arXiv subjects

M. Shimada

Publications and source records attributed to M. Shimada.

4 recordsLinked to original sources

arXiv2016

Background Studies for the MINER Coherent Neutrino Scattering Reactor Experiment

The proposed Mitchell Institute Neutrino Experiment at Reactor (MINER) experiment at the Nuclear Science Center at Texas A&M University will search for coherent elastic neutrino-nucleus scattering within close proximity (about 2 meters) of a 1 MW TRIGA nuclear reactor core using low threshold, cryogenic germanium and silicon detectors. Given the Standard Model cross section of the scattering process and the proposed experimental proximity to the reactor, as many as 5 to 20 events/kg/day are expected. We discuss the status of preliminary measurements to characterize the main backgrounds for the proposed experiment. Both in situ measurements at the experimental site and simulations using the MCNP and GEANT4 codes are described. A strategy for monitoring backgrounds during data taking is briefly discussed.

physics.ins-det↗

arXiv2014

Nuclear tetrahedral states and high-spin states studied using quantum number projection method

We have recently developed an efficient method of performing the full quantum number projection from the most general mean-field (HFB type) wave functions including the angular momentum, parity as well as the proton and neutron particle numbers. With this method, we have been investigating several nuclear structure mechanisms. In this report, we discuss the obtained quantum rotational spectra of the tetrahedral nuclear states formulating certain experimentally verifiable criteria, of the high-spin states, focussing on the wobbling- and chiral-bands, and of the drip-line nuclei as illustrative examples.

nucl-th↗

arXiv2000

Deep Optical Imaging of A Compact Group of Galaxies, Seyfert's Sextet

In order to investigate the dynamical status of Seyfert's Sextet (SS), we have obtained a deep optical ($VR+I$) image of this group. Our image shows that a faint envelope, down to a surface brightness $μ_{\rm optical}$(AB) $\simeq 27$ mag arcsec$^{-2}$, surrounds the member galaxies. This envelope is irregular in shape. It is likely that this shape is attributed either to recent-past or to on-going galaxy interactions in SS. If the member galaxies have experienced a number of mutual interactions over a long timescale, the shape of the envelope should be rounder. Therefore, the irregular-shaped morphology suggests that SS is in an early phase of dynamical interaction among the member galaxies. It is interesting to note that the soft X-ray image obtained with ROSAT (Pildis et al. 1995) is significantly similar in morphology. We discuss the possible future evolution of SS briefly.

astro-ph↗

arXiv2000

A Dynamical Study of Galaxies in the Hickson Compact Groups

In order to investigate dynamical properties of spiral galaxies in the Hickson compact groups (HCGs), we present rotation curves of 30 galaxies in 20 HCGs. We found as follows. 1) There is not significant relation between dynamical peculiarity and morphological peculiarity in HCG spirals. 2) There is no significant relation between the dynamical properties and the frequency distribution of nuclear activities in HCG spirals. 3) There are no significant correlations between the dynamical properties of HCG spirals and any group properties (i.e., the size, the velocity dispersion, the galaxy number density, and the crossing time). 4) Asymmetric and peculiar rotation curves are more frequently seen in the HCG spirals than in field spirals and in cluster ones. However, this tendency is more obviously seen in late-type HCG spirals. These results suggest that the dynamical properties of HCG spirals do not strongly correlate with the morphology, the nuclear activity, and the group properties. Our results also suggest that more frequent galaxy collisions occur in the HCGs than in the field and in the clusters.

astro-ph↗