Charge of the Top Quark

Andy Beretvas, J. Antos, Y.C. Chen and T. Maki

For the CDF Collaboration

There is a question about the identity of the top quark. Is it the top quark of the SM with electric charge 2/3 or is it an exotic quark with charge -4/3? An exotic charge has been preposed by D. Chang et al.[ D. Chang, W.-F. Chang, and E. Ma, Phys. Rev. D59, 091503 (1999)]. The analysis will use the standard CDF run II dilepton sample. The key ingredients of this analysis, are the correct pairing of the lepton and b-jet, the determination of the charge of the b-jet, and the reduction of the background. The analysis proceeds by using a binomial distribution and is formulated so that rejecting one hypothesis means support for the other hypothesis.

Measurement of the Lifetime Difference in the Bs System

Avdhesh Chandra

For the DO Collaboration

We present a study of the untagged decay of $B_s^0 \rightarrow J/\psi \phi$, the final state of which is a superposition of the CP-even and CP-odd states. Within the framework of the standard model (SM), to a good approximation, the two CP eigenstates of the ($B_s^0$, ${\overline{B}_s^0}$) system are equivalent to mass eigenstates. From a simultaneous fit to the distributions in the candidate mass, proper decay length, and three angles represents angular distribution of the decay products, we obtain the average lifetime of the ($B_s^0$, ${\overline{B}_s^0}$) system, $\overline \tau (B_s^0)$ =1.53 $\pm$0.08 (stat)$^{+0.01}_{-0.04}$ (syst) ps, and the width difference between the light and heavy mass eigenstates, $\Delta \Gamma \equiv (\Gamma_L - \Gamma_H)$ = 0.15 $\pm$ 0.10 (stat) $^{+0.03}_{-0.04}$ (syst) ps$^{-1}$. These measurements are consistent with SM predictions within the measurement uncertainties. The data sample corresponds to an integrated luminosity of 0.8 fb$^{-1}$ accumulated with the D\O\ detector at the Tevatron. All results are preliminary.

GEANT4 Validation with the CMS HCAL test beam data

Jordan Damgov, Stefan Piperov

A study of the CMS hadron calorimeter has been perform using pions, protons, electrons, and muons in the H2 test beam in the North Area at CERN in 2004. This note presents the some measured properties of the HCAL barrel calorimeter. They include the detector energy resolution, linearity, and longitudinal shower profile as a function of the incident particle momentum. The detector configuration that was used included a mock-up of electromagnetic calorimeter (ECAL) and two hadronic barrel modules (HB1 & 2). The momentum range of the beam particles was from 5 to 300 GeV/c. A validation of the GEANT4 physics lists, LHEP-3.7 and QGSP-2.8, was done by comparing the predictions of the simulation with the test beam data.

Search for Exotic and Excited Muons at CDF

Heather Gerberich

For the CDF Collaboration

We present a search for the production of excited or exotic muons (mu*) via the reaction pbar + p -> mu* + mu -> mu gamma + mu using 371/pb of data collected with the Run 2 CDF detector. In this signature-based search, we look for a resonance in the mu-gamma mass spectrum. The data are compared to Standard Model and detector background expectations, and with predictions of excited muon production. We use these comparisons to set limits on the mu* mass and compositeness scale in the Contact Interaction and Gauge-Mediated models.

Studying ttH with H to bb in the top dilepton channel

Christopher Hill, Joseph Incandela, Sue Ann Koay

Amongst (perhaps unofficial) mandates for the LHC, locating the Higgs particle is surely a feature in many physicists' dreams. However, since Nature -- or at least the Standard Model -- seems to have tucked the so-called "god particle" in a difficult mass range (roughly 114 to 207 GeV/c^2 via electroweak fit), prospective Higgs hunters are advised to pack mega-doses of ingenuity and perseverance. In this study, we investigate discovery prospects in the CMS experiment, when the Higgs is produced in conjunction with two top quarks both of which undergo leptonic decays: t -> bW with W -> lepton + neutrino.

