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The shape of the cosmic ray proton spectrum
Astroparticle Physics ( IF 3.5 ) Pub Date : 2020-07-01 , DOI: 10.1016/j.astropartphys.2020.102441 Paolo Lipari , Silvia Vernetto
Astroparticle Physics ( IF 3.5 ) Pub Date : 2020-07-01 , DOI: 10.1016/j.astropartphys.2020.102441 Paolo Lipari , Silvia Vernetto
Recent observations of cosmic ray protons in the energy range $10^2$--$10^5$~GeV have revealed that the spectrum cannot be described by a simple power law. A hardening of the spectrum around an energy of order few hundred~GeV, first observed by the magnetic spectrometers PAMELA and AMS02, has now been confirmed by several calorimeter detectors (ATIC, CREAM, CALET, NUCLEON and DAMPE). These new measurements reach higher energy and indicate that the hardening corresponds to a larger step in spectral index than what estimated by the magnetic spectrometers. Data at still higher energy (by CREAM, NUCLEON and DAMPE) show that the proton spectrum undergoes a marked softening at $E \approx 10^4$~GeV. Understanding the origin of these unexpected spectral features is a significant challenge for models of the Galactic cosmic rays. An important open question is whether additional features are present in the proton spectrum between the softening and the "Knee". Extensive Air Shower detectors, using unfolding procedures that require the modeling of cosmic ray showers in the atmosphere, estimated the proton flux below and around the Knee (at $E \simeq 3$~PeV). These results however have large systematic uncertainties and are in poor agreement with each other. The measurement in the PeV energy range, recently presented by IceTop/IceCube, indicates a proton flux higher than extrapolations of the direct measurements calculated assuming a constant slope, and therefore requires the existence of an additional spectral hardening below the Knee. A clarification of this point is very important for an understanding of the origin of the Galactic cosmic rays, and is also essential for a precise calculation of the spectra of atmospheric neutrinos in the energy range ($E \gtrsim 10$~TeV) where they constitute the foreground for the emerging astrophysical $\nu$ signal.
中文翻译:
宇宙射线质子谱的形状
最近对能量范围为 $10^2$--$10^5$~GeV 的宇宙射线质子的观察表明,光谱不能用简单的幂律来描述。大约几百~GeV 能量的光谱硬化,首先由磁光谱仪 PAMELA 和 AMS02 观察到,现在已经由几个量热仪检测器(ATIC、CREAM、CALET、NUCLEON 和 DAMPE)证实。这些新的测量值达到了更高的能量,并表明硬化对应于比磁光谱仪估计的更大的光谱指数步长。更高能量下的数据(通过 CREAM、NUCLEON 和 DAMPE)表明,质子光谱在 $E\约 10^4$~GeV 处经历了明显的软化。了解这些意想不到的光谱特征的起源是银河宇宙射线模型的重大挑战。一个重要的悬而未决的问题是在软化和“膝盖”之间的质子光谱中是否存在附加特征。广泛的空气簇射探测器使用需要对大气中的宇宙射线簇进行建模的展开程序,估计膝部下方和周围的质子通量(在 $E \simeq 3 $~PeV)。然而,这些结果具有很大的系统不确定性,并且彼此不一致。最近由 IceTop/IceCube 提出的 PeV 能量范围内的测量表明质子通量高于假设恒定斜率计算的直接测量的外推,因此需要在拐点下方存在额外的光谱硬化。澄清这一点对于理解银河系宇宙射线的起源非常重要,
更新日期:2020-07-01
中文翻译:
宇宙射线质子谱的形状
最近对能量范围为 $10^2$--$10^5$~GeV 的宇宙射线质子的观察表明,光谱不能用简单的幂律来描述。大约几百~GeV 能量的光谱硬化,首先由磁光谱仪 PAMELA 和 AMS02 观察到,现在已经由几个量热仪检测器(ATIC、CREAM、CALET、NUCLEON 和 DAMPE)证实。这些新的测量值达到了更高的能量,并表明硬化对应于比磁光谱仪估计的更大的光谱指数步长。更高能量下的数据(通过 CREAM、NUCLEON 和 DAMPE)表明,质子光谱在 $E\约 10^4$~GeV 处经历了明显的软化。了解这些意想不到的光谱特征的起源是银河宇宙射线模型的重大挑战。一个重要的悬而未决的问题是在软化和“膝盖”之间的质子光谱中是否存在附加特征。广泛的空气簇射探测器使用需要对大气中的宇宙射线簇进行建模的展开程序,估计膝部下方和周围的质子通量(在 $E \simeq 3 $~PeV)。然而,这些结果具有很大的系统不确定性,并且彼此不一致。最近由 IceTop/IceCube 提出的 PeV 能量范围内的测量表明质子通量高于假设恒定斜率计算的直接测量的外推,因此需要在拐点下方存在额外的光谱硬化。澄清这一点对于理解银河系宇宙射线的起源非常重要,