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 $h_4^\mathrm{Z}$.
Post-fit reconstruction-level photon transverse momentum $p_{T}^{\gamma}$ distribution in the ECAL barrel signal region. The yields correspond to the post-fit expectation from the maximum-likelihood fit used in the analysis, with uncertainties reflecting the post-fit total (stat+syst) uncertainty per bin. Data correspond to the full Run-2 dataset (138 fb$^{-1}$ at $\sqrt{s}=13$ TeV).
Post-fit reconstruction-level photon transverse momentum $p_{T}^{\gamma}$ distribution in the ECAL endcaps signal region. The yields correspond to the post-fit expectation from the maximum-likelihood fit used in the analysis, with uncertainties reflecting the post-fit total (stat+syst) uncertainty per bin. Data correspond to the full Run-2 dataset (138 fb$^{-1}$ at $\sqrt{s}=13$ TeV).
Measured and predicted fiducial cross sections (fb) in the EB, EE, and combined phase space. The fiducial phase space definition follows the analysis selection in the paper. Predictions are shown at NLO (MADGRAPH5_aMC@NLO) and NNLO (MATRIX).
In the physics program of the CMS experiment during the CERN LHC Run 3, which started in 2022, the long-lived particle triggers have been improved and extended to expand the scope of the corresponding searches. These dedicated triggers and their performance are described in this paper, using several theoretical benchmark models that extend the standard model of particle physics. The results are based on proton-proton collision data collected with the CMS detector during 2022$-$2024 at a center-of-mass energy of 13.6 TeV, corresponding to integrated luminosities of up to 123 fb$^{-1}$.
Offline standard tracking efficiency during Run~3 for different tracking iterations, as a function of simulated radial position of the track production vertex. In the figure, $t\bar{t}$ simulation for 2025 conditions and an average PU of 62 is used, and the tracks are required to have $\mathrm{p_T}>0.9$ GeV and $|\eta|<2.5$. The tracking efficiency is defined as the ratio of the simulated tracks (with the aforementioned selection requirements) geometrically matched to a reconstructed track, divided by the total simulated tracks passing the selections.
Overall standard tracking efficiency at the HLT during Run~3, as a function of the simulated radial position of the track production vertex. In the figure, $t\bar{t}$ simulation for 2025 conditions and an average PU of 62 is used, and the tracks are required to have $\mathrm{p_T}>0.9$ GeV and $|\eta|<2.5$. The tracking efficiency is defined as the ratio of the simulated tracks (with the aforementioned selection requirements) geometrically matched to a reconstructed track, divided by the total simulated tracks passing the selections.
L1T+HLT efficiency of the MET+IsoTrk trigger as a function of the number of tracker layers with valid measurements of the track that pass the offline requirements, in $\tilde{\chi}_{1}^{\pm} \rightarrow \tilde{\chi}_{1}^{0}$+X simulated events for 2022 conditions, where $m_{\tilde{\chi}_{1}^{\pm}}=900$ GeV and $\tilde{\chi}_{1}^{0}$ is nearly mass-degenerate with $\tilde{\chi}_{1}^{\pm}$. The efficiency is shown for LLPs with $c\tau=$ 10, 100, and 1000 cm in black, blue, and red, respectively.
Gauge-mediated supersymmetry-breaking models provide a strong motivation to search for a supersymmetric partner of the tau lepton (stau) with a macroscopic lifetime. Long-lived stau decays produce tau leptons that are displaced from the primary proton-proton interaction vertex, leading to an unconventional signature. This paper presents a search for the direct production of long-lived staus decaying within the CMS tracker volume in proton-proton collisions at $\sqrt{s}$ = 13 TeV, performed for the first time with an identification algorithm based on a graph neural network dedicated to displaced tau leptons. The data sample, corresponding to an integrated luminosity of 138 fb$^{-1}$, was recorded with the CMS experiment at the CERN LHC between 2016 and 2018. This search excludes, at 95% confidence level, stau masses, $m_\tildeτ$, in the 126$-$260 (906$-$425) GeV range for a proper decay length of 50 mm in the maximally mixed (mass-degenerate) scenario, while for $m_\tildeτ $ = 200 GeV, stau proper decay lengths are excluded in the range 21$-$94 (6$-$333) mm. These results improve the exclusion limits compared to previous searches, and extend the parameter space explored in the context of supersymmetry.
