Theoretical predictions for the direct detection of neutralino dark matter in the NMSSM

TL;DR

This work analyzes direct detection prospects for neutralino dark matter within the NMSSM, addressing how the extended Higgs and neutralino sectors, constrained by LEP data, affect the neutralino-nucleon cross section $\sigma_{\tilde{\chi}^0_1-p}$. It shows that, unlike in the MSSM, the NMSSM can accommodate very light, mostly singlet Higgs states and a singlino-Higgsino LSP, which together enhance scalar interactions via Higgs exchange and yield cross sections up to about $10^{-7}$ pb under current constraints. The study emphasizes that the presence of light singlet-dominated Higgses allows sizable cross sections while evading collider limits, due to reduced couplings to SM states. Although the analysis avoids relic-density constraints for now, it points to an important NMSSM-specific mechanism to obtain detectable DM signals, with caveats related to other flavor and cosmological bounds to be explored in future work.

Abstract

We analyse the direct detection of neutralino dark matter in the framework of the Next-to-Minimal Supersymmetric Standard Model. After performing a detailed analysis of the parameter space, taking into account all the available constraints from LEPII, we compute the neutralino-nucleon cross section, and compare the results with the sensitivity of detectors. We find that sizable values for the detection cross section, within the reach of dark matter detectors, are attainable in this framework. For example, neutralino-proton cross sections compatible with the sensitivity of present experiments can be obtained due to the exchange of very light Higgses with $m_{h_1^0}\lsim 70$ GeV. Such Higgses have a significant singlet composition, thus escaping detection and being in agreement with accelerator data. The lightest neutralino in these cases exhibits a large singlino-Higgsino composition, and a mass in the range $50\lsim m_{\tildeχ_1^0}\lsim 100$ GeV.

Figures (23)

• Figure 1: Feynman diagrams contributing to the neutralino-nucleon scalar cross section: (a) squark exchange and (b) scalar Higgs exchange.
• Figure 2: ($\lambda , \kappa$) parameter space for $\tan\beta=3$, $A_\lambda=200$ GeV, $A_\kappa=-50$ GeV and $\mu=110$ GeV. In both cases, the ruled area represents points which are excluded due to the occurrence of a Landau pole. The grided area is excluded because of the appearance of tachyons. The grey area is associated to those points that do not satisfy the LEP constraints or where (at least) the LEP bound on direct neutralino production is violated. Dotted lines in the experimentally accepted region represent contours of scalar neutralino-proton cross section $\sigma_{\tilde{\chi}^0_1-p}$. In (a), from top to bottom, solid lines indicate different values of lightest Higgs scalar mass, $m_{h_1^0}=114,\,75,\,25$ GeV, and dashed lines separate the regions where the lightest scalar Higgs has a singlet composition given by ${S_{13}^{\,2}}=0.1,\,0.9$. In (b), from top to bottom, solid lines are associated with different values of the lightest neutralino mass, $m_{\tilde{\chi}^0_1}=100,\,75,\,50$ GeV, while dot-dashed lines reflect the singlino composition of the lightest neutralino, $N_{15}^2=0.1,\,0.9$.
• Figure 3: Scatter plot of the scalar neutralino-nucleon cross section, $\sigma_{\tilde{\chi}^0_1-p}$, as a function of (a) the neutralino mass, $m_{\tilde{\chi}_1^0}$, and (b) the lightest scalar Higgs mass, $m_{h_1^0}$, for $A_\lambda=200$ GeV, $\mu=110$ GeV, $A_\kappa=-50$ GeV, and $\tan\beta=3$. Black dots correspond to points fulfilling all the experimental constraints, whereas grey dots represent those excluded. In (a) the sensitivities of present and projected experiments are also depicted with solid and dashed lines, respectively. The large (small) area bounded by dotted lines is allowed by the DAMA experiment when astrophysical uncertainties are (are not) taken into account.
• Figure 4: $(\lambda,\kappa)$ parameter space with the corresponding constraints and neutralino-nucleon cross section as a function of the lightest neutralino mass for the case $A_\lambda=200$ GeV, $A_\kappa=-200$ GeV, $\mu=110$ GeV and $\tan\beta=3$. In the $(\lambda,\kappa)$ plane the mass and composition of the lightest scalar Higgs, the composition of the lightest neutralino (only the line with $N_{15}^2=0.1$), and the predictions for $\sigma_{\tilde{\chi}^0_1-p}$ are represented with the same line conventions as in Fig. \ref{['++-a']}, and the new ruled area (vertical lines) is excluded due to the occurrence of unphysical minima. The colour convention for the plot $\sigma_{\tilde{\chi}^0_1-p}$ versus $m_{\tilde{\chi}_1^0}$ is as in Fig. \ref{['++-crossa']}.
• Figure 5: The same as in Fig. \ref{['++-ka']} but for the cases $A_\lambda=200$ GeV, $A_\kappa=-50$ GeV, $\mu=110$ GeV, and $\tan\beta=2,\,5,\,10$, from top to bottom. In the case with $\tan\beta=2$, only the lines with $m_{h_1^0}=75,\,25$ GeV are represented, since $m_{h_1^0}\hbox{$\;<$$\sim\;$}110$ GeV.