Cosmic ray knee and new physics at the TeV scale

TL;DR

This paper explores the hypothesis that the cosmic ray knee results from new TeV-scale physics involving proton-dark matter interactions, predicting specific energy-dependent effects and potential observational signatures.

Contribution

It proposes a novel explanation for the cosmic ray knee based on enhanced proton-dark matter cross sections at TeV energies, linking it to new physics and dark matter properties.

Findings

Cross section must grow like E^{0.4+β} above the knee.

Knees scale with atomic mass, consistent with KASKADE data.

Neutrino interactions would show a threshold at ~10^8 GeV.

Abstract

We analyze the possibility that the cosmic ray knee appears at an energy threshold where the proton-dark matter cross section becomes large due to new TeV physics. It has been shown that such interactions could break the proton and produce a diffuse gamma ray flux consistent with MILAGRO observations. We argue that this hypothesis implies knees that scale with the atomic mass for the different nuclei, as KASKADE data seem to indicate. We find that to explain the change in the spectral index in the flux from E^{-2.7} to E^{-3.1} the cross section must grow like E^{0.4+\beta} above the knee, where \beta=0.3-0.6 parametrizes the energy dependence of the age (\tau \propto E^{-\beta}) of the cosmic rays reaching the Earth. The hypothesis also requires mbarn cross sections (that could be modelled with TeV gravity) and large densities of dark matter (that could be clumped around the sources of cosmic rays). We argue that neutrinos would also exhibit a threshold at E=(m_\chi/m_p)E_{knee}\approx 10^8 GeV where their interaction with a nucleon becomes strong. Therefore, the observation at ICECUBE or ANITA of standard neutrino events above this threshold would disprove the scenario.