Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session H13: Top Quark Properties I |
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Sponsoring Units: DPF Chair: Reinhard Schwienhorst, Michigan State University Room: Hyatt Regency Dallas Cumberland G |
Sunday, April 23, 2006 8:30AM - 8:42AM |
H13.00001: Search for Single Top Quark Production at D\O Liang Li Protons and antiprotons are collided in Run~II at the Fermilab Tevatron at a center of mass energy of 1.96~TeV. We present results of an improved search for single top quark production in these collisions using a dataset of approximately 360~pb$^{-1}$ collected with the D\O detector. This analysis considers both production modes, $s$-channel $tb$ and $t$-channel $tqb$, and makes use of secondary-vertex tagging to identify jets originating from $b$~quarks as well as neural networks to separate the expected signals from backgrounds. [Preview Abstract] |
Sunday, April 23, 2006 8:42AM - 8:54AM |
H13.00002: Searches for Single Top Production at CDF Jason Slaunwhite We present recent results from searches for single-top-quark production at CDF in p-pbar collisions at 1.96 TeV. Individual top quarks are expected to be produced in association with bottom quarks mainly through the exchange of an off-mass-shell W boson ($s$-channel), or the W- gluon fusion process ($t$-channel). We select events with one charged lepton, high missing transverse energy and at least 2 jets, one of which is identified as a b-quark using the CDF Silicon detector. It is a challenge to distinguish the single top signal from significant backgrounds from W+jets processes with heavy flavour, eg Wbb, Wcc, Wc. We perform a combined search for the $s$- and $t$- channels, along with individual searches for each channel. [Preview Abstract] |
Sunday, April 23, 2006 8:54AM - 9:06AM |
H13.00003: Search for Single Top Quarks Produced via Flavor-Changing Neutral-Current Couplings at D\O Supriya Jain The large mass of the top quark, close to the electroweak symmetry-breaking scale, makes it a good candidate for probing physics beyond the Standard Model, including possible anomalous couplings. One form these couplings can take is with flavor-changing neutral currents, which can give rise to a single top quark in the final state through gluon exchange, together with a $c$ or $u$ quark in the initial or final state. We search for single top quark production through both the $t$-$c$-$g$ and $t$-$u$-$g$ couplings, using the D\O\ detector at the Fermilab Tevatron collider, and present limits on the anomalous coupling parameters $\kappa_c/\Lambda$ and $\kappa_u/\Lambda$, where $\Lambda$ defines the scale of new physics and $\kappa_c$ ($\kappa_u$) defines the strength of the $t$-$c$-$g$ ($t$-$u$-$g$) couplings. [Preview Abstract] |
Sunday, April 23, 2006 9:06AM - 9:18AM |
H13.00004: A Search for Resonant $t\bar{t}$ Production at D\O Amnon Harel We report on a search for a massive particle that decays to $t\bar{t}$. The search is performed using $t\bar{t}$ candidates in the lepton+jets channel. A constrained kinematic fit, with top quark mass fixed, is used to evaluate the $t\bar{t}$ invariant mass for each candidate. We then search for deviations from the $t\bar{t}$ mass distribution predicted by QCD. [Preview Abstract] |
Sunday, April 23, 2006 9:18AM - 9:30AM |
H13.00005: Search for Dilepton Signatures Containing Tau Leptons in Top Events at CDF Stephane Tourneur We present a measurement of the branching ratio of the top quark decaying exclusively into third generation particles: into a b quark, a tau lepton and a tau neutrino. The analysis is performed on the data collected by CDF during the Tevatron run II. We use top pair events in which, each top decaying into Wb, one W produces an electron or a muon, and the other W gives a tau decaying into hadrons and a neutrino. The result constitutes a first test of the lepton universality in the realm of the top physics. [Preview Abstract] |
Sunday, April 23, 2006 9:30AM - 9:42AM |
H13.00006: First Measurement of $\sigma(gg\rightarrow t\bar{t})/\sigma(q\bar{q} \rightarrow t\bar{t})$ in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV Shabnaz Pashapour Following the discovery of the top quark, various studies have been dedicated to understanding the properties of this heavy particle. We will present the first measurement of the relative rate of $t\bar{t}$ production through gluon-gluon fusion in quark-antiquark annihilation, $\sigma(gg\rightarrow t\bar{t})/\sigma(q\bar{q} \rightarrow t\bar{t})$. This measurement uses about 0.7 fb$^{-1}$ of $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV collected by the Collider Detector at Fermilab (CDF). It provides a test of the QCD predictions for this pair-production mechanism, and a technique to test for unexpected sources of top quark production. The average number of gluons in the initial state of candidate $t\bar{t}$ events is measured using the low $p_T$ charged particle multiplicity, and the charged particle multiplicity is determined using W+n jet(s) and dijet data calibration samples, verified using Standard Model calculations. [Preview Abstract] |
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