Download or read book Forward Backward Asymmetry in Top Quark Production in Ppbar Collisions at Sqrt s written by and published by . This book was released on 2008 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Measurement of the Forward backward Asymmetry in Top Quark antiquark Production in Ppbar Collisions Using the Lepton jets Channel written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measurement of the Forward Backward Asymmetry in Low Mass Bottom Quark Pairs Produced in Proton Antiproton Collisions written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We report a measurement of the forward-backward asymmetry, $A_{FB}$, in $b\bar{b}$ pairs produced in proton-antiproton collisions and identified by muons from semileptonic $b$-hadron decays. The event sample was collected at a center-of-mass energy of $\sqrt{s}=1.96$ TeV with the CDF II detector and corresponds to 6.9 fb$^{-1}$ of integrated luminosity. We obtain an integrated asymmetry of $A_{FB}(b\bar{b})=(1.2 \pm 0.7)$\% at the particle level for $b$-quark pairs with invariant mass, $m_{b\bar{b}}$, down to $40$ GeV/$c^2$ and measure the dependence of $A_{FB}(b\bar{b})$ on $m_{b\bar{b}}$. The results are compatible with expectations from the standard model.

Download or read book Forward backward Asymmetry in Top Quark antiquark Production written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Search for Same sign Top quark Pair Production at Sqrt s written by and published by . This book was released on 2011 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: An inclusive search for same-sign top-quark pair production in pp collisions at sqrt(s) = 7 TeV is performed using a data sample recorded with the CMS detector in 2010, corresponding to an integrated luminosity of 35 inverse picobarns. This analysis is motivated by recent studies of p p-bar to t t-bar reporting mass-dependent forward-backward asymmetries larger than expected from the standard model. These asymmetries could be due to Flavor Changing Neutral Currents (FCNC) in the top sector induced by t-channel exchange of a massive neutral vector boson (Z'). Models with such a Z' also predict enhancement of same-sign top-pair production in pp or p p-bar collisions. Limits are set as a function of the Z' mass and its couplings to u and t quarks. These limits disfavour the FCNC interpretation of the Tevatron results.

Download or read book Measurement of the Top Quark Forward backward Production Asymmetry and the Anomalous Chromoelectric and Chromomagnetic Moments in Pp Collisions at s written by Albert M. Sirunyan and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Forward Backward Asymmetry at High Mass in t bar t Production in p bar p Collisions at sqrt s written by and published by . This book was released on 2011 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: Current understanding of particle physics postulates that there are 17 fundamental particles that interact via four fundamental forces - gravity, the strong force, the weak force, and the electromagnetic force. These fundamental particles can be classified by their spins into bosons, which are the force-carrying particles with integer spins, and fermions, which have half-integer spins. Fermions can be further divided into quarks and leptons. The particles and three of the four forces - all but gravity - are described by the Standard Model, a local SU(3) x SU(2) x U(1) gauge theory. Electromagnetic and weak interactions as described by Electroweak Theory or Quantum Electrodynamics, SU(2) x U(1). Strong interactions are described by Quantum Chromodynamics or QCD, SU(3). Fermions are grouped into three generations as shown in Table 1.1. Each generation consists of a leptonic doublet containing a charged and a neutral lepton and a weak isospin doublet containing two quarks. The first generation, containing the electron, the electron neutrino, the up quark, and the down quark, is the lightest generation and is thus the most frequently found in nature. The second generation contains the muon, the muon neutrino, the strange quark, and the charm quark. The third generation contains the tau, the tau neutrino, the bottom quark, and the top quark.

Download or read book Measurement of the Charge Asymmetry in Top Quark Pair Production in Pp Collisions at sqrt s written by and published by . This book was released on 2015 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: The charge asymmetry in the production of top quark and antiquark pairs is measured in proton-proton collisions at a center-of-mass energy of 8 TeV. The data, corresponding to an integrated luminosity of 19.6 fb -1 were collected by the CMS experiment at the LHC. Events with a single isolated electron or muon, and four or more jets, at least one of which is likely to have originated from hadronization of a bottom quark, are selected. A template technique is used to measure the asymmetry in the distribution of differences in the top quark and antiquark absolute rapidities. The measured asymmetry is Ayc= [0.33_0.26 (stat)_0.33 (syst)]%, which is the most precise result to date. The results are compared to calculations based on the standard model and on several beyond-the-standard-model scenarios.

