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  • Indirect methods in nuclear astrophysics with relativistic radioactive beams
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2020-01-02
    Thomas Aumann; Carlos A. Bertulani

    Reactions with radioactive nuclear beams at relativistic energies have opened new doors to clarify the mechanisms of stellar evolution and cataclysmic events involving stars and during the big bang epoch. Numerous nuclear reactions of astrophysical interest cannot be assessed directly in laboratory experiments. Ironically, some of the information needed to describe such reactions, at extremely low energies (e.g., keVs), can only be studied on Earth by using relativistic collisions between heavy ions at GeV energies. In this contribution, we make a short review of experiments with relativistic radioactive beams and of the theoretical methods needed to understand the physics of stars, adding to the knowledge inferred from astronomical observations. We continue by introducing a more detailed description of how the use of relativistic radioactive beams can help to solve astrophysical puzzles and several successful experimental methods. State-of-the-art theories are discussed at some length with the purpose of helping us understand the experimental results reported. The review is not complete and we have focused most of it to traditional methods aiming at the determination of the equation of state of symmetric and asymmetric nuclear matter and the role of the symmetry energy. Whenever possible, under the limitations of our present understanding of experimental data and theory, we try to pinpoint the information still missing to further understand how stars evolve, explode, and how their internal structure might be. We try to convey the idea that in order to improve microscopic theories for many-body calculations, nuclear structure, nuclear reactions, and astrophysics, and in order to constrain and allow for convergence of our understanding of stars, we still need considerable improvements in terms of accuracy of experiments and the development of new and dedicated nuclear facilities to study relativistic reactions with radioactive beams.

    更新日期:2020-01-02
  • Photoproduction reactions and non-strange baryon spectroscopy
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-12-19
    David G. Ireland; Eugene Pasyuk; Igor Strakovsky

    We review the last two decades of using photon beams to measure the production of mesons, and in particular the information that can be obtained on the spectrum of light, non-strange baryons. This is a compendium of experimental results, which should be used as a complement to theoretical reviews of the subject. Lists of data sets are given, together with a comprehensive set of references. An indication of the impact of the data is presented with a summary of the results.

    更新日期:2019-12-19
  • PIC simulation methods for cosmic radiation and plasma instabilities
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-12-12
    M. Pohl; M. Hoshino; J. Niemiec

    Particle acceleration in collisionless plasma systems is a central question in astroplasma and astroparticle physics. The structure of the acceleration regions, electron-ion energy equilibration, preacceleration of particles at shocks to permit further energization by diffusive shock acceleration, require knowledge of the distribution function of particles besides the structure and dynamic of electromagnetic fields, and hence a kinetic description is desirable. Particle-in-cell simulations offer an appropriate, if computationally expensive method of essentially conducting numerical experiments that explore kinetic phenomena in collisionless plasma. We review recent results of PIC simulations of astrophysical plasma systems, particle acceleration, and the instabilities that shape them.

    更新日期:2019-12-13
  • Exclusive meson photo- and electro-production, a window on the structure of hadronic matter
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-11-14
    J.M. Laget

    At high energy, exclusive meson photo- and electro-production give access to the structure of hadronic matter. At low momentum transfers, the exchange of a few Regge trajectories leads to a comprehensive account of the cross-sections. Among these trajectories, which are related to the mass spectrum of families of mesons, the Pomeron plays an interesting role as it is related to glue-ball excitations. At high momentum transfers, the exchange of these collective excitations is expected to reduce to the exchange of their simplest (quark or gluon) components. However, contribution from unitarity rescattering cuts are relevant even at high energies. In the JLab energy range, the asymptotic regime, where the players in the game are current quarks and massless gluons has not been reached yet. One has to rely on more effective degrees of freedom adapted to the scale of the probe. A consistent picture, the “Partonic Non-Perturbative Regime”, is emerging. The properties of its various components (dressed propagators, effective coupling constants, quark wave functions, shape of the Regge trajectories, etc…..) provide us with various links to hadron properties. I will review the status of the field, will put in perspective the current achievements at JLab, SLAC and Hermes, and will assess future developments that are made possible by continuous electron beams at higher energies.

    更新日期:2019-11-14
  • Theory of deuteron stripping and pick-up reactions for nuclear structure studies
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-11-14
    N.K. Timofeyuk, R.C. Johnson

    Deuteron stripping and pick-up experiments - (d,p) and (p,d) - have been used for a long time to study the structure of nuclei. Today these experiments are often carried out in inverse kinematics in state-of-the-art radioactive beams facilities around the world, extending the boundaries of our knowledge of the nuclear chart. The nuclear structure information obtained from these experiments relies entirely on transfer reaction theory. We review the theory of (d,p) and (p,d) reactions starting from early formulations and ending with the most recent developments. In particular, we describe the recent progress made in the understanding of the three-body dynamics associated with the deuteron breakup degrees of freedom, including effects of nonlocality, and discuss the role of many-body degrees of freedom within the three-body context. We also review advances in structure model calculations of one-nucleon overlap functions - an important structure input to (d,p) and (p,d) reaction calculations. We emphasize the physics missing in widely-used standard approaches available to experimentalists and review ideas and efforts aimed at including this physics, formulating the crucial tasks for further development of deuteron stripping and pickup reaction theory.

    更新日期:2019-11-14
  • BCS-BEC crossover in cold atomic and in nuclear systems
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-11-14
    Y. Ohashi, H. Tajima, P. van Wyk

    We review the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose–Einstein condensation) crossover phenomenon discussed in an ultracold Fermi atomic gas and a neutron superfluid in the low-density crust regime of a neutron star. A purpose of this paper to show that these two very different atomic and nuclear systems can be closely related to each other from the viewpoint of this quantum many-body phenomenon. We explain how the BCS-BEC crossover is realized in the former atomic system by using the novel pairing mechanism called Feshbach resonance. We present a simple explanation for this crossover phenomenon to grasp the essence, as well as detailed microscopic theories that can cover the entire BCS-BEC crossover region. In the latter, we point out that the ordinary BCS theory already has the ability to describe the BCS-BEC crossover at T=0. At finite temperatures T>0, however, we need to go beyond this mean-field theory. Besides general aspects of the BCS-BEC crossover phenomenon, we also pick up special topics peculiar to each atomic gas and neutron fluid. The first one is the pseudogap phenomenon in the normal state of a Fermi atomic gas. The second one is the problem of non-zero effective range in an s-wave neutron superfluid.

    更新日期:2019-11-14
  • Status of light sterile neutrino searches
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-11-02
    Sebastian Böser, Christian Buck, Carlo Giunti, Julien Lesgourgues, Livia Ludhova, Susanne Mertens, Anne Schukraft, Michael Wurm

    A number of anomalous results in short-baseline oscillation may hint at the existence of one or more light sterile neutrino states in the eV mass range and have triggered a wave of new experimental efforts to search for a definite signature of oscillations between active and sterile neutrino states. The present paper aims to provide a comprehensive review on the status of light sterile neutrino searches in mid-2019: we discuss not only the basic experimental approaches and sensitivities of reactor, source, atmospheric, and accelerator neutrino oscillation experiments but also the complementary bounds arising from direct neutrino mass experiments and cosmological observations. Moreover, we review current results from global oscillation analyses that include the constraints set by running reactor and atmospheric neutrino experiments. They permit to set tighter bounds on the active-sterile oscillation parameters but as yet are not able to provide a definite conclusion on the existence of eV-scale sterile neutrinos.

    更新日期:2019-11-04
  • From quarks and gluons to baryon form factors.
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2012-04-01
    Gernot Eichmann

    I briefly summarize recent results for nucleon and [Formula: see text] electromagnetic, axial and transition form factors in the Dyson-Schwinger approach. The calculation of the current diagrams from the quark-gluon level enables a transparent discussion of common features such as: the implications of dynamical chiral symmetry breaking and quark orbital angular momentum, the timelike structure of the form factors, and their interpretation in terms of missing pion-cloud effects.

