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preprints:2006:ttp06-31 [2016/03/17 11:03] (current)
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 +====== TTP06-31 Theoretical update of Bs--Bs-bar mixing ====== 
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 +   <​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]] ​  | 
 +| |