Cosmic rays and hadronic interactions

Abstract

Abstract. The study of cosmic rays, and more in general of the "high energy universe" is at the moment a vibrant field that, thanks to the observations by several innovative detectors for relativistic charged particles, gamma-rays, and neutrinos continue to generate surprising and exciting results. The progress in the field is rapid but many fundamental problems remain open. There is an intimate relation between the study of the high energy universe and the study of the properties of hadronic interactions. High energy cosmic rays can only be studied detecting the showers they generate in the atmosphere, and for the interpretation of the data one needs an accurate modeling of the collisions between hadrons. Also the study of cosmic rays inside their sources and in the Galaxy requires a precise description of hadronic interactions. A program of experimental studies at the LHC and at lower energy, designed to address the most pressing problems, could significantly reduce the existing uncertainties and is very desirable. Such an experimental program would also have a strong intrinsic scientific interest, allowing the broadening and deepening of our understanding of Quantum Chromo Dynamics in the non-perturbative regime, the least understood sector of the Standard Model of particle physics. It should also be noted that the cosmic ray spectrum extends to particles with energy E ∼ 10 20 eV, or a nucleon-nucleon c.m. energy √ s 430 TeV, 30 times higher than the current LHC energy. Cosmic ray experiments therefore offer the possibility to perform studies on the properties of hadronic interactions that are impossible at accelerators.

Neutrino events at IceCube and the Fermi bubbles

“…When comparing the data to theoretical models of high energy neutrino fluxes, it is natural to expect that multiple sources might contribute to the observed signal. Although prompt atmospheric neutrinos could fit some of the data [3], distant astrophysical sources are the most natural explanation. Cosmological emitters would likely produce a uniform, diffuse flux, and the spatial distribution of the events is compatible with this hypothesis.…”