https://doi.org/10.1140/epjc/s10052-017-5270-2
Regular Article - Theoretical Physics
On flavourful Easter eggs for New Physics hunger and lepton flavour universality violation
1
INFN, Sezione di Roma Tre, Via della Vasca Navale 84, 00146, Rome, Italy
2
Dipartimento di Matematica e Fisica, Università di Roma Tre, Via della Vasca Navale 84, 00146, Rome, Italy
3
Dipartimento di Fisica, Università di Roma “La Sapienza”, P.le A. Moro 2, 00185, Rome, Italy
4
INFN, Sezione di Roma, P.le A. Moro 2, 00185, Rome, Italy
* e-mail: luca.silvestrini@roma1.infn.it
Received:
27
July
2017
Accepted:
1
October
2017
Published online:
17
October
2017
Within the standard approach of effective field theory of weak interactions for 
transitions, we look for possibly unexpected subtle New Physics effects, here dubbed “flavourful Easter eggs”. We perform a Bayesian global fit using the publicly available HEPfit package, taking into account state-of-the-art experimental information concerning these processes, including the suggestive measurements from LHCb of 
and 
, the latter available only very recently. We parametrise New Physics contributions to 
transitions in terms of shifts of Wilson coefficients of the electromagnetic dipole and semileptonic operators, assuming CP-conserving effects, but allowing in general for violation of lepton flavour universality. We show how optimistic/conservative hadronic estimates can impact quantitatively the size of New Physics extracted from the fit. With a conservative approach to hadronic uncertainties we find nonzero New Physics contributions to Wilson coefficients at the level of 
, depending on the model chosen. Furthermore, given the interplay between hadronic contributions and New Physics effects in the leptonic vector current, a scenario with nonstandard leptonic axial currents is comparable to the more widely advocated one with New Physics in the leptonic vector current.
© The Author(s), 2017
