17 May/19
14:00 - 16:00 (Europe/Zurich)

Stable sexaquark: Dark Matter predictions, constraints and lab detection


A stable sexaquark is an appealing Dark Matter candidate. Simple statistical physics arguments, plus known QCD parameters (quark masses and QCD transition temperature), predicts the DM to baryon ratio after the QGP-hadron transition to be ~4.5 +- 1, in remarkable agreement with the observed value of  5.3 +- 0.1. This seminar will derive this relation and report on several related topics:

Constraints on mS and S-B-B breakup amplitude: Strongest limits come from deuterium lifetime for d -> S e+ nu from SNO.  The limits leave open an unexpectedly large mass range and the overlap expectations comfortably accommodate the DM relic density.  (Contrary to the intuition of Kolb and Turner, sexaquarks would not be dissociated in the low temperature hadronic phase, given reasonable estimates of their wave-function overlap with two baryons;  McDermott et al claim of exclusion via SN1987a also rely on unjustified assumptions, as will be mentioned.)

Primordial 7Li puzzle: The > 10-sigma deficit between the observed abundance of primordial 7Li relative to the prediction of standard BBN can be explained by sufficiently strongly resonant S-Be scattering, without changing good predictions for D and He.  Although highly-tuned, the required parameter space is compatible with current CMB and direct detection limits (GRF, R. Galvez and X. Xu 2019).  Interpreting limits from direct detection is non-trivial in the parameter regime associated with resonant scattering (X. Xu, GRF 2019).

New stringent constraints on Dark Matter interactions (more general than S -- includes millicharged): i) D. Neufeld, GRF and C. McKee, Ap J 2018: Hadronically interacting DM in the mass range 0.6-6 GeV forms a calculable atmosphere around the Earth, leading to novel constraints on S and millicharged models. ii)  D. Wadekar and GRF, 2019:  Millicharge and hadronic interactions of DM and gas is directly constrained at velocities ~10 km/s by the Leo T dwarf galaxy, and for velocities ~ 200 km/s by Milky Way clouds.

Sexaquark Detection in Lab Expts: A stable sexaquark is surprisingly elusive.  Experimental strategies for discovering the S will be enumerated.  The recent BABAR search in exclusive final states would need a factor ~10^4 higher statistics to be sensitive.