18 research outputs found

    Search for pair-produced resonances decaying to quark pairs in proton-proton collisions at root s=13 TeV

    Get PDF
    A general search for the pair production of resonances, each decaying to two quarks, is reported. The search is conducted separately for heavier resonances (masses above 400 GeV), where each of the four final-state quarks generates a hadronic jet resulting in a four-jet signature, and for lighter resonances (masses between 80 and 400 GeV), where the pair of quarks from each resonance is collimated and reconstructed as a single jet resulting in a two-jet signature. In addition, a b-tagged selection is applied to target resonances with a bottom quark in the final state. The analysis uses data collected with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 35.9 fb(-1), from proton-proton collisions at a center-of-mass energy of 13 TeV. The mass spectra are analyzed for the presence of new resonances, and are found to be consistent with standard model expectations. The results are interpreted in the framework of R-parity-violating supersymmetry assuming the pair production of scalar top quarks decaying via the hadronic coupling lambda ''(312) or lambda ''(323) and upper limits on the cross section as a function of the top squark mass are set. These results probe a wider range of masses than previously explored at the LHC, and extend the top squark mass limits in the (t) over tilde -> qq' scenario.Peer reviewe

    Observation of the Λb0→J/ψΛφ decay in proton-proton collisions at s=13TeV

    No full text
    The observation of the Λb0→J/ψΛφ decay is reported using proton-proton collision data collected at s=13TeV by the CMS experiment at the LHC in 2018, corresponding to an integrated luminosity of 60fb−1. The ratio of the branching fractions B(Λb0→J/ψΛφ)/B(Λb0→ψ(2S)Λ) is measured to be (8.26±0.90(stat)±0.68(syst)±0.11(B))×10−2, where the first uncertainty is statistical, the second is systematic, and the last uncertainty reflects the uncertainties in the world-average branching fractions of φ and ψ(2S) decays to the reconstructed final states

    Measurement of the cross section for tt \mathrm{t}\overline{\mathrm{t}} production with additional jets and b jets in pp collisions at s \sqrt{s} = 13 TeV

    No full text
    Measurements of the cross section for the production of top quark pairs in association with a pair of jets from bottom quarks (σttbb) \left({\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{b}\overline{\mathrm{b}}}\right) and in association with a pair of jets from quarks of any flavor or gluons (σttjj) \left({\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{jj}}\right) and their ratio are presented. The data were collected in proton-proton collisions at a center-of-mass energy of 13 TeV by the CMS experiment at the LHC in 2016 and correspond to an integrated luminosity of 35.9 fb−1. The measurements are performed in a fiducial phase space and extrapolated to the full phase space, separately for the dilepton and lepton+jets channels, where lepton corresponds to either an electron or a muon. The results of the measurements in the fiducial phase space for the dilepton and lepton+jets channels, respectively, are σttjj {\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{jj}} = 2.36±0.02 (stat)±0.20 (syst) pb and 31.0±0.2 (stat)±2.9 (syst) pb, and for the cross section ratio 0.017 ± 0.001 (stat) ± 0.001 (syst) and 0.020 ± 0.001 (stat) ± 0.001 (syst). The values of σttbb {\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{b}\overline{\mathrm{b}}} are determined from the product of the σttjj {\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{jj}} and the cross section ratio, obtaining, respectively, 0.040±0.002 (stat)±0.005 (syst) pb and 0.62±0.03 (stat)±0.07 (syst) pb. These measurements are the most precise to date and are consistent, within the uncertainties, with the standard model expectations obtained using a matrix element calculation at next-to-leading order in quantum chromodynamics matched to a parton shower

    Search for medium effects using jets from bottom quarks in PbPb collisions at sNN=5.02TeV

    No full text
    The first study of the shapes of jets arising from bottom (b) quarks in heavy ion collisions is presented. Jet shapes are studied using charged hadron constituents as a function of their radial distance from the jet axis. Lead-lead (PbPb) collision data at a nucleon-nucleon center-of-mass energy of sNN=5.02TeV were recorded by the CMS detector at the LHC, with an integrated luminosity of 1.69nb−1. Compared to proton-proton collisions, a redistribution of the energy in b jets to larger distances from the jet axis is observed in PbPb collisions. This medium-induced redistribution is found to be substantially larger for b jets than for inclusive jets

    A search for the standard model Higgs boson decaying to charm quarks

    No full text
    A direct search for the standard model Higgs boson, H, produced in association with a vector boson, V (W or Z), and decaying to a charm quark pair is presented. The search uses a data set of proton-proton collisions corresponding to an integrated luminosity of 35.9 fb−1, collected by the CMS experiment at the LHC in 2016, at a centre-of-mass energy of 13 TeV. The search is carried out in mutually exclusive channels targeting specific decays of the vector bosons: W → lν, Z → ll, and Z → νν, where l is an electron or a muon. To fully exploit the topology of the H boson decay, two strategies are followed. In the first one, targeting lower vector boson transverse momentum, the H boson candidate is reconstructed via two resolved jets arising from the two charm quarks from the H boson decay. A second strategy identifies the case where the two charm quark jets from the H boson decay merge to form a single jet, which generally only occurs when the vector boson has higher transverse momentum. Both strategies make use of novel methods for charm jet identification, while jet substructure techniques are also exploited to suppress the background in the merged-jet topology. The two analyses are combined to yield a 95% confidence level observed (expected) upper limit on the cross section σ(VH)B(Hcc) \sigma \left(\mathrm{VH}\right)\mathrm{\mathcal{B}}\left(\mathrm{H}\to \mathrm{c}\overline{\mathrm{c}}\right) of 4.5 (2.40.7+1.0) \left({2.4}_{-0.7}^{+1.0}\right) pb, corresponding to 70 (37) times the standard model prediction

