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Constraining new physics in bcℓν transitions

  • Martin JungEmail author
  • David M. Straub
Open Access
Regular Article - Theoretical Physics
  • 12 Downloads

Abstract

B decays proceeding via bcℓν transitions with = e or μ are tree-level processes in the Standard Model. They are used to measure the CKM element Vcb, as such forming an important ingredient in the determination of e.g. the unitarity triangle; hence the question to which extent they can be affected by new physics contributions is important, specifically given the long-standing tension between Vcb determinations from inclusive and exclusive decays and the significant hints for lepton flavour universality violation in bcτ ν and bsℓℓ decays. We perform a comprehensive model-independent analysis of new physics in bcℓν, considering all combinations of scalar, vector and tensor interactions occuring in single-mediator scenarios. We include for the first time differential distributions of BDℓν angular observables for this purpose. We show that these are valuable in constraining non-standard interactions. Specifically, the zero-recoil endpoint of the BDℓν spectrum is extremely sensitive to scalar currents, while the maximum-recoil endpoint of the BDℓν spectrum with transversely polarized D is extremely sensitive to tensor currents. We also quantify the room for e-μ universality violation in bcℓν transitions, predicted by some models suggested to solve the bcτ ν anomalies, from a global fit to BDℓν and BDℓν for the first time. Specific new physics models, corresponding to all possible tree-level mediators, are also discussed. As a side effect, we present Vcb determinations from exclusive B decays, both with frequentist and Bayesian statistics, leading to compatible results. The entire numerical analysis is based on open source code, allowing it to be easily adapted once new data or new form factors become available.

Keywords

Beyond Standard Model Heavy Quark Physics 

Notes

Open Access

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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© The Author(s) 2019

Authors and Affiliations

  1. 1.Excellence Cluster UniverseGarchingGermany

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