arXiv subjects

N. Kanda

Publications and source records attributed to N. Kanda.

23 records · Page 2Linked to original sources

arXiv2017

The status of KAGRA underground cryogenic gravitational wave telescope

KAGRA is a 3-km interferometric gravitational wave telescope located in the Kamioka mine in Japan. It is the first km-class gravitational wave telescope constructed underground to reduce seismic noise, and the first km-class telescope to use cryogenic cooling of test masses to reduce thermal noise. The construction of the infrastructure to house the interferometer in the tunnel, and the initial phase operation of the interferometer with a simple 3-km Michelson configuration have been completed. The first cryogenic operation is expected in 2018, and the observing runs with a full interferometer are expected in 2020s. The basic interferometer configuration and the current status of KAGRA are described.

gr-qc↗

arXiv2013

T-matrix of $Z^0$ Decay into Two Photons

We first confirm that Nishijima's method of the $π^0 \rightarrow γ+γ$ calculation can precisely reproduce the observed life time of $π^0$ decay. Then, we calculate, for the first time, the T-matrix of the $Z^0 \rightarrow γ+γ$ process in which the vertex of the $γ^μγ_5$ is responsible for the decay of the weak vector boson. Even though the decay rate itself vanishes to zero due to the symmetry nature of two photons (Landau-Yang theorem), the T-matrix of the process has neither linear nor logarithmic divergences. Therefore, there is no room for the regularization of the triangle diagrams with the $γ^μγ^5$ vertex. Further, the T-matrices of all the triangle diagrams do not have any divergences at all, and therefore it is rigorously proved that the anomaly equation is spurious and appears only because of the improper regularization of unphysical amplitudes.

hep-ph↗

arXiv2010

Coherent versus coincidence detection of gravitational wave signals from compact inspiraling binaries

We compare two multi-detector detection strategies, namely, the coincidence and the coherent, for the detection of spinless inspiraling compact binary gravitational wave signals. The coincident strategy treats the detectors as if they are isolated - compares individual detector statistics with their respective thresholds while the coherent strategy combines the detector network data {\it phase coherently} to obtain a single detection statistic which is then compared with a single threshold. In the case of geographically separated detectors, we also consider an {\it enhanced} coincidence strategy because the usual (naive) coincidence strategy yields poor results for misaligned detectors. For simplicity, we consider detector pairs having the same power spectral density of noise, as that of initial LIGO and also assume the noise to be stationary and Gaussian. We compare the performances of the methods by plotting the \emph{receiver operating characteristic} (ROC) for the two strategies. A single astrophysical source as well as a distribution of sources is considered. We find that the coherent strategy performs better than the two coincident strategies under the assumptions of stationary Gaussian detector noise.

gr-qc↗

arXiv2009

New Renormalization Scheme of Vacuum Polarization in QED

We examine the vacuum polarization contribution in the renormalization scheme of QED. Normally, the quadratic divergence term is discarded under the condition that the counter term of the Lagrangian density should be gauge invariant. Here, it is shown that the whole contribution of the photon self-energy should not be considered for the renormalization procedure. In fact, the finite contribution of the renormalization in the vacuum polarization is shown to give rise to the hyperfine splitting energy which disagrees with the experimental observation in hydrogen atom. For the treatment of the vacuum polarization, we present a new renormalization scheme of the photon self-energy diagram.

hep-th↗

arXiv2002

Force measurements of a superconducting-film actuator for a cryogenic interferometric gravitational-wave detector

We measured forces applied by an actuator with a YBCO film at near 77 K for the Large-scale Cryogenic Gravitational-wave Telescope (LCGT) project. An actuator consisting of both a YBCO film of 1.6 micrometers thickness and 0.81 square centimeters area and a solenoid coil exerted a force of up to 0.2 mN on a test mass. The presented actuator system can be used to displace the mirror of LCGT for fringe lock of the interferometer.

gr-qc↗