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).
A combined statistical analysis of searches for heavy vector boson resonances decaying into pairs of W, Z, or Higgs bosons, as well as into quark pairs ($\mathrm{q\bar{q}}$, $\mathrm{b\bar{b}}$, $\mathrm{t\bar{t}}$, $\mathrm{t\bar{b}}$) or lepton pairs ($\ell^+\ell^-$, $\ell\barν$), with $\ell =$ e, $μ$, $τ$, is presented. The results are based on proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$, collected by the CMS experiment from 2016 to 2018. No significant deviation from the expectations of the standard model is observed. The results are interpreted in the simplified heavy vector triplet (HVT) framework, setting 95% confidence level upper limits on the production cross sections and coupling strengths to standard model particles or the HVT bosons. The results exclude HVT resonances with masses below 5.5 TeV in a weakly coupled scenario, below 4.8 TeV in a strongly coupled scenario, and up to 2.0 TeV in the case of production via vector boson fusion. The combination provides the most stringent constraints to date on new phenomena predicted by the HVT model.
Expected and observed 95% CL upper limits on the V'boson production cross section as functions of the resonance mass mV' shown separately for the V' → quarks category. The limits are evaluated in the HVT model A scenario.
Expected and observed 95% CL upper limits on the V'boson production cross section as functions of the resonance mass mV' shown separately for the V' → leptons category. The limits are evaluated in the HVT model A scenario.
Expected and observed 95% CL upper limits on the V' boson production cross section as functions of the resonance mass mV' shown separately for the V' → bosons category. The limits are evaluated in the HVT model B scenario.
A measurement of the Z$γ$ production cross section in proton-proton collisions at a center-of-mass energy of 13.6 TeV is presented. Data corresponding to an integrated luminosity of 34.8 fb$^{-1}$, collected by the CMS experiment at the LHC in 2022 are used. Events with an oppositely charged pair of muons or electrons, with an invariant mass corresponding to a Z boson, together with an isolated photon are selected. The measured fiducial cross section for the combined electron and muon channels is 1.896 $\pm$ 0.033 (stat) $\pm$ 0.05 (syst) $\pm$ 0.006 (theo) pb, in agreement with the standard model prediction of 1.922 $\pm$ 0.094 pb. Constraints on neutral triple gauge couplings generated by dimension-8 operators in a recently proposed effective field theory framework are determined for the first time.
Histograms represent the post-fit distribution of $mass_{\mu^+\mu^-\gamma}$. The number of signal and background are associated with the total uncertainty, and the number of data events are associated with the poisson errors. The last bins include overflow events.
Histograms represent the post-fit distribution of $mass_{e^+e^-\gamma}$. The number of signal and background are associated with the total uncertainty, and the number of data events are associated with the poisson errors. The last bins include overflow events.
Expected and observed 95% CL limits on nTGC parameters for the combination of the measurements in the electron and muon channels. The first three rows show the results using the VPM that preserves only the U(1)EM symmetry, while the last three rows show the results from the GSPM that preserves the SU(2)L x U(1)Y symmetry. Corresponding to Table 3 in the paper.
This paper presents a combination of searches for the nonresonant production of Higgs boson pairs (HH) in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data set was collected by the CMS experiment at the LHC from 2016 to 2018 and corresponds to a total integrated luminosity of 138 fb$^{-1}$. The observed (expected) upper limit on the inclusive HH production cross section relative to the standard model (SM) prediction is found to be 3.5 (2.5). Assuming all other Higgs boson couplings are equal to their SM values, the Higgs boson trilinear self-coupling modifier $κ_λ=λ_3/λ_{3}^\text{SM}$ is constrained in the range $-$1.35 $\leq$$κ_λ$$\leq$ 6.37 at 95% confidence level. Similarly, for the coupling modifier $κ_{2\mathrm{V}}$, which governs the interaction between two vector bosons and two Higgs bosons, we have excluded $κ_{2\mathrm{V}}$ = 0 at more than 5 standard deviations for all values of $κ_λ$. At 95% confidence level assuming other couplings are equal to their SM values, $κ_{2\mathrm{V}}$ is constrained in the range 0.64 $\leq$ $κ_{2\mathrm{V}}$ $\leq$ 1.40. This work also studies HH production in several new physics scenarios, using the Higgs effective field theory (HEFT) framework. The HEFT framework is further exploited to study various ultraviolet complete models with an extended Higgs sector and set constraints on specific parameters. An extrapolation of the results to the integrated luminosity expected after the high-luminosity upgrade of the LHC is reported as well.
