Abstract
Results are reported from a search for long-lived particles in proton-proton collisions at $\sqrt{s} =$ 13 TeV delivered by the CERN LHC and collected by the CMS experiment. The data sample, which was recorded during 2015 and 2016, corresponds to an integrated luminosity of 38.5 fb$^{-1}$. This search uses benchmark signal models in which long-lived particles are pair-produced and each decays into two or more quarks, leading to a signal with multiple jets and two displaced vertices composed of many tracks. No events with two well-separated high-track-multiplicity vertices are observed. Upper limits are placed on models of $R$-parity violating supersymmetry in which the long-lived particles are neutralinos or gluinos decaying solely into multijet final states or top squarks decaying solely into dijet final states. For neutralino, gluino, or top squark masses between 800 and 2600 GeV and mean proper decay lengths between 1 and 40 mm, the analysis excludes cross sections above 0.3 fb at 95% confidence level. Gluino and top squark masses are excluded below 2200 and 1400 GeV, respectively, for mean proper decay lengths between 0.6 and 80 mm. A method is provided for extending the results to other models with pair-produced long-lived particles.
Highlights
Many theories for physics beyond the standard model (SM) predict the pair production of long-lived particles decaying to final states with two or more jets
The “dijet” benchmark signal corresponds to an R-parity violating (RPV) phenomenological model in which pair-produced long-lived top squarks each decay into two down antiquarks [6]
We focus on signals with intermediate lifetimes, corresponding to mean proper decay lengths cτ from 0.1 to 100 mm, by identifying vertices that are displaced from the beam axis but within the radius of the beam pipe
Summary
Many theories for physics beyond the standard model (SM) predict the pair production of long-lived particles decaying to final states with two or more jets. This analysis is sensitive to models of new physics in which pairs of long-lived particles decay to final states with multiple charged particles. The “dijet” benchmark signal corresponds to an RPV phenomenological model in which pair-produced long-lived top squarks each decay into two down antiquarks [6]. The experimental signature of long-lived exotic particle pairs is two displaced vertices, each consisting of multiple charged-particle trajectories intersecting at a single point. In this analysis, a custom vertex reconstruction algorithm identifies displaced vertices in the CMS detector. The analysis reported here is sensitive to shorter lifetimes than those probed by previous analyses
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
