Measurement Of The Polarisation Of Single Top Quarks And Antiquarks Produced In The T Channel At Square Root S
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Measurement Of The Polarisation Of Single Top Quarks And Antiquarks Produced In The T Channel At Square Root S
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Author : [Study Group] ATLAS Collaboration CERN
language : en
Publisher:
Release Date : 2022
Measurement Of The Polarisation Of Single Top Quarks And Antiquarks Produced In The T Channel At Square Root S written by [Study Group] ATLAS Collaboration CERN and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with categories.
Abstract: A simultaneous measurement of the three components of the top-quark and top-antiquark polarisation vectors in t-channel single-top-quark production is presented. This analysis is based on data from proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 139 fb−1, collected with the ATLAS detector at the LHC. Selected events contain exactly one isolated electron or muon, large missing transverse momentum and exactly two jets, one being b-tagged. Stringent selection requirements are applied to discriminate t-channel single-top-quark events from the background contributions. The top-quark and top-antiquark polarisation vectors are measured from the distributions of the direction cosines of the charged-lepton momentum in the top-quark rest frame. The three components of the polarisation vector for the selected top-quark event sample are Px′ = 0.01 ± 0.18, Py′ = −0.029 ± 0.027, Pz′ = 0.91 ± 0.10 and for the top-antiquark event sample they are Px′ = −0.02 ± 0.20, Py′ = −0.007 ± 0.051, Pz′ = 0.79 ± 0.16. Normalised differential cross-sections corrected to a fiducial region at the stable-particle level are presented as a function of the charged-lepton angles for top-quark and top-antiquark events inclusively and separately. These measurements are in agreement with Standard Model predictions. The angular differential cross-sections are used to derive bounds on the complex Wilson coefficient of the dimension-six OtW operator in the framework of an effective field theory. The obtained bounds are CtW ∈ [−0.9, 1.4] and CitW ∈ [−0.8, 0.2], both at 95% confidence level
Measurement Of Top Quark Polarisation In T Channel Single Top Quark Production
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Author :
language : en
Publisher:
Release Date : 2015
Measurement Of Top Quark Polarisation In T Channel Single Top Quark 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 2015 with categories.
Our first measurement of the top quark spin asymmetry, sensitive to the top quark polarisation, in t-channel single top quark production is presented. It is based on a sample of pp collisions at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb-1. A high-purity sample of t-channel single top quark events with an isolated muon is selected. Signal and background components are estimated using a fit to data. Furthermore, a differential cross section measurement, corrected for detector effects, of an angular observable sensitive to the top quark polarisation is performed. The differential distribution is used to extract a top quark spin asymmetry of 0.26 ± 0.03 (stat) ± 0.10 (syst), which is compatible with a p-value of 4.6% with the standard model prediction of 0.44.
Measurement Of The Single Top Quark Production Cross Section At The Square Root Of S
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Author : Mark Anthony Padilla
language : en
Publisher:
Release Date : 2011
Measurement Of The Single Top Quark Production Cross Section At The Square Root Of S written by Mark Anthony Padilla and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with Particle accelerators categories.
The s channel has a Gaussian significance of 1.6[sigma], the t channel 5.5[sigma], and the s + t 4.3[sigma]. The results are consistent with the standard model predictions within one standard deviation. By combining these results with the results for two other analyses (using different MVA techniques) improved results of: Combined s + t channels : [sigma](ppbar [arrow right] tb + X, tqb + X) = 3.43 + 0.73 - 0.74 pb, t channel : [sigma](ppbar [arrow right] tqb + X) = 2.90 + 0.59 - 0.59 pb. were obtained. These give a 5.6[sigma] significance for the combined s + t channel and 5.5[sigma] for the t channel.
Measurement Of The T Channel Single Top Quark Production Cross Section In Pp Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2011
Measurement Of The T Channel Single Top Quark Production Cross Section In 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 2011 with categories.
Electroweak production of the top quark is measured in pp collisions at sqrt(s) = 7 TeV, using a dataset collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 36 inverse picobarns. With an event selection optimized for t-channel production, two complementary analyses are performed. The first one exploits the special angular properties of the signal, together with background estimates from data. The second approach uses a multivariate analysis technique to probe the compatibility with signal topology expected from electroweak top quark production. The combined measurement of the cross section is 83.6 +/- 29.8 (stat.+syst.) +/- 3.3 (lumi.) pb, consistent with the standard model expectation.
