Search for nonresonant new physics signals in high-mass dilepton events produced in association with b-tagged jets in proton-proton collisions at $\sqrt{s}$ = 13 TeV

The CMS collaboration
Chekhovsky, Vladimir , Hayrapetyan, Aram , Makarenko, Vladimir , Tumasyan, Armen , Adam, Wolfgang , Andrejkovic, Janik Walter , Benato, Lisa , Bergauer, Thomas , Damanakis, Konstantinos , Dragicevic, Marko
CMS-EXO-23-010, 2025.

Abstract (data abstract)
A search for nonresonant new physics phenomena in high-mass dilepton events produced in association with b-tagged jets is performed using Run~2 proton-proton collisions data collected by the CMS experiment at the CERN LHC, at a center-of-mass energy of 13\TeV, corresponding to an integrated luminosity of 138\fbinv. The analysis considers two effective field theory models with dimension-six operators; involving four-fermion contact interactions between two leptons ($\Pell\Pell$, electrons or muons) and $\PQb$ or $\PQs$ quarks (\bbll and \bsll). Two lepton flavor combinations ($\Pe\Pe$ and $\PGm\PGm$) are required and events are classified as having 0, 1, and $\ge2$ b-tagged jets in the final state. No significant excess is observed over the standard model backgrounds. Upper limits are set on the product of production cross section of the new physics signals. These translate into lower limits on the energy scale $\Lambda$ of 6.9 to 9.0\TeV in the \bbll model, depending on model parameters, and on the ratio of energy scale and coupling of the underlying physics, \lamdagstar of 2.0 to 2.6\TeV in the \bsll model. The latter represent the most stringent limits on this model to date. Lepton flavor universality is also tested by comparing the dielectron and dimuon mass spectra for different $\PQb$-tagged jet multiplicities. No significant deviation from the standard model expectation of unity is observed.

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