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.
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 search is performed for lepton-number-violating $B^-\to D^{(*)+}μ^-μ^-$ decays, using data collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb$^{-1}$. No significant signal is observed, and upper limits are set on the branching fractions, ${\cal B}(B^-\to D^{+}μ^-μ^-) < 4.6 \times 10^{-8}$ and ${\cal B}(B^-\to D^{*+}μ^-μ^-) < 5.9 \times 10^{-8}$, at the 95% confidence level.
Binned efficiencies across the Dalitz plane for $B^- \to D^{+} \mu^- \mu^-$ decay. Here $\mu_1^-$ and $\mu_2^-$ represent the two muons produced in the decay, and the index specifies their ordering in transverse momentum. Efficiencies are normalized to the average over the full simulated sample.
Binned efficiencies across the Dalitz plane for $B^- \to D^{*+} \mu^- \mu^-$ decay. Here $\mu_1^-$ and $\mu_2^-$ represent the two muons produced in the decay, and the index specifies their ordering in transverse momentum. Efficiencies are normalized to the average over the full simulated sample.
A search for exotic Higgs boson decays H $\to$$\mathcal{AA}$, with $\mathcal{A}$$\to$$γγ$ is presented, using events with a semi-merged topology. One of the hypothetical particles, $\mathcal{A}$, is assumed to decay promptly into a semi-merged diphoton system reconstructed as a single photon-like object, while the other $\mathcal{A}$ decays into two resolved photons. The search is performed using proton-proton collision data collected by the CMS experiment at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. The data agree with the standard model background expectation. Upper limits are set on the product of the Higgs boson production cross section and the branching fraction, $σ$(pp $\to$ H)$\mathcal{B}$(H $\to$$\mathcal{AA}$$\to$ 4$γ$), which range from 0.264 to 0.005 pb at 95% confidence level, for $\mathcal{A}$ masses in the range 1 $\lt$ $m_\mathcal{A}$ $\lt$ 15 GeV. These limits are the most stringent to date in the 1$-$5 GeV $m_\mathcal{A}$ range.
The 2D $m_A$ spectra in the final signal region. The unrolled 2D $m_A$ distribution made by scanning along bins of increasing $m_{A2}$ at fixed $m_{A1}$ before incrementing in $m_{A1}$. Only the bins in the $m_{A}$-SR region are included, with the x-axis corresponding to the unrolled bin index of the selected bins, listed sequentially. The data distributions (black points) are plotted against the total predicted background distributions (blue curves) after fitting to the data. The statistical plus systematic uncertainties in the background distribution are plotted as the blue band. The corresponding distributions of simulated $\mathrm{H} \to \mathcal{A} \mathcal{A} \to 4 \gamma$ events for $m_A = $3 (purple curve), 10 (gray curve), and 15 GeV (orange curve) are also overlaid on top. They are each normalized to the value of the expected upper limit to the signal cross section times 50. The lower panels of each plot show the ratio of the observed data over the predicted background as the black points, with the error bars representing the statistical uncertainties in the former. The ratio of the statistical plus systematic uncertainties in the background over the background prediction is shown as the blue band.
1D projections on the $m_{A1}$ axis of the 2D $m_A$ distribution in the final signal region. The data distributions (black points) are plotted against the total predicted background distributions (blue curves) after fitting to the data. The statistical plus systematic uncertainties in the background distribution are plotted as the blue band. The corresponding distributions of simulated $\mathrm{H} \to \mathcal{A} \mathcal{A} \to 4 \gamma$ events for $m_A = $3 (purple curve), 10 (gray curve), and 15 GeV (orange curve) are also overlaid on top. They are each normalized to the value of the expected upper limit to the signal cross section times 50. The lower panels of each plot show the ratio of the observed data over the predicted background as the black points, with the error bars representing the statistical uncertainties in the former. The ratio of the statistical plus systematic uncertainties in the background over the background prediction is shown as the blue band.
1D projections on the $m_{A2}$ axis of the 2D $m_A$ distribution in the final signal region. The data distributions (black points) are plotted against the total predicted background distributions (blue curves) after fitting to the data. The statistical plus systematic uncertainties in the background distribution are plotted as the blue band. The corresponding distributions of simulated $\mathrm{H} \to \mathcal{A} \mathcal{A} \to 4 \gamma$ events for $m_A = $3 (purple curve), 10 (gray curve), and 15 GeV (orange curve) are also overlaid on top. They are each normalized to the value of the expected upper limit to the signal cross section times 50. The lower panels of each plot show the ratio of the observed data over the predicted background as the black points, with the error bars representing the statistical uncertainties in the former. The ratio of the statistical plus systematic uncertainties in the background over the background prediction is shown as the blue band.
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 $ρ_\mathrm{tc} \gtrsim$ 0.15$-$0.5 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.
The postfit pDNN distributions in the SR e 2b2j assuming $m_{H^\pm} = 600$ GeV. Postfit signal for $m_{H^\pm} = 600$ GeV is also shown. Beneath plot the ratio of data to predictions is shown.
The postfit pDNN distributions in the SR $\mu$ 2b2j assuming $m_{H^\pm} = 600$ GeV. Postfit signal for $m_{H^\pm} = 600$ GeV is also shown. Beneath plot the ratio of data to predictions is shown.