Distributions of $p_\text{T, j2}$ for data and the predicted background, in the signal region. The signal distributions expected in the maximally mixed scenario for a few representative sets of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ values are overlaid: (100, 10), (100, 50), (100, 100), (200, 10), (200, 50), (200, 100), (300, 10), (300, 50), and (300, 100). In bins where the observed yield is zero, the Garwood interval at 68% CL is shown as a positive uncertainty. The last bin includes the overflow.
Distributions of $p^\text{miss}_\text{T}$ for data and the predicted background, in the signal region. The signal distributions expected in the maximally mixed scenario for a few representative sets of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ values are overlaid: (100, 10), (100, 50), (100, 100), (200, 10), (200, 50), (200, 100), (300, 10), (300, 50), and (300, 100). In bins where the observed yield is zero, the Garwood interval at 68% CL is shown as a positive uncertainty. The last bin includes the overflow.
Distributions of $m_\text{T2}$ for data and the predicted background, in the signal region. The signal distributions expected in the maximally mixed scenario for a few representative sets of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ values are overlaid: (100, 10), (100, 50), (100, 100), (200, 10), (200, 50), (200, 100), (300, 10), (300, 50), and (300, 100). In bins where the observed yield is zero, the Garwood interval at 68% CL is shown as a positive uncertainty. The last bin includes the overflow.
The production cross sections of the $Υ$(1S), $Υ$(2S), and $Υ$(3S) mesons are measured in proton-proton collisions at $\sqrt{s}$ = 13.6 TeV, using a data sample collected in 2022 by the CMS experiment and corresponding to an integrated luminosity of 37.4 fb$^{-1}$. The measurement is performed in the $μ^+μ^-$ decay channels, differentially as a function of transverse momentum in the 20$-$200 GeV range, in the $\lvert y\rvert$$\lt$ 0.6 and 0.6 $\lt$$\lvert y\rvert$$\lt$ 1.2 rapidity intervals.
Differential cross section times branching fraction for Upsilon(1S) -> mu+ mu-, measured in the rapidity range |y| < 0.6. This table corresponds to Figure 2 (left panel for |y|<0.6, right panel for 0.6<|y|<1.2) and Table A.1 in the paper. Results assume unpolarized production; polarization correction factors are provided in Table 6.
Differential cross section times branching fraction for Upsilon(1S) -> mu+ mu-, measured in the rapidity range 0.6 < |y| < 1.2. This table corresponds to Figure 2 (left panel for |y|<0.6, right panel for 0.6<|y|<1.2) and Table A.1 in the paper. Results assume unpolarized production; polarization correction factors are provided in Table 6.
Differential cross section times branching fraction for Upsilon(2S) -> mu+ mu-, measured in the rapidity range |y| < 0.6. This table corresponds to Figure 2 (left panel for |y|<0.6, right panel for 0.6<|y|<1.2) and Table A.2 in the paper. Results assume unpolarized production; polarization correction factors are provided in Table 6.
A search is presented for massive narrow-width resonances in the mass range of 1$-$4.5 TeV, decaying into pairs of Higgs bosons (HH). The search uses proton-proton collision data at a center-of-mass energy of 13 TeV collected with the CMS detector at the CERN LHC during 2016$-$2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The analysis targets final states where one Higgs boson decays into a pair of bottom quarks and the other into a pair of tau leptons, X $\to$ HH $\to$$\mathrm{b\bar{b}}τ^+τ^-$. It uses a single large jet to reconstruct the H $\to$$\mathrm{b\bar{b}}$ decay, while the H $\to$$τ^+τ^-$ decay products can either be contained within a single large jet or appear as two isolated tau leptons. The observed data are consistent with standard model background expectations. Upper limits at 95% confidence level are set on the production cross section for resonant HH production for masses between 1 and 4.5 TeV. This analysis sets the most sensitive limits to date on X $\to$ HH $\to$ $\mathrm{b\bar{b}}τ^+τ^-$ decays in the mass range of 1.4 to 4.5 TeV.
