A search for long-lived particles decaying to displaced, nonprompt jets and missing transverse momentum is presented. The data sample corresponds to an integrated luminosity of 137 fb$^{-1}$ of ...proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC in 2016-2018. Candidate signal events containing nonprompt jets are identified using the timing capabilities of the CMS electromagnetic calorimeter. The results of the search are consistent with the background prediction and are interpreted using a gauge-mediated supersymmetry breaking reference model with a gluino next-to-lightest supersymmetric particle. In this model, gluino masses up to 2100, 2500, and 1900 GeV are excluded at 95% confidence level for proper decay lengths of 0.3, 1, and 100 m, respectively. These are the best limits to date for such massive gluinos with proper decay lengths greater than $\sim$0.5 m.
A search is conducted for new physics in final states containing a photon and missing transverse momentum in proton-proton collisions at $ \sqrt{s}=13 $ TeV, using the data collected in 2016 by the ...CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. No deviations from the predictions of the standard model are observed. The results are interpreted in the context of dark matter production and models containing extra spatial dimensions, and limits on new physics parameters are calculated at 95% confidence level. For the two simplified dark matter production models considered, the observed (expected) lower limits on the mediator masses are both 950 (1150) GeV for 1 GeV dark matter mass. For an effective electroweak-dark matter contact interaction, the observed (expected) lower limit on the suppression parameter Λ is 850 (950) GeV. Values of the effective Planck scale up to 2.85–2.90 TeV are excluded for between 3 and 6 extra spatial dimensions.
Results are reported from a search for new particles that decay into a photon and two gluons, in events with jets. Novel jet substructure techniques are developed that allow photons to be identified ...in an environment densely populated with hadrons. The analyzed proton-proton collision data were collected by the CMS experiment at the LHC, in 2016 at s=13 TeV, and correspond to an integrated luminosity of 35.9 fb-1. The spectra of total transverse hadronic energy of candidate events are examined for deviations from the standard model predictions. No statistically significant excess is observed over the expected background. The first cross section limits on new physics processes resulting in such events are set. The results are interpreted as upper limits on the rate of gluino pair production, utilizing a simplified stealth supersymmetry model. The excluded gluino masses extend up to 1.7 TeV, for a neutralino mass of 200 GeV and exceed previous mass constraints set by analyses targeting events with isolated photons.
A search for the production of events containing three W bosons predicted by the standard model is reported. The search is based on a data sample of proton-proton collisions at a center-of-mass ...energy of 13 TeV recorded by the CMS experiment at the CERN LHC and corresponding to a total integrated luminosity of 35.9 fb$^{-1}$. The search is performed in final states with three leptons (electrons or muons), or with two same-charge leptons plus two jets. The observed (expected) significance of the signal for W$^\pm$W$^\pm$W$^\mp$ production is 0.60 (1.78) standard deviations, and the ratio of the measured signal yield to that expected from the standard model is 0.34$^{+0.62}_{-0.34}$. Limits are placed on three anomalous quartic gauge couplings and on the production of massive axion-like particles.
Results of a search for nonresonant production of Higgs boson pairs, with each Higgs boson decaying to a $ \mathrm{b}\overline{\mathrm{b}} $ pair, are presented. This search uses data from ...proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{−1}$, collected by the CMS detector at the LHC. No signal is observed, and a 95% confidence level upper limit of 847 fb is set on the cross section for standard model nonresonant Higgs boson pair production times the squared branching fraction of the Higgs boson decay to a $ \mathrm{b}\overline{\mathrm{b}} $ pair. The same signature is studied, and upper limits are set, in the context of models of physics beyond the standard model that predict modified couplings of the Higgs boson.
The pseudorapidity distributions of dijets as functions of their average transverse momentum $(p_{T}^{ave})$ are measured in proton-lead ($pPb$) and proton-proton ($pp$) collisions. The data samples ...were collected by the CMS experiment at the CERN LHC, at a nucleon-nucleon center-of-mass energy of 5.02 TeV. A significant modification of the $pPb$ spectra with respect to the $pp$ spectra is observed in all $p_{T}^{ave}$ intervals investigated. The ratios of the $pPb$ and $pp$ distributions are compared to next-to-leading order perturbative quantum chromodynamics calculations with unbound nucleon and nuclear parton distribution functions (PDFs). These results give the first evidence that the gluon PDF at large Bjorken $x$ in lead ions is strongly suppressed with respect to the PDF in unbound nucleons.