Values of the effective Lagrangian couplings for the Higgs Effective field theory benchmarks proposed in Ref. [33].
Values of the effective Lagrangian couplings for the Higgs Effective field theory benchmarks proposed in Ref. [34].
Summary of results for the HH analyses included in this combination. The second column is the observed (expected) 95$\%$ CL upper limit on the inclusive signal strength $r$. The third (fourth) column is the allowed 68$\%$ CL interval for the coupling modifier $\kappa_\lambda$ ($\kappa _{2V}$). The last column indicates whether the analysis is included in the results using the HEFT parametrisation.
The formation of light (anti)nuclei with mass number A of a few units (e.g., d, $^3$He, and $^4$He) in high-energy hadronic collisions presents a longstanding mystery in nuclear physics [1,2]. It is not clear how nuclei bound by a few MeV can emerge in environments characterized by temperatures above 100 MeV [3-5], about 100,000 times hotter than the center of the Sun. Despite extensive studies, this question remained unanswered. The ALICE Collaboration now addresses it with a novel approach using deuteron-pion momentum correlations in proton-proton (pp) collisions at the Large Hadron Collider (LHC). Our results provide model-independent evidence that about 80% of the observed (anti)deuterons are produced in nuclear fusion reactions [6] following the decay of short-lived resonances, such as the $\Delta (1232)$. These findings resolve a crucial gap in our understanding of nucleosynthesis in hadronic collisions. Beyond answering the fundamental question on how nuclei are formed in hadronic collisions, the results can be employed in the modeling of the production of light and heavy nuclei in cosmic rays [7] and dark matter decays [8,9].
Measured $\pi^{+}$–d$\oplus\pi^{-}$–$\overline{\mathrm{d}}$ (left panel) correlation function.
Measured $\pi^{-}$–d$\oplus\pi^{+}$–$\overline{\mathrm{d}}$ (right panel) correlation function.
The extracted kinetic decoupling temperature is derived from $\pi^{+}$–d correlation functions.
A first search for beyond the standard model physics in jet multiplicity patterns of multilepton events is presented, using a data sample corresponding to an integrated luminosity of 138 fb$^{-1}$ of 13 TeV proton-proton collisions recorded by the CMS detector at the LHC. The search uses observed jet multiplicity distributions in one-, two-, and four-lepton events to explore possible enhancements in jet production rate in three-lepton events with and without bottom quarks. The data are found to be consistent with the standard model expectation. The results are interpreted in terms of supersymmetric production of electroweak chargino-neutralino superpartners with cascade decays terminating in prompt hadronic $R$-parity violating interactions.
Distributions of jet multiplicity in a W-enriched selection of one-lepton events.The lower panels show the ratio of observed events (Data) to the total background prediction (Bkg.), with the gray bands representing the statistical uncertainty (Unc.) in the predictions. SM background predictions fall short of the observations in all cases for higher jet multiplicities. Expected RPVq ($m_{{\widetilde{\chi^{\pm}}_{1}}}=m_{{\widetilde{\chi^{0}}_{2}}}=350~$GeV, $m_{{\widetilde{\chi^{0}}_{1}}}=150~$GeV) signal distributions are overlaid for comparison.
Distributions of jet multiplicity in a W-enriched selection of one-lepton events.The lower panels show the ratio of observed events (Data) to the total background prediction (Bkg.), with the gray bands representing the statistical uncertainty (Unc.) in the predictions. SM background predictions fall short of the observations in all cases for higher jet multiplicities. Expected RPVq ($m_{{\widetilde{\chi^{\pm}}_{1}}}=m_{{\widetilde{\chi^{0}}_{2}}}=350~$GeV, $m_{{\widetilde{\chi^{0}}_{1}}}=150~$GeV) signal distributions are overlaid for comparison.
