Top Quark Mass Measurement in the lepton plus jets Channel Using a Matrix Element Method and in situ Jet Energy Calibration

A precision measurement of the top quark mass m(t) is obtained using a sample of t (t) over bar events from p (p) over bar collisions at the Fermilab Tevatron with the CDF II detector. Selected events require an electron or muon, large missing transverse energy, and exactly four high-energy jets, at least one of which is tagged as coming from a b quark. A likelihood is calculated using a matrix element method with quasi-Monte Carlo integration taking into account finite detector resolution and jet mass effects. The event likelihood is a function of mt and a parameter Delta(JES) used to calibrate the jet energy scale in situ. Using a total of 1087 events in 5.6 fb(-1) of integrated luminosity, a value of m(t) 173.0 +/- 1.2 GeV/c(2) is measured

Measurements of bottom-antibottom azimuthal production correlations in proton-antiproton collisions at root s=1.8 TeV RID C-1693-2008 RID E-4473-2011

We have measured the azimuthal angular correlation of b (b) over bar production, using 86.5 pb(-1) of data collected by Collider Detector at Fermilab (CDF) in p (p) over bar collisions at root s = 1.8 TeV during 1994-1995. In high-energy p (p) over bar collisions, such as at the Tevatron, b (b) over bar production can be schematically categorized into three mechanisms. The leading-order (LO) process is "flavor creation," where both b and (b) over bar quarks substantially participate in the hard scattering and result in a distinct back-to-back signal in final state. The "flavor excitation" and the "gluon splitting" processes, which appear at next-leading-order (NLO), are known to make a comparable contribution to total b (b) over bar cross section, while providing very different opening angle distributions from the LO process. An azimuthal opening angle between bottom and antibottom, Delta phi, has been used for the correlation measurement to probe the interaction creating b (b) over bar pairs. The Delta phi distribution has been obtained from two different methods. One method measures the Delta phi between bottom hadrons using events with two reconstructed secondary vertex tags. The other method uses b (b) over bar -> (J/psi X)(lX(')) events, where the charged lepton (l) is an electron (e) or a muon (mu), to measure Delta phi between bottom quarks. The b (b) over bar purity is determined as a function of Delta phi by fitting the decay length of the J/psi and the impact parameter of the center dot. Both methods quantify the contribution from higher-order production mechanisms by the fraction of the b (b) over bar pairs produced in the same azimuthal hemisphere, f(toward). The measured f(toward) values are consistent with both parton shower Monte Carlo and NLO QCD predictions

Comparison of three-jet events in p(p)over-bar collisions at root s=1.8 TeV to predictions from a next-to-leading order QCD calculation

The properties of three-jet events with total transverse energy greater than 320 GeV and individual jet energy greater than 20 GeV have been analyzed and compared to absolute predictions from a next-to-leading order (NLO) perturbative QCD calculation. These data, of integrated luminosity 86 pb -1, were recorded by the CDF Experiment for pp collisions at √s = 1.8 TeV This study tests a model of higher order QCD processes that result in gluon emission and may give some indication of the magnitude of the contribution of processes higher than NLO. The total cross section is measured to be 466 ± 3(stat.)-70+207(syst.) pb. The differential cross section is furthermore measured for all kinematically accessible regions of the Dalitz plane, including those for which the theoretical prediction is unreliable. While the measured cross section is consistent with the theoretical prediction in magnitude, the two differ somewhat in shape in the Dalitz plane. © 2005 The American Physical Society

K-S(0) and Lambda(0) production studies in p(p)over-bar collisions at root s=1800 and 630 GeV

We present a study of the production of K_s^0 and Lambda^0 in inelastic pbar-p collisions at sqrt(s)= 1800 and 630 GeV using data collected by the CDF experiment at the Fermilab Tevatron. Analyses of K_s^0 and Lambda^0 multiplicity and transverse momentum distributions, as well as of the dependencies of the average number and of K_s^0 and Lambda^0 on charged particle multiplicity are reported. Systematic comparisons are performed for the full sample of inelastic collisions, and for the low and high momentum transfer subsamples, at the two energies. The p_T distributions extend above 8 GeV/c, showing a higher than previous measurements. The dependence of the mean K_s^0(Lambda^0) p_T on the charged particle multiplicity for the three samples shows a behavior analogous to that of charged primary tracks.Comment: 47 pages, 20 figures, to be submitted to Phys.Rev.

Measurement of the gamma gamma* -> eta c transition form factor

We study the reaction e(+)e(-) -> e(+)e(-) eta(c), eta(c) -> K(S)K(+/-)pi(-/+) and obtain eta(c) mass and width values 2982.2 +/- 0.4 +/- 1.6 MeV/c(2) and 31.7 +/- 1.2 +/- 0.8 MeV, respectively. We find Gamma(eta(c) -> gamma gamma)B(eta(c) -> KK pi) = 0.374 +/- 0.009 +/- 0.031 keV, and measure the gamma gamma* -> eta(c) transition form factor in the momentum transfer range from 2 to 50 GeV(2). The analysis is based on 469 fb(-1) of integrated luminosity collected at PEP-II with the BABAR detector at e(+)e(-) center-of-mass energies near 10.6 GeV. RI Patrignani, Claudia/C-5223-2009; Neri, Nicola/G-3991-2012; Monge, Maria Roberta/G-9127-201

Searches for Lepton flavor violation in the decays tau(+/-) -> e(+/-)gamma and tau(+/-) -> mu(+/-)gamma

Searches for lepton-flavor-violating decays of a tau lepton to a lighter mass lepton and a photon have been performed with the entire data set of (963 +/- 7) x 10(6) tau decays collected by the BABAR detector near the Y(4S), Y(3S) and Y(2S) resonances. The searches yield no evidence of signals and we set upper limits on the branching fractions of B(tau(+/-) -> e(+/-)gamma) mu(+/-)gamma) < 4.4 X 10(-8) at 90% confidence level

Search for B^{+}→ℓ^{+}ν_{ℓ} recoiling against B^{-}→D^{0}ℓ^{-}ν[over ¯]X

We present a search for the decay B+→ℓ+νℓ(ℓ=τ,μ, or e) in (458.9±5.1)×106 BB̅ pairs recorded with the BABAR detector at the PEP-II B-factory. We search for these B decays in a sample of B+B- events where one B-meson is reconstructed as B-→D0ℓ-ν̅ X. Using the method of Feldman and Cousins, we obtain B(B+→τ+ντ)=(1.7±0.8±0.2)×10-4, which excludes zero at 2.3σ. We interpret the central value in the context of the standard model and find the B meson decay constant to be fB2=(62±31)×103  MeV2. We find no evidence for B+→e+νe and B+→μ+νμ and set upper limits at the 90% C.L. B(B+→e+νe)<0.8×10-5 and B(B+→μ+νμ)<1.1×10-5

Search for the supersymmetric partner of the top quark in p(p)over-bar collisions at root s=1.8 TeV

We report on a search for the supersymmetric partner of the top quark (top squark) produced in t (t) over bar events using 110 ph(-1) of p (p) over bar collisions at roots = 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 t (t) over bar 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 30 GeV/c(2)