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result(s) for
"Malcles, J."
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CP violation and the CKM matrix: assessing the impact of the asymmetric B factories
2005
We present an up-to-date profile of the Cabibbo-Kobayashi-Maskawa matrix with emphasis on the interpretation of recent CP-violation results from the B factories. For this purpose, we review all relevant experimental and theoretical inputs from the contributing domains of electroweak interaction. We give the “standard” determination of the apex of the Unitarity Triangle, namely the Wolfenstein parameters \\(\\overline\\rho\\) and \\(\\overline\\eta\\), by means of a global CKM fit. The fit is dominated by the precision measurement of \\(\\sin 2 \\beta\\) by the B factories. A detailed numerical and graphical study of the impact of the results is presented. We propose to include \\(\\sin 2\\alpha\\) from the recent measurement of the time-dependent CP-violating asymmetries in \\(B^0\\to\\rho^ + \\rho^-\\), using isospin relations to discriminate the penguin contribution. The constraint from \\(\\varepsilon^\\prime/\\varepsilon\\) is discussed. We study the impact from the branching fraction measurement of the rare kaon decay \\(K^ + \\to\\pi^ + \\nu\\overline\\nu\\), and give an outlook into the reach of a future measurement of \\(K^0_L\\to\\pi^0\\nu\\overline\\nu\\). The B system is investigated in detail. We display the constraint on \\(2\\beta + \\gamma\\) and \\(\\gamma\\) from \\(B^0\\to D^{(*)\\pm}\\pi^\\mp\\) and \\(B^ + \\to D^{(*)0}K^ + \\) decays, respectively. A significant part of this paper is dedicated to the understanding of the dynamics of B decays into \\(\\pi\\pi\\), \\(K\\pi\\), \\(\\rho\\pi\\), \\(\\rho\\rho\\) and modes related to these by flavor symmetry. Various phenomenological approaches and theoretical frameworks are discussed. We find a remarkable agreement of the \\(\\pi\\pi\\) and \\(K\\pi\\) data with the other constraints in the unitarity plane when the hadronic matrix elements are calculated within QCD Factorization, where we apply a conservative treatment of the theoretical uncertainties. A global fit of QCD Factorization to all \\(\\pi\\pi\\) and \\(K\\pi\\) data leads to precise predictions of the related observables. However sizable phenomenological power corrections are preferred. Using an isospin-based phenomenological parameterization, we analyze separately the \\(B\\to K\\pi\\) decays, and the impact of electroweak penguins in response to recent discussions. We find that the present data are not sufficiently precise to constrain either electroweak parameters or hadronic amplitude ratios. We do not observe any unambiguous sign of New Physics, whereas there is some evidence for potentially large non-perturbative rescattering effects. Finally we use a model-independent description of a large class of New Physics effects in both \\(B^0\\overline B^0\\) mixing and B decays, namely in the \\(b\\to d\\) and \\(b\\to s\\) gluonic penguin amplitudes, to perform a new numerical analysis. Significant non-standard corrections cannot be excluded yet, however Standard Model solutions are favored in most cases. In the appendix to this paper we propose a frequentist method to extract a confidence level on \\(\\Delta m_s\\) from the experimental information on \\(B^0_s \\overline B_s^0\\) oscillation. In addition we describe a novel approach to combine potentially inconsistent measurements. All results reported in this paper have been obtained with the numerical analysis package CKMfitter, featuring the frequentist statistical approach Rfit.
Journal Article
Measurement of the ttbar production cross section using events with one lepton and at least one jet in pp collisions at sqrt(s)=13 TeV
2017
A measurement of the ttbar production cross section at sqrt(s)=13 TeV is presented using proton-proton collisions, corresponding to an integrated luminosity of 2.3 inverse femtobarns, collected with the CMS detector at the LHC. Final states with one isolated charged lepton (electron or muon) and at least one jet are selected and categorized according to the accompanying jet multiplicity. From a likelihood fit to the invariant mass distribution of the isolated lepton and a jet identified as coming from the hadronization of a bottom quark, the cross section is measured to be sigma(ttbar)= 835 +/- 3 (stat) +/- 23 (syst) +/- 23 (lum) pb, in agreement with the standard model prediction. Using the expected dependence of the cross section on the pole mass of the top quark (m[t]), the value of m[t] is found to be 172.7+2.4-2.7 GeV.
