Searches for new physics in events with a photon and b-quark jet at CDF

We have searched for evidence of physics beyond the standard model in events that include an energetic photon and an energetic b-quark jet, produced in 85 pb(-1) of (p) over barp collisions at 1.8 TeV at the Tevatron Collider at Fermilab. This signature, containing at least one gauge boson and a third-generation quark, could arise in the production and decay of a pair of new particles, such as those predicted by supersymmetry, leading to a production rate exceeding standard model predictions. We also search these events for anomalous production of missing transverse energy, additional jets and leptons (e, mu and tau), and additional b quarks. We find no evidence for any anomalous production of gammab or gammab + X events, We present limits on two supersymmetric models: a model where the photon is produced in the decay (χ) over tilde (0)(2)→gamma(χ) over tilde (0)(1), and a model where the photon is produced in the neutralino decay into the gravitino LSP, (χ) over tilde (0)(1)→gamma(G) over tilde. We also present our limits in a model-independent form and test methods of applying model-independent limits

Measurement of B-meson lifetimes using fully reconstructed B decays produced in p(p)over-bar collisions at root s=1.8 TeV

We present an improved measurement of b-meson lifetimes using fully reconstructed B-decays produced in p(p) over bar collisions at roots = 1.8 TeV, using 114 pb(-1) of data collected at the Collider Detector at Fermilab. We obtain tau(B+) = 1.636+/-0.058(stat)+/-0.025(syst) ps, tau(B-0) = 1.497+/-0.073(stat)+/-0.032(syst) ps and for the lifetime ratio tau(B+)/tau(B-0) = 1.093+/-0.066(stat)+/-0.028(syst)

Observation of diffractive J/psi production at the Fermilab Tevatron

We report the first observation of diffractive J/psi(→ mu (+)mu (-)) production in [(p)power bar] collisions at roots = 1.8 TeV. Diffractive events are identified by their rapidity gap signature. In a sample of events with two muons of transverse momentum p(T)(mu) gt 2 GeV/c within the pseudorapidity region \ eta \ lt 1.0, the ratio of diffractive to total J/[psi] production rates is found to be R-J/psi = [1.45 +/- 0.25]%. ne ratio R-J/psi(X) is presented as a function of x-Bjorken. By combining it with our previously measured corresponding ratio R-jj(x) for diffractive dijet production, we extract a value of 0.59 +/- 0.15 for the gluon fraction of the diffractive structure function of the proton

Measurement of the B⁺ total cross section and B⁺ differential cross section d sigma/dp_T in p(p)over-bar collisions at root s=1.8 TeV

We present measurements of the B+ meson total cross section and differential cross section dsigma/dp(T). The measurements use a 98+/-4 pb(-1) sample of p (p) over bar collisions at roots = 1.8 TeV collected by the CDF detector. Charged B meson candidates are reconstructed through the decay B+/- → J/psiK(+/-) with J/psi → mu(+)mu(-). The total cross section, measured in the central rapidity region \y\ lt 1.0 for p(T)(B) gt 6.0 GeV/c, is 3.6+/-0.6(stat + syst) mub. The measured differential cross section is substantially larger than typical QCD predictions calculated to next-to-leading order

Search for a W' boson decaying to a top and bottom quark pair in 1.8 TeV p(p)over-bar collisions

We report the results of a search for a W-' boson produced in p (p) over bar collisions at a center-of-mass energy of 1.8 TeV using a 106 pb(-1) data sample recorded by the Collider Detector at Fermilab. We observe no significant excess of events above background for a W' boson decaying to a top and bottom quark pair. In a model where this boson would mediate interactions involving a massive right-handed neutrino (nu(R)) and have standard model strength couplings, we use these data to exclude a W' boson with mass between 225 and 536 GeV/c(2) at 95% confidence level for M-W(') gt M-nuR and between 225 and 566 GeV/c(2) at 95% confidence level for M-W(') lt M-nuR

