121279531
Results of the first integration test of the CMS drift tubes muon trigger
Two drift tubes (DTs) chambers of the CMS muon barrel system were exposed to a 40 MHz bunched muon beam at the CERN SPS, and for the first time the whole CMS Level-1 DTs-based trigger system chain was tested. Data at different energies and inclination angles of the incident muon beam were collected, as well as data with and without an iron absorber placed between the two chambers, to simulate the electromagnetic shower development in CMS. Special data-taking runs were dedicated to test for the first time the Track Finder system, which reconstructs track trigger candidates by performing a proper matching of the muon segments delivered by the two chambers. The present paper describes the results of these measurements.
29757321
Search for physics beyond the standard model in events with a Z boson, jets, and missing transverse energy in pp collisions at √s=7 TeV
A search is presented for physics beyond the standard model (BSM) in events with a Z boson, jets, and missing transverse energy (MET). This signature is motivated by BSM physics scenarios, including supersymmetry. The study is performed using a sample of proton-proton collision data collected at sqrt(s) = 7 TeV with the CMS experiment at the LHC, corresponding to an integrated luminosity of 4.98 inverse femtobarns. The contributions from the dominant standard model backgrounds are estimated from data using two complementary strategies, the jet-Z balance technique and a method based on modeling MET with data control samples. In the absence of evidence for BSM physics, we set limits on the non-standard-model contributions to event yields in the signal regions and interpret the results in the context of simplified model spectra. Additional information is provided to facilitate tests of other BSM physics models.
209835030
Alignment of the CMS Silicon Tracker during Commissioning with Cosmic Rays
This is the Pre-print version of the Article. The official published version of the Paper can be accessed from the link below - Copyright @ 2010 IOP
197441991
Tests of models of color reconnection and a search for glueballs using gluon jets with a rapidity gap
Gluon jets with a mean energy of 22 GeV and purity of 95% are selected from hadronic Z(0) decay events produced in e (+) e(-) annihilations. A subsample of these jets is identified which exhibits a large gap in the rapidity distribution of particles within the jet. After imposing the requirement of a rapidity gap, the gluon jet purity is 86%. These jets are observed to demonstrate a high degree of sensitivity to the presence of color reconnection, i.e. higher order QCD processes affecting the underlying color structure. We use our data to test three QCD models which include a simulation of color reconnection: one in the Ariadne Monte Carlo, one in the Herwig Monte Carlo, and the other by Rathsman in the Pythia Monte Carlo. We find the Rathsman and Ariadne color reconnection models can describe our gluon jet measurements only if very large values are used for the cutoff parameters which serve to terminate the parton showers, and that the description of inclusive Z(0) data is significantly degraded in this case. We conclude that color reconnection as implemented by these two models is disfavored. The signal from the Herwig color reconnection model is less clear and we do not obtain a definite conclusion concerning this model. In a separate study, we follow recent theoretical suggestions and search for glueball-like objects in the leading part of the gluon jets. No clear evidence is observed for these objects.
122603752
CMS Data Processing Workflows during an Extended Cosmic Ray Run
The CMS Collaboration conducted a month-long data taking exercise, the Cosmic Run At Four Tesla, during October-November 2008, with the goal of commissioning the experiment for extended operation. With all installed detector systems participating, CMS recorded 270 million cosmic ray events with the solenoid at a magnetic field strength of 3.8 T. This paper describes the data flow from the detector through the various online and offline computing systems, as well as the workflows used for recording the data, for aligning and calibrating the detector, and for analysis of the data.
124687924
Constraints on anomalous quartic gauge boson couplings from nu anti-nu gamma gamma and q anti-q gamma gamma events at LEP2
Anomalous quartic couplings between the electroweak gauge bosons may contribute to the vv gamma gamma and qq gamma gamma final states produced in e+e- collisions. This analysis uses the LEP2 OPAL data sample at centre-of-mass energies up to 209 GeV. Event selections identify vv gamma gamma and qq gamma gamma events in which the two photons are reconstructed within the detector acceptance. The cross-section for the process e+e- -> qq gamma gamma is measured. Averaging over all energies, the ratio of the observed e+e- -> qq gamma gamma cross-section to the Standard Model expectation is R(data/SM) = 0.92 +- 0.07 +- 0.04 where the errors represent the statistical and systematic uncertainties respectively. The vv gamma gamma and qq gamma gamma data are used to constrain possible anomalous W+W- gamma gamma and ZZ gamma gamma couplings. Combining with previous OPAL results from the W+W- gamma final state, the 95% confidence level limits on the anomalous coupling parameters aoz, acz, aow and acw are found to be: 
-0.007 GeV^-2 < aoz/Lambda^2 < 0.023 GeV^-2 -0.029 GeV^-2 < acz/Lambda^2 < 0.029 GeV^-2 -0.020 GeV^-2 < aow/Lambda^2 < 0.020 GeV^-2 -0.052 GeV^-2 < acw/Lambda^2 < 0.037 GeV^-2 where Lamdba is the energy scale of the new physics. Limits found when allowing two or more parameters to vary are also presented.
7502694
Measurement of the top-quark mass in the lepton+jets channel using a matrix element technique with the CDF II detector
A measurement of the top-quark mass is presented using Tevatron data from proton-antiproton collisions at center-of-mass energy {radical}(s)=1.96 TeV collected with the CDF II detector. Events are selected from a sample of candidates for production of tt pairs that decay into the lepton+jets channel. The top-quark mass is measured with an unbinned maximum likelihood method where the event probability density functions are calculated using signal and background matrix elements, as well as a set of parametrized jet-to-parton transfer functions. The likelihood function is maximized with respect to the top-quark mass, the signal fraction in the sample, and a correction to the jet energy scale (JES) calibration of the calorimeter jets. The simultaneous measurement of the JES correction ({Delta}{sub JES}) amounts to an additional in situ jet energy calibration based on the known mass of the hadronically decaying W boson. Using the data sample of 578 lepton+jets candidate events, corresponding to 3.2 fb{sup -1} of integrated luminosity, the top-quark mass is measured to be m{sub t}=172.4{+-}1.4(stat+{Delta}{sub JES}){+-}1.3(syst) GeV/c{sup 2}.