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Impact of polarization observables and Bc→τν on new physics explanations of the b→cτν anomaly


Blanke, Monika; Crivellin, Andreas; de Boer, Stefan; Moscati, Marta; Nierste, Ulrich; Nišandžić, Ivan; Kitahara, Teppei (2019). Impact of polarization observables and Bc→τν on new physics explanations of the b→cτν anomaly. Physical review D, 99(7):075006.

Abstract

The combined analysis of the BABAR, Belle, and LHCb data on B→Dτν, B→D∗τν and Bc→J/Ψτν decay observables shows evidence of physics beyond the Standard Model (SM). In this article, we study all the one- and two-dimensional scenarios which can be generated by adding a single new particle to the SM. We put special emphasis on the model-discriminating power of FL(D∗) and of the τ polarizations, and especially on the constraint from the branching fraction BR(Bc→τν). We critically review this constraint and do not support the aggressive limit of BR(Bc→τν)<10% used in some analyses. While the impact of FL(D∗) is currently still limited, the BR(Bc→τν) constraint has a significant impact: depending on whether one uses a limit of 60%, 30% or 10%, the pull for new physics (NP) in scalar operators changes drastically. More specifically, for a conservative 60% limit a scenario with scalar operators gives the best fit to data, while for an aggressive 10% limit this scenario is strongly disfavored and the best fit is obtained in a scenario in which only a left-handed vector operator is generated. We find a sum rule for the branching ratios of B→Dτν, B→D∗τν and Λb→Λcτν which holds for any NP contribution to the Wilson coefficients. This sum rule entails an enhancement of BR(Λb→Λcτν) over its SM prediction by (24±6)% for the current R(D(*)) data.

Abstract

The combined analysis of the BABAR, Belle, and LHCb data on B→Dτν, B→D∗τν and Bc→J/Ψτν decay observables shows evidence of physics beyond the Standard Model (SM). In this article, we study all the one- and two-dimensional scenarios which can be generated by adding a single new particle to the SM. We put special emphasis on the model-discriminating power of FL(D∗) and of the τ polarizations, and especially on the constraint from the branching fraction BR(Bc→τν). We critically review this constraint and do not support the aggressive limit of BR(Bc→τν)<10% used in some analyses. While the impact of FL(D∗) is currently still limited, the BR(Bc→τν) constraint has a significant impact: depending on whether one uses a limit of 60%, 30% or 10%, the pull for new physics (NP) in scalar operators changes drastically. More specifically, for a conservative 60% limit a scenario with scalar operators gives the best fit to data, while for an aggressive 10% limit this scenario is strongly disfavored and the best fit is obtained in a scenario in which only a left-handed vector operator is generated. We find a sum rule for the branching ratios of B→Dτν, B→D∗τν and Λb→Λcτν which holds for any NP contribution to the Wilson coefficients. This sum rule entails an enhancement of BR(Λb→Λcτν) over its SM prediction by (24±6)% for the current R(D(*)) data.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Physics Institute
Dewey Decimal Classification:530 Physics
Uncontrolled Keywords:Physics and Astronomy (miscellaneous)
Language:English
Date:5 April 2019
Deposited On:12 Sep 2019 11:12
Last Modified:14 Feb 2020 08:28
Publisher:American Physical Society
ISSN:2470-0010
OA Status:Green
Publisher DOI:https://doi.org/10.1103/physrevd.99.075006
Project Information:
  • : FunderSNSF
  • : Grant IDPZ00P2_154834
  • : Project TitleFlavour Physics beyond the Standard Model

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