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Charming new B-physics

Jäger, Sebastian; Kirk, Matthew; Lenz, Alexander; Leslie, Kirsten

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Sebastian Jäger

Matthew Kirk

Alexander Lenz

Kirsten Leslie


We give a comprehensive account of the flavour physics of Beyond-Standard-Model (BSM) effects in b → cc¯¯cs transitions, considering the full set of 20 four-quark operators. We discuss the leading-order structure of their RG mixing with each other as well as the QCD-penguin, dipole, and FCNC semileptonic operators they necessarily mix with, providing compact expressions. We also provide the first complete results for BSM effects in the lifetime observables ∆Γs and τ (Bs)/τ(Bd), as well as for the semileptonic CP-asymmetry assl. From a global analysis, we obtain stringent constraints on 16 of the 20 BSM operators, including the 10 operators Qc′1…10 involving a right-handed strange quark. Focussing on CP-conserving new physics, the constraints correspond to NP scales of order 10 TeV in most cases, always dominated by exclusive and/or radiative B-decays via RGE mixing. For the remaining four operators, including the two Standard-Model (SM) ones, larger effects are experimentally allowed, as previously noted in [1]. We extend that paper’s scope to the CP-violating case, paying attention to the impact on the decay rate and time-dependent CP-violation in Bd → J/ψKS. Contrary to common lore, we show that quantifiable constraints arise for new physics in either of the two SM operators, with the uncertain non-perturbative matrix element of the colour-suppressed (or equivalently, colour-octet) operator determined from the data. For new physics in the coefficient Cc1, suppressed in the SM, we find (in addition to CP-conserving new physics) two perfectly viable, narrow bands of complex Wilson coefficients. Somewhat curiously, one of them contains a region where the fitted matrix element for the colour-suppressed operator is in agreement with naive factorization, contrarily to a widely held belief that large non- factorizable contributions to Bd → J/ψKS are implied by experimental data.


Jäger, S., Kirk, M., Lenz, A., & Leslie, K. (2020). Charming new B-physics. Journal of High Energy Physics, 2020(3), Article 122.

Journal Article Type Article
Acceptance Date Feb 25, 2020
Online Publication Date Mar 23, 2020
Publication Date Mar 31, 2020
Deposit Date Mar 24, 2020
Publicly Available Date Mar 24, 2020
Journal Journal of High Energy Physics
Print ISSN 1126-6708
Publisher Scuola Internazionale Superiore di Studi Avanzati (SISSA)
Peer Reviewed Peer Reviewed
Volume 2020
Issue 3
Article Number 122


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Copyright Statement
This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.

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