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UHECR mass composition from anisotropy of their arrival directions with the Telescope Array SD

par Kuznetsov, Mikhail Yu M.;Tiniakov, Petr ;Kuzmin, Vadim;Kwon, Y. Y.J.
Référence Pos proceedings of science, 395, 294
Publication Publié, 2022-03-01

Article révisé par les pairs

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Résumé :

We propose a new method for the estimation of ultra-high energy cosmic ray (UHECR) mass composition from a distribution of their arrival directions. The method employs a test statistic (TS) based on a characteristic deflection of UHECR events with respect to the distribution of luminous matter in the local Universe modeled with a flux-weighed 2MRS catalog. Making realistic simulations of the mock UHECR sets, we show that this TS is robust to the presence of galactic and non-extreme extra-galactic magnetic fields and sensitive to the mass composition of events in a set. We apply the method to Telescope Array surface detector data for 11 years and derive new independent constraints on fraction of protons and iron in p-Fe mix at E > 10 EeV. At 10 < E < 100 EeV the data favors increase of allowed proton fraction and decrease of allowed iron fraction, while at E > 100 EeV — pure iron or even more massive composition. This result is in tension with Auger composition model inferred from spectrum–Xmax fit at 2.7σ (2.0σ) for PT’11 (JF’12) regular GMF model.