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Top quark pair production by (polarized) gamma gamma collisions offers an interesting testing ground of the Standard Model and its extensions. In this Letter we present results for differential cross sections of top quark pair production…

High Energy Physics - Phenomenology · Physics 2009-11-11 A. Brandenburg , Z. G. Si

Top quark pair production at photon-photon colliders is studied in low scale quantum gravity scenario. From the dependence of the cross sections on the spin configuration of the top quark and anti-quark, we introduce a new observable, top…

High Energy Physics - Phenomenology · Physics 2009-10-31 Kang Young Lee , Seong Chan Park , H. S. Song , Jeonhyeon Song , Chaehyun Yu

Angular distributions of a mu+ and a b-quark resulting from the decay of a top quark produced at the e+e- linear collider with an unpolarized and a 100% longitudinally polarized electron beam are presented. The results of the standard model…

High Energy Physics - Phenomenology · Physics 2007-05-23 K. Cieckiewicz , K. Kolodziej

We discuss the degree of spin polarization of single top quarks produced via $Wg$ fusion process in $ep$ collision at TESLA+HERAp and CLIC+LHC energies $\sqrt{s}=1.6$ and 5.3 TeV. For $eb \to t \bar{\nu}$ subprocess we show that the top…

High Energy Physics - Phenomenology · Physics 2009-11-10 S. Atag , B. D. Sahin

We discuss the optimal spin bases for describing angular correlations in single top quark events at the Fermilab Tevatron. We define spin bases that exploit the fact that the top quarks are produced with 100% polarization along the momenta…

High Energy Physics - Phenomenology · Physics 2007-05-23 Gregory Mahlon

We investigate the feasibility of probing anomalous top-quark couplings of $Wtb$, $Z t \bar{t}$, and $\gamma t \bar{t}$ in terms of an effective Lagrangian with dimension-six operators at future $e^+e^-$ linear colliders with a c. m. energy…

High Energy Physics - Phenomenology · Physics 2009-11-07 Z. -H. Lin , T. Han , T. Huang , J. -X. Wang , X. Zhang

We propose techniques to observe the correlation of the spins of top quarks and antiquarks at the Tevatron and the LHC. Observation of the spin correlation would confirm that the top quark decays before its spin flips, and would place a…

High Energy Physics - Phenomenology · Physics 2008-11-26 T. Stelzer , S. Willenbrock

Top-antitop quark pairs produced at the Tevatron have a sizeable spin correlation. That correlation feeds into the angular distribution of the decay products, particularly in the dilepton channel. Including the expected correlation in an…

High Energy Physics - Phenomenology · Physics 2007-05-23 Gary R. Goldstein

We discuss top quark production and its subsequent decay at lepton colliders including both QCD corrections and anomalous gamma / Z - t t-bar couplings. The off-diagonal spin basis for the top and anti-top quarks is shown to be useful to…

High Energy Physics - Phenomenology · Physics 2009-10-31 Y. Kiyo , J. Kodaira , K. Morii , T. Nasuno , S. Parke

Spin correlations, using a generic spin basis, are investigated to leading order in QCD for top quark production at lepton colliders. Even though, these radiative corrections induce an anomalous gamma/Z magnetic moment for the top quarks…

High Energy Physics - Phenomenology · Physics 2010-02-03 Jiro Kodaira , Takashi Nasuno , Stephen Parke

Top-antitop pairs produced at hadron colliders are largely unpolarized, but their spins are highly correlated. The structure of these correlations varies significantly over top production phase space, allowing very detailed tests of the…

High Energy Physics - Phenomenology · Physics 2015-06-12 Matthew Baumgart , Brock Tweedie

We perform a comparative study of the reach of future $e^+e^-$ collider options for the scale of non-resonant new physics effects in the top quark sector, phrased in the language of higher-dimensional operators. Our focus is on the…

High Energy Physics - Phenomenology · Physics 2017-10-26 Christoph Englert , Michael Russell

We discuss the degree of spin polarization of single top quarks produced via $Wg$ fusion process in $ep$ collision at TESLA+HERAp and CLIC+LHC energies $\sqrt{s}=1.6$ and 5.3 TeV. A description on how to combine the cross sections of…

High Energy Physics - Phenomenology · Physics 2009-11-10 S. Atag , B. D. Sahin

Spin correlations of $e^{+}e^{-}$ pair productions of two colliding photons are investigated and explicit expressions for their corresponding probabilities are derived and found to be \textit{energy} (speed) dependent, for initially…

Quantum Physics · Physics 2015-03-17 N. Yongram

We analyze the spin correlations of the top quark pairs produced at Photon Linear Colliders. We employ the circular polarized photon beams and general spin basis for the top quark pair. We consider general spin bases to find a strong spin…

High Energy Physics - Phenomenology · Physics 2016-08-25 Michihiro Hori , Yuichiro Kiyo , Takashi Nasuno

We investigate the potential of $e\gamma$ collisions to probe anomalous $Wtb$ couplings via the polarized single top quark production process $e^{+} \gamma \to t \bar{b} \bar{\nu_{e}}$. We find 95% confidence level limits on the anomalous…

High Energy Physics - Phenomenology · Physics 2008-11-26 B. Sahin , I. Sahin

Full one-loop electroweak-corrections for an $e^-e^+\rightarrow t \bar{t}$ process associated with sequential $t\rightarrow b \mu\nu_\mu$ decay are discussed. At the one-loop level, the spin-polarization effects of the initial electron and…

High Energy Physics - Phenomenology · Physics 2018-06-25 Nhi M. U. Quach , Yoshimasa Kurihara , Khiem H. Phan , Takahiro Ueda

Top quark studies at future $e^+e^-$ colliders are considered. Two issues are discussed: {a --}Some results are presented on the decays of top quarks. Energy distributions of charged leptons and neutrinos in $t\to bW\to be^+\nu$ and jets in…

High Energy Physics - Phenomenology · Physics 2014-11-17 M. Jeżabek

In ongoing and upcoming hadron collider experiments, top quark physics will play an important role in testing the Standard Model and its possible extensions. In this work we present analytic results for the differential cross sections of…

High Energy Physics - Phenomenology · Physics 2011-05-05 W. Bernreuther , A. Brandenburg , Z. G. Si , P. Uwer

We study the spin properties of top quarks produced in collisions of polarized photons in the threshold region. For a relatively heavy top quark the influence of non-perturbative effects is small and its polarization parameters can be…

High Energy Physics - Phenomenology · Physics 2009-10-28 V. S. Fadin , V. A. Khoze , M. I. Kotsky