Theoretical update ofB_s−bar B_smixing

Abstract

We update the theory predictions for the mass difference ∆M s , the width difference ∆Γ s and the CP asymmetry in flavour-specific decays, a s fs , for the B s −B s system. In particular we present a new expression for the element Γ s 12 of the decay matrix, which enters the predictions of ∆Γ s and a s fs. To this end we introduce a new operator basis, which reduces the troublesome sizes of the 1/m b and α s corrections and diminishes the hadronic uncertainty in ∆Γ s /∆M s considerably. Logarithms of the charm quark mass are summed to all orders. We find ∆Γ s /∆M s = (49.7 ± 9.4) • 10 −4 and ∆Γ s = (f Bs /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 Bs. The improved result for Γ s 12 also permits the extraction of the CP-violating B s −B s mixing phase from a s fs with better accuracy. We show how the measurements of ∆M s , ∆Γ s , a s fs , A mix CP (B s → J/ψφ) and other observables can be efficiently combined to constrain new physics. Applying our new formulae to data from the DØ experiment, we find a 2σ deviation of the B s −B s mixing phase from its Standard Model value. We also briefly update the theory predictions for the B d −B d system and find ∆Γ d /∆M d = 52.6 +11.5 −12.8 • 10 −4 and a d fs = −4.8

Model-independent constraints on ΔF= 2 operators and the scale of new physics

“…4 With respect to ref. [32], we find that the inclusion of A µµ SL has a weaker impact in reducing the ambiguity coming from several small differences in the analysis (theoretical assumptions on NP in A d SL , presence of NP in penguin contributions to A d,s SL , inclusion of the CDF measurement of A µµ SL , etc.). 5 We find that factorization gives δ1 ∼ 0 and δ2 ∼ π, resolving the ambiguity of the D0 untagged analysis in favour of φs ∼ 0.79 for positive ∆Γ, while ref.…”

“…We confirm that, with the same assumptions of ref. [32] on strong phases, 5 the deviation from zero of φ Bs slightly exceeds 2σ. Without assuming strong 3 To combine the CDF and DØ measurements, we have converted the value for A defined in ref.…”

“…5 We find that factorization gives δ1 ∼ 0 and δ2 ∼ π, resolving the ambiguity of the D0 untagged analysis in favour of φs ∼ 0.79 for positive ∆Γ, while ref. [32] uses δ1 ∼ π, δ2 ∼ 0 and φs ∼ −0.79. However, this sign difference in φs is compensated by the fact that φs as defined in ref.…”

“…However, this sign difference in φs is compensated by the fact that φs as defined in ref. [32] should be compared to −φs as measured by D0.…”

Studying ofBs0−B¯s0mixing andBs→KWang1, Xu2, Chang3 et al. 2011Phys. Rev. D383430View full textAdd to dashboardCite

“…More recently, the DØ collaboration has reported evidence for an anomalously large CP violation in the like-sign dimuon charge asymmetry in semileptonic Bhadron decays A b sl = (−9.57 ± 2.51(stat) ± 1.46(syst))×10 −3 [10], which differs by 3.2 standard deviations from the SM prediction A b,SM sl = (−2.3 +0. 5 −0.6 ) × 10 −4 [5,11]. Although the errors of the data are still large, these deviations from the SM could be attributed to the presence of non-SM flavor violationin the b → s, d non-leptonic decays.…”