Abstract
Two related searches for phenomena beyond the standard model (BSM) are performed using events with hadronic jets and significant transverse momentum imbalance. The results are based on a sample of proton–proton collisions at a center-of-mass energy of 13,text {Te}text {V} , collected by the CMS experiment at the LHC in 2016–2018 and corresponding to an integrated luminosity of 137,text {fb}^{-1}. The first search is inclusive, based on signal regions defined by the hadronic energy in the event, the jet multiplicity, the number of jets identified as originating from bottom quarks, and the value of the kinematic variable M_{mathrm {T2}} for events with at least two jets. For events with exactly one jet, the transverse momentum of the jet is used instead. The second search looks in addition for disappearing tracks produced by BSM long-lived charged particles that decay within the volume of the tracking detector. No excess event yield is observed above the predicted standard model background. This is used to constrain a range of BSM models that predict the following: the pair production of gluinos and squarks in the context of supersymmetry models conserving R-parity, with or without intermediate long-lived charginos produced in the decay chain; the resonant production of a colored scalar state decaying to a massive Dirac fermion and a quark; or the pair production of scalar and vector leptoquarks each decaying to a neutrino and a top, bottom, or light-flavor quark. In most of the cases, the results obtained are the most stringent constraints to date.
Highlights
Background estimation4.1 Inclusive MT2 searchThe backgrounds in jets-plus- pTmiss final states arise from three categories of standard model (SM) processes. The lost-lepton (LL) background: events with a lepton from a W boson decay where the lepton is either out of acceptance, not reconstructed, not identified, or not isolated
Some theoretical models [13,14] predict the existence of long-lived charged particles that can be identified as disappearing tracks, when they decay within the volume of the tracking detector and their charged decay products are below the pT detection threshold
The background estimates and corresponding uncertainties rely exclusively on the inputs from control samples and simulation described in Sect. 4.1, prior to the fit to the data detailed in Sect. 6, and are referred to in the rest of the text as pre-fit background results
Summary
2016–2018, and corresponding to an integrated luminosity of 137 fb−1. The first is an inclusive search that exploits the transverse momentum imbalance as inferred from the kinematic variable MT2 [1], defined in Sect. 3.1, in events with at least two hadronic jets, or the transverse momentum ( pT) of the jet in events with just one jet. The second search aims at extending the sensitivity of the inclusive search for scenarios where the mass spectrum of potential new particles is compressed In such scenarios, some theoretical models [13,14] predict the existence of long-lived charged particles that can be identified as disappearing tracks, when they decay within the volume of the tracking detector and their charged decay products are below the pT detection threshold. Some theoretical models [13,14] predict the existence of long-lived charged particles that can be identified as disappearing tracks, when they decay within the volume of the tracking detector and their charged decay products are below the pT detection threshold Such signatures are rare in the SM and are often dominated by instrumental effects. Event counts in bins of Nj, HT, disappearing track length, and disappearing track pT are compared against estimates of the background from SM processes derived from dedicated data control samples
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