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Heavy flavor physics at the Tevatron

Description: We report on the status of top and b quark physics at the Fermilab Teva-tron collider. In particular, we summarize the knowledge obtained by CDF and D 6 O on the top quark mass and production cross-section. We also present some new interesting results obtained by CDF with the discovery of the Bc meson and a first low statistic measurement of sin(2{beta}) at an hadronic col-lider.
Date: November 1, 1998
Creator: Apollinari, G.
Partner: UNT Libraries Government Documents Department

Naturalness and Higgs Decays in the MSSM with a Singlet

Description: The simplest extension of the supersymmetric standard model--the addition of one singlet superfield--can have a profound impact on the Higgs and its decays. We perform a general operator analysis of this scenario, focusing on the phenomenologically distinct scenarios that can arise, and not restricting the scope to the narrow framework of the NMSSM. We reexamine decays to four b quarks and four {tau}'s, finding that they are still generally viable, but at the edge of LEP limits. We find a broad set of Higgs decay modes, some new, including those with four gluon final states, as well as more general six and eight parton final states. We find the phenomenology of these scenarios is dramatically impacted by operators typically ignored, specifically those arising from D-terms in the hidden sector, and those arising from weak-scale colored fields. In addition to sensitivity of m{sub z}, there are potential tunings of other aspects of the spectrum. In spite of this, these models can be very natural, with light stops and a Higgs as light as 82 GeV. These scenarios motivate further analyses of LEP data as well as studies of the detection capabilities of future colliders to the new decay channels presented.
Date: November 21, 2005
Creator: Chang, Spencer; Fox, Patrick J. & Weiner, Neal
Partner: UNT Libraries Government Documents Department

b {r_arrow} sl{sup +}l{sup {minus}} in the left-right symmetric model

Description: We begin to analyze and contrast the predictions for the decay b {r_arrow} sl{sup +}l{sup {minus}} in the Left-Right Symmetric Model (LMR) with those of the Standard Model (SM). In particular, we show that the forward-backward asymmetry of the lepton spectrum can be used to distinguish the SM from the simplest manifestation of the LRM.
Date: May 1, 1997
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

The discovery of the b quark at Fermilab in 1977: The experiment coordinator`s story

Description: I present the history of the discovery of the Upsilon ({Upsilon}) particle (the first member of the b-quark family to be observed) at Fermilab in 1977 by the CFS (Columbia-Fermilab-Stony Brook collaboration) E288 experiment headed by Leon Lederman. We found the first evidence of the {Upsilon} in November 1976 in an early phase of E288. The subsequent discovery in the spring of 1977 resulted from an upgraded E288 the {mu}{mu}II phase, optimized for dimuons, with about 100 times the sensitivity of the previous investigatory dimuon phase (which had been optimized for dielectrons). The events leading to the discovery, the planning of {mu}{mu}II and the running, including a misadventure (the infamous Shunt Fire of May 1977), are described. Some discussions of the aftermath, a summary, and an acknowledgement list end this brief historical note.
Date: December 1, 1997
Creator: Yoh, J.
Partner: UNT Libraries Government Documents Department

Recent Tevatron results on b quark production

Description: A number of recent B physics results from the CDF and D0 experiments at the Fermilab Tevatron Collider is reported. Measurements of open b quark production cross section in the central and forward rapidity regions in p{anti p} interactions at {radical}s = 1800 GeV are presented. The measurements are used to evaluate the rapidity dependence of b quark production. We also report recent results on correlated b {anti b} production: a measurement of b {anti b} angular correlations using dimuon triggers (D0) and the first direct measurement of b {anti b} rapidity correlations (CDF). The results from the various measurements are compared with the next-to-leading order QCD predictions. Finally, a measurement by CDF of the polarization of {psi}(2S) mesons is compared with the predictions of the Color Octet Model.
Date: June 1, 1999
Creator: Baarmand, Marc M.
Partner: UNT Libraries Government Documents Department

