Flavor phenomenology of the leptoquark singlet-triplet model
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Springer
Received: December 19, Revised: April 16, Accepted: April 27, Published: June 1,
2019 2020 2020 2020
Flavor phenomenology of the leptoquark singlet-triplet model
a
Paul Scherrer Institut, CH–5232 Villigen PSI, Switzerland b Physik-Institut, Universit¨ at Z¨ urich, Winterthurerstrasse 190, CH-8057 Z¨ urich, Switzerland c Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, CH-3012 Bern, Switzerland
E-mail: [email protected], [email protected], [email protected] Abstract: In recent years, experiments revealed intriguing hints for new physics (NP) in semi-leptonic B decays. Both in charged current processes, involving b → cτ ν transitions, and in the neutral currents b → s`+ `− , a preference for NP compared to the standard model (SM) of more that 3σ and 5σ was found, respectively. In addition, there is the long-standing tension between the theory prediction and the measurement of the anomalous magnetic moment (AMM) of the muon (aµ ) of more than 3σ. Since all these observables are related to the violation of lepton flavor universality (LFU), a common NP explanation seems not only plausible but is even desirable. In this context, leptoquarks (LQs) are especially promising since they give tree-level effects in semi-leptonic B decays, but only loop-suppressed effects in other flavor observables that agree well with their SM predictions. Furthermore, LQs can lead to a mt /mµ enhanced effect in aµ , allowing for an explanation even with (multi) TeV particles. However, a single scalar LQ representation cannot provide a common solution to all three anomalies. In this article we therefore consider a model in which we combine two scalar LQs: the SU(2)L singlet and the SU(2)L triplet. Within this model we compute all relevant 1-loop effects and perform a comprehensive phenomenological analysis, pointing out various interesting correlations among the observables. Furthermore, we identify benchmark points which are in fact able to explain all three anomalies (b → cτ ν, b → s`+ `− and aµ ), without violating bounds from other observables, and study their predictions for future measurements. Keywords: Beyond Standard Model, Heavy Quark Physics ArXiv ePrint: 1912.04224
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP06(2020)020
JHEP06(2020)020
Andreas Crivellin,a Dario M¨ ullera,b and Francesco Saturninoc
Contents 1 Introduction
1
2 Setup
4 5 6 10 10 12 13 15 17 18 19
4 Phenomenology 4.1 LHC bounds 4.2 b → cτ ν 4.3 b → cτ ν and b → s`+ `− 4.4 b → cτ ν, b → s`+ `− and aµ
20 20 21 25 25
5 Conclusions
26
A Loop functions and exact results A.1 Loop functions A.2 dd`` A.3 uuγ and EDM A.4 du`ν ¯s mixing A.5 ddνν and Bs − B
28 28 29 29 30 30 31 33 34 34
A.6 A.7 A.8 A.9
1
``γ, Z`` and Zνν W `ν τ → 3µ, τ → µe+ e− and µ → 3e τ → `ν ν¯ and µ → eν ν¯
Introduction
While the Large Hadron Collider (LHC) at CERN has not directly observed any particles beyond the ones of the SM (see e.g. refs. [1, 2] for an overvie
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