    更新日期:2019-11-01
  • Cluster structure of light nuclei
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-10-23
    R. Bijker, F. Iachello

    We review recent studies of the cluster structure of light nuclei within the framework of the algebraic cluster model (ACM) for nuclei composed of k α-particles and within the framework of the cluster shell model (CSM) for nuclei composed of k α-particles plus x additional nucleons. The calculations, based on symmetry considerations and thus for the most part given in analytic form, are compared with experiments in light cluster nuclei. The comparison shows evidence for Z2, D3h and Td symmetry in the even-even nuclei 8Be (k=2), 12C (k=3) and 16O (k=4), respectively, and for the associated double groups Z2′ and D3h′ in the odd nuclei 9Be, 9B (k=2, x=1) and 13C (k=3, x=1), respectively.

    更新日期:2019-10-24
  • Coupled-channel approach in hadron–hadron scattering
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-09-14
    J.A. Oller

    Coupled-channel dynamics for scattering and production processes in partial-wave amplitudes is discussed from a perspective that emphasizes unitarity and analyticity. We elaborate on several methods that have driven to important results in hadron physics, either by themselves or in conjunction with effective field theory. We also develop the use of the Lippmann–Schwinger equation in near-threshold scattering and compare it with other methods. The final(initial)-state interactions are discussed in detail for the elastic and coupled-channel case. Emphasis has been put in the derivation and discussion of the methods presented, with some applications examined as important examples of their usage.

    更新日期:2019-09-16
  • Why is there more matter than antimatter? Calculational methods for leptogenesis and electroweak baryogenesis
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-09-10
    Björn Garbrecht

    We review the production of the matter-antimatter asymmetry in the early Universe, that is baryogenesis, in out-of-equlibrium conditions induced by decays of heavy particles or by the presence of phase boundaries. The most prominent examples are given by leptogenesis and electroweak baryogenesis, respectively. For both cases, we derive the equations that govern the production of the asymmetries. We first use intuitive arguments based on classical fluid equations in combination with quantum-field-theoretical effects of CP-violation. As for a more thorough approach that is well-suited for systematic improvements, we obtain the real-time evolution of the system of interest using the closed time-path method. We thus provide a simple and practicable scheme to set up phenomenological fluid equations based on first principles of quantum field theory. Necessary for baryogenesis are both, CP even as well as odd phases in the amplitudes. A possibility of generating the even phases is the coherent superposition of quantum states, i.e. mixing. These coherence effects are essential in resonant leptogenesis as well as in some scenarios of electroweak baryogenesis. Recent theoretical progress on asymmetries from out-of-equlibrium decays may therefore also be applicable to baryogenesis at phase boundaries.

    更新日期:2019-09-11
  • Heavy ion charge exchange reactions as probes for nuclear β-decay
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-08-12
    Horst Lenske, Francesco Cappuzzello, Manuela Cavallaro, Maria Colonna

    The status and prospects of heavy ion charge exchange reactions are reviewed. Their important role for nuclear reaction, nuclear structure, and beta-decay investigations is emphasized. Dealing with peripheral reactions, direct reaction theory gives at hand the proper methods for single (SCE) and double charge exchange (DCE) ion-ion scattering. The microscopic descriptions of charge exchange ion-ion residual interactions and the reaction mechanism are obtained by distorted wave theory. Ion-Ion optical potentials and reaction form factors are determined in a folding approach by using NN T-matrices and microscopic ground state and transition densities, respectively. The theory of one-step direct and two-step transfer reaction mechanisms for SCE reactions is discussed and illustrated in applications to data. Specific SCE reactions are discussed in detail, emphasizing the versatility of projectile–target combinations and incident energies. SCE reactions induced by 12C and 7Li beams are presented as representative examples. Heavy ion DCE reactions are shown to proceed in principle either by sequential pair transfer or two kinds of collisional NN processes. Double single charge exchange (DSCE) is given by two consecutive SCE processes, resembling in structure 2ν2β decay. A competing process is a two-nucleon mechanism, relying on short range NN correlations and leading to the correlated exchange of two charged mesons between projectile and target. These Majorana DCE (MDCE) events are of a similar diagrammatic structure as 0ν2β decay. The similarities of the DSCE and MDCE processes to pionic DCE reactions are elucidated. An overview on recent experimental research activities on heavy ion DCE research is given. Charge exchange strength distributions above the isovector spin-multipole resonance region and the excitation of nucleon resonances in high energy heavy ion SCE reactions are discussed in connection with the quenching issue.

    更新日期:2019-08-12
  • Hadron matter in neutron stars in view of gravitational wave observations
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-08-07
    Felipe J. Llanes-Estrada, Eva Lope-Oter

    In this review we highlight a few physical properties of neutron stars and their theoretical treatment inasmuch as they can be useful for nuclear and particle physicists concerned with matter at finite density (and newly, temperature). Conversely, we lay out some of the hadron physics necessary to test General Relativity with binary mergers including at least one neutron star, in view of the event GW170817: neutron stars and their mergers reach the highest matter densities known, offering access to the matter side of Einstein’s equations. In addition to minimum introductory material for those interested in starting research in the field of neutron stars, we dedicate quite some effort to a discussion of the Equation of State of hadron matter in view of gravitational wave developments; we address phase transitions and how the new data may help; we show why transport is expected to be dominated by turbulence instead of diffusion through most if not all of the star, in view of the transport coefficients that have been calculated from microscopic hadron physics; and we relate many of the interesting physics topics in neutron stars to the radius and tidal deformability.

    更新日期:2019-08-07
  • Gravitational waves from neutron star mergers and their relation to the nuclear equation of state
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-08-02
    L. Baiotti

    In this article, I introduce ideas and techniques to extract information about the equation of state of matter at very high densities from gravitational waves emitted before, during and after the merger of binary neutron stars. I also review current work and results on the actual use of the first gravitational-wave observation of a neutron-star merger to set constraints on properties of such equation of state. In passing, I also touch on the possibility that what we observe in gravitational waves are not neutron stars, but something more exotic. In order to make this article more accessible, I also review the dynamics and gravitational-wave emission of neutron-star mergers in general, with focus on numerical simulations and on which representations of the equation of state are used for studies on binary systems.

    更新日期:2019-08-03
  • Experimental aspects of geoneutrino detection: Status and perspectives
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-08-01
    O. Smirnov

    Neutrino geophysics, the study of the Earth’s interior by measuring the fluxes of geologically produced neutrino at its surface, is a new interdisciplinary field of science, rapidly developing as a synergy between geology, geophysics and particle physics. Geoneutrinos, antineutrinos from long-lived natural isotopes responsible for the radiogenic heat flux, provide valuable information for the chemical composition models of the Earth. The calculations of the expected geoneutrino signal are discussed, together with experimental aspects of geoneutrino detection, including the description of possible backgrounds and methods for their suppression. At present, only two detectors, Borexino and KamLAND, have reached sensitivity to the geoneutrino. The experiments accumulated a set of ∼190 geoneutrino events and continue the data acquisition. The detailed description of the experiments, their results on geoneutrino detection, and impact on geophysics are presented. The start of operation of other detectors sensitive to geoneutrinos is planned for the near future: the SNO+ detector is being filled with liquid scintillator, and the biggest ever 20 kt JUNO detector is under construction. A review of the physics potential of these experiments with respect to the geoneutrino studies, along with other proposals, is presented. New ideas and methods for geoneutrino detection are reviewed.

    更新日期:2019-08-02
  • Towards an ab initio covariant density functional theory for nuclear structure
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-08-01
    Shihang Shen, Haozhao Liang, Wen Hui Long, Jie Meng, Peter Ring

    Nuclear structure models built from phenomenological mean fields, the effective nucleon–nucleon interactions (or Lagrangians), and the realistic bare nucleon–nucleon interactions are reviewed. The success of covariant density functional theory (CDFT) to describe nuclear properties and its influence on Brueckner theory within the relativistic framework are focused upon. The challenges and ambiguities of predictions for unstable nuclei without data or for high-density nuclear matter, arising from relativistic density functionals, are discussed. The basic ideas in building an ab initio relativistic density functional for nuclear structure from ab initio calculations with realistic nucleon–nucleon interactions for both nuclear matter and finite nuclei are presented. The current status of fully self-consistent relativistic Brueckner-Hartree–Fock (RBHF) calculations for finite nuclei or neutron drops (ideal systems composed of a finite number of neutrons and confined within an external field) is reviewed. The guidance and perspectives towards an ab initio covariant density functional theory for nuclear structure derived from the RBHF results are provided.

