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Author : James C. Romano
Publisher :
ISBN 13 :
Total Pages : 214 pages
Book Rating : 4.:/5 (341 download)
Download or read book A Search for Top Quark Pair Production in the Dilepton Decay Mode written by James C. Romano and published by . This book was released on 1995 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for Direct Pair Production of Scalar Top Quarks in the Single- and Dilepton Channels in Proton-proton Collisions at $\sqrt{s}$ written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Results are reported from a search for the top squark $ \tilde{t}_1 $, the lighter of the two supersymmetric partners of the top quark. The data sample corresponds to 19.7 fb$^{-1}$ of proton-proton collisions at $\sqrt{s} =$ 8 TeV collected with the CMS detector at the LHC. The search targets $ \tilde{t}_1 \to \mathrm{b} \tilde{\chi}^{\pm}_1$ and $ \tilde{t}_1 \to \mathrm{t}^{(*)} \tilde{\chi}^0_1$ decay modes, where $\tilde{\chi}^{\pm}_1$ and $\tilde{\chi}^0_1$ are the lightest chargino and neutralino, respectively. The reconstructed final state consists of jets, b jets, missing transverse energy, and either one or two leptons. Leading backgrounds are determined from data. No significant excess in data is observed above the expectation from standard model processes. The results exclude a region of the two-dimensional plane of possible $ \tilde{t}_1 $ and $\tilde{\chi}^0_1 $ masses. The highest excluded $ \tilde{t}_1 $ and $ \tilde{\chi}^0_1$ masses are about 700 GeV and 250 GeV, respectively.
Author :
Publisher :
ISBN 13 :
Total Pages : 10 pages
Book Rating : 4.:/5 (685 download)
Download or read book Search for the Top Quark in the Single Lepton + Jets Channel at written by and published by . This book was released on 1993 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have searched for standard model top quark pair production at (square root)s = 1.8 TeV. We present preliminary results of searches in the single lepton decay modes (i.e. where one top quark decays semileptonically to an electron or a muon and the other top quark decayed hadronically). We do not find evidence for top quark production in these decay channels. By combining this negative result with our negative result from the dilepton decay channels, we obtain a 95% confidence level upper limit on the top quark production cross section for top masses between 80 and 140 GeV/c2. By comparing this cross section upper limit curve with a theoretical production cross section we obtain a lower limit on the top quark mass of 124 GeV/c2.
Author : William Johnson
Publisher :
ISBN 13 : 9781124219684
Total Pages : pages
Book Rating : 4.2/5 (196 download)
Download or read book Search for Pair Production of Supersymmetric Top Quarks in Dilepton Events at the Tevatron written by William Johnson and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We search for pair production of the supersymmetric partner of the top quark, the stop quark, decaying to a b-quark and a chargino with a subsequent decay into a neutralino, lepton, and neutrino. Using 2.7 fb−1 of [square root]s=1.96 TeV proton on antiproton collision data collected by the CDF II experiment, we reconstruct the mass of candidate stop events and fit the observed mass spectrum to a combination of standard model processes and stop signal. No evidence of stop pair production is found, therefore we set 95% C.L. limits on the masses of the stop and the neutralino for several values of the chargino mass and the branching ratio B(X̃±/1[right arrow]X̃01l±v).
Download or read book Search for Pair Production of Supersymmetric Top Quarks in Dilepton Events from $p\bar{p}$ Collisions at $\sqrt{s}$ written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the results of a search for pair production of the supersymmetric partner of the top quark (the stop quark ≈1) decaying to a b-quark and a chargino {tilde {chi}}1{sup {+-}} with a subsequent {tilde {chi}}1{sup {+-}} decay into a neutralino {tilde {chi}}1°, lepton l, and neutrino [nu]. Using a data sample corresponding to 2.7 fb−1 of integrated luminosity of p{bar p} collisions at √s = 1.96 TeV collected by the CDF II detector, we reconstruct the mass of candidate stop events and fit the observed mass spectrum to a combination of standard model processes and stop quark signal. We find no evidence for {tilde t}1{bar {tilde t}}1 production and set 95% C.L. limits on the masses of the stop quark and the neutralino for several values of the chargino mass and the branching ratio [Beta]({tilde {chi}}1{sup {+-}} → {tilde {chi}}1°l{sup {+-}}[nu]).