Properties of b-quark production at the Tevatron

Description: We report on results obtained by the D0 and CDF collaborations on the properties of b-quark production in p{anti p} collisions at ps = 1:8 TeV. The D0 experiment has measured the inclusive production cross section for muons originating from b-quark decays in the forward region, corresponding to the rapidity range 2:4 < j y {sup {mu}} j < 3:2. Combined with previous measurements in the central region, these results permit a comparison of the rapidity dependence of the b-quark production cross section with the predictions of next-to-leading order QCD. The CDF experiment has achieved the #12;rst direct measurement of b {anti b} rapidity correlations at a hadron collider, with the ratio of the cross sections obtained in two rapidity bins. This measurement is a direct probe of the high-x gluon content of the proton.
Date: October 1, 1998
Creator: Stichelbaut, Frederic
Partner: UNT Libraries Government Documents Department

A Measurement of the Top Quark Mass in 1.96 TeV Proton-Antiproton Collisions Using a Novel Matrix Element Method

Description: A measurement of the top quark mass in t{bar t} {yields} l + jets candidate events, obtained from p{bar p} collisions at {radical}s = 1.96 TeV at the Fermilab Tevatron using the CDF II detector, is presented. The measurement approach is that of a matrix element method. For each candidate event, a two dimensional likelihood is calculated in the top pole mass and a constant scale factor, 'JES', where JES multiplies the input particle jet momenta and is designed to account for the systematic uncertainty of the jet momentum reconstruction. As with all matrix element techniques, the method involves an integration using the Standard Model matrix element for t{bar t} production and decay. However, the technique presented is unique in that the matrix element is modified to compensate for kinematic assumptions which are made to reduce computation time. Background events are dealt with through use of an event observable which distinguishes signal from background, as well as through a cut on the value of an event's maximum likelihood. Results are based on a 955 pb{sup -1} data sample, using events with a high-p{sub T} lepton and exactly four high-energy jets, at least one of which is tagged as coming from a b quark; 149 events pass all the selection requirements. They find M{sub meas} = 169.8 {+-} 2.3(stat.) {+-} 1.4(syst.) GeV/c{sup 2}.
Date: September 30, 2007
Creator: CDF Collaboration
Partner: UNT Libraries Government Documents Department

Measurement of Branching Fractions and CP-Violating Asymmetries in B0 to K0K0bar and B+ to K0barK+ Decays at the BaBar Experiment

Description: Over the last few years, the B factories have established the Cabbibo-Kobayashi-Maskawa mechanism of CP violation in the Standard Model through the study of the decays of B mesons. The focus of Belle and BaBar has now expanded to the search for signatures of new physics beyond the Standard Model, particularly through examination of flavor-changing neutral-current transitions, which proceed through diagrams involving virtual loops. These decays are suppressed in the Standard Model, increasing sensitivity to new-physics effects but decreasing branching fractions. Exploiting large and growing datasets, BaBar and Belle have made many measurements in loop decays where a b quark transitions to an s quark, observing hints of possible deviations from Standard Model expectations in CP-violating measurements.
Date: July 10, 2007
Creator: Biesiada, Jedrzej & U., /Princeton
Partner: UNT Libraries Government Documents Department

Measurement of B(d) mixing using opposite-side flavor tagging

Description: We report on a measurement of the B{sub d}{sup 0} mixing frequency and the calibration of an opposite-side flavor tagger in the D0 experiment. Various properties associated with the b quark on the opposite side of the reconstructed B meson are combined using a likelihood-ratio method into a single variable with enhanced tagging power. Its performance is tested with data, using a large sample of reconstructed semileptonic B {yields} {mu}D{sup 0} X and B {yields} {mu}D* X decays, corresponding to an integrated luminosity of approximately 1 fb{sup -1}. The events are divided into groups depending on the value of the combined tagging variable, and an independent analysis is performed in each group. Combining the results of these analyses, the overall effective tagging power is found to be {var_epsilon}{prime}D{sup 2} = (2.48 {+-} 0.21{sub -0.06}{sup +0.08})%. The measured B{sub d}{sup 0} mixing frequency {Delta}m{sub d} = 0.506 {+-} 0.020 (stat) {+-} 0.016 (syst) ps{sup -1} is in good agreement with the world average value.
Date: September 1, 2006
Creator: Abazov, V. M.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adams, M.; Adams, T. et al.
Partner: UNT Libraries Government Documents Department

Z{sup 0} pole direct measurements of the parity violation parameters A{sub b} and A{sub c} at SLD