    Search for Higgs Boson and Observation of <math display="inline"><mi>Z</mi></math> Boson through their Decay into a Charm Quark-Antiquark Pair in Boosted Topologies in Proton-Proton Collisions at <math display="inline"><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math>

    No full text
    International audienceA search for the standard model (SM) Higgs boson (H) produced with transverse momentum (pT) greater than 450 GeV and decaying to a charm quark-antiquark (cc¯) pair is presented. The search is performed using proton-proton collision data collected at s=13  TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 138  fb-1. Boosted H→cc¯ decay products are reconstructed as a single large-radius jet and identified using a deep neural network charm tagging technique. The method is validated by measuring the Z→cc¯ decay process, which is observed in association with jets at high pT for the first time with a signal strength of 1.00-0.14+0.17(syst)±0.08(theo)±0.06(stat), defined as the ratio of the observed process rate to the SM expectation. The observed (expected) upper limit on σ(H)B(H→cc¯) is set at 47 (39) times the SM prediction at 95% confidence level

    Search for CP violation in tt \overline{\textrm{t}} H and tH production in multilepton channels in proton-proton collisions at s \sqrt{s} = 13 TeV

    No full text
    The charge-parity (CP) structure of the Yukawa interaction between the Higgs (H) boson and the top quark is measured in a data sample enriched in the tt \overline{\textrm{t}} H and tH associated production, using 138 fb−1 of data collected in proton-proton collisions at s \sqrt{s} = 13 TeV by the CMS experiment at the CERN LHC. The study targets events where the H boson decays via H → WW or H → ττ and the top quarks decay via t → Wb: the W bosons decay either leptonically or hadronically, and final states characterized by the presence of at least two leptons are studied. Machine learning techniques are applied to these final states to enhance the separation of CP -even from CP -odd scenarios. Two-dimensional confidence regions are set on κt and κ \overset{\sim }{\kappa } t, which are respectively defined as the CP -even and CP -odd top-Higgs Yukawa coupling modifiers. No significant fractional CP -odd contributions, parameterized by the quantity |fCPHtt {f}_{CP}^{\textrm{Htt}} | are observed; the parameter is determined to be |fCPHtt {f}_{CP}^{\textrm{Htt}} | = 0.59 with an interval of (0.24, 0.81) at 68% confidence level. The results are combined with previous results covering the H → ZZ and H → γγ decay modes, yielding two- and one-dimensional confidence regions on κt and κ \overset{\sim }{\kappa } t, while |fCPHtt {f}_{CP}^{\textrm{Htt}} | is determined to be |fCPHtt {f}_{CP}^{\textrm{Htt}} | = 0.28 with an interval of |fCPHtt {f}_{CP}^{\textrm{Htt}} | < 0.55 at 68% confidence level, in agreement with the standard model CP -even prediction of |fCPHtt {f}_{CP}^{\textrm{Htt}} | = 0

    Search for Exotic Higgs Boson Decays H\ensuremath{\rightarrow}\mathcal{A}\mathcal{A}\ensuremath{\rightarrow}4\ensuremath{\gamma} with Events Containing Two Merged Diphotons in Proton-Proton Collisions at s=13  TeV\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}

    No full text

    Search for Exotic Higgs Boson Decays H→AA→4γ with Events Containing Two Merged Diphotons in Proton-Proton Collisions at sqrt[s]=13  TeV

    No full text
    : We present the first direct search for exotic Higgs boson decays H→AA, A→γγ in events with two photonlike objects. The hypothetical particle A is a low-mass spin-0 particle decaying promptly to a merged diphoton reconstructed as a single photonlike object. We analyze the data collected by the CMS experiment at sqrt[s]=13  TeV corresponding to an integrated luminosity of 136  fb^{-1}. No excess above the estimated background is found. We set upper limits on the branching fraction B(H→AA→4γ) of (0.9-3.3)×10^{-3} at 95% confidence level for masses of A in the range 0.1-1.2&nbsp;GeV

    Study of central exclusive production in proton-proton collisions at s=5.02\sqrt{s} = 5.02 and 13TeV

    No full text
    Central exclusive and semiexclusive production of pairs is measured with the CMS detector in proton-proton collisions at the LHC at center-of-mass energies of 5.02 and 13TeV. The theoretical description of these nonperturbative processes, which have not yet been measured in detail at the LHC, poses a significant challenge to models. The two pions are measured and identified in the CMS silicon tracker based on specific energy loss, whereas the absence of other particles is ensured by calorimeter information. The total and differential cross sections of exclusive and semiexclusive central production are measured as functions of invariant mass, transverse momentum, and rapidity of the system in the fiducial region defined as transverse momentum and pseudorapidity . The production cross sections for the four resonant channels , , , and are extracted using a simple model. These results represent the first measurement of this process at the LHC collision energies of 5.02 and 13TeV
    corecore