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Measurement Of Top Quark Antiquark Pair Production In Association With A W Or Z Boson In Pp Collisions At Sqrts
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Book Synopsis Measurement of Top Quark-antiquark Pair Production in Association with a W Or Z Boson in Pp Collisions at $\sqrt{s} by :
Download or read book Measurement of Top Quark-antiquark Pair Production in Association with a W Or Z Boson in Pp Collisions at $\sqrt{s} written by and published by . This book was released on 2014 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: A measurement of the cross section for the production of top quark-antiquark pairs (${\mathrm {t}}\overline{{\mathrm {t}}}$) in association with a vector boson V (W or Z) in proton-proton collisions at $\sqrt{s} = 8$ $\, \text {TeV}$ is presented. The results are based on a dataset corresponding to an integrated luminosity of 19.5 fb$^{-1}$ recorded with the CMS detector at the LHC. The measurement is performed in three leptonic (e and $\mu$) channels: a same-sign dilepton analysis targeting ${\mathrm {t}}\overline{{\mathrm {t}}} \mathrm {W} $ events, and trilepton and four-lepton analyses designed for ${\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {Z}} $ events. In the same-sign dilepton channel, the ${\mathrm {t}}\overline{{\mathrm {t}}} \mathrm {W} $ cross section is measured as $\sigma _{{\mathrm {t}}\overline{{\mathrm {t}}} \mathrm {W}} = 170 ^{+90-80}\, \text {(stat)} \pm 70\, \text {(syst)} \, \text {fb} $, corresponding to a significance of 1.6 standard deviations over the background-only hypothesis. Combining the trilepton and four-lepton channels, a direct measurement of the ${\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {Z}} $ cross section, $\sigma _{{\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {Z}}} = 200 ^{+80-70}\, \text {(stat)} ^{+40-30}\, \text {(syst)} \mathrm{fb}^{-1} $, is obtained with a significance of 3.1 standard deviations. The measured cross sections are compatible with standard model predictions within their experimental uncertainties. The inclusive ${\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {V}} $ process is observed with a significance of 3.7 standard deviations from the combination of all three leptonic channels.
Book Synopsis Measurement of Top Quark-antiquark Pair Production in Association with a Z Boson with a Trilepton Final State in Pp Collisions at 8 TeV Center of Mass Energy by : Ian Christopher MacNeill
Download or read book Measurement of Top Quark-antiquark Pair Production in Association with a Z Boson with a Trilepton Final State in Pp Collisions at 8 TeV Center of Mass Energy written by Ian Christopher MacNeill and published by . This book was released on 2015 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for Z boson production with associated top-antitop pairs is performed with a final state which contains trileptons and b-tagged jets. The measurement is performed on the complete dataset of pp collisions at a center-of-mass energy of 8 TeV collected at the CMS detector, for a total instantaneous luminosity of 19.5 fb−1. A cross section is calculated for this final state and compared to the standard model prediction. The cross section for tt̄Z production is measured to be sigma=194+105/−89 fb. The measured cross section to theoretical cross section ratio is 0.94+0̇̇̇·51/−43. The process is measured with a significance of 2.33. This measurement is then combined with an outside 4 lepton channel measurement for an equivalent cross section measurement of sigma=200+90/−76 fb and a significance of 3.1.
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 Observation of Top Quark Pairs Produced in Association with a Vector Boson in Pp Collisions at {u221A}(s) by :
Download or read book Observation of Top Quark Pairs Produced in Association with a Vector Boson in Pp Collisions at {u221A}(s) written by and published by . This book was released on 2016 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: Measurements of the cross sections for top quark pairs produced in association with a W or Z boson are presented, using 8 TeV pp collision data corresponding to an integrated luminosity of 19.5 fb-1, collected by the CMS experiment at the LHC. We found that final states are selected in which the associated W boson decays to a charged lepton and a neutrino or the Z boson decays to two charged leptons. Signal events are identified by matching reconstructed objects in the detector to specific final state particles from tt-W or tt-Z decays. The tt-W cross section is measured to be 382+117 -102 fb with a significance of 4.8 standard deviations from the background-only hypothesis. The tt-Z cross section is measured to be 242+65 -55 fb with a significance of 6.4 standard deviations from the background-only hypothesis. These measurements are used to set bounds on five anomalous dimension-six operators that would affect the tt-W and tt-Z cross sections.
