Abstract
The results of a previous search by the CMS Collaboration for squarks and gluinos are reinterpreted to constrain models of leptoquark (LQ) production. The search considers jets in association with a transverse momentum imbalance, using the $M_\mathrm{T2}$ variable. The analysis uses proton-proton collision data at $\sqrt{s}=$ 13 TeV, recorded with the CMS detector at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Leptoquark pair production is considered with LQ decays to a neutrino and a top, bottom, or light quark. This reinterpretation considers higher mass values than the original CMS search to constrain both scalar and vector LQs. Limits on the cross section for LQ pair production are derived at the 95% confidence level depending on the LQ decay mode. A vector LQ decaying with a 50% branching fraction to t$\nu$, and 50% to b$\tau$, has been proposed as part of an explanation of anomalous flavor physics results. In such a model, using only the decays to t$\nu$, LQ masses below 1530 GeV are excluded assuming the Yang--Mills case with coupling $\kappa =$ 1, or 1115 GeV in the minimal coupling case $\kappa =$ 0, placing the most stringent constraint to date from pair production of vector LQs.
Highlights
Leptoquarks (LQ) are hypothetical particles with quantum numbers of both quarks and leptons [1]
Using the full analysis information including all signal regions and correlations, we extend the interpretations from Ref. [58] to higher mass values, allowing us to improve the upper limits on LQ pair production cross sections in the tν decay channel by as much as a factor of 2.8 over the flat extrapolation assumed in Ref. [39]
The standard model (SM) backgrounds to the search comprise three classes of processes: Z þ jets production with the decay Z → νν, W þ jets or tt þ jets production with the decay W → lν where the charged lepton is outside the acceptance or not identified (“lost lepton”), and quantum chromodynamics (QCD) multijet production where p⃗ mT iss arises from jet mismeasurement
Summary
Leptoquarks (LQ) are hypothetical particles with quantum numbers of both quarks and leptons [1]. Constraints on LQ production with decays to a quark and a neutrino have been placed using LHC data by the ATLAS [40] and CMS [41,42,43] Collaborations, either by reinterpreting existing squark searches, or considering mixed branching fraction scenarios with an LQ decaying to a quark and a charged lepton. For an LQV decaying to tν as predicted to explain the flavor physics anomalies, the mass limit was derived from a flat extrapolation assuming that the cross section limit stayed the same at higher masses To improve upon these constraints, in this paper we present an extended interpretation of the search from Ref. We derive the strongest coupling-independent constraints to date on the anomaly-inspired model of Refs. [37,38]
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