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Measurement Of The T T Bar Production Cross Section In Pp Collisions At 7 Tev In Lepton Jets Events Using B Quark Jet Identification
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Book Synopsis Measurement of the T T-bar Production Cross Section in Pp Collisions at 7 TeV in Lepton + Jets Events Using B-quark Jet Identification by :
Download or read book Measurement of the T T-bar Production Cross Section in Pp Collisions at 7 TeV in Lepton + Jets Events Using B-quark Jet Identification written by and published by . This book was released on 2011 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new measurement of the inclusive production cross section for pp to t t-bar is performed at a center-of-mass energy of 7 TeV using data collected by the CMS experiment at the LHC. The analysis uses a data sample corresponding to an integrated luminosity of 36 inverse picobarns, and is based on the final state with one isolated, high transverse momentum muon or electron, missing transverse energy, and hadronic jets. The ttbar content of the selected events is enhanced by requiring the presence of at least one jet consistent with b-quark hadronization. The measured cross section is 150 +/- 9 (stat.) +/- 17 syst.) +/- 6 (lumi.) pb and is in agreement with higher-order QCD calculations. The combination of this measurement with a previous CMS result based on dileptons gives 154 +/- 17 (stat.+syst.) +/- 6 (lumi.) pb.
Author :Anna Christine Henrichs Publisher :Springer Science & Business Media ISBN 13 :3319014870 Total Pages :231 pages Book Rating :4.3/5 (19 download)
Book Synopsis Top Quark Pair Production by : Anna Christine Henrichs
Download or read book Top Quark Pair Production written by Anna Christine Henrichs and published by Springer Science & Business Media. This book was released on 2013-10-04 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt: Before any kind of new physics discovery could be made at the LHC, a precise understanding and measurement of the Standard Model of particle physics' processes was necessary. The book provides an introduction to top quark production in the context of the Standard Model and presents two such precise measurements of the production of top quark pairs in proton-proton collisions at a center-of-mass energy of 7 TeV that were observed with the ATLAS Experiment at the LHC. The presented measurements focus on events with one charged lepton, missing transverse energy and jets. Using novel and advanced analysis techniques as well as a good understanding of the detector, they constitute the most precise measurements of the quantity at that time.
Book Synopsis Measurements of the T-tbar Production Cross Section in Lepton+jets Final States in Pp Collisions at 8 TeV and Ratio of 8 to 7 TeV Cross Sections by :
Download or read book Measurements of the T-tbar Production Cross Section in Lepton+jets Final States in Pp Collisions at 8 TeV and Ratio of 8 to 7 TeV Cross Sections written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A measurement of the top quark pair production (t-tbar) cross section in proton-proton collisions at the centre-of-mass energy of 8 TeV is presented using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.6 inverse-femtobarns. This analysis is performed in the t-tbar decay channels with one isolated, high transverse momentum electron or muon and at least four jets, at least one of which is required to be identified as originating from hadronization of a b quark. The calibration of the jet energy scale and the efficiency of b jet identification are determined from data. The measured t-tbar cross section is 228.5 +/- 3.8 (stat) +/- 13.7 (syst) +/- 6.0 (lumi) pb. This measurement is compared with an analysis of 7 TeV data, corresponding to an integrated luminosity of 5.0 inverse-femtobarns, to determine the ratio of 8 TeV to 7 TeV cross sections, which is found to be 1.43 +/- 0.04 (stat) +/- 0.07 (syst) +/- 0.05 (lumi). The measurements are in agreement with QCD predictions up to next-to-next-to-leading order.