A search for exotic Higgs boson decays to light pseudoscalars in the final state of two muons and two τ leptons is performed using proton-proton collision data recorded by the CMS experiment at the ...LHC at a center-of-mass energy of 13 TeV in 2016, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. Masses of the pseudoscalar boson between 15.0 and 62.5 GeV are probed, and no significant excess of data is observed above the prediction of the standard model. Upper limits are set on the branching fraction of the Higgs boson to two light pseudoscalar bosons in different types of two-Higgs-doublet models extended with a complex scalar singlet.
The differential yields of charged particles having pseudorapidity within |η| < 1 are measured using xenon-xenon (XeXe) collisions at $ \sqrt{s_{\mathrm{NN}}} = 5.44 $ TeV. The data, corresponding to ...an integrated luminosity of 3.42 μb$^{−1}$, were collected in 2017 by the CMS experiment at the LHC. The yields are reported as functions of collision centrality and transverse momentum, p$_{T}$, from 0.5 to 100 GeV. A previously reported p$_{T}$ spectrum from proton-proton collisions at $ \sqrt{s}=5.02 $ TeV is used for comparison after correcting for the difference in center-of-mass energy. The nuclear modification factors using this reference, R$_{AA}^{*}$ , are constructed and compared to previous measurements and theoretical predictions. In head-on collisions, the R$_{AA}^{*}$ has a value of 0.17 in the p$_{T}$ range of 6–8 GeV, but increases to approximately 0.7 at 100 GeV. Above ≈6 GeV, the XeXe data show a notably smaller suppression than previous results for lead-lead (PbPb) collisions at $ \sqrt{s_{\mathrm{NN}}}=5.02 $ TeV when compared at the same centrality (i.e., the same fraction of total cross section). However, the XeXe suppression is slightly greater than that for PbPb in events having a similar number of participating nucleons.
The $\chi_\mathrm{b1}$(3P) and $\chi_\mathrm{b2}$(3P) states are observed through their $\Upsilon$(3S) $\gamma$ decays, using an event sample of proton-proton collisions collected by the CMS ...experiment at the CERN LHC. The data were collected at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 80.0 fb$^{-1}$. The $\Upsilon$(3S) mesons are identified through their dimuon decay channel, while the low-energy photons are detected after converting to e$^+$e$^-$ pairs in the silicon tracker, leading to a $\chi_\mathrm{b}$(3P) mass resolution of 2.2 MeV. This is the first time that the $J =$ 1 and 2 states are well resolved and their masses individually measured: 10$\,$513.42 $\pm$ 0.41 (stat) $\pm$ 0.18 (syst) MeV and 10$\,$524.02 $\pm$ 0.57 (stat) $\pm$ 0.18 (syst) MeV; they are determined with respect to the world-average value of the $\Upsilon$(3S) mass, which has an uncertainty of 0.5 MeV. The mass splitting is measured to be 10.60 $\pm$ 0.64 (stat) $\pm$ 0.17 (syst) MeV.
Results are reported from a search for long-lived particles in proton-proton collisions at s=13 TeV delivered by the CERN LHC and collected by the CMS experiment. The data sample, which was recorded ...during 2015 and 2016, corresponds to an integrated luminosity of 38.5 fb-1. This search uses benchmark signal models in which long-lived particles are pair-produced and each decays into two or more quarks, leading to a signal with multiple jets and two displaced vertices composed of many tracks. No events with two well-separated high-track-multiplicity vertices are observed. Upper limits are placed on models of R-parity violating supersymmetry in which the long-lived particles are neutralinos or gluinos decaying solely into multijet final states or top squarks decaying solely into dijet final states. For neutralino, gluino, or top squark masses between 800 and 2600 GeV and mean proper decay lengths between 1 and 40 mm, the analysis excludes cross sections above 0.3 fb at 95% confidence level. Gluino and top squark masses are excluded below 2200 and 1400 GeV, respectively, for mean proper decay lengths between 0.6 and 80 mm. A method is provided for extending the results to other models with pair-produced long-lived particles.
