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A method for correcting the substructure of multiprong jets using the Lund jet plane
(Springer, 2025) Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Damanakis, K.
Many analyses at the CERN LHC exploit the substructure of jets to identify heavy resonances produced with high momenta that decay into multiple quarks and/or gluons. This paper presents a new technique for correcting the substructure of simulated large-radius jets from multiprong decays. The technique is based on reclustering the jet constituents into several subjets such that each subjet represents a single prong, and separately correcting the radiation pattern in the Lund jet plane of each subjet using a correction derived from data. The data presented here correspond to an integrated luminosity of 138 fb(-1) collected by the CMS experiment between 2016-2018 at a center-of-mass energy of 13TeV. The correction procedure improves the agreement between data and simulation for several different substructure observables of multiprong jets. This technique establishes, for the first time, a robust calibration for the substructure of jets with four or more prongs, enabling future measurements and searches for new phenomena containing these signatures.
Constraints on standard model effective field theory for a Higgs boson produced in association with W or Z bosons in the H → b(b)over-bar decay channel in proton-proton collisions at √s=13 TeV
(Springer, 2025) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.
A standard model effective field theory (SMEFT) analysis with dimension-six operators probing nonresonant new physics effects is performed in the Higgs-strahlung process, where the Higgs boson is produced in association with a W or Z boson, in proton-proton collisions at a center-of-mass energy of 13 TeV. The final states in which the W or Z boson decays leptonically and the Higgs boson decays to a pair of bottom quarks are considered. The analyzed data were collected by the CMS experiment between 2016 and 2018 and correspond to an integrated luminosity of 138 fb(-1). An approach designed to simultaneously optimize the sensitivity to Wilson coefficients of multiple SMEFT operators is employed. Likelihood scans as functions of the Wilson coefficients that carry SMEFT sensitivity in this final state are performed for different expansions in SMEFT. The results are consistent with the predictions of the standard model.
Determination of the strong coupling and its running from measurements of inclusive jet production
(Elsevier, 2025) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.
The value of the strong coupling alpha(S) is determined in a comprehensive analysis at next-to-next-to-leading order accuracy in quantum chromodynamics. The analysis uses double-differential cross section measurements from the CMS Collaboration at the CERN LHC of inclusive jet production in proton-proton collisions at centre-of-mass energies of 2.76, 7, 8, and 13 TeV, combined with inclusive deep-inelastic data from HERA. The value alpha(S)(m(Z)) = 0.1176(-0.0016)(+0.0014) is obtained at the scale of the Z boson mass. By using the measurements in different intervals of jet transverse momentum, the running of alpha(S) is probed for energies between 100 and 1600GeV.
Development of systematic uncertainty-aware neural network trainings for binned-likelihood analyses at the LHC
(Springer, 2025) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.
We propose a neural network training method capable of accounting for the effects of systematic variations of the data model in the training process and describe its extension towards neural network multiclass classification. The procedure is evaluated on the realistic case of the measurement of Higgs boson production via gluon fusion and vector boson fusion in the tau tau decay channel at the CMS experiment. The neural network output functions are used to infer the signal strengths for inclusive production of Higgs bosons as well as for their production via gluon fusion and vector boson fusion. We observe improvements of 12 and 16% in the uncertainty in the signal strengths for gluon and vector-boson fusion, respectively, compared with a conventional neural network training based on cross-entropy.
Evidence for Similar Collectivity of High Transverse-Momentum Particles in p-Pb and Pb-Pb Collisions
(Amer Physical Soc, 2025) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.
Charged hadron elliptic anisotropies (v(2)) are presented over a wide transverse momentum (p(T)) range for proton-lead (pPb) and lead-lead (PbPb) collisions at nucleon-nucleon center-of-mass energies of 8.16 and 5.02 TeV, respectively. The data were recorded by the CMS experiment and correspond to integrated luminosities of 186 and 0.607 nb(-1) for the pPb and PbPb systems, respectively. A four-particle cumulant analysis is performed using subevents separated in pseudorapidity to effectively suppress noncollective effects. At high pT (p(T) > 8 GeV), significant positive v(2) values that are similar between pPb and PbPb collisions at comparable charged particle multiplicities are observed. This observation suggests a common origin for the multiparticle collectivity for high-p(T) particles in the two systems.
