https://doi.org/10.1140/epjc/s10052-019-7210-9
Regular Article - Theoretical Physics
New Physics in 
confronts new data on lepton universality
1
INFN, Sezione di Roma Tre, Via della Vasca Navale 84, 00146, Rome, Italy
2
CFTP, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais 1, 1049-001, Lisbon, Portugal
3
Dept. de Física Quàntica i Astrofísica, Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona, Martí Franquès 1, 08028, Barcelona, Spain
4
INFN, Sezione di Roma, P.le A. Moro 2, 00185, Rome, Italy
5
DESY, Notkestraße 85, 22607, Hamburg, Germany
6
Institut für Physik, Humboldt-Universität zu Berlin, 12489, Berlin, Germany
7
Theoretical Physics Department, CERN, Geneva, Switzerland
8
Department of Physics and Astronomy, University of California, Irvine, CA, 92697-4575, USA
* e-mail: ayan.paul@desy.de
Received:
12
April
2019
Accepted:
8
August
2019
Published online:
27
August
2019
In light of the very recent updates on the 
and 
measurements from the LHCb and Belle collaborations, we systematically explore here imprints of New Physics in 
transitions using the language of effective field theories. We focus on effects that violate Lepton Flavour Universality both in the Weak Effective Theory and in the Standard Model Effective Field Theory. In the Weak Effective Theory we find a preference for scenarios with the simultaneous presence of two operators, a left-handed quark current with vector muon coupling and a right-handed quark current with axial muon coupling, irrespective of the treatment of hadronic uncertainties. In the Standard Model Effective Field Theory we select different scenarios according to the treatment of hadronic effects: while an aggressive estimate of hadronic uncertainties points to the simultaneous presence of two operators, one with left-handed quark and muon couplings and one with left-handed quark and right-handed muon couplings, a more conservative treatment of hadronic matrix elements leaves room for a broader set of scenarios, including the one involving only the purely left-handed operator with muon coupling.
© The Author(s), 2019
