Light Dark Matter and the Electroweak Phase Transition in the NMSSM

Abstract

We analyze the stability of the vacuum and the electroweak phase transition in the NMSSM close to the Peccei-Quinn symmetry limit. This limit contains light Dark Matter (DM) particles with a mass significantly smaller than the weak scale and also light CP-even and CP-odd Higgs bosons. Such light particles lead to a consistent relic density and facilitate a large spin-independent direct DM detection cross section, that may accommodate the recently reported signatures at the DAMA and CoGeNT experiments. Studying the one-loop effective potential at finite temperature, we show that when the lightest CP-even Higgs mass is of the order of a few GeV, the electroweak phase transition tends to become first order and strong. The inverse relationship between the direct-detection cross-section and the lightest CP-even Higgs mass implies that a cross-section of the order of 10$^{-41}$ cm$^2$ is correlated with a strong first order phase transition.

Figures (15)

• Figure 1: $F(m_s^2)$ plotted as a function of $m_s^2$ with $\phi_c=140$ GeV, for Parameter Set 1 in Table \ref{['tablemsAll']}. We see that it is only possible to have a strong first-order phase transition ($F(m_s^2) > 0$) for two regions of $m_s^2$. The solution for small $m_s^2$ is shown in more detail in the right plot $(b)$.
• Figure 2: Values of $\phi_c/T_c$ as a function of $m_s^2$ for Parameter Set 1 in Table \ref{['tablemsAll']}.
• Figure 3: Left:$m_{h_2}$ vs. $m_{h_1}$ for both EWSB (Green dots) and Baryogenesis (Red crosses), fixing the stop spectrum so that $m_{h_2}$ is in the 115--120 GeV range and scanning over all other parameters. Right: Same as left side but for $m_{a1}$ vs. $m_{\chi_1}$.
• Figure 4: $m_{h_2}$ vs. $m_{h_1}$ for both EWSB (Green dots) and Baryogenesis (Red crosses) for Parameter Set $a$ (left) and $b$ (right).
• Figure 5: Parametric plot of $m_s^2$ range for set of parameters given in Table \ref{['tablemsAll']} and the maximum allowed value approximated in the PQ-limit given in Eq. (\ref{['msrange']}). $\Delta\tilde{\lambda}_{\tilde{t}}$ was fixed such that $m_{h_2}$ is in the range 115--120 GeV.