The Pixel Luminosity Telescope is a silicon pixel detector dedicated to luminosity measurement at the CMS experiment at the LHC. It is located approximately 1.75 m from the interaction point and arranged into 16 “telescopes”, with eight telescopes installed around the beam pipe at either end of the detector and each telescope composed of three individual silicon sensor planes. The per-bunch instantaneous luminosity is measured by counting events where all three planes in the telescope register a hit, using a special readout at the full LHC bunch-crossing rate of 40 MHz. The full pixel information is read out at a lower rate and can be used to determine calibrations, corrections, and systematic uncertainties for the online and offline measurements. This paper details the commissioning, operational history, and performance of the detector during Run 2 (2015–18) of the LHC, as well as preparations for Run 3, which will begin in 2022.
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Abstract A study of the anomalous couplings of the Higgs boson to vector bosons, including
-violation effects, has been conducted using its production and decay in the WW channel. This analysis is performed on proton–proton collision data collected with the CMS detector at the CERN LHC during 2016–2018 at a center-of-mass energy of 13 TeV, and corresponds to an integrated luminosity of 138$${\textit{CP}}$$ . The different-flavor dilepton$$\,\text {fb}^{-1}$$ final state is analyzed, with dedicated categories targeting gluon fusion, electroweak vector boson fusion, and associated production with a W or Z boson. Kinematic information from associated jets is combined using matrix element techniques to increase the sensitivity to anomalous effects at the production vertex. A simultaneous measurement of four Higgs boson couplings to electroweak vector bosons is performed in the framework of a standard model effective field theory. All measurements are consistent with the expectations for the standard model Higgs boson and constraints are set on the fractional contribution of the anomalous couplings to the Higgs boson production cross section.$$({\textrm{e}} {{\upmu }})$$ Free, publicly-accessible full text available August 1, 2025 -
A bstract Measurements of the charge-dependent two-particle angular correlation function in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of
= 8$$ \sqrt{s_{\textrm{NN}}} $$ . 16 TeV and lead-lead (PbPb) collisions at = 5$$ \sqrt{s_{\textrm{NN}}} $$ . 02 TeV are reported. The pPb and PbPb data sets correspond to integrated luminosities of 186 nb− 1and 0.607 nb− 1, respectively, and were collected using the CMS detector at the CERN LHC. The charge-dependent correlations are characterized by balance functions of same- and opposite-sign particle pairs. The balance functions, which contain information about the creation time of charged particle pairs and the development of collectivity, are studied as functions of relative pseudorapidity (∆η ) and relative azimuthal angle (∆ϕ ), for various multiplicity and transverse momentum (p T) intervals. A multiplicity dependence of the balance function is observed in ∆η and ∆ϕ for both systems. The width of the balance functions decreases towards high-multiplicity collisions in the momentum region< 2 GeV, for pPb and PbPb results. Integrals of the balance functions are presented in both systems, and a mild dependence of the charge-balancing fractions on multiplicity is observed. No multiplicity dependence is observed at higher transverse momentum. The data are compared withhydjet ,hijing , andampt generator predictions, none of which capture completely the multiplicity dependence seen in the data. The comparison of results with different center-of-mass energies suggests that the balance functions become narrower at higher energies, which is consistent with the idea of delayed hadronization and the effect of radial flow.Free, publicly-accessible full text available August 1, 2025 -
Abstract A measurement is presented of a ratio observable that provides a measure of the azimuthal correlations among jets with large transverse momentum
. This observable is measured in multijet events over the range of$$p_{\textrm{T}}$$ –$$p_{\textrm{T}} = 360$$ based on data collected by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13$$3170\,\text {Ge}\hspace{-.08em}\text {V} $$ , corresponding to an integrated luminosity of 134$$\,\text {Te}\hspace{-.08em}\text {V}$$ . The results are compared with predictions from Monte Carlo parton-shower event generator simulations, as well as with fixed-order perturbative quantum chromodynamics (pQCD) predictions at next-to-leading-order (NLO) accuracy obtained with different parton distribution functions (PDFs) and corrected for nonperturbative and electroweak effects. Data and theory agree within uncertainties. From the comparison of the measured observable with the pQCD prediction obtained with the NNPDF3.1 NLO PDFs, the strong coupling at the Z boson mass scale is$$\,\text {fb}^{-1}$$ , where the total uncertainty is dominated by the scale dependence of the fixed-order predictions. A test of the running of$$\alpha _\textrm{S} (m_{{\textrm{Z}}}) =0.1177 \pm 0.0013\, \text {(exp)} _{-0.0073}^{+0.0116} \,\text {(theo)} = 0.1177_{-0.0074}^{+0.0117}$$ in the$$\alpha _\textrm{S}$$ region shows no deviation from the expected NLO pQCD behaviour.$$\,\text {Te}\hspace{-.08em}\text {V}$$ Free, publicly-accessible full text available August 1, 2025 -
Energy correlators that describe energy-weighted distances between two or three particles in a hadronic jet are measured using an event sample ofproton-proton collisions collected by the CMS experiment and corresponding to an integrated luminosity of. The measured distributions are consistent with the trends in the simulation that reveal two key features of the strong interaction: confinement and asymptotic freedom. By comparing the ratio of the measured three- and two-particle energy correlator distributions with theoretical calculations that resum collinear emissions at approximate next-to-next-to-leading-logarithmic accuracy matched to a next-to-leading-order calculation, the strong coupling is determined at theboson mass:, the most precisevalue obtained using jet substructure observables.
