70 research outputs found
Observation of Bs0→J/ψK*(892)0 [B subscript s superscript 0 → J / psi K* (892) superscript 0] and Bs0→J/ψKS0 [B subscript s superscript 0 → J / psi K subscript s superscript 0 ] decays
No full textWe report the first observation of two Cabibbo-suppressed decay modes of the Bs0 [B subscript s superscript 0] meson. Using a sample of pp̅ collisions at √s=1.96 [square root of 1.96] TeV corresponding to 5.9 fb-1 [fb superscript -1] of integrated luminosity collected with the CDF II, the collider detector at the Fermilab Tevatron, we search for new Bs0 [B subscript s superscript 0] decay modes in a sample of events containing J/ψ→μ+μ- [J / psi→mu superscript + mu superscript -] decays. We reconstruct a Bs0→J/ψK*(892)0 [B subscript s superscript 0→J / psi K subscript s superscript 0] signal with K*(892)0→K+π- [K* (892) superscript 0 →K superscript + pi superscript -], observing a yield of 151±25 events with a statistical significance of 8.0σ [8.0 delta]. We also reconstruct a Bs0→J/ψKS0 [B subscript s superscript 0→J / psi K subscript s superscript 0] signal with KS0→π+π- [K subscript s superscript 0→ pi superscript + pi superscript -], observing a yield of 64±14 events with a statistical significance of 7.2σ [7.2 delta]. From these yields, we extract the branching ratios B(Bs0→J/ψK*(892)0)=(8.3±3.8)×10-5 [B (B subscript s superscript 0→J / psi K* (892) superscript 0) = (8.3±3.8) × 10 superscript -5] and B(Bs0→J/ψK0)=(3.5±0.8)×10-5 [B (B subscript s superscript 0→J / psi K superscript 0) = (3.5 ± 0.8) × 10 superscript -5], where statistical, systematic, and fragmentation-fraction uncertainties are included in the combined uncertainty.United States. Dept. of EnergyNational Science foundation (U.S.)Alfred P. Sloan Foundatio
Observation of the structure in the Mass Spectrum in cays
No full text7 pages, 2 figures, submited to Phys. Rev. LettInternational audienceThe observation of the structure in decays produced in collisions at \sqrt{s}=1.96~\TeV is reported with a statistical significance greater than 5 standard deviations. A fit to the mass spectrum is performed assuming the presence of a Breit-Wigner resonance. The fit yields a signal of resonance events, and resonance mass and width of 4143.4^{+2.9}_{-3.0}(\mathrm{stat})\pm0.6(\mathrm{syst})~\MeVcc and 15.3^{+10.4}_{-6.1}(\mathrm{stat})\pm2.5(\mathrm{syst})~\MeVcc respectively. The parameters of this resonance-like structure are consistent with values reported from an earlier CDF analysis
Improved determination of the sample composition of dimuon events produced in p(p)over-bar collisions at root s=1.96 TeV
No full textWe use a new method to estimate with 5% accuracy the contribution of pion and kaon in-flight-decays to the dimuon data set acquired with the CDF detector. Based on this improved estimate, we show that the total number and the properties of the collected dimuon events are not yet accounted for by ordinary sources of dimuons which also include the contributions, as measured in the data, of heavy flavor, Υ{hooked}, and Drell-Yan production in addition to muons mimicked by hadronic punchthrough. The number of unaccounted events corresponds to (12.8±3.2)% of the bb̄ production. We find that (23±6)% of the unaccounted events contain additional muon candidates. For comparison, this fraction is (6.9±0.4)% for events due to bb̄ production. © 2011 The Author(s)
Inclusive Search for Standard Model Higgs Boson Production in the WW Decay Channel Using the CDF II Detector
No full textWe present a search for standard model (SM) Higgs boson production using pp̅ collision data at √s=1.96 TeV, collected with the CDF II detector and corresponding to an integrated luminosity of 4.8 fb[superscript -1]. We search for Higgs bosons produced in all processes with a significant production rate and decaying to two W bosons. We find no evidence for SM Higgs boson production and place upper limits at the 95% confidence level on the SM production cross section (σ[subscript H]) for values of the Higgs boson mass (m[subscript H]) in the range from 110 to 200 GeV. These limits are the most stringent for m[subscript H]>130 GeV and are 1.29 above the predicted value of σ[subscript H] for m[subscript H]=165 GeV.Academy of FinlandSlovak R&D AgencyPrograma Consolider-Ingenio 2010, SpainMinisterio de Ciencia e Innovación, SpainRussian Foundation for Basic ResearchInstitut National de Physique Nucleaire et Physique des Particules/CNRSScience and Technology Facilities Council and the Royal Society, UKNational Research Foundation of KoreaWorld Class University ProgramBundesministerium für Bildung und Forschung, GermanyAlfred P. Sloan FoundationSwiss National Science FoundationNational Science Council of the Republic of ChinaNatural Sciences and Engineering Research Council of CanadaMinistry of Education, Culture, Sports, Science and Technology of JapanItalian Istituto Nazionale di Fisica NucleareNational Science FoundationUnited States. Dept. of Energ
Measurement of the Lambda(0)(b) Lifetime in Lambda(0)(b) -> Lambda(+)(c)pi(-) Decays in p(p)over-bar Collisions at root s=1.96 TeV
No full textWe report a measurement of the lifetime of the Lambda(0)(b) baryon in decays to the Lambda(+)(c)pi(-) final state in a sample corresponding to 1.1 fb(-1) collected in p (p) over bar collisions at root s = 1.96 TeV by the CDF II detector at the Tevatron collider. Using a sample of about 3000 fully reconstructed Lambda(0)(b) events we measure tau(Lambda(0)(b) ) = 1.401 +/- 0.046(stat) +/- 0.035(syst) ps (corresponding to c tau(Lambda(0)(b)) = 420.1 +/- 13.7(stat) +/- 10.6(syst) mu m, where c is the speed of light). The ratio of this result and the world average B-0 lifetime yields tau(Lambda(0)(b))/tau(B-0) = 0.918 +/- 0.038 (stat) and (syst), in good agreement with recent theoretical predictions
