A search is presented for narrow resonances, with a mass between 0.6 and 1.8 TeV, decaying to pairs of jets, in proton-proton collisions at $\sqrt{s}$ = 13 TeV. The search is performed using dijets that are reconstructed, selected, and recorded in a compact form by the high-level trigger in a technique referred to as "data scouting", from data collected in 2016$-$2018 corresponding to an integrated luminosity of 177 fb$^{-1}$. The dijet mass spectra are well described by a smooth parameterization, and no significant evidence for the production of new particles is observed. Model-independent upper limits are presented on the product of the cross section, branching fraction, and acceptance for the individual cases of narrow quark-quark, quark-gluon, and gluon-gluon resonances, and are compared to the predictions from a variety of models of narrow dijet resonance production. The upper limit on the coupling of a dark matter mediator to quarks is presented as a function of the mediator mass. The sensitivity of this search goes beyond what is expected from statistical scaling with the integrated luminosity alone, as a consequence of the use of fewer parameters in the background function within a more robust statistical procedure.
Observed differential dijet spectrum using the 2016 data.
Observed differential dijet spectrum using the 2017 data.
Observed differential dijet spectrum using the 2018 data.
The ratio between the B$_\mathrm{c}^+$$\to$ J/$ψ$$τ^+ν_τ$ and B$_\mathrm{c}^+$$\to$ J/$ψ$$μ^+ν_μ$ branching fractions is measured using a data sample of proton-proton collisions collected by CMS at a center-of-mass energy of 13 TeV in the years 2016$-$2018 and corresponding to an integrated luminosity of 138 fb$^{-1}$. The J$/ψ$ meson is identified through its J$/ψ$$\to$$μ^+μ^-$ decay and the tau lepton is reconstructed in the hadronic three-prong final state. The measured ratio of branching fractions in this tau decay mode, $\mathcal{R}^\text{had}_{\mathrm{J}/ψ}$ = 1.04$_{-0.44}^{+0.50}$, is combined with the previous analysis based on the $τ^+$$\to$$μ^+ν_μ\barν_τ$ leptonic decay channel, leading to $\mathcal{R}_{\mathrm{J}/ψ}$ = 0.49 $\pm$ 0.26. As this result is consistent with the standard model prediction of 0.258 $\pm$ 0.004, no evidence of lepton flavor universality violation is found.
Measured R(J/psi) ratio
A search is presented for emerging jets using 140 fb$^{-1}$ of proton-proton collision data at $\sqrt{s} = 13$ TeV, collected by the ATLAS experiment between 2015 and 2018. The search looks for the existence of a dark sector with symmetries similar to those in quantum chromodynamics. This dark sector is populated with dark quarks, which undergo showering similar to quarks in the Standard Model, leading to a high multiplicity of long-lived dark hadrons within a dark jet. These dark hadrons subsequently decay to Standard Model particles via a new heavy scalar mediating particle $ϕ$. This results in jets which contain multiple displaced vertices, known as emerging jets. This analysis targets four-jet topologies, with two emerging jets and two Standard Model jets, resulting from the decay of pair-produced scalar mediators. No significant excess above the Standard Model background is observed. For dark pion proper decay lengths of 20 mm, mediator masses are excluded between 1 TeV and 2 TeV assuming a dark pion mass of 20 GeV.
Comparison of the data with N<sub>DV</sub> > 1 and the estimated background in the SR using the modified ABCD method. The division between the SR and CR is shown by the vertical dashed line. In the final fit, the bins with R > 0.4 are combined into a single bin. Three selected signal samples are included for comparison.
95% CL upper limits as a function of (left) cτ<sub>π<sub>d</sub></sub> and (right) M<sub>φ</sub>. The upper plots show the expected and observed limits on σ(pp →φ<sup>†</sup>φ) for m<sub>π<sub>d</sub></sub> = 20 GeV: (a) using M<sub>φ</sub> = 1.6 TeV and (b) using cτ<sub>π<sub>d</sub></sub> = 20 mm. The lower plots show a comparison of the observed limits for all three dark pion masses: (c) using M<sub>φ</sub> = 1.4 TeV, and (d) using cτ<sub>π<sub>d</sub></sub> = 1 mm. The mediator mass-dependent theoretical cross-section is given with the band corresponding to the uncertainty from NNLL-Fast.
