Probing CP-violating Higgs contributions in gamma-gamma -> f anti-f through fermion polarization

Abstract

We discuss the use of fermion polarization for studying neutral Higgs bosons at a photon collider. To this aim we construct polarization asymmetries which can isolate the contribution of a Higgs boson $\varphi$ in $\gamma \gamma \to f\bar{f}$, $f=\tau /t$, from that of the QED continuum. This can help in getting information on the $\gamma \gamma \varphi$ coupling in case $\varphi$ is a CP eigenstate. We also construct CP-violating asymmetries which can probe CP mixing in case $\varphi$ has indeterminate CP. Furthermore, we take the MSSM with CP violation as an example to demonstrate the potential of these asymmetries in a numerical analysis. We find that these asymmetries are sensitive to the presence of a Higgs boson as well as its CP properties over a wide range of MSSM parameters. In particular, the method suggested can cover the region where a light Higgs boson may have been missed by LEP due to CP violation in the Higgs sector, and may be missed as well at the LHC.

Comments: 14 pages, 14 figures, typeset in revtex4. Version which has appeared in Physical Review D; typos in two references corrected