https://doi.org/10.1140/epjc/s10052-017-5202-1
Regular Article - Theoretical Physics
Probing lepton-flavour universality with 
decays
Physik-Institut, Universität Zürich, Winterthurerstrasse 190, 8057, Zurich, Germany
* e-mail: buttazzo@physik.uzh.ch
Received:
23
June
2017
Accepted:
4
September
2017
Published online:
16
September
2017
We analyse the rare processes in view of the recent hints of violations of lepton-flavour universality (LFU) observed in B meson decays. If, as suggested by present data, the new interactions responsible for LFU violations couple mainly to the third generation of left-handed fermions, decays turn out to be particularly interesting: these are the only kaon decays with third-generation leptons (the 
neutrinos) in the final state. In order to relate B-physics anomalies and K decays we adopt an effective field theory approach, assuming that the new interactions satisfy an approximate 
flavour symmetry. In this framework we show that O(1) deviations from the Standard Model predictions in branching ratios, closely correlated to similar effects in 
, are naturally expected. The correlation of 
, 
, and the LFU violations in B decays would provide a very valuable tool to shed more light on this interesting phenomenon.
© The Author(s), 2017
