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Languages : en
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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.
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Languages : en
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Book Description
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.
Author: Boris Lemmer
Publisher: Springer
ISBN: 3319189328
Category : Science
Languages : en
Pages : 246
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Book Description
This thesis introduces readers to the Standard Model, the top quark and its properties, before explaining the concept of spin correlation measurement. The first measurement of top quark spin correlations at the LHC in the lepton+jets decay channel is presented. As the heaviest elementary particle, the top quark plays an essential role in the Standard Model of elementary particle physics. In the case of top quarks being produced in pairs at hadron colliders, the Standard Model predicts their spins to be correlated. The degree of correlation depends on both the production mechanism and properties of the top quark. Any deviation from the Standard Model prediction can be an indicator for new physics phenomena. The thesis employs an advanced top quark reconstruction algorithm including dedicated identification of the up- and down-type quarks from the W boson decay.
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Languages : en
Pages : 7
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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.
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Languages : en
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We presented measurements of the top quark-antiquark (tt¯) spin correlations and the top quark polarization for tt¯ pairs produced in pp collisions at √s=8 TeV. The data correspond to an integrated luminosity of 19.5 fb-1 collected with the CMS detector at the LHC. The measurements are performed using events with two oppositely charged leptons (electrons or muons) and two or more jets, where at least one of the jets is identified as originating from a bottom quark. The spin correlations and polarization are measured from the angular distributions of the two selected leptons, both inclusively and differentially, with respect to the invariant mass, rapidity, and transverse momentum of the tt¯ system. Moreover, the measurements are unfolded to the parton level and found to be in agreement with predictions of the standard model. A search for new physics in the form of anomalous top quark chromo moments is performed. Lastly, no evidence of new physics is observed, and exclusion limits on the real part of the chromo-magnetic dipole moment and the imaginary part of the chromo-electric dipole moment are evaluated.
Author: Mario Campanelli
Publisher: Springer Science & Business Media
ISBN: 3540328416
Category : Science
Languages : en
Pages : 360
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Book Description
This book gathers the proceedings of The Hadron Collider Physics Symposia (HCP) 2005, and reviews the state-of-the-art in the key physics directions of experimental hadron collider research. Topics include QCD physics, precision electroweak physics, c-, b-, and t-quark physics, physics beyond the Standard Model, and heavy ion physics. The present volume serves as a reference for everyone working in the field of accelerator-based high-energy physics.
![Measurement of Tt Production Cross Section in Pp Collisions at [square Root] S PDF](https://books.google.com/books/content/images/frontcover/KRerbQi0wksC?fife=w80-h100)
Author: Harpreet Singh
Publisher:
ISBN:
Category : Collisions (Nuclear physics)
Languages : en
Pages : 418
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Book Description
Author:
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ISBN:
Category :
Languages : en
Pages : 249
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Book Description
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 ...
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Languages : en
Pages : 26
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Book Description
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.
![Spin Correlation in T[anti T] Production from P[anti P] Collisions At[radical] PDF](https://books.google.com/books/content/images/frontcover/Uk7QjwEACAAJ?fife=w80-h100)
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Category :
Languages : en
Pages :
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Book Description
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.
Author: Tomas Cechák
Publisher: Springer Science & Business Media
ISBN: 140204965X
Category : Science
Languages : en
Pages : 289
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Book Description
Recent results on the nature of low-, intermediate- and high-energy nuclear forces as well as on the internal structure of nucleons and atomic nuclei are presented. Prospects to find a new state of the nuclear matter at extreme conditions that existed in the early Universe and the utilisation of the nuclear energy are discussed.