Evidence of medium response to hard probes using correlations of Z bosons with hadrons in heavy ion collisions
(Elsevier, 2026) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.
The first measurement of pseudorapidity and azimuthal angle distributions relative to the momentum vector of a Z boson for low transverse momentum (p(T)) charged hadrons in lead-lead (PbPb) collisions is presented. By studying the hadrons produced in an event with a high-p(T) Z boson (40 < p(T) < 350 GeV), the analysis probes how the quark-gluon plasma (QGP) medium created in these collisions affects the parton recoiling opposite to the Z boson. Utilizing PbPb data at a nucleon-nucleon center-of-mass energy root s(NN) = 5.02 TeV from 2018 with an integrated luminosity of 1.67 nb(-1) and proton-proton (pp) data at the same energy from 2017 with 301 pb(-1), the distributions are examined in bins of charged-hadron p(T). A significant modification of the distributions for charged hadrons in the range 1 < p(T) < 2 GeV in PbPb collisions is observed when compared to reference measurements from pp collisions. The data provide new information about the correlation between hard and soft particles in heavy ion collisions, which can be used to test predictions of various jet quenching models. When compared with theoretical predictions, the results are consistent with expectations of a hydrodynamic wake created when the QGP is depleted of energy by the parton propagating through it. Therefore, this Letter presents the first evidence of probe-induced energy depletion and the resulting response by the QGP medium.
First Exclusive Reconstruction of the B*+, B*0, and Bs*0 Mesons and Precise Measurement of Their Masses
(Amer Physical Soc, 2026) Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.; Bergauer, T.
Using proton-proton collision data collected by the CMS experiment at root s = 13 TeV in 2016-2018, corresponding to an integrated luminosity of 140 fb(-1), the first full reconstruction of the three vector B meson states, B*(+), B-*0, and B-s(*0), is performed. The mass differences between the excited mesons and their corresponding ground states are measured to be m(B*(+)) - m(B+) 45.277 +/- 0.039 +/- 0.027 MeV, m(B*(0))- m(B-0) = 45.471 +/- 0.056 +/- 0.028 MeV, and m(B-s(0)) - m(B-s(0)) = 49.407 +/- 0.132 +/- 0.041 MeV, where the first uncertainties are statistical and the second are systematic. These results improve on the precision of previous measurements by an order of magnitude.
General search for supersymmetric particles in scenarios with compressed mass spectra using proton-proton collisions at √s=13 TeV
(Amer Physical Soc, 2025) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.
A general search is presented for supersymmetric particles (sparticles) in scenarios featuring compressed mass spectra using proton-proton collisions at a center-of-mass energy of 13 TeV, recorded with the CMS detector at the LHC. The analyzed data sample corresponds to an integrated luminosity of 138 fb(-1). Awide range of potential sparticle signatures are targeted, including pair production of electroweakinos, sleptons, and top squarks. The search focuses on events with a high transverse momentum system from initial-stateradiation jets recoiling against a potential sparticle system with significant missing transverse momentum. Events are categorized based on their lepton multiplicity, jet multiplicity, number of b-tagged jets, and kinematic variables sensitive to the sparticle masses and mass splittings. The sensitivity extends to higher parent sparticle masses than previously probed at the LHC for production of pairs of electroweakinos, sleptons, and top squarks with mass spectra featuring small mass splittings (compressed mass spectra). The observed results demonstrate agreement with the predictions of the background-only model. Lower mass limits are set at 95% confidence level on production of pairs of electroweakinos, sleptons, and top squarks that extend to 325, 275, and 780 GeV, respectively, for the most favorable compressed mass regime cases.
Identification of low-momentum muons in the CMS detector using multivariate techniques in proton-proton collisions at √s=13.6 TeV
(Iop Publishing Ltd, 2025) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.