The postfit pDNN distributions in the SR e 3b3j assuming $m_{H^\pm} = 600$ GeV. Postfit signal for $m_{H^\pm} = 600$ GeV is also shown. Beneath plot the ratio of data to predictions is shown.
Measurements of the spin correlation coefficients in the beam basis are presented for top quark-antiquark ($\mathrm{t\bar{t}}$) systems produced in proton-proton collisions at $\sqrt{s}$ = 13 TeV collected by the CMS experiment in 2016$-$2018, and corresponding to an integrated luminosity of 138 fb$^{-1}$. The $\mathrm{t\bar{t}}$ system is reconstructed from final states containing an electron or muon, and jets. Together with the previously reported results in the helicity basis, these measurements are used to decompose the system into the Bell and spin eigenstates in various kinematic regions. The spin correlation coefficients are also used to evaluate properties of the $\mathrm{t\bar{t}}$ quantum state, such as the purity, von Neumann entropy, and entanglement. All results are consistent with standard model predictions.
Measured spin correlation coefficients in beam basis for $m(t\bar{t})$ vs. $|cos(\theta)|$ bins
Covariance for spin correlation coefficients in beam basis for $m(t\bar{t})$ vs. $|cos(\theta)|$ bins
Measured spin correlation coefficients in beam basis for $p_{T}(t)$ vs. $|cos(\theta)|$ bins
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.
<jats:title>Abstract</jats:title> <jats:p> The existence of three distinct neutrino flavours, <jats:italic>ν</jats:italic> <jats:sub>e</jats:sub> , <jats:italic>ν</jats:italic> <jats:sub>μ</jats:sub> and <jats:italic>ν</jats:italic> <jats:sub>τ</jats:sub> , is a central tenet of the Standard Model of particle physics <jats:sup>1,2</jats:sup> . Quantum-mechanical interference can allow a neutrino of one initial flavour to be detected sometime later as a different flavour, a process called neutrino oscillation. Several anomalous observations inconsistent with this three-flavour picture have motivated the hypothesis that an additional neutrino state exists, which does not interact directly with matter, termed as ‘sterile’ neutrino, <jats:italic>ν</jats:italic> <jats:sub>s</jats:sub> (refs. <jats:sup>3–9</jats:sup> ). This includes anomalous observations from the Liquid Scintillator Neutrino Detector (LSND) <jats:sup>3</jats:sup> experiment and Mini-Booster Neutrino Experiment (MiniBooNE) <jats:sup>4,5</jats:sup> , consistent with <jats:italic>ν</jats:italic> <jats:sub>μ</jats:sub> → <jats:italic>ν</jats:italic> <jats:sub>e</jats:sub> transitions at a distance inconsistent with the three-neutrino picture. Here we use data obtained from the MicroBooNE liquid-argon time projection chamber <jats:sup>10</jats:sup> in two accelerator neutrino beams to exclude the single light sterile neutrino interpretation of the LSND and MiniBooNE anomalies at the 95% confidence level (CL). Moreover, we rule out a notable portion of the parameter space that could explain the gallium anomaly <jats:sup>6–8</jats:sup> . This is one of the first measurements to use two accelerator neutrino beams to break a degeneracy between <jats:italic>ν</jats:italic> <jats:sub>e</jats:sub> appearance and disappearance, which would otherwise weaken the sensitivity to the sterile neutrino hypothesis. We find no evidence for either <jats:italic>ν</jats:italic> <jats:sub>μ</jats:sub> → <jats:italic>ν</jats:italic> <jats:sub>e</jats:sub> flavour transitions or <jats:italic>ν</jats:italic> <jats:sub>e</jats:sub> disappearance that would indicate non-standard flavour oscillations. Our results indicate that previous anomalous observations consistent with <jats:italic>ν</jats:italic> <jats:sub>μ</jats:sub> → <jats:italic>ν</jats:italic> <jats:sub>e</jats:sub> transitions cannot be explained by introducing a single sterile neutrino state. </jats:p>
14 observation channels used in this analysis. The first 7 channels correspond to the BNB, while the last 7 channels correspond to the NuMI beam. Each set of seven channels is split by reconstructed event type as well as containment in the detector, fully contained (FC) or partially contained (PC). The seven channels in order are $\nu_e$CC FC, $\nu_e$CC PC, $\nu_\mu$CC FC, $\nu_\mu$CC PC, $\nu_\mu$CC $\pi^0$ FC, $\nu_\mu$CC $\pi^0$ PC, and NC $\pi^0$. Each channel contains 25 bins from 0 to 2500 MeV of reconstructed neutrino energy, with an additional overflow bin.
Four $\nu_e$CC observation channels, after constraints from 10 $\nu_\mu$CC and NC $\pi^0$ channels. The four channels in order are BNB $\nu_e$CC FC, BNB $\nu_e$CC PC, NuMI $\nu_e$CC FC, and NuMI $\nu_e$CC PC. Each channel contains 25 bins from 0 to 2500 MeV of reconstructed neutrino energy, with an additional overflow bin.
14 channel covariance matrix showing uncertainties and correlations between bins due to flux uncertainties, cross-section uncertainties, hadron reinteraction uncertainties, detector systematic uncertainties, Monte-Carlo statistical uncertainties, and dirt (outside cryostat) uncertainties. Data statistical uncertainties have not been included, but they can be calculated with the Combined Neyman-Pearson (CNP) method. Each channel contains 25 bins from 0 to 2500 MeV of reconstructed neutrino energy, with an additional overflow bin.
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