arXiv subjects

CMS Collaboration

Publications and source records attributed to CMS Collaboration.

At least 19 recordsLinked to original sources

arXiv2026

Search for resonant production of pairs of dijet resonances through broad mediators in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A reinterpretation of a prior narrow-resonance search is performed to investigate the resonant production of pairs of dijet resonances via broad mediators. This analysis targets events with four resolved jets, requiring dijet invariant masses greater than 0.2 TeV and four-jet invariant masses greater than 1.6 TeV. The search uses a data sample corresponding to an integrated luminosity of 138 fb$^{-1}$ collected by the CMS experiment in proton-proton collisions at $\sqrt{s}$ = 13 TeV. The reinterpretation considers the production of new heavy four-jet resonances, with widths ranging from 1.5 to 10% of their mass, which decay to a pair of dijet resonances. This analysis probes resonant production in the four-jet and dijet mass distributions. Upper limits at 95% confidence level and significances are reported on the production cross section of new resonances as functions of their widths and masses, between 2 and 10 TeV. In particular, at a four-jet resonance mass of 8.6 TeV, the local (global) significance ranges from 3.9 (1.6) to 3.6 (1.4) standard deviations (s.d.) as the resonance width is increased from 1.5 to 10%. This relative insensitivity to the choice of width indicates that a broad resonance is an equally valid interpretation of this excess. The broad resonance hypothesis at a resonance mass of 8.6 TeV is supported by the presence of an event with a four-jet mass of 5.8 TeV and an average dijet mass of 2.0 TeV. Also, we report the reinterpretation of a second effect, at a four-jet resonance mass of 3.6 TeV, which has a local (global) significance of up to 3.9 (2.2) s.d.

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arXiv2026

Search for new physics using single-lepton events with high multiplicities of jets and b jets in proton-proton collisions at $\sqrt{s}$ = 13 TeV

This paper presents a search for beyond the standard model physics using single-lepton events with a high multiplicity of jets, including those identified as bottom quark jets, without a requirement on missing transverse momentum. The analysis is based on proton-proton collision data collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. This search is sensitive to $R$-parity violating supersymmetry models, where supersymmetric particles can decay into standard-model particles through interactions that violate baryon number conservation. In particular, the signal model considered is gluino pair production, where each gluino decays into top, bottom, and strange quarks. The sum of large-radius jet masses is used to distinguish the signal from background, as it effectively captures the features of high jet multiplicity and high interaction energy. No significant excess of data over the background predictions is observed. Gluinos in this model have been excluded for masses below 1890 GeV at 95% confidence level.

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arXiv2026

Search for nonresonant production of strongly coupled dark matter in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search is presented for semivisible jets produced in nonresonant processes, using proton-proton collision data at $\sqrt{s}$ = 13 TeV, collected with the CMS detector at the CERN LHC and corresponding to an integrated luminosity of 138 fb$^{-1}$. These jets, containing both visible and invisible particles, would indicate the presence of dark matter arising from a strongly coupled hidden sector. The signal model includes a bifundamental scalar that couples simultaneously to standard model quarks and dark-sector quarks, the latter forming semivisible jets. The final state therefore includes missing transverse momentum aligned with a jet, rather than recoiling against standard model particles as typically required by conventional collider dark-matter searches. Two separate machine-learning strategies are employed to identify semivisible jets: a supervised graph neural network and an unsupervised autoencoder. No significant excess corresponding to dark-sector signal hypotheses is observed. Upper limits at 95% confidence level on the signal production cross section are determined for each strategy and interpreted as exclusions in the signal model parameter space. The supervised search excludes mediator masses between 0.5 and 2.4 TeV, depending on the other signal model parameters. For signal models with semivisible jets containing higher fractions of stable dark-matter particles, the unsupervised search demonstrates increased sensitivity with 5 (11)% higher expected (observed) mediator mass exclusions than the supervised search.

