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 Measurement of the Forward backward Asymmetry in Top antitop Quark Events in the Lepton jets Channel at D written by Douglas A. Orbaker and published by . This book was released on 2012 with total page 298 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 DØ 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 (9.2 ± 3.7)%, after background processes have been subtracted. After correcting for the effects of acceptance and detector reconstruction, we measure an asymmetry of (19.6 ± 6.5)%. In addition, we measure an acceptance-corrected asymmetry based on the lepton from top-antitop quark decay of (15.2 ± 4.0)%. We compare these results to predictions from the mc@nlo next-to-leading-order QCD simulation"--Leaf v.

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 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 Front Back Asymmetry in Top Antitop Quark Pairs Produced in Pp Collisions at s written by Thomas Andrew Schwarz and published by . This book was released on 2006 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 A Measurement of the Mass of the Top Quark in Lepton Jets Events at CDF written by Erik Matthews Brubaker and published by . This book was released on 2004 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The First Measurement of the Top Quark Mass at CDF II in the Lepton jets and Dilepton Channels Simultaneously written by and published by . This book was released on 2008 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present a measurement of the mass of the top quark using data corresponding to an integrated luminosity of 1.9 fb−1 of p{bar p} collisions collected at (square root)s = 1.96 TeV with the CDF II detector at Fermilab's Tevatron. This is the first measurement of the top quark mass using top-antitop pair candidate events in the lepton + jets and dilepton decay channels simultaneously. They reconstruct two observables in each channel and use a non-parametric kernel density estimation technique to derive two-dimensional probability density functions from simulated signal and background samples. The observables are the top quark mass and the invariant mass of two jets from the W decay in the lepton + jets channel, and the top quark mass and the scalar sum of transverse energy of the event in the diletpon channel. They perform a simultaneous fit for the top quark mass and the jet energy scale, which is constrained in situ by the hadronic W boson mass. using 332 lepton + jets candidate events and 144 diletpon candidate events, they measure the top quark mass to be m{sub top} = 171.9 ± 1.7 (stat. + JES) ± 1.1 (other sys.) GeV/c2 = 171.9 ± 2.0 GeV/c2.

Download or read book Measurement of the Forward backward Charge Asymmetry in Electron positron Annihilation Into a Quark antiquark Pair written by David Donald Stuart and published by . This book was released on 1992 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Measurement of the Left right Forward backward Asymmetry for Charm Quarks Using D sup and D Mesons written by and published by . This book was released on 1994 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Longitudinal polarization of the SLC e− beam allows a direct measurement of the left-right, forward-backward asymmetry of c-quarks to be made with the SLD. Events from Z° --> c{bar c} are tagged using fully and partially reconstructed decays of D{sup *+} mesons, and fully reconstructed decays of D mesons. The authors measure A{sub c} = 0.77 " 0.22(stat.) " 0.10(syst.).

Download or read book Measurement of Top Quark Polarization in Top antitop Lepton jets Final States at written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a measurement of the top quark polarization in the $t\overline{t}$ events produced in $p\overline{p}$ collisions at $\sqrt{s}=1.96$ TeV using data corresponding to 9.7 fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The final states used in the measurement contain one lepton and at least three jets. The polarization is measured using the angular distribution of leptons along three different axes: the beam axis, the helicity axis, and the transverse axis normal to the $t\overline{t}$ production plane. This is the first measurement of top quark polarization at the Tevatron Collider in lepton+jets final states, and the first measurement of transverse polarization in $t\overline{t}$ production. The polarization along the beam axis is combined with the previous result in the dilepton final states by the D0 experiment. The observed distributions are consistent with the Standard Model of nearly no polarization and no indication for beyond Standard Model physics is observed. The measurement offers legacy result from unique Tevatron Collider data and provides more information about the top quark production and decays, about the properties of the heaviest elementary particle.

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 Supersymmetry and the Unification of Fundamental Interactions written by Deog Ki Hong and published by AIP Conference Proceedings (Nu. This book was released on 2008-12-11 with total page 670 pages. Available in PDF, EPUB and Kindle. Book excerpt: This annual SUSY conference has become the world's largest international meeting devolted to new ideas in high energy physics. The main subject of the conference is theoretical and phenomenological aspects of supersymmetric theories, and dark matter and dark energy, and other comological connections. New, interesting results from various experimental groups are increasingly presented at the conference as well. With roughly 200 plenary and parallel presentations, SUSY08 will likely deliver energy and enthusiasm of both theorists and experimentalists who are searching the frontier of high energy physics.

Download or read book Precision Measurement of the Top Quark Mass in the Lepton Jets Channel Using a Matrix Element Method with Quasi Monte Carlo Integration written by and published by . This book was released on 2009 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a measurement of the top quark mass obtained from p{bar p} collisions at √s = 1.96 TeV at the Fermilab Tevatron using the CDF II detector. The measurement uses a matrix element integration method to calculate a t{bar t} likelihood, employing a Quasi-Monte Carlo integration, which enables us to take into account effects due to finite detector angular resolution and quark mass effects. We calculate a t{bar t} likelihood as a 2-D function of the top pole mass m{sub t} and [Delta]{sub JES}, where [Delta]{sub JES} parameterizes the uncertainty in our knowledge of the jet energy scale; it is a shift applied to all jet energies in units of the jet-dependent systematic error. By introducing [Delta]{sub JES} into the likelihood, we can use the information contained in W boson decays to constrain [Delta]{sub JES} and reduce error due to this uncertainty. We use a neural network discriminant to identify events likely to be background, and apply a cut on the peak value of individual event likelihoods to reduce the effect of badly reconstructed events. This measurement uses a total of 4.3 fb−1 of integrated luminosity, requiring events with a lepton, large E{sub T}, and exactly four high-energy jets in the pseudorapidity range.

Download or read book Direct Top Quark Decay Width Measurement in the Tt Lepton Jets Channel at s written by Philipp Stolte-Cord to Krax and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark t plays an essential role in the field of elementary particle physics - in particular due to its exceptional properties comprising a large mass, which approximately equals the mass of a tungsten atom, and an enormously short lifetime. This thesis is devoted to the study of a fundamental property of the top quark - its decay width. Its value is predicted by the established Standard Model of particle physics and deviations may hint at yet unknown physics beyond this model. A direct measurement of the decay width of the top quark is presented. The analysis is based on tt events i...

Download or read book Measurement of the Front Back Asymmetry in Top antitop Quark Pairs Produced in Proton antiproton Collisions at Center of Mass Energy written by Thomas A. Schwarz and published by . This book was released on 2006 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Izmerenie Massy Top kvarka V Neme enych Sobytijach Tipa lepton Strui Na CDF written by and published by . This book was released on 2005 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: