Importance of Loop Effects in Explaining the Accumulated Evidence for New Physics in B Decays with a Vector Leptoquark

Crivellin, Andreas (Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland) ; Greub, Christoph (Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, CH-3012 Bern, Switzerland) ; Saturnino, Francesco (Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, CH-3012 Bern, Switzerland) ; Müller, Dario (Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland)

11 January 2019

Abstract: In recent years experiments revealed intriguing hints for new physics (NP) in B decays involving bcτν and bs+ transitions at the 4σ and 5σ level, respectively. In addition, there are slight disagreements in buτν and bdμ+μ observables. While not significant on their own, they point in the same direction. Furthermore, Vus extracted from τ decays shows a slight tension (2.5σ) with its value determined from Cabibbo-Kobayashi-Maskawa unitarity, and an analysis of BELLE data found an excess in Bdτ+τ. Concerning NP explanations, the vector leptoquark SU(2) singlet is of special interest since it is the only single particle extension of the standard model which can (in principle) address all the anomalies described above. For this purpose, large couplings to τ leptons are necessary and loop effects, which we calculate herein, become important. Including them in our phenomenological analysis, we find that neither the tension in Vus nor the excess in Bdτ+τ can be fully explained without violating bounds from Kπνν¯. However, one can account for bcτν and buτν data finding intriguing correlations with Bqτ+τ and Kπνν¯. Furthermore, the explanation of bcτν predicts a positive shift in C7 and a negative one in C9, being nicely in agreement with the global fit to bs+ data. Finally, we point out that one can fully account for bcτν and bs+ without violating bounds from τϕμ, ϒτμ, or bsτμ processes.


Published in: Physical Review Letters 122 (2019)
Published by: APS
DOI: 10.1103/PhysRevLett.122.011805
arXiv: 1807.02068
License: CC-BY-4.0



Back to search

Fulltext:
Download fulltextXML Download fulltextPDF