Forward-Backward Asymmetry of Top Quark Pair Productionn at the Fermilab Tevatron

Forward-Backward Asymmetry of Top Quark Pair Productionn at the Fermilab Tevatron
Author :
Publisher :
Total Pages : 297
Release :
ISBN-10 : OCLC:951619247
ISBN-13 :
Rating : 4/5 (47 Downloads)

Synopsis Forward-Backward Asymmetry of Top Quark Pair Productionn at the Fermilab Tevatron by :

This dissertation presents the final measurements of the forward-backward asymmetry (AFB) of top quark-antiquark pair events (t t- ) at the Collider Detector at Fermilab (CDF) experiment. The t t- events are produced in proton{anti-proton collisions with a center of mass energy of 1:96 TeV during the Run II of the Fermilab Tevatron. The measurements are performed with the full CDF Run II data (9.1 fb-1) in the final state that contain two charged leptons (electrons or muons, the dilepton final state), and are designed to con rm or deny the evidence-level excess in the AFB measurements in the final state with a single lepton and hadronic jets (lepton+jets final state) as well as the excess in the preliminary measurements in the dilepton final state with the first half of the CDF Run II data. New measurements include the leptonic AFB (AlFB), the lepton-pair AFB (All FB) and the reconstructed top AFB (At t FB). Each are combined with the previous results from the lepton+jets final state measured at the CDF experiment. The inclusive Al FB, All FB, and At t FB measured in the dilepton final state are 0.072 ± 0.060, 0.076 ± 0.081, and 0.12 ± 0.13, to be compared with the Standard Model (SM) predictions of 0.038 ± 0.003, 0.048 ± 0.004, and 0.010 ± 0.006, respectively. The CDF combination of AlFB and At t FB are 0.090+0:028 -0.026, and 0.160 ± 0.045, respectively. The overall results are consistent with the SM predictions.

Top Quark Pair Production Cross Section and Forward-Backward Asymmetry at the Tevatron

Top Quark Pair Production Cross Section and Forward-Backward Asymmetry at the Tevatron
Author :
Publisher :
Total Pages : 4
Release :
ISBN-10 : OCLC:727355918
ISBN-13 :
Rating : 4/5 (18 Downloads)

Synopsis Top Quark Pair Production Cross Section and Forward-Backward Asymmetry at the Tevatron by :

We present recent results on top quark pair production cross section and forward-backward asymmetry at the Tevatron. Three new cross section measurements from CDF and one new measurement from DO are presented that utilize the full dataset available. A new DO top cross section combination gives a ttbar production cross section of sigma ttbar = 7.83 + 0.46-0.45 (stat) + 0.64-0.53 (syst) +-0.48 (lumi). The new CDF cross section combination for ttbar production is found to be 7.0 +- 0.3 (stat) +- 0.4 (syst) +- 0.4 (lumi) pb giving a total uncertainty of 9%, very close to the that of the current best theoretical predictions. It is important to measure the top cross section in as many different channels as possible and investigate their compatibility. This is useful as new physics might show up differently in the different channels. Thus any significant discrepancy could be a sign of new physics. Three new measurements of the forward-backward asymmetry are also presented. The two CDF measurements unfold the observed asymmetry back to parton level in order to directly compare the values obtained with theoretical predictions. The DO measurement is not unfolded and therefore does not depend on the specific method used for unfolding.

Evidence for a Mass Dependent Forward-Backward Asymmetry in Top Quark Pair Production

Evidence for a Mass Dependent Forward-Backward Asymmetry in Top Quark Pair Production
Author :
Publisher :
Total Pages : 23
Release :
ISBN-10 : OCLC:873634996
ISBN-13 :
Rating : 4/5 (96 Downloads)

Synopsis Evidence for a Mass Dependent Forward-Backward Asymmetry in Top Quark Pair Production by :

