Measurement Of Spin Correlations In T Tbar Production Using The Matrix Element Method In The Muon Jets Final State In Pp Collisions At U221a S
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Measurement Of Spin Correlations In T Tbar Production Using The Matrix Element Method In The Muon Jets Final State In Pp Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2016
Measurement Of Spin Correlations In T Tbar Production Using The Matrix Element Method In The Muon Jets Final State In Pp Collisions 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 2016 with categories.
The consistency of the spin correlation strength in top quark pair production with the standard model (SM) prediction is tested in the muon+jets final state. The events are selected from pp collisions, collected by the CMS detector, at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb-1. We then compare the data with the expectation for the spin correlation predicted by the SM and with the expectation of no correlation. Furthermore, by using a template fit method, the fraction of events that show SM spin correlations is measured to be 0.72 ±0.08 (stat)+0.15 -0.13 (syst), representing the most precise measurement of this quantity in the lepton+jets final state to date.
Evidence For Spin Correlation In Tt Production
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language : en
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Release Date : 2012
Evidence For Spin Correlation In Tt Production written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
We present a measurement of the ratio of events with correlated t and t spins to the total number of tt events. This ratio f is evaluated using a matrix-element-based approach in 729 tt candidate events with a single lepton l (electron or muon) and at least four jets. The analyzed pp collisions data correspond to an integrated luminosity of 5.3 fb-1 and were collected with the D0 detector at the Fermilab Tevatron collider operating at a center-of-mass energy \(\sqrt{s}=1.96\) TeV. Combining this result with a recent measurement of f in dileptonic final states, we find f in agreement with the standard model. In addition, the combination provides evidence for the presence of spin correlation in tt events with a significance of more than 3 standard deviations.
Evidence For Spin Correlation In T Bar T Production
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language : en
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Release Date : 2011
Evidence For Spin Correlation In T Bar T Production written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
We present a measurement of the ratio of events with correlated t and {bar t} spins to the total number of t{bar t} events. This ratio f is evaluated using a matrix-element-based approach in events with a single lepton (electron or muon) and at least four jets. We analyze p{bar p} collisions data corresponding to an integrated luminosity of 5.3 fb−1 collected with the D0 detector at the Fermilab Tevatron collider operating at a center of mass energy √s = 1.96 TeV. Combining this result with a recent measurement of f in t{bar t} → W+b W−{bar b} → l+ [nu]b l− {bar {nu}}b final states, we find f in agreement with the standard model. In addition, the combination provides evidence for the presence of spin correlation in t{bar t} events with a significance of more than three standard deviations.
Measurement Of Spin Correlations In Top Anti Top Events From Pp Collisions At Sqrt S
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Author :
language : en
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Release Date : 2014
Measurement Of Spin Correlations In Top Anti Top Events From Pp 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 2014 with categories.
The top quark decays before it hadronises. Before its spin state can be changed in a process of strong interaction, it is directly transferred to the top quark decay products. The top quark spin can be deduced by studying angular distributions of the decay products. The Standard Model predicts the top/anti-top quark (tt) pairs to have correlated spins. The degree is sensitive to the spin and the production mechanisms of the top quark. Measuring the spin correlation allows to test the predictions. New physics e ects can be reflected in deviations from the prediction. In this thesis the spin ...
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.
A Search For Resonant Production Of Tt Pairs In 4 8 Fb 1 Of Integrated Luminosity Of Pp Collisions At U221a S
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Author :
language : en
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Release Date : 2011
A Search For Resonant Production Of Tt Pairs In 4 8 Fb 1 Of Integrated Luminosity Of Pp Collisions 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 2011 with categories.
We search for resonant production of tt pairs in 4.8 fb-1 integrated luminosity of pp collision data at √s = 1.96 TeV in the lepton+jets decay channel, where one top quark decays leptonically and the other hadronically. A matrix element reconstruction technique is used; for each event a probability density function (pdf) of the tt candidate invariant mass is sampled. These pdfs are used to construct a likelihood function, whereby the cross section for resonant tt production is estimated, given a hypothetical resonance mass and width. The data indicate no evidence of resonant production of tt pairs. A benchmark model of leptophobic Z' → tt is excluded with mZ'
Measurement Of The Ttbar Production Cross Section At S 1 2
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Author :
language : en
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Release Date : 2005
Measurement Of The Ttbar Production Cross Section 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 2005 with categories.
A measurement of the t[bar t] production cross section in the lepton+jets channels with the D0 detector at [radical]s = 1.96 TeV using the lifetime-tagging techniques is presented. The t[bar t] cross section is estimated from the combination of the e+jets and [mu]+jets channels. The obtained result [sigma][sub tt][sup -] = 7.47 [sub -1.14][sup +1.22](stat)[sub -1.03][sup +1.65](syst) [+-] 0.49 (lumi) pb is consistent with the Standard Model expectation.
Spin Correlation In T Anti T Production From P Anti P Collisions At Radical
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Author :
language : en
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Release Date : 2001
Spin Correlation In T Anti T Production From P Anti P Collisions At Radical written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.
The Standard Model predicts that the lifetime of the top quark is shorter than the typical time scale at which hadronization process occurs, and the spin information at its production is preserved. Spin correlation of the t[anti t] system from p[anti p] collisions at the Tevatron is analyzed using 6 events in the dilepton channels collected using the D0 detector. Spin correlation factor of[kappa]>[minus] 0.25 at 68% CL is obtained from the data.
Spin Correlation In T Anti T Production From P Anti P Collisions At S
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Author :
language : en
Publisher:
Release Date : 2000
Spin Correlation In T Anti T Production From 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 2000 with categories.
The Standard Model predicts that the lifetime of the top quark is shorter than the typical time scale at which hadronization process occurs, and the spin information at its production is preserved. Spin correlation of the t{anti t} system from p{anti p} collisions at the Tevatron is analyzed using 6 events in the dilepton channels collected using the D0 detector. Spin correlation factor of?> - 0.25 at 68% CL is obtained from the data.
Measurements Of The Charm Jet Cross Section And Nuclear Modification Factor In Ppb Collisions At Sqrt S Nn
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language : en
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Release Date : 2016
Measurements Of The Charm Jet Cross Section And Nuclear Modification Factor In Ppb Collisions At Sqrt S Nn written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
The CMS Collaboration presents the first measurement of the differential cross section of jets from charm quarks produced in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of sqrt(s[NN]) = 5.02 TeV, as well as results from charm quark jets in proton-proton (pp) collisions at sqrt(s)= 2.76 and 5.02 TeV. By comparing the yields of the pPb and pp collision systems at the same energy, a nuclear modification factor for charm jets in pPb collisions at sqrt(s[NN]) = 5.02 TeV of R[pA] = 0.92 +/- 0.07 (stat) +/- 0.11 (syst) is obtained. This is consistent with an absence of final-state energy loss for charm quarks in pPb collisions. In addition, the fraction of jets coming from charm quarks is found to be consistent with that predicted by PYTHIA 6 for pp collisions at sqrt(s)= 2.76 and 5.02 TeV, and is independent of the jet transverse momentum from 55 to 400 GeV.