The work of K. K. was supported in part by PPARC Grant No. PP/D000394/1, EU Grant No. MRTN-CT-2006-035863, the European Union through the Marie Curie Research and Training Network "UniverseNet," MRTN-CT-2006-035863, and Grant-in-Aid for Scientific research from the Ministry of Education, Science, Sports, and Culture, Japan (No. 18071001). The work of M. K. was supported in part by the Grant-in-Aid for the Ministry of Education, Culture, Sports, Science, and Technology, Government of Japan (No. 22740140). The work of J. S. was supported in part by the Grant-in-Aid for the Ministry of Education, Culture, Sports, Science, and Technology, Government of Japan (Nos. 20025001, 20039001, and 20540251). The work of T. S. was supported in part by MEC and FEDER (EC) Grant No. FPA2005-01678. The work of M. Y. was supported in part by the Grant-in-Aid for the Ministry of Education, Culture, Sports, Science, and Technology, Government of Japan (No. 20007555).

We calculate the relic density of stau at the big-bang nucleosynthesis era in the coannihilation scenario of the minimal supersymmetric standard model. In this scenario, stau can be long lived and have significance in the remediation of light elements abundances. The freeze-out of stau is corroborated by solving the Boltzmann equation numerically, and the parameter dependence of the relic density is investigated. The possibility of solving the (7)Li problem is examined by taking account into the long-lived stau. By adopting an observational value of (7)Li in [J. Melendez and I. Ramirez, Astrophys. J. 615, L33 (2004).], we get minimal supersymmetric standard model parameter space in which abundances of both dark matter and all of the light elements are reproduced in accordance with observations. We also address the influence of intergenerational mixing on our calculation.

Peer reviewed