Download or read book 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 published by . This book was released on 2016 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Evidence for Spin Correlation in t bar t Production written by and published by . This book was released on 2011 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Evidence for Spin Correlation in Tt Production written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Measurement of Spin Correlations in Top Anti Top Events from Pp Collisions at Sqrt s written by and published by . This book was released on 2014 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 ...

Download or read book Measurement of the Ttbar Production Cross Section in the All jets Final State in Pp Collisions at sqrt s written by and published by . This book was released on 2015 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: The cross section for tt production in the all-jets final state is measured in pp collisions at a centre-of-mass energy of 8 TeV at the LHC with the CMS detector, in data corresponding to an integrated luminosity of 18.4 fb-1. The inclusive cross section is found to be 275.6 ±6.1 (stat) ± 37.8 (syst) ± 7.2 (lumi) pb. The normalized differential cross sections are measured as a function of the top quark transverse momenta, pT, and compared to predictions from quantum chromodynamics. The results are reported at detector, parton, and particle levels. In all cases, the measured top quark pT spectra are significantly softer than theoretical predictions.

Download or read book Measurement of Jet Activity in Top Quark Events Using the E mu Final State with Two B tagged Jets in Pp Collisions at sqrt s written by and published by . This book was released on 2016 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measurement of gamma 1S Spin Alignment with the CMS Detector written by Matthew Scott Rudolph and published by . This book was released on 2011 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a measurement of the spin alignment of prompt [gamma](1S) mesons produced in proton-proton collisions at [square root of]s = 7 TeV at the Large Hadron Collider using the Compact Muon Solenoid detector. Approximately 1 fb-1 of data taken during the year 2011 is analyzed. The decay to two muons is used to identify these decays, and the angular distribution of the two muons is measured. The method is designed to measure the tensor polarization with minimal assumptions about the production mechanism involved. The decay distribution of the muons is measured in the full two dimensional angular space as a function of the transverse momentum and rapidity of the [gamma], and the analysis is repeated in the helicity and Collins-Soper frames. A frame invariant quantity is calculated in each frame from the measured decay distribution and compared. The final result disfavors large polarization, but suggests the presence of some anisotropy in the decay

Download or read book 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 published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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'