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

¹ Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582, Japan
² Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa, Chiba 277-8582, Japan

^a e-mail: kusakabe@icrr.u-tokyo.ac.jp

Abstract

The plateau of ⁷Li abundance as a function of the iron abundance by spectroscopic 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 ⁷Li 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 ⁷Be and ⁷Li 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 ⁷Li 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 ⁷Li 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.