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arXiv2026

Measurement of the Z$γ$ production cross section and search for anomalous neutral triple gauge couplings in pp collisions at $\sqrt{s}$ = 13 TeV

A measurement of the fiducial cross section of the associated production of a Z boson and a high-$p_\mathrm{T}$ photon, where the Z decays to two neutrinos, and a search for anomalous triple gauge couplings are reported. The results are based on data collected by the CMS experiment at the LHC in proton-proton collisions at $\sqrt{s}$ = 13 TeV during 2016$-$2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The fiducial Z$γ$ cross section, where a photon with a $p_\mathrm{T}$ greater than 225 GeV is produced in association with a Z, and the Z decays to a $ν\barν$ pair (Z($ν\barν$)$γ$), is measured to be 23.3 $^{+1.4}_{-1.3}$ fb, in agreement, within uncertainties, with the standard model prediction. The differential cross section as a function of the photon $p_\mathrm{T}$ has been measured and compared with standard model predictions computed at next-to-leading and at next-to-next-to-leading order in perturbative quantum chromodynamics. Constraints have been placed on the presence of anomalous couplings that affect the ZZ$γ$ and Z$γγ$ vertex using the $p_\mathrm{T}$ spectrum of the photons. The observed 95% confidence level intervals for $CP$-conserving $h_3^γ$ and $h_4^γ$ are determined to be ($-$3.4, 3.5) $\times$ 10$^{-4}$ and ($-$6.8, 6.8) $\times$ 10$^{-7}$, and for $h_3^\mathrm{Z}$ and $h_4^\mathrm{Z}$ they are ($-$2.2, 2.2) $\times$ 10$^{-4}$ and ($-$4.1, 4.2) $\times$ 10$^{-7}$, respectively. These are the strictest limits to date on $h_3^γ$, $h_3^\mathrm{Z}$ and $h_4^\mathrm{Z}$.

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arXiv2026

Particle transformers for identifying Lorentz-boosted Higgs bosons decaying to a pair of W bosons

A novel deep neural network classifier, a ``Particle transformer'' (PaRT), is introduced for the identification of highly Lorentz-boosted resonances reconstructed as single, multipronged jets in measurements and searches performed by the CMS Collaboration at the CERN LHC. Based on a self-attention mechanism that allows the model to weigh the importance of different particles, PaRT is trained on a wide variety of topologies, notably demonstrating strong performance for the first time on jets originating from boosted Higgs boson decays to W bosons. The PaRT algorithm achieves a tagging efficiency of more than 50% for such jets at a background efficiency of 1%, while maintaining decorrelation from the jet mass. A calibration is performed in proton-proton collision data collected by CMS at a center-of-mass energy of 13 TeV, with a data set corresponding to a total luminosity of 138 fb$^{-1}$. Data-to-simulation selection efficiency scale factors are measured to be in the 0.9$-$1.0 range, with relative uncertainties between 7 and 23%. The tagging capability of PaRT enhances the sensitivity of standard model measurements and searches for beyond-the-standard-model resonances decaying to hadronic diboson systems.

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arXiv2026

Analysis of the $C\!P$ structure of the Yukawa coupling between the Higgs boson and tau leptons in proton-proton collisions at $\sqrt{s}$ = 13.6 TeV

This paper presents a measurement of the charge-parity ($C\!P$) structure of the Yukawa coupling between the Higgs boson (H) and tau leptons, using proton-proton collision data at $\sqrt{s}$ = 13.6 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 62.4 fb$^{-1}$. Angular correlations between the decay products of tau leptons produced in H $\to$ $ττ$ decays are exploited to constrain the effective $C\!P$ mixing angle $α^{\mathrm{H}ττ}$, which parameterizes the admixture of scalar and pseudoscalar couplings. The mixing angle is measured to be $α^{\mathrm{H}ττ}$ = (36 $^{+33}_{-30}$)$^\circ$, compared with an expected value of (0 $\pm$ 19)$^\circ$ under the standard model hypothesis. When combined with the previous CMS measurement using data collected at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$, the mixing angle is determined to be (7 $\pm$ 16)$^\circ$, with an expected value of (0 $\pm$ 14)$^\circ$. This result represents the most precise measurement by CMS of the $C\!P$ nature of the Higgs boson coupling to tau leptons, with an expected precision that is the best achieved by any experiment to date.

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arXiv2026

Search for resonant and nonresonant production of pairs of dijet resonances in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search for pairs of dijet resonances with the same mass is conducted in final states with at least four jets. Results are presented separately for the case where the four jet production proceeds via an intermediate resonant state and for nonresonant production. The search uses a data sample corresponding to an integrated luminosity of 138 fb$^{-1}$ collected by the CMS detector in proton-proton collisions at $\sqrt{s}$ = 13 TeV. Model-independent limits, at 95% confidence level, are reported on the production cross section of four-jet and dijet resonances. These first LHC limits on resonant pair production of dijet resonances via high mass intermediate states are applied to a signal model of diquarks that decay into pairs of vector-like quarks, excluding diquark masses below 7.6 TeV for a particular model scenario. There are two events in the tails of the distributions, each with a four-jet mass of 8 TeV and an average dijet mass of 2 TeV, resulting in local and global significances of 3.9 and 1.6 standard deviations, respectively, if interpreted as a signal. The nonresonant search excludes pair production of top squarks with masses between 0.50 TeV to 0.77 TeV, with the exception of a small interval between 0.52 and 0.58 TeV, for supersymmetric $R$-parity-violating decays to quark pairs, significantly extending previous limits. Here, the most significant excess above the predicted background occurs at an average dijet mass of 0.95 TeV, for which the local and global significances are 3.6 and 2.5 standard deviations, respectively.