    更新日期:2019-08-02
  • Spallation, cosmic rays, meteorites, and planetology
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-07-29
    J.-C. David, I. Leya

    In this review article we present some of the major applications for cosmogenic nuclide studies; extraterrestrial applications on meteorites, lunar surface samples but also on interstellar grains and terrestrial applications ranging from ages for exposure and burial over erosion and denudation rates to uplift and soil dynamics. For all the applications a good knowledge of the cosmogenic nuclide production rates are indispensable. Since it is neither possible nor feasible measuring production rates for all possible set-ups and geometries they are usually calculated using the particle spectra for primary and secondary particles and the cross sections for the relevant nuclear reactions. Considering the reacting particles we also discuss in some detail the basic properties of solar and galactic cosmic rays, especially we focus on the temporal variability. With a good understanding of the projectile types, a very relevant step is to understand and model the induced nuclear reactions. In doing so, we will briefly discuss the basic properties of spallation reactions and we especially focus on the recent very impressive improvements. We finish with a short outlook of the next possible steps for further improvements.

    更新日期:2019-07-29
  • Cosmic ray models
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-07-24
    M. Kachelrieß, D.V. Semikoz

    We review progress in high-energy cosmic ray physics focusing on recent experimental results and models developed for their interpretation. Emphasis is put on the propagation of charged cosmic rays, covering the whole range from ∼(20–50) GV, i.e. the rigidity when solar modulations can be neglected, up to the highest energies observed. We discuss models aiming to explain the anomalies in Galactic cosmic rays, the knee, and the transition from Galactic to extragalactic cosmic rays.

    更新日期:2019-07-25
  • Relativistic hydrodynamics for spin-polarized fluids
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-07-24
    Wojciech Florkowski, Radoslaw Ryblewski, Avdhesh Kumar

    Recent progress in the formulation of relativistic hydrodynamics for particles with spin one-half is reviewed. We start with general arguments advising introduction of a tensor spin chemical potential that plays a role of the Lagrange multiplier coupled to the spin angular momentum. Then, we turn to a discussion of spin-dependent distribution functions that have been recently proposed to construct a hydrodynamic framework including spin and serve as a tool in phenomenological studies of hadron polarization. Distribution functions of this type are subsequently used to construct the equilibrium Wigner functions that are employed in the semi-classical kinetic equation. The semi-classical expansion elucidates several aspects of the hydrodynamic approach, in particular, shows the ways in which different possible versions of hydrodynamics with spin can be connected by pseudo-gauge transformations. These results point out at using the de Groot - van Leeuwen - van Weert versions of the energy–momentum and spin tensors as the most natural and complete physical variables. Finally, a totally new method is proposed to design hydrodynamics with spin, which is based on the classical treatment of spin degrees of freedom. Interestingly, for small values of the spin chemical potential the new scheme brings the results that coincide with those obtained before. The classical approach also helps us to resolve problems connected with the normalization of the spin polarization three-vector. In addition, it clarifies the role of the Pauli-Lubański vector and the entropy current conservation. We close our review with several general comments presenting possible future developments of the discussed frameworks.

    更新日期:2019-07-24
  • Current status of r-process nucleosynthesis
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-03-06
    T. Kajino, W. Aoki, A.B. Balantekin, R. Diehl, M.A. Famiano, G.J. Mathews

    The rapid neutron capture process (r process) is believed to be responsible for about half of the production of the elements heavier than iron and contributes to abundances of some lighter nuclides as well. A universal pattern of r-process element abundances is observed in some metal-poor stars of the Galactic halo. This suggests that a well-regulated combination of astrophysical conditions and nuclear physics conspires to produce such a universal abundance pattern. The search for the astrophysical site for r-process nucleosynthesis has stimulated interdisciplinary research for more than six decades. There is currently much enthusiasm surrounding evidence for r-process nucleosynthesis in binary neutron star mergers in the multi-wavelength follow-up observations of kilonova/gravitational-wave GRB170807A/GW170817. Nevertheless, there remain questions as to the contribution over the history of the Galaxy to the current solar-system r-process abundances from other sites such as neutrino-driven winds or magnetohydrodynamical ejection of material from core-collapse supernovae. In this review we highlight some current issues surrounding the nuclear physics input, astronomical observations, galactic chemical evolution, and theoretical simulations of r-process astrophysical environments with the goal of outlining a path toward resolving the remaining mysteries of the r process.

    更新日期:2019-07-05
  • Interplay of neutron-proton equilibration and nuclear dynamics
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-06-13
    Alan B. McIntosh, Sherry J. Yennello

    Neutron-proton equilibration in heavy-ion collisions proceeds atop a landscape of deformed topography and large density changes. The rapidly-varying landscape is created by the collision dynamics. The collision dynamics influences the neutron-proton equilibration, but just as importantly the different migration of the protons and neutrons influences the dynamics. To fully appreciate either the reaction dynamics or the neutron-proton equilibration, one must understand both. This review explores decades of work on both topics, and highlights the connections to the nuclear equation of state in nuclear experiment, theoretical prediction, and astrophysical observation.

    更新日期:2019-06-13
  • Measurements of multi vector boson production processes at the LHC
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-06-10
    A. Oh

    Standard model processes with multi-boson final states provide a unique testing ground for the electroweak sector of the standard model and allow to set limits on generic model extensions to constrain the scale of new particles and interactions. The experiments at the Large Hadron Collider at CERN followed a comprehensive program to determine the properties of many accessible multi-boson processes at different collision energies in run-1 and run-2. This review discusses the current status of multi-boson measurements at the LHC.

    更新日期:2019-06-10
  • The QCD renormalization group equation and the elimination of fixed-order scheme-and-scale ambiguities using the principle of maximum conformality
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-05-27
    Xing-Gang Wu, Jian-Ming Shen, Bo-Lun Du, Xu-Dong Huang, Sheng-Quan Wang, Stanley J. Brodsky

    The conventional scale setting approach to fixed-order perturbative QCD (pQCD) predictions is based on a guessed renormalization scale, usually taking as the one to eliminate the large log-terms of the pQCD series, together with an arbitrary range to estimate its uncertainty. This ad hoc assignment of the renormalization scale causes the coefficients of the QCD running coupling at each perturbative order to be strongly dependent on the choices of both the renormalization scale and the renormalization scheme, which leads to conventional renormalization scheme-and-scale ambiguities. However, such ambiguities are not necessary, since as a basic requirement of renormalization group invariance (RGI), any physical observable must be independent of the choices of both the renormalization scheme and the renormalization scale. In fact, if one uses the Principle of Maximum Conformality (PMC) to fix the renormalization scale, the coefficients of the pQCD series match the series of conformal theory, and they are thus scheme independent. The PMC predictions also eliminate the divergent renormalon contributions, leading to a better convergence property. It has been found that the elimination of the scale and scheme ambiguities at all orders relies heavily on how precisely we know the analytic form of the QCD running coupling αs. In this review, we summarize the known properties of the QCD running coupling and its recent progresses, especially for its behavior within the asymptotic region. Conventional schemes for defining the QCD running coupling suffer from a complex and scheme-dependent renormalization group equation (RGE), or the β-function, which is usually solved perturbatively at high orders due to the entanglement of the scheme-running and scale-running behaviors. These complications lead to residual scheme dependence even after applying the PMC, which however can be avoided by using a C-scheme coupling αˆs, whose scheme-and-scale running behaviors are governed by the same scheme-independent RGE. As a result, an analytic solution for the running coupling can be achieved at any fixed order. Using the C-scheme coupling, a demonstration that the PMC prediction is scheme-independent to all-orders for any renormalization schemes can be achieved. Given a measurement which sets the magnitude of the QCD running coupling at a specific scale such as MZ, the resulting pQCD predictions, after applying the single-scale PMC, become completely independent of the choice of the renormalization scheme and the initial renormalization scale at any fixed-order, thus satisfying all of the conditions of RGI. An improved pQCD convergence provides an opportunity of using the resummation procedures such as the Padé approximation (PA) approach to predict higher-order terms and thus to increase the precision, reliability and predictive power of pQCD theory. In this review, we also summarize the current progress on the PMC and some of its typical applications, showing to what degree the conventional renormalization scheme-and-scale ambiguities can be eliminated after applying the PMC. We also compare the PA approach for the conventional scale-dependent pQCD series and the PMC scale-independent conformal series. We observe that by using the conformal series, the PA approach can provide a more reliable estimate of the magnitude of the uncalculated terms. And if the conformal series for an observable has been calculated up to nth-order level, then the [N∕M]=[0∕n−1]-type PA series provides an important estimate for the higher-order terms.