Distribution of the invariant mass of the di-$\tau$ system, reconstructed with the FastMTT algorithm, after the full event selection in the $\tau_{\mathrm{h}}\tau_{\mathrm{h}}$ channel. The data (solid circles) are compared to the background simulation (filled histograms), where the gray bands represent the total background uncertainty, obtained from the post-fit values of the dominant systematic uncertainties and the statistical uncertainties in the simulated samples. The $X\to HH$ signal simulation (solid red line) is overlaid and normalized to $\sigma(X\to HH)=0.1~\mathrm{pb}$ for illustration. The ratio between the data and the total expected background contribution is shown in the lower panel, where a solid black triangle indicates those bins where the ratio exceeds the axis range.
Distribution of the invariant mass of the di-$\tau$ system, reconstructed with the FastMTT algorithm, after the full event selection in the $\ell\tau_{\mathrm{h}}$ channel. The data (solid circles) are compared to the background simulation (filled histograms), where the gray bands represent the total background uncertainty, obtained from the post-fit values of the dominant systematic uncertainties and the statistical uncertainties in the simulated samples. The $X\to HH$ signal simulation (solid red line) is overlaid and normalized to $\sigma(X\to HH)=0.1~\mathrm{pb}$ for illustration. The ratio between the data and the total expected background contribution is shown in the lower panel, where a solid black triangle indicates those bins where the ratio exceeds the axis range.
Distribution of $M_{\mathrm{H}(\mathrm{b}\bar{\mathrm{b}})}$ obtained from the leading AK8 jet in the event after the full event selection for the $\tau_{\mathrm{h}}\tau_{\mathrm{h}}$ channel. The signal-enriched region (SR) is defined as $100 < M_{\mathrm{H}(\mathrm{b}\bar{\mathrm{b}})} < 150\ \mathrm{GeV}$. The sideband (SB) is immediately adjacent to the SR, on either side. The data (solid circles) are compared to the background simulation (filled histograms), where the gray bands represent the total background uncertainty, obtained from the post-fit values of the dominant systematic uncertainties and the statistical uncertainties in the simulated samples. The $X\to HH$ signal simulation (solid red line) is overlaid and normalized to $\sigma(X\to HH)=0.1~\mathrm{pb}$ for illustration. The ratio between the data and the total expected background contribution is shown in the lower panel, where a solid black triangle indicates those bins where the ratio exceeds the axis range.
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$^{+82}_{-78}$ fb and 3.96$^{+0.53}_{-0.51}$ fb, respectively, in agreement with the standard model predictions of 631 $\pm$ 126 fb and 3.87 $\pm$ 0.77 fb. This agreement enables stringent constraints to be imposed on anomalous quartic gauge couplings within a dimension-8 effective field theory framework.
Normalized simulated $N_{tracks}$ distributions for signal and background processes.
Normalized simulated acoplanarity distributions for signal and background processes. The acoplanarity distribution is shown for events with $N_{tracks}=0$.
Observed and predicted $p_{T}^{e\mu}$ distributions for events with $N_{tracks}=0$, using 2016--2018 data. The distributions are shown after the maximum likelihood fit to the data ('postfit distributions'). The observed data and their associated Poissonian statistical uncertainty are shown with black markers with vertical error bars. The uncertainty band accouts for all sources of background and signal uncertainty, systematic as well as statistical, after the fit. The last bin includes the overflow. The lower panels show the ratio of data to sum of signal and background contributions, before (prefit, open red circles) and after (black full markers) the maximum likelihood fit.
