Model of vector leptoquarks in view of the B -physics anomalies

By L. Calibbi, Andreas Crivellin, Tianjun Li. Physical Review D, 2017

248 citations recorded by the source corpus.

Lepton number as a fourth color is an intriguing theoretical idea which is combined with a possible left-right symmetry within the famous Pati-Salam (PS) model. In the conventional PS model, a spontaneous breaking of the PS gauge group down to the SM one can only take place at very high scales (above the PeV scale) due to the stringent bounds from $K_L\to\mu e$ and $K\to\pi\mu e$ induced by the resulting vector leptoquarks. In this paper, we show that these constraints can be avoided once additional vector-like fermions are introduced and thus a breaking at the TeV scale is possible. We consider the flavor phenomenology of this model in the context of the intriguing hints for new physics in semileptonic $B$ decays. The necessary violation of lepton flavor universality is induced by mixing SM and vector-like fermions. Concerning $R(D)$ and $R(D^*)$ we find that sizable effects are possible while respecting the bounds from other flavor observables but predicting a large enhancement of $B_s\to\tau^+\tau^-$. Furthermore, also in $b\to s\ell^+\ell^-$ transitions the observed deviations from the SM predictions (including $R(K)$ and $R(K^*)$) can be explained with natural values for the free parameters of the model without any fine-tuning, predicting sizable decay rates for $b\to s\tau\mu$. Finally, the anomaly in anomalous magnetic moment of the muon can be accounted for by a loop-contribution involving the vector leptoquark and vector-like leptons.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/bcb2fb150ce48d591d8fb4f964c0354c8194b3c6

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Citations in the corpus

Revisiting the vector leptoquark explanation of the B-physics anomalies (2019, background): “Given the success of some EFT approaches and simplified models in describing available data, the attention has shifted recently towards the development of more complete (and more complex) models with a consistent ultraviolet (UV) behavior (see in particular [28–42]).”
Maximal flavour violation: a Cabibbo mechanism for leptoquarks (2018, background): “[38, 50], generically predict too large neutrino masses.”
B-decay discrepancies after Moriond 2019 (2019, background): “tic estimate of the size of the eects. 9Such contributions are, however, model-dependent. For example, they will be quite dierent in models with additional vector-like fermions running in the loops [89,90], as shown explicitly in Ref. [101]. 16 0:200 0:175 0:150 0:125 0:100 0:075 0:050 0:025 0:000 g”
Review of lepton universality tests in B decays (2018, background): “ntributions (correlated with scalar contributions). Leptoquark models are also bounded by high-pT constraints [151], but the bounds can be avoided by assuming large couplings to the second generation [176,206,207]. The extension of this discussion to more general frameworks is possible and leaves ro”