hep-ex updates on arXiv.org

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On the Chudakov effect for the most probable value of high-energy electron-positron pair ionization loss in thin targets. (arXiv:2206.14247v1 [physics.acc-ph])

The ionization loss of a high-energy electron-positron pair in thin targets is considered. The analogue of the Landau distribution function is derived for this loss under the condition when the Chudakov effect of the pair ionization loss suppression is manifested. Expression for the most probable value of the pair ionization loss $E_{MP}$ is obtained. It is shown that the magnitude of Chudakov effect for $E_{MP}$ can be noticeably different from the magnitude of this effect for the restricted mean value of the pair ionization loss. The obtained results are applied to the analysis of experimental measurements of high-energy electron-positron pair ionization loss in thin silicon detectors.

Accelerator experiments check general relativity. (arXiv:1401.3720v3 [physics.gen-ph] UPDATED)

The deflection of gamma-rays in Earth's gravitational field is tested in laser Compton scattering at high energy accelerators. Within a formalism connecting the bending angle to the photon's momentum it follows that detected gamma-ray spectra are inconsistent with a deflection magnitude of 2.78 nrad, predicted by Einstein's gravity theory. Moreover, preliminary results for 13-28 GeV photons from two different laboratories show opposite - away from the beam line - deflection, amounting to 33.8-0.8 prad. These conclusions, however, are applicable only for gravitationally sterile high energy electrons. Much more subtle effects are expected if the gravitational deflection of the electrons is taken into account.

Towards Powerful Probes of Neutrino Self-Interactions in Supernovae. (arXiv:2206.12426v1 [hep-ph] CROSS LISTED)

Neutrinos remain mysterious. As an example, enhanced self-interactions ($\nu$SI), which would have broad implications, are allowed. For the high neutrino densities within core-collapse supernovae, $\nu$SI could be important, but robust observables have been lacking. We show that $\nu$SI make neutrinos form a tightly coupled fluid that expands under relativistic hydrodynamics. The outflow becomes either a burst or a steady-state wind; which occurs here is uncertain. Though the diffusive environment where neutrinos are produced may make a wind more likely, further work is needed to determine when each case is realized. In the burst-outflow case, $\nu$SI increase the duration of the neutrino signal, and even a simple analysis of SN 1987A data has powerful sensitivity. For the wind-outflow case, we outline several promising ideas that may lead to new observables. Combined, these results are important steps towards solving the 35-year-old puzzle of how $\nu$SI impact supernovae.

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