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arXiv2026

Measurement of the Z $\to$ $μ^+μ^-$ angular coefficients in pp collisions at $\sqrt{s}$ = 13 TeV as functions of transverse momentum and rapidity

A measurement of the eight angular polarization coefficients, $A_0$ to $A_7$, in the cross section for the Drell$-$Yan production of two muons is presented. The analysis is based on proton-proton (pp) collision data recorded with the CMS detector at the LHC at a center-of-mass energy of $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 140 fb$^{-1}$. The coefficients are determined double differentially in eight intervals of transverse momentum and two intervals of rapidity of the muon pair $μ^+μ^-$. The results are presented for the $μ^+μ^-$ invariant mass range 81$-$101 GeV and are compared with theoretical predictions calculated at next-to-next-to-leading order in perturbative quantum chromodynamics. The measurement provides relevant information about the underlying partonic dynamics and the Z boson production mechanisms.

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arXiv2026

Measurement of dijet angular distributions and search for beyond the standard model physics in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A measurement is presented of dijet angular distributions in proton-proton collisions at $\sqrt{s}$ = 13 TeV, using data collected with the CMS detector at the CERN LHC and corresponding to an integrated luminosity of 138 fb$^{-1}$. For the first time, the dijet angular distributions, corrected for detector effects, are compared with the predictions of perturbative quantum chromodynamics at next-to-next-to-leading order, including next-to-leading-order electroweak corrections. While data are generally found to be in agreement with predictions, a small difference in shape of the normalized distributions is seen for dijet masses ranging from 2.4 to 4.8 TeV and above 6 TeV. The distributions are used to search for proposed signatures of quark compositeness, extra spatial dimensions, quantum black holes, dark-matter mediators, axion-like particles, and anomalous gluon couplings. The most stringent limits to date are set for most of these scenarios. Quark contact interactions are excluded at 95% confidence level (CL) up to a scale of 17 (37) TeV for destructive (constructive) interference in a benchmark scenario, valid to next-to-leading order in quantum chromodynamics, and in which only left-handed quarks participate. The coupling of axion-like particles to the gluon, $c_{\text{g}}/f_{\text{a}}$, is constrained to be lower than 0.42 TeV$^{-1}$ at 95% CL. The anomalous triple-gluon coupling, $C_{\text{G}}/Λ^2$, in a standard model effective field theory is constrained to be lower than 0.0076 TeV$^{-2}$ at 95% CL.

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arXiv2026

Observation of $Υ$(1S) + Z associated production and measurement of the effective double-parton scattering cross section in proton-proton collisions at $\sqrt{s}$ = 13 TeV

The observation of associated production of an $Υ$(1S) meson with a Z boson and a measurement of the ratio of its fiducial cross section to the fiducial cross section of the Z boson are presented. Both the $Υ$(1S) meson and the Z boson are identified via decays into a pair of opposite-sign muons. The analysis is based on proton-proton (pp) collision data at $\sqrt{s}$ = 13 TeV, collected with the CMS detector in 2016$-$2018 and corresponding to an integrated luminosity of 138 fb$^{-1}$. Using the production of the Z boson decaying into four muons as a normalization channel, the ratio of the fiducial cross sections $σ$(pp $\to$ Z $+$ $Υ$(1S))$\mathcal{B}$(Z $\to$ $μ^+μ^-$)$\mathcal{B}$($Υ$(1S) $\to$ $μ^+μ^-$ ) to $σ$(pp $\to$ Z)$\mathcal{B}$(Z $\to$ 4$μ$) is measured to be $\mathcal{R}_{\mathrm{Z+Υ}\mathrm{(1S)}}$ = (21.1 $\pm$ 55 (stat) $\pm$ 0.6 (syst) $\times$ 10$^{-3}$), where stat and syst denote the statistical and systematic uncertainties, respectively. The result is used to extract the effective double-parton scattering cross section $σ_\text{eff}$ = 13.0 $^{+7.7}_{-3.4}$ mb. In addition, for the first time, $σ_\text{eff}$ is measured in bins of the transverse momentum of the $Υ$(1S) meson or of the Z boson.