Soft muons with a transverse momentum below 10 GeV are featured in many processes studied by the CMS experiment, such as decays of heavy-flavor hadrons or rare tau lepton decays. Maximizing the selection efficiency for these muons, while simultaneously suppressing backgrounds from long-lived light-flavor hadron decays, is therefore important for the success of the CMS physics program. Multivariate techniques have been shown to deliver better muon identification performance than traditional selection techniques. To take full advantage of the large data set currently being collected during Run 3 of the CERN LHC, a new multivariate classifier based on a gradient-boosted decision tree has been developed. It offers a significantly improved separation of signal and background muons compared to a similar classifier used for the analysis of the Run 2 data. The performance of the new classifier is evaluated on a data set collected with the CMS detector in 2022 and 2023, corresponding to an integrated luminosity of 62 fb(-1).
Measurement of (Formula presented) Meson Photoproduction in Ultraperipheral Heavy Ion Collisions
(American Physical Society, 2026) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Benato, L.
This Letter reports the first measurement of photonuclear (Formula presented) meson production in ultraperipheral heavy ion collisions. The study is performed using lead-lead collision data, with an integrated luminosity of (Formula presented), collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 5.36 TeV. Photonuclear events, where one of the colliding nuclei breaks up and the other remains intact, are selected based on breakup neutron emissions and by requiring no particle activity in a large rapidity interval in the direction of the photon-emitting nucleus. The (Formula presented) mesons are reconstructed via the (Formula presented) decay channel, with the cross section measured as a function of (Formula presented) meson transverse momentum and rapidity. The results are compared with next-to-leading-order perturbative QCD calculations that employ recent parametrizations of the lead nuclear parton distribution functions, as well as with predictions based on the color glass condensate framework. This measurement is the first photonuclear collision study characterizing parton distribution functions of lead nuclei for parton fractional momenta (Formula presented) (relative to the nucleon) ranging approximately from a few (Formula presented) to (Formula presented) for different hard energy scale (Formula presented) selections. © 2026 CERN, for the CMS Collaboration.
Measurement of event shapes in minimum-bias events from proton-proton collisions at √s=13 TeV
(Amer Physical Soc, 2025) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.
A measurement of event-shape variables is presented, using a data sample produced in a special run with approximately one inelastic proton-proton collision per bunch crossing. The data were collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 64 mu b(-1). A number of observables related to the overall distribution of charged particles in the collisions are corrected for detector effects and compared with simulations. Inclusive event-shape distributions, as well as differential distributions of event shapes as functions of charged-particle multiplicity, are studied. None of the models investigated are able to satisfactorily describe the data. Moreover, there are significant features common amongst all generator setups studied, particularly showing data being more isotropic than any of the simulations. Multidimensional unfolded distributions are provided, along with their correlations.
Measurement of WWZ and ZH Production Cross Sections at √s=13 and 13.6 TeV
(Amer Physical Soc, 2025) Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.; Bergauer, T.
A measurement is presented of the cross section in proton-proton collisions for the production of two W bosons and one Z boson. It is based on data recorded by the CMS experiment at the CERN LHC at center-of-mass energies root s = 13 and 13.6 TeV, corresponding to an integrated luminosity of 200 fb(-1). Events with four charged leptons (electrons or muons) in the final state are selected. Both nonresonant WWZ production and ZH production, with the Higgs boson decaying into two W bosons, are reported. For the first time, the two processes are measured separately in a simultaneous fit. Combining the two modes, signal strengths relative to the standard model (SM) predictions of 0.75(-0.29)(+0.34) and 1.74(-0.60)(+0.71) are measured for root s = 13 and 13.6 TeV, respectively. The observed (expected) significance for the triboson signal is 3.8 (2.5) standard deviations for root s = 13.6 TeV, thus providing the first evidence for triboson production at this center-of-mass energy. Combining the two modes and the two center-of-mass energies, the inclusive signal strength relative to the SM prediction is measured to be 1.03(-0.28)(+0.31), with an observed (expected) significance of 4.5 (5.0) standard deviations.
Measurements of inclusive and differential Higgs boson production cross sections at √s=13.6 TeV in the H → γγ decay channel
(Springer, 2025) Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.; Bergauer, T.
