276 Matching Results

Search Results

open access

Higgs Boson Production in Association With Bottom Quarks

In the Standard Model, the coupling of the Higgs boson to b quarks is weak, leading to small cross sections for producing a Higgs boson in association with b quarks. However, Higgs bosons with enhanced couplings to b quarks, such as occur in supersymmetric models for large values of tan {beta}, will be copiously produced at both the Tevatron and the LHC in association with b quarks which will be an important discovery channel. We investigate the connections between the production channels, bg {… more

Date: May 26, 2003

Creator: Dawson, S.; Campbell, J.; Dittmaier, S.; Jackson, C.; Kramer, M. & Maltoni, F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Neutral Supersymmetric Higgs Boson Searches

In some Supersymmetric extensions of the Standard Model, including the Minimal Supersymmetric Standard Model (MSSM), the coupling of Higgs bosons to b-quarks is enhanced. This enhancement makes the associated production of the Higgs with b-quarks an interesting search channel for the Higgs and Supersymmetry at D0. The identification of b-quarks, both online and offline, is essential to this search effort. This thesis describes the author's involvement in the development of both types of b-taggi… more

Date: September 1, 2009

Creator: Robinson, Stephen Luke

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

The left-right forward-backward asymmetry for B quarks at the SLD

The left-right asymmetry for b quarks, A{sub b}, is precisely predicted by the Weinberg-Salam-Glashow model of particle interactions, now the standard model for high-energy particle physics. As a test of this model, A{sub b} is directly measured at the SLC Large Detector (SLD) by taking advantage of the unique polarized electron beam at the Stanford Linear Collider (SLC) and measuring the left-right forward-backward asymmetry of b quarks. To measure the asymmetry, b quarks are identified using … more

Date: May 1, 1994

Creator: Williams, D. C.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

CDF searches for new phenomena

We present results of recent searches for new physics using the CDF detector at the Fermilab Tevatron. Presented are searches for Higgs {yields} {gamma}{gamma}, as well as more general searches in {gamma}{gamma} + X where X is /E{sub T}, jets, charged leptons, b-quarks or extra photons. The CDF ee{gamma}{gamma}/E{sub T} candidate event is discussed along with estimates of the expected rates in the Standard Model. Other searches for SUSY, Higgs and Technicolor look for particles which decay to v… more

Date: June 1, 1998

Creator: Toback, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

B-Tagging at CDF and D0, lessons for LHC

The identification of jets resulting from the fragmentation and hadronization of b quarks is an important part of high-p{sub T} collider physics. The methods used by the CDF and D0 collaborations to perform this identification are described, including the calibration of the efficiencies and fake rates. Some thoughts on the application of these methods in the LHC environment are also presented.

Date: May 1, 2006

Creator: Wright, Thomas

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Triggering on B-jets at CDF II

In this paper we present a trigger algorithm able to select online events enriched of b-jets. This feature is of central interest in order to extend the physics reach for standard model and minimal super symmetric model Higgs decaying into a pair of b-quarks. The algorithm fully exploits the recently upgraded CDFII tracking system and Level 2 CALorimeter cluster finder. These upgrades are necessary to cope with Tevatron increasing luminosity and provide new and refined trigger primitives that a… more

Date: January 1, 2009

Creator: Amerio, Silvia; Casarsa, Massimo; Cortiana, Giorgio; Donini, Julien; Lucchesi, Donatella & Pagan Griso, Simone

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Study of t anti-t production in tau jets channel at CDFII using neural networks

CDF (Collider Detector at Fermilab) is a particle detector located at Fermi National Laboratories, near Chicago. it allows to study decay products of p{bar p} collisions at center-of-mass energy of 1.96 TeV. During its first period of data taking (RunI), CDF observed for the first time the top quark (1995). The current period of data taking (RunII) is devoted to precise measurements of top properties and to search for new physics. This thesis work is about the top decay channel named {tau} + je… more

Date: December 1, 2005

Creator: Amerio, Silvia

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

Search for neutral Higgs bosons decaying to tau pairs produced in association with b-quarks at s**(1/2)=1.96 TeV

We report results from a search for neutral Higgs bosons decaying to tau pairs produced in association with a b-quark in 1.6 fb{sup -1} of data taken from June 2006 to March 2008 with the D0 detector at Fermi National Accelerator Laboratory. The final state includes a muon, hadronically decaying tau, and jet identified as coming from a b-quark. We set cross section times branching ratio limits on production of such neutral Higgs bosons {phi} in the mass range from 90 GeV to 160 GeV. Exclusion l… more

