Speaker
Description
Dirac dark matter (DM) fermions $\chi$ can arise within the framework of Composite Higgs Models (CHMs). In such scenarios, the DM candidate is a composite neutral fermion emerging from a strongly-coupled sector. This strongly-coupled dynamics could also result in a light Higgs boson, which arises as a composite pseudo-Nambu-Goldstone boson (pNGB)—in direct analogy to pions in QCD.
We focus on an $E_6$-inspired Composite Higgs Model ($E_6$CHM), which can originate from $E_6$ supersymmetric Grand Unified Theories. In this model, the strongly-coupled sector is assumed to possess an approximate $SU(6) \subset E_6$ symmetry, which is spontaneously broken to an $SU(5)$ subgroup at a scale $f \simeq 5$–$10\,\text{TeV}$. Besides the Higgs doublet, $SU(6)$ breaking gives rise to a colored triplet $T$, which constitutes a distinctive feature of the model. The $E_6$CHM, with baryon number conservation and an additional $U(1)_E$ symmetry, can yield an $SU(5)$-singlet lightest Dirac composite particle (LDCP) $\chi$ with baryon charge $B = 1/3$ and a mass below $1\,\text{TeV}$. In this case, the LDCP is stable and can contribute to the dark matter density of the Universe.
Stringent constraints on the spin-independent dark matter-nucleon interaction limit the allowed LDCP density. For $f \sim 5\,\text{TeV}$ and an LDCP mass below $1\,\text{TeV}$, it can constitute only about $10–20\%$ of the total dark matter, while for $f \sim 10\,\text{TeV}$ the LDCP could account for the full observed DM density. We analyze the differential cross-section of LDCP-xenon nuclei scattering as a function of recoil energy, LDCP mass and magnetic moment within these constraints.
