Effect of exotic long-lived sub-strongly interacting massive particles in big bang nucleosynthesis and a new solution to the Li problem

Abstract

The plateau of 7 Li abundance as a function of the iron abundance by spec- troscopic observations of metal-poor halo stars (MPHSs) indicates its primordial origin. The observed abundance levels are about a factor of three smaller than the primordial 7 Li abundance predicted in the standard Big Bang Nucleosynthesis (BBN) model. This discrepancy might originate from exotic particle and nuclear processes operating in BBN epoch. Some particle models include heavy (m 1 GeV) long-lived colored particles which would be confined inside exotic heavy hadrons, i.e., strongly interacting massive particles (SIMPs). We have found reactions which destroy 7 Be and 7 Li during BBN in the scenario of BBN catalyzed by a long-lived sub-strongly interacting massive particle (sub-SIMP, X). The reactions are non radiative X captures of 7 Be and 7 Li which can be operative if the X particle interacts with nuclei strongly enough to drive 7 Be destruction but not strongly enough to form a bound state with 4 He of relative angular momentum L = 1. We suggest that 7 Li problem can be solved as a result of a new process beyond the standard model through which the observable signature was left on the primordial Li abundance.