Cosmic ray spectrum of protons plus helium nuclei between 6 and 158 TeV from HAWC data
A. Albert, R. Alfaro, C. Álvarez, José Roberto Ángeles Camacho, J. C. Arteaga‐Velázquez, K. P. Arunbabu, D. Avila Rojas, H. A. Ayala Solares, E. Belmont‐Moreno, C. Brisbois, K. S. Caballero‐Mora, T. Capistrán, A. Carramiñana, S. Casanova, U. Cotti, J. Cotzomi, E. De la Fuente, R. Díaz Hernández, M. A. DuVernois, Mora Durocher, J. C. Díaz–Vélez, C. Espinoza, N. Fraija, J. A. García-González, F. Garfias, M. M. González, J. A. Goodman, J. P. Harding, B. Hona, Dezhi Huang, F. Hueyotl‐Zahuantitla, P. Hüntemeyer, A. Iriarte, Vikas Joshi, D. Kieda, Gerd J. Kunde, A. Lara, W. H. Lee, H. León Vargas, J. Linnemann, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martı́nez, J. Martínez-Castro, J. Matthews, P. Miranda-Romagnoli, J. A. Morales-Soto, E. Moreno, M. Mostafá, A. Nayerhoda, L. Nellen, M. Newbold, R. Noriega-Papaqui, N. Omodei, E. G. Pérez‐Pérez, Chang Dong Rho, D. Rosa‐González, H. Salazar, F. Salesa Greus, A. Sandoval, José Serna-Franco, A. J. Smith, R. W. Springer, Kirsten Tollefson, I. Torres, R. Torres-Escobedo, F. Ureña-Mena, L. Villaseñor, X. Wang, E. Willox, H. Zhou, C. de León, J. D. Álvarez, G. B. Yodh, A. Zepeda
Abstract
A measurement with high statistics of the differential energy spectrum of light elements in cosmic rays, in particular, of primary H plus He nuclei, is reported. The spectrum is presented in the energy range from 6 to 158 TeV per nucleus. Data was collected with the High Altitude Water Cherenkov (HAWC) Observatory between June 2015 and June 2019. The analysis was based on a Bayesian unfolding procedure, which was applied on a subsample of vertical HAWC data that was enriched to 82% of events induced by light nuclei. To achieve the mass separation, a cut on the lateral age of air shower data was set guided by predictions of CORSIKA/QGSJET-II-04 simulations. The measured spectrum is consistent with a broken power-law spectrum and shows a kneelike feature at around $E={24.0}_{\ensuremath{-}3.1}^{+3.6}\text{ }\text{ }\mathrm{TeV}$, with a spectral index $\ensuremath{\gamma}=\ensuremath{-}2.51\ifmmode\pm\else\textpm\fi{}0.02$ before the break and with $\ensuremath{\gamma}=\ensuremath{-}2.83\ifmmode\pm\else\textpm\fi{}0.02$ above it. The feature has a statistical significance of $4.1\ensuremath{\sigma}$. Within systematic uncertainties, the significance of the spectral break is $0.8\ensuremath{\sigma}$.