Abstract
Ultra high energy cosmic rays (UHECRs) may interact with photon backgrounds and thus the universe is opaque to their propagation. Many Lorentz Invariance Violation (LIV) theories predict a dilation of the expected horizon from which UHECRs can arrive to Earth, in some case even making the interaction probability negligible. In this work, we investigate this effect in the context of the LIV theory that goes by the name of Homogeneously Modified Special Relativity (HMSR). In this work, making use of a specifically modified version of the SimProp simulation program in order to account for the modifications introduced by the theory to the propagation of particles, the radius of the proton opacity horizon (GZK sphere), and the attenuation length for the photopion production process are simulated and the modifications of these quantities introduced by the theory are studied.
Highlights
Cosmic rays (CRs) are the part of the radiation of extraterrestrial origin made up by charged particles
This work is structured as follows: in Section 2, we present the Lorentz Invariance Violation (LIV) model employed here (HMSR) [19]; in Section 3, we introduce ultra-high energy cosmic rays (UHECRs) propagation; in Section 4, we illustrate the modifications introduced in the UHECR physics by LIV in order to obtain a modified SimProp software version able to simulate their free propagation in a Lorentz violating scenario; in Section 5, we summarize the obtained results and, in Section 6, we present the future perspectives to extend the analysis to a more realistic CR composition scenario
One can state that the GZK sphere enlargement and the attenuation length increase imply that the introduction of LIV determines a reduction of the Universe opacity for Lorentz covariance underlies nowadays our knowledge of physics; small departures from this fundamental symmetry are supposed as possible residual evidence of the phenomenology induced by quantum gravity
Summary
Cosmic rays (CRs) are the part of the radiation of extraterrestrial origin made up by charged particles. The UHECR sources are still unknown; the physics correlated with their propagation can be exploited to investigate new phenomena, such as the hypothetical ones induced by quantum gravity and described by LIV theories These perturbations can be considered as Planck scale physics residual effects in the low energy limit; they may be an open window on possible phenomenology induced by quantum gravity. This work is structured as follows: in Section 2, we present the LIV model employed here (HMSR) [19]; in Section 3, we introduce UHECR propagation; in Section 4, we illustrate the modifications introduced in the UHECR physics by LIV in order to obtain a modified SimProp software version able to simulate their free propagation in a Lorentz violating scenario; in Section 5, we summarize the obtained results and, in Section 6, we present the future perspectives to extend the analysis to a more realistic CR composition scenario
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