Download or read book Measurement of the Top Anti-top Quark Pair Production Cross Section in the Dilepton Decay Channel Using Lepton+Track Selection in 7 TeV P - P Collisions with L written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 146 pages
Book Rating : 4.:/5 (16 download)
Download or read book Search for Pair Production of Supersymmetric Top Quarks in Dilepton Events at the Tevatron written by and published by . This book was released on 2010 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: We search for pair production of the supersymmetric partner of the top quark, the stop quark $̃ar{t}$1, decaying to a b-quark and a chargino X-±1 with a subsequent X-±1 decay into a neutralino X-1 , lepton l, and neutrino . Using 2.7 fb-1 of √s = 1.96 TeV p$ar{p}$ collision data collected by the CDF II experiment, we reconstruct the mass of candidate stop events and t the observed mass spectrum to a combination of standard model processes and stop signal. No evidence of $̃ar{t}$1 $ar{t}$1 production is found, therefore we set 95% C.L. limits on the masses of the stop and the neutralino for several values of the chargino mass and the branching ratio B (X-±1 → X-01 l±v).
Author :
Publisher :
ISBN 13 :
Total Pages : 218 pages
Book Rating : 4.:/5 (953 download)
Download or read book Top Pair Production in the Dilepton Decay Channel with a Tau Lepton written by and published by . This book was released on 2012 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark pair production and decay into leptons with at least one being a [tau] lepton is studied in the framework of the CDF experiment at the Tevatron proton antiproton collider at Fermilab (USA). The selection requires an electron or a muon produced either by the [tau] lepton decay or by a W decay. The analysis uses the complete Run II data set i.e. 9.0 fb-1, selected by one trigger based on a low transverse momentum electron or muon plus one isolated charged track. The top quark pair production cross section at 1.96 TeV is measured at 8.2 ± 1.7+1.2-1.1 ± 0.5 pb, and the top branching ratio into [tau] lepton is measured at 0.120 ± 0.027+0.022 -0.019 ± 0.007 with statistical, systematics and luminosity uncertainties. These are up to date the most accurate results in this top decay channel and are in good agreement with the results obtained using other decay channels of the top at the Tevatron. The branching ratio is also measured separating the single lepton from the two leptons events with a log likelihood method. This is the first time these two signatures are separately identified. With a fit to data along the log-likelihood variable an alternative measurement of the branching ratio is made: 0.098 ± 0.022(stat:) ± 0.014(syst:); it is in good agreement with the expectations of the Standard Model (with lepton universality) within the experimental uncertainties. The branching ratio is constrained to be less than 0.159 at 95% con dence level. This limit translates into a limit of a top branching ratio into a potential charged Higgs boson.
Download or read book Measurement of the Top Quark Pair Production Cross-section in the Dilepton Channel Using Lepton Plus Track Selection and Identified B-jets written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Using 1.0 fb^{-1} of data collected by the Collider Detector at Fermilab (CDF) from Run II of the Fermilab Tevatron, we measure the top-antitop production cross-section in events with two leptons, significant missing transverse energy, and at least jets, at least one of which is identified as a b-jet. As the Run II dataset grows, more stringent tests of Standard Model predictions for the top quark sector are becoming possible. The dilepton channel, where both top quarks decay t-> W b ->l nu b, is of particular interest due to its high purity. Use of an isolated track as the second lepton significantly increases the dilepton acceptance, at the price of some increase in background, particularly from W + jets events where one of the jets is identified as a lepton. To control the increase in background we add to the event selection the requirement that at least one of the jets be identified as a b-jet, reducing the background contribution from all sources. Assuming a branching ratio of BR(W->l nu) = 10.8% and a top mass of m_top = 175 GeV/c^{2} the measured cross-section is sigma = (10.5 +/- 1.8 stat. +/- 0.8 syst. +/- 0.6 lumi.) pb.
