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Journal Articles

Isomer production ratio of the $$^{112}$$Cd($$n,gamma$$)$$^{113}$$Cd reaction in an $$s$$-process branching point

Hayakawa, Takehito*; Toh, Yosuke; Kimura, Atsushi; Nakamura, Shoji; Shizuma, Toshiyuki*; Iwamoto, Nobuyuki; Chiba, Satoshi*; Kajino, Toshitaka*

Physical Review C, 103(4), p.045801_1 - 045801_5, 2021/04

 Times Cited Count:0 Percentile:0.02(Physics, Nuclear)

Journal Articles

Measurement of the isomer production ratio for the $$^{112}$$Cd($$n,gamma$$)$$^{113}$$Cd reaction using neutron beams at J-PARC

Hayakawa, Takehito*; Toh, Yosuke; Huang, M.; Shizuma, Toshiyuki*; Kimura, Atsushi; Nakamura, Shoji; Harada, Hideo; Iwamoto, Nobuyuki; Chiba, Satoshi*; Kajino, Toshitaka*

Physical Review C, 94(5), p.055803_1 - 055803_6, 2016/11

 Times Cited Count:4 Percentile:37.68(Physics, Nuclear)

Journal Articles

$$beta$$-decay half-lives of 110 neutron-rich nuclei across the $$N$$=82 shell gap; Implications for the mechanism and universality of the astrophysical $$r$$ process

Lorusso, G.*; Nishimura, Shunji*; Xu, Z. Y.*; Jungclaus, A.*; Shimizu, Y.*; Simpson, G. S.*; S$"o$derstr$"o$m, P.-A.*; Watanabe, H.*; Browne, F.*; Doornenbal, P.*; et al.

Physical Review Letters, 114(19), p.192501_1 - 192501_7, 2015/05

 Times Cited Count:130 Percentile:97.86(Physics, Multidisciplinary)

Journal Articles

Neutrinos in core-collapse supernovae and nucleosynthesis

Kajino, Toshitaka*; Mathews, G. J.*; Hayakawa, Takehito

Journal of Physics G; Nuclear and Particle Physics, 41(4), p.044007_1 - 044007_34, 2014/04

 Times Cited Count:18 Percentile:77.4(Physics, Nuclear)

Neutrino interactions are a key component of the mechanism for supernova explosions. They also play an important role in the associated nucleosynthesis. Nevertheless, a number of issues remain to be resolved. In this review we summarize research by our group and others on some of these issues. Much effort is now invested in understanding the transport of neutrinos from the core and the role of neutrino heated convection in the outer envelopes. In addition to the neutrino transport issues, we review some current topics in neutrino induced nucleosynthesis (the neutrino and p processes). We review some current issues regarding the synthesis of the neutirno-process isotopes $$^{180}$$Ta and $$^{138}$$La and summarize the application of the neutrino -process chronometers, $$^{136,138}$$Ce, $$^{138}$$La, and$$^{92}$$Nb. We also consider other aspects.

Journal Articles

Supernova neutrino nucleosynthesis of the radioactive $$^{92}$$Nb observed in primitive meteorites

Hayakawa, Takehito; Nakamura, Ko*; Kajino, Toshitaka*; Chiba, Satoshi; Iwamoto, Nobuyuki; Cheoun, M. K.*; Mathews, G. J.*

Astrophysical Journal Letters, 779(1), p.L9_1 - L9_5, 2013/12

 Times Cited Count:26 Percentile:61.74(Astronomy & Astrophysics)

Short-lived radioactivities are used as nuclearcosmochronometers for understanding the free decay time from the last nucleosynthesis episode until the time of solar system formation (SSF). $$^{92}$$Nb (half-life of 34.7 Myr) is one of a short-lived isotope existed at SSF. However, there is a controversy in that the inferred initial abundance ratios for $$^{92}$$Nb/$$^{93}$$Nb at the time of SSF cluster around two different values; one is near 10$$^{-3}$$, while the other is near 10$$^{-5}$$. Moreover, the astrophysical mechanism for the synthesis of $$^{92}$$Nb has remained an unsolved problem. Here we argue that conventional nucleosynthesis mechanisms cannot produce $$^{92}$$Nb and propose a new mechanism for the nucleosynthesis of this isotopebased upon neutrino induced reactions occurring during core-collapse supernova explosions.

