Measurements of the five most significant angular coefficients, A0 through A4, for Z bosons produced in pp collisions at sqrt(s)=8 TeV and decaying to mu+mu- are presented as a function of the ...transverse momentum and rapidity of Z boson. The integrated luminosity of the dataset collected with the CMS detector at the LHC corresponds to 19.7 inverse femtobarns. These measurements provide comprehensive information about Z boson production mechanisms, and are compared to QCD predictions at leading order, next-to-leading order, and next-to-next-to-leading order in perturbation theory.
A search is performed for heavy Majorana neutrinos (N) using an event signature defined by two muons of the same charge and two jets (mu+/- mu+/- jj). The data correspond to an integrated luminosity ...of 19.7 inverse femtobarns of proton-proton collisions at a center-of-mass energy of 8 TeV, collected with the CMS detector at the CERN LHC. No excess of events is observed beyond the expected standard model background and upper limits are set on abs(Vmu,N)^2 as a function of Majorana neutrino mass mN for masses in the range of 40-500 GeV, where Vmu,N is the mixing element of the heavy neutrino with the standard model muon neutrino. The limits obtained are abs(Vmu,N)^2 < 0.00470 for mN = 90 GeV, abs(Vmu,N)^2 < 0.0123 for mN = 200 GeV, and abs(Vmu,N)^2 < 0.583 for mN = 500 GeV. These results extend considerably the regions excluded by previous direct searches.
The first measurement of the cross section ratio sigma(t t-bar b b-bar) / sigma(t t-bar jj) is presented using a data sample corresponding to an integrated luminosity of 19.6 inverse femtobarns ...collected in pp collisions at sqrt(s) = 8 TeV with the CMS detector at the LHC. Events with two leptons (e or mu) and four reconstructed jets, including two identified as b quark jets, in the final state are selected. The ratio is determined for a minimum jet transverse momentum pt of both 20 and 40 GeV. The measured ratio is 0.022 +/- 0.003 (stat) +/- 0.005 (syst) for pt > 20 GeV. The absolute cross sections sigma(t t-bar b b-bar) and sigma(t t-bar jj) are also measured. The measured ratio for pt > 40 GeV is compatible with a theoretical quantum chromodynamics calculation at next-to-leading order.
The angular distributions and the differential branching fraction of the decay B0 to K*0(892) mu mu are studied using data corresponding to an integrated luminosity of 20.5 inverse femtobarns ...collected with the CMS detector at the LHC in pp collisions at sqrt(s) = 8 TeV. From 1430 signal decays, the forward-backward asymmetry of the muons, the K*0(892) longitudinal polarization fraction, and the differential branching fraction are determined as a function of the dimuon invariant mass squared. The measurements are among the most precise to date and are in good agreement with standard model predictions.
A search for pair production of third-generation scalar leptoquarks decaying to top quark and tau lepton pairs is presented using proton-proton collision data at a center-of-mass energy of sqrt(s)=8 ...TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 inverse femtobarns. The search is performed using events that contain an electron or a muon, a hadronically decaying tau lepton, and two or more jets. The observations are found to be consistent with the standard model predictions. Assuming that all leptoquarks decay to a top quark and a tau lepton, the existence of pair produced, charge -1/3, third-generation leptoquarks up to a mass of 685 GeV is excluded at 95% confidence level. This result constitutes the first direct limit for leptoquarks decaying into a top quark and a tau lepton, and is also directly applicable to pair produced bottom squarks decaying via the R-parity violating coupling lambda'333.