We present a new measurement of the inclusive forward-backward t{bar t} production asymmetry and its rapidity and mass dependence. The measurements are performed with data corresponding to an integrated luminosity of 5.3 fb−1 of p{bar p} collisions at √s = 1.96 TeV, recorded with the CDF II Detector at the Fermilab Tevatron. Significant inclusive asymmetries are observed in both the laboratory frame and the t{bar t} rest frame, and in both cases are found to be consistent with CP conservation under interchange of t and {bar t}. In the t{bar t} rest frame, the asymmetry is observed to increase with the t{bar t} rapidity difference, [Delta]y, and with the invariant mass M{sub t{bar t}} of the t{bar t} system. Fully corrected parton-level asymmetries are derived in two regions of each variable, and the asymmetry is found to be most significant at large [Delta]y and M{sub t{bar t}}. For M{sub t{bar t}} ≥ 450 GeV/c2, the parton-level asymmetry in the t{bar t} rest frame is A{sup t{bar t}} = 0.475 ± 0.114 compared to a next-to-leading order QCD prediction of 0.088 ± 0.013.

Forward-backward Asymmetry in Top Quark-antiquark Production

Forward-backward Asymmetry in Top Quark-antiquark Production
Author :
Publisher :
Total Pages :
Release :
ISBN-10 : OCLC:873808918
ISBN-13 :
Rating : 4/5 (18 Downloads)

Synopsis Forward-backward Asymmetry in Top Quark-antiquark Production by :

We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a dataset corresponding to an integrated luminosity of 5.4 fb−1, collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t{bar t} forward-backward asymmetry to be (9.2 ± 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 ± 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 ± 4.0)%. The results are compared to predictions based on the next-to-leading-order QCD generator mc@nlo. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.

Forward-Backward Asymmetries in Top-Antitop Quark Production at the Tevatron

Forward-Backward Asymmetries in Top-Antitop Quark Production at the Tevatron
Author :
Publisher :
Total Pages :
Release :
ISBN-10 : OCLC:986210125
ISBN-13 :
Rating : 4/5 (25 Downloads)

Synopsis Forward-Backward Asymmetries in Top-Antitop Quark Production at the Tevatron by :

We present the combined results on inclusive forward-backward asymmetries in the production of top-antitop quark pairs and their decay leptons. The analysis is based on measurements by the CDF and D0 experiments at the Fermilab $p\bar{p}$ Tevatron collider using all the data collected at $\sqrt{s}$ = 1:96 TeV. The measured asymmetries are in agreement with standard model predictions.

Forward-Backward Asymmetry in Top Quark Production in Ppbar Collisions at Sqrt{s}

Forward-Backward Asymmetry in Top Quark Production in Ppbar Collisions at Sqrt{s}
Author :
Publisher :
Total Pages : 8
Release :
ISBN-10 : OCLC:727212335
ISBN-13 :
Rating : 4/5 (35 Downloads)

Synopsis Forward-Backward Asymmetry in Top Quark Production in Ppbar Collisions at Sqrt{s} by :

Reconstructable final state kinematics and charge assignment in the reaction p{bar p} --> t{bar t} allows tests of discrete strong interaction symmetries at high energy. We define frame dependent forward-backward asymmetries for the outgoing top quark in both the p{bar p} and t{bar t} rest frames, correct for experimental distortions, and derive values at the parton-level. Using 1.9 fb−1 of p{bar p} collisions at (square root)s = 1.96 TeV recorded with the CDF II detector at the Fermilab Tevatron, we measure forward-backward top quark production asymmetries in the p{bar p} and t{bar t} rest frames of A{sub FB}{sup p{bar p}} = 0.17 ± 0.08 and A{sub FB}{sup t{bar t}} = 0.24 ± 0.14.

Recent Results of Top Quark Physics from the Tevatron

Recent Results of Top Quark Physics from the Tevatron
Author :
Publisher :
Total Pages : 4
Release :
ISBN-10 : OCLC:940484872
ISBN-13 :
Rating : 4/5 (72 Downloads)

Synopsis Recent Results of Top Quark Physics from the Tevatron by :

Twenty years after its discovery in 1995 by the CDF and D0 collaborations at the Tevatron proton-antiproton collider at Fermilab, the top quark still undergoes intensive studies at the Tevatron and the LHC at CERN. In this article, recent top quark physics results from CDF and D0 are reported. In particular, measurements of single top quark and double top quark production, the $t\bar{t}$ forward-backward asymmetry and the top quark mass are discussed.