    更新日期:2019-05-27
  • Experimental searches for the chiral magnetic effect in heavy-ion collisions
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-05-22
    Jie Zhao, Fuqiang Wang

    The chiral magnetic effect (CME) in quantum chromodynamics (QCD) refers to a charge separation (an electric current) of chirality imbalanced quarks generated along an external strong magnetic field. The chirality imbalance results from interactions of quarks, under the approximate chiral symmetry restoration, with metastable local domains of gluon fields of non-zero topological charges out of QCD vacuum fluctuations. Those local domains violate the P and CP invariance, potentially offering a solution to the strong CP problem in explaining the magnitude of the matter–antimatter asymmetry in today’s universe. Relativistic heavy-ion collisions, with the likely creation of the high energy density quark–gluon plasma and restoration of the approximate chiral symmetry, and the possibly long-lived strong magnetic field, provide a unique opportunity to detect the CME. Early measurements of the CME-induced charge separation in heavy-ion collisions are dominated by physics backgrounds. Major efforts have been devoted to eliminate or reduce those backgrounds. We review those efforts, with a somewhat historical perspective, and focus on the recent innovative experimental undertakings in the search for the CME in heavy-ion collisions.

    更新日期:2019-05-23
  • Majorana fermions in magnetic chains
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-05-22
    Rémy Pawlak, Silas Hoffman, Jelena Klinovaja, Daniel Loss, Ernst Meyer

    Majorana fermions have recently garnered a great attention outside the field of particle physics, in condensed matter physics. In contrast to their particle physics counterparts, Majorana fermions are zero energy, chargeless, spinless, composite quasiparticles, residing at the boundaries of so-called topological superconductors. Furthermore, in opposition to any particles in the standard model, Majorana fermions in solid-state systems obey non-Abelian exchange statistics that make them attractive candidates for decoherence-free implementations of quantum computers. In this review, we report on the recent advances to realize synthetic topological superconductors supporting Majorana fermions with an emphasis on chains of magnetic impurities on the surface of superconductors. After outlining the theoretical underpinning responsible for the formation of Majorana fermions, we report on the subsequent experimental efforts to build topological superconductors and the resulting evidence in favor of Majorana fermions, focusing on scanning tunneling microscopy and the hunt for zero-bias peaks in the measured current. We conclude by summarizing the open questions in the field and propose possible experimental measurements to answer them.

    更新日期:2019-05-23
  • The hadronic light-by-light contribution to the muon’s anomalous magnetic moment
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-05-14
    Igor Danilkin, Christoph Florian Redmer, Marc Vanderhaeghen

    In view of the current 3 - 4 σ deviation between theoretical and experimental values for the muon’s anomalous magnetic moment, we review the ongoing efforts in constraining the hadronic light-by-light contribution to aμ by using dispersive techniques combined with a dedicated experimental program to obtain the required hadronic input.

    更新日期:2019-05-16
  • Pentaquark and Tetraquark States
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-04-09
    Yan-Rui Liu, Hua-Xing Chen, Wei Chen, Xiang Liu, Shi-Lin Zhu

    The past seventeen years have witnessed tremendous progress on the experimental and theoretical explorations of the multiquark states. The hidden-charm and hidden-bottom multiquark systems were reviewed extensively in Ref. [1]. In this article, we shall update the experimental and theoretical efforts on the hidden heavy flavor multiquark systems in the past three years. Especially the LHCb collaboration not only confirmed the existence of the hidden-charm pentaquarks but also provided strong evidence of the molecular picture. Besides the well-known XYZ and Pc states, we shall discuss more interesting tetraquark and pentaquark systems either with one, two, three or even four heavy quarks. Some very intriguing states include the fully heavy exotic tetraquark states QQQ̄Q̄ and doubly heavy tetraquark states QQq̄q̄, where Q is a heavy quark. The QQQ̄Q̄ states may be produced at LHC while the QQq̄q̄ system may be searched for at BelleII and LHCb. Moreover, we shall pay special attention to various theoretical schemes such as the chromomagnetic interaction (CMI), constituent quark model, meson exchange model, heavy quark and heavy diquark symmetry, QCD sum rules, Faddeev equation for the three body systems, Skyrme model and the chiral quark-soliton model, and the lattice QCD simulations. We shall emphasize the model-independent predictions of various models which are truly/closely related to Quantum Chromodynamics (QCD). For example, the chromomagnetic interaction arises from the gluon exchange which is fundamental and universal in QCD and responsible for the mixing and mass splitting of the conventional mesons and baryons within the same multiplet. The same CMI mechanism shall also be responsible for the mixing of the different color configurations and mass splittings within the multiplets in the multiquark sector. There have also accumulated many lattice QCD simulations through multiple channel scattering on the lattice in recent years, which provide deep insights into the underlying structure/dynamics of the XYZ states. In terms of the recent Pc states, the lattice simulations of the charmed baryon and anti-charmed meson scattering are badly needed. We shall also discuss some important states which may be searched for at BESIII, BelleII and LHCb in the coming years.

    更新日期:2019-05-16
  • Novel techniques for constraining neutron-capture rates relevant for r-process heavy-element nucleosynthesis
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-04-05
    A.C. Larsen, A. Spyrou, S.N. Liddick, M. Guttormsen

    The rapid-neutron capture process (r process) is identified as the producer of about 50% of elements heavier than iron. This process requires an astrophysical environment with an extremely high neutron flux over a short amount of time (∼ seconds), creating very neutron-rich nuclei that are subsequently transformed to stable nuclei via β− decay. In 2017, one site for the r process was confirmed: the advanced LIGO and advanced Virgo detectors observed two neutron stars merging, and immediate follow-up measurements of the electromagnetic transients demonstrated an “afterglow” over a broad range of frequencies fully consistent with the expected signal of an r process taking place. Although neutron-star mergers are now known to be r-process element factories, contributions from other sites are still possible, and a comprehensive understanding and description of the r process is still lacking. One key ingredient to large-scale r-process reaction networks is radiative neutron-capture (n,γ) rates, for which there exist virtually no data for extremely neutron-rich nuclei involved in the r process. Due to the current status of nuclear-reaction theory and our poor understanding of basic nuclear properties such as level densities and average γ-decay strengths, theoretically estimated (n,γ) rates may vary by orders of magnitude and represent a major source of uncertainty in any nuclear-reaction network calculation of r-process abundances. In this review, we discuss new approaches to provide information on neutron-capture cross sections and reaction rates relevant to the r process. In particular, we focus on indirect, experimental techniques to measure radiative neutron-capture rates. While direct measurements are not available at present, but could possibly be realized in the future, the indirect approaches present a first step towards constraining neutron-capture rates of importance to the r process.

    更新日期:2019-05-16
  • Extreme matter in electromagnetic fields and rotation
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-04-04
    Kenji Fukushima

    We look over recent developments on our understanding about relativistic matter under external electromagnetic fields and mechanical rotation. I review various calculational approaches for concrete physics problems, putting my special emphasis on generality of the method and the consequence, rather than going into phenomenological applications in a specific field of physics. The topics covered in this article include static problems with magnetic fields, dynamical problems with electromagnetic fields, and phenomena induced by rotation.