© 2024 CERN, for the CMS Collaboration 2024 CERN Free, publicly-accessible full text available August 1, 2025 -
The first observation of the decayand measurement of the branching ratio oftoare presented. Theandmesons are reconstructed using their dimuon decay modes. The results are based on proton-proton colliding beam data from the LHC collected by the CMS experiment atin 2016–2018, corresponding to an integrated luminosity of. The branching fraction ratio is measured to be, where the last uncertainty comes from the uncertainties in the branching fractions of the charmonium states. New measurements of thebaryon mass and natural width are also presented, using thefinal state, where thebaryon is reconstructed through the decays,,, and. Finally, the fraction ofbaryons produced fromdecays is determined.
© 2024 CERN, for the CMS Collaboration 2024 CERN Free, publicly-accessible full text available July 1, 2025 -
A search for beyond the standard model spin-0 bosons,, that decay into pairs of electrons, muons, or tau leptons is presented. The search targets the associated production of such bosons with aorgauge boson, or a top quark-antiquark pair, and uses events with three or four charged leptons, including hadronically decaying tau leptons. The proton-proton collision data set used in the analysis was collected at the LHC from 2016 to 2018 at a center-of-mass energy of 13 TeV, and corresponds to an integrated luminosity of. The observations are consistent with the predictions from standard model processes. Upper limits are placed on the product of cross sections and branching fractions of such new particles over the mass range of 15 to 350 GeV with scalar, pseudoscalar, or Higgs-boson-like couplings, as well as on the product of coupling parameters and branching fractions. Several model-dependent exclusion limits are also presented. For a Higgs-boson-likemodel, limits are set on the mixing angle of the Higgs boson with theboson. For the associated production of aboson with a top quark-antiquark pair, limits are set on the coupling to top quarks. Finally, limits are set for the first time on a fermiophilic dilaton-like model with scalar couplings and a fermiophilic axion-like model with pseudoscalar couplings.
© 2024 CERN, for the CMS Collaboration 2024 CERN Free, publicly-accessible full text available July 1, 2025 -
A bstract A search for “emerging jets” produced in proton-proton collisions at a center-of-mass energy of 13 TeV is performed using data collected by the CMS experiment corresponding to an integrated luminosity of 138 fb
− 1. This search examines a hypothetical dark quantum chromodynamics (QCD) sector that couples to the standard model (SM) through a scalar mediator. The scalar mediator decays into an SM quark and a dark sector quark. As the dark sector quark showers and hadronizes, it produces long-lived dark mesons that subsequently decay into SM particles, resulting in a jet, known as an emerging jet, with multiple displaced vertices. This search looks for pair production of the scalar mediator at the LHC, which yields events with two SM jets and two emerging jets at leading order. The results are interpreted using two dark sector models with different flavor structures, and exclude mediator masses up to 1950 (1950) GeV for an unflavored (flavor-aligned) dark QCD model. The unflavored results surpass a previous search for emerging jets by setting the most stringent mediator mass exclusion limits to date, while the flavor-aligned results provide the first direct mediator mass exclusion limits to date.Free, publicly-accessible full text available July 1, 2025 -
Abstract A search for
and$${\text {Z}{}{}} {\text {Z}{}{}} $$ production in the$${\text {Z}{}{}} {\text {H}{}{}} $$ final state is presented, where H is the standard model (SM) Higgs boson. The search uses an event sample of proton-proton collisions corresponding to an integrated luminosity of 133$${\text {b}{}{}} {\bar{{\text {b}{}{}}}{}{}} {\text {b}{}{}} {\bar{{\text {b}{}{}}}{}{}} $$ collected at a center-of-mass energy of 13$$\,\text {fb}^{-1}$$ with the CMS detector at the CERN LHC. The analysis introduces several novel techniques for deriving and validating a multi-dimensional background model based on control samples in data. A multiclass multivariate classifier customized for the$$\,\text {Te}\hspace{-.08em}\text {V}$$ final state is developed to derive the background model and extract the signal. The data are found to be consistent, within uncertainties, with the SM predictions. The observed (expected) upper limits at 95% confidence level are found to be 3.8 (3.8) and 5.0 (2.9) times the SM prediction for the$${\text {b}{}{}} {\bar{{\text {b}{}{}}}{}{}} {\text {b}{}{}} {\bar{{\text {b}{}{}}}{}{}} $$ and$${\text {Z}{}{}} {\text {Z}{}{}} $$ production cross sections, respectively.$${\text {Z}{}{}} {\text {H}{}{}} $$ Free, publicly-accessible full text available July 1, 2025