Date: December 1, 2008

Creator: Herner, Kenneth Richard

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

Recent measurements of the average lifetime of hadrons containing B-quarks from PEP experiments at SLAC (Stanford Linear Accelerator Center)

Recent precise results from several experiments have confirmed the early evidence that the lifetime of hadrons containing B-quarks is rather long, implying that the third generation of quarks is more decoupled from the first two than the second is from the first. The average of the measurements performed by the experiments at PEP is 1.08 +- 0.13 ps.

Date: May 1, 1987

Creator: Camporesi, T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Search for neutral Higgs bosons decaying to tau pairs in association with b-quarks at the D0 Detector

We report results from a search for neutral Higgs bosons decaying to tau pairs produced in association with a b-quark in 1.2 fb{sup -1} of data taken from June 2006 to August 2007 with the D0 detector at Fermi National Accelerator Laboratory. The final state includes a muon, hadronically decaying tau and jet identified as coming from a b-quark. We set cross section times branching ratio limits on production of such neutral Higgs bosons {phi} in the mass range from 90 GeV/c{sup 2} to 160 GeV/c{s… more

Date: June 1, 2009

Creator: Herner, Kenneth

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Precision Measurement of the Mass of the Top Quark in p anti-p Collisions

We report a measurement of the mass of the top quark (m{sub top}) in p{bar p} collisions at a center of mass energy of 1.96 TeV. The analysis is based on p{bar p}{yields}t{bar t}{yields} lepton+jets data recorded with the D0 detector at the Fermilab Tevatron Collider. Events were preselected in the e+jets (913 events/pb of data) and in the {mu}+jets (871 events/pb of data) channels. These were analyzed through a comparison of the matrix element for the production and decay of the t{bar t} state… more

Date: January 1, 2007

Creator: Garcia, Carlos A.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

Measurement of the polarized forward-backward asymmetry of B quarks using momentum-weighted track charge at SLD

This thesis presents a direct measurement of the parity-violating parameter A{sub b} by analyzing the polarized forward-backward asymmetry of b quarks in e{sup +}e{sup {minus}} {yields} Z{sup 0} {yields} b{bar b}. Data were taken at the Stanford Linear Accelerator Center (SLAC), with the Stanford Large Detector (SLD), which records the products of e{sup +}e{sup {minus}} interactions at a center of mass energy {radical}s = 91.2 GeV/c{sup 2} at the SLAC Linear Collider (SLC). The SLC/SLD experime… more

Date: November 1, 1995

Creator: Junk, T.R.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

Measurement of the inclusive bb jet cross section at the Collidor Detector at Fermilab

Data collected by the Fermilab CDF detector are used to measure the inclusive b{bar b} jet production cross section in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. Vertices displaced from the primary interaction point (secondary vertices) are a signature for long-lived decay and are used to identify jets originating from b quarks. An event sample containing two jets, each having an identified secondary vertex, is used. The jets are required to be within the pseudo-rapidi… more

Date: September 1, 2005

Creator: Gajjar, Anant

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

Study of sequential semileptonic decays of b hadrons produced at the Tevatron

The authors present a study of rates and kinematical properties of lepton pairs contained in central jets with transverse energy E{sub T} {ge} 15 GeV that re produced at the Fermilab Tevatron collider. They compare the data to a QCD prediction based on the HERWIG and QQ Monte Carlo generator programs. They find that the data are poorly described by the simulation, in which sequential semileptonic decays of single b quarks (b {yields} l c X with c {yields} l s X) are the major source of such lep… more

Date: July 1, 2005

Creator: Apollinari, G.; Fiori, I.; Giromini, P.; Happacher, F.; Miscetti, S.; Parri, A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Photo- and hadro-production of charm and beauty at Fermilab

This report concentrates on results from three Fermilab experiments: the photoproduction of charm in the fixed target mode from experiment E687, and the collider hadroproduction of b-quarks and B-mesons as measured respectively by the D0 and CDF detectors. Only the production of open flavors is considered. For heavy quarkonia results see the contribution from B. Naroska to these proceedings.