Search for radiative b-hadron decays in p(p)over-bar collisions at root s=1.8 TeV

We have performed a search for radiative b-hadron decays using events produced in p (p) over bar collisions at roots=1.8 TeV and collected by the Collider Detector at Fermilab. The decays we considered were (B) over bar (0)(d)→(K) over bar*(0)(→K(-)pi(+))gamma, (B) over bar (0)(s)→phi(→K+K-)gamma, Lambda(b)(0)→Lambda(→ppi(-))gamma, and their charge conjugates. Two independent methods to identify photons from such decays were employed. In the first method, the photon was detected in the electromagnetic calorimeter. In the second method, the photon was identified by an electron-positron pair produced through the external photon conversion before the tracking detector volume. By combining the two methods we obtain upper limits on the branching fractions for the (B) over bar (0)(d), (B) over bar (0)(s), and Lambda(b)(0) radiative decays which, at the 95% confidence level, are found to be B((B) over bar (0)(d)→(K) over bar*(0)gamma) lt 1.4x10(-4), B((B) over bar (0)(s)→phigamma) lt 1.6x10(-4), and B(Λ(0)(b)→Lambdagamma) lt 1.9x10(-3)

Properties of jets in Z boson events from 1.8 TeV p\u304p collisions

We present a study of events with Z bosons and hadronic jets produced in p\uafp collisions at a center-of-mass energy of 1.8 TeV. The data consist of 6708 Z\u2192e+e 12 decays from 106pb 121 of integrated luminosity collected using the CDF detector at the Fermilab Tevatron Collider. The Z+ 65n jet cross sections and jet production properties have been measured for n=1 to 4. The data are compared to predictions of leading-order QCD matrix element calculations with added gluon radiation and simulated parton fragmentation

Inclusive jet cross section in p\u304p collisions at 1as = 1.8 TeV

The inclusive jet differential cross section has been measured for jet transverse energies, ET, from 15 to 440 GeV, in the pseudorapidity region 0.1 64|\u3b7| 640.7. The results are based on 19.5pb 121 of data collected by the CDF Collaboration at the Fermilab Tevatron collider. The data are compared with QCD predictions for various sets of parton distribution functions. The cross section for jets with ET>200GeV is significantly higher than current predictions based on O(\u3b13s) perturbative QCD calculations. Various possible explanations for the high- ET excess are discussed

Measurement of the \u3b3 + D*\ub1 cross section in p\u304p collisions at 1as = 1.8 TeV

We have measured the cross section of gamma + D-*+/- production in <(p)over bar p> collisions at root s = 1.8 TeV using the Collider Detector at Fermilab. In this kinematic region, the Compton scattering process (g(c) --> gamma(c)) is expected to dominate and thus provide a direct link to the charm quark density in the proton. From the 45 +/- 18 gamma + D-*+/- candidates in a 16.4 pb(-1) data sample, we have determined the production cross section to be 0.38 +/- 0.15(stat) +/- 0.11(syst) nb for the rapidity range y(D-*+/-) < 1.2 and y(gamma) < 0.9, and for the transverse momentum range p(T)(D-*+/-) > 6 GeV/c and 16 < p(T)(gamma) < 40 GeV/c. The measured cross section is compared to a theoretical prediction

Search for the supersymmetric partner of the top quark in pp\u304 collisions at 1as=1.8 TeV

We report on a search for the supersymmetric partner of the top quark (top squark) produced in tt\u304 events using 110 pb-1 of pp\u304 collisions at 1as = 1.8 TeV recorded with the Collider Detector at Fermilab. In the case of a light top squark, the decay of the top quark into a top squark plus the lightest supersymmetric particle (LSP) could have a significant branching ratio. The observed events are consistent with standard model tt\u304 production and decay. Hence, we set limits on the branching ratio of the top quark decaying into a top squark plus LSP, excluding branching ratios above 45% for a LSP mass up to 40 GeV/c2