Testing the 2HDM explanation of the muon g – 2 anomaly at the LHC

Abstract

The discrepancy between the measured value and the Standard Model prediction for the muon anomalous magnetic moment is one of the important issues in the particle physics. In this paper, we consider a two Higgs doublet model (2HDM) where the extra Higgs doublet couples to muon and tau in lepton flavor violating (LFV) way and the one-loop correction involving the scalars largely contributes to the muon anomalous magnetic moment. The couplings should be sizable to explain the discrepancy, so that the extra Higgs bosons would dominantly decay into µτ LFV modes, which makes the model testable at the LHC through multilepton signatures even though they are produced via the electroweak interaction. We discuss the current status and the future prospect for the extra Higgs searches at the LHC, and demonstrate the reconstruction of the mass spectrum using the multi-lepton events. arXiv:1907.09845v1 [hep-ph] 23 Jul 2019 * There are other possible setups to explain this anomaly: a muon specific 2HDM [10], a lepton specific (Type-X) 2HDM [11-14], a aligned 2HDM [15-17] and a U (1)-symmetric 2HDM [18].

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

“…Recently, the importance of the photon initiated processes for such a Z searches is shown, and a large part of the model parameter favored by the anomaly would be covered at the high-luminosity (HL)-LHC [30]. Moreover, if the other neutral scalars exist as in G2HDMs, the current LHC data for 150 fb −1 would already cover the large parameter space through the electroweak production processes in the same µ ± µ ± τ ∓ τ ∓ modes [25].…”

“…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.…”

Higgs Lepton Flavor Violating Decays in Two Higgs Doublet Models

“…A Higgs doublet with µτ LFV couplings can also address the long-standing muon g − 2 anomaly. This was studied in relation to the LFV decay h → τ µ in [9,19,34,47,53,70,76,130], and very recently in [134,135]. It could also be linked to the popular b → s [31,48] or b → c [42] anomalies observed in B-meson decays or be a crucial ingredient for lepton-flavored electroweak baryogenesis [80].…”

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.…”