Motohiko Kusakabe
University of Tokyo
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Featured researches published by Motohiko Kusakabe.
Physical Review D | 2007
Motohiko Kusakabe; Toshitaka Kajino; Richard N. Boyd; Takashi Yoshida; Grant J. Mathews
The {sup 6}Li abundance observed in metal-poor halo stars exhibits a plateau similar to that for {sup 7}Li suggesting a primordial origin. However, the observed abundance of {sup 6}Li is a factor of 10{sup 3} larger and that of {sup 7}Li is a factor of 3 lower than the abundances predicted in the standard big bang when the baryon-to-photon ratio is fixed by Wilkinson microwave anisotropy probe. Here we show that both of these abundance anomalies can be explained by the existence of a long-lived massive, negatively charged leptonic particle during nucleosynthesis. Such particles would capture onto the synthesized nuclei thereby reducing the reaction Coulomb barriers and opening new transfer reaction possibilities, and catalyzing a second round of big bang nucleosynthesis. This novel solution to both of the Li problems can be achieved with or without the additional effects of stellar destruction.
The Astrophysical Journal | 2008
Motohiko Kusakabe; Toshitaka Kajino; Richard N. Boyd; Takashi Yoshida; Grant J. Mathews
The 6Li abundance observed in metal-poor halo stars exhibits a plateau as a function of metallicity similar to that for 7Li, suggesting a big bang origin. However, the inferred primordial abundance of 6Li is ~1000 times larger than that predicted by standard big bang nucleosynthesis for the WMAP baryon-to-photon ratio. In addition, the inferred 7Li primordial abundance is 3 times smaller than the big bang prediction. We describe a possible simultaneous solution to both of these lithium problems that is based on a hypothetical massive, negatively charged leptonic particle that binds to the light nuclei produced in big bang nucleosynthesis, but decays long before it can be detected. We consider only the X-nuclear reactions and assume that the effect of decay products is negligible, as would be the case if lifetime were large or the mass difference between the charged particle and its daughter were small. An interesting feature is that, because the particle gets bound to the existing nuclei after the cessation of the usual big bang nuclear reactions, a second longer epoch of nucleosynthesis can occur among X-nuclei with reduced Coulomb barriers. We confirm that reactions in which the hypothetical particle is transferred can greatly enhance the production of 6Li while depleting 7Li. Thus, big bang nucleosynthesis in the presence of these hypothetical particles, with or without an event of stellar processing, can simultaneously solve the two Li abundance problems.
Physical Review D | 2006
Motohiko Kusakabe; Toshitaka Kajino; Grant J. Mathews
Recent spectroscopic observations of metal-poor stars have indicated that both
Physical Review D | 2009
Motohiko Kusakabe; Toshitaka Kajino; Takashi Yoshida; Grant J. Mathews
^{7}\mathrm{Li}
Physical Review D | 2012
Masahiro Kawasaki; Motohiko Kusakabe
and
Physical Review D | 2010
Motohiko Kusakabe; Toshitaka Kajino; Takashi Yoshida; Grant J. Mathews
^{6}\mathrm{Li}
Physical Review D | 2017
Nishanth Sasankan; Mayukh R. Gangopadhyay; Grant J. Mathews; Motohiko Kusakabe
have abundance plateaus with respect to the metallicity. Abundances of
Physical Review D | 2014
Dai Yamazaki; Myung-Ki Cheoun; Grant J. Mathews; Motohiko Kusakabe; Toshitaka Kajino
^{7}\mathrm{Li}
Physical Review D | 2011
Masahiro Kawasaki; Motohiko Kusakabe
are about a factor three lower than the primordial abundance predicted by standard big bang nucleosynthesis (SBBN), and
Physical Review D | 2011
Myung-Ki Cheoun; Toshitaka Kajino; Motohiko Kusakabe; Grant J. Mathews
^{6}\mathrm{Li}