Description: This report presents three different techniques used at SLD to measure directly the parity violation parameters of Zb{bar b} and Zc{bar c} couplings from the left-right forward-backward asymmetries. The results have been obtained using 150,000 hadronic Z{sup 0} decays accumulated during the 1993-95 runs with high electron beam polarization.
Date: September 1, 1996
Creator: Mancinelli, G.
Partner: UNT Libraries Government Documents Department

B physics in Run II with upgraded CDF II

Description: At the beginning of next millennium B-factories at KEK or PEP collider will be operating and will provide precise measurements of CP violation parameters in the B{sup 0} systems. In order to test the Standardd Model predictions, measurements of parameters which involve B{sub s}, B{sub u} and {Lambda}{sub b} decays will be necessary. We present here how the upgraded CDF detector will be suited for these studies.
Date: October 1, 1998
Creator: Lucchesi, Donatella
Partner: UNT Libraries Government Documents Department

A measurement of the b quark fragmentation function at {radical}Q{sup 2} = 45.6 GeV

Description: Presented here is a measurement of the b quark fragmentation function D{sub b}(X), taken from a sample of 504 semi-leptonic B decays which were selected from the 150,000 Z{sup 0} decays collected between 1993 and 1995 at the SLD at SLAC. The energy of each tagged B hadron is reconstructed using missing jet energy, based on the information from the lepton and a partially-reconstructed charm-decay vertex. Account is taken of the effect of primary orbitally excited mesons (B**s). An iterative unfolding procedure is used which serves to effectively extract the true fragmentation function from the reconstructed B energy spectrum. The final result is shown to be compatible with many theoretical models. A comparison is made with other b fragmentation function measurements at 45.6 GeV, and this measurement is shown to be consistent with those results. The average scaled energy is found to be (x{sub E}) = 0.697{+-} 0.017(stat) {+-} 0.034(sys).
Date: June 1, 1996
Creator: Church, E.D.
Partner: UNT Libraries Government Documents Department

Calculating fermion masses in superstring derived standard-like models

Description: One of the intriguing achievements of the superstring derived standard-like models in the free fermionic formulation is the possible explanation of the top quark mass hierarchy and the successful prediction of the top quark mass. An important property of the superstring derived standard-like models, which enhances their predictive power, is the existence of three and only three generations in the massless spectrum. Up to some motivated assumptions with regard to the light Higgs spectrum, it is then possible to calculate the fermion masses in terms of string tree level amplitudes and some VEVs that parameterize the string vacuum. I discuss the calculation of the heavy generation masses in the superstring derived standard-like models. The top quark Yukawa coupling is obtained from a cubic level mass term while the bottom quark and tau lepton mass terms are obtained from nonrenormalizable terms. The calculation of the heavy fermion Yukawa couplings is outlined in detail in a specific toy model. The dependence of the effective bottom quark and tau lepton Yukawa couplings on the flat directions at the string scale is examined. The gauge and Yukawa couplings are extrapolated from the string unification scale to low energies. Agreement with {alpha}{sub strong}, sin{sup 2} {theta}{sub W} and {alpha}{sub em} at M{sub Z} is imposed, which necessitates the existence of intermediate matter thresholds. The needed intermediate matter thresholds exist in the specific toy model. The effect of the intermediate matter thresholds on the extrapolated Yukawa couplings is studied. It is observed that the intermediate matter thresholds help to maintain the correct b/{tau} mass relation. It is found that for a large portion of the parameter space, the LEP precision data for {alpha}{sub strong}, sin{sup 2} {theta}{sub W} and {alpha}{sub em}, as well as the top quark mass and the b/{tau} mass relation can all simultaneously ...
Date: April 1, 1996
Creator: Faraggi, A.E.
Partner: UNT Libraries Government Documents Department

Status of BTeV: A dedicated b physics experiment at the Fermilab Tevatron Collider

Description: BTeV is a program whose long term goal is to carry out precision studies of CP violation, mixing, and raare decays of bottom and charmed quarks in the forward direction at the Fermilab Tevatron Collider. It is planned for the new interaction region, C0, currently being constructed. We describe the technique, physics reach, and status of BTeV.
Date: October 1, 1998
Creator: Butler, Joel N.
Partner: UNT Libraries Government Documents Department

