Search for Heavy Neutral Leptons in Decays of W Bosons Using a Dilepton Displaced Vertex in sqrt[s]=13 TeV pp Collisions with the ATLAS Detector.

A search for a long-lived, heavy neutral lepton (N) in 139  fb^{-1} of sqrt[s]=13  TeV pp collision data collected by the ATLAS detector at the Large Hadron Collider is reported. The N is produced via W→Nμ or W→Ne and decays into two charged leptons and a neutrino, forming a displaced vertex. The N mass is used to discriminate between signal and background.

Observation of Collider Muon Neutrinos with the SND@LHC Experiment.

We report the direct observation of muon neutrino interactions with the SND@LHC detector at the Large Hadron Collider. A dataset of proton-proton collisions at sqrt[s]=13.6  TeV collected by SND@LHC in 2022 is used, corresponding to an integrated luminosity of 36.

Evolution of the Primordial Axial Charge across Cosmic Times.

We investigate collisional decay of the axial charge in an electron-photon plasma at temperatures 10 MeV-100 GeV. We demonstrate that the decay rate of the axial charge is first order in the fine-structure constant Γ_{flip}∝αm_{e}^{2}/T and thus orders of magnitude greater than the naive estimate which has been in use for decades. This counterintuitive result arises through infrared divergences regularized at high temperature by environmental effects.

A facility to search for hidden particles at the CERN SPS: the SHiP physics case.

This paper describes the physics case for a new fixed target facility at CERN SPS. The SHiP (search for hidden particles) experiment is intended to hunt for new physics in the largely unexplored domain of very weakly interacting particles with masses below the Fermi scale, inaccessible to the LHC experiments, and to study tau neutrino physics. The same proton beam setup can be used later to look for decays of tau-leptons with lepton flavour number non-conservation, [Formula: see text] and to search for weakly-interacting sub-GeV dark matter candidates.

Checking the Dark Matter Origin of a 3.53 keV Line with the Milky Way Center.

We detect a line at 3.539±0.011  keV in the deep exposure data set of the Galactic center region, observed with the x-ray multi-mirror mission Newton.