Search for: All records

A bstract A search for the pair production of the lightest supersymmetric partner of the top quark, the top squark ( $$ {\overset{\sim }{\textrm{t}}}_1 $$ t ~ 1 ), is presented. The search targets the four-body decay of the $$ {\overset{\sim }{\textrm{t}}}_1 $$ t ~ 1 , which is preferred when the mass difference between the top squark and the lightest supersymmetric particle is smaller than the mass of the W boson. This decay mode consists of a bottom quark, two other fermions, and the lightest neutralino ( $$ {\overset{\sim }{\chi}}_1^0 $$ χ ~ 1 0 ), which is assumed to be the lightest supersymmetric particle. The data correspond to an integrated luminosity of 138 fb − 1 of proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC. Events are selected using the presence of a high-momentum jet, an electron or muon with low transverse momentum, and a significant missing transverse momentum. The signal is selected based on a multivariate approach that is optimized for the difference between m ( $$ {\overset{\sim }{\textrm{t}}}_1 $$ t ~ 1 ) and m ( $$ {\overset{\sim }{\chi}}_1^0 $$ χ ~ 1 0 ). The contribution from leading background processes is estimated from data. No significant excess is observed above the expectation from standard model processes. The results of this search exclude top squarks at 95% confidence level for masses up to 480 and 700 GeV for m ( $$ {\overset{\sim }{\textrm{t}}}_1 $$ t ~ 1 ) − m ( $$ {\overset{\sim }{\chi}}_1^0 $$ χ ~ 1 0 ) = 10 and 80 GeV, respectively. 

A bstract Results are presented from a search for charged-lepton flavor violating (CLFV) interactions in top quark production and decay in pp collisions at a center-of-mass energy of 13 TeV. The events are required to contain one oppositely charged electron-muon pair in the final state, along with at least one jet identified as originating from a bottom quark. The data correspond to an integrated luminosity of 138 fb − 1 , collected by the CMS experiment at the LHC. This analysis includes both the production (q → e μ t) and decay (t → e μ q) modes of the top quark through CLFV interactions, with q referring to a u or c quark. These interactions are parametrized using an effective field theory approach. With no significant excess over the standard model expectation, the results are interpreted in terms of vector-, scalar-, and tensor-like CLFV four-fermion effective interactions. Finally, observed exclusion limits are set at 95% confidence levels on the respective branching fractions of a top quark to an e μ pair and an up (charm) quark of 0 . 13 × 10 − 6 (1 . 31 × 10 − 6 ), 0 . 07 × 10 − 6 (0 . 89 × 10 − 6 ), and 0 . 25 × 10 − 6 (2 . 59 × 10 − 6 ) for vector, scalar, and tensor CLFV interactions, respectively. 

A bstract Events containing one or more top quarks produced with additional prompt leptons are used to search for new physics within the framework of an effective field theory (EFT). The data correspond to an integrated luminosity of 41.5 fb − 1 of proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC, collected by the CMS experiment in 2017. The selected events are required to have either two leptons with the same charge or more than two leptons; jets, including identified bottom quark jets, are also required, and the selected events are divided into categories based on the multiplicities of these objects. Sixteen dimension-six operators that can affect processes involving top quarks produced with additional charged leptons are considered in this analysis. Constructed to target EFT effects directly, the analysis applies a novel approach in which the observed yields are parameterized in terms of the Wilson coefficients (WCs) of the EFT operators. A simultaneous fit of the 16 WCs to the data is performed and two standard deviation confidence intervals for the WCs are extracted; the standard model expectations for the WC values are within these intervals for all of the WCs probed. 

A bstract A search for standard model Higgs bosons (H) produced with transverse momentum ( p T ) greater than 450 GeV and decaying to bottom quark-antiquark pairs ( $$ \mathrm{b}\overline{\mathrm{b}} $$ b b ¯ ) is performed using proton-proton collision data collected by the CMS experiment at the LHC at $$ \sqrt{s} $$ s = 13 TeV. The data sample corresponds to an integrated luminosity of 137 fb − 1 . The search is inclusive in the Higgs boson production mode. Highly Lorentz-boosted Higgs bosons decaying to $$ \mathrm{b}\overline{\mathrm{b}} $$ b b ¯ are reconstructed as single large-radius jets, and are identified using jet substructure and a dedicated b tagging technique based on a deep neural network. The method is validated with Z → $$ \mathrm{b}\overline{\mathrm{b}} $$ b b ¯ decays. For a Higgs boson mass of 125 GeV, an excess of events above the background assuming no Higgs boson production is observed with a local significance of 2.5 standard deviations ( σ ), while the expectation is 0.7. The corresponding signal strength and local significance with respect to the standard model expectation are μ H = 3 . 7 ± 1 . 2(stat) $$ {}_{-0.7}^{+0.8} $$ − 0.7 + 0.8 (syst) $$ {}_{-0.5}^{+0.8} $$ − 0.5 + 0.8 (theo) and 1 . 9 σ . Additionally, an unfolded differential cross section as a function of Higgs boson p T for the gluon fusion production mode is presented, assuming the other production modes occur at the expected rates.