Probing Anomalous Top-Quark Couplings Induced by Dim.6 Operators at Photon Colliders

Abstract

Possible anomalous top-quark couplings induced by SU(2) x U(1) gauge-invariant dimension-6 effective operators were studied in the process of t t-bar productions and decays at polarized gamma gamma colliders. Two CP-violating asymmetries, a linear-polarization asymmetry and a circular-polarization asymmetry, were computed including both non-standard [t t-bar gamma] and [gamma gamma H] couplings. An optimal-observable analysis for the process gamma gamma --> t t-bar --> l^{+-} ... was performed in order to estimate the precision for determination of all relevant non-standard couplings, including the anomalous tbW coupling.

Figures (2)

• Figure 1: $C\!P$-violating linear-polarization asymmetry $A_{lin}$ as a function of the Higgs-boson mass computed for $\sqrt{s_{e\bar{e}}}=500$ GeV, ${\mit\Lambda}=1$ TeV, $y_0=\tilde{y}_0=4.828$, $\alpha_{\gamma 2}=\alpha_{h 2}=0.1$, $P_e=P_{\bar{e}}=1$, $P_t=P_{\tilde{t}}=P_{\gamma}=P_{\tilde{\gamma}}= 1/\sqrt{2}$ and $\chi\equiv \varphi-\tilde{\varphi}=\pm\pi/4$.
• Figure 2: $C\!P$-violating circular-polarization asymmetry $A_{cir}$ as a function of the Higgs-boson mass computed for $\sqrt{s_{e\bar{e}}}=500$ GeV, ${\mit\Lambda}=1$ TeV, $y_0=\tilde{y}_0=4.828$, $\alpha_{h 2}=0.1$, and $P_e=P_{\bar{e}}= P_{\gamma}=P_{\tilde{\gamma}}=\pm 1$.