Phenomenological Effects of CPT and Lorentz Invariance Violation in Particle and Astroparticle Physics

Abstract

It is well known that a fundamental theorem of Quantum Field Theory (QFT) set in flat spacetime ensures the CPT invariance of the theory. This symmetry is strictly connected to the Lorentz covariance, and consequently to the fundamental structure of spacetime. Therefore it may be interesting to investigate the possibility of departure from this fundamental symmetry, since it can furnish a window to observe possible effects of a more fundamental quantum gravity theory in a “lower energy limit”. Moreover, in the past, the inquiry of symmetry violations provided a starting point for new physics discoveries. A useful physical framework for this kind of search is provided by astroparticle physics, thanks to the high energy involved and to the long path travelled by particles accelerated by an astrophysical object and then revealed on Earth. Astrophysical messengers are therefore very important probes for investigating this sector, involving high energy photons, charged particles, and neutrinos of cosmic origin. In addition, one can also study artificial neutrino beams, investigated at accelerator experiments. Here we discuss the state of art for all these topics and some interesting new proposals, both from a theoretical and phenomenological point of view.

Predictions of Ultra-High Energy Cosmic Ray Propagation in the Context of Homogeneously Modified Special Relativity

“…It is well known that Lorentz violation does not imply the CPT one [28][29][30], whereas the opposite statement is widely debated in literature [31][32][33][34][35]. In HMSR, every particle species has its own personal MDR, with a specific perturbation f .…”

“…Indeed as a result, it is possible to introduce LIV preserving the CPT symmetry. It is well known that Lorentz violation does not imply the CPT one [28,29,30], whereas the opposite statement is widely debated in literature [31,32,33,34,35].…”

On Mikheyev–Smirnov–Wolfenstein Resonance Widths

“…It is proven experimentally that the strong and electromagnetic interactions preserve the aforementioned symmetries. See reviews [1,2].…”

Non-minimal Lorentz invariance violation in light of muon anomalous magnetic moment and long-baseline neutrino oscillation data

“…Only recently, the integrity of SM has started to falter as mounting evidence from electroweak precision observables, CKM matrix element measurements and neutrino experiments are showing divergences between experiments and SM predictions. As physicists look for methods to accommodate SM physics in a more complete theoretical framework, searching evidence of violation to fundamental symmetries could provide hints of the underlying theory, such as the formulation of quantum gravity [1][2][3].…”