Massive LHC experiment finds no dark matter—yet narrows where it could hide
Scientists at CERN's Large Hadron Collider searched for dark matter particles produced alongside bottom quarks but found nothing—a null result that nonetheless constrains where dark matter can exist. The findings eliminate vast swaths of theoretical parameter space, forcing physicists to refine models and potentially redirect billion-dollar detector upgrades.
Originaltitel: Search for dark matter production in association with bottom quarks and a lepton pair in proton-proton collisions at √s = 13TeV
<p>A search is performed for dark matter produced in association with bottom quarks and a pair of electrons or muons in data collected with the CMS detector at the LHC, corresponding to 138 fb−1 of integrated luminosity of proton-proton collisions at a center-of-mass energy of 13 TeV. For the first time at the LHC, the associated production of a bottom quark-antiquark pair and a new heavy neutral Higgs boson (H) that subsequently decays into a leptonically decaying Z boson and a pseudoscalar (a) is explored. The latter acts as a dark matter mediator in the context of the two Higgs doublet model plus a pseudoscalar (2HDM+a). Multivariate techniques that target a wide range of mass configurations for the H and a particles are used. The observations are consistent with the expectations from standard model processes. Upper limits at 95% confidence level are set on the product of cross section and branching fraction of the new particles, ranging from 10−2 pb for an H mass of 400 GeV to 10−3 pb for an H mass of 2000 GeV. Constraints on the parameter space of a benchmark 2HDM+a model are derived and compared with expectations in the context of cosmological predictions.</p>