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Longitudinal quark polarization in \(e^+e^- \to t\overline{t}\) and chromoelectric and chromomagnetic dipole couplings of the top quark

  • S.D. Rindani
  • M.M. Tung
Theoretical physics
  • 23 Downloads

Abstract.

The effect of anomalous chromomagnetic (\(\mu\)) and chromoelectric couplings (d) of the gluon to the top quark is considered in \(e^+e^- \to t\overline{t}\), with unpolarized and longitudinally polarized electron beams. The total cross section, as well as t and \(\overline{t}\) polarizations, are calculated to order \(\alpha_s\) in the presence of the anomalous couplings. One of the two linear combinations of t and \(\overline{t}\) polarizations is CP even, while the other is CP odd. The limits that could be obtained at a typical future linear collider with an integrated luminosity of 50 fb\(^{-1}\) and a total c.m. energy of 500 GeV on the most sensitive CP-even combination of anomalous couplings, are estimated as \(-3 < {\rm Re}(\mu) < 2\), for \({\rm Im}(\mu)=0=d\), and \(\sqrt{{\rm Im}(\mu)^2 + \vert d \vert ^2} < 2.25\), for \({\rm Re}(\mu)=0\). There is an improvement by roughly a factor of 2 at 1000 GeV. On the other hand, from the CP-odd combination, we derive the possible complementary bounds as \(-3.6 < {\rm Im} (\mu^* d) < 3.6\), for \({\rm Im} (d) = 0\), and \(-10 < {\rm Im} (d) < 10\), for \({\rm Im} (\mu^* d) = 0\), for a c.m. energy of 500 GeV. The corresponding limit for 1000 GeV is almost an order of magnitude better for \({\rm Im} (\mu^* d)\), though somewhat worse for \({\rm Im} (d)\). Results for the c.m. energies 500 GeV and 1000 GeV, if combined, would yield independent limits on the two CP-violating parameters of \(-0.8 < {\rm Im} (\mu^* d) < 0.8\) and \(-11 <{\rm Im} (d) < 11\).

Keywords

Linear Combination Electron Beam Total Cross Section Dipole Coupling Linear Collider 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • S.D. Rindani
    • 1
  • M.M. Tung
    • 2
  1. 1.Theory Group, Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, India IN
  2. 2.Institute for Theoretical Physics, State University of New York, Stony Brook, NY 11794-3840, USA US

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