Inclusive and differential cross sections for Higgs boson production in proton-proton collisions at a centre-of-mass energy of 13.6TeV are measured using data collected with the CMS detector at the LHC in 2022, corresponding to an integrated luminosity of 34.7 fb(-1). Events with the diphoton final state are selected, and the measured inclusive fiducial cross section is sfid = 74 +/- 11 (stat)(-4)(+5) (syst) fb, in agreement with the standard model prediction of 67.8 +/- 3.8 fb. Differential cross sections are measured as functions of several observables: the Higgs boson transverse momentum and rapidity, the number of associated jets, and the transverse momentum of the leading jet in the event. Within the uncertainties, the differential cross sections agree with the standard model predictions.
Measurements of the Higgs boson production cross section in the four-lepton final state in proton-proton collisions at √s=13.6 TeV
(Springer, 2025) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.
The measurements of the Higgs boson (H) production cross sections performed by the CMS Collaboration in the four-lepton (4l, l = e, mu) final state at a center-of-mass energy root s = 13.6 TeV are presented. These measurements are based on data collected with the CMS detector at the CERN LHC in 2022, corresponding to an integrated luminosity of 34.7 fb(-1). Cross sections are measured in a fiducial region closely matching the experimental acceptance, both inclusively and differentially, as a function of the transverse momentum and the absolute value of the rapidity of the four-lepton system. The H -> ZZ -> 4l inclusive fiducial cross section is measured to be 2.89(-0.49)(+0.53) (stat)(-0.21)(+0.29) (syst) fb, in agreement with the standard model expectation of 3.09(-0.24)(+0.27)fb.
Measurements of the inclusive W and Z boson production cross sections and their ratios in proton-proton collisions at √s=13.6 TeV
(Springer, 2026) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.
Measurements are presented of the W and Z boson production cross sections in proton-proton collisions at a center-of-mass energy of 13.6TeV. Data collected in 2022 and corresponding to an integrated luminosity of 5.01 fb(-1) with one or two identified muons in the final state are analyzed. The results for the products of total inclusive cross sections and branching fractions for muonic decays of W and Z bosons are 11.93 +/- 0.08 (syst) +/- 0.17 (lumi)(-0.07)(+0.07) (acceptance) nb for W+ boson production, 8.86 +/- 0.06 (syst) +/- 0.12 (lumi)(-0.06) (+0.05) (acceptance) nb for W- boson production, and 2.021 +/- 0.009 (syst) +/- 0.028 (lumi)(-0.013)(+0.011) (acceptance) nb for the Z boson production in the dimuon mass range of 60-120 GeV, all with negligible statistical uncertainties. Furthermore, the corresponding fiducial cross sections, as well as cross section ratios for both fiducial and total phase space, are provided. The ratios include charge-separated results for W boson production (W+ and W-) and the sum of the two contributions (W-+/-), each relative to the measured Z boson production cross section. Additionally, the ratio of the measured cross sections for W+ and W- boson production is reported. All measurements are in agreement with theoretical predictions, calculated at next-to-next-to-leading order accuracy in quantum chromodynamics.
Model-agnostic search for dijet resonances with anomalous jet substructure in proton-proton collisions at s=13 TeV
(Iop Publishing Ltd, 2025) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.
This paper presents a model-agnostic search for narrow resonances in the dijet final state in the mass range 1.8-6 TeV. The signal is assumed to produce jets with substructure atypical of jets initiated by light quarks or gluons, with minimal additional assumptions. Search regions are obtained by utilizing multivariate machine-learning methods to select jets with anomalous substructure. A collection of complementary anomaly detection methods-based on unsupervised, weakly supervised, and semisupervised algorithms-are used in order to maximize the sensitivity to unknown new physics signatures. These algorithms are applied to data corresponding to an integrated luminosity of 138 fb-1, recorded by the CMS experiment at the LHC, at a center-of-mass energy of 13 TeV. No significant excesses above background expectations are seen. Exclusion limits are derived on the production cross section of benchmark signal models varying in resonance mass, jet mass, and jet substructure. Many of these signatures have not been previously sought, making several of the limits reported on the corresponding benchmark models the first ever. When compared to benchmark inclusive and substructure-based search strategies, the anomaly detection methods are found to significantly enhance the sensitivity to a variety of models.
Model-independent measurement of the Higgs boson associated production with two jets and decaying to a pair of W bosons in proton-proton collisions at s=13 TeV
(Springer Science and Business Media Deutschland GmbH, 2026) Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Benato, L.; Bergauer, T.