Journal Article
Search for CP violation in top quark-antiquark production and decay in proton-proton collisions at sqrt(s) = 8 TeV
2017
The results of a first search for CP violation in the production and decay of top quark-antiquark (ttbar) pairs are presented. The search is based on asymmetries in T-odd, triple-product correlation observables, where T is the time-reversal operator. The analysis uses a sample of proton-proton collisions at sqrt(s)=8 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 19.7 inverse femtobarns.. Events are selected having one electron or muon and at least four jets. The T-odd observables are measured using four-momentum vectors associated with ttbar production and decay. The measured asymmetries exhibit no evidence for CP-violating effects, consistent with the expectation from the standard model.
Journal Article
Search for high-mass Z-gamma resonances in e+e-gamma and mu+mu-gamma final states in proton-proton collisions at sqrt(s)=8 and 13 TeV
2017
This paper describes the search for a high-mass narrow-width scalar particle decaying into a Z boson and a photon. The analysis is performed using proton-proton collision data recorded with the CMS detector at the LHC at center-of-mass energies of 8 and 13 TeV, corresponding to integrated luminosities of 19.7 and 2.7 inverse femtobarns, respectively. The Z bosons are reconstructed from opposite-sign electron or muon pairs. No statistically significant deviation from the standard model predictions has been found in the 200-2000 GeV mass range. Upper limits at 95% confidence level have been derived on the product of the scalar particle production cross section and the branching fraction of the Z decaying into electrons or muons, which range from 280 to 20 fb for resonance masses between 200 and 2000 GeV.
Journal Article
Measurement of electroweak-induced production of W gamma with two jets in pp collisions at sqrt(s)=8 TeV and constraints on anomalous quartic gauge couplings
2017
A measurement of electroweak-induced production of W gamma and two jets is performed, where the W boson decays leptonically. The data used in the analysis correspond to an integrated luminosity of 19.7 inverse femtobarns collected by the CMS experiment in sqrt(s)=8 TeV proton-proton collisions produced at the LHC. Candidate events are selected with exactly one muon or electron, missing transverse momentum, one photon, and two jets with large rapidity separation. An excess over the hypothesis of the standard model without electroweak production of W gamma with two jets is observed with a significance of 2.7 standard deviations, corresponding to an upper limit on the electroweak signal strength of 4.3 times the standard model expectation at 95% confidence level. The cross section measured in the fiducial region is 10.8 +/- 4.1 (stat) +/- 3.4 (syst) +/- 0.3 (lum) fb, which is consistent with the standard model electroweak prediction. The total cross section for W gamma in association with two jets in the same fiducial region is measured to be 23.2 +/- 4.3 (stat) +/- 1.7 (syst) +/- 0.6 (lum) fb, which is consistent with the standard model prediction from the combination of electroweak- and quantum chromodynamics-induced processes. No deviations are observed from the standard model predictions and experimental limits on anomalous quartic gauge couplings f[M,0-7]/⁴, f[T,0-2]/⁴, and f[T,5-7]/⁴ are set at 95% confidence level.
Journal Article
A search for new phenomena in pp collisions at sqrt(s) = 13 TeV in final states with missing transverse momentum and at least one jet using the alphaT variable
2017
A search for new phenomena is performed in final states containing one or more jets and an imbalance in transverse momentum in pp collisions at a centre-of-mass energy of 13 TeV. The analysed data sample, recorded with the CMS detector at the CERN LHC, corresponds to an integrated luminosity of 2.3 inverse femtobarns. Several kinematic variables are employed to suppress the dominant background, multijet production, as well as to discriminate between other standard model and new physics processes. The search provides sensitivity to a broad range of new-physics models that yield a stable weakly interacting massive particle. The number of observed candidate events is found to agree with the expected contributions from standard model processes, and the result is interpreted in the mass parameter space of fourteen simplified supersymmetric models that assume the pair production of gluinos or squarks and a range of decay modes. For models that assume gluino pair production, masses up to 1575 and 975 GeV are excluded for gluinos and neutralinos, respectively. For models involving the pair production of top squarks and compressed mass spectra, top squark masses up to 400 GeV are excluded.
