On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

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The Observation of Gravitational Waves from a Binary Black Hole Merger

日本物理学会誌及びJournal of the Physical Society of Japanの月刊について

There is almost universal agreement among astronomers that most of the mass in the Universe and most of the mass in the Galactic halo is dark. Many lines of reasoning suggest that the dark matter consists of some new, as yet undiscovered, weakly-interacting massive particle (WIMP). There is now a vast experimental effort being surmounted to detect WIMPS in the halo. The most promising techniques involve direct detection in low-background laboratory detectors and indirect detection through observation of energetic neutrinos from annihilation of WIMPs that have accumulated in the Sun and/or the Earth. Of the many WIMP candidates, perhaps the best motivated and certainly the most theoretically developed is the neutralino, the lightest superpartner in many supersymmetric theories. We review the minimal supersymmetric extension of the Standard Model and discuss prospects for detection of neutralino dark matter. We review in detail how to calculate the cosmological abundance of the neutralino and the event rates for both direct- and indirect-detection schemes, and we discuss astrophysical and laboratory constraints on supersymmetric models. We isolate and clarify the uncertainties from particle physics, nuclear physics, and astrophysics that enter at each step in the calculation. We briefly review other related dark-matter candidates and detection techniques.

Supersymmetric Dark Matter

KamLAND has measured the flux of nu;(e)'s from distant nuclear reactors. We find fewer nu;(e) events than expected from standard assumptions about nu;(e) propagation at the 99.95% C.L. In a 162 ton.yr exposure the ratio of the observed inverse beta-decay events to the expected number without nu;(e) disappearance is 0.611+/-0.085(stat)+/-0.041(syst) for nu;(e) energies >3.4 MeV. In the context of two-flavor neutrino oscillations with CPT invariance, all solutions to the solar neutrino problem except for the "large mixing angle" region are excluded.

First Results from KamLAND: Evidence for Reactor Anti-Neutrino Disappearance

A thin (0.05cm) and wide area (5cmX5cm) NaI(Tl) scintillator was developed. The performance of the thin NaI(Tl) plate, energy resolution, single photoelectron energy and position sensitivity were tested. An excellent energy resolution of 20% (FWHM) at 60keV was obtained. The single photoelectron energy was calculated to be approximately 0.42 0.02keV. Position information in the 5cmx5cm area of the detector was also obtained by analyzing the ratio of the number of photons collected at opposite ends of the detector. The position resolution was obtained to be 1cm (FWHM) in the 5cmx5cm area.

The performance of thin NaI(Tl) scintillator plate for dark matter search

MOON is a multilayer system of plastic scintillators and 100Mo films for 100Mo 0νββ decays. A prototype detector MOON-1 was built with 6 layers of plastic scintillators and 142g of 100Mo films for background (BG), energy and position resolution studies of the MOON detector. No serious BG from natural radioactive isotopes (RI) for 0νββ detection was found.

http://iopscience.iop.org/article/10.1088/1742-6596/39/1/096/pdf

The MOON-1 detector construction and the study of backgrounds from radioactive isotopes

New Approach to M1 Cross Section for D(gamma,n) via the D(7Li,7Be) Reaction.

This is a brief report on Majorana neutrino(v) mass to be studied by neutrino-less double beta decays (0vββ). The v-mass depends on the nuclear structure of the ββ isotope, the effective detector volume and the background rate. Subjects discussed include 1 0vββ and v-mass, 2 0vββ nuclear matrix elements, and 3 0vββ experiments and v-mass sensitivities.

Double beta decay experiments and v-mass sensitivities

A dark matter search project needs and extremely low background radiation detector since the expected event rate of dark matter is less than a few events in one year in one tonne of the detector mass. The authors developed a highly radiopure NaI(Tl) crystal to search for dark matter. The best combination of the purification methods was developed, resulting $^{\mathrm{nat}}$K and $^{210}$Pb were less than 20 ppb and 5.7 $\mu$Bq/kg, respectively. 
The authors will construct a large volume detector system with high-purity NaI(Tl) crystals. The design and the performance of the prototype detector module will be reported in this article.

Ken-Ichi Fushimi

Papers

The performance of thin NaI(Tl) scintillator plate for dark matter search

The MOON-1 detector construction and the study of backgrounds from radioactive isotopes

New Approach to M1 Cross Section for D(gamma,n) via the D(7Li,7Be) Reaction.

Double beta decay experiments and v-mass sensitivities

Dark matter search with high purity NaI(Tl) scintillator