Neutralino Dark Matter in a Class of Unified Theories
S. A. Abel, S. Sarkar, I. B. Whittingham
TL;DR
The paper investigates neutralino dark matter within a class of unified theories where electroweak breaking is seeded by a gauge singlet. By deriving analytic renormalization-group solutions, it expresses SUSY-breaking parameters in terms of $m_{1/2}$, $m_0$, and $A$, and computes the LSP composition and the relic density below the $m_W$ scale using a full annihilation-channel treatment and a compact analytic approximation. The analysis reveals that stable neutralinos can provide a significant contribution to the cosmic dark matter density over a broad portion of the viable parameter space, with robust predictions tied to the Higgs-singlet couplings $\\\lambda_{7}$ and \\lambda_{8}$. The work highlights regions in parameter space where the relic density is near unity and demonstrates the impact of signs and magnitudes of the soft terms, particularly the trilinear coupling $A$, on the cosmological outcome. Overall, the results support neutralino dark matter as a viable constituent in this minimally extended MSSM framework, offering analytic insight into the connection between high-scale SUSY-breaking parameters and cosmological relic abundance.
Abstract
The cosmological significance of the neutralino sector is studied for a class of models in which electroweak symmetry breaking is seeded by a gauge singlet. Extensive use is made of the renormalisation group equations to significantly reduce the parameter space, by deriving analytic expressions for all the supersymmetry-breaking couplings in terms of the universal gaugino mass $m_{1/2}$, the universal scalar mass $m_0$ and the coupling $A$. The composition of the LSP is determined exactly below the W mass, no approximations are made for sfermion masses, and all particle exchanges are considered in calculating the annihilation cross-section; the relic abundance is then obtained by an analytic approximation. We find that in these models, stable neutralinos may make a significant contribution to the dark matter in the universe.