Electroweak Production of Top Quarks in RunII at DO

Shabnam Jabeen

Boston University

For the D0 Collaboration

Electroweak production of the top quark (single top) has yet to be observed. The single top cross section is sensitive to new physics and to the CKM matrix parameter Vtb. The DO experiment at the Tevatron has been collecting data at sqrt{s}= 1.96 TeV in pbar-p collisions since the start of Run II. Results of an improved search for single top quark production, using a dataset of approximately 360/pb are presented. This analysis makes use of secondary-vertex tagging to identify jets originating from b-quarks and discriminating techniques to separate the expected signal from backgrounds.

Bayesian Learning of Neural Networks for Signal/Background Discrimination in Particle Physics

Michael Pogwizd*, Laura Jane Elgass*, Pushpalatha C. Bhat**

* College of DuPage, Glen Ellyn, IL and Northern Illinois University, DeKalb, IL

** Fermilab, Batavia, IL and Northern Illinois University, DeKalb, IL

Neural networks are used extensively in classification problems in particle physics research. Since the training of neural networks can be viewed as a problem of inference, Bayesian learning of neural networks can provide more optimal and robust results than conventional learning methods. We have investigated the use of Bayesian neural networks for signal/background discrimination in the search for second generation leptoquarks at the Tevatron, as an example. We present a comparison of the results obtained from the conventional training of feedforward neural networks and networks trained with Bayesian methods.

W and Z bosons production at sqrt(s)=1.96TeV with the D0 detector

Alexei Popov

IHEP(Protvino)

For the D0 Collaboration

The D0 Forward Proton Detector

Murilo Rangel

For the D0 Collaboration

Quantum Chromo-Dynamics (QCD) has been a very successful model describing the strong interaction, but its success has been limited primarily to the perturbative regime. About 40% of the total proton-antiproton cross section at the Tevatron consists of the non-perturbative processes of elastic and diffractive scattering. These processes are better described by the phenomenology of a color singlet exchange of a particle with quantum numbers of the vacuum called the pomeron (Regge theory). The D0 experiment is currently taking data with a forward proton detector (FPD) to better study this process. The FPD data is being used to study the diffractive phenomenology, which has attracted both experimental and theoretical attention. This data provides a unique opportunity to study many topics in the diffractive regime, for instance events which contain a double pomeron exchange. This talk will present FPD data acquired during the last year, focusing on the methods for eliminating background and noise and emphasizing the detector capabilities to explore this interesting physics regime.

CDF Measurement of the W Boson Mass

Ian Vollrath, Chris Hays, William Trischuk, Oliver Stelzer-Chilton, Larry Nodulman, and Ashutosh Kotwal

We describe an analysis of the W boson mass using a sample of W to e nu and W to mu nu candidates collected in sqrt(s)=1.96 TeV proton anti-proton collisions produced by the Fermilab Tevatron and measured by the CDF II detector. The achieved precision is greater than any other hadron collider W mass measurement, including the CDF combined Run 1 measurement.

Extra Dimensions at CDF

Sara-madge Wynne

For the CDF Collaboration

We present an overview of searches for ADD, RS and 1/TeV extra dimensions at sqrt(s)=1.96 TeV at the Tevatron, using the CDF detector, with integrated luminosities of 300 to 800 /pb. These searches, carried out in the diphoton and dilepton channels, set limits using the signatures of both graviton emission and exchange.

Search for a Standard Model Higgs Boson in CMS via Vector Boson Fusion in the H->WW->lnln Channel

Efe Yazgan, Jordan Damgov

A study of the potential to discover the Standard Model Higgs boson in the vector-boson fusion channel is presented. The decay of Higgs bosons into the W+W- final state is considered, with both W-bosons decaying leptonically. The main background is ttbar with one or more jets produced. The study is based on a full simulation of the CMS detector, and up-to-date reconstruction codes. The conclusion is that a signal of at least 5 sigma significance can be obtained with an integrated luminosity of about 60 inverse femtobarns for Higgs bosons with 130 < m(H) < 200 GeV.