Download or read book SUSY QCD Corrections to the Polarization and Spin Correlations of Top Quarks Produced in E e Collisions written by A. Brandenburg and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book SUSY QCD Corrections to the Polarization and Spin Correlations of Top Quarks Produced in E e Collisions written by Arnd Brandenburg and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book QCD Corrections to Top Quark Spin Correlations at Hadron Colliders written by Werner Bernreuther and published by . This book was released on 2000 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurements of Tt u00AF Spin Correlations and Top Quark Polarization Using Dilepton Final States in Pp Collisions at S written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Measurements of t bar t Spin Correlations and Top quark Polarization Using Dilepton Final States in Pp Collisions at sqrt s written by and published by . This book was released on 2013 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurements of T t Spin Correlations and Top Quark Polarization Using Dilepton Final States in Pp Collisions at s written by CMS Collaboration and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Next to Leading Order QCD Corrections to Top Quark Spin Correlations at Hadron Colliders written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Higgs Effects in the Polarization of Top Quarks written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Top quarks produced in high-energy collisions should exhibit a parity-conserving spin polarization normal to the production plane which can be measured by the asymmetry in their leptonic decays. A portion of this effect, which can be calculated in perturbation theory, is attributable to the quark's QCD interactions. In addition, there is a component of the polarization due to the Yukawa coupling (g[sub Y] [congruent] m[sub T]/(250 GeV)) of the top quark with the Higgs sector. We can demonstrate the interplay of QCD and Yukawa forces in the polarization for e[sup +]e[sup [minus]] [yields] 4 T[bar T]. Assuming M[sub H]> 2M[sub T] and that the Higgs particle is not discovered before the top quark, measurement of top quark polarization in e[sup +]e[sup [minus]] or hadron-hadron collisions can be used to specify an approximate mass for the Higgs and guide direct searches.
Download or read book Polarization in Heavy Quark Decays written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis I concentrate on the angular correlations in top quark decays and their next--to--leading order (NLO) QCD corrections. I also discuss the leading--order (LO) angular correlations in unpolarized and polarized hyperon decays. In the first part of the thesis I calculate the angular correlation between the top quark spin and the momentum of decay products in the rest frame decay of a polarized top quark into a charged Higgs boson and a bottom quark in Two-Higgs-Doublet-Models: $t(uparrow)rightarrow b+H^{+}$. The decay rate in this process is split into an angular independent part (unpolarized) and an angular dependent part (polar correlation). I provide closed form formulae for the ${mathcal O}(alpha_{s})$ radiative corrections to the unpolarized and the polar correlation functions for $m_{b}neq 0$ and $m_{b}=0$. The results for the unpolarized rate agree with the existing results in the literature. The results for the polarized correlations are new. I found that, for certain values of $tanbeta$, the ${mathcal O}(alpha_s)$ radiative corrections to the unpolarized, polarized rates, and the asymmetry parameter can become quite large. In the second part I concentrate on the semileptonic rest frame decay of a polarized top quark into a bottom quark and a lepton pair: $t(uparrow) to X_b + ell^+ + nu_ell$. I analyze the angular correlations between the top quark spin and the momenta of the decay products in two different helicity coordinate systems: system 1a with the $z$--axis along the charged lepton momentum, and system 3a with the $z$--axis along the neutrino momentum. The decay rate then splits into an angular independent part (unpolarized), a polar angle dependent part (polar correlation) and an azimuthal angle dependent part (azimuthal correlation). I present closed form expressions for the ${mathcal O}(alpha_{s})$ radiative corrections to the unpolarized part and the polar and azimuthal correlations in system 1a and 3a for $m_{b}neq 0$ and $m_{b}=0$. Fo.
Download or read book Spin Correlations in Tt Events from Pp Collisions written by Boris Lemmer and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2730 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Top Pair Production in E e and gamma gamma Processes written by and published by . This book was released on 1998 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: We analyze spin correlations between top quark and anti-top quark produced at polarized e e− and [gamma][gamma] colliders. We consider a generic spin basis to find a strong spin correlation. Optimal spin decompositions for top quark pair are presented for ee− and [gamma][gamma] colliders. We show the cross- section in these bases and discuss the characteristics of results.
Download or read book Top Quark Spin Correlations Theory written by and published by . This book was released on 2012 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark decay width (G{sub F}m{sub t}3 ≈ 1 GeV) is much larger than the QCD hadronization scale (?{sub QCD} ≈ 0.1 GeV) and much larger than the spin decorrelation scale (?{sub QCD}2/m{sub t} ≈ 0.1 MeV). Therefore, spin correlations in top quark pair production are reflected in angular correlations of the decay products, see [1] and [2].
Download or read book Why E superscript e superscript T Tbar is Different written by and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Unlike other examples of fermion pair production in ee− collisions, we show that top-quark pairs are produced in an essentially unique spin configuration in polarized ee− colliders at all energies. Since the directions of the electroweak decay products of polarized top-quarks are strongly correlated to the top-quark spin axis, this unique spin configuration leads to a distinctive topology for top-quark pair events which can be used to constrain anomalous couplings to the top-quark. A significant interference effect between the longitudinal and transverse W-bosons in the decay of polarized top-quarks is also discussed.
Download or read book Top Quark Spin Correlations and Leptonic Forward backward Asymmetries at written by Timothy Head and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is the heaviest fundamental particle. Its correspondingly short lifetime implies that it will decay before top flavoured hadrons can form. This provides an opportunity to study the properties of a quark without the effects of hadronisation, which is unique in the standard model. Using data recorded by the D0 experiment at the Fermilab Tevatron collider, and corresponding to \unit[5.4]{fb {-1}} of proton-antiproton collisions two analyses of the production and decay mechanism of top quarks are presented in this thesis. In the standard model the directions of the spin of top quarks produced in pairs by the strong interaction are expected to be correlated. In the first analysis, the strength of the correlation is extracted from the angles of the two leptons in the top quark and antiquark rest frames, yielding a correlation strength C=0.10\pm0.45. This is in agreement with the NLO QCD prediction within two standard deviations, but also in agreement with the no correlation hypothesis. In the second analysis, forward-backward asymmetries in top quark-antiquark production are measured using the charged leptons from top quark decays. We find that the angular distributions of \ell {\mathrm{-}} relative to antiprotons and \ell {+} relative to protons are in agreement with each other. Combining the two distributions and correcting for detector acceptance we obtain the forward-backward asymmetry \al=\left(5.8\pm5.1\mathrm{(stat)}\pm1.3\mathrm{(syst)}\right)\%, compared to the standard model prediction of \al\mathrm{(predicted)}=\left(4.7\pm0.1\right)\%.
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 Spin Correlation Between Top and Antitop Quarks Produced in p bar p Collisions at sqrt s written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the correlation between the spins of t and tbar quarks produced in proton-antiproton collisions at the Tevatron Collider at a center-of-mass energy of 1.96 TeV. We apply a matrix element technique to dilepton and single-lepton+jets final states in data accumulated with the D0 detector that correspond to an integrated luminosity of 9.7 fb$^{-1}$. The measured value of the correlation coefficient in the off-diagonal basis, $O_{off} = 0.89 \pm 0.22$ (stat + syst), is in agreement with the standard model prediction, and represents evidence for a top-antitop quark spin correlation difference from zero at a level of 4.2 standard deviations.
