6,924 research outputs found

    Observation of Two Excited B\u3csup\u3e+\u3c/sup\u3e\u3csub\u3ec\u3c/sub\u3e States and Measurement of the B\u3csup\u3e+\u3c/sup\u3e\u3csub\u3ec\u3c/sub\u3e (2S) Mass in \u3ci\u3epp\u3c/i\u3e Collisions at √s = 13 TeV

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    Signals consistent with the B+c (2S) and B*c+(2S) states are observed in proton-proton collisions at √s = 13 TeV, in an event sample corresponding to an integrated luminosity of 143 fb−1, collected by the CMS experiment during the 2015–2018 LHC running periods. These excited []c states are observed in the B+c π+π− invariant mass spectrum, with the ground state B+c reconstructed through its decay to J/ψπ+. The two states are reconstructed as two well-resolved peaks, separated in mass by 29.1 ± 1.5(stat) ± 0.7(syst) MeV. The observation of two peaks, rather than one, is established with a significance exceeding five standard deviations. The mass of the B+c (2S) meson is measured to be 6871.0 ± 1.2(stat) ± 0.8(syst) ± 0.8(B+c) MeV, where the last term corresponds to the uncertainty in the world-average B+c mass

    Search for the Higgs Boson Decaying to Two Muons in Proton-Proton Collisions at √s =13 TeV

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    A search for the Higgs boson decaying to two oppositely charged muons is presented using data recorded by the CMS experiment at the CERN LHC in 2016 at a center-of-mass energy √s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. Data are found to be compatible with the predicted background. For a Higgs boson with a mass of 125.09 GeV, the 95% confidence level observed (background-only expected) upper limit on the production cross section times the branching fraction to a pair of muons is found to be 3.0 (2.5) times the standard model expectation. In combination with data recorded at center-of-mass energies √s = 7 and 8 TeV, the background-only expected upper limit improves to 2.2 times the standard model value with a standard model expected significance of 1.0 standard deviation. The corresponding observed upper limit is 2.9 with an observed significance of 0.9 standard deviation. This corresponds to an observed upper limit on the standard model Higgs boson branching fraction to muons of 6.4 × 10−4 and to an observed signal strength of 1.0 ± 1.0(stat) ± 0.1(syst)

    Search for Dark Matter Particles Produced in Association with a Top Quark Pair at √s =13 TeV

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    A search is performed for dark matter particles produced in association with a top quark pair in proton-proton collisions at √s = 13 TeV. The data correspond to an integrated luminosity of 35.9 fb−1 recorded by the CMS detector at the LHC. No significant excess over the standard model expectation is observed. The results are interpreted using simplified models of dark matter production via spin-0 mediators that couple to dark matter particles and to standard model quarks, providing constraints on the coupling strength between the mediator and the quarks. These are the most stringent collider limits to date for scalar mediators, and the most stringent for pseudoscalar mediators at low masses

    Combination of Searches for Higgs Boson Pair Production in Proton-Proton Collisions at √s = 13 TeV

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    This Letter describes a search for Higgs boson pair production using the combined results from four final states: bbγγ, bbττ, bbbb, and bbVV, where V represents a W or Z boson. The search is performed using data collected in 2016 by the CMS experiment from LHC proton-proton collisions at √s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. Limits are set on the Higgs boson pair production cross section. A 95% confidence level observed (expected) upper limit on the nonresonant production cross section is set at 22.2 (12.8) times the standard model value. A search for narrow resonances decaying to Higgs boson pairs is also performed in the mass range 250–3000 GeV. No evidence for a signal is observed, and upper limits are set on the resonance production cross section

    Search for Physics beyond the Standard Model in Events with Overlapping Photons and Jets

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    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

    Studies of Beauty Suppression via Nonprompt \u3ci\u3eD\u3c/i\u3e\u3csup\u3e0\u3c/sup\u3e Mesons in Pb-Pb Collisions at √\u3csup\u3eS\u3c/sup\u3eNN =5.02 TeV

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    The transverse momentum spectra of D0 mesons from b hadron decays are measured at midrapidity (|y| \u3c 1) in pp and Pb-Pb collisions at a nucleon-nucleon center of mass energy of 5.02 TeV with the CMS detector at the LHC. The D0 mesons from b hadron decays are distinguished from prompt D0 mesons by their decay topologies. In Pb-Pb collisions, the B → D0 yield is found to be suppressed in the measured pT range from 2 to 100 GeV=c as compared to pp collisions. The suppression is weaker than that of prompt D0 mesons and charged hadrons for pT around 10 GeV=c. While theoretical calculations incorporating partonic energy loss in the quark-gluon plasma can successfully describe the measured B → D0 suppression at higher pT, the data show an indication of larger suppression than the model predictions in the range of 2 \u3c pT \u3c 5 GeV/c

    Search for Narrow \u3ci\u3eHγ\u3c/i\u3e Resonances in Proton-Proton Collisions at √s =13 TeV

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    A search for heavy, narrow resonances decaying to a Higgs boson and a photon (Hγ) has been performed in proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1 collected with the CMS detector at the LHC in 2016. Events containing a photon and a Lorentz-boosted hadronically decaying Higgs boson reconstructed as a single, large-radius jet are considered, and the γ + jet invariant mass spectrum is analyzed for the presence of narrow resonances. To increase the sensitivity of the search, events are categorized depending on whether or not the large-radius jet can be identified as a result of the merging of two jets originating from b quarks. Results in both categories are found to agree with the predictions of the standard model. Upper limits on the production rate of Hγ resonances are set as a function of their mass in the range of 720–3250 GeV, representing the most stringent constraints to date

    Search for \u3ci\u3eW\u3c/i\u3e Boson Decays to Three Charged Pions

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    For the first time, a search for the rare decay of the W boson to three charged pions has been performed. Proton-proton collision data recorded by the CMS experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 77.3 fb−1, have been analyzed. No significant excess is observed above the background expectation. An upper limit of 1.01 × 10−6 is set at 95% confidence level on the branching fraction of the W boson to three charged pions. This provides a strong motivation for theoretical calculations of this branching fraction

    Search for a Light Charged Higgs Boson Decaying to a \u3ci\u3eW\u3c/i\u3e Boson and a \u3ci\u3eCP\u3c/i\u3e-Odd Higgs Boson in Final States with \u3ci\u3eeμμ\u3c/i\u3e or \u3ci\u3eμμμ\u3c/i\u3e in Proton-Proton Collisions at √s =13 TeV

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    A search for a light charged Higgs boson (H+) decaying to a W boson and a CP-odd Higgs boson (A) in final states with eμμ or μμμ is performed using data from pp collisions at √s = 13 TeV, recorded by the CMS detector at the LHC and corresponding to an integrated luminosity of 35.9 fb−1. In this search, it is assumed that the H+ boson is produced in decays of top quarks, and the A boson decays to two oppositely charged muons. The presence of signals for H+ boson masses between 100 and 160 GeV and A boson masses between 15 and 75 GeV is investigated. No evidence for the production of the H+ boson is found. Upper limits at 95% confidence level are obtained on the combined branching fraction for the decay chain, t → bH+ → bW+A → bW+μ+μ−, of 1.9 × 10−6 to 8.6 × 10−6, depending on the masses of the H+ and A bosons. These are the first limits for these decay modes of the H+ and A bosons
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