Search for ZX {yields} {nu}{anti {nu}} b {anti b} Events in the D-Zero Detector

Description: We report on a search for a new particle, X, decaying via X {yields} b{anti b}, made through associated production with a Z boson. We use data collected with the D0 detector operating at the Fermilab Tevatron p{anti p} collider with {radical}s = 1.8 TeV. We utilize muon-tagged jets to identify b-quarks and the {nu}{anti {nu}} channel to detect Z bosons. Preliminary results on cross section limits for X masses between 90 GeV/c{sup 2} and 180 GeV/c{sup 2} are presented.
Date: October 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Determination of the b-quark production cross section in p{anti p} collisions at 630 GeV

Description: We present a preliminary measurement of the b-quark production cross section in p{anti p} collisions at {radical}s = 630 GeV. The analysis is based on 340 nb{sup -1} of data collected with the D0 detector at the Fermilab Tevatron Collider. We determine the ratio of the b-quark production cross sections at 630 GeV to 1800 GeV and compare our results with the CDF and UA1 measurements, and with the next-to- leading order QCD predictions.
Date: October 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Can we distinguish an MSSM higgs from a SM higgs at a linear collider?

Description: The authors study the prospects for distinguishing the CP-even Higgs boson of the minimal supersymmetric extension of the Standard Model (MSSM) from the Standard Model (SM) Higgs boson by measuring its branching ratios at an e{sup +}e{sup {minus}} linear collider. The regions of the M{sub A} - tan {beta} plane in which an MSSM Higgs boson can be distinguished from the SM Higgs boson depend strongly upon the supersymmetric parameters that enter the radiative corrections to the Higgs mass matrix and the Higgs couplings to fermions. In some regions of parameter space it is possible to extract the supersymmetric correction to the relation between the b quark mass and its Yukawa coupling from Higgs branching ratio measurements.
Date: January 4, 2001
Creator: Logan, H.E.
Partner: UNT Libraries Government Documents Department

Advances in the determination of quark masses

Description: Significant progress has been made in the determination of the light quark masses, using both lattice QCD and sum rule methods, in the last year. The authors discuss the different methods and review the status of current results. Finally, they review the calculation of bottom and charm masses.
Date: March 1, 1998
Creator: Bhattacharya, T. & Gupta, R.
Partner: UNT Libraries Government Documents Department

B-physics results from D-Zero

Description: A number of B-physics results from the D0 experiment at the Fermilab Tevatron Collider is reported. Measurements of b{anti b} production in p{anti p} interactions at {radical}s = 1800 GeV and 630 GeV are used to evaluate, for the first time with the same detector, the center-of-mass energy and rapidity dependence of b-quark production cross section. A measurement of the b{anti b} angular correlations using dimuon triggers is also presented. Preliminary results from these measurements are compared with the next-to-leading order QCD predictions. Finally, dimuon data samples are used to study P{sub T} and rapidity dependence of b-produced and direct charmonium production.
Date: January 1, 1998
Creator: Baarmand, M.M.
Partner: UNT Libraries Government Documents Department

Onium and b production at the Tevatron

Description: Recent data from the CDF and D0 experiments at the Tevatron are presented on b quark production cross sections, J/{psi}, {psi}{prime} and {Upsilon} production cross sections. An analysis from CDF of the production polarization of the J/{psi}, {psi}{prime} and {Upsilon}(1S) is reviewed and the results discussed in the context of the color octet model.
Date: January 27, 2000
Creator: Sumorok, K.
Partner: UNT Libraries Government Documents Department

Observation of Z decays to b quark pairs at the Tevatron Collider

Description: A search for Z boson decays to pairs of b-quark jets has been performed in the full dataset collected with the CDF detector at the Tevatron p{anti p} collider. After the selection of a pure sample of b {anti b} events by means of the identification of secondary vertices from b-quark decays, we have used two kinematic variables to further discriminate the electroweak b {anti b} production from QCD processes, and sought evidence for the Z decay in the dijet invariant mass distribution. An absolute background prediction allows the extraction of an excess of events inconsistent with the background predictions by 3.23{sigma} but in good agreement with the amount and characteristics of the expected signal. We then fit the mass distribution with an unbinned likelihood technique, and obtain a Z {yields} b {anti b} signal amounting to 91 {+-} 30 {+-} 19 events.
Date: July 1, 1998
Creator: Dorigo, T.
Partner: UNT Libraries Government Documents Department