A measurement of inclusive ZZ production cross section and constraints on anomalous triple gauge couplings in proton-proton collisions at sqrt(s) = 8 TeV are presented. A data sample, corresponding ...to an integrated luminosity of 19.6 inverse femtobarns was collected with the CMS experiment at the LHC. The measurements are performed in the leptonic decay modes ZZ to lll'l', where l = e, mu and l' = e, mu, tau. The measured total cross section, sigma(pp to ZZ) = 7.7 +/- 0.5 (stat.) +0.5-0.4 (syst.) +/- 0.4 (theo.) +/- 0.2 (lum.) pb for both Z bosons produced in the mass range 60 < mZ < 120 GeV, is consistent with standard model predictions. Differential cross sections are measured and well described by the theoretical predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZ gamma couplings at the 95% confidence level: -0.004
The Bc+/- to J/psi pi+/- and Bc+/- to J/psi pi+/- pi+/- pi-/+ decay modes are studied in proton-proton collisions at a center-of-mass energy of 7 TeV with the CMS detector at the LHC. The kinematic ...region investigated requires Bc+/- mesons with transverse momentum pt > 15 GeV and rapidity abs(y) < 1.6. The data sample corresponds to an integrated luminosity of 5.1 inverse femtobarns. The ratio of the branching fractions B(Bc+/- to J/psi pi+/- pi+/- pi-/+)/B(Bc+/- to J/psi pi+/-) is measured to be 2.55 +/- 0.80 (stat) +/- 0.33 (syst) +0.04/-0.01 (tauBc+). The ratio of the production cross sections times branching fractions (sigma(Bc+) B(Bc+ to J/psi pi+))/ (sigma(B+) B(B+ to J/psi K+)) is determined to be 0.48 +/- 0.05 (stat) +/- 0.03 (syst) +/- 0.05 (tau_{Bc})%
A measurement of the underlying event (UE) activity in proton-proton collisions is performed using events with charged-particle jets produced in the central pseudorapidity region (abs(etajet) < 2) ...and with transverse momentum 1<= ptjet < 100 GeV. The analysis uses a data sample collected at a centre-of-mass energy of 2.76 TeV with the CMS experiment at the LHC. The UE activity is measured as a function of ptjet in terms of the average multiplicity and scalar sum of transverse momenta (pt) of charged particles, with abs(eta) < 2 and pt > 0.5 GeV, in the azimuthal region transverse to the highest pt jet direction. By further dividing the transverse region into two regions of smaller and larger activity, various components of the UE activity are separated. The measurements are compared to previous results at 0.9 and 7 TeV, and to predictions of several Monte Carlo event generators, providing constraints on the modelling of the UE dynamics.
A search for a light charged Higgs boson, originating from the decay of a top quark and subsequently decaying into a charm quark and a strange antiquark, is presented. The data used in the analysis ...correspond to an integrated luminosity of 19.7 inverse-femtobarns recorded in proton-proton collisions at sqrt(s) = 8 TeV by the CMS experiment at the LHC. The search is performed in the process t tbar to W+/- b H-/+ bbar, where the W boson decays to a lepton (electron or muon) and a neutrino. The decays lead to a final state comprising an isolated lepton, at least four jets and large missing transverse energy. No significant deviation is observed in the data with respect to the standard model predictions, and model-independent upper limits are set on the branching fraction BF( t to H+ b ), ranging from 1.2 to 6.5% for a charged Higgs boson with mass between 90 and 160 GeV, under the assumption that BF( H+ to c sbar ) = 100%.
A study of the 1300 K compressive and tensile creep properties of 001-oriented NiAl–1Hf (D209) single crystals has been undertaken. Neither post homogenization cooling treatment, minor chemical ...variations within an ingot or from ingot-to-ingot, nor testing procedure had a significant effect on mechanical behavior; however a heat treatment which dissolved the initial G-phase precipitates and promoted formation of Heusler particles led to a strength reduction. Little primary creep was found utilizing direct measurement of strain, and a misorientation of 18° from the 001 did not reduce the creep strength. The effects of heat treatments on properties and a comparison of the flow stress–strain rate data to those predicted by the Jaswon–Cottrell solid solution hardening model indicate that the 1300 K strength in NiAl–1Hf single crystals is mainly due to precipitation hardening mechanisms.
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