Lepton flavor violation in Higgs boson decays under the rare tau decay results

Abstract

We study lepton flavor violation (LFV) associated with tau leptons in the framework of the two Higgs doublet model, in which LFV couplings are introduced as a deviation from Model II Yukawa interaction. Parameters of the model are constrained from experimental results and also from requirements of theoretical consistencies such as vacuum stability and perturbative unitarity. Current data for rare tau decays provide substantial upper limits on the LFV Yukawa couplings in the large tan β region (tan β 30), which are comparable with predictions in fundamental theories.Here tan β is the ratio of vacuum expectation values of the two Higgs doublets. We show that a search for the LFV decays φ 0 → τ ± µ ∓ (τ ± e ∓ ) of neutral Higgs bosons (φ 0 = h, H and A) at future collider experiments can be useful to further constrain the LFV couplings especially in the relatively small tan β region (tan β 30), where rare tau decay data cannot give any strong limit.

$$\mu \rightarrow e \gamma $$ μ → e γ in the 2HDM: an exercise in EFT

“…The one-and two-loop contributions to μ → eγ of the neutral Higgses were calculated by Chang et al [5], and their result, in the decoupling limit, is given in Eqs. (20), (19), (21), (23) and (25).…”

“…The decay μ → eγ has been extensively studied in the 2HDM [3,[15][16][17][18][19][20][21][22][23][24][25][26][27], particularily in connection [29][30][31][32][33][34][35][36][37] with the recent LHC [28,38] excess in h → τ ± μ ∓ . Chang, Hou and Keung [5] (CHK) calculate the contributions to μ → eγ of neutral Higgs bosons with flavour-changing couplings.…”

“…(20) and ( Then the quark loop of the tensor operator is closed to mix it to the dipole if SU(2) was imposed:…”

Explaining the CMS Higgs flavor-violating decay excess

“…Furthermore, this ansatz can be understood as a minimal correction beyond the Type-II 2HDM, with the only departure in the τ µ coupling [34]. Finally, the Higgs couplings to gauge bosons are fully dictated by the gauge symmetry.…”

Model-discriminating power of lepton flavor violatingτdecays

“…Many scenarios of physics beyond the SM predict rates for LFV processes of charged leptons within the reach of present and future experiments. Some examples are: the SM with additional right-handed heavy Majorana neutrinos or with left-handed and right-handed neutral singlets [2], supersymmetric models [3][4][5][6][7][8][9][10][11][12][13][14], left-right symmetric models [15,16], technicolor models with non-universal Z exchange [17], multi-Higgs doublet models [18][19][20][21][22][23], leptoquark models [24][25][26], models with heavy vector-like leptons [27][28][29][30], and, the Littlest Higgs model with T-parity [31,32]. It is obvious then that if LFV transitions among charged leptons are observed at some point, it will be a challenging task to disentangle all the possible NP candidates.…”