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Can the Differences in the Determinations of Vub and Vcb Be Explained by New Physics?

Andreas Crivellin and Stefan Pokorski
Phys. Rev. Lett. 114, 011802 – Published 7 January 2015

Abstract

The precise determination of the Cabibbo-Kobayashi-Maskawa elements Vcb and Vub is crucial for any new physics analysis in the flavor sector. Their values can be determined from several tree-level decays: Vcb can be extracted from BDν and BD*ν while Vub can be obtained from Bπν, Bρν, and Bτν. In addition, for both Vcb and Vub an inclusive determination is available. There is a long lasting discrepancy between the inclusive and exclusive determinations which recently even increased for Vcb above the 3σ level. In this Letter we study the possible effect of new physics on the inclusive and exclusive determination of Vcb and Vub in a model independent way. We find that there is only one operator corresponding to a modified W coupling which can achieve this. However, respecting SU(2) gauge invariance at the high scale this would lead to very large violations of the Z to bb¯ coupling not compatible with experiment. Therefore, we conclude that a new physics explanation of the difference between the inclusive and exclusive determination of Vcb and Vub is currently ruled out. Therefore, the discrepancies must be due to underestimated uncertainties in the theoretical and/or the experimental analysis.

  • Figure
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  • Received 19 July 2014

DOI:https://doi.org/10.1103/PhysRevLett.114.011802

This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

© 2015 Published by American Physical Society

Authors & Affiliations

Andreas Crivellin

  • CERN Theory Division, CH-1211 Geneva 23, Switzerland

Stefan Pokorski

  • Institute of Theoretical Physics, Physics Department, University of Warsaw, Hoża 69, 00-681 Warsaw, Poland

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Issue

Vol. 114, Iss. 1 — 9 January 2015

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