Measurement Of The Relative Fraction Of Ttbar Events Produced Via Gluon Fusion In Ppbar Collision At Square Root Of S
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Measurement Of The Relative Fraction Of Ttbar Events Produced Via Gluon Fusion In Ppbar Collision At Square Root Of S
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Author :
language : en
Publisher:
Release Date : 2007
Measurement Of The Relative Fraction Of Ttbar Events Produced Via Gluon Fusion In Ppbar Collision At Square Root Of S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Particles (Nuclear physics) categories.
In this thesis we present a measurement of the relative fraction of ttbar events produced via gluon-fusion to the total number of ttbar events. Using the kinematics of the production and decay of the top and antitop quark pair, we trained a Neural Network to discriminate the gluon-fusion events. The Neural Network was then used as a template to fit for the gluon-fusion fraction in data. Using a total integrated luminosity of 955 pb-1 we find the fraction of gluon-fusion event in all ttbar events to be
Measurement Of The Relative Fraction Of Ttbar Events Produced Via Gluon Fusion In Ppbar Collision At S 1 2
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Author :
language : en
Publisher:
Release Date : 2007
Measurement Of The Relative Fraction Of Ttbar Events Produced Via Gluon Fusion In Ppbar Collision At S 1 2 written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
In this thesis we present a measurement of the relative fraction of t{bar t} events produced via gluon-fusion to the total number of t{bar t} events. Using the kinematics of the production and decay of the top and antitop quark pair, we trained a Neural Network to discriminate the gluon-fusion events. The Neural Network was then used as a template to fit for the gluon-fusion fraction in data. Using a total integrated luminosity of 955 pb−1 we find [sigma](gg2!{bar t})/[sigma](p{bar p}2!{bar t})
Measurement Of The Relative Fraction Of T Bar T Events Produced Via Gluon Fusion In P Bar P Collision At U221a S
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language : en
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Release Date : 2007
Measurement Of The Relative Fraction Of T Bar T Events Produced Via Gluon Fusion In P Bar P Collision At U221a S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
In this thesis we present a measurement of the relative fraction of t$ar{t}$ events produced via gluon-fusion to the total number of t$ar{t}$ events. Using the kinematics of the production and decay of the top and antitop quark pair, we trained a Neural Network to discriminate the gluon-fusion events. The Neural Network was then used as a template to fit for the gluon-fusion fraction in data. Using a total integrated luminosity of 955 pb-1 we find ?(gg→t$ar{t}$)/?(p$ar{p}$→t$ar{t}$)
Measurement Of The Fraction Of T Anti T Production Via Gluon Gluon Fusion In P Anti P Collisions At S
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Author :
language : en
Publisher:
Release Date : 2008
Measurement Of The Fraction Of T Anti T Production Via Gluon Gluon Fusion In P Anti P Collisions At S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
First Measurement Of Sigma Gg Ttbar Sigma Ppbar Ttbar
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language : en
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Release Date : 2008
First Measurement Of Sigma Gg Ttbar Sigma Ppbar Ttbar written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
The work presented here is the first measurement of the fraction of top quark pair production through gluon-gluon fusion. We use an integrated luminosity of 0.96 ± 0.06 fb−1 of p{bar p} collisions at √s of 1.96 TeV collected by the CDF II detector. We select t{bar t} candidates by identifying a high-p{sub T} lepton candidate, a large missing E{sub T} as evidence for a neutrino candidate and at least four high E{sub T} jets, one of which has to be identified as originating from a b quark. The challenge is to discriminate between the two production processes with the identical final state, gg → t{bar t} and q{bar q} → t{bar t}. We take advantage of the fact that compared to a quark, a gluon is more likely to radiate a low momentum gluon and therefore, one expects a larger number of charged particles with low p{sub T} in a process involving more gluons. Given the large uncertainties associated with the modeling of the low p{sub T} charged particle multiplicity, a data-driven technique was employed. Using calibration data samples, we show there exists a clear correlation between the observed average number of low p{sub T} charged particles and the average number of gluons involved in the production process predicted by Monte Carlo calculations. Given the correlation, one can identify low p{sub T} charged particle multiplicity distributions associated with specific average number of gluons. The W + 0 jet sample and dijets sample with leading jet E{sub T} in the range of 80-100 GeV are used to find no-gluon and gluon-rich low p{sub T} charged particle multiplicity distributions, respectively. Using these no-gluon and gluon-rich distributions in a likelihood fit, we find the fraction of gluon-rich events in t{bar t} candidates. This fraction has contributions from the signal and background events. Taking into account these contributions and the gg → t{bar t} and q{bar q} → t{bar t} production channel acceptances, we find [sigma](gg → t{bar t})/[sigma](p{bar p} → t{bar t}) = 0.07 ± 0.14(stat) ± 0.07(syst) in agreement with the theoretical predictions of 0.15 ± 0.05. This measurement is a stepping stone towards a better understanding of the production mechanism of top quark pairs and implies that at least 67% of the t{bar t} events are consistent with q{bar q} production at 95% C.L, leaving little room for non SM processes which are not similar to the q{bar q} → t{bar t} in their gluon radiation. The result confirms our current understanding of the SM high p{sub T} production mechanism and the relative gluon PDFs at relatively high Q2 and x.
