Speaker
Description
We present a search for low-mass narrow quark-antiquark resonances. This search uses data from the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS detector in Run 2, and corresponds to an integrated luminosity of 136 fb^-1. The analysis strategy makes use of an initial state photon recoiling against the narrow resonance. The resulting large transverse momentum (pT) of the resonance leads to its decay products being collimated into a single jet with internal two-pronged substructure. The new physics signal is searched for as a narrowly peaking excess above the standard model backgrounds in the jet mass spectrum. During the 2018 data taking period, a lower photon pT threshold trigger was implemented and is used in this analysis, allowing us to better probe the lower mass region. The variable N2DDT is used to identify two-pronged substructure jets, which is decorrelated with the jet’s mass and pT. An alternate method of selecting jets with two-pronged substructure using a machine learning algorithm called ParticleNet is also in development. A mostly data-driven method is used to determine the backgrounds in the analysis. A leptophobic Z’ decaying to quarks is the benchmark model used, and the analysis is further motivated by a simplified model of dark matter involving a mediator particle interacting between quarks and dark matter.