Measurement of d sigma/dy of Drell-Yan e(+)e(-) pairs in the Z mass region from p(p)over-bar collisions at root s=1.96 TeV
No full textWe report on a CDF measurement of the total cross section and rapidity distribution, d sigma/dy, for gamma*/Z -\u3e e(+)e(-) events in the Z boson mass region (66 \u3c M-ee \u3c 116 GeV/c(2)) produced in p (p) over bar collisions at root s = 1.96 TeV with 2.1 fb(-1) of integrated luminosity. The measured cross section of 257 +/- 16 pb and d sigma/dy distribution are compared with Next-to-Leading-Order (NLO) and Next-to-Next-to-Leading-Order (NNLO) QCD theory predictions with CTEQ and MRST/MSTW parton distribution functions (PDFs). There is good agreement between the experimental total cross section and d sigma/dy measurements with theoretical calculations with the most recent NNLO PDFs. (C) 2010 Elsevier B.V. All rights reserved
Search for R-Parity Violating Decays of Sneutrinos to e mu, mu tau, and e tau Pairs in p(p)over-bar Collisions at root s=1.96 TeV
No full textWe present a search for supersymmetric neutrino (nu) over tilde production using the Tevatron p (p) over bar collision data collected with the CDF II detector and corresponding to an integrated luminosity of 1 fb(-1). We focus on the scenarios predicted by the R-parity violating (RPV) supersymmetric models in which sneutrinos decay to two charged leptons of different flavor. With the data consistent with the standard model expectations, we set upper limits on sigma(p (p) over bar -> (nu) over tilde) BR((nu) over tilde -> e mu, mu tau, e tau) and use these results to constrain the RPV couplings as a function of the sneutrino mass
Exclusion of an Exotic Top Quark with-4/3 Electric Charge Using Soft Lepton Tagging
No full textWe present a measurement of the electric charge of the top quark using p (p) over bar collisions corresponding to an integrated luminosity of 2: 7 fb(-1) at the CDF II detector. We reconstruct t (t) over bar events in the lepton + jets final state. We use soft lepton taggers to determine the flavor of the b jets, which we use to reconstruct the top quark's electric charge and exclude an exotic top quark with -4/3 charge at 95% confidence level. This is the strongest exclusion of the exotic charge scenario and the first to use soft leptons for this purpose
Measurement of the top quark mass and pp̅ →tt̅ cross section in the all-hadronic mode with the CDF II detector
No full textWe present a measurement of the top quark mass and of the top-antitop (tt̅ ) pair production cross section using pp̅ data collected with the CDF II detector at the Tevatron Collider at the Fermi National Accelerator Laboratory and corresponding to an integrated luminosity of 2.9 fb-1. We select events with six or more jets satisfying a number of kinematical requirements imposed by means of a neural-network algorithm. At least one of these jets must originate from a b quark, as identified by the reconstruction of a secondary vertex inside the jet. The mass measurement is based on a likelihood fit incorporating reconstructed mass distributions representative of signal and background, where the absolute jet energy scale (JES) is measured simultaneously with the top quark mass. The measurement yields a value of 174.8±2.4(stat+JES)-1.0+1.2(syst) GeV/c2, where the uncertainty from the absolute jet energy scale is evaluated together with the statistical uncertainty. The procedure also measures the amount of signal from which we derive a cross section, σtt̅ =7.2±0.5(stat)±1.0(syst)±0.4(lum) pb, for the measured values of top quark mass and JES.United States Department of EnergyNational Science FoundationIstituto Nazionale di Fisica Nucleare of ItalyMinistry of Education, Culture, Sports, Science and Technology of JapanNatural Sciences and Engineering Research Council of CanadaNational Science Council of the Republic of ChinaSwiss National Science FoundationAlfred P. Sloan FoundationBundesministerium für Bildung und Forschung, GermanyWorld Class University Program (Korea)National Research Foundation of KoreaScience and Technology Facilities Council, United KingdomRoyal Society, United KingdomInstitut National de Physique Nucleaire et Physique des Particules/CNRSRussian Foundation for Basic ResearchMinisterio de Ciencia e Innovación, SpainPrograma Consolider-Ingenio 2010, SpainSlovak R&D AgencyAcademy of Finlan
Measurement of W-Boson Polarization in Top-Quark Decay in p(p)over-bar Collisions at root s=1.96 TeV
No full textWe report measurements of the polarization of W bosons from top-quark decays using 2.7 fb(-1) of p (p) over bar collisions collected by the CDF II detector. Assuming a top-quark mass of 175 GeV/c(2), three measurements are performed. A simultaneous measurement of the fraction of longitudinal (f(0)) and right-handed (f(0)) W bosons yields the model- independent results f(0) =0. 88 +/- 0.11(stat) +/- 0.06(syst) and f(+) = 0.15 +/- 0.07(stat) +/- 0.06(syst) with a correlation coefficient of -0.59. A measurement of f(0) [f(+)] constraining f(+) [f(0)] to its standard model value of 0.0 [0.7] yields f(0) 0.70 + 0.07(stat) +/- 0.04(syst) [f(+) - 0.01 +/- 0.02(stat) +/- 0.05(syst)]. All these results are consistent with standard model expectations. We achieve the single most precise measurements of f(0) for both the model- independent and modeldependent determinations
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