A search is performed for a heavy scalar resonance X decaying to a Higgs boson (H) and a Higgs-like scalar boson (Y) in the two bottom quark (H $\to$$\mathrm{b\bar{b}}$) and four quark (Y $\to$ VV $\to$ 4q) final state, where V denotes a W or Z boson. Masses of the X between 900 and 4000 GeV and the Y between 60 and 2800 GeV are considered. The search is performed in data collected by the CMS experiment at the CERN LHC from proton-proton collisions at 13 TeV center-of-mass energy, with a data set corresponding to a total integrated luminosity of 138 fb$^{-1}$. It targets the Lorentz-boosted regime, in which the products of the H $\to$$\mathrm{b\bar{b}}$ decay can be reconstructed as a single large-area jet, and those from the Y $\to$ VV $\to$ 4q decay as either one Y $\to$ 4q or two V to $\mathrm{q\bar{q}}$ jets. Jet identification and mass reconstruction exploit machine-learning tools, including a novel attention-based "particle transformer" for Y $\to$ 4q identification. No significant excess is observed in the data above the standard model background expectation. Upper limits on the product of production cross section and branching fraction as low as 0.2 fb are derived at 95% confidence level for various mass hypotheses. This is the first search at the LHC for scalar resonances in the all-hadronic $\mathrm{b\bar{b}}$VV decay channel.
Projected distributions of the $\mathrm{m}_{\mathrm{X}}^{\text{rec}}$ observable in the SP region of the fully merged (FM) category, after a maximum likelihood fit to the data with an $\mathrm{X} \to \mathrm{HY} \to \mathrm{b}\bar{\mathrm{b}}\mathrm{WW}$ signal with $\mathrm{m}_{\mathrm{X}} = 900$ GeV and $\mathrm{m}_{\mathrm{Y}} = 80$ GeV and best-fit production cross section times branching fraction of 15 fb. The lower panels show the pull per bin, defined as $(\mathrm{data} - \mathrm{bkg.})/\sigma_{\mathrm{stat}}$, where $\sigma_{\mathrm{stat}}$ is the statistical uncertainty in the data, as well as the systematic uncertainty normalized to $\sigma_{\mathrm{stat}}$. The full yields in each bin are presented here without division by the bin width as shown in the paper.
Projected distributions of the $\mathrm{m}_{\mathrm{Y}}^{\text{rec}}$ observable in the SP region of the fully merged (FM) category, after a maximum likelihood fit to the data with an $\mathrm{X} \to \mathrm{HY} \to \mathrm{b}\bar{\mathrm{b}}\mathrm{WW}$ signal with $\mathrm{m}_{\mathrm{X}} = 900$ GeV and $\mathrm{m}_{\mathrm{Y}} = 80$ GeV and best-fit production cross section times branching fraction of 15 fb. The lower panels show the pull per bin, defined as $(\mathrm{data} - \mathrm{bkg.})/\sigma_{\mathrm{stat}}$, where $\sigma_{\mathrm{stat}}$ is the statistical uncertainty in the data, as well as the systematic uncertainty normalized to $\sigma_{\mathrm{stat}}$. The full yields in each bin are presented here without division by the bin width as shown in the paper.
Projected distributions of the $\mathrm{m}_{\mathrm{X}}^{\text{rec}}$ observable in the SP region of the semimerged (SM) category, after a maximum likelihood fit to the data with an $\mathrm{X} \to \mathrm{HY} \to \mathrm{b}\bar{\mathrm{b}}\mathrm{WW}$ signal with $\mathrm{m}_{\mathrm{X}} = 1200$ GeV and $\mathrm{m}_{\mathrm{Y}} = 900$ GeV and best-fit production cross section times branching fraction of 250 fb. The lower panels show the pull per bin, defined as $(\mathrm{data} - \mathrm{bkg.})/\sigma_{\mathrm{stat}}$, where $\sigma_{\mathrm{stat}}$ is the statistical uncertainty in the data, as well as the systematic uncertainty normalized to $\sigma_{\mathrm{stat}}$. The full yields in each bin are presented here without division by the bin width as shown in the paper.
Three structures, X(6600), X(6900), and X(7100), have emerged from the J$/ψ\,$J$/ψ$ (J$/ψ$\to$μ^+μ^-$) mass spectrum. These are candidates of all-charm tetraquarks, an exotic form of hadronic matter. A clearer picture of these states is obtained using proton-proton collision data collected by the CMS detector that corresponds to 315 fb$^{-1}$, which yields 3.6 times more J$/ψ\,$J$/ψ$ pairs than previous studies by CMS. All three structures, and their mutual interference, have statistical significances above five standard deviations. The presence of interference implies that the structures have common quantum numbers. Their squared masses align linearly with a resonance index and have natural widths that systematically decrease as the index increases. These features are consistent with radial excitations of tetraquarks composed of two aligned spin-1 diquarks without orbital excitation, and disfavor other interpretations. The J$/ψ\,$$ψ$(2S) $\to$$μ^+μ^-μ^+μ^-$ decay mode is also explored and the X(6900) and X(7100) states are found with significances exceeding 8 and 4 standard deviations, respectively.
Measured masses and widths of the three X states from the fits to the $\mathrm{J}/\psi\mathrm{J}/\psi$ mass spectrum from the Run 2+3 data sets. The amplitudes (phases) of the X(6600) and X(7100) relative to the X(6900) state are r1 = 1.790 ± 0.737 (phi1 = 1.693 ± 0.660 rad) and r3 = 0.429 ± 0.267 (phi3 = -0.388 ± 0.410 rad), respectively.
Measured masses and widths of the three X states from the fits to the $\mathrm{J}/\psi \psi(2S)$ mass spectrum from the Run 2+3 data sets.The amplitudes (phases) of the X(7100) relative to the X(6900) state are r = 0.692 ± 0.225 (phi1 = -1.486 ± 0.970 rad).
The $\mathrm{J}/\psi\mathrm{J}/\psi$ invariant-mass spectrum covering the full range of the fit: 6.175 - 15.0 GeV.
The target asymmetry T, recoil asymmetry P, and beam-target double polarization observable H were determined in exclusive $\pi ^0$ and $\eta $ photoproduction off quasi-free protons and, for the first time, off quasi-free neutrons. The experiment was performed at the electron stretcher accelerator ELSA in Bonn, Germany, with the Crystal Barrel/TAPS detector setup, using a linearly polarized photon beam and a transversely polarized deuterated butanol target. Effects from the Fermi motion of the nucleons within deuterium were removed by a full kinematic reconstruction of the final state invariant mass. A comparison of the data obtained on the proton and on the neutron provides new insight into the isospin structure of the electromagnetic excitation of the nucleon. Earlier measurements of polarization observables in the $\gamma p \rightarrow \pi ^0 p$ and $\gamma p \rightarrow \eta p$ reactions are confirmed. The data obtained on the neutron are of particular relevance for clarifying the origin of the narrow structure in the $\eta n$ system at $W = 1.68\ \textrm{GeV}$. A comparison with recent partial wave analyses favors the interpretation of this structure as arising from interference of the $S_{11}(1535)$ and $S_{11}(1650)$ resonances within the $S_{11}$-partial wave.
Target asymmetry T, recoil asymmetry P, and polarization observable H for $\gamma p \to \pi^0 p$ as a function of the polar center-of-mass angle for bins at the given centroid c.m. energies.
Target asymmetry T, recoil asymmetry P, and polarization observable H for $\gamma n \to \pi^0 n$ as a function of the polar center-of-mass angle for bins at the given centroid c.m. energies.
Target asymmetry T, recoil asymmetry P, and polarization observable H for $\gamma p \to \eta p$ as a function of the polar center-of-mass angle for bins at the given centroid c.m. energies.
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