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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 $B_s\to J/ψϕ$, the counterpart of $B_d\to J/ψK_S$, providing a powerful tool to search for new-physics contributions to $B^0_s$--$\bar{B^0_s}$ mixing. Another benchmark mode is $B_s\to K^+K^-$, which complements $B_d\toπ^+π^-$, thereby allowing an extraction of the angle $γ$ 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 $γ$ with the help of $B_s\to D_s^{(\ast)\pm} K^\mp$ decays, which complement $B_d\to D^{(\ast)\pm}π^\mp$ modes. Since these strategies involve ``tree'' decays, the values of $γ$ thus extracted exhibit a small sensitivity on new physics.