A model-independent measurement of the differential production cross section of the Higgs boson decaying into a pair of W bosons, with a final state including two jets produced in association, is presented. In the analysis, events are selected in which the decay products of the two W bosons consist of an electron, a muon, and missing transverse momentum. The model independence of the measurement is maximized by employing a discriminating variable, developed through machine learning, that is agnostic to the signal hypothesis. The analysis is based on proton-proton collision data at s=13 TeV collected with the CMS detector from 2016–2018, corresponding to an integrated luminosity of 138 fb−1. The production cross section is measured as a function of the difference in azimuthal angle between the two jets. The differential cross section measurements are used to constrain Higgs boson couplings within the standard model effective field theory framework. © The Author(s) 2026.
Observation of Coherent φ(1020) Meson Photoproduction in Ultraperipheral PbPb Collisions at √sNN=5.36 TeV
(Amer Physical Soc, 2025) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.
The first observation of coherent phi(1020) meson photoproduction off heavy nuclei is presented using ultraperipheral lead-lead collisions at a center-of-mass energy per nucleon pair of 5.36 TeV. The data were collected by the CMS experiment and correspond to an integrated luminosity of 1.62 mu b(-1). The phi(1020) meson signals are reconstructed via the K+K- decay channel. The production cross section is presented as a function of the phi(1020) meson rapidity in the range 0.3 < vertical bar y vertical bar < 1.0, probing gluons that carry a fraction of the nucleon momentum (x) around 10(-4). The observed cross section exhibits little dependence on rapidity and is significantly suppressed, by a factor of similar to 5, compared to a baseline model that treats a nucleus as a collection of free nucleons. Theoretical models that incorporate the nuclear shadowing effect generally provide a better description of the phi(1020) data than those incorporating gluon saturation. This study establishes a powerful new tool for exploring nuclear effects and nuclear gluonic structure in the small-x regime at a unique energy scale bridging the perturbative and nonperturbative quantum chromodynamics domains.
Observation of nuclear modification of energy-energy correlators inside jets in heavy ion collisions
(Elsevier, 2025) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.
Energy-energy correlators are constructed by averaging the number of charged particle pairs within jets, weighted by the product of their transverse momenta, as a function of the angular separation of the particles within a pair. They are sensitive to a multitude of perturbative and nonperturbative quantum chromodynamics phenomena in high-energy particle collisions. Using lead-lead data recorded with the CMS detector, energy-energy correlators inside high transverse momentum jets are measured in heavy ion collisions for the first time. The data are obtained at a nucleon-nucleon center-of-mass energy of 5.02TeV and correspond to an integrated luminosity of 1.70 nb(-1). A similar analysis is done for proton-proton collisions at the same center-of-mass energy to establish a reference. The ratio of lead-lead to proton-proton energy-energy correlators reveals significant jet substructure modifications in the quark-gluon plasma. The results are compared to different models that incorporate either color coherence or medium response effects, where the two effects predict similar substructure modifications.
Observation of the Charged-Particle Multiplicity Dependence of (Formula presented) in (Formula presented)-Pb Collisions at 8.16 TeV
(American Physical Society, 2025) Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Benato, L.
Bound states of charm and anticharm quarks, known as charmonia, have a rich spectroscopic structure that can be used to probe the dynamics of hadron production in high-energy hadron collisions. Here, the cross section ratio of excited (Formula presented) and ground state (Formula presented) vector mesons is measured as a function of the charged-particle multiplicity in proton-lead ((Formula presented)) collisions at a center-of-mass (CM) energy per nucleon pair of 8.16 TeV. The data corresponding to an integrated luminosity of (Formula presented) were collected using the CMS detector. The ratio is measured separately for prompt and nonprompt charmonia in the transverse momentum range (Formula presented) and in four rapidity ranges spanning (Formula presented). For the first time, a statistically significant multiplicity dependence of the prompt cross section ratio is observed in proton-nucleus collisions. There is no clear rapidity dependence in the ratio. The prompt measurements are compared with a theoretical model which includes interactions with nearby particles during the evolution of the system. These results provide additional constraints on hadronization models of heavy quarks in nuclear collisions. © 2025 CERN, for the CMS Collaboration.

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