We present a search for neutral Higgs bosons varphi decaying into bb, produced in association with b quarks in pp collisions. This process could be observable in supersymmetric models with high ...values of tan beta . The event sample corresponds to 2.6 fb super(-1) of integrated luminosity collected with the CDF II detector at the Fermilab Tevatron collider. We search for an enhancement in the mass of the two leading jets in events with three jets identified as coming from b quarks using a displaced vertex algorithm. A data-driven procedure is used to estimate the dijet mass spectrum of the nonresonant multijet background. The contributions of backgrounds and a possible Higgs boson signal are determined by a two-dimensional fit of the data, using the dijet mass together with an additional variable which is sensitive to the flavor composition of the three tagged jets. We set mass-dependent limits on sigma(pp arrow right varphib) x Bernoulli(varphi arrow right bb) which are applicable for a narrow scalar particle varphi produced in association with b quarks. We also set limits on tan beta in supersymmetric Higgs models including the effects of the Higgs boson width.
We report a measurement of the lifetime of the Lambda(b)(0) baryon in decays to the Lambda(c)(+)pi(-) final state in a sample corresponding to 1.1 fb(-1) collected in pp collisions at square root of ...s = 1.96 TeV by the CDF II detector at the Tevatron collider. Using a sample of about 3000 fully reconstructed Lambda(b)(0) events we measure tau(Lambda(b)(0)) = 1.401 +/- 0.046(stat) +/- 0.035(syst) ps (corresponding to ctau(Lambda(b)(0)) = 420.1 +/- 13.7(stat) +/- 10.6(syst) microm, where c is the speed of light). The ratio of this result and the world average B(0) lifetime yields tau(Lambda(b)(0))/tau(B(0)) = 0.918 +/- 0.038 (stat) and (syst), in good agreement with recent theoretical predictions.
We present the first general search for new heavy particles, X, which decay via X --> WZ0 --> e(nu)+jj as a function of M(X) and Gamma(X) in pp collisions at square roots = 1.8 TeV. No evidence is ...found for production of X in 110 pb(-1) of data collected by the Collider Detector at Fermilab. General cross section limits are set at the 95% C.L. as a function of mass and width of the new particle. The results are further interpreted as mass limits on the production of new heavy charged vector bosons which decay via W' --> WZ0 in an extended gauge model as a function of the width, Gamma(W'), and mixing factor between the W' and the standard model W bosons.
An associative memory full-custom CMOS VLSI chip (AMchip), to be used in fast trigger systems for pattern recognition, has been designed and is being tested. The AMchip is a full-custom associative ...memory IC developed for high energy physics. It contains about 140000 MOS transistors, has been realized in 1.5- mu m, double-metal, silicon gate CMOS technology, and is housed in a 120-pin package. The AMchip has been designed to be used with any kind of detector which provides in the output the hit coordinates. Some preliminary tests have been done on the 55 prototypes received from the ES2 (European silicon structures) foundry. The performance test, limited by the equipment used, has shown that the AMchip can work with a 20-MHz clock.< >
We present the results of a search in pp collisions at sqrts = 1.8 TeV for anomalous production of events containing a photon and a lepton (e or mu), both with large transverse energy, using 86 ...pb(-1) of data collected with the Collider Detector at Fermilab during the 1994-1995 collider run at the Fermilab Tevatron. The presence of large missing transverse energy (E(T)), additional photons, or additional leptons in these events is also analyzed. The results are consistent with standard model expectations, with the possible exception of photon-lepton events with large E(T), for which the observed total is 16 events and the expected mean total is 7.6+/-0.7 events.
We report on a search for a spin-zero non-standard-model particle in proton-antiproton collisions collected by the Collider Detector at Fermilab at a center-of-mass-energy of 1.96 TeV. This particle, ...the \(\phi\) boson, is expected to decay into a bottom-antibottom quark pair and to be produced in association with at least one bottom quark. The data sample consists of events with three jets identified as initiated by bottom quarks and corresponds to \(5.4~\text{fb}^{-1}\) of integrated luminosity. In each event, the invariant mass of the two most energetic jets is studied by looking for deviations from the multijet background, which is modeled using data. No evidence is found for such particle. Exclusion upper limits ranging from 20 to 2 pb are set for the product of production cross sections times branching fraction for hypothetical \(\phi\) boson with mass between 100 and 300 GeV/\(c^2\). These are the most stringent constraints to date.
A combined mass and particle identification fit is used to make the first observation of the decay B(s)(0) --> D(s)(+/-)K(-/+) and measure the branching fraction of B(s)(0) --> D(s)(+/-)K(-/+) ...relative to B(s)(0) --> D(s)(+)pi(-). This analysis uses 1.2 fb(-1) integrated luminosity of pp collisions at square root(s) = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron collider. We observe a B(s)(0) --> D(s)(+/-)K(-/+) signal with a statistical significance of 8.1 sigma and measure B(B(s)(0) --> D(s)(+/-)K(-/+) /B(B(s)(0) --> D(s)(+)pi(-) 0.097+/-0.018(stat) +/- 0.009(syst).
We report the first observation of diffractive J/psi(--> mu+mu-) production in pp collisions at root squares = 1.8 TeV. Diffractive events are identified by their rapidity gap signature. In a sample ...of events with two muons of transverse momentum p(mu)T>2 GeV/c within the pseudorapidity region /eta/ < 1.0, the ratio of diffractive to total J/psi production rates is found to be R(J/psi) = 1.45 +/- 0.25%. The 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.
We report a study of the decays B0 --> J/psiK(*)0pi(+)pi(-), which involve the creation of a uu or dd quark pair in addition to a b -->c(cs) decay. The data sample consists of 110 pb(-1) of pp ...collisions at square roots = 1.8 TeV collected by the CDF detector at the Fermilab Tevatron collider during 1992-1995. We measure the branching fractions to be B(B0 --> J/psiK(*0)pi(+)pi(-)) = (6.6 +/- 1.9 +/- 1.1)x10(-4) and B(B0 --> J/psiK0pi(+)pi(-)) = (10.3 +/- 3.3 +/- 1.5)x10(-4). Evidence is seen for contributions from psi(2S)K(*)0, J/psiK0rho(0), J/psiK(*+)pi(-), and J/psiK1(1270).
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