arXiv subjects

J. S. Diaz

Publications and source records attributed to J. S. Diaz.

5 recordsLinked to original sources

arXiv2016

Changes in extensive air showers from isotropic Lorentz violation in the photon sector

We consider a theory with isotropic nonbirefringent Lorentz violation in the photon sector and explore the effects on the development of the electromagnetic component of extensive air showers in the Earth atmosphere. Specifically, we consider the case of a "fast" photon with a phase velocity larger than the maximum attainable velocity of a massive Dirac fermion (this case corresponds to a negative Lorentz-violating parameter $κ$ in the action). Shower photons with above-threshold energies decay promptly into electron-positron pairs, instead of decaying by the conventional production of electron-positron pairs in the background fields of atomic nuclei. This rapid production of charged leptons accelerates the shower development, decreasing the atmospheric depth of the shower maximum ($X_\text{max}$) by an amount which could be measured by cosmic-ray observatories. Precise measurements of $X_\text{max}$ could then improve existing limits on the negative Lorentz-violating parameter $κ$ by several orders of magnitude.

hep-ph↗

arXiv2016

Neutrino refraction by the cosmic neutrino background

We have determined the dispersion relation of a neutrino test particle propagating in the cosmic neutrino background. Describing the relic neutrinos and antineutrinos from the hot big bang as a dense medium, a matter potential or refractive index is obtained. The vacuum neutrino mixing angles are unchanged, but the energy of each mass state is modified. Using a matrix in the space of neutrino species, the induced potential is decomposed into a part which produces signatures in beta-decay experiments and another part which modifies neutrino oscillations. The low temperature of the relic neutrinos makes a direct detection extremely challenging. From a different point of view, the identified refractive effects of the cosmic neutrino background constitute an ultralow background for future experimental studies of nonvanishing Lorentz violation in the neutrino sector.

hep-ph↗

arXiv2015

Parton-model calculation of a nonstandard decay process in isotropic modified Maxwell theory

We have performed a calculation in the parton-model approximation of a nonstandard decay process in isotropic modified Maxwell theory coupled to standard Dirac theory, with a single Lorentz-violating parameter $κ$ in the photonic sector. Previous calculations of this process (vacuum Cherenkov radiation by a proton for the theory with $κ>0$) were performed for pointlike particles, and an upper bound on $κ$ at the $10^{-19}$ level was obtained from experimental data on ultra-high-energy cosmic rays. The parton-model results change the decay rate by about an order of magnitude but give the same upper bound on $κ$ because the threshold energy is unchanged. The previous point-particle calculation of photon decay into an electron-positron pair for the theory with $κ<0$ remains valid, and experimental results on cosmic gamma rays provide a lower bound on $κ$ at the $-10^{-15}$ level.

hep-ph↗

arXiv2013

Search for neutrino-antineutrino oscillations with a reactor experiment

The disappearance of reactor antineutrinos in the Double Chooz experiment is used to investigate the possibility of neutrino-antineutrino oscillations arising due to the breakdown of Lorentz invariance. We find no evidence for this phenomenon and set the first limits on 15 coefficients describing neutrino-antineutrino mixing within the framework of the Standard-Model Extension.

hep-ex↗

arXiv2012

Light Sterile Neutrinos: A White Paper

This white paper addresses the hypothesis of light sterile neutrinos based on recent anomalies observed in neutrino experiments and the latest astrophysical data.

hep-ph↗