    更新日期:2019-05-16
  • QCD at finite temperature and chemical potential from Dyson–Schwinger equations
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-01-31
    Christian S. Fischer

    We review results for the phase diagram of QCD, the properties of quarks and gluons and the resulting properties of strongly interacting matter at finite temperature and chemical potential. The interplay of two different but related transitions in QCD, chiral symmetry restoration and deconfinement, leads to a rich phenomenology when external parameters such as quark masses, volume, temperature and chemical potential are varied. We discuss the progress in this field from a theoretical perspective, focusing on non-perturbative QCD as encoded in the functional approach via Dyson–Schwinger and Bethe–Salpeter equations. We aim at a pedagogical overview on the physics associated with the structure of this framework and explain connections to other approaches, in particular with the functional renormalisation group and lattice QCD. We discuss various aspects associated with the variation of the quark masses, assess recent results for the QCD phase diagram including the location of a putative critical end-point for Nf=2+1 and Nf=2+1+1 , discuss results for quark spectral functions and summarise aspects of QCD thermodynamics and fluctuations.

    更新日期:2019-03-12
  • Open charm hadron spectroscopy at B-factories
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-01-16
    Y. Kato, T. Iijima

    Open charm hadrons are excellent probes to study the dynamics of quarks and gluons inside hadrons. Because the mass of a charm quark is heavier than ΛQCD , so called heavy quark symmetry emerges in the hadron containing a charm quark and plays a central role in the classification and constraining the interactions. Belle and BaBar, which are B-factory experiments, have made significant advances in the field of open charm hadron spectroscopy in these 15 years. In this article, experimental advances on both open charm mesons and baryons by B-factory experiments are reviewed. Finally, the prospect of the open charm hadrons with the next generation B-factory experiment, Belle II is described.

    更新日期:2019-03-12
  • Liquid–Gas phase transition in nuclei
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-12-13
    B. Borderie, J.D. Frankland

    This review article takes stock of the progress made in understanding the phase transition in hot nuclei and highlights the coherence of observed signatures.

    更新日期:2019-03-12
  • Dynamics of clusters and fragments in heavy-ion collisions
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-11-13
    Akira Ono

    A review is given on the studies of formation of light clusters and heavier fragments in heavy-ion collisions at incident energies from several tens of MeV/nucleon to several hundred MeV/nucleon, focusing on dynamical aspects and on microscopic theoretical descriptions. Existing experimental data already clarify basic characteristics of expanding and fragmenting systems typically in central collisions, where cluster correlations cannot be ignored. Cluster correlations appear almost everywhere in excited low-density nuclear many-body systems and nuclear matter in statistical equilibrium where the properties of a cluster may be influenced by the medium. On the other hand, transport models to solve the time evolution have been developed based on the single-nucleon distribution function. Different types of transport models are reviewed putting emphasis both on theoretical features and practical performances in the description of fragmentation. A key concept to distinguish different models is how to consistently handle single-nucleon motions in the mean field, fluctuation or branching induced by two-nucleon collisions, and localization of nucleons to form fragments and clusters. Some transport codes have been extended to treat light clusters explicitly. Results indicate that cluster correlations can have strong impacts on global collision dynamics and correlations between light clusters should also be taken into account.

    更新日期:2019-03-12
  • Nuclear level density, thermalization, chaos, and collectivity
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-12-10
    Vladimir Zelevinsky, Mihai Horoi

    The knowledge of the level density is necessary for understanding nuclear reactions involving excited nuclear states. In particular, it is an important element in description of astrophysical processes and in technological applications. This review article explains main ideas of physics forming the level density in complex nuclei that grows very fast due to combinatorial complexity of total excitation energy shared by many constituents. This can be translated into a language of statistical physics by the Darwin–Fowler method. We briefly go through the historical development from the nuclear Fermi-gas model to the self-consistent mean field including the pairing effects. At the next step we introduce the ideas of thermalization in a closed mesoscopic system and quantum chaos with very complicated eigenfunctions. This is supported by the experience of the shell model in a limited orbital space that either provides an exact solution or uses the Monte Carlo approach. The statistical method of moments allows one to avoid the exact diagonalization keeping intact the quality of the results. We discuss the popular “constant temperature model” that describes well available data and the shell-model results; it is shown that its success cannot be explained by the phase transition from superfluid to a normal phase. The interpretation is suggested, supported by the numerical studies, in terms of dynamical chaotization including the collective enhancement of the level density. The role of incoherent collision-like interactions is stressed as a necessary element of the thermalization process.

    更新日期:2019-03-12
  • Recent developments in radioactive charged-particle emissions and related phenomena
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-12-06
    Chong Qi, Roberto Liotta, Ramon Wyss

    The advent and intensive use of new detector technologies as well as radioactive ion beam facilities have opened up possibilities to investigate alpha, proton and cluster decays of highly unstable nuclei. This article provides a review of the current status of our understanding of clustering and the corresponding radioactive particle decay process in atomic nuclei. We put alpha decay in the context of charged-particle emissions which also include one- and two-proton emissions as well as heavy cluster decay. The experimental as well as the theoretical advances achieved recently in these fields are presented. Emphasis is given to the recent discoveries of charged-particle decays from proton-rich nuclei around the proton drip line. Those decay measurements have shown to provide an important probe for studying the structure of the nuclei involved. Developments on the theoretical side in nuclear many-body theories and supercomputing facilities have also made substantial progress, enabling one to study the nuclear clusterization and decays within a microscopic and consistent framework. We report on properties induced by the nuclear interaction acting in the nuclear medium, like the pairing interaction, which have been uncovered by studying the microscopic structure of clusters. The competition between cluster formations as compared to the corresponding alpha-particle formation are included. In the review we also describe the search for super-heavy nuclei connected by chains of alpha and other radioactive particle decays.

    更新日期:2019-03-12
  • Recent developments for the optical model of nuclei
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-11-14
    W.H. Dickhoff, R.J. Charity

    A brief overview of various approaches to the optical-model description of nuclei is presented. A survey of some of the formal aspects is given which links the Feshbach formulation for either the hole or particle Green’s function to the time-ordered quantity of many-body theory. The link between the reducible self-energy and the elastic nucleon–nucleus scattering amplitude is also presented using the development of Villars. A brief summary of the essential elements of the multiple-scattering approach is also included. Several ingredients contained in the time-ordered Green’s function are summarized for the formal framework of the dispersive optical model (DOM). Empirical approaches to the optical potential are reviewed with emphasis on the latest global parametrizations for nucleons and composites. Various calculations that start from an underlying realistic nucleon–nucleon interaction are discussed with emphasis on more recent work. The efficacy of the DOM is illustrated in relating nuclear structure and nuclear reaction information. Its use as an intermediate between experimental data and theoretical calculations is advocated. Applications of the use of optical models are pointed out in the context of the description of nuclear reactions other than elastic nucleon–nucleus scattering.

    更新日期:2019-03-12
  • Transport approaches for the description of intermediate-energy heavy-ion collisions
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-03-06
    Jun Xu

    The transport approach is a useful tool to study dynamics of non-equilibrium systems. For heavy-ion collisions at intermediate energies, where both the smooth nucleon potential and the hard-core nucleon–nucleon collision are important, the dynamics are properly described by two families of transport models, i.e., the Boltzmann-Uehling-Uhlenbeck approach and the quantum molecular dynamics approach. These transport models have been extensively used to extract valuable information of the nuclear equation of state, the nuclear symmetry energy, and microscopic nuclear interactions from intermediate-energy heavy-ion collision experiments. On the other hand, there do exist deviations on the predications and conclusions from different transport models. Efforts on the transport code evaluation project are devoted in order to understand the model dependence of transport simulations and well control the main ingredients, such as the initialization, the mean-field potential, the nucleon–nucleon collision, etc. An new era of accurately extracting nuclear interactions from transport model studies is foreseen.

    更新日期:2019-03-12
  • A design for an electromagnetic filter for precision energy measurements at the tritium endpoint
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-02-28
    M.G. Betti, M. Biasotti, A. Boscá, F. Calle, J. Carabe-Lopez, G. Cavoto, C. Chang, W. Chung, A.G. Cocco, A.P. Colijn, J. Conrad, N. D’Ambrosio, P.F. de Salas, M. Faverzani, A. Ferella, E. Ferri, P. Garcia-Abia, G. Garcia Gomez-Tejedor, K.M. Zurek

    We present a detailed description of the electromagnetic filter for the PTOLEMY project to directly detect the Cosmic Neutrino Background (CNB). Starting with an initial estimate for the orbital magnetic moment, the higher-order drift process of E×B is configured to balance the gradient-B drift motion of the electron in such a way as to guide the trajectory into the standing voltage potential along the mid-plane of the filter. As a function of drift distance along the length of the filter, the filter zooms in with exponentially increasing precision on the transverse velocity component of the electron kinetic energy. This yields a linear dimension for the total filter length that is exceptionally compact compared to previous techniques for electromagnetic filtering. The parallel velocity component of the electron kinetic energy oscillates in an electrostatic harmonic trap as the electron drifts along the length of the filter. An analysis of the phase-space volume conservation validates the expected behavior of the filter from the adiabatic invariance of the orbital magnetic moment and energy conservation following Liouville’s theorem for Hamiltonian systems.