Book Synopsis Measurement of the Ttbar Production Cross Section in Ppbar Collisions at S**ư by :
Download or read book Measurement of the Ttbar Production Cross Section in Ppbar Collisions at S**ư written by and published by . This book was released on 2005 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the measurement of the top quark pair production cross section in p{bar p} collisions at √s = 1.96 TeV using 318 pb−1 of data collected by the CDF detector at the Fermilab Tevatron. We measure the cross section in events with one high transverse momentum electron or muon, large missing transverse energy and three or more jets, where at least one bottom quarks from the top quark decay is identified via a secondary vertex tagging algorithm. The measured t{bar t} cross section is 8.7{sub -0.9}{sup +0.9}(stat){sub -0.9}{sup +1.2}(syst) pb, assuming a top quark mass of 178 GeV. The cross section measurement in the subsample in which both b-quark jets are identified gives 10.1{sub -1.4}{sup +1.6}(stat){sub -1.4}{sup +2.1}(syst) pb. We present one additional measurement of the t{bar t} cross section in the same dataset but without the b-tagging requirement. Top quark events are distinguished from the primary background of W boson production with associated jets using an artificial neural network method with a variety of kinematic quantities. This measurement uses a larger dataset albeit with a smaller t{bar t} fraction. The t{bar t} cross section without b-tagging is measured to be 6.0 ± 0.8(stat) ± 1.0(syst) pb.
Book Synopsis Measurement of the Ttbar Production Cross Section in Ppbar Collisions at S**1/2 by :
Download or read book Measurement of the Ttbar Production Cross Section in Ppbar Collisions at S**1/2 written by and published by . This book was released on 2005 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the measurement of the top quark pair production cross section in p{bar p} collisions at √s = 1.96 TeV using 318 pb−1 of data collected by the CDF detector at the Fermilab Tevatron. We measure the cross section in events with one high transverse momentum electron or muon, large missing transverse energy and three or more jets, where at least one bottom quarks from the top quark decay is identified via a secondary vertex tagging algorithm. The measured t{bar t} cross section is 8.7{sub -0.9}{sup +0.9}(stat){sub -0.9}{sup +1.2}(syst) pb, assuming a top quark mass of 178 GeV. The cross section measurement in the subsample in which both b-quark jets are identified gives 10.1{sub -1.4}{sup +1.6}(stat){sub -1.4}{sup +2.1}(syst) pb. We present one additional measurement of the t{bar t} cross section in the same dataset but without the b-tagging requirement. Top quark events are distinguished from the primary background of W boson production with associated jets using an artificial neural network method with a variety of kinematic quantities. This measurement uses a larger dataset albeit with a smaller t{bar t} fraction. The t{bar t} cross section without b-tagging is measured to be 6.0 ± 0.8(stat) ± 1.0(syst) pb.
Book Synopsis Measurement of the $t\bar{t}$ Production Cross Section Using Events with One Lepton and at Least One Jet in Pp Collisions at $\sqrt{s}$ by :
Download or read book Measurement of the $t\bar{t}$ Production Cross Section Using Events with One Lepton and at Least One Jet in Pp Collisions at $\sqrt{s}$ written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A measurement of the $\mathrm{ t \bar{t} }$ production cross section at $\sqrt{s}=$ 13 TeV is presented using proton-proton collisions, corresponding to an integrated luminosity of 2.3 fb$^{-1}$, collected with the CMS detector at the LHC. Final states with one isolated charged lepton (electron or muon) and at least one jet are selected and categorized according to the accompanying jet multiplicity. From a likelihood fit to the invariant mass distribution of the isolated lepton and a jet identified as coming from the hadronization of a bottom quark, the cross section is measured to be $\sigma(\mathrm{ t \bar{t} })=$ 835 $\pm$ 3 (stat) $\pm$ 23 (syst) $\pm$ 23 (lumi) pb, in agreement with the standard model prediction. Using the expected dependence of the cross section on the pole mass of the top quark ($m_{\mathrm{ t }}$), the value of $m_{\mathrm{ t }}$ is found to be 172.7$^{+2.4}_{-2.7}$ GeV.
