LHC τ -rich tests of lepton-specific 2HDM for (g − 2) μ

Abstract

The lepton-sepcific (or type X) 2HDM (L2HDM) is an attractive new physics candidate explaining the muon g − 2 anomaly requiring a light CP-odd boson A and large tan β. This scenario leads to τ -rich signatures, such as 3τ , 4τ and 4τ + W/Z, which can be readily accessible at the LHC. We first study the whole L2HDM parameter space to identify allowed regions of extra Higgs boson masses as well as two couplings λ hAA and ξ l h which determine the 125 GeV Higgs boson decays h → τ + τ − and h → AA/AA * (τ + τ − ), respectively. This motivates us to set up two regions of interest: (A) m A m H ∼ m H ± , and (B) m A ∼ m H ± ∼ O(100)GeV m H , for which derive the current constraints by adopting the chargino-neutralino search at the LHC8, and then analyze the LHC14 prospects by implementing τ -tagging algorithm. A correlated study of the upcoming precision determination of the 125 GeV Higgs boson decay properties as well as the observation of multi-tau events at the next runs of LHC will be able to shed light on the L2HDM option for the muon g − 2.

Leptonic precision test of leptophilic two-Higgs-doublet model

“…Recall that we included the full HFAG data from the pure leptonic and semi-hadronic decays and obtained much weaker bounds than those in refs. [19,20]. In fact, the lepton universality data with tau decays show a 2σ deviation from the SM prediction and thus we obtain a large chi-square minimum, χ 2 min = 15.6, even for the L2HDM fit.…”

“…As we will see, the proper treatment of the lepton universality data in the charged current gives much weaker bounds than the previous ones [19,20] which used a partial data set.…”

“…Another test was carried out by HFAG in the processes of l → l νν , τ → νπ/K and π/K → µν [25]. The lepton universality data by HFAG need to be taken after projecting out a redundant degree in the ratios of the three lepton decay rates [20]. The precisions of these two data are at the level of 0.1% and thus sensitive enough to probe L2HDM corrections to the τ lepton vertices.…”

“…In the previous analyses [19,20], only partial data set from the lepton universality test by HFAG [25] was taken. In this work, we take the full data set properly including all the correlation effect.…”

“…It has been known that the discrepancy in the muon g − 2 can be accommodated through Barr-Zee two-loop corrections [16] if the extended Higgs sector allows a relatively light pseudoscalar with large Yukawa couplings to fermions. Recently, it was found that only the lepton-specific (or type X) 2HDM remains viable after considering all the updated experimental constraints [17][18][19][20][21][22].…”