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 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 Symmetry in Particle Physics written by Michal Hnatič and published by MDPI. This book was released on 2021-06-24 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Particle physics is a science about the symmetries of our world. The Standard Model is the fundamental theory of microworld. Particle dynamics in the Standard Model obeys strict symmetry laws with explicit experimental consequences. Priority problems of particle physics based on the Standard Model are more accurate theoretical predictions, experimental measurements and data analysis, proof of existence or non-existence of supersymmetry, top quark properties, Higgs boson, exotic quark states, and physics of neutrinos. In this collection of articles, many of these problems are discussed. We recommend this book for students, graduate students, and scientists working in the field of high energy physics.
Download or read book First Measurement of the Forward backward Asymmetry in Bottom quark Pair Production at High Mass written by and published by . This book was released on 2015 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: We measure the particle-level forward-backward production asymmetry in $\mathrm{b\bar{b}}$ pairs with masses (m$\mathrm{b\bar{b}}$) larger than 150 GeV/c2, using events with hadronic jets and employing jet charge to distinguish b from $\bar{b}$. The measurement uses 9.5 fb-1 of $\mathrm{p\bar{p}}$ collisions at a center-of-mass energy of 1.96 TeV recorded by the CDF II detector. The asymmetry as a function of m$\mathrm{b\bar{b}}$ is consistent with zero, as well as with the predictions of the standard model. The measurement disfavors a simple model including an axigluon with a mass of 200 GeV/c2, whereas a model containing a heavier 345 GeV/c2 axigluon is not excluded.
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 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 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 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 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 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 The Particle Century written by G Fraser and published by CRC Press. This book was released on 1998-01-01 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt: From the first attempts to split the atom to the discovery of the top quark, the 20th century has witnessed a revolution in basic physics. Probing successively smaller constituents of matter has also revealed the conditions present at the time of the Big Bang. In a series of essays by scientists who have been closely involved in this exciting research, The Particle Century describes the unprecedented advances in our understanding of the universe. The book covers major historical developments as well as current advances, including early accelerator physics, the rise of the Standard Model, new comprehension of the big bang theory, and the cutting edge of today's investigations. These essays add novel insight into the continuing efforts to unravel the deepest secrets of nature.
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 Bottom Quark antiquark Rapidity Correlations in Proton antiproton Collisions at square Root Of s written by James D. Olsen and published by . This book was released on 1998 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Download or read book Measurement of Charge Asymmetry in Top Quark Pair Production at the Large Hadron Collider written by Burton Andrew Betchart and published by . This book was released on 2013 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: "We present a measurement of charge asymmetry in the production of top and antitop quark pairs in proton-proton collisions, in a sample of 19:6 fb−1 of data collected by the CMS experiment at 8TeV center of mass energy in 2012. Selected events have a single isolated electron or muon, and at least four jets, at least one of which is likely due to a bottom quark. A template technique is employed to measure top-antitop asymmetry in two kinematic observables simultaneously, which allows attribution of contributions to the observed forward-central asymmetry from distinct Standard Model production mechanisms. An asymmetry Ayc = (0:15 ± 0:42)% is measured in the difference of absolute rapidities of top-antitop pairs, of which (0:00 ± 0:43)% is attributable to quark-antiquark initial states, and (0:18 ± 0:15)% is attributable to quark-gluon initial states. The first measurement of the transverse top quark charge asymmetry is also presented, with the result A[phi]c = (0:44 ± 0:50)%. Measurements of the inclusive asymmetry on selections with high and low top system mass and absolute rapidity are consistent with the main result. The results are compared to Standard Model predictions and measurements from the LHC and the Tevatron"--Page vii.
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 Measurement of the Front Back Asymmetry in Top antitop Quark Pairs Produced in P bar p Collisions at Center of Mass Energy u221A s written by and published by . This book was released on 2006 with total page 125 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$ar{p}$ collisions at 1.8 TeV at the Fermilab Tevatron. The mass of the top quark was measured to be 176 ± 13 GeV/c2 and the cross section 6.8$+3.6top{-2.4}$ pb. It is the Q = 2/3, T3 = +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$ar{p}$ collisions at the Tevatron. Top quark production at the Tevatron is almost exclusively by quark-antiquark annihilation, q$ar{q}$ → t$ar{t}$ (85%), and gluon fusion, gg → t$ar{t}$ (15%), mediated by the strong force. The theoretical cross-section for this process is ?t$ar{t}$ = 6.7 ± 0.8 pb for mt = 175 GeV/c2. Top quarks can also be produced at the Tevatron via q$ar{b}$' → tb and qg → q'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 → Wb). The total decay width t → Wb is ? = 1.50 GeV. This corresponds to an incredibly short lifetime of 0.5 x 10-24 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.