    更新日期:2019-03-12
  • Electroweak precision tests of the Standard Model after the discovery of the Higgs Boson
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-02-28
    Jens Erler, Matthias Schott

    The global fit of the Standard Model predictions to electroweak precision data, which has been routinely performed in the past decades by several groups, led to the prediction of the top quark and the Higgs boson masses before their respective discoveries. With the measurement of the Higgs boson mass at the Large Hadron Collider (LHC) in 2012 by the ATLAS and CMS collaborations, the last free parameter of the Standard Model of particle physics has been fixed, and the global electroweak fit can be used to test the full internal consistency of the electroweak sector of the Standard Model and constrain models beyond. In this article, we review the current state-of-the-art theoretical calculations, as well as the precision measurements performed at the LHC, and interpret them within the context of the global electroweak fit. Special focus is drawn in the impact of the Higgs boson mass on the fit.

    更新日期:2019-03-12
  • Collider searches for long-lived particles beyond the Standard Model
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-02-27
    Lawrence Lee, Christian Ohm, Abner Soffer, Tien-Tien Yu

    Despite decades of attempts to reveal its flaws, the Standard Model of particle physics (SM) has withstood all experimental tests and its predictions are in excellent agreement with data. Since the theory was formulated, experiments have provided little guidance regarding the explanations of phenomena not described by the SM, such as the baryon asymmetry of the universe and dark matter. Nor do we have satisfying understanding of the aesthetic and theoretical problems of the model, despite years of searching for new processes and particles proposed to solve them. Such particles can evade being discovered by the comprehensive search programs at collider experiments if the analysis selections and the algorithms used to reconstruct the detector data are not matched to the characteristics of the particles, e.g. if they have long enough lifetimes. As interest in searches for such long-lived particles at colliders grows rapidly, we present a review of this area of research in this article. The broad range of theoretical motivations for particles with long lifetimes and the experimental strategies and methods employed to search for them are described. Results from decades of searches are reviewed, as are opportunities for the next generation of searches both at existing and proposed future experiments.

    更新日期:2019-03-12
  • Isoscalar and isovector dipole excitations: Nuclear properties from low-lying states and from the isovector giant dipole resonance
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-02-27
    A. Bracco, E.G. Lanza, A. Tamii

    This review paper concerns the research devoted to the study of the properties of dipole excitations in nuclei. The main focus is on questions related to isospin effects in these types of excitations. Particular attention is given to the experimental and theoretical efforts made to understand the nature and the specific structure of the low-lying dipole states known as the Pygmy Dipole Resonance (PDR). The main experimental methods employed in the study of the PDR are reviewed as well as the most interesting theoretical aspects. The main features of the experiments and of theoretical models are reported with special emphasis on the reaction cross sections populating the dipole states. Results are organised for nuclei according to different mass regions. The knowledge of the isovector dipole response as well as its low energy part is important in order to deduce the nuclear polarisability as accurate as possible. This issue is discussed in this paper together with the connection with the neutron skin and the nuclear equation of state. The important role played by the dipole response to deduce other physical quantities of general interest is discussed in the last two chapters. One concerns the level density and the other the isospin mixing in nuclei at finite temperature and its relation with beta decay.

    更新日期:2019-03-12
  • Recent progress in QCD condensate evaluations and sum rules
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-02-27
    P. Gubler, D. Satow

    We review the recent status of the QCD sum rule approach to study the properties of hadrons in vacuum and in hot or dense matter. Special focus is laid on the progress made in the evaluation of the QCD condensates, which are the input of all QCD sum rule calculations, and for which much new information has become available through high precision lattice QCD calculations, chiral perturbation theory and experimental measurements. Furthermore, we critically examine common analysis methods for QCD sum rules and contrast them with potential alternative strategies. The status of QCD sum rule studies investigating the modification of hadrons at finite density as well as recent derivations of exact sum rules applicable to finite temperature spectral functions, are also reviewed.

    更新日期:2019-03-12
  • Effective density functionals beyond mean field
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-02-18
    Marcella Grasso

    I present a review on non relativistic effective energy–density functionals (EDFs). An introductory part is dedicated to traditional phenomenological functionals employed for mean-field-type applications and to several extensions and implementations that have been suggested over the years to generalize such functionals, up to the most recent ideas. The heart of this review is then focused on density functionals designed for beyond-mean-field models. Examples of these studies are discussed. Starting from these investigations, some illustrations of ab-initio-based or ab-initio-inspired functionals are provided. Constructing functionals by building bridges with ab-initio models represents an extremely challenging and timely objective. This will eventually reduce/eliminate the empirical character of EDFs and link them with the underlying theory of QCD. Conclusions are presented in the last part of the review.

    更新日期:2019-03-12
  • Brout–Englert–Higgs physics: From foundations to phenomenology
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2019-02-16
    Axel Maas

    Brout–Englert–Higgs physics is one of the most central and successful parts of the standard model. It is also part of a multitude of beyond-the-standard-model scenarios. The aim of this review is to describe the field-theoretical foundations of Brout–Englert–Higgs physics, and to show how the usual phenomenology arises from it. This requires to give a precise and gauge-invariant meaning to the underlying physics. This is complicated by the fact that concepts like the Higgs vacuum expectation value or the separation between confinement and the Brout–Englert–Higgs effect lose their meaning beyond perturbation theory. This is addressed by carefully constructing the corresponding theory space and the quantum phase diagram of theories with elementary Higgs fields and gauge interactions. The physical spectrum needs then to be also given in terms of gauge-invariant, i.e. composite, states. Using gauge-invariant perturbation theory, as developed by Fröhlich, Morchio, and Strocchi, it is possible to rederive conventional perturbation theory in this framework. This derivation explicitly shows why the description of the standard model in terms of the unphysical, gauge-dependent, elementary states of the Higgs and W -bosons and Z -boson, but also of the elementary fermions, is adequate and successful. These are unavoidable consequences of the field theory underlying the standard model, from which the usual picture emerges. The validity of this emergence can only be tested non-perturbatively. Such tests, in particular using lattice gauge theory, will be reviewed as well. They fully confirm the underlying mechanisms. In this course it will be seen that the structure of the standard model is very special, and qualitative changes occur beyond it. The extension beyond the standard model will therefore also be reviewed. Particular attention will be given to structural differences arising for phenomenology. Again, non-perturbative tests of these results will be reviewed. Finally, to make this review self-contained a brief discussion of issues like the triviality and hierarchy problem, and how they fit into a fundamental field-theoretical formulation, is included.

    更新日期:2019-03-12
  • New physics searches in nuclear and neutron β decay
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-08-28
    M. González-Alonso, O. Naviliat-Cuncic, N. Severijns

    The status of tests of the standard electroweak model and of searches for new physics in allowed nuclear β decay and neutron decay is reviewed including both theoretical and experimental developments. The sensitivity and complementarity of recent and ongoing experiments are discussed with emphasis on their potential to look for new physics. Measurements are interpreted using a model-independent effective field theory approach enabling to recast the outcome of the analysis in many specific new physics models. Special attention is given to the connection that this approach establishes with high-energy physics. A new global fit of available β -decay data is performed incorporating, for the first time in a consistent way, superallowed 0+→0+ transitions, neutron decay and nuclear decays. The constraints on exotic scalar and tensor couplings involving left- or right-handed neutrinos are determined while a constraint on the pseudoscalar coupling from neutron decay data is obtained for the first time as well. The values of the vector and axial–vector couplings, which are associated within the standard model to Vud and gA respectively, are also updated. The ratio between the axial and vector couplings obtained from the fit under standard model assumptions is CA∕CV=−1.27510(66) . The relevance of the various experimental inputs and error sources is critically discussed and the impact of ongoing measurements is studied. The complementarity of the obtained bounds with other low- and high-energy probes is presented including ongoing searches at the Large Hadron Collider.