Book Synopsis Measurement of Bottom Quark Pair Production, in Association with Z Bosons and Top Quarks, with the ATLAS Detector by : Stewart Swift (Ph. D. in physics)
Download or read book Measurement of Bottom Quark Pair Production, in Association with Z Bosons and Top Quarks, with the ATLAS Detector written by Stewart Swift (Ph. D. in physics) and published by . This book was released on 2019 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Observation of Top Quark Pairs Produced in Association with a W Or Z Boson in PP Collisions at the LHC by : Andrew Brinkerhoff
Download or read book Observation of Top Quark Pairs Produced in Association with a W Or Z Boson in PP Collisions at the LHC written by Andrew Brinkerhoff and published by . This book was released on 2015 with total page 209 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Measurement of the Associated Production of a Vector Boson (W, Z) and Top Quark Pair in the Opposite Sign Dilepton Channel with Pp Collisions at $\sqrts} by : Tamara Vázquez Schröder
Download or read book Measurement of the Associated Production of a Vector Boson (W, Z) and Top Quark Pair in the Opposite Sign Dilepton Channel with Pp Collisions at $\sqrts} written by Tamara Vázquez Schröder and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Measurement of the Top Quark Pair Production Cross Section in Pp Collisions at Sqrt(s) by :
Download or read book Measurement of the Top Quark Pair Production Cross Section in Pp Collisions at Sqrt(s) written by and published by . This book was released on 2012 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark pair production cross section is measured in dilepton events with one electron or muon, and one hadronically decaying tau lepton from the decay t anti-t to (l nu(l)) (tau nu(tau)) b anti-b, where l can be either an electron or a muon. The data sample corresponds to an integrated luminosity of 2.0 inverse femtobarns for the electron channel and 2.2 inverse femtobarns for the muon channel, collected by the CMS detector at the LHC. This is the first measurement of the t anti-t cross section explicitly including tau leptons in proton-proton collisions at sqrt(s)=7 TeV. The measured value sigma(t anti-t) = 143 +/- 14 (stat.) +/- 22 (syst.) +/- 3 (lumi.) pb is consistent with the standard model predictions.
Book Synopsis Measurements of Top Quark Pair Production Cross Section in Proton Anti-proton Collisions at S**1/2 by :
Download or read book Measurements of Top Quark Pair Production Cross Section in Proton Anti-proton Collisions at S**1/2 written by and published by . This book was released on 2009 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents a new measurement of p{bar p} → t{bar t}X production at √s = 1.96 TeV using 974.2 pb−1 of data collected with the D0 detector between 2002 and 2006. We focus on the final state where the W boson from one of the top quarks decays into a [tau] lepton and its associated neutrino, while the other W boson decays into a quark-antiquark pair. We aim to select those events in which the [tau] lepton subsequently decays hadronically, meaning to one or three charged hadrons, zero or more neutral hadrons and a tau neutrino (the charge conjugate processes are implied in all of the above). The observable signature thus consists of a narrow calorimeter shower with associated track(s) characteristic of a hadronic tau decay, four or more jets, of which two are initiated by b quarks accompanying the W's in the top quark decays, and a large net missing momentum in the transverse plane due to the energetic neutrino-antineutrino pair that leave no trace in the detector media. The preliminary result for the measured cross section is: [sigma](t{bar t}) = 6.9{sub -1.2}{sup +1.2}(stat){sub -0.7}{sup +0.8}(syst) ± 0.4 (lumi) pb. This indicates that our finding is consistent with the Standard Model prediction.
Book Synopsis Measurement of the Charge Asymmetry in Top Quark Pair Production in Pp Collisions at $\sqrt{s}$ by :
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.
Book Synopsis Measurement of the Charge Asymmetry in Top-quark Pair Production in Proton-proton Collisions at Sqrt(s) by :
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.
