WIMP dark matter, Higgs exchange and DAMA

Abstract

In the WIMP scenario, there is a one-to-one relation between the dark matter (DM) relic density and spin independent direct detection rate if both the annihilation of DM and its elastic scattering on nuclei go dominantly through Higgs exchange. In particular, for DM masses much smaller than the Higgs boson mass, the ratio of the relevant cross sections depends only on the DM mass. Assuming DM mass and direct detection rate within the ranges allowed by the recent DAMA collaboration results -taking account of the channelling effect on energy threshold and the null results of the other direct detection experiments- gives a definite range for the relic density. For scalar DM models, like the Higgs portal models or the inert doublet model, the relic density range turns out to be in agreement with WMAP. This scenario implies that the Higgs boson has a large branching ratio to pairs of DM particles, a prediction which might challenge its search at the LHC.

Figures (5)

• Figure 1: Higgs exchange diagrams for the DM annihilation (a) and scattering with a nucleon (b).
• Figure 2: Values of the ratio $R$ calculated from Eq. (\ref{['ratioS']}) for three values of $f$ to be compared with the area of $R$ values required to match at $2 \sigma$ level both WMAP relic density and direct detection constraints (i.e. DAMA, channelling effect included, and upper bounds from CDMS, Xenon, CoGent and Cresst, see Fig. 1 of Ref. Petriello:2008jj).
• Figure 3: For $m_h=120$ GeV, values of $m_S$ and $\lambda_L$ which lead to the WMAP result, $0.094< \Omega_{DM} h^2 < 0.129$ (solid black lines), and which match the direct detection constraints ( i.e. Fig.1 of Ref. Petriello:2008jj), for the central value $f=0.30$ as well as the values $f=0.14$ and $f=0.66$ .
• Figure 4: For $m_h=120$ GeV, $\log \sigma_p^{SI}$ (in pb$\equiv 10^{-36} cm^2$) as a function of $m_S$ and $\lambda_L$, versus $\Omega_{DM} h^2$ (black lines). For other values of $m_h$$\sigma_p^{SI}$ scales as $1/m_h^4$.
• Figure 5: For three example values of $m_S$ and $\mu_2$ (in GeV) taken from Fig. 3, flux of gamma rays from the galactic centre from the annihilation of a scalar DM consistent with DAMA, compared with EGRET data.