====== TTP06-31 Theoretical update of Bs--Bs-bar mixing ======
 
 
   <hidden TTP06-31  Theoretical update of Bs--Bs-bar mixing > We update the theory predictions for the mass difference Delta m_s, the
 width difference Delta Gamma_s and the CP asymmetry in flavour-specific
 decays, a_fs^s, for the Bs-Bs-bar mixing system. In particular we
 present a new expression for the element Gamma_{12}^s of the decay
 matrix, which enters the predictions of Delta Gamma_s and a_fs^s.  To
 this end we introduce a new operator basis, which reduces the
 troublesome sizes of the 1/m_b and alpha_s corrections and diminishes
 the hadronic uncertainty in Delta Gamma_s/Delta m_s considerably.
 Logarithms of the charm quark mass are summed to all orders.  We find
 Delta m_s = (49.7 =/- 9.4 ) * 10^{-4} and Delta Gamma_s =(f_{B_s}/240
 MeV)^2 [(0.105 +/- 0.016) B + (0.024 +/- 0.004) B_S~' - 0.027 +/- 0.015]
 ps^{-1} in terms of the bag parameters B, B_S~' in the NDR scheme and
 the decay constant f_{B_s}. The improved result for Gamma_{12}^s also
 permits the extraction of the CP-violating Bs-Bs-bar mixing phase from
 a_fs^s with better accuracy.  We show how the measurements of Delta M_s,
 Delta Gamma_s, a_fs^s, A_CP^mix(B_s\to J/\psi \phi) and other
 observables can be efficiently combined to constrain new
 physics. Applying our new formulae to data from the D0 experiment, we
 find a 2-sigma deviation of the Bs-Bs-bar mixing phase from its Standard
 Model value. We also briefly update the theory predictions for the
 Bd-Bd-bar mixing system and find Delta Gamma_d/Delta m_d =
 (52.6+11.5/-12.8) * 10^{-4} and a_fs^d =(-4.8 +1.0/-1.2}) *10^{-4} in
 the Standard Model.
 </hidden>
|**Alexander Lenz and Ulrich Nierste**  | 
|**  JHEP   0706 072 2007  **  |
| {{preprints:2006:ttp06-31.pdf|PDF}} {{preprints:2006:ttp06-31.ps|PostScript}} [[http://arxiv.org/abs/hep-ph/0612167|arXiv]]   |
| |