Book Synopsis Measurements of the Associated Production of a Top Quark Pair and a Z Boson with the ATLAS Detector by : Laurynas Mince
Download or read book Measurements of the Associated Production of a Top Quark Pair and a Z Boson with the ATLAS Detector written by Laurynas Mince and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Observation of Top-quark Pair Production in Association with a Photon and Measurement of the Tt{u00AF}? Production Cross Section in pp Collisions at {u221A}s by :
Download or read book Observation of Top-quark Pair Production in Association with a Photon and Measurement of the Tt{u00AF}? Production Cross Section in pp Collisions at {u221A}s written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search is performed for top-quark pairs (tt¯) produced together with a photon (?) with transverse energy greater than 20 GeV using a sample of tt¯ candidate events in final states with jets, missing transverse momentum, and one isolated electron or muon. The data set used corresponds to an integrated luminosity of 4.59 fb−1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. In total, 140 and 222 tt¯? candidate events are observed in the electron and muon channels, to be compared to the expectation of 79 ± 26 and 120 ± 39 non-tt¯? background events, respectively. The production of tt¯? events is observed with a significance of 5.3 standard deviations away from the null hypothesis. The tt¯? production cross section times the branching ratio (BR) of the single-lepton decay channel is measured in a fiducial kinematic region within the ATLAS acceptance. The measured value is ?fidtt¯? × BR = 63 ± 8(stat)+17–13(syst) ± 1(lumi) fb per lepton flavor, in good agreement with the leading-order theoretical calculation normalized to the next-to-leading-order theoretical prediction of 48 ± 10 fb.
Book Synopsis Measurements of the Top Quark Pair Production Cross Section and Branching Ratio to a W-boson and Bottom Quark Using the Semi-leptonic and Dilepton Final States with the ATLAS Detector at the LHC by : Robert E. Calkins
Download or read book Measurements of the Top Quark Pair Production Cross Section and Branching Ratio to a W-boson and Bottom Quark Using the Semi-leptonic and Dilepton Final States with the ATLAS Detector at the LHC written by Robert E. Calkins and published by . This book was released on 2012 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract : In the Standard Model, the top quark plays a unique role as the heaviest known fundamental particle and as a quark that decays before it is able to hadronize. Top quarks are expected to decay to a W-boson and a b-quark nearly 100% of the time. If the branching ratio of t → Wb is lower than one, the distribution of the number of b-tagged jets will shift to lower multiplicities. A simultaneous likelihood fit to the number of b-tagged jets distributions in the lepton+jets and dilepton channels is performed on 4.7 fb−1 of data collected by the ATLAS detector to extract both the branching ratio and the tt ̄ cross section. The branching ratio of t → Wb, R, is measured to be 1.06±0.11, which is consistent with the Standard Model value. This is the first measurement of the t → Wb branching ratio performed with the ATLAS detector using both the lepton+jets and dilepton channels at the LHC. The tt ̄ cross section is measured to be [special characters omitted] pb, which agrees with NNLO predictions.
Book Synopsis Search for Same-sign Top-quark Pair Production at Sqrt(s) by :
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.
Book Synopsis Measurement of the Top Quark Pair Production Cross Section in Pp Collisions at a Center-of-mass Energy of 7 TeV with the CMS Experiment at the LHC by : Geng-Yuan Jeng
Download or read book Measurement of the Top Quark Pair Production Cross Section in Pp Collisions at a Center-of-mass Energy of 7 TeV with the CMS Experiment at the LHC written by Geng-Yuan Jeng and published by . This book was released on 2011 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: We perform a measurement of the top quark pair production cross section in pp collisions at a center-of-mass energy of 7 TeV at the Large Hadron Collider. The analysis is based on a 36 pb -1 dataset collected with the CMS experiment in 2010. We study the kinematic characteristics of events with exactly one isolated muon in association with additional hard jets and exhibiting substantial missing transverse energy to distinguish the tt− signal from the electroweak and QCD multijet backgrounds. The tt− signal is extracted by simultaneously fitting the tri-jet invariant mass distributions in events with exactly three jets and at least four jets. The measured cross section is 157 ± 12(stat.[Special characters omitted.] (syst.) ± 6(lumi.) pb, which is consistent with the theoretical predictions.
Book 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
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.
