CP Violation and New Physics in $B_s$ Decays

The $B_s$-meson system is a key element in the $B$-physics programme of hadron colliders, offering various avenues to explore CP violation and to search for new physics. One of the most prominent decays is $B_sto J/psiphi$, the counterpart of $B_dto J/psi K_S$, providing a powerful tool to search for new-physics contributions to $B^0_s$--$bar{B^0_s}$ mixing. Another benchmark mode is $B_sto K^+K^-$, which complements $B_dtopi^+pi^-$, thereby allowing an extraction of the angle $gamma$ of the unitarity triangle that is sensitive to new-physics effects in the QCD penguin sector. Finally, we discuss new methods to constrain and determine $gamma$ with the help of $B_sto D_s^{(ast)pm} K^mp$ decays, which complement $B_dto D^{(ast)pm}pi^mp$ modes. Since these strategies involve ``tree'' decays, the values of $gamma$ thus extracted exhibit a small sensitivity on new physics.