95% CL upper limits as a function of (left) cτ<sub>π<sub>d</sub></sub> and (right) M<sub>φ</sub>. The upper plots show the expected and observed limits on σ(pp →φ<sup>†</sup>φ) for m<sub>π<sub>d</sub></sub> = 20 GeV: (a) using M<sub>φ</sub> = 1.6 TeV and (b) using cτ<sub>π<sub>d</sub></sub> = 20 mm. The lower plots show a comparison of the observed limits for all three dark pion masses: (c) using M<sub>φ</sub> = 1.4 TeV, and (d) using cτ<sub>π<sub>d</sub></sub> = 1 mm. The mediator mass-dependent theoretical cross-section is given with the band corresponding to the uncertainty from NNLL-Fast.
A measurement is presented of the electroweak vector boson scattering production of ZV (V = W, Z) boson pairs associated with two jets in proton-proton collisions at a center-of-mass energy of 13 TeV. The data, corresponding to an integrated luminosity of 138 fb$^{-1}$, were collected at the CERN LHC with the CMS detector during the 2016$-$2018 data-taking period. The analysis targets final states with a pair of isolated electrons or muons from Z boson decays and three or four jets, depending on the momentum of the vector boson that decays into quarks. Signal strength is measured for events characterized by a large invariant mass of two forward jets with a wide pseudorapidity gap between them. The electroweak production of ZV in association with two jets is measured with an observed (expected) significance of 1.3 (1.8) standard deviations. A combination of the analyses of ZV channel and the previously published WV channel in the lepton plus jets final state places constraints on effective field theory parameters that describe anomalous electroweak production of WW, WZ, and ZZ boson pairs in association with two jets. Several world best limits are set on anomalous quartic gauge couplings in terms of dimension-8 standard model effective field theory operators.
Distributions of DNN score for the data and post-fit backgrounds (stacked histograms), in the SRs of the ZV channel for the b tag (left) and the b veto (right) channels, for the resolved (merged) category in the first (second) row. The post-fit VBS EW ZV signal is shown overlaid as a red solid line. The overflow is included in the last bin. The lower panels show the ratios of the data to the pre-fit background prediction and post-fit background yield as red open squares and blue points, respectively. The gray band in the lower panels indicates the systematic component of the post-fit background uncertainty. The vertical bars on the data points represent statistical uncertainties. The last bin includes overflow.
Distributions of DNN score for the data and post-fit backgrounds (stacked histograms), in the SRs of the ZV channel for the b tag (left) and the b veto (right) channels, for the resolved (merged) category in the first (second) row. The post-fit VBS EW ZV signal is shown overlaid as a red solid line. The overflow is included in the last bin. The lower panels show the ratios of the data to the pre-fit background prediction and post-fit background yield as red open squares and blue points, respectively. The gray band in the lower panels indicates the systematic component of the post-fit background uncertainty. The vertical bars on the data points represent statistical uncertainties. The last bin includes overflow.
Distributions of DNN score for the data and post-fit backgrounds (stacked histograms), in the SRs of the ZV channel for the b tag (left) and the b veto (right) channels, for the resolved (merged) category in the first (second) row. The post-fit VBS EW ZV signal is shown overlaid as a red solid line. The overflow is included in the last bin. The lower panels show the ratios of the data to the pre-fit background prediction and post-fit background yield as red open squares and blue points, respectively. The gray band in the lower panels indicates the systematic component of the post-fit background uncertainty. The vertical bars on the data points represent statistical uncertainties. The last bin includes overflow.
Differential top quark pair production cross sections are measured in the dilepton final states e$^+$e$^-$, $μ^+μ^-$, and e$^\pmμ^\mp$, as a function of kinematic variables of the two-neutrino system: the transverse momentum $p_\mathrm{T}^{νν}$ of the dineutrino system, the minimum distance in azimuthal angle between $\vec{p}_\mathrm{T}^{\,νν}$ and leptons, and in two dimensions in bins of both observables. The measurements are performed using CERN LHC proton-proton collisions at $\sqrt{s}$ = 13 TeV, recorded by the CMS detector between 2016 and 2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The measured cross sections are unfolded to the particle level using an unregularized least squares method. Results are compared with predictions by the standard model of particle physics, and found to be in agreement with theoretical calculations as well as Monte Carlo simulations.
Data and MC simulation yields after the event selection, combined for all data-taking periods and split by channels. The uncertainties on the expected yields include systematic and statistical uncertainties. The relative contribution in percent of each process to the total expected yield of a channel is given in parentheses.
