Physicists close in on missing piece of matter puzzle at CERN
Researchers at CERN's Large Hadron Collider searched for exotic heavy neutrinos that could explain why the universe contains more matter than antimatter. Finding none in the tested mass range doesn't solve the mystery, but it narrows where physicists should look next—important for companies building next-generation detectors and governments funding fundamental research infrastructure.
Originaltitel: Search for heavy right-handed Majorana neutrinos in the decay of top quarks produced in proton-proton collisions at â<em>s</em>=13 TeV with the ATLAS detector
<p>A search for heavy right-handed Majorana neutrinos is performed with the ATLAS detector at the CERN Large Hadron Collider, using the 140 fb(-1) of proton-proton collision data at root s = 13 TeV collected during Run 2. This search targets t (t) over bar production, in which both top quarks decay into a bottom quark and a W boson, where one of the W bosons decays hadronically and the other decays into an electron or muon and a heavy neutral lepton. The heavy neutral lepton is identified through a decay into an electron or muon and another W boson, resulting in a pair of same-charge same-flavor leptons in the final state. This paper presents the first search for heavy neutral leptons in the mass range of 15-75 GeV using t (t) over bar events. No significant excess is observed over the background expectation, and upper limits are placed on the signal cross sections. Assuming a benchmark scenario of the phenomenological type-I seesaw model, these cross section limits are then translated into upper limits on the mixing parameters of the heavy Majorana neutrino with Standard Model neutrinos.</p>