New Cosmological and Experimental Constraints on the CMSSM

TL;DR

The paper investigates how recent cosmological measurements of dark matter density and collider/flavor constraints restrict the CMSSM parameter space, focusing on the neutralino relic density $\Omega_\chi h^2$ and its interplay with LEP bounds, $BR(B\rightarrow X_s \gamma)$, and the muon anomalous magnetic moment. Using a modified ISASUGRA framework with careful RG running, radiative electroweak symmetry breaking, and exact annihilation calculations, the authors map the viable regions in the $(m_{1/2},m_0)$ plane for representative $\tan\beta$ values. They find that for $\tan\beta \lesssim 40$ the allowed spectra are confined to narrow bands, while at $\tan\beta \sim 50$ a broad $A$-resonance shifts viable spectra toward TeV-scale masses, with the resonance position sensitive to $m_t$ and $m_b$. The study highlights significant theoretical uncertainties in Higgs-mass calculations and the reliability of spectrum codes at very large $\tan\beta$, underscoring the need for improved computations in this regime.

Abstract

We analyze the implications of several recent cosmological and experimental measurements for the mass spectra of the Constrained MSSM (CMSSM). We compute the relic abundance of the neutralino and compare the new cosmologically expected and excluded mass ranges with those ruled out by the final LEP bounds on the lightest chargino and Higgs masses, with those excluded by current experimental values of $\br(B\to X_s γ)$, and with those favored by the recent measurement of the anomalous magnetic moment of the muon. We find that for $tanβ\lsim 45$ there remains relatively little room for the mass spectra to be consistent with the interplay of the several constraints. On the other hand, at larger values of $tanβ\$ the decreasing mass of the pseudoscalar Higgs gives rise to a wide resonance in the neutralino WIMP pair-annihilation, whose position depends on the ratio of top and bottom quark masses. As a consequence, the cosmologically expected regions consistent with other constraints often grow significantly and generally shift towards superpartner masses in the $\tev$ range.

Figures (1)

• Figure 1: The same as in Fig. \ref{['fig:tb50']} but for different values of the top and bottom masses as indicated in respective windows. In window d) the white area around the green 'island' of the expected range $0.1<\Omega_\chi h^2<0.2$ corresponds to $\Omega_\chi h^2<0.1$. The white strips between the narrow green bands and the excluded (light orange) regions of $\Omega_\chi h^2>0.3$ correspond to $0.2<\Omega_\chi h^2<0.3$, and so does the white 'hole' inside the green 'island' in window d).