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arXiv2026

Search for single production of a vector-like B' quark decaying to a top quark and a W boson in the single-lepton final state in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search is presented for the single production of a narrow-width vector-like B' quark that decays to a t quark and a W boson. This search targets a single-lepton final state, where a muon or electron originates either from the semileptonic decay of the t quark or from the leptonic decay of the W boson, with the other particle decaying hadronically. The (semi-)leptonic portion of the event is reconstructed from an electron or muon, missing transverse momentum, and a small-radius jet identified as a b quark jet if the muon or electron originates from the t quark. The hadronic portion of the event is reconstructed as a single large-radius jet. The originating particle of the large-radius jet is identified using a neural-network-based tagger, and the dominant background contributions are modeled from data using a neural autoregressive flow network. The data were collected from 2016 to 2018 by the CMS experiment at the LHC in proton-proton collisions at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. This search is the most sensitive to date to the production of single narrow-width B' quarks. It excludes electroweak-singlet B' quarks with $Γ/m_\mathrm{B'}$ = 5% for masses between 0.8 and 1.23 TeV. Limits are also placed on the production cross section of single B' quarks produced in association with t quarks, and on the coupling factor of the B' quark to electroweak bosons.

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arXiv2026

A machine-learning method for the estimation of the background from jets misidentified as hadronic tau lepton decays

Backgrounds arising from quark- and gluon-initiated jets misidentified as hadronically decaying tau leptons constitute a major experimental challenge for analyses involving tau leptons. The MUltivariate Fake-Factor INference (MUFFIN) approach, a machine-learning-based method for estimating this background directly from observed events, is presented. Boosted decision tree reweighting is used to learn multidimensional, per-object correction factors directly from observed data, thereby modelling the jet to hadronic tau lepton misidentification probability across the kinematic and topological phase space without relying on low-dimensional parametrisations. Performance studies are presented using proton-proton collision data collected by the CMS experiment at the CERN LHC at $\sqrt{s}$ = 13.6 TeV, corresponding to an integrated luminosity of 62.4 fb$^{-1}$. Compared to low-dimensional parametrisation methods, improved modelling of key kinematic observables is achieved, particularly in regions of high $p_\mathrm{T}$. The improved modelling leads to a reduction of up to 70% in the systematic uncertainty associated with jets being misidentified as hadronically decaying tau leptons. The MUFFIN method provides a robust and scalable method for background estimation in precision measurements and searches for beyond-the-standard-model physics involving tau lepton final states.

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arXiv2026

Measurement of event shape variables using charged particles inside jets in proton-proton collisions at $\sqrt{s}$ = 13 TeV

Event shape variables, constructed from the four-momenta of the final-state objects in an event, are sensitive to the predictions of quantum chromodynamics in multijet production. A measurement of five event shape variables is presented, using proton-proton collision data collected at a centre-of-mass energy of 13 TeV with the CMS detector during 2016$-$2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The variables are evaluated using the charged particles inside jets. After correcting for detector effects, their distributions are compared with the predictions from several models for multijet production. Overall, there is general agreement between several theoretical predictions and the data with scope for improvement of our understanding of QCD at different energy scales.

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arXiv2026

Search for charged Higgs bosons decaying into top and bottom quarks in lepton+jets final states in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search is presented for charged Higgs bosons (H$^\pm$) in proton-proton (pp) collision events via the pp $\to$ (b)H$^\pm$ processes, with H$^\pm$ decaying into top (t) and bottom (b) quarks. The search targets final states with one lepton, missing transverse momentum, and two or more b jets. The analysis is based on data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb$^{-1}$. We search for charged Higgs bosons in the 200 GeV to 1 TeV mass range. The results are interpreted within the generalized two-Higgs-doublet model (g2HDM). This model predicts additional Yukawa couplings of the Higgs bosons to the top quark $ρ_\mathrm{tt}$, the top and charm quark $ρ_\mathrm{tc}$, and the top and up quark $ρ_\mathrm{tu}$. This search focuses on the real components of $ρ_\mathrm{tt}$ and $ρ_\mathrm{tc}$, which are probed up to values of unity. An excess is observed with respect to the standard model expectation with a local significance of 2.4 standard deviations for a signal with an H$^\pm$ boson mass ($m_{\mathrm{H}^\pm}$) of 600 GeV. Limits are derived on the product of the cross section $σ$(pp $\to$ (b)H$^\pm$) and branching fraction $\mathcal{B}$(H$^\pm$ $\to$ tb, t $\to$ b$\ellν$), where $\ell$ = e, $μ$. The values of $ρ_\mathrm{tc} \gtrsim$ 0.11$-$0.38 are excluded at 95% confidence level, depending on the $m_{\mathrm{H}^\pm}$ and $ρ_\mathrm{tt}$ assumptions. The results represent the first search for charged Higgs bosons within the g2HDM framework and complement the existing results on additional neutral Higgs bosons performed on the same-sign top quark pair, three top quark, or four top quark pair final states, constraining extra Yukawa couplings for the neutral Higgs boson below the TeV scale.

