We present the results of a search for pair production of a heavy toplike (t') quark decaying to Wq final states using data corresponding to an integrated luminosity of 5.6 fb{sup -1} collected by ...the CDF II detector in pp collisions at {radical}(s)=1.96 TeV. We perform parallel searches for t'{yields}Wb and t'{yields}Wq (where q is a generic down-type quark) in events containing a lepton and four or more jets. By performing a fit to the two-dimensional distribution of total transverse energy versus reconstructed t{sup '} quark mass, we set upper limits on the t't' production cross section and exclude a standard model fourth-generation t' quark decaying to Wb (Wq) with mass below 358 (340) GeV/c{sup 2} at 95% C.L.
We report measurements of direct CP--violating asymmetries in charmless decays of neutral bottom hadrons to pairs of charged hadrons with the upgraded Collider Detector at the Fermilab Tevatron. ...Using a data sample corresponding to 1 fb{sup -1} of integrated luminosity, we obtain the first measurements of direct CP violation in bottom strange mesons, A{sub CP}(B{sub s}{sup 0}{yields}K{sup -}{pi}{sup +})=+0.39{+-}0.15(stat){+-}0.08(syst), and bottom baryons, A{sub CP}({Lambda}{sub b}{sup 0}{yields}p{pi}{sup -})=+0.03{+-}0.17(stat){+-}0.05(syst) and A{sub CP}({Lambda}{sub b}{sup 0}{yields}pK{sup -})=+0.37{+-}0.17(stat){+-}0.03(syst). In addition, we measure CP violation in B{sup 0}{yields}K{sup +}{pi}{sup -} decays with 3.5{sigma} significance, A{sub CP}(B{sup 0}{yields}K{sup +}{pi}{sup -})=-0.086{+-}0.023(stat){+-}0.009(syst), in agreement with the current world average. Measurements of branching fractions of B{sub s}{sup 0}{yields}K{sup +}K{sup -} and B{sup 0}{yields}{pi}{sup +}{pi}{sup -} decays are also updated.
We reconstruct the rare decays B{sup +}{yields}K{sup +}{mu}{sup +}{mu}{sup -}, B{sup 0}{yields}K{sup *}(892){sup 0}{mu}{sup +}{mu}{sup -}, and B{sub s}{sup 0}{yields}{phi}(1020){mu}{sup +}{mu}{sup -} ...in a data sample corresponding to 4.4 fb{sup -1} collected in pp collisions at {radical}(s)=1.96 TeV by the CDF II detector at the Tevatron Collider. Using 121{+-}16 B{sup +}{yields}K{sup +}{mu}{sup +}{mu}{sup -} and 101{+-}12 B{sup 0}{yields}K*{sup 0}{mu}{sup +}{mu}{sup -} decays we report the branching ratios. In addition, we report the differential branching ratio and the muon forward-backward asymmetry in the B{sup +} and B{sup 0} decay modes, and the K{sup *0} longitudinal polarization fraction in the B{sup 0} decay mode with respect to the squared dimuon mass. These are consistent with the predictions, and most recent determinations from other experiments and of comparable accuracy. We also report the first observation of the B{sub s}{sup 0}{yields}{phi}{mu}{sup +}{mu}{sup -} decay and measure its branching ratio BR(B{sub s}{sup 0}{yields}{phi}{mu}{sup +}{mu}{sup -})=1.44{+-}0.33{+-}0.46x10{sup -6} using 27{+-}6 signal events. This is currently the most rare B{sub s}{sup 0} decay observed.
We present a direct measurement of the mass difference between t and t quarks using tt candidate events in the lepton+jets channel, collected with the CDF II detector at Fermilab's 1.96 TeV Tevatron ...pp Collider. We make an event by event estimate of the mass difference to construct templates for top quark pair signal events and background events. The resulting mass difference distribution of data is compared to templates of signals and background using a maximum likelihood fit. From a sample corresponding to an integrated luminosity of 5.6 fb{sup -1}, we measure a mass difference, {Delta}M{sub top}=M{sub t}-M{sub t}=-3.3{+-}1.4(stat){+-}1.0(syst) GeV/c{sup 2}, approximately 2 standard deviations away from the CPT hypothesis of zero mass difference.