Top Polarization Measurement In Single Top Quark Production With The Atlas Detector
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Author : Xiaohu Sun
language : en
Publisher:
Release Date : 2013
Top Polarization Measurement In Single Top Quark Production With The Atlas Detector written by Xiaohu Sun and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
The top quark polarization in electroweak production for single top t-channel allows to test the structure of the Wtb vertex: the left-handed vector coupling of the Standard Model (SM) as well as the anomalous couplings including the right-handed vector, the left-handed tensor and the right-handed tensor couplings. The 4.7 fb-1 data recorded by the ATLAS detector at the LHC with the center of mass energy at 7 TeV in 2011 provides a chance to measure the top polarization. This thesis discusses the measurement of the top polarization by studying the polarized angular distributions in specific bases with t-channel single top events. In the beginning of the thesis, a theoretical context of the top quark production via the strong interaction and the electroweak interaction at the LHC is introduced. Then the detector, the reconstruction performances as well as the event selections with a single top t-channel event signature are described. To measure the top polarization, the unfolding and folding methods are constructed and tested with different configurations. In the end, the measured results are examined with the estimated uncertainties from the theory, the detector response and modeling as well as the statistics. This is the first measurement of the top polarization with the ATLAS detector. The results are compatible with the SM predictions and contribute signicantly to constrain the anomalous couplings in the Wtb vertex.
Measurement Of The Single Top Quark And Antiquark Production Cross Sections In The T Channel And Their Ratio In Proton Proton Collisions At S
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Author : Albert M. Sirunyan
language : en
Publisher:
Release Date : 2018
Measurement Of The Single Top Quark And Antiquark Production Cross Sections In The T Channel And Their Ratio In Proton Proton Collisions At S written by Albert M. Sirunyan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
Model Independent Measurement Of Boldsymbol T Channel Single Top Quark Production In Boldsymbol P Bar P Collisions At Boldsymbol Sqrt S
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Author :
language : en
Publisher:
Release Date : 2011
Model Independent Measurement Of Boldsymbol T Channel Single Top Quark Production In Boldsymbol P Bar P Collisions At Boldsymbol 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 2011 with categories.
We present a model-independent measurement of t-channel electroweak production of single top quarks in p{bar p} collisions at √s = 1.96 TeV. Using 5.4 fb−1 of integrated luminosity collected by the D0 detector at the Fermilab Tevatron Collider, and selecting events containing an isolated electron or muon, missing transverse energy and one or two jets originating from the fragmentation of b quarks, we measure a cross section [sigma](p{bar p} → tqb + X) = 2.90 ± 0.59 (stat + syst) pb for a top quark mass of 172.5 GeV. The probability of the background to fluctuate and produce a signal as large as the one observed is 1.6 x 10−8, corresponding to a significance of 5.5 standard deviations.
Measurement Of The Top Anti Top Quark Pair Production Cross Section In The Tau Jets Channel At Square Root Of S
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Author : Teeba Rashid
language : en
Publisher:
Release Date : 2013
Measurement Of The Top Anti Top Quark Pair Production Cross Section In The Tau Jets Channel At Square Root Of S written by Teeba Rashid and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Hadron interactions categories.
Measurement Of Top Quark Polarization In Top Antitop Lepton Jets Final States At
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Author :
language : en
Publisher:
Release Date : 2017
Measurement Of Top Quark Polarization In Top Antitop Lepton Jets Final States At written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
This thesis presents a measurement of the top quark polarization in the $t\overline{t}$ events produced in $p\overline{p}$ collisions at $\sqrt{s}=1.96$ TeV using data corresponding to 9.7 fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The final states used in the measurement contain one lepton and at least three jets. The polarization is measured using the angular distribution of leptons along three different axes: the beam axis, the helicity axis, and the transverse axis normal to the $t\overline{t}$ production plane. This is the first measurement of top quark polarization at the Tevatron Collider in lepton+jets final states, and the first measurement of transverse polarization in $t\overline{t}$ production. The polarization along the beam axis is combined with the previous result in the dilepton final states by the D0 experiment. The observed distributions are consistent with the Standard Model of nearly no polarization and no indication for beyond Standard Model physics is observed. The measurement offers legacy result from unique Tevatron Collider data and provides more information about the top quark production and decays, about the properties of the heaviest elementary particle.
Observation Of Single Top Quark Production
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Author :
language : en
Publisher:
Release Date : 2009
Observation Of Single Top Quark 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 2009 with categories.
The author reports on the observation of electroweak production of single top quarks in p{bar p} collisions at (square root)s = 1.96 Tev using 2.3 fb−1 of data collected with the D0 detector at the fermilab Tevatron Collider. Using events containing an isolated electron or muon, missing transverse energy, two, three or four jets, with one or two of them identified as originating from the fragmentation of a b quark, the measured cross section for the process p{bar p} --> tb + X, tqb + X is 3.94 ± 0.88 pb (for a top quark mass of 170 GeV). the probability to measure a cross section at this value or higher in the absence of signal is 2.5 x 10−7, corresponding to a 5.0 standard deviation significance. Using the same dataset, the measured cross sections for the t- and the s-channel processes when determined simultaneously with no assumption on their relative production rate are 3.14{sub -0.80}{sup +0.94} pb and 1.05 ± 0.81 pb respectively, consistent with standard model expectations. The measured t-channel cross section has a significance of 4.8 standard deviations, representing the first evidence for the production of an individual single top process to be detected.