High-energy cosmic rays and tests of basic principles of Physics

Abstract

Abstract. With the present understanding of data, the observed flux suppression for ultra-high energy cosmic rays (UHECR) at energies above 4.10 19 eV can be a signature of the Greisen-Zatsepin-Kuzmin (GZK) cutoff or be related to a similar mechanism. But it may also correspond, for instance, to the maximum energies available at the relevant sources. In both cases, violations of special relativity modifying cosmic-ray propagation or acceleration at very high energy can potentially play a role. Other violations of fundamental principles of standard particle physics (quantum mechanics, energy and momentum conservation, vacuum homogeneity and "static" properties, effective space dimensions, quark confinement...) can also be relevant at these energies. In particular, UHECR data would in principle allow to set bounds on Lorentz symmetry violation (LSV) in patterns incorporating a privileged local reference frame (the "vacuum rest frame", VRF). But the precise analysis is far from trivial, and other effects can also be present. The effective parameters can be related to Planckscale physics, or even to physics beyond Planck scale, as well as to the dynamics and effective symmetries of LSV for nucleons, quarks, leptons and the photon. LSV can also be at the origin of GZK-like effects. In the presence of a VRF, and contrary to a "grand unification" view, LSV and other violations of standard principles can modify the internal structure of particles at very high energy and conventional symmetries may cease to be valid at energies close to the Planck scale. We present an updated discussion of these topics, including experimental prospects, new potentialities for high-energy cosmic ray phenomenology and the possible link with unconventional pre-Big Bang scenarios, superbradyon (superluminal preon) patterns... The subject of a possible superluminal propagation of neutrinos at accelerator energies is also dealt with.

BICEP2, Planck, spinorial space-time, pre-Big Bang.

“…Fundamental physics at ultra-high energy (UHE), including possible effects of new physics, remains poorly known [41,92] and requires further experimental and theoretical effort. It is even not yet clear [102,103] if the observed fall of the ultra-high energy cosmic-ray (UHECR) spectrum is a signature of the Greisen-Zatsepin-Kuzmin (GZK) cutoff or corresponds to the maximum EPJ Web of Conferences 03014-p. 16 energies available at astrophysical sources.…”

Tests and prospects of new physics at very high energy. Beyond the standard basic principles, and beyond conventional matter and space-time. On the possible origin of Quantum Mechanics.

“…The degree of validity of the standard fundamental principles of Physics for the nature, internal properties, propagation and interactions of ultra-high energy (UHE) particles including the existing ultra-high energy cosmic rays (UHECR) remains by now a basic open question [52][53][54]. Answering it will require further experimental, theoretical and phenomenological work.…”

“…Contrary to the usual prejudices, such symmetries do not necessarily become more exact as energy increases [52,54]. Work on this subject should include the search for possible signatures of a transition energy scale between standard physics and new physics with comparatively strong symmetry breaking [52,53].…”

“…Similarly, energy-dependent deformations can be considered for all basic principles of standard physics, including quantum mechanics [41,54]. In all cases, a transition energy similar to E trans can exist.…”

“…But a new basic physics, beyond standard quantum dynamics or just best adapted to the reality of vacuum in most of the Universe, may manifest itself in other situations. It can be potentially detectable through UHECR experiments and other cosmic-ray studies [53,54], as well as in suitable cosmological observations [40,44].…”