A search for light pair-produced resonances decaying into at least four quarks

Results are presented of a search for light pair-produced particles that each decay into at least four quarks, targeting particles with masses above $100~\mathrm{GeV}$. The representative signal model is a supersymmetric quark that decays into four quarks through an intermediate Higgsino with a hadronic $R$-parity-violating coupling. Using $38.2~\mathrm{fb}^{-1}$ of data collected by the CMS experiment at the LHC from 2015 to 2016 with proton-proton collisions at a center-of-mass energy $\sqrt{s}=13~\mathrm{TeV}$, reconstructed particles are clustered into two jets with large radius and high transverse momentum, each consistent with four-parton substructure and with similar mass. A novel, data-driven technique is used to estimate the dominant QCD multijet event background. Background contributions from top-quark decays are also taken into account and additionally serve for the calibration of systematic uncertainties. No statistically significant excess is observed, and the production of supersymmetric quark pairs and supersymmetric gluon pairs with masses below $721~\mathrm{GeV}$ and $1.0~\mathrm{TeV}$, respectively, are excluded at the $95\%$ confidence level.