We report the most sensitive direct search for pair production of fourth-generation bottomlike chiral quarks (b{sup '}) each decaying promptly to tW. We search for an excess of events with an ...electron or muon, at least five jets (one identified as due to a b or c quark), and an imbalance of transverse momentum by using data from pp collisions collected by the CDF II detector at Fermilab with an integrated luminosity of 4.8 fb{sup -1}. We observe events consistent with background expectation, calculate upper limits on the b{sup '} pair-production cross section ({sigma}{sub bb-bar}{sup '} < or approx. 30 fb for m{sub b}{sup '}>375 GeV/c{sup 2}), and exclude m{sub b}{sup '}<372 GeV/c{sup 2} at 95% confidence level assuming a 100% branching ratio of b{sup '} to tW.
We present a search for a new narrow, spin-1, high mass resonance decaying to {mu}{sup +}{mu}{sup -}+X, using a matrix-element-based likelihood and a simultaneous measurement of the resonance mass ...and production rate. In data with 4.6 fb{sup -1} of integrated luminosity collected by the CDF detector in pp collisions at {radical}(s)=1960 GeV, the most likely signal cross section is consistent with zero at 16% confidence level. We therefore do not observe evidence for a high mass resonance and place limits on models predicting spin-1 resonances, including M>1071 GeV/c{sup 2} at 95% confidence level for a Z{sup '} boson with the same couplings to fermions as the Z boson.
We report on a measurement of b-hadron lifetimes in the fully reconstructed decay modes B{sup +}{yields}J/{psi}K{sup +}, B{sup 0}{yields}J/{psi}K{sup *}(892){sup 0}, B{sup 0}{yields}J/{psi}K{sub ...s}{sup 0}, and {Lambda}{sub b}{sup 0}{yields}J/{psi}{Lambda}{sup 0} using data corresponding to an integrated luminosity of 4.3 fb{sup -1}, collected by the CDF II detector at the Fermilab Tevatron. The measured lifetimes are {tau}(B{sup +})=1.639{+-}0.009(stat){+-}0.009(syst) ps, {tau}(B{sup 0})=1.507{+-}0.010(stat){+-}0.008(syst) ps, and {tau}({Lambda}{sub b}{sup 0})=1.537{+-}0.045(stat){+-}0.014(syst) ps. The lifetime ratios are {tau}(B{sup +})/{tau}(B{sup 0})=1.088{+-}0.009(stat){+-}0.004(syst) and {tau}({Lambda}{sub b}{sup 0})/{tau}(B{sup 0})=1.020{+-}0.030(stat){+-}0.008(syst). These are the most precise determinations of these quantities from a single experiment.
We search for the standard model Higgs boson produced with a Z boson in 4.1 fb{sup -1} of integrated luminosity collected with the CDF II detector at the Tevatron. In events consistent with the decay ...of the Higgs boson to a bottom-quark pair and the Z boson to electrons or muons, we set 95% credibility level upper limits on the ZH production cross section multiplied by the H{yields}bb branching ratio. Improved analysis methods enhance signal sensitivity by 20% relative to previous searches. At a Higgs boson mass of 115 GeV/c{sup 2} we set a limit of 5.9 times the standard model cross section.
The CMS muon barrel drift tubes system commissioning Abbiendi, G.; Amapane, N.; Battilana, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2009, 2009-1-00, Letnik:
598, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The CMS muon barrel drift tubes system has been recently fully installed and commissioned in the experiment. The performance and the current status of the detector are briefly presented and discussed.
We report on a search for Standard Model t-channel ans s-channel single top
quark production in p-pbar collisions at a center of mass energy of 1.96 TeV.
We use a data sample corresponding to 0.7 ...fb-1 recorded by the upgraded
Collider Detector at Fermilab (CDFII) and a data sample corresponding to 370
pb-1 recorded by D0. Both CDF and D0 find no significant evidence for
electroweak top quark production and set upper limits at the 95 % confidence
level on the production cross section
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