title: Constraining the phase of Bs-Bs mixing.
abstract: New physics contributions to Bs-Bs mixing can be parametrized by the size (rs2) and the phase (2thetas) of the total mixing amplitude relative to the standard model amplitude. The phase has so far been unconstrained. We first use the D0 measurement of the semileptonic CP asymmetry ASL to obtain the first constraint on the semileptonic CP asymmetry in Bs decays, ASLs=-0.008+/-0.011. Then we combine recent measurements by the CDF and D0 Collaborations--the mass difference (DeltaMs), the width difference (DeltaGammas), and ASL;s--to constrain 2thetas. The errors on DeltaGammas and ASL;s should still be reduced to have a sensitive probe of the phase, yet the central values are such that the regions around 2thetas approximately 3pi/2 and, in particular, 2thetas approximately pi/2, are disfavored.
authors.affiliation: Department of Physics, Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel.
authors.forename: Yuval
authors.initials: Y
authors.lastname: Grossman
authors.forename: Yosef
authors.initials: Y
authors.lastname: Nir
authors.forename: Guy
authors.initials: G
authors.lastname: Raz