Physicists Hunt for Exotic Particles That Could Rewrite Fundamental Physics
Scientists at CERN's Large Hadron Collider searched for hypothetical heavy particles that could explain mysteries beyond current physics—but found no definitive evidence. The null result still matters: it narrows where these particles could hide, accelerating the hunt for new physics that could eventually reshape technology and materials science.
Originaltitel: Search for heavy pseudoscalar and scalar bosons decaying to a top quark pair in proton–proton collisions at √s = 13 TeV
<p>A search for pseudoscalar or scalar bosons decaying to a top quark pair (t¯ t) in final states with one or two charged leptons is presented. The analyzed proton–proton collision data was recorded at √s = 13TeV by the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 138fb−1. The invariant mass mt¯ t of the reconstructed t¯ t system and variables sensitive to its spin and parity are used to discriminate against the standard model t¯ t background. Interference between pseudoscalar or scalar boson production and the standard model t¯ t continuum is included, leading to peak-dip structures in the mt¯ t distribution. An excess of the data above the background prediction, based on perturbative quantum chromodynamics (QCD) calculations, is observed near the kinematic t¯ t production threshold, while good agreement is found for high mt¯ t. The data are consistent with the background prediction if the contribution from a simplified model of a color-singlet 1S[1]0 t¯ t quasi-bound state ηt, inspired by nonrelativistic QCD, is added. Upper limits at 95% confidence level are set on the coupling between the pseudoscalar or scalar bosons and the top quark for boson masses in the range 365–1000GeV, relative widths between 0.5% and 25%, and two background scenarios with or without ηt contribution.</p>