    更新日期:2019-02-26
  • Lattice QCD and the anomalous magnetic moment of the muon
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-10-22
    Harvey B. Meyer, Hartmut Wittig

    The anomalous magnetic moment of the muon, aμ , has been measured with an overall precision of 540 ppb by the E821 experiment at BNL. Since the publication of this result in 2004 there has been a persistent tension of 3.5 standard deviations with the theoretical prediction of aμ based on the Standard Model. The uncertainty of the latter is dominated by the effects of the strong interaction, notably the hadronic vacuum polarisation (HVP) and the hadronic light-by-light (HLbL) scattering contributions, which are commonly evaluated using a data-driven approach and hadronic models, respectively. Given that the discrepancy between theory and experiment is currently one of the most intriguing hints for a possible failure of the Standard Model, it is of paramount importance to determine both the HVP and HLbL contributions from first principles. In this review we present the status of lattice QCD calculations of the leading-order HVP and the HLbL scattering contributions, aμhvp andaμhlbl . After describing the formalism to express aμhvp andaμhlbl in terms of Euclidean correlation functions that can be computed on the lattice, we focus on the systematic effects that must be controlled to achieve a first-principles determination of the dominant strong interaction contributions to aμ with the desired level of precision. We also present an overview of current lattice QCD results for aμhvp andaμhlbl , as well as related quantities such as the transition form factor for π0→γ∗γ∗ . While the total error of current lattice QCD estimates of aμhvp has reached the few-percent level, it must be further reduced by a factor ∼5 to be competitive with the data-driven dispersive approach. At the same time, there has been good progress towards the determination of aμhlbl with an uncertainty at the 10−15 %-level.

    更新日期:2019-02-26
  • Heavy quark production and properties of Quark–Gluon Plasma
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-09-05
    Xin Dong, Vincenzo Greco

    Heavy quarks (HQ) are believed to have unique roles for studying QCD at finite temperature and baryon density. By comparing precision measurements of HQ hadron production in heavy-ion collisions with realistic phenomenological model calculations, the goal is to understand interactions and dynamics of HQ propagating through the Quark–Gluon Plasma (QGP) medium and furthermore to characterize the QGP with emergent QCD transport parameters and their temperature dependence. In this article, we will review recent experimental and theoretical achievements on HQ production in high energy p+p , p∕d+A and A+A collisions at RHIC and the LHC. We will discuss what we have learned about the HQ production and how HQs interact with the QGP medium along with their QGP medium properties. Finally, we would like to discuss a few open questions and propose future experimental and theoretical directions towards the physics goals utilizing HQ probes.

    更新日期:2019-02-26
  • Sterile neutrino Dark Matter
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-08-18
    A. Boyarsky, M. Drewes, T. Lasserre, S. Mertens, O. Ruchayskiy

    We review sterile neutrinos as possible Dark Matter candidates. After a short summary on the role of neutrinos in cosmology and particle physics, we give a comprehensive overview of the current status of the research on sterile neutrino Dark Matter. First we discuss the motivation and limits obtained through astrophysical observations. Second, we review different mechanisms of how sterile neutrino Dark Matter could have been produced in the early universe. Finally, we outline a selection of future laboratory searches for keV-scale sterile neutrinos, highlighting their experimental challenges and discovery potential.

    更新日期:2019-02-26
  • Low-energy heavy-ion reactions and the Skyrme effective interaction
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-10-23
    P.D. Stevenson, M.C. Barton
    更新日期:2019-02-26
  • Fast radio bursts
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-07-21
    J.I. Katz

    More than a decade after their discovery, astronomical Fast Radio Bursts remain enigmatic. They are known to occur at “cosmological” distances, implying large energy and radiated power, extraordinarily high brightness temperature and coherent emission. Yet their source objects, the means by which energy is released and their radiation processes remain unknown. This review is organized around these unanswered questions.

    更新日期:2019-02-26
  • Heavy-ion collisions and fission dynamics with the time-dependent Hartree–Fock theory and its extensions
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-07-26
    C. Simenel, A.S. Umar

    Microscopic methods and tools to describe nuclear dynamics have considerably been improved in the past few years. They are based on the time-dependent Hartree–Fock (TDHF) theory and its extensions to include pairing correlations and quantum fluctuations. The TDHF theory is the lowest level of approximation of a range of methods to solve the quantum many-body problem, showing its universality to describe many-fermion dynamics at the mean-field level. The range of applications of TDHF to describe realistic systems allowing for detailed comparisons with experiment has considerably increased. For instance, TDHF is now commonly used to investigate fusion, multi-nucleon transfer and quasi-fission reactions. Thanks to the inclusion of pairing correlations, it has also recently led to breakthroughs in our description of the saddle to scission evolution, and, in particular, the non-adiabatic effects near scission. Beyond mean-field approaches such as the time-dependent random-phase approximation (TDRPA) and stochastic mean-field methods have reached the point where they can be used for realistic applications. We review recent progresses in both techniques and applications to heavy-ion collision and fission.

    更新日期:2019-02-26
  • Breakup reactions of light and medium mass neutron drip line nuclei
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-06-28
    R. Chatterjee, R. Shyam

    The formal theories of breakup reactions are reviewed. The direct breakup mechanism that is formulated within the framework of the post-form distorted-wave Born approximation, is discussed in detail. In this theory, which requires the information about only the ground state wave function of the projectile, the fragment–target interactions are included to all orders while fragment–fragment interaction is treated only in the first order. We put special emphasis on the breakup reactions of the near neutron drip line nuclei on heavy nuclear targets, which are dominated by the pure Coulomb breakup mechanism. The applicability of this theory to describe such reactions involving both spherical as well as deformed projectiles, is demonstrated by comparing the calculations with breakup data for total, energy and angle integrated cross sections and momentum distributions of fragments emitted in such reactions. Roles played by the pure Coulomb, pure nuclear and the Coulomb–nuclear interference terms in describing the breakup observables are discussed. Postacceleration effects in the Coulomb breakup of neutron halo nuclei are elaborated. The function of the pure Coulomb breakup mechanism in the one-neutron removal reactions of the type A(a,bγ)X on heavy target nuclei is underlined. The relationship between the parallel momentum distribution of the fragments and the break down of the magic numbers as the neutron drip line is approached, is highlighted.

    更新日期:2019-02-26
  • New developments in calorimetric particle detection
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-07-24
    Richard Wigmans

    In nuclear, particle and astroparticle physics experiments, calorimeters are used to measure the properties of particles with kinetic energies that range from a fraction of 1 eV to 1020eV or more. These properties are not necessarily limited to the energy carried by these particles, but may concern the entire four-vector, including the particle mass and type. In many modern experiments, large calorimeter systems play a central role, and this is expected to be no different for experiments that are currently being planned/designed for future accelerators. In this paper, the state of the art as well as new developments in calorimetry are reviewed. The latter are of course inspired by the perceived demands of future experiments, and/or the increasing demands of the current generation of experiments, as these are confronted with, for example, increased luminosity. These demands depend on the particles to be detected by the calorimeter. In electromagnetic calorimeters, radiation hardness of the detector components is a major concern. The generally poor performance of the current generation of hadron calorimeters is considered inadequate for future experiments, and a lot of the R&D in the past decade has focused on improving this performance. The root causes of the problems are investigated and different methods that have been exploited to remedy this situation are evaluated. In the past two decades, experiments in astroparticle physics have started to make major contributions to our fundamental understanding of physics and of a variety of processes that are inaccessible in laboratory experiments here on Earth. These experiments typically make use of calorimetric particle detection. At the extreme low end of the energy spectrum, ingenious instruments are used to study phenomena involving energy transfers of the order of 1 eV using calorimetric methods. In separate sections, some salient aspects of this work are reviewed.