Date: September 1, 1995

Creator: Maciel, A. K. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The CDF silicon vertex tracker

Real time pattern recognition is becoming a key issue in many position sensitive detector applications. The CDF collaboration is building SVT: a specialized electronic device designed to perform real time track reconstruction using the silicon vertex detector (SVX II). This will strongly improve the CDF capability of triggering on events containing b quarks, usually characterized by the presence of a secondary vertex. SVT is designed to reconstruct in real time charged particles trajectories us… more

Date: October 10, 2000

Creator: al., A. Cerri et

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

L3 physics at the Z resonance and a search for the Higgs particle

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory. Electroweak interactions were studied using the L3 Detector on the Large Electron-Positron Collider (LEP) at the European Center for Nuclear Study (CERN). The specific physics studied utilized the Silicon Microvertex Detector (SMD) of L3, which Los Alamos had previously played a major role in proposing, designing, constructing, and commissioning. This dete… more

Date: July 1, 1997

Creator: Coan, T.A.; Kinnison, W.W.; Kapustinsky, J. & Shukla, J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The magnitude of the gluon condensate and the masses of c and b quarks from the families of T/{Psi} and {Upsilon} mesons

It is shown that the model used by Shifman, Vainshtein, and Zakharov for the description of the experimental function R{sub c}(s) in the form of a sum of {delta}-functions and the plateau contradicts the Wilson operator expansion (O.E.) in the terms due to the gluon condensate. A QCD model with an infinite number of vector mesons does satisfy the requirements of the O.E. for masses and electronic width resonances close to the experimental values. The region of allowable values of the masses of … more

Date: November 1, 1993

Creator: Geshkenbein, B. & Morgunov, V.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Angular correlations in beauty production at the Tevatron at sqrt(s) = 1.96 TeV

Measurements of the b quark production cross section at the Tevatron and at Hera in the final decades of the 20th century have consistently yielded higher values than predicted by Next-to-Leading Order (NLO) QCD. This discrepancy has led to a large efforts by theorists to improve theoretical calculations of the cross sections and simulations of b quark production. As a result, the difference between theory and experiment has been much reduced. New measurements are needed to test the development… more

Date: June 1, 2005

Creator: Wijngaarden, Daniel A. & Nijmegen, /Radboud U.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

Resonance--Continuum Interference in Light Higgs Boson Production at a Photon Collider

We study the effect of interference between the Standard Model Higgs boson resonance and the continuum background in the process {gamma}{gamma} {yields} H {yields} b{bar b} at a photon collider. Taking into account virtual gluon exchange between the final-state quarks, we calculate the leading corrections to the height of the resonance for the case of a light (m{sub H} < 160 GeV) Higgs boson. We find that the interference is destructive and around 0.1-0.2% of the peak height, depending on th… more

Date: January 6, 2009

Creator: Dixon, Lance J.; Sofianatos, Yorgos & /SLAC /Stanford U., Phys. Dept.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Naturalness and Higgs Decays in the MSSM with a Singlet

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… more

Date: November 21, 2005

Creator: Chang, Spencer; Fox, Patrick J. & Weiner, Neal

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

D0 Higgs physics results

We have searched for the Standard Model (SM) and non Standard Model Higgs bosons using of about 200-260 pb{sup -1} of data collected with the upgraded Run II D0 detector at Fermilab Tevatron. Low-mass SM Higgs boson is searched in the associated production with W or Z and limits are placed on the cross section and the kinematic properties of the W or Z plus heavy flavor production. SM Higgs boson with mass greater than 135 GeV is searched for in its dominant decay mode WW with W's decaying into… more

Date: June 1, 2005

Creator: Rani, K. Jyothsna & Inst., /Tata

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Search for Scalar Bottom Quarks from Gluino Decays in Proton - Anti-proton Collisions at a Center-of-Mass Energy of 1.96-TeV

The authors have performed a search for the scalar bottom quark ({tilde b}{sub 1}) from gluino ({tilde g}) decays in an R-parity conserving SUSY scenario with m{sub {tilde g}} > m{sub {tilde b}{sub 1}}, by investigating a final state of large missing transverse energy, with three or more jets, and some of them from the hadronization of b-quarks. A data sample of 156 pb{sup -1} collected by the Collider Detector at Fermilab at a center-of-mass energy of {radical}s = 1.96 TeV was used. For the… more

Date: December 1, 2004

Creator: Rott, Carsten

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

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

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.

Item Type: Article

Partner: UNT Libraries Government Documents Department