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Dive into the research topics where Motohiko Kusakabe is active.

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Featured researches published by Motohiko Kusakabe.


Physical Review D | 2007

A Simultaneous Solution to the ^6Li and ^7Li Big Bang Nucleosynthesis Problems from a Long-Lived Negatively-Charged Leptonic Particle

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

The X− Solution to the 6Li and 7Li Big Bang Nucleosynthesis Problems

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

Li 6 production by the radiative decay of long-lived particles

Motohiko Kusakabe; Toshitaka Kajino; Grant J. Mathews

Recent spectroscopic observations of metal-poor stars have indicated that both


Physical Review D | 2009

Effect of long-lived strongly interacting relic particles on big bang nucleosynthesis

Motohiko Kusakabe; Toshitaka Kajino; Takashi Yoshida; Grant J. Mathews

^{7}\mathrm{Li}


Physical Review D | 2012

Updated constraint on a primordial magnetic field during big bang nucleosynthesis and a formulation of field effects

Masahiro Kawasaki; Motohiko Kusakabe

and


Physical Review D | 2010

New results on catalyzed big bang nucleosynthesis with a long-lived negatively charged massive particle

Motohiko Kusakabe; Toshitaka Kajino; Takashi Yoshida; Grant J. Mathews

^{6}\mathrm{Li}


Physical Review D | 2017

New observational limits on dark radiation in braneworld cosmology

Nishanth Sasankan; Mayukh R. Gangopadhyay; Grant J. Mathews; Motohiko Kusakabe

have abundance plateaus with respect to the metallicity. Abundances of


Physical Review D | 2014

Cosmological solutions to the Lithium problem: Big-bang nucleosynthesis with photon cooling,

Dai Yamazaki; Myung-Ki Cheoun; Grant J. Mathews; Motohiko Kusakabe; Toshitaka Kajino

^{7}\mathrm{Li}


Physical Review D | 2011

X

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

-particle decay and a primordial magnetic field

Myung-Ki Cheoun; Toshitaka Kajino; Motohiko Kusakabe; Grant J. Mathews

^{6}\mathrm{Li}

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Kyungsik Kim

Korea Aerospace University

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