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Deconfinement and degrees of freedom in pp and \(A-A\) collisions at LHC energies

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Abstract

We present the extraction of the temperature by analyzing the charged particle transverse momentum spectra in lead–lead (Pb–Pb) and proton–proton (pp) collisions at LHC energies from the ALICE Collaboration using the Color String Percolation Model (CSPM). From the measured energy density \({\varvec{\varepsilon }}\) and the temperature T the dimensionless quantity \({\varvec{\varepsilon }/}T^{4}\) is obtained to get the degrees of freedom (DOF), \({\varvec{\varepsilon }}/T^{4} = \hbox {DOF} \,{ \pi ^{2}}/30\). We observe for the first time a two-step behavior in the increase of DOF, characteristic of deconfinement, above the hadronization temperature at temperature \(\sim \) 210 MeV for both Pb–Pb and pp collisions and a sudden increase to the ideal gas value of \(\sim 47\) corresponding to three quark flavors in the case of Pb–Pb collisions.

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Data Availability Statement

This manuscript has no associated data or the data will not be deposited. [Authors’ comment: Published data from ALICE Collaboration was used.]

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Acknowledgements

A. M. acknowledges the post-doctoral fellowship of DGAPA UNAM. Partial support was received by DGAPA-PAPIIT IN109817 and CONACYT A1-S-16215 projects. A. M. also thanks the Hungarian National Research, Development and Innovation Office (NKFIH) under the contract numbers OTKA K120660, NKFIH 2019-2.1.11-T ET-2019-00078, and 2019-2.1.11-T ET-2019-00050. C. P. thanks the grant Maria de Maeztu Unit of excellence MDM-2016-0682 of Spain, the support of Xunta de Galicia under the project ED431C 2017 and project FPA 2017-83814 of Ministerio de Ciencia e Innovacion of Spain and FEDER. GP acknowledges the DGAPA sabatical fellowship.

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Authors and Affiliations

  1. Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, México Distrito Federal, 04510, México

    Aditya N Mishra & Guy Paić

  2. Wigner Research Center for Physics, 1121, Budapest, Hungary

    Aditya N Mishra

  3. Departamento de Fisica de Particulas, Universidale de Santiago de Compostela and Instituto Galego de Fisica de Atlas Enerxias(IGFAE), 15782, Santiago de Compostela, Spain

    C. Pajares

  4. Department of Physics and Astronomy, Purdue University, West Lafayette, IN, 47907, USA

    R. P. Scharenberg & B. K. Srivastava

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  1. Aditya N Mishra
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  2. Guy Paić
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Correspondence to B. K. Srivastava.

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Communicated by Silvia Masciocchi.

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Mishra, A.N., Paić, G., Pajares, C. et al. Deconfinement and degrees of freedom in pp and \(A-A\) collisions at LHC energies. Eur. Phys. J. A 57, 245 (2021). https://doi.org/10.1140/epja/s10050-021-00552-2

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  • DOI: https://doi.org/10.1140/epja/s10050-021-00552-2

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