Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV

The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standard model.Comment: Replaced with published version. Included journal reference and DO

Measurement of the X(3872) production cross section via decays to J/psi pi(+)pi(-) in pp collisions at √s=7 TeV

The article is the pre-print version of the final publishing paper that is available from the link below.The production of the X(3872) is studied in pp collisions at √s=7TeV, using decays to J/ψπ + π −, where the J/ψ decays to two muons. The data were recorded by the CMS experiment and correspond to an integrated luminosity of 4.8 fb−1. The measurements are performed in a kinematic range in which the X(3872) candidates have a transverse momentum 10 < pT < 50 GeV and rapidity |y| < 1.2. The ratio of the X(3872) and ψ(2S) cross sections times their branching fractions into J/ψ π+ π− is measured as a function of pT. In addition, the fraction of X(3872) originating from B decays is determined. From these measurements the prompt X(3872) differential cross section times branching fraction as a function of pT is extracted. The π+ π− mass spectrum of the J/ψπ+ π− system in the X(3872) decays is also investigated

Measurement of the W-boson helicity in top-quark decays from t(t)over-bar production in lepton plus jets events in pp collisions at √s=7 TeV

This is the pre-print version of the final published article that can be accessed at the link below.The W-boson helicity fractions in top-quark decays are measured with tt events in the lepton+jets final state, using proton-proton collisions at a centre-of-mass energy of 7 TeV, collected in 2011 with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 5.0 fb-1. The measured fractions of longitudinal, left-, and right-handed helicity are F0 = 0.682 0.030 (stat.) 0.033 (syst.), FL = 0.310 0.022 (stat.) 0.022 (syst.), and FR = 0.008 0.012 (stat.) 0.014 (syst.), consistent with the standard model predictions. The measured fractions are used to probe the existence of anomalous Wtb couplings. Exclusion limits on the real components of the anomalous couplings gL, gR are also derived

Search for narrow resonances and quantum black holes in inclusive and b-tagged dijet mass spectra from pp collisions at √s=7 TeV

This is the pre-print version of the Article. The official published version of the Article can be accessed from the links below - Copyright @ 2013 Springer-Verlag.A search for narrow resonances and quantum black holes is performed in inclusive and b-tagged dijet mass spectra measured with the CMS detector at the LHC. The data set corresponds to 5 fb−1 of integrated luminosity collected in pp collisions at √s=7 TeV. No narrow resonances or quantum black holes are observed. Model-independent upper limits at the 95% confidence level are obtained on the product of the cross section, branching fraction into dijets, and acceptance for three scenarios: decay into quark-quark, quark-gluon, and gluon-gluon pairs. Specific lower limits are set on the mass of string resonances (4.31 TeV), excited quarks (3.32 TeV), axigluons and colorons (3.36 TeV), scalar color-octet resonances (2.07 TeV), E6 diquarks (3.75 TeV), and on the masses of W′ (1.92 TeV) and Z′ (1.47 TeV) bosons. The limits on the minimum mass of quantum black holes range from 4 to 5.3 TeV. In addition, b-quark tagging is applied to the two leading jets and upper limits are set on the production of narrow dijet resonances in a model-independent fashion as a function of the branching fraction to b-jet pairs.This study is supported by the BMWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MSI (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MON, RosAtom, RAS and RFBr (Russia); MSTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)

Measurement of the t(t)over-bar production cross section in the all-jet final state in pp collisions at √s=7 TeV

This article is the pre-print version of the final published paper that is available from the link below.A measurement is presented of the tt production cross section (σtt) in protonproton collisions at a centre-of-mass energy of 7TeV, in the all-jet final state that contains at least six jets, two of which are tagged as originating from b quarks. The data correspond to an integrated luminosity of 3.54 fb-1, collected with the CMS detector at the LHC. The cross section is determined through an unbinned maximum likelihood fit of background and tt signal to the reconstructed mass spectrum of tt candidates in the data, in which events are subjected to a kinematic fit assuming a tt → W+bW-b → 6 jets hypothesis. The measurement yields σtt = 139±10 (stat.) ±26 (syst.) ±3 (lum.) pb, a result consistent with those obtained in other tt decay channels, as well as with predictions of the standard model

Search for pair production of excited top quarks in the lepton+jets final state

A search is performed for pair-produced spin-3/2 excited top quarks (t* t*-bar), each decaying to a top quark and a gluon. The search uses data collected with the CMS detector from pp collisions at a center-of-mass energy of sqrt(s)=8 TeV, selecting events that have a single isolated muon or electron, an imbalance in transverse momentum, and at least six jets, of which one must be compatible with originating from the fragmentation of a b quark. The data, corresponding to an integrated luminosity of 19.5 inverse femtobarns, show no significant excess over standard model predictions, and provide a lower limit of 803 GeV at 95% confidence on the mass of the spin-3/2 t* quark in an extension of the Randall-Sundrum model, assuming a 100% branching fraction of its decay into a top quark and a gluon. This is the first search for a spin-3/2 excited top quark performed at the LHC

Measurement of the Λ(b)0\Lambda(b)0 lifetime in pp collisions at s=7\sqrt{s} = 7 TeV

A measurement of the Lambda(b)0 lifetime using the decay Lambda(b)0 to J/Psi Lambda in proton-proton collisions at sqrt(s)=7 TeV is presented. The data set, corresponding to an integrated luminosity of about 5 inverse femtobarns, was recorded with the CMS experiment at the Large Hadron Collider using triggers that selected dimuon events in the J/Psi mass region. The Lambda(b)0 lifetime is measured to be 1.503 +/- 0.052 (stat.) +/- 0.031 (syst.) ps

Search for electroweak production of charginos and neutralinos using leptonic final states in pp collisions at s=7\sqrt{s} = 7 TeV

The 2011 dataset of the CMS experiment, consisting of an integrated luminosity of 4.98 inverse femtobarns of pp collisions at sqrt(s) = 7 TeV, enables expanded searches for direct electroweak pair production of charginos and neutralinos in supersymmetric models as well as their analogs in other models of new physics. Searches sensitive to such processes, with decays to final states that contain two or more leptons, are presented. Final states with three leptons, with a same-sign lepton pair, and with an opposite-sign lepton pair in conjunction with two jets, are examined. No excesses above the standard model expectations are observed. The results are used in conjunction with previous results on four-lepton final states to exclude a range of chargino and neutralino masses from approximately 200 to 500 GeV in the context of models that assume large branching fractions of charginos and neutralinos to leptons and vector bosons.Comment: Replaced with published version. Added journal reference and DO