Journal Articles

Nucleosynthesis in supernovae and neutrino oscillation

Suzuki, Toshio*; Yoshida, Takashi*; Chiba, Satoshi; Kajino, Toshitaka*

Nihon Butsuri Gakkai-Shi, 67(1), p.49 - 54, 2012/01

Neutrino processes play important roles in synthesis of $$^7$$Li, $$^{11}$$B, $$^{138}$$La, $$^{180}$$Ta and other elements in explosive environments realized in supernovae. In order to understand better the neutrino processes, we constructed new shell model Hamiltonians based on recent progress of physics in unstable nuclei near the neutron drip-line. We then applied these Hamiltonians to calculate the neutrino-nucleus reaction cross sections through detailed and careful comparison of nuclear properties with those of relevant experimental data. We can thus carry out precise and reliable theoretical estimate of supernova nucleosynthesis of $$^{7}$$Li, $$^{11}$$B, etc including the neutrino processes. Finally we propose a new method to determine unknown neutrino oscillation parameters, namely the mixing angle $$theta_{13}$$ and the mass hierarchy, by making use of strong dependence of the yields of $$^{7}$$Li, $$^{11}$$B on these parameters.

Journal Articles

Nucleosynthesis in supernovae and neutrino oscillation

Suzuki, Toshio*; Yoshida, Takashi*; Chiba, Satoshi; Kajino, Toshitaka*

Nihon Butsuri Gakkai-Shi, 67(1), p.49 - 54, 2012/01

Neutrino-nucleus reaction processes play important roles in synthesis of $$^7$$Li, $$^{11}$$B, $$^{138}$$La, $$^{180}$$Ta and other elements in explosive environments realized in supernovae. We have constructed new shell model Hamiltonians based on recent progress of physics in unstable nuclei near the neutron drip-line. The spin responses of nuclei are found to be remarkably improved by the new Hamiltonians. We then applied these Hamiltonians to calculate the neutrino-nucleus reaction cross sections, and obtained more precise and reliable theoretical estimate of supernova nucleosynthesis of $$^7$$Li, $$^{11}$$B, etc including the neutrino processes. Finally we propose a new method to determine unknown neutrino oscillation parameters, namely the mixing angle $$theta_{13}$$ and the mass hierarchy, by making use of strong dependence of the yields of $$^7$$Li and $$^{11}$$B on these parameters.

Journal Articles

Reanalysis of the ($$J$$ = 5) state at 592 keV in $$^{180}$$Ta and its role in the $$nu$$-process nucleosynthesis of $$^{180}$$Ta in supernovae

Hayakawa, Takehito; Mohr, P.*; Kajino, Toshitaka*; Chiba, Satoshi; Mathews, G. J.*

Physical Review C, 82(5), p.058801_1 - 058801_4, 2010/11

 Times Cited Count:13 Percentile:60.78(Physics, Nuclear)

We analyze the production and freeze-out of the isomer $$^{180}$$Ta in the $$nu$$-process. We consider the influence of a possible low-lying intermediate ($$J$$ = 5) state at 592 keV using a transition width estimated from the measured half-life. This more realistic width is much smaller than the previous estimate. We find that the 592 keV state leads only to a small reduction of the residual isomer ratio from the previous result. The isomer ratio changes from 0.39 to 0.38, whereas previously it was estimated that this transition could reduce the ratio to R = 0.18. This finding strengthens the evidence that $$^{138}$$La and $$^{180}$$Ta are coproduced by neutrino nucleosynthesis with an electron neutrino temperature of ${it kT}$ $$approx$$ 4 MeV.

