Single decay-lepton angular distributions in polarized 𝑒+𝑒- → $toverline{t}$ and simple angular asymmetries as a measure of CP-violating top dipole couplings

Pramana

Saurabh D Rindani1¹ 

[1] Theory Group, Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, India$$

关键词: Top quark;    CP violation;    𝑒+𝑒- collider.;   

DOI  :  

学科分类：物理（综合）

来源: Indian Academy of Sciences

【 摘 要 】

In the presence of an electric dipole coupling of $toverline{t}$ to a photon, and an analogous `weak’ dipole coupling to the 𝑍, CP violation in the process 𝑒+𝑒- → $toverline{t}$ 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 either 𝑡 or $overline{t}$ decays leptonically, including $mathscr{O}(𝛼_{s})$ 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 the 𝑡 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 $sqrt{s}=500$ GeV with integrated luminosity 500 fb-1 and also at $sqrt{s} = 1000$ GeV with integrated luminosity 1000 fb-1 have been evaluated. The effect of longitudinal electron and/or positron beam polarizations has been included.

【 授权许可】

Unknown