Observed (black markers) and expected distributions of leading lepton $p_{T}$ after event selection. The hatched (grey) areas denote the systematic (total) uncertainties in the expected yields. Events from all data-taking periods and all channels are combined. The lower panel of each plot shows the ratio between observed and expected distributions. The last bin includes all events above the plotted range. The entry Background corresponds to the sum of all the SM predictions.
Observed (black markers) and expected distributions of leading jet $p_{T}$ after event selection. The hatched (grey) areas denote the systematic (total) uncertainties in the expected yields. Events from all data-taking periods and all channels are combined. The lower panel of each plot shows the ratio between observed and expected distributions. The last bin includes all events above the plotted range. The entry Background corresponds to the sum of all the SM predictions.
A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, H $\to$$\mathrm{c\bar{c}}$, produced in association with a top quark-antiquark pair ($\mathrm{t\bar{t}}$H) is presented. The search is performed with data from proton-proton collisions at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. Advanced machine learning techniques are employed for jet flavor identification and event classification. The Higgs boson decay to a bottom quark-antiquark pair is measured simultaneously and the observed $\mathrm{t\bar{t}}$H (H $\to$$\mathrm{b\bar{b}}$) event rate relative to the standard model expectation is 0.91 $^{+0.26}_{-0.22}$. The observed (expected) upper limit on the product of production cross section and branching fraction $σ$($\mathrm{t\bar{t}}$H) $\mathcal{B}$(H $\to$$\mathrm{c\bar{c}}$) is 0.11 (0.13) pb at 95% confidence level, corresponding to 7.8 (8.7) times the standard model prediction. When combined with the previous search for H $\to$ $\mathrm{c\bar{c}}$ via associated production with a W or Z boson, the observed (expected) 95% confidence interval on the Higgs-charm Yukawa coupling modifier, $κ_\mathrm{c}$, is $\lvert{κ_\mathrm{c}}\rvert$ $\lt$ 3.5 (2.7), the most stringent constraint to date.
Upper limits on the signal strength for $\text{H}\to\text{c}\overline{\text{c}}$ decays with respect to the standard model expectation of unity.
Upper limits on the signal strength for $\text{t}\overline{\text{t}}\text{H}(\text{H}\to\text{c}\overline{\text{c}})$ decays with respect to the standard model expectation of unity.
Signal strength and significance for $\text{t}\overline{\text{t}}\text{H}(\text{H}\to\text{b}\overline{\text{b}})$ decays with respect to the standard model expectation of unity.
This paper presents a search for new physics through the process where a new massive particle, X, decays into a Higgs boson and a second particle, Y. The Higgs boson subsequently decays into a bottom quark-antiquark pair, reconstructed as a single large-radius jet. The decay products of Y are also assumed to produce a single large-radius jet. The identification of the Y particle is enhanced by computing the anomaly score of its candidate jet using an autoencoder, which measures deviations from typical QCD multijet jets. This allows a simultaneous search for multiple Y decay scenarios within a single analysis. In the main benchmark process, Y is a scalar particle that decays into W$^+$W$^-$. Two other benchmark processes are also considered, where Y is a scalar particle decaying into a light quark-antiquark pair, or into a top quark-antiquark pair. The last benchmark considers Y as a hadronically decaying top quark, arising from the decay of a vector-like quark into a top quark and a Higgs boson. Data recorded by the CMS experiment at a center-of-mass energy of 13 TeV in 2016$-$2018, and corresponding to an integrated luminosity of 138 fb$^{-1}$, are analyzed. No significant excess is observed, and upper limits on the benchmark signal cross section for various masses of X and Y, at 95% confidence level, are placed.
The $m_{jj}$ and $m_{J}$ projections for the number of observed events (black markers) compared with the backgrounds estimated in the fit to the data (filled histograms) in the CR. Pass and Fail categories are shown. The high level of agreement between the model and the data in the Fail region is due to the nature of the background estimate. The lower panels show the ``Pull'' defined as $(\text{observed events}{-}\text{expected events})/\sqrt{\smash[b]{\sigma_\text{obs}^{2} + \sigma_\text{exp}^{2}}}$, where $\sigma_\text{obs}$ and $\sigma_\text{exp}$ are the total uncertainties in the observation and the background estimation, respectively.
The $m_{jj}$ and $m_{J}$ projections for the number of observed events (black markers) compared with the backgrounds estimated in the fit to the data (filled histograms) in the CR. Pass and Fail categories are shown. The high level of agreement between the model and the data in the Fail region is due to the nature of the background estimate. The lower panels show the ``Pull'' defined as $(\text{observed events}{-}\text{expected events})/\sqrt{\smash[b]{\sigma_\text{obs}^{2} + \sigma_\text{exp}^{2}}}$, where $\sigma_\text{obs}$ and $\sigma_\text{exp}$ are the total uncertainties in the observation and the background estimation, respectively.
