arXiv subjects

Sheldon L. Glashow

Publications and source records attributed to Sheldon L. Glashow.

23 records · Page 2Linked to original sources

arXiv1998

"Just So" Neutrino Oscillations Are Back

Recent evidence for oscillations of atmospheric neutrinos at Super-Kamiokande suggest, in the simplest see-saw interpretation, neutrino masses such that `just so' vacuum oscillations can explain the solar neutrino deficit. Super-K solar neutrino data provide preliminary support for this interpretation. We describe how the just-so signal---an energy dependent seasonal variation of the event rate, might be detected within the coming years and provide general arguments constraining the sign of the variation. The expected variation at radiochemical detectors may be below present sensitivity, but a significant modulation in the $^7$Be signal could shed light on the physics of the solar core---including a direct measure of the solar core temperature.

hep-ph↗

arXiv1998

Evading the GZK Cosmic-Ray Cutoff

Explanations of the origin of ultra-high energy cosmic rays are severely constrained by the Greisen-Zatsepin-Kuz'min effect, which limits their propagation over cosmological distances. We argue that possible departures from strict Lorentz invariance, too small to have been detected otherwise, can affect elementary-particle kinematics so as to suppress or forbid inelastic collisions of cosmic-ray nucleons with background photons. Thereby can the GZK cutoff be relaxed or removed.

hep-ph↗

arXiv1998

Cosmological Searches for Photon Velocity Oscillations

We posit a second massless photon, uncoupled to known forms of matter but undergoing Lorentz non-invariant velocity mixing with ordinary photons. Our speculation within a speculation suffers from the sin of implausibility but enjoys the virtue of verifiability. To avoid unacceptable distortion of the well-measured microwave background spectrum, the velocity difference of the photons cannot exceed $\sim10^{-32} c$. Stronger constraints (or observable effects!) can arise from optical measurements of distant sources.

astro-ph↗

arXiv1997

Cosmic Ray and Neutrino Tests of Special Relativity

Searches for anisotropies due to Earth's motion relative to a preferred frame -- modern versions of the Michelson-Morley experiment -- provide precise verifications of special relativity. We describe other tests, independent of this motion, that are or can become even more sensitive. The existence of high-energy cosmic rays places strong constraints on Lorentz non-invariance. Furthermore, if the maximum attainable speed of a particle depends on its identity, then neutrinos, even if massless, may exhibit flavor oscillations. Velocity differences far smaller than any previously probed can produce characteristic effects at accelerators and solar neutrino experiments.

hep-ph↗

arXiv1996

Decays of a Leptophobic Gauge Boson

We discuss the theory and phenomenology of decays of a leptophobic $U(1)_\X$ gauge boson $X$, such as has been proposed to explain the alleged deviations of $R_b$ and $R_c$ from standard model predictions. If the scalars involved in the breaking of the $SU(2)\times U(1)$ symmetry are sufficiently light, $X$ will sometimes decay into a charged (or neutral) scalar along with an oppositely-charged $W$ (or $Z$). These decay modes could yield clean signals for the leptophobic gauge bosons at hadron colliders and provide an interesting window into the Higgs sector of the theory.

hep-ph↗