Nonstandard Yukawa couplings and Higgs portal dark matter

Abstract

Abstract:We study the implications of non-standard Higgs Yukawa couplings to light quarks on Higgs-portal dark matter phenomenology. Saturating the present experimental bounds on up-quark, down-quark, or strange-quark Yukawa couplings, the predicted direct dark matter detection scattering rate can increase by up to four orders of magnitude. The effect on the dark matter annihilation cross-section, on the other hand, is subleading unless the dark matter is very light -a scenario that is already excluded by measurements of the Higgs invisible decay width. We investigate the expected size of corrections in multi-Higgsdoublet models with natural flavor conservation, the type-II two-Higgs-doublet model, the Giudice-Lebedev model of light quark masses, minimal flavor violation new physics models, Randall-Sundrum, and composite Higgs models. We find that an enhancement in the dark matter scattering rate of an order of magnitude is possible. Finally, we point out that a discovery of Higgs-portal dark matter could lead to interesting bounds on the light-quark Yukawa couplings.

Direct and indirect constraints on CP-violating Higgs-quark and Higgs-gluon interactions

“…The matrix elements are shown in table 4, where it must be stressed that these results apply only if a Peccei-Quinn (PQ) mechanism is invoked to remove the QCDθ term [62]. 6 The uncertainty is estimated to be significant, O(50%), for the light qCEDM contributions. More problematic is the dependence of the nucleon EDMs on the strange CEDM.…”

“…The one-body component is determined by the EDM of the constituent nucleons, d n and d p . A second contribution is due to 6 Note that in the presence of BSM sources of CP violation, the PQ mechanism relaxesθ to a finite valuē θ ind (induced theta-term), proportional to the coefficient of the new physics operator. Currently the effect of θ ind is taken into account within the QCD sum rule approach.…”

“…In addition, the nuclear Schiff moments depend on the constituent nucleon EDMs. As far as we are aware, this has only been calculated for d Hg [74], with the result α n = 1.9(1) and α p = 0.20 (6). We neglect possible contributions from CPV short-range nucleon-nucleon interactions but stress that this assumption is untested.…”

“…The impact of improved limits on d n , d Hg , or d e , can be simply obtained by rescaling the bounds in table 6. In table 8 we show constraints using expected future experimental sensitivities and central values of the matrix elements.…”

“…In fact, the Higgs couplings to gauge bosons and t, b quarks are known with an uncertainty of O(20 − 30%) [3], while the couplings of the Higgs to first and second generation fermions are much less constrained [4,5]. Clearly, better knowledge of the Higgs couplings will shed light on the nature of EWSB mechanism and will also have nontrivial implications for other aspects of Higgs phenomenology (such as Higgs portal Dark Matter [6]). Improving the sensitivity and constraints to the Higgs couplings is a major goal of Run 2 at the LHC and is becoming an increasingly important target for low-energy indirect probes.…”