Measurement Of The Fraction Of T Anti T Production Via Gluon Gluon Fusion In P Anti P Collisions At S 1 2
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Author :
language : en
Publisher:
Release Date : 2008
Measurement Of The Fraction Of T Anti T Production Via Gluon Gluon Fusion In P Anti P Collisions At S 1 2 written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
Large Pt Processes In Ppbar Collisions At 2 Tev
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Author : Ashish Kumar
language : en
Publisher:
Release Date : 2005
Large Pt Processes In Ppbar Collisions At 2 Tev written by Ashish Kumar and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
The measurement of the top-antitop pair production cross section in p{bar p} collisions at {radical}s = 1.96 TeV in the dielectron decay channel using 384 pb{sup -1} of D0 data yields a t{bar t} production cross-section of {sigma}{sub t{bar t}} = 7.9{sub -3.8}{sup +5.2}(stat){sub -1.0}{sup +1.3}(syst) {+-} 0.5 (lumi) pb. This measurement [98] is based on 5 observed events with a prediction of 1.04 background events. The cross-section corresponds to the top mass of 175 GeV, and is in good agreement with the Standard Model expectation of 6.77 {+-} 0.42 pb based on next-to-next-leading-order (NNLO) perturbative QCD calculations [78]. This analysis shows significant improvement from our previous cross-section measurement in this channel [93] with 230 pb{sup -1} dataset in terms of significantly better signal to background ratio and uncertainties on the measured cross-section. Combination of all the dilepton final states [98] yields a yields a t{bar t} cross-section of {sigma}{sub t{bar t}} = 8.6{sub -2.0}{sup +2.3}(stat){sub -1.0}{sup +1.2}(syst) {+-} 0.6(lumi) pb, which again is in good agreement with theoretical predictions and with measurements in other final states. Hence, these results show no discernible deviation from the Standard Model. Fig. 6.1 shows the summary of cross-section measurements in different final states by the D0 in Run II. This measurement of cross-section in the dilepton channels is the best dilepton result from D0 till date. Previous D0 result based on analysis of 230 pb{sup -1} of data (currently under publication in Physics Letters B) is {sigma}{sub t{bar t}} = 8.6{sub -2.7}{sup +3.2}(stat){sub -1.1}{sup +1.1}(syst) {+-} 0.6(lumi) pb. It can be seen that the present cross-section suffers from less statistical uncertainty. This result is also quite consistent with CDF collaboration's result of {sigma}{sub t{bar t}} = 8.6{sub -2.4}{sup +2.5}(stat){sub -1.1}{sup +1.1}(syst) pb. These results have been presented as D0's preliminary results in the high energy physics conferences in the Summer of 2005 (Hadron Collider Physics Symposium, European Physical Society Conference, etc.). The uncertainty on the cross-section is still dominated by statistics due to the small number of observed events. It can be seen that we are at a level where statistical uncertainties are becoming closer to the systematic ones. Future measurements of the cross section will benefit from considerably more integrated luminosity, leading to a smaller statistical error. Thus the next generation of measurements will be limited by systematic uncertainties. Monte Carlo samples with higher statistics are also being generated in order to decrease the uncertainty on the background estimation. In addition, as the jet energy scale, the electron energy scale, the detector resolutions, and the luminosity measurement are fine-tuned, the systematic uncertainties will continue to decrease.
Measurement Of Tt Production Cross Section In Pp Collisions At Square Root S
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Author : Harpreet Singh
language : en
Publisher:
Release Date : 1999
Measurement Of Tt Production Cross Section In Pp Collisions At Square Root S written by Harpreet Singh and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with Collisions (Nuclear physics) categories.
Measurement Of The Top Pair Production Cross Section In The Dilepton Decay Channel In Ppbar Collisions At Sqrt S
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language : en
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Release Date : 2010
Measurement Of The Top Pair Production Cross Section In The Dilepton Decay Channel In Ppbar Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
A measurement of the t{bar t} production cross section in p{bar p} collisions at √s = 1.96 TeV using events with two leptons, missing transverse energy, and jets is reported. The data were collected with the CDF II Detector. The result in a data sample corresponding to an integrated luminosity 2.8 fb−1 is: [sigma]{sub t{bar t}} = 6.27 ± 0.739(stat) ± 0.63(syst) ± 0.39(lum) pb for an assumed top mass of 175 GeV/c2.
Double Parton Interactions In Photon 3 Jet Events In Ppbar Collisions Sqrt S
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Author :
language : en
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Release Date : 2009
Double Parton Interactions In Photon 3 Jet Events In Ppbar Collisions Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
We have used a sample of photon+3 jets events collected by the D0 experiment with an integrated luminosity of about 1 fb−1 to determine the fraction of events with double parton scattering (f{sub DP}) in a single ppbar collision at √s = 1.96 TeV. The DP fraction and effective cross section (sigma{sub eff}), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in p{sub T}) jet transverse momentum pT{sub jet2} within the range 15