Heavy quarks flavored scalar dark matter with a vector-like fermion portal

  • March 6, 2018, 2:30 pm
  • Wilson Hall, Curia II
  • Peiwen Wu, KIAS
  • Kiel

The absence of confirmed signal in dark matter (DM) direct detection (DD) may suggest weak interaction strengths between DM and the abundant constituents inside nucleon, i.e. gluons and valence light quarks. In this work we consider a real scalar dark matter $S$ interacting only with $SU(2)_L$ singlet Up-type quarks $U_i=u_R,c_R,t_R$ via a vector-like fermion $\psi$. The DM-nucleon scattering can proceed through both $h$-mediated Higgs portal (HP) and $\psi$-mediated vector-like portal (VLP), in which HP can receive sizable radiative corrections through the new fermions. We find that the constraints of XENON1T results are strong on $y_1$ from VLP scattering and on $y_3$ from its radiative contributions to HP scattering. Then we focus on DM-heavy quark interactions via $y_2,y_3$ in terms of DM-gluon scattering at loop level. We find that renormalization group equation (RGE) and heavy quark threshold effects are important. For the benchmarks $y_3=0.5, y_2=0.5, 1, 3$, combined results from $\Omega_{\rm DM} h^2\simeq 0.12$, XENON1T, Fermi-LAT, 13 TeV LHC data have almost excluded $m_S<m_t/2$ when only DM-$\{c,t\}$ interactions are considered. FCNC of top quark are usually below $10^{-9}$ after passing the other constraints, which are still safe from the current top quark width measurements.