269 Search Results

A search for a Higgs boson produced in association with a W or Z boson and decaying via a soft unclustered energy pattern (SUEP) is presented. The analysis is based on proton-proton collision data corresponding to an integrated luminosity of 138fb−1 collected between 2016 and 2018 at the LHC. Final states with a leptonic W or Z boson decay associated with a high multiplicity of low-momentum charged particles are explored for the first time. The results show no significant excess over the standard model background expectation. Limits are set on the production cross section of a Higgs boson that decaysmore » to a SUEP, for a range of parameters of the SUEP model. Material is provided to facilitate further interpretation of the results.« less

Anomaly detection methods used in a recent search for new phenomena by CMS at the CERN LHC are presented. The methods use machine learning to detect anomalous jets produced in the decay of new massive particles without depending on a specific theory model. The effectiveness of these approaches in enhancing sensitivity to various simulated signal samples is studied and compared using data collected in proton–proton collisions at a center-of-mass energy of 13$${\,\textrm{TeV}}$$. In an example analysis, the capabilities of anomaly detection methods are further demonstrated by identifying large-radius jets consistent with Lorentz-boosted hadronically decaying top quarks in a model-agnostic framework.

This analysis presents an observation of the photon-fusion production of W boson pairs using the CMS detector at the LHC. The total cross section of the W$$^{+}$$W$$^{−}$$ production in photon fusion is measured using proton-proton collision data with an integrated luminosity of 138 fb$$^{−1}$$ collected with the CMS detector in 2016–2018 at a center-of-mass energy of $$ \sqrt{s}=13 $$ TeV. Events are selected in the final state with one isolated electron and one isolated muon, and no additional tracks associated with the electron-muon production vertex. The total and fiducial production cross sections are $$ {643}_{-78}^{+82} $$ fb and $$ {3.96}_{-0.51}^{+0.53}more » $$ fb, respectively, in agreement with the standard model predictions of 631 ± 126 fb and 3.87 ± 0.77 fb. This agreement enables stringent constraints on anomalous quartic gauge couplings within a dimension-8 effective field theory framework.[graphic not available: see fulltext]« less

A search is performed for dark matter produced in association with bottom quarks and a pair of electrons or muons in data collected with the CMS detector at the LHC, corresponding to 138 fb$$^{−1}$$ of integrated luminosity of proton-proton collisions at a center-of-mass energy of 13 TeV. For the first time at the LHC, the associated production of a bottom quark-antiquark pair and a new heavy neutral Higgs boson (H) that subsequently decays into a leptonically decaying Z boson and a pseudoscalar (a) is explored. The latter acts as a dark matter mediator in the context of the two Higgsmore » doublet model plus a pseudoscalar (2HDM+a). Multivariate techniques that target a wide range of mass configurations for the H and a particles are used. The observations are consistent with the expectations from standard model processes. Upper limits at 95% confidence level are set on the product of cross section and branching fraction of the new particles, ranging from 10$$^{−2}$$ pb for an H mass of 400 GeV to 10$$^{−3}$$ pb for an H mass of 2000 GeV. Constraints on the parameter space of a benchmark 2HDM+a model are derived and compared with expectations in the context of cosmological predictions.[graphic not available: see fulltext]« less

The ratio between the B$$_\mathrm{c}^+$$$$\to$$ J/$$ψ$$$τ^+ν_τ$$ and B$$_\mathrm{c}^+$$$$\to$$ J/$$ψ$$$μ^+ν_μ$$ branching fractions is measured using a data sample of proton-proton collisions collected by CMS at a center-of-mass energy of 13 TeV in the years 2016$$-$$2018 and corresponding to an integrated luminosity of 138 fb$$^{-1}$$. The J$/ψ$ meson is identified through its J$/ψ$$$$\to$$$$μ^+μ^-$ decay and the tau lepton is reconstructed in the hadronic three-prong final state. The measured ratio of branching fractions in this tau decay mode, $$\mathcal{R}^\text{had}_{\mathrm{J}/ψ}$$ = 1.04 $$_{-0.44}^{+0.50}$$, is combined with the previous analysis based on the $τ^+$$$$\to$$$$μ^+ν_μ\barν_τ$$ leptonic decay channel, leading to $$\mathcal{R}_{\mathrm{J}/ψ}$$ = 0.49 $$\pm$$ 0.26. Asmore » this result is consistent with the standard model prediction of 0.258 $$\pm$$ 0.004, no evidence of lepton flavor universality violation is found.« less

The Higgs boson (H) decay width is determined from the ratio of off- and on-shell production of H $$\to$$ WW $$\to$$ e$νμν$ using proton-proton collision data corresponding to an integrated luminosity of 138 fb$$^{-1}$$ collected at $$\sqrt{s}$$ = 13 TeV by the CMS experiment at the Large Hadron Collider. The off-shell signal strength is measured as $$μ_\text{off-shell}$$ = 1.2 $$^{+0.8}_{-0.7}$$. The Higgs boson total decay width is $$Γ_\text{H}$$ = 3.9 $$^{+2.7}_{-2.2}$$ MeV, in agreement with the standard model prediction. The uncertainty in this result represents a factor of three improvement over the previous CMS result in this decay channel.