Download or read book Evidence for a Mass Dependent Forward Backward Asymmetry in Top Quark Pair Production written by and published by . This book was released on 2011 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Forward Backward Asymmetry of Top Quark Pair Productionn at the Fermilab Tevatron written by and published by . This book was released on 2015 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Measurement of the Forward Backward Asymmetry in Top Antitop Quark Events in the Lepton Jets Channel at written by and published by . This book was released on 2012 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of forward-backward asymmetries in top-antitop quark pairs produced in proton-antiproton collisions decaying via the lepton+jets channel. Using data recorded by the D0 experiment at the Fermilab Tevatron collider and corresponding to an integrated luminosity of 5.4 fb-1, we measure the forward-backward asymmetry in top-antitop quark events to be $\left(9.2 \pm 3.7\right)\%$, after background processes have been subtracted. After correcting for the effects of acceptance and detector reconstruction, we measure an asymmetry of $\left(19.6 \pm 6.5\right)\%$. In addition, we measure an acceptance-corrected asymmetry based on the lepton from top-antitop quark decay of $\left(15.2 \pm 4.0\right)\%$. We compare these results to predictions from the MC@NLO next-to-leading-order QCD simulation.

Download or read book Forward Backward Asymmetries in Top Antitop Quark Production at the Tevatron written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Measurement of the Forward backward Asymmetry in b0 and bar u039B b0 Baryon Production in p bar p Collisions at sqrt s written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We measure the forward-backward asymmetry in the production of ?0b and ?¯0b baryons as a function of rapidity in pp¯ collisions at √s = 1.96 TeV using 10.4 fb-1 of data collected with the D0 detector at the Fermilab Tevatron collider. The asymmetry is determined by the preference of ?0b or ?¯0b particles to be produced in the direction of the beam protons or antiprotons, respectively. As a result, the measured asymmetry integrated over rapidity y in the range 0.1

Download or read book Forward Backward Asymmetry in Lambda b Production and Search for the Xi b and Omega b Baryons in p bar p Collisions at sqrt s written by and published by . This book was released on 2015 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a search for the heavy-flavor baryons $\Xi_{b}$ (bsd) and $\Omega^{-}_{b}$ in decays $\Xi^{-}_{b}$→ J/[psi]$\Xi^{-}_{b}$ → J/[psi][Lambda][pi]-, J/[psi] → [mu]+ [mu]- and $\Omega^{-}_{b}$ → J/[psi]$\Omega^{-}_{b}$ J/[psi][Lambda] $K^{-}_{b}$, J/[psi] → [mu]+ [mu]- respectively.

Download or read book Measurement of the Charge Asymmetry in Top quark Pair Production in Proton proton Collisions at Sqrt s written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The difference in angular distributions between top quarks and antiquarks, commonly referred to as the charge asymmetry, is measured in pp collisions at the LHC with the CMS experiment. The data sample corresponds to an integrated luminosity of 1.09 fb−1 at a centre-of-mass energy of 7 TeV. Top-quark pairs are selected in the final state with an electron or muon and four or more jets. At least one jet is identified as originating from b-quark hadronization. The charge asymmetry is measured in two variables, one based on the pseudorapidities ([eta]) of the top quarks and the other on their rapidities (y). The results A{sub C}{sup {eta}} = -0.017 ± 0.032(stat.){sub -0.036}{sup +0.025}(syst.) and A{sub C}{sup y} = -0.013 ± 0.028(stat.){sub -0.031}{sup +0.029}(syst.) are consistent within uncertainties with the standard-model predictions.

Download or read book Measurement of the Forward backward Asymmetry in Lambda b0 and bar Lambda b 0 Baryon Production in p bar p Collisions at sqrt s written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Top Quark Pair Production Cross Section and Forward Backward Asymmetry at the Tevatron written by and published by . This book was released on 2008 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.