Higgs studies in polarizedγγcollisions

The study of an intermediate mass Higgs boson via the process $\gamma \gamma \to H\to b\overline{b}$ from an initially polarized $J_z=0\mathrm{}$ state has been advocated as an important feasible goal of a future photon linear collider. The crucial argument was the $m_b^2/s$ suppression of the background process $\gamma \gamma {(J}_z=0)\to b\overline{b}$. We critically review the contribution of the radiative background processes (in which the $m_b^2/s$ suppression is absent) to the quasi-two-jet-like events with at least one, but preferably two, tagged energetic $b$ jets. Within a complete study of the radiative processes, we find that a sizable background contribution can come from the helicity-violating $\gamma \gamma {(J}_z=0)\to b\overline{b}$ process accompanied by soft gluon emission. These latter radiative corrections contain a new type of double logarithmic (DL) terms. We clarify the physical nature of these novel DL corrections. Despite the fact that the one-loop DL terms are comparable or even larger than the Born term, fortunately we find that the calculation of the cross section in the two-loop approximation is sufficient for a reliable evaluation of the background to the Higgs signal.