Distributions of jet multiplicity in a Z-enriched selection of two-lepton OnZ events. The lower panels show the ratio of observed events (Data) to the total background prediction (Bkg.), with the gray bands representing the statistical uncertainty (Unc.) in the predictions. SM background predictions fall short of the observations in all cases for higher jet multiplicities. Expected RPVq ($m_{{\widetilde{\chi^{\pm}}_{1}}}=m_{{\widetilde{\chi^{0}}_{2}}}=350~$GeV, $m_{{\widetilde{\chi^{0}}_{1}}}=150~$GeV) signal distributions are overlaid for comparison.
A search for light long-lived particles decaying to displaced jets is presented, using a data sample of proton-proton collisions at a center-of-mass energy of 13.6 TeV, corresponding to an integrated luminosity of 34.7 fb$^{-1}$, collected with the CMS detector at the CERN LHC in 2022. Novel trigger, reconstruction, and machine-learning techniques were developed for and employed in this search. After all selections, the observations are consistent with the background predictions. Limits are presented on the branching fraction of the Higgs boson to long-lived particles that subsequently decay to quark pairs or tau lepton pairs. An improvement by up to a factor of 10 is achieved over previous limits for models with long-lived particle masses smaller than 60 GeV and proper decay lengths smaller than 1 m. The first constraints are placed on the fraternal twin Higgs and folded supersymmetry models, where the lower bounds on the top quark partner mass reach up to 350 GeV for the fraternal twin Higgs model and 250 GeV for the folded supersymmetry model.
The predicted background yields and the number of observed events for the data with $g_{\mathrm{prompt-veto}}>0.985$, shown for different bins of the displacd-dijet GNN score $g_{\mathrm{displaced}}$. Expected signal yields for the $\mathrm{H \to SS}$, $\mathrm{S \to b\overline{b}}$ signature are also shown for models with $m_{\mathrm{S}}=40~\mathrm{GeV}$, and $c \tau_{0}=1$, $10$ or $100\mathrm{mm}$, assuming a branching fraction of $1\%$ for the $\mathrm{H \to SS}$ decay.
The 95% CL upper limits on the branching fraction $\mathcal{B}(\mathrm{H \to SS})$ with $\mathrm{S \to b\overline{b}}$ deacy, for different LLP masses $m_{\mathrm{S}}$ and proper decay lengths $c\tau_{0}$.
The 95% CL upper limits on the branching fraction $\mathcal{B}(\mathrm{H \to SS})$ with $\mathrm{S \to d\overline{d}}$ decay, for different LLP masses $m_{\mathrm{S}}$ and proper decay lengths $c\tau_{0}$.
The first measurement of the inclusive and normalised differential cross sections of single top quark production in association with a W boson in proton-proton collisions at a centre-of-mass energy of 13.6 TeV is presented. The data were recorded with the CMS detector at the LHC in 2022, and correspond to an integrated luminosity of 34.7 fb$^{-1}$. The analysed events contain one muon and one electron in the final state. For the inclusive measurement, multivariate discriminants exploiting the kinematic properties of the events are used to separate the signal from the dominant top quark-antiquark production background. A cross section of 82.3 $\pm$ 2.1 (stat) ${}^{+9.9}_{-9.7}$ (syst) $\pm$ 3.3 (lumi) pb is obtained, consistent with the predictions of the standard model. A fiducial region is defined according to the detector acceptance to perform the differential measurements. The resulting differential distributions are unfolded to particle level and show good agreement with the predictions at next-to-leading order in perturbative quantum chromodynamics.
The distribution of the RF output for events in the 1j1b region. The number of observed events (points) and estimated signal and background events (filled histograms) from the maximum likelihood fit are shown. The vertical bars on the points represent the statistical uncertainty in the data, and the hatched band the total uncertainty in the estimated events after the fit. The lower panels display the ratio of the data to the sum of the estimated events (points) after the fit, with the bands giving the corresponding uncertainties.
Distribution of the RF output for events in the 1j1b region. The number of observed events (points) and estimated signal and background events (filled histograms) before the maximum likelihood fit are shown. The vertical bars on the points represent the statistical uncertainty in the data, and the hatched band the total uncertainty in the estimated events before the fit. The lower panels display the ratio of the data to the sum of the estimated events (points) before the fit, with the bands giving the corresponding uncertainties.
The distribution of the RF output for events in the 2j1b region. The number of observed events (points) and estimated signal and background events (filled histograms) from the maximum likelihood fit are shown. The vertical bars on the points represent the statistical uncertainty in the data, and the hatched band the total uncertainty in the estimated events after the fit. The lower panels display the ratio of the data to the sum of the estimated events (points) after the fit, with the bands giving the corresponding uncertainties.
