The production of a Z boson, decaying into two leptons and produced in association with one or more b jets, is studied using proton-proton collisions delivered by the LHC at a centre-of-mass energy ...of 7 TeV. The data were recorded in 2011 with the CMS detector and correspond to an integrated luminosity of 5 fb super(-1). The Z() + b-jets cross sections (where = mu mu or ee) are measured separately for a Z boson produced with exactly one b jet and with at least two b jets. In addition, a cross section ratio is extracted for a Z boson produced with at least one b jet, relative to a Z boson produced with at least one jet. The measured cross sections are compared to various theoretical predictions, and the data favour the predictions in the five-flavour scheme, where b quarks are assumed massless. The kinematic properties of the reconstructed particles are compared with the predictions from the MadGraph event generator using the pythia parton shower simulation. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).Results are presented from a search for the production of a heavy gauge boson W' decaying into a top and a bottom quark, ...using a data set collected by the CMS experiment at ... = 8 TeV and corresponding to an integrated luminosity of 19.5 fb super(-1). Various models of W'-boson production are studied by allowing for an arbitrary combination of left- and right-handed couplings. The analysis is based on the detection of events with a lepton (e, mu ), jets, and missing transverse energy in the final state. No evidence for W'-boson production is found and 95% confidence level upper limits on the production cross section times branching fraction are obtained. For W super(') bosons with purely right-handed couplings, and for those with left-handed couplings assuming no interference effects, the observed 95% confidence level limit is M(W') > 2.05 TeV. For W super(') bosons with purely left-handed couplings, including interference effects, the observed 95% confidence level limit is M(W') > 1.84 TeV. The results presented in this paper are the most stringent limits published to date. Figure not available: see fulltext.
A measurement of the underlying activity in scattering processes with transverse momentum scale in the GeV region is performed in proton-proton collisions at sqrt(s) = 0.9 TeV, using data collected ...by the CMS experiment at the LHC. Charged hadron production is studied with reference to the direction of a leading object, either a charged particle or a set of charged particles forming a jet. Predictions of several QCD-inspired models as implemented in PYTHIA are compared, after full detector simulation, to the data. The models generally predict too little production of charged hadrons with pseudorapidity eta < 2, p_T > 0.5 GeV/c, and azimuthal direction transverse to that of the leading object.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).A measurement of the ... cross section in pp collisions at ... TeV is presented, using data corresponding to an integrated ...luminosity of 5.0 fb super(-1) collected with the CMS detector. This measurement is based on the observation of events with an imbalance of transverse energy in excess of 130 GeV and a single photon in the absolute pseudorapidity range | eta |<1.4 with transverse energy above 145 GeV. The ... production cross section is measured to be 21.1 plus or minus 4.2 (stat.) plus or minus 4.3 (syst.) plus or minus 0.5 (lum.) fb, which agrees with the standard model prediction of 21.9 plus or minus 1.1 fb. The results are combined with the CMS measurement of Z gamma production in the super(+) super(-) gamma final state (where is an electron or a muon) to yield the most stringent limits to date on triple gauge boson couplings: ..., ... for ZZ gamma and ..., ... for Z gamma gamma couplings. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).A search for exclusive or quasi-exclusive W super(+)W super(-) production by photon-photon interactions, pp arrow right p ...super((*))W super(+)W super(-)p super((*)), at ... TeV is reported using data collected by the CMS detector with an integrated luminosity of 5.05 fb super(-1). Events are selected by requiring a mu super( plus or minus )e super() vertex with no additional associated charged tracks and dilepton transverse momentum p sub(T)( mu super( plus or minus )e super()) > 30 GeV. Two events passing all selection requirements are observed in the data, compared to a standard model expectation of 2.2 plus or minus 0.4 signal events with 0.84 plus or minus 0.15 background. The tail of the dilepton p sub(T) distribution is studied for deviations from the standard model. No events are observed with p sub(T) >100 GeV. Model-independent upper limits are computed and compared to predictions involving anomalous quartic gauge couplings. The limits on the parameters ... with a dipole form factor and an energy cutoff Lambda sub(cutoff)=500 GeV are of the order of 10 super(-4). Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).Figure not available: see fulltext. The production of the X(3872) is studied in pp collisions at ... TeV, using decays to ...J/ psi pi super(+) pi super(-), where the J/ psi decays to two muons. The data were recorded by the CMS experiment and correspond to an integrated luminosity of 4.8 fb super(-1). The measurements are performed in a kinematic range in which the X(3872) candidates have a transverse momentum 10<p sub(T) <50 GeV and rapidity |y|<1.2. The ratio of the X(3872) and psi (2S) cross sections times their branching fractions into J/ psi pi super(+) pi super(-) is measured as a function of p sub(T). 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 p sub(T) is extracted. The pi super(+) pi super(-) mass spectrum of the J/ psi pi super(+) pi super(-) system in the X(3872) decays is also investigated.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).A search for supersymmetry in final states with jets and missing transverse energy is performed in pp collisions at a ...centre-of-mass energy of ... TeV. The data sample corresponds to an integrated luminosity of 4.98 fb super(-1) collected by the CMS experiment at the LHC. In this search, a dimensionless kinematic variable, alpha sub(T), is used as the main discriminator between events with genuine and misreconstructed missing transverse energy. The search is performed in a signal region that is binned in the scalar sum of the transverse energy of jets and the number of jets identified as originating from a bottom quark. No excess of events over the standard model expectation is found. Exclusion limits are set in the parameter space of the constrained minimal supersymmetric extension of the standard model, and also in simplified models, with a special emphasis on compressed spectra and third-generation scenarios.Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).A measurement is presented of the ZZ production cross section in the ZZ arrow right 22' decay mode with = e, mu and ' = e, ...mu , tau in proton-proton collisions at ... TeV with the CMS experiment at the LHC. Results are based on data corresponding to an integrated luminosity of 5.0 fb super(-1). The measured cross section ... is consistent with the standard model predictions. The following limits on ZZZ and ZZ gamma anomalous trilinear gauge couplings are set at 95% confidence level: ..., and ...Figure not available: see fulltext.
In June 2008 single-sided silicon strip sensors with 50 \(\mu\)m readout pitch were tested in a highly energetic pion beam at the SPS at CERN. The purpose of the test was to evaluate characteristic ...detector properties by varying the strip width and the number of intermediate strips. The experimental setup and first results for the spatial resolution are discussed.
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