Pulsar Kick and Asymmetric Iron Velocity Distribution in SN 1987A

We have investigated the relation of the direction of the momentum among the matter, neutrino, and proto-neutron star in a collapse-driven supernova in order to discuss the pulsar kick. In particular, we have investigated the effects of the pulsar motion on the explosion, which are neglected in the previous study. As a result, it is suggested that the direction of the total momentum of the matter and neutrino is opposite to that of the momentum of the proto-neutron star in the asymmetric explosion models. This is because the center of the explosion deviates from the center of the progenitor due to the pulsar motion. This picture is common among the asymmetric explosion models. So if we assume that the pulsar motion is caused by an asymmetric supernova explosion, the neutron star born in SN 1987A, which has not been found yet, will be moving in the southern part of the remnant. In other words, if we can find one neutron star in SN 1987A on the south part of the remnant, asymmetric explosion models will be supported by the observation better than the binary models.Comment: 10 pages and 4 postscript figure

Rapid-Process Nucleosynthesis in Neutrino-Magneto-Centrifugally Driven Winds

We have studied whether the rotation and magnetic fields in neutrino-driven winds can be key processes for the rapid-process (r-process) nucleosynthesis. We have examined the features of a steady and subsonic wind solutions which extend the model of Weber and Davis (1967), which is a representative solar wind model. As a result, we found that the entropy per baryon becomes lower and the dynamical timescale becomes longer as the angular velocity becomes higher. These results are inappropriate for the production of the r-process nuclei. As for the effects of magnetic fields, we found that a solution as a steady wind from the surface of the proto-neutron star can not be obtained when the strength of the magnetic field becomes $\ge$ $10^{11}$ G. Since the magnetic field in normal pulsars is of order $10^{12}$ G, a steady wind solution might not be realized there, which means that the models in this study may not be adopted for normal proto-neutron stars. In this situation, we have little choice but to conclude that it is difficult to realize a successful r-process nucleosynthesis in the wind models in this framework.Comment: 20 pages and 4 postscript figures. submitted to Publications of the Astronomical Society of Japa

Anisotropic e+e−e^+ e^- pressure due to the QED effect in strong magnetic fields and the application to the entropy production in neutrino-driven wind

We study the equation of state of electron in strong magnetic fields which are greater than the critical value $B_c \simeq 4.4 \times 10^{13}$ Gauss. We find that such a strong magnetic field induces the anisotropic pressure of electron. We apply the result to the neutrino-driven wind in core-collapse supernovae and find that it can produce large entropy per baryon, $S \sim 400 k_B$. This mechanism might successfully account for the production of the heavy nuclei with mass numbers A = 80 -- 250 through the r-process nucleosynthesis.Comment: 4 pages, using REVTeX and 3 postscript figure

Oscillating scalar-field dark matter in supergravity

We show that an oscillating scalar field in supergravity of mass of the order of $\sim$ TeV with a nonzero vacuum expectation value ($\sim 10^{10}$ GeV) can be a candidate of cold dark matter (CDM). To avoid the gravitino problem, we need a low reheating temperature after the primordial inflation. Then, the energy density of the oscillating scalar field satisfies all the requirements for CDM at present in the universe.Comment: LaTeX JHEP-format, to appear in JHE

Production cross sections of gamma-rays, electrons, and positrons in p-p collisions

Because the production cross sections of gamma-rays, electrons, and positrons made in p-p collisions, $\sigma_{pp\rightarrow \gamma}$ and $\sigma_{pp\rightarrow {e}^\pm}$, respectively, are kinematically equivalent with respect to the parent pion-production cross section $\sigma_{pp\rightarrow \pi}$, we obtain $\sigma_{pp\rightarrow {e}^\pm}$ directly from the machine data on $\sigma_{pp\rightarrow \gamma}$. In Sato et al. (2012), we give explicitly $\sigma_{pp\rightarrow \gamma}$, reproducing quite well the accelerator data with LHC, namely $\sigma_{pp\rightarrow {e}^\pm}$ is applicable enough over the wide energy range from GeV to 20\,PeV for projectile proton energy. We dicuss in detail the relation between the cross sections, and present explicitly $\sigma_{pp\rightarrow {e}^\pm}$ that are valid into the PeV electron energy.Comment: 27 pages, 2 tables, 4 figures. Version after major revision. Accepted for publication in Astroparticle Physics; paper can be also downloaded from http://www.phys.aoyama.ac.jp/~ryo/papers/pp-collision2_ApP.pd

Polarization tensors in a strong magnetic field

The vacuum polarization tensor in strong external magnetic fields has been evaluated numerically for various strengths of magnetic fields and momenta of photons under the threshold of the $e^{\pm}$ pair creation. The fitting formula has been obtained which reproduces the calculated results within 10 % of error. The proper time method is employed further to obtain the retarded polarization tensor for finite temperature plasmas