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https://www.ias.ac.in/article/fulltext/pram/061/01/0033-0050

Top quark; CP violation; e⁺e⁻ collider

In the presence of an electric dipole coupling of$$\overline {tt} $$ to a photon, and an analogous ‘weak’ dipole coupling to the Z, CP violation in the process e⁺e⁻ →$$\overline {tt} $$ results in modified polarization of the top and the anti-top. This polarization can be analyzed by studying the angular distributions of decay charged leptons when the top or anti-top decays leptonically. Analytic expressions are presented for these distributions when eithert or$$\overline t $$ decays leptonically, including$$\mathcal{O}$$(α_s) QCD corrections in the soft-gluon approximation. The angular distributions are insensitive to anomalous interactions in top decay. Two types of simple CP-violating polar-angle asymmetries and two azimuthal asymmetries, which do not need the full reconstruction of thet or$$\overline t $$, are studied. Independent 90% CL limits that may be obtained on the real and imaginary parts of the electric and weak dipole couplings at a linear collider operating at √ s = 500 GeV with integrated luminosity 500 fb⁻ and also at √s = 1000 GeV with integrated luminosity 1000 fb⁻ have been evaluated. The effect of longitudinal electron and/or positron beam polarizations has been included.

Saurabh D Rindani¹

1. Theory Group, Physical Research Laboratory, Navrangpura, Ahmedabad - 380 009, India

Published

July 2003

Manuscript received

30 December 2002

Manuscript revised

1 April 2003