Search for supersymmetry in events with a photon, jets, b-jets, and missing transverse momentum

Abstract

Although many of the experimental observations can be theoretically well explained using the standard model (SM) of particle physics, the SM is not complete because it does not explain gravity, dark matter and dark energy in the universe, matterantimatter asymmetry, nonzero neutrino mass, observed mass of the Higgs boson being much lower than theoretically favored value etc. Supersymmetry (SUSY) is a well motivated theoretical extension of the SM which can address some of the issues in SM such as, Higgs mass problem and dark matter problem. In SUSY, every SM particle has a superpartner whose spin differs by half a unit. We have not yet observed superpartners with same masses as their SM counterparts which makes SUSY a broken symmetry. There are several theoretical mechanisms to achieve this symmetry breaking, and one of the mechanisms is gauge mediated SUSY breaking (GMSB). If GMSB is realized in nature, it typically results in events with one or more photons in the final state. A search for SUSY is presented based on events with at least one photon, jets, and large missing transverse momentum produced in protonproton collisions at a center-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 35.9 fb−1 and were recorded at the LHC with the CMS detector in 2016. The analysis characterizes signal-like events by categorizing the data into various signal regions based on the number of jets, the number of b-tagged jets, and the missing transverse momentum. No significant excess of events is observed with respect to the expectations from standard model processes. Limits are placed on the gluino and top squark pair production cross sections using several simplified models of supersymmetric particle production with GMSB scenario. Depending on the model and the mass of the next-to-lightest supersymmetric particle, the production of gluinos with masses as large as 2120 GeV and the production of top squarks with masses as large as 1230 GeV are excluded at 95% confidence level.