Download or read book # Top Physics written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the t{bar t} production cross section using 194 pb−1 of CDF II data using events with a high transverse momentum electron or muon, three or more jets, and missing transverse energy. The measurement assumes 100% t --> Wb branching fraction. Events consistent with t{bar t} decay are found by identifying jets containing heavy flavor semileptonic decays to muons. The dominant backgrounds are evaluated directly from the data. Based on 20 candidate events and an expected background of 9.5 " 1.1 events, we measure a production cross section of 5.3 " 3.3{sub -1.0}{sup +1.3} pb, in agreement with the standard model.
Book Synopsis Measurement of the Ttbar Production Cross Section in Ppbar Collisions at Sqrt(s) by :
Download or read book Measurement of the Ttbar Production Cross Section in Ppbar Collisions at Sqrt(s) written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the top quark pair production cross section in p{bar p} collisions at √s = 1.96 TeV using a data sample corresponding to 1.7 fb−1 of integrated luminosity collected with the Collider Detector at Fermilab. We reconstruct t{bar t} events in the lepton+jets channel, consisting of e[nu]+jets and [mu][nu]+jets final states. The dominant background is the production of W bosons in association with multiple jets. To suppress this background, we identify electrons from the semileptonic decay of heavy-flavor jets ('soft electron tags'). From a sample of 2196 candidate events, we obtain 120 tagged events with a background expectation of 51 ± 3 events, corresponding to a cross section of [sigma]{sub t{bar t}} = 7.8 ± 2.4 (stat) ± 1.6 (syst) ± 0.5 (lumi) pb. We assume a top-quark mass of 175 GeV/c2. This is the first measurement of the t{bar t} cross section with soft electron tags in Run II of the Tevatron.
Download or read book Top Physics written by and published by . This book was released on 2005 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the t{bar t} production cross section using events with one charged lepton and jets from p{bar p} collisions at a center-of-mass energy of 1.96TeV. In these events, heavy flavor quarks from top quark decay are identified with a secondary vertex tagging algorithm. From 162 pb−1 of data collected by the Collider Detector at Fermilab, a total of 48 candidate events are selected, where 13.5 ± 1.8 events are expected from background contributions. We measure a t{bar t} production cross section of 5.6{sub -1.1}{sup _1.2}(stat.){sub -0.6}{sup +0.9}(syst.)pb.
Book Synopsis Measurement of the Ttbar Production Cross Section in the All-jets Final State in Pp Collisions at $\sqrt{s}$ by :
Download or read book Measurement of the Ttbar Production Cross Section in the All-jets Final State in Pp Collisions at $\sqrt{s}$ written by and published by . This book was released on 2015 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: The cross section for tt production in the all-jets final state is measured in pp collisions at a centre-of-mass energy of 8 TeV at the LHC with the CMS detector, in data corresponding to an integrated luminosity of 18.4 fb-1. The inclusive cross section is found to be 275.6 ±6.1 (stat) ± 37.8 (syst) ± 7.2 (lumi) pb. The normalized differential cross sections are measured as a function of the top quark transverse momenta, pT, and compared to predictions from quantum chromodynamics. The results are reported at detector, parton, and particle levels. In all cases, the measured top quark pT spectra are significantly softer than theoretical predictions.
