The Forward Tracking: Algorithm and Performance Studies

This note describes the so-called Forward Tracking. This algorithm uses as input track seeds reconstructed in the VELO (Vetex Locator) and searches for associated tracks in the inner and outer tracker of the T stations based on a Hough Transformation approach. We describe in detail the implementation of the algorithm as it is in Brunel version 30r14 and the according performance on DC06 data

Measurement of the ratio of branching fractions B(B±→J/ ψπ±)/B(B±→J/ψK±)

We report a measurement of the ratio of branching fractions of the decays B±→J/ψπ± and B±→J/ψK± using the CDF II detector at the Fermilab Tevatron Collider. The signal from the Cabbibo-suppressed B±→J/ψπ± decay is separated from B±→J/ψK± using the B±→J/ψK± invariant mass distribution and the kinematical differences of the hadron track in the two decay modes. From a sample of 220pb-1 of pp̄ collisions at s=1.96TeV, we observe 91±15 B±→J/ψπ± events together with 1883±34 B±→J/ψK± events. The ratio of branching fractions is found to be B(B±→J/ψπ±)/ B(B±→J/ψK±)=(4.86±0.82(stat)±0.15(syst))%. © 2009 The American Physical Society.This work was supported by the U.S. Department of Energy and the National Science Foundation; the Italian Istituto Nazionale di Fisica Nucleare; the Ministry of Education, Culture, Sports, Science and Technology of Japan; the Natural Sciences and Engineering Research Council of Canada; the National Science Council of the Republic of China; the Swiss National Science Foundation; the A. P. Sloan Foundation; the Bundesministerium für Bildung und Forschung, Germany; the Korean Science and Engineering Foundation and the Korean Research Foundation; the Particle Physics and Astronomy Research Council and the Royal Society, UK; the Russian Foundation for Basic Research; the Comisión Interministerial de Ciencia y Tecnología, Spain; in part by the European Community’s Human Potential Programme under Contract No. HPRNCT-2002-00292; and the Academy of Finland

Top quark mass measurement using the template method at CDF

We present a measurement of the top quark mass in the lepton+jets and dilepton channels of $t\bar{t}$ decays using the template method. The data sample corresponds to an integrated luminosity of 5.6 fb$^{-1}$ of $p\bar{p}$ collisions at Tevatron with $\sqrt{s}=1.96$ TeV, collected with the CDF II detector. The measurement is performed by constructing templates of three kinematic variables in the lepton+jets and two kinematic variables in the dilepton channel. The variables are two reconstructed top quark masses from different jets-to-quarks combinations and the invariant mass of two jets from the $W$ decay in the lepton+jets channel, and a reconstructed top quark mass and $m_{T2}$, a variable related to the transverse mass in events with two missing particles, in the dilepton channel. The simultaneous fit of the templates from signal and background events in the lepton+jets and dilepton channels to the data yields a measured top quark mass of $M_{top} = 172.1 \pm 1.1(stat) \pm 0.9(syst).$Comment: submitted to Phys. Rev.

Search for the Higgs boson in events with missing transverse energy and b quark jets produced in proton-antiproton collisions at s**(1/2)=1.96 TeV

We search for the standard model Higgs boson produced in association with an electroweak vector boson in events with no identified charged leptons, large imbalance in transverse momentum, and two jets where at least one contains a secondary vertex consistent with the decay of b hadrons. We use ~1 fb-1 integrated luminosity of proton-antiproton collisions at s**(1/2)=1.96 TeV recorded by the CDF II experiment at the Tevatron. We find 268 (16) single (double) b-tagged candidate events, where 248 +/- 43 (14.4 +/- 2.7) are expected from standard model background processes. We place 95% confidence level upper limits on the Higgs boson production cross section for several Higgs boson masses ranging from 110 GeV/c2 to 140 GeV/c2. For a mass of 115 GeV/c2 the observed (expected) limit is 20.4 (14.2) times the standard model prediction.Comment: 8 pages, 2 figures, submitted to Phys. Rev. Let

Measurement of the Helicity Fractions of W Bosons from Top Quark Decays Using Fully Reconstructed top-antitop Events with CDF II

We present a measurement of the fractions F_0 and F_+ of longitudinally polarized and right-handed W bosons in top quark decays using data collected with the CDF II detector. The data set used in the analysis corresponds to an integrated luminosity of approximately 318 pb -1. We select ttbar candidate events with one lepton, at least four jets, and missing transverse energy. Our helicity measurement uses the decay angle theta*, which is defined as the angle between the momentum of the charged lepton in the W boson rest frame and the W momentum in the top quark rest frame. The cos(theta*) distribution in the data is determined by full kinematic reconstruction of the ttbar candidates. We find F_0 = 0.85 +0.15 -0.22 (stat) +- 0.06 (syst) and F_+ = 0.05 +0.11 -0.05 (stat) +- 0.03 (syst), which is consistent with the standard model prediction. We set an upper limit on the fraction of right-handed W bosons of F_+ < 0.26 at the 95% confidence level.Comment: 11 pages, 2 figures, submitted to Phys. Rev.

Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s) = 1.96 TeV

We present a measurement of the top quark pair production cross section in ppbar collisions at sqrt(s)=1.96 TeV using 318 pb^{-1} of data collected with the Collider Detector at Fermilab. We select ttbar decays into the final states e nu + jets and mu nu + jets, in which at least one b quark from the t-quark decays is identified using a secondary vertex-finding algorithm. Assuming a top quark mass of 178 GeV/c^2, we measure a cross section of 8.7 +-0.9 (stat) +1.1-0.9 (syst) pb. We also report the first observation of ttbar with significance greater than 5 sigma in the subsample in which both b quarks are identified, corresponding to a cross section of 10.1 +1.6-1.4(stat)+2.0-1.3 (syst) pb.Comment: Accepted for publication in Physics Review Letters, 7 page

Evidence for the exclusive decay Bc+- to J/psi pi+- and measurement of the mass of the Bc meson

We report first evidence for a fully reconstructed decay mode of the B_c^{\pm} meson in the channel B_c^{\pm} \to J/psi \pi^{\pm}, with J/psi \to mu^+mu^-. The analysis is based on an integrated luminosity of 360 pb$^{-1} in p\bar{p} collisions at 1.96 TeV center of mass energy collected by the Collider Detector at Fermilab. We observe 14.6 \pm 4.6 signal events with a background of 7.1 \pm 0.9 events, and a fit to the J/psi pi^{\pm} mass spectrum yields a B_c^{\pm} mass of 6285.7 \pm 5.3(stat) \pm 1.2(syst) MeV/c^2. The probability of a peak of this magnitude occurring by random fluctuation in the search region is estimated as 0.012%.Comment: 7 pages, 3 figures. Version 3, accepted by PR

Observation and Mass Measurement of the Baryon Ξb−\Xi^-_b

We report the observation and measurement of the mass of the bottom, strange baryon $\Xi^-_b$ through the decay chain $\Xi^-_b \to J/\psi \Xi^-$, where $J/\psi \to \mu^+ \mu^-$, $\Xi^- \to \Lambda \pi^-$, and $\Lambda \to p \pi^-$. Evidence for observation is based on a signal whose probability of arising from the estimated background is 6.6 x 10^{-15}, or 7.7 Gaussian standard deviations. The $\Xi^-_b$ mass is measured to be $5792.9\pm 2.5$ (stat.) $\pm 1.7$ (syst.) MeV/$c^2$.Comment: Minor text changes for the second version. Accepted by Phys. Rev. Let

Polarizations of J/psi and psi(2S) Mesons Produced in ppbar Collisions at 1.96 TeV

We have measured the polarizations of \jpsi and \psiprime mesons as functions of their transverse momentum \pt when they are produced promptly in the rapidity range $|y|<0.6$ with \pt \geq 5 \pgev. The analysis is performed using a data sample with an integrated luminosity of about 800 \ipb collected by the CDF II detector. For both vector mesons, we find that the polarizations become increasingly longitudinal as \pt increases from 5 to 30 \pgev. These results are compared to the predictions of nonrelativistic quantum chromodynamics and other contemporary models. The effective polarizations of \jpsi and \psiprime mesons from $B$-hadron decays are also reported.Comment: 8 pages, 7 figures, published in Physical Review Letter

Search for New Particles Leading to Z+jets Final States in ppˉp\bar{p} Collisions at s=1.96\sqrt{s}=1.96 TeV

We present the results of a search for new particles that lead to a \Z boson plus jets in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV using the Collider Detector at Fermilab (CDF II). A data sample with a luminosity of 1.06 \ifb\ collected using \Z boson decays to $ee$ and $\mu\mu$ is used. We describe a completely data-based method to predict the dominant background from standard-model \Z+jet events. This method can be similarly applied to other analyses requiring background predictions in multi-jet environments, as shown when validating the method by predicting the background from $W$+jets in \ttbar production. No significant excess above the background prediction is observed, and a limit is set using a fourth generation quark model to quantify the acceptance. Assuming $BR(b' \to b\Z) = 100$ and using a leading-order calculation of the $b'$ cross section, $b'$ quark masses below 268 \gev/c^2 are excluded at 95% confidence level.Comment: To be submitted to PR