The width difference in \bbm at order α_s and beyond

2022/02/24 by Gerlach, Marvin, Nierste, Ulrich, Shtabovenko, Vladyslav +1
#FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph)

paper · doi:10.48550/arxiv.2202.12305

Abstract

We complete the calculation of the element Γ₁₂^q of the decay matrix in B_q-B_q mixing, q=d,s, to order α_s in the leading power of the Heavy Quark Expansion. To this end we compute one- and two-loop contributions involving two four-quark penguin operators. Furthermore, we present two-loop QCD corrections involving a chromomagnetic operator and either a current-current or four-quark penguin operator. Such contributions are of order α_s², i.e. next-to-next-to-leading-order. We also present one-loop and two-loop results involving two chromomagnetic operators which are formally of next-to-next-to-leading and next-to-next-to-next-to-leading-order, respectively. With our new corrections we obtain the Standard-Model prediction ΔΓ_s/ΔM_s= (5.20± 0.69)⋅ 10^-3 if Γ₁₂^s is expressed in terms of the \rm MS b-quark mass, while we find ΔΓ_s/ΔM_s= (4.70± 0.96)⋅ 10^-3 instead for the use of the pole mass.

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