Search for Supersymmetry with a Compressed Mass Spectrum in Events with a Soft ? Lepton, a Highly Energetic Jet, and Large Missing Transverse Momentum in Proton-Proton Collisions at sqrt[s]=13??TeV

PubMed ID: 32058742The first search for supersymmetry in events with an experimental signature of one soft, hadronically decaying ? lepton, one energetic jet from initial-state radiation, and large transverse momentum imbalance is presented. These event signatures are consistent with direct or indirect production of scalar ? leptons (?[over ˜]) in supersymmetric models that exhibit coannihilation between the ?[over ˜] and the lightest neutralino (?[over ˜]_{1}^{0}), and that could generate the observed relic density of dark matter. The data correspond to an integrated luminosity of 77.2??fb^{-1} of proton-proton collisions at sqrt[s]=13??TeV collected with the CMS detector at the LHC in 2016 and 2017. The results are interpreted in a supersymmetric scenario with a small mass difference (?m) between the chargino (?[over ˜]_{1}^{±}) or next-to-lightest neutralino (?[over ˜]_{2}^{0}), and the ?[over ˜]_{1}^{0}. The mass of the ?[over ˜] is assumed to be the average of the ?[over ˜]_{1}^{±} and ?[over ˜]_{1}^{0} masses. The data are consistent with standard model background predictions. Upper limits at 95% confidence level are set on the sum of the ?[over ˜]_{1}^{±}, ?[over ˜]_{2}^{0}, and ?[over ˜] production cross sections for ?m(?[over ˜]_{1}^{±},?[over ˜]_{1}^{0})=50??GeV, resulting in a lower limit of 290 GeV on the mass of the ?[over ˜]_{1}^{±}, which is the most stringent to date and surpasses the bounds from the LEP experiments