Solution for Lithium Problem from Supersymmetric Standard Model

Abstract

AbstractA review on a non-standard Big-Bang nucleosynthesis (BBN) scenario within the minimal supersymmetric standard model is given to explain our solution for the \(^7\)Li and \(^6\)Li problems. There is a well-known discrepancy between the predicted abundance in the standard BBN and the observed one. In the solution, the lightest slepton mainly consisting of stau, a supersymmetric partner of the tau lepton, plays a crucial role. It is a long-lived charged particle and becomes long-lived when it degenerates in mass with the lightest supersymmetric particle. According to coannihilation mechanism, then the lightest supersymmetric particle will be a good candidate for dark matter. The long-lived “stau” forms a bound state with a nucleus and provides non-standard nuclear reactions. Among them, the internal conversion process is most important to destruct \(^{7}\)Be and \(^7\)Li, leading a solution to the \(^7\)Li problem. Note that, in addition, the catalyzed process which is another exotic process caused by a bound state of stau and \(^{4}\)He can solve the \(^6\)Li problem. In general, the lifetime of particles is determined by the degeneracy of the masses and also controlled by the strength of lepton flavor violation. If stau is a long-lived particle, then it can contribute to the exotic process for nucleosynthesis. The internal conversion process must be effective while other exotic processes must be ineffective. For these requests, the parameter space of stau is strictly constrained, however. Therefore, we need to study carefully the stau-\(^{4}\)He bound state for solving the \(^6\)Li problem. The scenario of the long-lived stau simultaneously and successfully fits the abundances of light elements (D, T, \(^{3}\)He, \(^{4}\)He, \(^6\)Li, and \(^7\)Li) and the neutralino dark matter to the experimental data. Consequently, we can determine the parameter space of the stau and the neutralino with excellent accuracy. We address that, in this parameter space, the mechanism of Sommerfeld enhancement plays a crucial role, and then, as a result, the dark matter signal becomes large enough to be observed by the current sensitivity of indirect experiments.KeywordsBig BangNucleosynthesisEarly universeLi problemStandard model of particle physicsSupersymmetryDark matter