A search for the rare η→μ+μ−μ+μ− double-Dalitz decay is performed using a sample of proton-proton collisions, collected by the CMS experiment at the CERN LHC with high-rate muon triggers during 2017 and 2018 and...
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A search for the rare η→μ+μ−μ+μ− double-Dalitz decay is performed using a sample of proton-proton collisions, collected by the CMS experiment at the CERN LHC with high-rate muon triggers during 2017 and 2018 and corresponding to an integrated luminosity of 101 fb−1. A signal having a statistical significance well in excess of 5 standard deviations is observed. Using the η→μ+μ− decay as normalization, the branching fraction b(η→μ+μ−μ+μ−)=[5.0±0.8(stat)±0.7(syst)±0.7(b2μ)]×10−9 is measured, where the last term is the uncertainty in the normalization channel branching fraction. This work achieves an improved precision of over 5 orders of magnitude compared to previous results, leading to the first measurement of this branching fraction, which is found to agree with theoretical predictions.
Video streaming over HTTP through 4G wireless network used for multimedia applications faces many challenges due to fluctuations in network conditions. The existing HTTP Adaptive Streaming (HAS) techniques based on pr...
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Video streaming over HTTP through 4G wireless network used for multimedia applications faces many challenges due to fluctuations in network conditions. The existing HTTP Adaptive Streaming (HAS) techniques based on prediction of buffer state or link bandwidth offer solution to some extent, but if the link condition deteriorates, the adaptation process may reduce the streaming bit rate below an acceptable quality level. In this paper, we propose a machine learning based method, State Action Reward State Action (SARSA) based Quality Adaptation algorithm using Softmax Policy (SbQA-SP), which identifies the current state (Throughput), action (Streaming quality) and reward (current video quality) at client to determine the future state and action of the system. The ITU-T G.1070 recommendation (parametric) modelis embedded in the SbQA-SP to implement adaptation process. The proposed system was implemented on the top of HTTP in a typical internet environment using 4G wireless network and the streaming quality is analyzed using several full reference video metrics. The test results outperformed the existing Q-Learning based video quality adaptation (QbQA) algorithm. For instance, an improvement of 5% in average PSNR and 2 % increase in average SSIM index over the QbQA approach was observed for the live stream.
A search is presented for charged, long-lived supersymmetric particles in final states with one or more disappearing tracks. The search is based on data from proton-proton collisions at a center-of-mass energy of 13 T...
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A search is presented for charged, long-lived supersymmetric particles in final states with one or more disappearing tracks. The search is based on data from proton-proton collisions at a center-of-mass energy of 13 TeV collected with the CMS detector at the CERN LHC between 2016 and 2018, corresponding to an integrated luminosity of 137 fb−1. The search is performed over final states characterized by varying numbers of jets, b-tagged jets, electrons, and muons. The length of signal-candidate tracks in the plane perpendicular to the beam axis is used to characterize the lifetimes of wino- and Higgsino-like charginos produced in the context of the minimal supersymmetric standard model. The dE/dx energy loss of signal-candidate tracks is used to increase the sensitivity to charginos with a large mass and thus a small Lorentz boost. The observed results are found to be statistically consistent with the background-only hypothesis. Limits on the pair-production cross section of gluinos and squarks are presented in the framework of simplified models of supersymmetric particle production and decay, and for electroweakino production based on models of wino and Higgsino dark matter. The limits presented are the most stringent to date for scenarios with light third-generation squarks and a wino- or Higgsino-like dark matter candidate capable of explaining the observed dark matter relic density.
A search for the production of a top quark in association with a photon and additional jets via flavor changing neutral current interactions is presented. The analysis uses proton-proton collision data recorded by the...
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A search for the production of a top quark in association with a photon and additional jets via flavor changing neutral current interactions is presented. The analysis uses proton-proton collision data recorded by the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb−1. The search is performed by looking for processes where a single top quark is produced in association with a photon, or a pair of top quarks where one of the top quarks decays into a photon and an up or charm quark. Events with an electron or a muon, a photon, one or more jets, and missing transverse momentum are selected. Multivariate analysis techniques are used to discriminate signal and standard model background processes. No significant deviation is observed over the predicted background. Observed (expected) upper limits are set on the branching fractions of top quark decays: b(t→uγ)<0.95×10−5 (1.20×10−5) and b(t→cγ)<1.51×10−5 (1.54×10−5) at 95% confidence level, assuming a single nonzero coupling at a time. The obtained limit for b(t→uγ) is similar to the current best limit, while the limit for b(t→cγ) is significantly tighter than previous results.
Differential cross sections are measured for the standard model Higgs boson produced in association with vector bosons (W, Z) and decaying to a pair of b quarks. Measurements are performed within the framework of the ...
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Differential cross sections are measured for the standard model Higgs boson produced in association with vector bosons (W, Z) and decaying to a pair of b quarks. Measurements are performed within the framework of the simplified template cross sections. The analysis relies on the leptonic decays of the W and Z bosons, resulting in final states with 0, 1, or 2 electrons or muons. The Higgs boson candidates are either reconstructed from pairs of resolved b-tagged jets, or from single large-radius jets containing the particles arising from two b quarks. Proton-proton collision data at s=13 TeV, collected by the CMS experiment in 2016–2018 and corresponding to a total integrated luminosity of 138 fb−1, are analyzed. The inclusive signal strength, defined as the product of the observed production cross section and branching fraction relative to the standard model expectation, combining all analysis categories, is found to be μ=1.15−0.20+0.22. This corresponds to an observed (expected) significance of 6.3 (5.6) standard deviations.
