The cost of an ALP solution to the neutral B-anomalies

Abstract

The neutral anomalies in B decays are analysed in terms of the tree-level exchange of an axion-like-particle (ALP), within the effective field theory framework. The complete two-dimensional parameter space for ALP couplings to electrons and muons is explored. The solutions to RK and to the two energy bins of $$ {R}_{K^{\ast }} $$ R K ∗ are confronted with the impact of ALP exchange on other observables (meson oscillations, leptonic and semileptonic decays of B mesons including searches for new resonances, astrophysical constraints), as well as with the theoretical domain of validity of the effective theory. Solutions based on ALPs heavier than B mesons, or lighter than twice the muon mass, are shown to be excluded. In contrast, the exchange of on-shell ALPs provides solutions to RK and/or $$ {R}_{K^{\ast }} $$ R K ∗ within 2σ sensitivity which are technically compatible with those constraints. Furthermore, a “golden ALP mass” is identified at the frontier between the two energy bin windows of $$ {R}_{K^{\ast }} $$ R K ∗ , which could simultaneously explain these two $$ {R}_{K^{\ast }} $$ R K ∗ anomalies together with RK; this calls for the convenience of different energy binning which would easily clear up this (unlikely) possibility. The impact of smearing on data analysis is also discussed. When loop effects are taken into account, the solutions found can be in addition compatible with the data on the g − 2 of the electron but not simultaneously with those on the g − 2 of the muon. Furthermore, loop effects may require fine-tunings of some coupling values.

Probing HNL‐ALP Couplings at Colliders

“…On the experimental side, the efforts pointed towards the construction of a consistent effective description of ALPs, [25][26][27][28][29][30][31][32] beyond the seminal study in Ref. [33], in order to investigate DOI: 10.1002/prop.202300027 possible signals at low-energy facilities, [34][35][36][37][38][39][40][41][42][43][44] colliders [25,[45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61] and in non-terrestrial environments. [62][63][64][65] Most of the analyses performed on collider data and from astrophysics deal with an on-shell ALP in the initial or final state of the considered processes, such as mono-Z, mono-W, and mono-Higgs searches or stellar cooling, and the associated bounds strongly depend on the ALP mass.…”

A Lesson from RττK(*)$R_{\tau \tau }^{K^{(\ast )}}$ and RννK(*)$R_{\nu \nu }^{K^{(\ast )}}$ at Belle II

“…Several beyond the standard model (BSM) scenarios have been discussed in the literature, [ 14–45 ] and it is quite challenging to formulate a scenario that would be consistent with both $$R_{D^{(\ast )}}$$ and $$R_{K^{(\ast )}}$$ and with a wealth of low energy flavor physics observables.…”

A Light Shed on Lepton Flavor Universality in B Decays

“…Also, there has been a fascinating set of anomalies looming in the past few years in various studies of different decay modes [11][12][13][14][15][16][17][18][19][20][21][22], see Refs. [23][24][25][26][27][28][29] for latest theoretical investigations. First-order decays of beauty (B) mesons to final τ lepton states have also been observed in BaBar [30,31], Belle [11,[32][33][34][35], and LHCb [10,19,21,[36][37][38][39][40] experiments.…”