Leptoquark model to explain the B -physics anomalies, RK and R

Abstract

We show that a model with a scalar leptoquark of hypercharge Y = 1/6 which includes the light right-handed neutrinos, can successfully describe both of the B-physics anomalies, R expWe discuss the corresponding low energy effective theory and, after using the known experimental data as constraints, we show that the model is viable and that it offers several predictions which can be tested experimentally.

Simultaneous explanation of R(D (∗)) and b→sμ + μ −: the last scalar leptoquarks standing

“…These large third generation couplings lead again to stringent bounds from direct LHC searches [65] and electroweak precision observables [66]. In principle, these constraints can be avoided with right-handed couplings [59] (including possibly right-handed neutrinos [16]). However, in such solutions no interference with the SM appears and very large couplings, close to non-perturbativity, are required.…”

“…W gauge bosons [11,14,53,54] 3. Leptoquarks [9,10,12,13,15,16,19,20,42,[55][56][57][58][59][60] Models with charged Higgses lead to (too) large effects in the total B c lifetime [61] and, depending on the coupling structure, can also be disfavored by the q 2 distribution [62][63][64]. Interestingly, if the couplings of the charged Higgs are chosen in such a way that they are compatible with the measured q 2 distribution, these models are ruled out by direct searches [65].…”

“…Therefore, it is well motivated to search for a simultaneous explanation of these two anomalies [8][9][10][11][12][13][14][15][16][17][18][19][20]. Furthermore, since a e agrees with the SM prediction, also a µ can be considered as a LFUV quantity and one can address it together with R(D ( * ) ) and/or b → sµ + µ − [13,[21][22][23].…”

On the importance of electroweak corrections for B anomalies

“…Moreover, there are four types of lepto-quark (LQ) mediators giving rise to O (1) lq and O (3) lq at the tree-level [80,[94][95][96][97][98][99][100][101]. Two have spin one, U µ and U a µ , and two have spin zero, S and S a .…”

A leptoquark model to accommodate R K exp < R K SM and R K ∗ exp < R K ∗

“…If confirmed, these results would exclude the model of refs. [26][27][28], for example, in which < 0. That induced problems elsewhere in phenomenology, ultimately making that particular model phenomenologically unviable, see discussion in ref.…”