    更新日期:2019-02-26
  • New experimental approaches in the search for axion-like particles
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-06-19
    Igor G. Irastorza, Javier Redondo

    Axions and other very light axion-like particles appear in many extensions of the Standard Model, and are leading candidates to compose part or all of the missing matter of the Universe. They also appear in models of inflation, dark radiation, or even dark energy, and could solve some long-standing astrophysical anomalies. The physics case of these particles has been considerably developed in recent years, and there are now useful guidelines and powerful motivations to attempt experimental detection. Admittedly, the lack of a positive signal of new physics at the high energy frontier, and in underground detectors searching for weakly interacting massive particles, is also contributing to the increase of interest in axion searches. The experimental landscape is rapidly evolving, with many novel detection concepts and new experimental proposals. An updated account of those initiatives is lacking in the literature. In this review we attempt to provide such an update. We will focus on the new experimental approaches and their complementarity, but will also review the most relevant recent results from the consolidated strategies and the prospects of new generation experiments under consideration in the field. We will also briefly review the latest developments of the theory, cosmology and astrophysics of axions and we will discuss the prospects to probe a large fraction of relevant parameter space in the coming decade.

    更新日期:2018-07-12
  • Current unknowns in the three-neutrino framework
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-05-18
    F. Capozzi, E. Lisi, A. Marrone, A. Palazzo

    We present an up-to-date global analysis of data coming from neutrino oscillation and non-oscillation experiments, as available in April 2018, within the standard framework including three massive and mixed neutrinos. We discuss in detail the status of the three-neutrino (3ν) mass-mixing parameters, both known and unknown. Concerning the latter, we find that: normal ordering (NO) is favored over inverted ordering (IO) at 3σ level; the Dirac CP phase is constrained within ∼15% (∼9% ) uncertainty in NO (IO) around nearly-maximal CP-violating values; the octant of the largest mixing angle and the absolute neutrino masses remain undetermined. We briefly comment on other unknowns related to theoretical and experimental uncertainties (within 3ν ) or possible new states and interactions (beyond 3ν ).

    更新日期:2018-07-12
  • Radioactive nuclei from cosmochronology to habitability
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-05-22
    M. Lugaro, U. Ott, Á. Kereszturi

    In addition to long-lived radioactive nuclei like U and Th isotopes, which have been used to measure the age of theGalaxy, also radioactive nuclei with half-lives between 0.1 and 100 million years (short-lived radionuclides, SLRs) were present in the early Solar System (ESS), as indicated by high-precision meteoritic analysis. We review the most recent meteoritic data and describe the nuclear interaction processes responsible for the creation of SLRs in different types of stars and supernovae. We show how the evolution of radionuclide abundances in the Milky Way Galaxy can be calculated based on their stellar production. By comparing predictions for the evolution of galactic abundances to the meteoritic data we can build up a time line for the nucleosynthetic events that predated the birth of the Sun, and investigate the lifetime of the stellar nursery where the Sun was born. We then review the scenarios for the circumstances and the environment of the birth of the Sun, within such a stellar nursery, that have been invoked to explain the abundances in the ESS of the SLRs with the shortest lives — of the order of million years or less. Finally, we describe how the heat generated by radioactive decay and in particular by the abundant  26Al in the ESS had important consequences for the thermo-mechanical and chemical evolution of planetesimals, and discuss possible implications on the habitability of terrestrial-like planets. We conclude with a set of open questions and future directions related to our understanding of the nucleosynthetic processes responsible for the production of SLRs in stars, their evolution in the Galaxy, the birth of the Sun, and the connection with the habitability of extra-solar planets.

    更新日期:2018-07-12
  • Opening a new window onto the universe with IceCube
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-05-17
    Markus Ahlers, Francis Halzen

    Weakly interacting neutrinos are ideal astronomical messengers because they travel through space without deflection by magnetic fields and, essentially, without absorption. Their weak interaction also makes them notoriously difficult to detect, with observation of high-energy neutrinos from distant sources requiring kilometer-scale detectors. The IceCube project transformed a cubic kilometer of natural Antarctic ice at the geographic South Pole into a Cherenkov detector. It discovered a flux of cosmic neutrinos in the energy range from 10 TeV to 10 PeV, predominantly extragalactic in origin. Their corresponding energy density is close to that of high-energy photons detected by gamma-ray satellites and ultra-high-energy cosmic rays observed with large surface detectors. Neutrinos are therefore ubiquitous in the nonthermal universe, suggesting a more significant role of protons (nuclei) relative to electrons than previously anticipated. Thus, anticipating an essential role for multimessenger astronomy, IceCube is planning significant upgrades of the present instrument as well as a next-generation detector. Similar detectors are under construction in the Mediterranean Sea and Lake Baikal.

    更新日期:2018-07-12
  • Relativistic anisotropic hydrodynamics
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-05-12
    Mubarak Alqahtani, Mohammad Nopoush, Michael Strickland

    In this paper we review recent progress in relativistic anisotropic hydrodynamics. We begin with a pedagogical introduction to the topic which takes into account the advances in our understanding of this topic since its inception. We consider both conformal and non-conformal systems and demonstrate how one can implement a realistic equation of state using a quasiparticle approach. We then consider the inclusion of non-spheroidal (non-ellipsoidal) corrections to leading-order anisotropic hydrodynamics and present the findings of the resulting second-order viscous anisotropic hydrodynamics framework. We compare the results obtained in both the conformal and non-conformal cases with exact solutions to the Boltzmann equation and demonstrate that, in all known cases, anisotropic hydrodynamics best reproduces the exact solutions. Based on this success, we then discuss the phenomenological application of anisotropic hydrodynamics. Along these lines, we review techniques which can be used to convert a momentum-space anisotropic fluid into hadronic degrees of freedom by generalizing the original idea of Cooper–Frye freeze-out to momentum-space anisotropic systems. And, finally, we present phenomenological results of 3+1d quasiparticle anisotropic hydrodynamic simulations and compare them to experimental data produced in 2.76 TeV Pb–Pb collisions at the LHC. Our results indicate that anisotropic hydrodynamics provides a promising framework for describing the dynamics of the momentum-space anisotropic QGP created in heavy-ion collisions.

    更新日期:2018-07-12
  • Neutron physics with accelerators
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-02-24
    N. Colonna, F. Gunsing, F. Käppeler

    Neutron-induced nuclear reactions are of key importance for a variety of applications in basic and applied science. Apart from nuclear reactors, accelerator-based neutron sources play a major role in experimental studies, especially for the determination of reaction cross sections over a wide energy span from sub-thermal to GeV energies. After an overview of present and upcoming facilities, this article deals with state-of-the-art detectors and equipment, including the often difficult sample problem. These issues are illustrated at selected examples of measurements for nuclear astrophysics and reactor technology with emphasis on their intertwined relations.

    更新日期:2018-07-12
  • Nuclear equation of state from ground and collective excited state properties of nuclei
    Prog. Part. Nucl. Phys. (IF 10.764) Pub Date : 2018-05-01
    X. Roca-Maza, N. Paar

    This contribution reviews the present status on the available constraints to the nuclear equation of state (EoS) around saturation density from nuclear structure calculations on ground and collective excited state properties of atomic nuclei. It concentrates on predictions based on self-consistent mean-field calculations, which can be considered as an approximate realization of an exact energy density functional (EDF). EDFs are derived from effective interactions commonly fitted to nuclear masses, charge radii and, in many cases, also to pseudo-data such as nuclear matter properties. Although in a model dependent way, EDFs constitute nowadays a unique tool to reliably and consistently access bulk ground state and collective excited state properties of atomic nuclei along the nuclear chart as well as the EoS. For comparison, some emphasis is also given to the results obtained with the so called ab initio approaches that aim at describing the nuclear EoS based on interactions fitted to few-body data only. Bridging the existent gap between these two frameworks will be essential since it may allow to improve our understanding on the diverse phenomenology observed in nuclei. Examples on observations from astrophysical objects and processes sensitive to the nuclear EoS are also briefly discussed. As the main conclusion, the isospin dependence of the nuclear EoS around saturation density and, to a lesser extent, the nuclear matter incompressibility remain to be accurately determined. Experimental and theoretical efforts in finding and measuring observables specially sensitive to the EoS properties are of paramount importance, not only for low-energy nuclear physics but also for nuclear astrophysics applications.

    更新日期:2018-07-12
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