Book Synopsis Measurement of the TtH Production Cross-section with a Collimated H -> Bb Decay in Pp Collisions at Sqrt(s) by : Eftychia Tzovara
Download or read book Measurement of the TtH Production Cross-section with a Collimated H -> Bb Decay in Pp Collisions at Sqrt(s) written by Eftychia Tzovara and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The predictions of the Standard Model (SM) of particle physics have been probed with remarkable accuracy, so far. The Large Hadron Collider (LHC) at CERN has significantly contributed to this quest. A remarkable achievement of the ATLAS and CMS experiments at the LHC was the discovery of the Higgs boson in 2012, the last missing piece of the SM. With the increasing amount of proton-proton collisions delivered by the LHC, more precise measurements of the Higgs boson are now possible, while rare processes are accessible as well. A property of the Higgs boson that is of particular importance is its coupling to the top quark, which is expected to be the strongest in the SM due to the high mass of the top quark. Therefore, its precise measurement is a stringent test of the SM. A direct measurement of the top-quark Yukawa coupling can be assessed through the Higgs-boson production in association with a pair of top quarks (ttH). This thesis presents the measurement of the ttH process with a subsequent Higgs-boson decay to a pair of b-quarks (H -> bb), the decay mode with the largest branching ratio. The measurement is performed with data collected by the ATLAS detector, corresponding to an integrated luminosity of 139 fb^-1 at a center-of-mass energy of 13 TeV. Events with one or two charged leptons from the tt decay in the final state are considered to the measurement. The main challenge of the ttH(H -> bb) channel emerges from the large SM backgrounds from the production of top-quark pairs with additional jets (tt+jets). Also the many jets coming from b-hadrons (b-jets) in the final state cause combinatorial ambiguities. Thus, the identification of such jets is decisive in order to determine the signal and reject many background processes. The ttH events are split into exclusive analysis regions, based on the number of leptons, jets, and jets tagged as b-jets, providing regions enhanced in signal, or in the main background components. Specifically in the single-lepton channel, a boosted category is defined by selecting events in which the Higgs boson and possibly also the hadronically decaying top quark are produced with high transverse momentum (pT), with their decay products being collimated in large-radius jets. The single-lepton boosted channel targets events with Higgs-boson candidate pT >= 300 GeV and is the main scope of this thesis. To identify the reconstructed objects with the underlying particles and to maximise the discrimination of the ttH signal from the overwhelming tt+jets background events in the signal-enriched regions, machine-learning algorithms are employed. The background is dominated by a tt process with an additional gluon in the final state which further splits into a pair of b-quarks (tt+bb). Besides, a large number of heavy-flavour jets in the final state is not well modelled, thus many systematic uncertainties have to be considered, decreasing the sensitivity of the measurement. All the defined analysis regions are analysed together in a combined profile likelihood fit to test for the presence of signal. The fit simultaneously determines the event yields for the signal and the most important background component, while constraining the overall background model within the assigned systematic uncertainties. Eventually, the ratio of the measured ttH cross section to the SM expectation in the inclusive cross-section measurement is found to be 0.35 +0.36,-0.34}, corresponding to an observed (expected) significance of 1.0 (2.7) standard deviations. A ttH signal strength larger than the SM prediction is excluded at 95% confidence level. The measurement uncertainty is dominated by systematic uncertainties, mainly regarding the theoretical knowledge of the tt +>= 1b background process. Finally, to further test the SM, the cross-section is measured differentially as a function of the generator-level Higgs-boson pT, taking advantage of the reconstruction of the Higgs-boson kinematics.
Book Synopsis Measurement of the T Anti-t Production Cross Section in P Anti-p Collisions at S**1/2 by :
Download or read book Measurement of the T Anti-t Production Cross Section in P Anti-p Collisions at S**1/2 written by and published by . This book was released on 2005 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the top quark pair (t{bar t}) production cross section ([sigma]{sub t{bar t}}) in p{bar p} collisions at √s = 1.96 TeV using 230 pb−1 of data collected by the D0 experiment at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), missing transverse energy, and jets in the final state. We employ lifetime-based b-jet identification techniques to further enhance the t{bar t} purity of the selected sample. For a top quark mass of 175 GeV, we measure [sigma]{sub t{bar t}} = 8.6{sub -1.5}{sup +1.6}(stat. + syst.) ± 0.6 (lumi.) pb, in agreement with the standard model expectation.