The pseudorapidity ($\eta$) distributions of charged hadrons are measured using data collected at the highest ever nucleon-nucleon center-of-mass energy of $\sqrt{s_\mathrm{NN}}$ = 5.36 TeV for collisions of lead-lead ions. The data were recorded by the CMS experiment at the LHC in 2022 and correspond to an integrated luminosity of 0.30 $\pm$ 0.03 $\mu$b$^{-1}$. Using the CMS silicon pixel detector, the yields of primary charged hadrons produced in the range $\vert\eta\vert$$\lt$ 2.6 are reported. The evolution of the midrapidity particle density as a function of collision centrality is also reported. In the 5% most central collisions, the charged-hadron $\eta$ density in the range $\vert\eta\vert$ $\lt$ 0.5 is found to be 2032 $\pm$ 91 (syst), with negligible statistical uncertainty. This result is consistent with an extrapolation from nucleus-nucleus collision data at lower center-of-mass energies. Comparisons are made to various Monte Carlo event generators and to previous measurements of lead-lead and xenon-xenon collisions at similar collision energies. These new data detail the dependence of particle production on the collision energy, initial collision geometry, and the size of the colliding nuclei.
Charged-hadron $\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta$ distributions in PbPb collisions at 5.36 TeV for events in the 0--80%, 0--5% and 50--55% centrality class.
Charged-hadron $\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta$ in PbPb collisions at 5.36 TeV at midrapidity as a function of event centrality.
Charged-hadron $\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta/2A$ in PbPb collisions at 5.36 TeV at midrapidity as a function of event centrality.
Measurements of fiducial and total inclusive cross sections for W and Z boson production are presented in proton-proton collisions at $\sqrt{s}$ = 5.02 and 13 TeV. Electron and muon decay modes ($\ell$ = e or $\mu$) are studied in the data collected with the CMS detector in 2017, in dedicated runs with reduced instantaneous luminosity. The data sets correspond to integrated luminosities of 298 $\pm$ 6 pb$^{-1}$ at 5.02 TeV and 206 $\pm$ 5 pb$^{-1}$ at 13 TeV. Measured values of the products of the total inclusive cross sections and the branching fractions at 5.02 TeV are $\sigma$(pp $\to$ W+X) $\mathcal{B}$(W $\to$$\ell\nu$) = 7300 $\pm$ 10 (stat) $\pm$ 60 (syst) $\pm$ 140 (lumi) pb, and $\sigma$(pp $\to$ Z+X) $\mathcal{B}$(Z $\to$$\ell^+\ell^-$) = 669 $\pm$ 2 (stat) $\pm$ 6 (syst) $\pm$ 13 (lumi) pb for the dilepton invariant mass in the range of 60-120 GeV. The corresponding results at 13 TeV are 20480 $\pm$ 10 (stat) $\pm$ 170 (syst) $\pm$ 470 (lumi) pb and 1952 $\pm$ 4 (stat) $\pm$ 18 (syst) $\pm$ 45 (lumi) pb. The measured values agree with cross section calculations at next-to-next-to-leading-order in perturbative quantum chromodynamics. Fiducial and total inclusive cross sections, ratios of cross sections of W$^+$ and W$^-$ production as well as inclusive W and Z boson production, and ratios of these measurements at 5.02 and 13 TeV are reported.
Distributions of $m_T$ in the $W^{+}$ signal selection for e final states for the pp collisions at $\sqrt{s}=$ 5TeV after the maximum likelihood fit. The EW backgrounds include the contributions from DY, $W\to\tau\nu$, and diboson processes.
Distributions of $m_T$ in the $W^{+}$ signal selection for mu final states for the pp collisions at $\sqrt{s}=$ 5TeV after the maximum likelihood fit. The EW backgrounds include the contributions from DY, $W\to\tau\nu$, and diboson processes.
Distributions of $m_T$ in the $W^{+}$ signal selection for e final states for the pp collisions at $\sqrt{s}=$ 13TeV after the maximum likelihood fit. The EW backgrounds include the contributions from DY, $W\to\tau\nu$, and diboson processes.
Forum