We studied allowed region on the intergenerational mixing parameters of
sleptons from a viewpoint of big-bang nucleosynthesis in a slepton-neutralino
coannihilation scenario. In this scenario, 7Li and 6Li problems can be
solved by considering exotic reactions caused by bound-state effects with a
long-lived slepton. Light element abundances are calculated as functions of the
relic density and lifetime of the slepton which considerably depend on the
intergenerational mixing parameters. Compared with observational light element
abundances, we obtain allowed regions on the intergenerational mixing. Ratio of
selectron component to stau component, ce​, is allowed in 2×10−11≲ce​≲2×10−9 with solving both the 7Li and 6Li
problems. Similarly, the ratio for smuon, cμ​, is allowed in 10−7≲cμ​≲5×10−5 for mass difference between
slepton and neutralino, which is smaller than muon mass, and for the mass difference in
range between muon mass and 125 MeV. We also discuss collider signatures of the
slepton decays. We find characteristic double peaks in momentum distribution of
event number of the slepton decays with allowed mixing parameters. Discoveries
of the double peaks at future collider experiments should confirm our scenario.Comment: 10 pages, 6 figure