Abstract
With the present understanding of data, the observed flux suppression for ultra-high energy cosmic rays (UHECR) at energies above 4.10E19 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, 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 Planck-scale 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. (Contribution to the International Conference on New Frontiers in Physics, ICFP 2012, Kolymbari, Crete, June 10-16 2012)
Highlights
ultra-high energy cosmic rays (UHECR) data would in principle allow to set bounds on Lorentz symmetry violation (LSV) in patterns incorporating a privileged local reference frame
Assuming the VRF to be close to that naturally suggested by cosmic microwave background radiation (CMB), the rest frames used in UHECR and other experiments will move at nonrelativistic speed with respect to the VRF
As already emphasized in [9, 37] and further discussed here, UHECR experiments provide a powerful and unique microscope directly focused on the Planck scale and beyond
Summary
EPJ Web of Conferences suppressing mechanism of a different dynamical origin All these phenomena can be sensitive, for instance, to violations of standard special relativity modifying cosmic-ray production [7, 8], propagation [9, 10] or acceleration [11, 12] at very high energy. From a cosmological point of view, possible UHE violations of standard fundamental principles can possibly be related to pre-Big Bang scenarios [22, 23] where the new physics would be expected to play a leading role In this contribution, we present an updated discussion of UHECR data and phenomenology, paying special attention to unconventional theoretical motivations and to alternatives to standard interpretations of data. As the OPERA claim [24] on a possible superluminal propagation of the muon neutrino had not yet been withdrawn [43] when this conference was announced, we briefly discuss the consistency problems [25, 26] of a 2.5 x 10−5 critical speed anomaly for light neutrinos including the muon neutrino
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