Book Synopsis Spin Correlations in tt Events from pp Collisions by : Boris Lemmer
Download or read book Spin Correlations in tt Events from pp Collisions written by Boris Lemmer and published by Springer. This book was released on 2015-06-24 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis introduces readers to the Standard Model, the top quark and its properties, before explaining the concept of spin correlation measurement. The first measurement of top quark spin correlations at the LHC in the lepton+jets decay channel is presented. As the heaviest elementary particle, the top quark plays an essential role in the Standard Model of elementary particle physics. In the case of top quarks being produced in pairs at hadron colliders, the Standard Model predicts their spins to be correlated. The degree of correlation depends on both the production mechanism and properties of the top quark. Any deviation from the Standard Model prediction can be an indicator for new physics phenomena. The thesis employs an advanced top quark reconstruction algorithm including dedicated identification of the up- and down-type quarks from the W boson decay.
Book Synopsis Measurement of the T Anti-t Production Cross Section in P Anti-p Collisions at S**ư by :
Download or read book Measurement of the T Anti-t Production Cross Section in P Anti-p Collisions at S**ư written by and published by . This book was released on 2006 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present a measurement of the t{bar t} production cross section using events with one charged lepton and jets from p{bar p} collisions at a center-of-mass energy of 1.96 TeV. A b-tagging algorithm based on the probability of displaced tracks coming from the event interaction vertex is applied to identify b quarks from top decay. Using 318 pb−1 of data collected with the CDF II detector, they measure the t{bar t} production cross section in events with at least one restrictive (tight) b-tagged jet and obtain 8.9{sub -1.0}{sup +1.0}(stat.){sub -1.0}{sup +1.1}(syst.) pb. The cross section value assumes a top quark mass of m{sub t} is presented in the paper. This result is consistent with other CDF measurements of the t{bar t} cross section using different samples and analysis techniques, and has similar systematic uncertainties. They have also performed consistency checks by using the b-tagging probability function to vary the signal to background ratio and also using events that have at least two b-tagged jets.
Book Synopsis Measurement of the Top Quark Pair Production Cross Section and an In-situ B-tagging Efficiency Calibration with ATLAS in Pp Collisions at √s by : Bin Guo
Download or read book Measurement of the Top Quark Pair Production Cross Section and an In-situ B-tagging Efficiency Calibration with ATLAS in Pp Collisions at √s written by Bin Guo and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the top anti-top quark (ttbar)production cross section in the dilepton final states from proton-proton collisions at a center of mass energy at 7 TeV at the LHC. A b-tagging algorithm based on tracks displaced from the event interaction vertex is applied to identify bottom quark jets from top quark decay and reject background events. Given the relatively pure sample of bottom quark jets in ttbar dilepton final states, a new technique to measure in-situ the b-tagging efficiency is introduced that uses the distribution of the number of observed b-tagged jets. We present results with data collected at the ATLAS detector in 2010 with an integrated luminosity of 35 pb-1. The measured ttbar cross section is 176 +22/-21 (stat.) ± 20 (syst.) ± 6 (lum.) pb in the dilepton channel. We will also discuss the future prospects of this measurement.
Book Synopsis Measurement of Jet Multiplicity Distributions in T T-bar Production in Pp Collisions at Sqrt(s) by :
Download or read book Measurement of Jet Multiplicity Distributions in T T-bar Production in Pp Collisions at Sqrt(s) written by and published by . This book was released on 2014 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: The normalised differential top quark-antiquark production cross section is measured as a function of the jet multiplicity in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC with the CMS detector. The measurement is performed in both the dilepton and lepton + jets decay channels using data corresponding to an integrated luminosity of 5.0 inverse femtobarns. Using a procedure to associate jets to decay products of the top quarks, the differential cross section of the t t-bar production is determined as a function of the additional jet multiplicity in the lepton + jets channel. Furthermore, the fraction of events with no additional jets is measured in the dilepton channel, as a function of the threshold on the jet transverse momentum. The measurements are compared with predictions from perturbative quantum chromodynamics and no significant deviations are observed.
Book Synopsis Top Physics: Measurement of the Cross Section for Ttbar Production in Ppbar Collisions Using the Kinematics of Lepton + Jets Events by :
Download or read book Top Physics: Measurement of the Cross Section for Ttbar Production in Ppbar Collisions Using the Kinematics of Lepton + Jets Events written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