The observation of WWγ production in proton-proton collisions at a center-of-mass energy of 13 TeV with an integrated luminosity of 138 fb−1 is presented. The observed (expected) significance is 5.6 (5.1) standard d...
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The observation of WWγ production in proton-proton collisions at a center-of-mass energy of 13 TeV with an integrated luminosity of 138 fb−1 is presented. The observed (expected) significance is 5.6 (5.1) standard deviations. Events are selected by requiring exactly two leptons (one electron and one muon) of opposite charge, moderate missing transverse momentum, and a photon. The measured fiducial cross section for WWγ is 5.9±0.8(stat)±0.8(syst)±0.7(modeling) fb, in agreement with the next-to-leading order quantum chromodynamics prediction. The analysis is extended with a search for the associated production of the Higgs boson and a photon, which is generated by a coupling of the Higgs boson to light quarks. The result is used to constrain the Higgs boson couplings to light quarks.
The results of a search for stealth supersymmetry in final states with two photons and jets, targeting a phase space region with low missing transverse momentum (pTmiss), are reported. The study is based on a sample o...
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The results of a search for stealth supersymmetry in final states with two photons and jets, targeting a phase space region with low missing transverse momentum (pTmiss), are reported. The study is based on a sample of proton-proton collisions at s=13 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb−1. As LHC results continue to constrain the parameter space of the minimal supersymmetric standard model, the low pTmiss regime is increasingly valuable to explore. To estimate the backgrounds due to standard model processes in such events, we apply corrections derived from simulation to an estimate based on a control selection in data. The results are interpreted in the context of simplified stealth supersymmetry models with gluino and squark pair production. The observed data are consistent with the standard model predictions, and gluino (squark) masses of up to 2150 (1850) GeV are excluded at the 95% confidence level.
A search for long-lived particles (LLPs) decaying in the CMS muon detectors is presented. A data sample of proton-proton collisions at s=13 TeV corresponding to an integrated luminosity of 138 fb−1, recorded at the ...
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A search for long-lived particles (LLPs) decaying in the CMS muon detectors is presented. A data sample of proton-proton collisions at s=13 TeV corresponding to an integrated luminosity of 138 fb−1, recorded at the LHC in 2016–2018, is used. The decays of LLPs are reconstructed as high multiplicity clusters of hits in the muon detectors. In the context of twin Higgs models, the search is sensitive to LLP masses from 0.4 to 55 GeV and a broad range of LLP decay modes, including decays to hadrons, τ leptons, electrons, or photons. No excess of events above the standard model background is observed. The most stringent limits to date from LHC data are set on the branching fraction of the Higgs boson decay to a pair of LLPs with masses below 10 GeV. This search also provides the best limits for various intervals of LLP proper decay length and mass. Finally, this search sets the first limits at the LHC on a dark quantum chromodynamic sector whose particles couple to the Higgs boson through gluon, Higgs boson, photon, vector, and dark-photon portals, and is sensitive to branching fractions of the Higgs boson to dark quarks as low as 2×10−3.
A search is described for the production of a pair of bottom-type vectorlike quarks (b VLQs) with mass greater than 1000 GeV. Each b VLQ decays into a b quark and a Higgs boson, a b quark and a Z boson, or a t quark a...
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A search is described for the production of a pair of bottom-type vectorlike quarks (b VLQs) with mass greater than 1000 GeV. Each b VLQ decays into a b quark and a Higgs boson, a b quark and a Z boson, or a t quark and a W boson. This analysis considers both fully hadronic final states and those containing a charged lepton pair from a Z boson decay. The products of the H→bbboson decay and of the hadronic Z or W boson decays can be resolved as two distinct jets or merged into a single jet, so the final states are classified by the number of reconstructed jets. The analysis uses data corresponding to an integrated luminosity of 138 fb−1 collected in proton-proton collisions at s=13 TeV with the CMS detector at the LHC from 2016 to 2018. No excess over the expected background is observed. Lower limits are set on the b VLQ mass at the 95% confidence level. These depend on the b VLQ branching fractions and are 1570 and 1540 GeV for 100% b→bH and 100% b→bZ, respectively. In most cases, the mass limits obtained exceed previous limits by at least 100 GeV.
A combination of the results of several searches for the electroweak production of the supersymmetric partners of standard model bosons, and of charged leptons, is presented. All searches use proton-proton collision d...
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A combination of the results of several searches for the electroweak production of the supersymmetric partners of standard model bosons, and of charged leptons, is presented. All searches use proton-proton collision data at s=13 TeV recorded with the CMS detector at the LHC in 2016–2018. The analyzed data correspond to an integrated luminosity of up to 137 fb−1. The results are interpreted in terms of simplified models of supersymmetry. Two new interpretations are added with this combination: a model spectrum with the bino as the lightest supersymmetric particle together with mass-degenerate Higgsinos decaying to the bino and a standard model boson, and the compressed-spectrum region of a previously studied model of slepton pair production. Improved analysis techniques are employed to optimize sensitivity for the compressed spectra in the wino and slepton pair production models. The results are consistent with expectations from the standard model. The combination provides a more comprehensive coverage of the model parameter space than the individual searches, extending the exclusion by up to 125 GeV, and also targets some of the intermediate gaps in the mass coverage.
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