Many new physics models that explain the intriguing anomalies in the b-quark flavor sector are severely constrained by B s mixing, for which the Standard Model prediction and experiment agreed well until recently. The most recent Flavour Lattice Averaging Group (FLAG) average of lattice results for the nonperturbative matrix elements points, however, in the direction of a small discrepancy in this observable Cabibbo-Kobayashi-Maskawa (CKM). Using up-to-date inputs from standard sources such as PDG, FLAG and one of the two leading CKM fitting groups to determine ΔM SM s , we find a severe reduction of the allowed parameter space of Z 0 and leptoquark models explaining the B anomalies. Remarkably, in the former case the upper bound on the Z 0 mass approaches dangerously close to the energy scales already probed by the LHC. We finally identify some model-building directions in order to alleviate the tension with B s mixing.
Abstract:The hadronic matrix elements of dimension-six ∆F = 0, 2 operators are crucial inputs for the theory predictions of mixing observables and lifetime ratios in the B and D system. We determine them using HQET sum rules for three-point correlators. The results of the required three-loop computation of the correlators and the one-loop computation of the QCD-HQET matching are given in analytic form. For mixing matrix elements we find very good agreement with recent lattice results and comparable theoretical uncertainties. For lifetime matrix elements we present the first ever determination in the D meson sector and the first determination of ∆B = 0 matrix elements with uncertainties under control -superseeding preliminary lattice studies stemming from 2001 and earlier. With our stateof-the-art determination of the bag parameters we predict:−0.8 and the mixing-observables in the B s and B d system, in good agreement with the most recent experimental averages.
This paper reports an updated measurement of the standard model CP violation parameter sin 2 using the CDF Detector at Fermilab. The entire run I data sample of 110 pb Ϫ1 of proton-antiproton collisions at ͱs ϭ1.8 TeV is used to identify a signal sample of ϳ400 B→J/ K S 0 events, where J/→ ϩ Ϫ and K S 0 → ϩ Ϫ. The flavor of the neutral B meson is identified at the time of production by combining information from three tagging algorithms: a same-side tag, a jet-charge tag, and a soft-lepton tag. A maximum likelihood fitting method is used to determine sin 2ϭ0.79 Ϫ0.44 ϩ0.41 (statϩsyst). This value of sin 2 is consistent with the standard model prediction, based upon existing measurements, of a large positive CP-violating asymmetry in this decay mode.
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