Journal Articles

Neutrino reactions on $$^{138}$$La and $$^{180}$$Ta via charged and neutral currents by the quasiparticle random-phase approximation

Cheoun, M. K.*; Ha, E.*; Hayakawa, Takehito; Kajino, Toshitaka*; Chiba, Satoshi

Physical Review C, 82(3), p.035504_1 - 035504_7, 2010/09

 Times Cited Count:36 Percentile:88.24(Physics, Nuclear)

We investigate neutrino-induced reactions on heavy nuclei. Charged current (CC) reactions,$$^{138}$$Ba($$nu_e$$, $$e$$$$^-$$)$$^{138}$$La and $$^{180}$$Hf($$nu_e$$, $$e$$$$^-$$)$$^{180}$$Ta are calculated by a quasi-particle random phase approximation (QRPA) with pairing correlations. For neutral current (NC) reactions, $$^{139}$$La($$nu,nu'$$)$$^{139}$$La$$^*$$ and $$^{181}$$Ta($$nu,nu'$$)$$^{181}$$Ta$$^*$$, we generate ground and excited states of odd-even target nuclei, $$^{139}$$La and $$^{181}$$Ta, by operating one quasi-particle to even-even nuclei. Numerical results for CC reactions are shown to be consistent with recent semi-empirical data deduced from the Gamow-Teller strength distributions measured in the ($$^3$$He,$$t$$) reaction. Results for NC reactions are estimated to be smaller by a factor about 4 to 5 rather than those by CC reactions. Finally, cross sections weighted by the incident neutrino flux in the core collapsing supernova are presented for further applications to the network calculations for relevant nuclear abundances.

Journal Articles

New estimate for the time-dependent thermal nucleosynthesis of $$^{180}$$Ta$$^{m}$$

Hayakawa, Takehito; Kajino, Toshitaka*; Chiba, Satoshi; Mathews, G. J.*

Physical Review C, 81(5), p.052801_1 - 052801_4, 2010/05

 Times Cited Count:46 Percentile:91.45(Physics, Nuclear)

The nucleosynthesis of $$^{180}$$Ta has remained an unsolved problem. The supernova neutrino process has been proposed as the origin of $$^{180}$$Ta but its model calculation overproduces the $$^{180}$$Ta solar abundance. This may originate from the unique feature that the naturally occurring abundance of $$^{180}$$Ta is actually a meta-stable isomer, while the ground state is beta-unstable. We have made a new time-dependent calculation of the supernova production ratio of the long-livedisomer in $$^{180}$$Ta. Such a time-dependent solution is crucial for understanding the production and survival of this isotope. We find that the explicit time evolution of the synthesis of $$^{180}$$Ta using the available nuclear data shows $$^{180}$$Ta can be produced by neutrino process and neutrino temperature of 4 MeV.

Journal Articles

Neutron capture cross section to $$^{113}$$Cd isomer and $$_{s-}$$process contribution to rare $$_{p-}$$nuclide $$^{115}$$Sn

Hayakawa, Takehito; Shizuma, Toshiyuki; Chiba, Satoshi; Kajino, Toshitaka*; Hatsukawa, Yuichi; Iwamoto, Nobuyuki; Shinohara, Nobuo; Harada, Hideo

Astrophysical Journal, 707(2), p.859 - 865, 2009/12

 Times Cited Count:5 Percentile:18.69(Astronomy & Astrophysics)

no abstracts in English

Journal Articles

Reply to "Comment on '$$^{138}$$La-$$^{138}$$Ce-$$^{136}$$Ce nuclear cosmochronometer of supernova neutrino process'"

Hayakawa, Takehito; Shizuma, Toshiyuki; Kajino, Toshitaka*; Ogawa, Kengo*; Nakada, Hitoshi*

Physical Review C, 79(5), p.059802_1 - 059802_2, 2009/05

 Times Cited Count:0 Percentile:1.45(Physics, Nuclear)

We have proposed a new nuclear cosmochronometer $$^{138}$$La(T$$_{1/2}$$=102 Gyr)-$$^{138}$$Ce-$$^{136}$$Ce for measuring the time elapsed from a supernova $$nu$$ process episode. $$^{138}$$La is synthesized by the $$nu$$ process. If a 1$$^+$$ excited state exists at energy lower than 72 keV, the 1$$^+$$ state may be a $$beta$$ unstable isomer and $$^{138}$$La synthesized by the $$nu$$ process is destroyed via the isomer. Recently, Byelikov et al. have measured Gamow-Teller strength distributions in $$^{138}$$La. It has been presented that this experiment shows that the existence of a low-energy 1$$^+$$ state in $$^{138}$$La is extremely unlikely. Our calculated result is consistent with their result and we conclude that there is no evidence that suggests the existence of the 1$$^+$$ isomer in $$^{138}$$La.

