Low-energy signatures of the PS3 model: from B-physics anomalies to LFV

Abstract

The three-site Pati-Salam gauge model provides a consistent description for the hints of lepton-flavor non-universality observed in B decays, connecting the present pattern of "anomalies" to the origin of the Standard Model Yukawa couplings. We present here a detailed analysis of the model predictions for a series of low-energy observables, mainly in B and τ physics. The model is in good agreement with present data and predicts a well-defined pattern of non-standard effects in lowenergy observables that could allow us to test it in the near future. Particularly interesting are the predictions of large τ → µ Lepton Flavor Violating processes, such as τ → µγ, τ → 3µ, B → Kτ µ, and B s → τ µ. Also µ → 3e, µ → eγ, and K L → µe decays could be not far from the present exclusion bounds, although this conclusion is more model dependent.

Effective theory approach to new physics with flavour: general framework and a leptoquark example

“…(3.31). A sizeable scalar contribution to b → cτ −ν decays is known to improve the quality of fits [36,38,39,[49][50][51]. We require it to be comparable with the left-handed one, i.e.…”

“…As an illustration of the method, we consider in detail the minimally extended MFV scenario that accounts for the present flavour anomalies. Since one of the most promising setups to fit the anomalies is a U 1 leptoquark model [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40], one simply needs to consider the spurions which are associated with the fermion currents that the U 1 leptoquark is coupling to (see below). These spurions will be referred to as ∆ QL and ∆ DE in the following.…”

Unified SU(4) theory for the RD(*) and RKBalaji1, Schmidt2 2020Phys. Rev. D

“…We find that for small Y tµ we require large Y cτ and vice versa which is what we expect from inspecting Eq. (26). It should be noted that more complicated Yukawa textures for Y 4 and Y 3 are indeed permissible as mentioned earlier.…”

“…(30) and the C cbτ 4 V R constraint in Eq. (26), which can be easily plotted analytically along with the perturbative boundaries. Figure 3 shows the viable parameter ranges for the Yukawa couplings Y cτ , Y tµ , and y 3 as a function of the leptoquark mass mχ.…”

“…The possibility that some or even all of these deviations might be a harbinger of new physics has been entertained in the literature. In particular, several SU (4) models [19][20][21][22][23][24][25][26][27][28][29][30] have been proposed. Most of these models simultaneously explain the B physics anomalies via a massive vector leptoquark W ∼ (3, 1, 4/3) 1 , which is predicted by the breaking of SU (4) C → SU (3) C .…”