Search for long-lived particles decaying to jets with displaced vertices

We report the results of a search for long-lived particles produced in pairs in proton-proton collisions at the LHC operating at a center-of-mass energy of $\sqrt{s}=13~\mathrm{TeV}$. The data were collected by the CMS detector during the full Run 2 data taking period from 2015 through 2018, corresponding to a total integrated luminosity of $140~\mathrm{fb}^{-1}$. This search targets long-lived particles with a mean proper decay length between $0.1$ and $100~\mathrm{mm}$ that each decay into at least two quarks. The signature is a pair of displaced vertices each formed from many tracks. This search extends a previous CMS search using the 2015 and 2016 dataset, with improvements in background rejection, background estimation techniques, as well as uncertainty estimation. By requiring two reconstructed vertices inside the beam pipe, this search has particularly high sensitivity to decay lengths below $20~\mathrm{mm}$, which complements similar long-lived search strategies that are less sensitive to such short decay lengths. Results are compared with $R$-parity violating supersymmetry models that predict pair-produced long-lived particles, each decaying into multijet or dijet final states. No events are observed with two reconstructed high-track-multiplicity vertices. For models of long-lived pair-produced neutralinos, gluinos, and top squarks, pair-production cross sections larger than $0.08~\mathrm{fb}$ are excluded at $95\%$ confidence level for masses between $800$ and $3000~\mathrm{GeV}$ and mean proper decay lengths between $1$ and $25~\mathrm{mm}$.