Hunting for ALPs with lepton flavor violation

Abstract

We examine the low-energy signatures of axion-like particles (ALPs) in lepton flavor violating (LFV) processes. By using a dimension-5 effective Lagrangian, we compute the most general ALP contributions to LFV decays of leptons and mesons. The provided expressions are valid for any choice of ALP mass and couplings. We explore the complementarity of different processes, identifying specific patterns to be experimentally tested. Constraints on LFV couplings are derived from existing data and prospects for forthcoming experiments are also discussed. As a by-product, we revisit the possibility of a simultaneous explanation of the observed discrepancies in the muon and electron g − 2 through ALP interactions.

Probing μτ flavor-violating solutions for the muon g − 2 anomaly at Belle II

“…Since the dipole operator requires the chirality flipping, one-loop correction involving a mediator with the µτ flavor violating couplings is enhanced by a factor of m τ /m µ O (10). Such µτ flavor violating scenarios are discussed to explain the muon g − 2 anomaly in the context of the axion like particles (ALPs) [11,12], in the general two Higgs doublet model (G2HDM) [13][14][15][16][17][18][19][20][21][22][23][24][25][26], and in the Z models [27][28][29][30]. Figure 1 shows the representative diagram to induce the δa µ contribution with a µτ flavor violating mediator particle X, which is either a scalar or vector boson, and the µτ flavor violating nature of X introduces the internal τ -propagator at one-loop level.…”

“…We discuss a model with a new scalar mediator for the first. Following the ALP scenario, we introduce the interaction as follows [12]…”

“…In this setup, we have three independent parameters: the mass of the ALP particle m a , scalar coupling V l µτ , and pseudo scalar coupling a l µτ . The a µ contribution in this model is calculated as [12],…”

An explanation for the muon and electron g − 2 anomalies and dark matter

“…Interestingly, this measurement also shows a possible disagreement between the data and theory, with the measured value lower than the SM prediction by JHEP09(2020)119 about 2.4σ [13]. These tantalizing opposite deviations have invited many studies to explore suitable NP models [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29].…”

Detecting a μτ -philic Z′ boson via photon initiated processes at the LHC

“…2 The introduction of a new particle with lepton flavor violating µτ couplings is known to be able to explain the observed value of δa µ . Examples of such models are the axion like particle model [9,10], general two Higgs doublet model [11,12,13,14,15,16,17,18] and Z models [19,20,21,22]. In this paper, we consider a vector boson (Z ) which has sizable µτ flavor violating couplings.…”