Journal Articles

A New measurement of the astrophysical $$^8$$Li(d,t)$$^7$$Li reaction

Hashimoto, Takashi; Ishiyama, Hironobu*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari; Jeong, S.-C.*; Tanaka, Masahiko*; Yoshikawa, Nobuharu*; Nomura, Toru*; et al.

Physics Letters B, 674(4-5), p.276 - 280, 2009/04

 Times Cited Count:6 Percentile:44.7(Astronomy & Astrophysics)

The excitation function of the $$^8$$Li(d,t)$$^7$$Li reaction was directly measured using $$^8$$Li beams at E$$_{mathrm{cm}}$$ = 0.3, 0.4, 0.5, 0.7, 0.8, 1.0, 1.1, and 1.2 MeV with CD$$_2$$ targets. The beam energies covered the Gamow peaks for 1$$sim$$3$$times$$10$$^9$$ K. Large cross sections were observed at around E$$_{mathrm{cm}}$$ = 0.8 MeV, implying a resonance state located at 22.4 MeV in $$^{10}$$Be. The present astrophysical reaction rate is higher in one order magnitude than the presently adopted rate at around 1$$times$$10$$^9$$ K.

Journal Articles

Empirical abundance scaling laws and implications for the $$gamma$$ process in core-collapse supernovae

Hayakawa, Takehito; Iwamoto, Nobuyuki; Kajino, Toshitaka*; Shizuma, Toshiyuki; Umeda, Hideyuki*; Nomoto, Kenichi*

Astrophysical Journal, 685(2), p.1089 - 1102, 2008/10

 Times Cited Count:24 Percentile:56.14(Astronomy & Astrophysics)

no abstracts in English

Journal Articles

Neutrino-nucleus reaction cross sections for light element synthesis in supernova explosions

Yoshida, Takashi*; Suzuki, Toshio*; Chiba, Satoshi; Kajino, Toshitaka*; Yokomakura, Hidekazu*; Kimura, Keiichi*; Takamura, Akira*; Hartmann, D.*

Astrophysical Journal, 686(1), p.448 - 466, 2008/10

The neutrino-nucleus reaction cross sections of $$^4$$He and $$^{12}$$C are evaluated using new shell model Hamiltonians. Branching ratios of various decay channels are calculated to evaluate the yields of Li, Be, and B produced through the $$nu$$-process in supernova explosions. The new cross sections enhance the yields of $$^{7}$$Li and $$^{11}$$B produced during the supernova explosion of a 16.2 M$$_odot$$ star model compared to our previous study by factors of 1.3 and 1.2, respectively. On the other hand, the yield of $$^{10}$$B decreases by a factor of three. The yields of $$^{6}$$Li, $$^{9}$$Be, and the radioactive nucleus $$^{10}$$Be are found at a level of 10 to 11 M$$_odot$$. The temperature of $$nu mu, tau$$- and $$bar{nu} mu, tau$$-neutrinos inferred from the supernova contribution of $$^{11}$$B in Galactic chemical evolution models is constrained to be in the range 4.5 MeV to 6.4 MeV. The increase in the $$^{7}$$Li and $$^{11}$$B yields due to neutrino oscillations is demonstrated with the new cross sections.

