, B – B̄ mixing , radiative penguin and rare ( semi ) leptonic decays

CKM03 WG2 Conveners' Report: V td and V ts , B– ¯ B mixing, radiative penguin and rare (semi)leptonic decays We introduce the Working Group 2 proceedings contributions from the 2nd workshop on the CKM Unitarity Triangle and note their connection to the proceedings of the first workshop. The topic of WG 2 was the determination of the CKM matrix elements V td and V ts from B-¯ B mixing, radiative penguin B → X s/d γ decays and rare (semi)leptonic decays such as B → X s ℓ + ℓ −. At the first CKM workshop, Working Group 2 focused on the present status of determining the Cabibbo-Kobayashi-Maskawa matrix elements V td and V ts from B meson oscillations [ 1]. On the experimental side, the status of the measurements of the B 0 d oscillation frequency ∆M d and the limits on the B 0 s oscillation frequency ∆M s were discussed. From the theoretical end, the focus was on the status and prospects of determining the non-perturbative parameters for B meson mixing from lattice QCD calculations. For the second CKM workshop at Durham, the experimental status of B meson mixing and the near term prospects for measuring B 0 S meson oscillations as well as the status of lattice QCD calculations were re-evaluated. However, the focus shifted towards methods of determining the CKM matrix elements V td and V ts from other sources in the next five years. In particular, the experimental prospects for measuring |V td /V ts | 2 from exclusive rare radiative decays B → K * γ and B → ργ and their theoretical limitations were explored. Furthermore, rare (semi)leptonic decays B → X s ℓ + ℓ − were discussed as summarized below. In the Standard Model, B 0 – ¯ B 0 mixing occurs via second order weak processes. The mass difference ∆M q between the two mass eigenstates B H and B L of the neutral B q meson (q = d, s) can be determined within the Standard Model by computing the electroweak box diagram, where the dominant contribution is through top quark exchange: ∆M q = G 2 F 6π 2 m B q (ˆ B B q F 2 B q) η B m 2 W S 0 (x t) |V tq | 2. (1) Here, ˆ B B q is the bag parameter of the B …