Author :
Publisher :
ISBN 13 :
Total Pages : 145 pages
Book Rating : 4.:/5 (16 download)
Download or read book Search for Scalar Top Quark Pair-Production in Scenario with Violated R-parity in Pp{u00AF} Collisions at {u221A}s written by and published by . This book was released on 2005 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for the pair production of supersymmetric partner of the top quark in scenario with R-parity violation is presented. The quantum number called R-parity distinguishes particles in standard model from supersymmetric particles. A scalar top quark (stop) is assumed to decay only via Rp-violating supersymmetric coupling into tau lepton and b-quark. To collect events with multiple taus, a new special tau trigger (the lepton plus track trigger) is installed in Run II experiment of the Collider Detector at Fermilab (CDF). The goal of the lepton plus track trigger is to collect generic dilepton (ll, l?, ??) events with lower pT threshold (8 GeV/c) and without prescale even at high luminosity. The Z → ?? event, where one ?-lepton decays leptonically and the other hadronically, is a good benchmark to calibrate the lepton plus track trigger and ? identification. The data sample of 72 pb-1, collected using the electron plus track trigger, contains clear a ? signal from Z → ?? events. The data used in stop search correspond to 200 pb-1. The lower stop mass bound of 134 GeV/c2 at a 95% confidence level is obtained. This limit is also directly applicable to the case of the third generation scalar leptoquark (LQ3) assuming a 100% branching for the LQ3 → ?b decay mode.
Author :
Publisher :
ISBN 13 :
Total Pages : 5 pages
Book Rating : 4.:/5 (873 download)
Download or read book Search for the Top Quark in Dilepton Decay Modes at written by and published by . This book was released on 1995 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present preliminary results on the search for the top quark in p{bar p} collisions at √s = 1.8 TeV by the D0 collaboration at the Fermilab Tevatron. The results are based on an integrated luminosity of 13.5 pb−1 of data collected by the D0 detector during the 1992-3 Tevatron collider run. They have searched for Standard Model t{bar t} decays into the dilepton decay modes ee + X, e[mu] + X and [mu][mu] + X. No significant signal is observed for top quark production in these channels. They find one candidate event in the e[mu] + X channel and no events in the other two channels with an estimated non-top background of 0.76 ± 0.16 events.
Author : Robert E. Calkins
Publisher :
ISBN 13 : 9781267906960
Total Pages : 241 pages
Book Rating : 4.9/5 (69 download)
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.
Author :
Publisher :
ISBN 13 :
Total Pages : 159 pages
Book Rating : 4.:/5 (727 download)
Download or read book Study on the Top Quark Pair Production Mechanism in 1.96 TeV Proton-antiproton Collisions written by and published by . This book was released on 2008 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of the top quark pair production mechanism in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV is described. The main subjects are the measurements of the top quark pair production cross section, the top quark mass and a search for a new particle decaying to the top quark pair. The analyses are based on 1.9 fb−1 of data collected by the Collider Detector at Fermilab (CDF) Run II experiment between March 2002 and May 2007, using the lepton+jets events. The measured top quark pair production cross section is 8.2 ± 0.5 (stat.) ± 0.8 (syst.) ± 0.5 (lum.) pb, which is slightly higher than the standard model prediction at the top mass of 175 GeV/c2. The top quark mass is an important parameter in the standard model, and also in the experimental studies. The measured top quark mass if 171.6 ± 2.0 (stat.) ± 1.3(syst.) GeV/c2. Finally, they report on a search for a new gauge boson decaying to t{bar t}, which interferes with the standard model gluon in the q{bar q} --> t{bar t} production process. They call such a hypothetical particle a 'Massive Gluon'. The observed t{bar t} invariant mass distribution is consistent with the standard model expectations, and also the measured massive gluon coupling strength with quarks is consistent within a statistical fluctuation of the standard model expectation in the wide range of the massive gluon masses and widths. They set the upper and lower limits on the coupling strength of the massive gluon.