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arXiv2026

Search for single vector-like quark production in opposite-sign dilepton final states in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search is presented for single production of a vector-like top quark T, decaying into the standard model top quark and Higgs boson, in a final state including two opposite-sign leptons (electrons or muons), jets, and missing transverse momentum. The data were recorded by the CMS experiment in proton-proton collisions at a center-of-mass energy of 13 TeV at the CERN LHC in the years 2016$-$2018, and corresponding to an integrated luminosity of up to 138 fb$^{-1}$. No excess in data over the background expectations is observed. Upper limits at 95% confidence level on the product of the T production cross section and its decay branching fraction to tH are set. The observed limits are 2.0 pb at a T mass 600 GeV and 0.3 pb at $M_\mathrm{T}$ = 1200 GeV, with a minimum of 0.1 pb at $M_\mathrm{T}$ = 1000 GeV. This is the first search for single vector-like T quark production, followed by a decay to a top quark and the Higgs boson, in opposite-sign dilepton final states.

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arXiv2026

Search for a new heavy scalar resonance decaying to a pair of Z bosons in the four-lepton final state in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search for a new heavy scalar resonance decaying to two Z bosons, each subsequently decaying to a pair of electrons or muons, is presented. The results are based on a proton-proton collision data set collected by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. The search is performed over a wide range of resonance masses from 130 GeV to 3 TeV, considering both narrow- and broad-width scenarios, and considering the gluon fusion and vector boson fusion production processes. For the broad-width scenario, the interference between the new resonance, the 125 GeV Higgs boson production, and the continuum background is taken into account. No significant excess with respect to the standard model background expectation is observed in the examined phase space. Upper limits at the 95% confidence level are set on the product of the heavy scalar resonance production cross section and the branching fraction for its decay into two Z bosons. The exclusion limits range from 0.05$-$0.1 pb in the low-mass region to 0.005 pb in the high-mass region.

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arXiv2026

Combination of vector boson scattering measurements in leptonic final states in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A statistical combination of vector boson scattering measurements in proton-proton collisions at $\sqrt{s}$ = 13 TeV is presented. The analysis is based on a dataset corresponding to an integrated luminosity of 138 fb$^{-1}$, collected with the CMS detector in 2016$-$2018. Events are selected to contain two vector bosons, with at least one decaying leptonically, and at least two additional jets with a high invariant mass and a large pseudorapidity separation. Signal rates are extracted for same-sign WW, opposite-sign WW, as well as for WZ and ZZ channels, and are compared with the standard model predictions. The combination provides a global view of vector boson scattering by simultaneously constraining all channels in a coherent framework, improving sensitivity beyond individual inputs, with all results in agreement with the standard model predictions. In addition, a charge-separated measurement is performed in which W bosons are distinguished according to their electric charge, allowing sensitivity to the production charge asymmetry.

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arXiv2026

Simultaneous measurements of $N$-subjettiness observables in jets from gluons and light-flavour quarks, and in decays of boosted W bosons and top quarks

A simultaneous measurement of 25 substructure observables is presented using large-radius jets with high transverse momentum from proton-proton collisions at $\sqrt{s}$ = 13 TeV. The measurement is carried out on dijet events and $\mathrm{t\bar{t}}$ events enriched in Lorentz-boosted W bosons and top quarks decaying hadronically. The three data samples consist of jets with one, two, or three prongs from the showering and hadronization of a gluon or light-flavour quark, two quarks, or three quarks, respectively. The data correspond to an integrated luminosity of 138 fb$^{-1}$, recorded by the CMS experiment in 2016$-$2018. A detailed characterization of the jet substructure is provided using a 6-body basis of $N$-subjettiness observables that overconstrains the phase space of the resolved emissions in the jet. The measurements are unfolded to the level of stable particles, and an estimate of the particle-level correlations between observables is provided, ensuring that the results can be used to systematically assess and refine the modelling of radiation in jets.

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