Measurement of the Front Back Asymmetry in Top-antitop Quark Pairs Produced in Proton-antiproton Collisions at Center of Mass Energy

Measurement of the Front Back Asymmetry in Top-antitop Quark Pairs Produced in Proton-antiproton Collisions at Center of Mass Energy
Author :
Publisher :
Total Pages : 110
Release :
ISBN-10 : OCLC:316302323
ISBN-13 :
Rating : 4/5 (23 Downloads)

Synopsis Measurement of the Front Back Asymmetry in Top-antitop Quark Pairs Produced in Proton-antiproton Collisions at Center of Mass Energy by : Thomas A. Schwarz

Quarks, along with leptons and force carrying particles, are predicted by the Standard Model to be the fundamental constituents of nature. In distinction from the leptons, the quarks interact strongly through the chromodynamic force and are bound together within the hadrons. The familiar proton and neutron are bound states of the light ''up'' and ''down'' quarks. The most massive quark by far, the ''top'' quark, was discovered by the CDF and D0 experiments in March, 1995. The new quark was observed in p{bar p} collisions at 1.8 TeV at the Fermilab Tevatron. The mass of the top quark was measured to be 176 {+-} 13 GeV/c{sup 2} and the cross section 6.8{sub -2.4}{sup +3.6} pb. It is the Q = 2/3, T{sub 3} = +1/2 member of the third generation weak-isospin doublet along with the bottom quark. The top quark is the final Standard Model quark to be discovered. Along with whatever is responsible for electroweak symmetry breaking, top quark physics is considered one of the least understood sectors of the Standard Model and represents a front line of our understanding of particle physics. Currently, the only direct measurements of top quark properties come from the CDF and D0 experiments observing p{bar p} collisions at the Tevatron. Top quark production at the Tevatron is almost exclusively by quark-antiquark annihilation, q{bar q} {yields} t{bar t} (85%), and gluon fusion, gg {yields} t{bar t} (15%), mediated by the strong force. The theoretical cross-section for this process is {sigma}{sub t{bar t}} = 6.7 {+-} 0.8 pb for m{sub t} = 175 GeV/c{sup 2}. Top quarks can also be produced at the Tevatron via q{bar b}{prime} {yields} tb and qg {yields} q{prime}tb through the weak interaction. The cross section for these processes is lower (3pb) and the signal is much more difficult to isolate as backgrounds are much higher. The top quark is predicted to decay almost exclusively into a W-boson and a bottom quark (t {yields} Wb). The total decay width t {yields} Wb is {Lambda} = 1.50 GeV. This corresponds to an incredibly short lifetime of 0.5 x 10{sup -24} seconds. This happens so quickly that hadronization and bound states do not take place, which leads to the interesting consequence that the top quark spin information is passed to the decay products.

Top Quark Physics at Hadron Colliders

Top Quark Physics at Hadron Colliders
Author :
Publisher : Springer Science & Business Media
Total Pages : 166
Release :
ISBN-10 : 9783540710608
ISBN-13 : 3540710604
Rating : 4/5 (08 Downloads)

Synopsis Top Quark Physics at Hadron Colliders by : Arnulf Quadt

This will be a required acquisition text for academic libraries. More than ten years after its discovery, still relatively little is known about the top quark, the heaviest known elementary particle. This extensive survey summarizes and reviews top-quark physics based on the precision measurements at the Fermilab Tevatron Collider, as well as examining in detail the sensitivity of these experiments to new physics. Finally, the author provides an overview of top quark physics at the Large Hadron Collider.

Physics at the Terascale

Physics at the Terascale
Author :
Publisher : John Wiley & Sons
Total Pages : 437
Release :
ISBN-10 : 9783527634972
ISBN-13 : 3527634975
Rating : 4/5 (72 Downloads)

Synopsis Physics at the Terascale by : Ian Brock

Written by authors working at the forefront of research, this accessible treatment presents the current status of the field of collider-based particle physics at the highest energies available, as well as recent results and experimental techniques. It is clearly divided into three sections; The first covers the physics -- discussing the various aspects of the Standard Model as well as its extensions, explaining important experimental results and highlighting the expectations from the Large Hadron Collider (LHC). The second is dedicated to the involved technologies and detector concepts, and the third covers the important - but often neglected - topics of the organisation and financing of high-energy physics research. A useful resource for students and researchers from high-energy physics.