Author : Takashi Ogawa
Publisher :
ISBN 13 :
Total Pages : 145 pages
Book Rating : 4.:/5 (316 download)
Download or read book Search for Scalar Top Quark Pair-Production in Scenario with Violated R-parity in Ppbar Collisions at Sqrt(s) written by Takashi Ogawa and published by . This book was released on 2005 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for the pair production of supersymmetric partner of the top quark in scenario with R-parity violation is presented. The quantum number called R-parity distinguishes particles in standard model from supersymmetric particles. A scalar top quark (stop) is assumed to decay only via R{sub p}-violating supersymmetric coupling into tau lepton and b-quark. To collect events with multiple taus, a new special tau trigger (the lepton plus track trigger) is installed in Run II experiment of the Collider Detector at Fermilab (CDF). The goal of the lepton plus track trigger is to collect generic dilepton ({ell}{ell}, {ell}{tau}, {tau}{tau}) events with lower p{sub T} threshold (8 GeV/c) and without prescale even at high luminosity. The Z {yields} {tau}{tau} event, where one {tau}-lepton decays leptonically and the other hadronically, is a good benchmark to calibrate the lepton plus track trigger and {tau} identification. The data sample of 72 pb{sup -1}, collected using the electron plus track trigger, contains clear a {tau} signal from Z {yields} {tau}{tau} events. The data used in stop search correspond to 200 pb{sup -1}. The lower stop mass bound of 134 GeV/c{sup 2} at a 95% confidence level is obtained. This limit is also directly applicable to the case of the third generation scalar leptoquark (LQ{sub 3}) assuming a 100% branching for the LQ{sub 3} {yields} {tau}b decay mode.
Author :
Publisher :
ISBN 13 :
Total Pages : 9 pages
Book Rating : 4.:/5 (16 download)
Download or read book Top Quark Physics and Searches for New Phenomena at the Tevatron written by and published by . This book was released on 1998 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: The CDF and D0 collaborations each have collected over 110 pb−1 from top quark physics and searches for first generation leptoquarks (LQ), using the entire statistics of these large data sets. After careful selection, both collaborations have collected top quark data samples consisting of several dozen events each. From these events both experiments have measured the top quark mass and pair production cross section in a variety of decay channels, including the so-called dilepton, lepton plus jets, and all jets channels. The combined top quark mass from both experiments in the lepton plus jets channels is m{sub t} = 175.6±5.5 GeV/c2. CDF and D0 have also performed optimized searches for the pair production of first generation leptoquarks. No candidate events were found. Combining the results from the ee+jets, e?+jets, and??+jets channels both experiments set 95% confidence level (CL) upper limits on the LQ pair production cross section as a function of mass and of?, the branching fraction to a charged lepton.
Author :
Publisher :
ISBN 13 :
Total Pages : 704 pages
Book Rating : 4.:/5 (31 download)
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Michael Werth
Publisher :
ISBN 13 : 9781267256621
Total Pages : 115 pages
Book Rating : 4.2/5 (566 download)
Download or read book Search for Fourth Generation Quarks in the Dilepton Channel at ATLAS with Sqrt(s) written by Michael Werth and published by . This book was released on 2012 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search is presented for heavy-quark pair production (QQ̄) under the decay hypothesis QQ̄ to W+qW-q̄ with q = u,d,c,s,b. The search is performed with 1.04 fb-1 of integrated luminosity from pp collisions at √s = 7 TeV collected by the ATLAS detector at the CERN Large Hadron Collider (LHC). Events are selected with two oppositely-charged leptons (e or mu), large missing transverse momentum and at least two jets. Mass reconstruction of heavy quark candidates is performed by assuming that the W boson decay products are nearly collinear. The data are in agreement with Standard Model expectations; a heavy quark with mass less than 350 GeV is excluded at 95% confidence level.
