Full one-loop QCD and electroweak corrections to sfermion pair production in γγ\gamma \gamma collisions

We have calculated the full one-loop electroweak (EW) and QCD corrections to the third generation scalar-fermion pair production processes $e^+e^- \to \gamma \gamma \to \tilde{f_i}\bar{\tilde{f_i}} (f=t,b,\tau)$ at an electron-positron linear collider(LC) in the minimal supersymmetric standard model (MSSM). We analyze the dependence of the radiative corrections on the parameters such as the colliding energy $\sqrt{\hat s}$ and the SUSY fundamental parameters $A_f$, $\tan \beta$, $\mu$, $M_{SUSY}$ and so forth. The numerical results show that the EW corrections to the squark-, stau-pair production processes and QCD corrections to the squark-pair production processes give substantial contributions in some parameter space. The EW relative corrections to squark-pair production processes can be comparable with QCD corrections at high energies. Therefore, these EW and QCD corrections cannot be neglected in precise measurement of sfermion pair productions via $\gamma\gamma$ collision at future linear colliders.Comment: to be appeared in Phys. Rev.

The SUSY EW-like corrections to top pair production in photon-photon collisions

We studied the one-loop contributions of the gaugino-Higgsino-sector to the process of top-pair production via $\gamma \gamma$ fusion at NLC in frame of the Minimal Supersymmetric Model(MSSM). We find that the corrections to $\gamma \gamma \to t\bar{t}$ and $e^+ e^- \to \gamma \gamma \to t\bar{t}$ are found to be significant and can approach to a few percent and one percent, respectively. Furthermore, the dependences of the corrections on the supersymmetric parameters are also investigated. The corrections are not sensitive to $M_{SU(2)}$ (or $|\mu|$) when $M_{SU(2)}~>>~|\mu|$ (or $|\mu|~>>~M_{SU(2)}$) and are weakly dependent on the $\tan{\beta}$ with $M_Q$ (or $|\mu|$) being large enough. But they are sensitive to the c.m.s. energy of the incoming photons.Comment: LaTex, 33 pages, 8 Eps figuer

Top quark pair production via polarized and unpolarized photons in Supersymmetric QCD

QCD corrections to top quark pair production via fusion of both polarized and unpolarized photons are calculated in Supersymmetric Model. The corrections are found to be sizable. The dependence of the corrections on the masses of the supersymmetric particles is also investigated. Furthermore, we studied CP asymmetry effects arising from the complex couplings in the MSSM. The CP violating parameter can reach $10^{-2}$ for favorable parameter values.Comment: 26 pages, LaTex, including 12 figures in 12 eps files. submitted to Phys. Rev.