Abstract
Recently, we have witnessed two hints of physics beyond the standard model: a 3.3σ local excess ( {M}_{A_0} = 52 GeV) in the search for H0 → A0A0 → b overline{b} μ+μ− and a 4.2σ deviation from the SM prediction in the (g − 2)μ measurement. The first excess was found by the ATLAS collaboration using 139 fb−1 data at sqrt{s} = 13 TeV. The second deviation is a combination of the results from the Brookhaven E821 and the recently reported Fermilab E989 experiment. We attempt to explain these deviations in terms of a renormalizable simplified dark matter model. Inspired by the null signal result from dark matter (DM) direct detection, we interpret the possible new particle, A0, as a pseudoscalar mediator connecting DM and the standard model. On the other hand, a new vector-like muon lepton can explain these two excesses at the same time while contributing to the DM phenomenology.
Highlights
− 2)μ data amt e√assu=re1m3eTnetV. .TThheefisresctoenxdcedsesvwiaatsiofnouisnda combination of the results from the Brookhaven E821 and the recently reported Fermilab
Motivated by these observations and from theoretical considerations, we propose a renormalizable simplified dark matter (DM) model based on extending the SM with three SM singlet fields: a Dirac DM, a vectorlike muon lepton (VLML), and a pseudoscalar mediator
DM and at least one mediator are two indispensable ingredients inside these models. This opens up the possibility of discovering a mediator before finding the actual DM, helping us narrow down the regions worth exploring and the possible interactions between DM and the SM
Summary
We show our model configuration. We consider a SM singlet Dirac fermion χ as a DM candidate. After electroweak symmetry breaking (EWSB), the pseudoscalar A and the SM Higgs boson h mix with each other via the μA term. We will see that the LHC Higgs boson measurements can put a strong upper limit on sin 2α in this model. According to Z → l+l− precision measurements [62], an upper limit for the mixing between the left-handed muon and VLML is set at. [63, 64], we assign the upper bound sin α < 0.3 in our parameter scan.. For simplicity, we assume MA0/2 < Mχ < Mψ such that A0 → χχ and the annihilation χχ → ψ+ψ− are kinematically forbidden Taking all these facts into consideration, the scan range for the non-fixed parameters is given by the followings bounds. Where the star (∗) indicates that the parameter is scanned logarithmically in base 10
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