We extend the theoretical prediction for the width difference ΔΓ_{q} in the mixing of neutral B mesons in the Standard Model to next-to-next-to-leading order in α_{s}. To this aim, we calculate three-loop diagrams with two |ΔB|=1 current-current operators analytically. In the matching between |ΔB|=1 and |ΔB|=2 effective theories, we regularize the infrared divergences dimensionally and take into account all relevant evanescent operators. Further elements of the calculation are the two-loop renormalization matrix Z_{ij} for the |ΔB|=2 operators and the O(α_{s}^{2}) corrections to the finite renormalization that ensures the 1/m_{b} suppression of the operator R_{0} at two-loop order. Our theoretical prediction reads ΔΓ_{s}/ΔM_{s}=(4.33±0.93)×10^{-3} if expressed in terms of the bottom mass in the MS[over ¯] scheme and ΔΓ_{s}/ΔM_{s}=(4.20±0.95)×10^{-3} for the use of the potential-subtracted mass. While the controversy on |V_{cb}| affects both ΔΓ_{s} and ΔM_{s}, the ratio ΔΓ_{s}/ΔM_{s} is not affected by the uncertainty in |V_{cb}|.
The energy-energy correlation (EEC) between two detectors in e^{+}e^{-} annihilation was computed analytically at leading order in QCD almost 40 years ago, and numerically at next-to-leading order (NLO) starting in the 1980s. We present the first analytical result for the EEC at NLO, which is remarkably simple, and facilitates analytical study of the perturbative structure of the EEC. We provide the expansion of the EEC in the collinear and back-to-back regions through next-to-leading power, information which should aid resummation in these regions.
