342 research outputs found

    Search for New Particles Decaying into b¯b and Produced in Association with <i>W</i> Bosons Decaying into <i>eν</i> or <i>μν</i> at the Fermilab Tevatron

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    We search for new particles that decay into b¯b and are produced with W bosons in p¯p collisions at √s=1.8TeV. The search uses 109±7pb⁻¹ accumulated by the CDF experiment at Fermilab. We select events with an eν or μν, and two jets, one of them b tagged. The number of events and the two-jet mass distribution are consistent with expectations. Using W+Higgs production as a model for the acceptance, we set an upper limit on the production cross section times branching ratio for the new particle ranging from 14 to 19 pb (95% C.L.) as the particle mass varies from 70 to 120GeV/c²

    Observation of B-c mesons in p(p)over-bar collisions at root s=1.8 TeV

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    We report the observation of bottom-charmed mesons B-c in 1.8 TeV collisions using the CDF detector at the Fermilab Tevatron. The B-c mesons were found through their semileptonic decays, B-c(+/-) --> J/psi l(+/-)X. A fit to the J/psi l mass distribution yielded 20.4(-5.5)(+6.2) events from B-c mesons. A test of the null hypothesis, i.e., an attempt to fit the data with background alone, was rejected at the level of 4.8 standard deviations. By studying the quality of the fit as a function of the assumed B-c mass, we determined M(B-c) = 6.40 +/- 0.39 (stat.)+/-0.13 (syst) GeV/c(2). From the distribution of trilepton intersection points in the plane transverse to the beam direction we measured the B-c lifetime to be tau(B-c) = 0.46(-0.16)(+0.18) (stat)+/-0.03 (syst) ps. We also measured the ratio of production cross section times branching fraction for Bc+ --> J/psi l(+) nu relative to that for B+ --> J/psi K+ to be sigma(B-c) X B(B-c --> J/psi l nu)/sigma(B) X B(B-->J/psi K) = 0.132(-0.037)(+0.041) (stat)+/-0.031 (syst)(-0.020)(+0.032)(lifetime). [S0556-2821(98)01421-0]

    Measurement of the Lambda(b)(0) lifetime using Lambda(b)(0)->Lambda(c)(+)l(-)(nu)over-bar

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    The lifetime of Lambda(b)(0) is measured using the semileptonic decay Lambda(b)(0)-->Lambda(c)(+)l(-)nu(-), where the Lambda(c)(+) is reconstructed through its decay Lambda(c)(+) --> pK(-)pi(+). The data were collected by the CDF detector at the Tevatron Collider during 1992-1995 and correspond to an integrated luminosity of 110 pb(-1) of collisions at root s=1.8 TeV. From a fit to the decay length distribution of the Lambda(c)-lepton system from 197+/-25 signal events, the lifetime of Lambda(b)(0) is measured to be 1.32+/-0.15+/- 0.07 ps

    Observation of the B-c meson in p(p)over-bar collisions at root s=1.8 TeV

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    We have observed bottom-charm mesons via the decay mode B-c(+/-) --> J/psi l(+/-)v in 1.8 TeV p (p) over bar collisions using the CDF detector at the Fermilab Tevatron. A fit of background and signal contributions to the J/psi l mass distribution yielded 20.4(-5.5)(+6.2) events from B-c mesons. A fit to the same distribution with background alone was rejected at the level of 4.8 standard deviations. We measured the B-c(+) mass to be 6.40 +/- 0.39(stat) +/- 0.13(syst) GeV/c(2) and the B-c(+) lifetime to be 0.46(-0.16)(+0.18)(stat) +/- 0.03(syst) ps. Our measured yield (production cross section times branching ratio) for B-c(+) --> J/psi l(+)v relative to that for B+ --> J/psi K+ is 0.132(-0.037)(+0.041)(stat) +/- 0.031 (syst)(-0.020)(+0.032)(lifetime)

    Production of J/psi mesons from chi(c) meson decays in p(p)over-bar collisions at root s=1.8 TeV

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    We have measured the fraction of J/psi mesons originating from chi(c) meson decays in p (p) over bar collisions at root s = 1.8 TeV. The fraction, for P-T/(J/psi) > 4.0 GeV/c and \(eta) over dot(J/psi) < 0.6, not including contributions from b flavored hadrons, is 29.7% +/- 1.7%(stat) +/- 5.7%(syst). We have determined the cross sections for J/psi mesons originating from chi(c) decays and for directly produced J/psi mesons. We have found that direct J/psi production is in excess of the prediction of the color singlet model by the same factor found for direct psi(2S) production

    Measurement of the Semileptonic Branching Ratio of Charm Hadrons Produced in Z0ccˉZ^{0} \to c\bar{c} Decays

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    The inclusive charm hadron semileptonic branching fractions B(c to e) and B(c to mu) in Z to ccbar events have been determined using 4.4 million hadronic Z decays collected with the OPAL detector at LEP. A charm-enriched sample is obtained by selecting events with reconstructed D*+- mesons. Using leptons found in the hemisphere opposite that of the D*+- mesons, the semileptonic branching fractions of charm hadrons are measured to be B(c to e) = 0.103 +-0.009 +0.009 -0.008 and B(c to mu) = 0.090 +-0.007 +0.007 -0.006 where the first errors are in each case statistical and the others systematic. Combining these measurements, an inclusive semileptonic branching fraction of charm hadrons of B(c to l) = 0.095 +-0.006 +0.007 -0.006 is obtained.The inclusive charm hadron semileptonic branching fractions B(c to e) and B(c to mu) in Z to ccbar events have been determined using 4.4 million hadronic Z decays collected with the OPAL detector at LEP. A charm-enriched sample is obtained by selecting events with reconstructed D*+- mesons. Using leptons found in the hemisphere opposite that of the D*+- mesons, the semileptonic branching fractions of charm hadrons are measured to be B(c to e) = 0.103 +-0.009 +0.009 -0.008 and B(c to mu) = 0.090 +-0.007 +0.007 -0.006 where the first errors are in each case statistical and the others systematic. Combining these measurements, an inclusive semileptonic branching fraction of charm hadrons of B(c to l) = 0.095 +-0.006 +0.007 -0.006 is obtained

    Measurement of the semileptonic branching ratio of charm hadrons produced in Z0 ---> c anti-c decays

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    Contains fulltext : 125089.pdf (Author’s version preprint ) (Open Access) Contains fulltext : 125089.pdf (Publisher’s version ) (Open Access
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