Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session X9: B Physics III |
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Sponsoring Units: DPF Chair: Bob Cahn, Lawrence Berkeley National Laboratory Room: Governor's Square 11 |
Tuesday, May 5, 2009 1:30PM - 1:42PM |
X9.00001: Study of $\overline{B^0}, B^- \to D^{(\ast)} p\bar{p}\ n\pi$, $n=0,1,2$ decays Tae Min Hong Using a data sample of about $414 \textrm{fb}^{-1}$ collected with the {\it B{\footnotesize A}B{\footnotesize AR}} detector at the $\Upsilon(4S)$ resonance, consisting of $455 \times 10^6$ $B\bar{B}$ pairs, we measure the branching fractions for ten Cabibbo-favored $B$ decays to final states of the form $\overline{B^0}, B^- \to D^{(\ast)} p\bar{p}\ n\pi$, $n=0,1,2$ and study their decay dynamics. [Preview Abstract] |
Tuesday, May 5, 2009 1:42PM - 1:54PM |
X9.00002: Polarization of $\Upsilon$~Mesons Produced in $p\bar p$~Collisions at $\sqrt{s} = 1.96$~TeV James Thome We measure the polarization of $\Upsilon$~mesons in the $\Upsilon(1S)$, $\Upsilon(2S)$ and $\Upsilon(3S)$ states as a function of their transverse momentum $p_T$ in the $s$-channel helicity frame. The analysis uses $\Upsilon$~mesons produced in the rapidity range $|y|<0.6$. The measurement is performed using a data sample of $p\bar{p}$ collisions at $\sqrt{s} = 1.96$~TeV with an integrated luminosity of $>3$~fb$^{-1}$ collected with the CDF\,II detector at the Fermilab Tevatron. The results are compared to theoretical predictions. [Preview Abstract] |
Tuesday, May 5, 2009 1:54PM - 2:06PM |
X9.00003: Strategies for btagging calibration using data at CMS Pratima Jindal A reliable estimate of the performance of $b$-jet Identification algorithms is crucial for a wide range of physics processes like the decay of top quarks, Higgs boson searches, and various supersymmetric processes. CMS has prepared several strategies to extract efficiencies and rejection rates from data, which should work even on the first data (10 $pb^{-1}$). Three methods are being presented here. The first extracts rejection rates from light quarks looking at tracks with negative impact parameter, and using these distributions to model the mistag rate due to detector effects like resolutions and badly reconstructed tracks.The second method uses jet samples with reconstructed muons; by tagging a $b$-jet and selection based on the $p_T$ of the muon relative to the jet, a system of equations can be constructed which leads to the direct extraction of efficiencies and rejections. The third method uses $t \bar{t}$ events with semi leptonic or fully leptonic W decays, and uses likelihood-based and event counting based methods to estimate the efficiencies. The strategies described here are studied taking into account the possible startup scenarios of LHC, and are currently being expanded to take into account the miscalibration scenarios which CMS can show at the startup. [Preview Abstract] |
Tuesday, May 5, 2009 2:06PM - 2:18PM |
X9.00004: ABSTRACT WITHDRAWN |
Tuesday, May 5, 2009 2:18PM - 2:30PM |
X9.00005: Observation of Resonances in the $\Lambda_b^0\rightarrow\Lambda_c^+\pi^+\pi^-\pi^-$ Decay Mode at CDF\,II Patrizia Barria In a sample of events, collected with a displaced secondary vertex trigger at the CDF\,II experiment and corresponding to about 2.4~fb$^{-1}$ of integrated luminosity, the decay $\Lambda_b^0\rightarrow\Lambda_c^+\pi^+\pi^-\pi^-$ is observed. In addition, the $\Lambda_c^+\pi^+\pi^-\pi^-$ final state is studied and clear signals of the following exclusive decay channels are observed: $\Lambda_b^0 \rightarrow{\Lambda_c^{*+}}(2593,2625)[\Lambda_c^+\pi^+\pi^-]\pi^-$, $\Lambda_b^0 \rightarrow{\Sigma_c^{++}}[\Lambda_c^+\pi^+]\pi^-\pi^-$, $\Lambda_b^0 \rightarrow{\Sigma_c^{0}}[\Lambda_c^+\pi^-]\pi^+\pi^-$, and $\Lambda_b^0 \rightarrow \Lambda_c^+\rho^0\pi^-$. The observation of such exclusive decay modes will allow for additional interesting measurements in the $\Lambda_b^0$ sector. [Preview Abstract] |