Differential top quark pair production cross sections are measured in the dilepton final states e$$^{+}$$e$$^{−}$$, μ$$^{+}$$μ$$^{−}$$, and e$$^{±}$$μ$$^{∓}$$, as a function of kinematic variables of the two-neutrino system: the transverse momentum $$ {p}_{\textrm{T}}^{\nu \nu} $$ of the dineutrino system, the minimum distance in azimuthal angle between $$ {\overrightarrow{p}}_{\textrm{T}}^{\nu \nu} $$ and leptons, and in two dimensions in bins of both observables. The measurements are performed using CERN LHC proton-proton collisions at $$ \sqrt{s}=13 $$ TeV, recorded by the CMS detector between 2016 and 2018, corresponding to an integrated luminosity of 138 fb$$^{−1}$$. The measured cross sections are unfolded to themore » particle level using an unregularized least squares method. Results are compared with predictions by the standard model of particle physics, and found to be in agreement with theoretical calculations as well as Monte Carlo simulations.[graphic not available: see fulltext]« less

The results of a search for the production of two scalar bosons in final states with two photons and two tau leptons are presented. The search considers both nonresonant production of a Higgs boson pair, HH, and resonant production via a new boson X which decays either to HH or to H and a new scalar Y. The analysis uses up to 138 fb$$^{−1}$$ of proton-proton collision data, recorded between 2016 and 2018 by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV. No evidence for signal is found in the data. For the nonresonant production,more » the observed (expected) upper limit at 95% confidence level (CL) on the HH production cross section is set at 930 (740) fb, corresponding to 33 (26) times the standard model prediction. At 95% CL, HH production is observed (expected) to be excluded for values of κ$$_{λ}$$ outside the range between −12 (−9.4) and 17 (15). Observed (expected) upper limits at 95% CL for the X → HH cross section are found to be within 160 to 2200 (200 to 1800) fb, depending on the mass of X. In the X → Y(ττ)H(γγ) search, the observed (expected) upper limits on the product of the production cross section and decay branching fractions vary between 0.059–1.2 fb (0.087–0.68 fb). For the X → Y(γγ)H(ττ) search the observed (expected) upper limits on the product of the production cross section and Y → γγ branching fraction vary between 0.69–15 fb (0.73–8.3 fb) in the low Y mass search, tightening constraints on the next-to-minimal supersymmetric standard model, and between 0.64–10 fb (0.70–7.6 fb) in the high Y mass search.[graphic not available: see fulltext]« less

A measurement of the angular structure of inclusive jets and those containing a prompt D$$^{0}$$ meson in proton-proton collisions at the LHC at a center-of-mass energy of 5.02 TeV is presented. The data corresponding to an integrated luminosity of 301 pb$$^{−1}$$ were collected by the CMS experiment in 2017. Two jet grooming algorithms, late-k$$_{T}$$ and soft drop, are used to study the intrajet radiation pattern using iterative Cambridge-Aachen declustering. The splitting-angle distributions of jets with transverse momentum (p$$_{T}$$) of around 100 GeV, obtained with these two algorithms, show that there is a shift of the distribution for jets containing amore » prompt D$$^{0}$$ meson with respect to inclusive jets. The suppression of emissions at small angles observed in the late-k$$_{T}$$ grooming approach is consistent with the dead-cone effect, whereas the similar suppression for splittings selected with the soft-drop algorithm appears to be induced by gluon splitting to charm quark-antiquark pairs at large angles. The measured distributions are corrected to the particle level and can be used to constrain model predictions for the substructure of high-p$$_{T}$$ charm quark jets.[graphic not available: see fulltext]« less

A search for heavy long-lived charged particles at the LHC is presented. Particles interacting with the CMS muon detector across several bunch crossings are searched for using a data sample of proton-proton collisions at $$\sqrt{s}$$ = 13.6 TeV collected with the CMS detector in 2024, corresponding to an integrated luminosity of 3.7 fb$$^{-1}$$. This is the first search relying on the novel level-1 trigger scouting data set collected without any trigger selection, allowing correlations between bunch crossings to be analyzed. The results are interpreted as upper limits on the cross sections of several benchmark processes with pair production of heavymore » long-lived charged particles. Upper limits on the fiducial cross section of a heavy long-lived charged particle with $$p_\mathrm{T}$$$$\gt$$ 500 GeV and $$\lvertη\rvert$$$$\lt$$ 0.83 are also set in different ranges of $β=v/c$. This analysis is a crucial proof of concept for the level-1 trigger data scouting system and complements existing searches for heavy long-lived charged particles by extending the sensitivity to lower $$β$$ values.« less