Journal Articles

Neutrino-nucleus reaction cross sections for light element synthesis in supernova explosions

Yoshida, Takashi*; Suzuki, Toshio*; Chiba, Satoshi; Kajino, Toshitaka*; Yokomakura, Hidekazu*; Kimura, Keiichi*; Takamura, Akira*; Hartmann, D. H.*

Astrophysical Journal, 686(1), p.448 - 466, 2008/10

 Times Cited Count:86 Percentile:89.74(Astronomy & Astrophysics)

The neutrino-nucleus reaction cross sections of $$^4$$He and $$^{12}$$C are evaluated using new shell model Hamiltonians. The new cross sections enhance the yields of $$^7$$Li and $$^{11}$$B produced during the supernova explosion of a 16.2 $$M_odot$$ star model compared to the case using the conventional cross sections by about 10%. On the other hand, the yield of $$^{10}$$B decreases by a factor of two. The yields of $$^6$$Li, $$^9$$Be, and the radioactive nucleus $$^{10}$$Be are found at a level of $$sim 10^{-11} M_odot$$. The temperature of $$nu_{mu,tau}$$- and $$bar{nu}_{mu,tau}$$-neutrinos inferred from the supernova contribution of $$^{11}$$B in Galactic chemical evolution models is constrained to be in the range 4.3 MeV to 6.5 MeV. The increase in the $$^7$$Li and $$^{11}$$B yields due to neutrino oscillations is demonstrated with the new cross sections.

Journal Articles

$$^{138}$$La-$$^{138}$$Ce-$$^{136}$$Ce nuclear cosmochronometer of supernova neutrino process

Hayakawa, Takehito; Shizuma, Toshiyuki; Kajino, Toshitaka*; Ogawa, Kengo*; Nakada, Hitoshi*

Physical Review C, 77(6), p.065802_1 - 065802_5, 2008/06

 Times Cited Count:13 Percentile:64.55(Physics, Nuclear)

no abstracts in English

Journal Articles

Half-life of the $$^{164}$$Ho by the ($$gamma$$,$$n$$) reaction from Laser Compton scattering $$gamma$$ rays at the electron storage ring NewSUBARU

Hayakawa, Takehito; Shizuma, Toshiyuki; Miyamoto, Shuji*; Amano, So*; Horikawa, Ken*; Ishihara, Kazuki*; Mori, Michiaki; Kawase, Keigo; Kando, Masaki; Kikuzawa, Nobuhiro; et al.

Physical Review C, 77(6), p.068801_1 - 068801_4, 2008/06

 Times Cited Count:12 Percentile:62.36(Physics, Nuclear)

no abstracts in English

Journal Articles

The r-process element abundance with a realistic fission fragment mass distribution

Chiba, Satoshi; Koura, Hiroyuki; Maruyama, Toshiki; Ota, Masahisa*; Tatsuda, Sayuki*; Wada, Takahiro*; Tachibana, Takahiro*; Sumiyoshi, Kosuke*; Otsuki, Kaori*; Kajino, Toshitaka*

AIP Conference Proceedings 1016, p.162 - 167, 2008/05

Effect of the $$beta$$-delayed fission in r-process abundance is investigated. The data base for the fission fragment mass distribution used in the r-process network calculation is constructed based on the 2-center shell model and Langevinequation. The $$beta$$-decay rates (no emissive, neutron emission and $$beta$$-delayed fission) are also newly calculated with the gross theory. The differences appeared in the final element abundance calculated with and without fission process are demonstrated and the mass region modified by the fission products is presented.

Journal Articles

Systematic study for the shell effect in the fission fragment mass distribution reptured from neutron rich nuclei

Ota, Masahisa*; Tatsuda, Sayuki*; Yamamoto, Kazuyuki*; Asano, Tomomasa*; Wada, Takahiro*; Hashizume, Kazuaki*; Sumiyoshi, Kosuke*; Otsuki, Kaori*; Kajino, Toshitaka*; Koura, Hiroyuki; et al.

Nuclear Physics A, 805(2), p.558 - 560, 2008/02

The data base for the fission fragment mass distribution used in the r-process network calculation is constructed. The differences appeared in the final element abundance calculated with and without fission process are demonstrated and the mass region modified by the fission products is presented.

62 (Records 1-20 displayed on this page)