The $m_{jj}$ and $m_{J}$ projections for the number of observed events (black markers) compared with the backgrounds estimated in the fit to the data (filled histograms) in the CR. Pass and Fail categories are shown. The high level of agreement between the model and the data in the Fail region is due to the nature of the background estimate. The lower panels show the ``Pull'' defined as $(\text{observed events}{-}\text{expected events})/\sqrt{\smash[b]{\sigma_\text{obs}^{2} + \sigma_\text{exp}^{2}}}$, where $\sigma_\text{obs}$ and $\sigma_\text{exp}$ are the total uncertainties in the observation and the background estimation, respectively.
The angular distributions of Drell-Yan lepton pairs provide sensitive probes of the underlying dynamics of quantum chromodynamics (QCD) effects in vector-boson production. This paper presents for the first time the measurement of the full set of angular coefficients together with the differential cross-section as a function of the transverse momentum of the $W$ boson, in the full phase space of the decay leptons. The measurements are performed separately for the $W^-$ and $W^+$ channels. The analysis uses proton-proton collision data recorded by the ATLAS experiment at the Large Hadron Collider in 2017 and 2018, during special low-luminosity runs with a reduced number of interactions per bunch crossings (pile-up). The data correspond to an integrated luminosity of $338$ pb$^{-1}$ at a centre-of-mass energy of $\sqrt{s} = 13$ TeV. The low pile-up conditions enable an optimised reconstruction of the $W$ boson transverse momentum. All results agree with theory predictions incorporating finite-order QCD corrections up to next-to-next-to-leading-order in the strong coupling constant, $α_S$.
The measured angular coefficients for $W^-$ in bins of the $p_T$ of the W.
The measured angular coefficients for $W^+$ in bins of the $p_T$ of the W.
The measured differential cross-section for $W^-$ in bins of the $p_T$ of the $W$.
Utilizing the 2012 transversely polarized proton data from the Relativistic Heavy Ion Collider at Brookhaven National Laboratory, the forward $η$-meson transverse single-spin asymmetry ($A_N$) was measured for $p^{\uparrow}+p$ collisions at $\sqrt{s}=200$ GeV as a function of Feynman-x ($x_F$) for $0.2<|x_F|<0.8$ and transverse momentum ($p_T$) for $1.0<p_T<5.0$ GeV/$c$. Large asymmetries at positive $x_F$ are observed ($\left<A_N\right>=0.086 \pm 0.019$), agreeing well with previous measurements of $π^{0}$ and $η$$A_N$, but with reach to higher $x_F$ and $p_T$. The contribution of initial-state spin-momentum correlations to the asymmetry, as calculated in the collinear twist-3 framework, appears insufficient to describe the data and suggests a significant impact on the asymmetry from fragmentation.
The $\eta$ meson transverse single-spin asymmetry vs. Feynman-x at forward rapidity in pp collisions at center-of-mass energy 200 GeV.
The $\eta$ meson transverse single-spin asymmetry vs. $\eta$ meson $p_T$ at forward rapidity in pp collisions at center-of-mass energy 200 GeV.
This Letter reports the first measurement of photonuclear D$^0$ meson production in ultraperipheral heavy ion collisions. The study is performed using lead-lead collision data, with an integrated luminosity of 1.38 nb$^{-1}$, 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 D$^0$ mesons are reconstructed via the D$^0$$\to$ K$^-$$π^+$ decay channel, with the cross section measured as a function of D$^0$ 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 $x$ (relative to the nucleon) ranging approximately from a few 10$^{-4}$ to 10$^{-2}$ for different hard energy scale $Q^2$ selections.
The mass distribution of D$^{0}$ decaying to K$^{-}$ and $\pi^{+}$ for $5 < p_{\mathrm{T}} < 8$ GeV and $0.0 < y < 1.0$ in 0nXn ultraperipheral PbPb collisions.
The d$^{2}\sigma$/dydp$_{\mathrm{T}}$ production cross section of D$^{0}$ for $2 < p_{\mathrm{T}} < 5$ GeV in ultraperipheral PbPb collisions.
The d$^{2}\sigma$/dydp$_{\mathrm{T}}$ production cross section of D$^{0}$ for $5 < p_{\mathrm{T}} < 8$ GeV in ultraperipheral PbPb collisions.
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