Tuesday, May 5, 2009 2:30PM - 2:42PM |
X9.00006: A Model Independent Measurement of the Branching Fraction of $\Upsilon(4S)$ Decays to Neutral $B$ Pairs Romulus Godang, Lucien Cremaldi, Don Summers Isospin violation in $\Upsilon(4S) \to B\bar{B}$ decays induces a difference in the branching fractions $f_{00} = {\cal B} (\Upsilon(4S) \to B^0 \bar{B}^{0})$, and $f_{+-} = {\cal B} (\Upsilon(4S) \to B^+B^-)$. These branching fractions are important inputs for many $B$ meson measurements at $B$ factories. Isospin violation in the $\Upsilon (4S)$ resonance decays may be at the level of a few percent mostly due to electromagnetic interactions and the mass difference between the up and the down quarks. We discuss a model independent measurement of the $f_{00}$ branching fraction based on a data sample of $\sim$470 million $B \bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the {\sl B{\scriptsize A}B{\scriptsize AR}} detector. We reconstruct neutral $B$ meson in the channel $\bar {B}^0 \to D^{*+} \ell^{-} \bar{\nu}_{\ell}$ using a partial reconstruction technique. [Preview Abstract] |
Tuesday, May 5, 2009 2:42PM - 2:54PM |
X9.00007: Search for the transition $\chi_{b0}\rightarrow \Upsilon(1S) \gamma$ Peter Lewis, Rafe Schindler We present the results of a search for the transition $\chi_{b0}\rightarrow \Upsilon(1S) \gamma$ in the exclusive reconstruction $\Upsilon(2S)\rightarrow \chi_{b0} \gamma$; $\chi_{b0} \rightarrow \Upsilon(1S) \gamma$; $\Upsilon(1S)\rightarrow \mu\mu$. Our results use 14~pb$^{-1}$ of data collected at the $\Upsilon(2S)$ resonance with the {\it B{\footnotesize A}B {\footnotesize AR}} detector at the PEP-II $e^+e^-$ storage rings. [Preview Abstract] |
Tuesday, May 5, 2009 2:54PM - 3:06PM |
X9.00008: Study of the $\Sigma_b$ Baryon with the CDF Detector Constantino Calancha We present a measurement of properties of the $\Sigma_b$ baryon in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. Using 2.9 fb$^{-1}$ of data collected with the CDF\,II detector, we observe four $\Lambda_b\,\pi$ resonances in the fully reconstructed decay mode $\Lambda_b \rightarrow J/\psi\Lambda$ with $J/\psi \rightarrow \mu^+\mu^-$ and $\Lambda \rightarrow p\pi$. In addition, we combine the selected $\Lambda_b$ signal from $\Lambda_b \rightarrow J/\psi\Lambda$ with events from the $\Lambda_b \rightarrow \Lambda_c\pi$ decay mode, with $\Lambda_c\rightarrow pK\pi$, to measure the $\Lambda_b$ polarization. [Preview Abstract] |
Tuesday, May 5, 2009 3:06PM - 3:18PM |
X9.00009: Study of $B \to \pi \ell \nu$ and $B \to \rho \ell \nu$ Decays and Determination of $|V_{ub}|$ H. Wells Wulsin We present an analysis of exclusive charmless semileptonic B- meson decays based on 343 million $B\bar{B}$ pairs recorded with the {\it B{\footnotesize A}B{\footnotesize AR}} detector at the $\Upsilon(4S)$ resonance. We measure branching fractions ${\cal B}(B \to \pi \ell \nu)$ and ${\cal B}(B \to \rho \ell \nu)$. We compare the measured distribution in $q^2$, the momentum- transfer squared, with theoretical predictions for the form factors from lattice QCD, light-cone sum rules, and quark model calculations. We also extract the CKM matrix element $|V_{ub}|$ from the measurement of $B \to \pi \ell \nu$ decays. [Preview Abstract] |
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