Journal Article
Measurement of the WZ production cross section in pp collisions at sqrts = 7 and 8 TeV and search for anomalous triple gauge couplings at sqrts = 8 TeV
2017
The WZ production cross section is measured by the CMS experiment at the CERN LHC in proton-proton collision data samples corresponding to integrated luminosities of 4.9 inverse femtobarns collected at sqrt(s)= 7 TeV, and 19.6 inverse femtobarns at sqrt(s)= 8 TeV. The measurements are performed using the fully-leptonic WZ decay modes with electrons and muons in the final state. The measured cross sections for 71 < m[Z] < 111 GeV are sigma(pp to WZ; sqrt(s)= 7 TeV) = 20.14 +/- 1.32 (stat) +/- 1.13 (syst) +/- 0.44 (lumi) pb and sigma(pp to WZ; sqrt(s)= 8 TeV) = 24.09 +/- 0.87 (stat) +/- 1.62 (syst) +/- 0.63 (lumi) pb. Differential cross sections with respect to the Z boson pt, the leading jet pt, and the number of jets are obtained using the sqrt(s)= 8 TeV data. The results are consistent with standard model predictions and constraints on anomalous triple gauge couplings are obtained.
Journal Article
Measurement of the ttbbar production cross section using events in the e mu final state in pp collisions at sqrt(s)=13 TeV
2017
The cross section of top quark-antiquark pair production in proton-proton collisions at sqrt(s) = 13 TeV is measured by the CMS experiment at the LHC, using data corresponding to an integrated luminosity of 2.2 inverse femtobarns. The measurement is performed by analyzing events in which the final state includes one electron, one muon, and two or more jets, at least one of which is identified as originating from hadronization of a b quark. The measured cross section is 792 +/- 8 (stat) +/- 37 (syst) +/- 21 (lumi) pb, in agreement with the expectation from the standard model.
Journal Article
Measurements of the associated production of a Z boson and b jets in pp collisions at sqrt(s) = 8 TeV
2017
Measurements of the associated production of a Z boson with at least one jet originating from a b quark in proton-proton collisions at sqrt(s) = 8 TeV are presented. Differential cross sections are measured with data collected by the CMS experiment corresponding to an integrated luminosity of 19.8 inverse femtobarns. Z bosons are reconstructed through their decays to electrons and muons. Cross sections are measured as a function of observables characterizing the kinematics of the b jet and the Z boson. Ratios of differential cross sections for the associated production with at least one b jet to the associated production with any jet are also presented. The production of a Z boson with two b jets is investigated, and differential cross sections are measured for the dijet system. Results are compared to theoretical predictions, testing two different flavour schemes for the choice of initial-state partons.
Journal Article
Suppression and azimuthal anisotropy of prompt and nonprompt J/psi production in PbPb collisions at sqrt(sNN) = 2.76 TeV
by
Favaro, C.
,
Titov, M.
,
Mamouni, H. El
in
High Energy Physics - Experiment
,
Nuclear Experiment
,
Physics
2017
The nuclear modification factor RAA and the azimuthal anisotropy coefficient v[2] of prompt and nonprompt (i.e. those from decays of b hadrons) J/psi mesons, measured from PbPb and pp collisions at sqrt(s[NN])=2.76 TeV at the LHC, are reported. The results are presented in several event centrality intervals and several kinematic regions, for transverse momenta pt>6.5 GeV/c and rapidity abs(y)<2.4, extending down to pt=3 GeV/c in the 1.6
Journal Article
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