Yuji Kato

Study of variable stars in the MOA data base: long-period red variables in the Large Magellanic Cloud

ABSTRA C T 146 long-period red variable stars in the Large Magellanic Cloud (LMC) from the three-year Microlensing Observations in Astrophysics (MOA) project data base were analysed. A careful periodic analysis was performed on these stars and a catalogue of their magnitudes, colours, periods and amplitudes is presented. We convert our blue and red magnitudes to K-band values using 19 oxygen-rich stars. A group of red short-period stars separated from the Mira sequence has been found on a (log P,K) diagram. They are located at the short period side of the Mira sequence consistent with the work of Wood & Sebo. There are two interpretations for such stars; a difference in pulsation mode or a difference in chemical composition. We investigated the properties of these stars together with their colour, amplitude and periodicity. We conclude that they have small amplitudes and less regular variability. They are likely to be higher-mode pulsators. A large scatter has also been found on the longperiod side of the (log P,K) diagram. This is possibly a systematic spread given that the blue band of our photometric system covers both standard B and V bands and affects carbon-rich stars.

Development of high intensity laser-electron photon beams up to 2.9 GeV at the SPring-8 LEPS beamline

Abstract A laser-Compton backscattering beam, which we call a ‘Laser-Electron Photon’ beam, was upgraded at the LEPS beamline of SPring-8. We accomplished the gains in backscattered photon beam intensities by factors of 1.5–1.8 with the injection of two adjacent laser beams or a higher power laser beam into the storage ring. The maximum energy of the photon beam was also extended from 2.4xa0GeV to 2.9xa0GeV with deep-ultraviolet lasers. The upgraded beams have been utilized for hadron photoproduction experiments at the LEPS beamline. Based on the developed methods, we plan the simultaneous injection of four high power laser beams at the LEPS2 beamline, which has been newly constructed at SPring-8. As a simulation result, we expect an order of magnitude higher intensities close to 10 7 xa0s −1 and 10 6 xa0s −1 for tagged photons up to 2.4xa0GeV and 2.9xa0GeV, respectively.

Wide-Field Camera for Gravitational Microlensing Survey: MOA-cam2

We have constructed a large, mosaic CCD camera called MOA-cam2 which has 4096 × 6144-pixelsto search for gravitational microlensing events. MOA-cam2 has three4096 × 2048-pixel SITe CCD chips, which have a very high quantum efficiency (nearly 80% in the wave region 500 to 800 nm),and three buttable sides. We have placed the threechips side by side with 100 μm dead space. MOA-cam2 has been installed on the 61 cm Boller and Chivens telescope of the MOA collaboration at the Mt. John University Observatory (MJUO) in NewZealand since July 1998. The field coverage is 0.92° × 1.38° per exposure. The technical details of MOA-cam2 and the first images obtained with the Boller and Chivens telescope are presented. MOA-cam2 introduces a second phase of research on gravitational microlensing by the MOA collaboration.

Low Resolution QR-Code Recognition by Applying Super-Resolution Using the Property of QR-Codes

This paper proposes a method for low resolution QR-code recognition. A QR-code is a two-dimensional binary symbol that can embed various information such as characters and numbers. To recognize a QR-code correctly and stably, the resolution of an input image should be high. In practice, however, recognition of a QR-code is usually difficult due to low resolution when it is captured from a distance. In this paper, we propose a method to improve the performance of low resolution QR-code recognition by using the super-resolution technique that generates a high resolution image from multiple low-resolution images. Although a QR-code is a binary pattern, it is observed as a grayscale image due to the degradation through the capturing process. Especially the pixels around the borders between white and black regions become ambiguous. To overcome this problem, the proposed method introduces a binary pattern constraint to generate super-resolved images appropriate for recognition. Experimental results showed that a recognition rate of 98% can be achieved by the proposed method, which is a 15.7% improvement in comparison with a method using a conventional super-resolution method.

Job monitoring on DIRAC for Belle II distributed computing

We developed a monitoring system for Belle II distributed computing, which consists of active and passive methods. In this paper we describe the passive monitoring system, where information stored in the DIRAC database is processed and visualized. We divide the DIRAC workload management flow into steps and store characteristic variables which indicate issues. These variables are chosen carefully based on our experiences, then visualized. As a result, we are able to effectively detect issues. Finally, we discuss the future development for automating log analysis, notification of issues, and disabling problematic sites.

Study of charmed strange baryons at Belle

We report results of a study of charmed strange baryons. The analysis is performed using a 980 fb 1 data sample collected with the Belle detector at the KEKB asymmetric-energy e + e collider. We search for two excited charmed strange baryons, Ξc(3055) + and Ξc(3123) + with Λ + K π + final states through intermediate Σ ++ (2455) or Σ ++ (2520) resonances. The Ξc(3055) + signal is observed with a significance of 6.6 standard deviations incl uding systematic uncertainty, while no signature of the Ξc(3123) + is seen. We also study ΛD +(0) final state. We observe decays of Ξc(3055) +(0) and Ξc(3080) + into ΛD +(0) . This is the first observation of the Ξc(3055) 0 .

Time-of-Propagation Counter for the LEPS

We have tested a time-of-propagation (TOP) counter, which is a ring-image Cherenkov counter utilizing the position and propagation time of the Cherenkov light produced by particles moving in a quartz radiator. Position-sensitive photomultipliers (PMTs) are attached to the end of the quartz bar to detect the produced Cherenkov-ring image. The velocity of the charged particle was determined by comparing the time-of-propagation spectra of the Cherenkov light with the results of Monte Carlo simulation. From analysis of the test experiment using the 1.22-GeV/c electron beam at SPring-8, we determined the velocity of the electron beam to be 1.001 with a resolution of 0.002. On the basis of this study, we suggest a full setup for the detector for separating pions and kaons in the momentum region from 1.5 to 2.0 GeV/c for a beam angle of less than 6°, by more than four standard deviations.

Improvement of the MCP-PMT Performance Under a High Count Rate

A square shape micro-channel-plate photomultiplier tube (MCP-PMT) was developed for the Belle II TOP counter, where the count rate of the MCP-PMT is as high as several MHz/PMT due to the accelerator beam backgrounds. A major problem of the MCP-PMT in such an environment is depression of the quantum efficiency along with the integrated amount of output charge. We succeeded in diminishing the depression significantly by introducing an atomic layer deposition technique and some other processes in the production of the MCP-PMT.

Overview and Highlights of the Belle II Computing

The Belle II is a next-generation B-factory experiment which aims to find the physics beyond the Standard Model with a data sample of 50 ab−1 integrated luminosity. In order to provide computing resources which can process and store such a huge data sample, a distributed computing model is adopted. Nagoya team leads monitoring group in Belle II computing to maximize the active computing resources. Also, we are contacting many Asian universities which have local computing resources to make them join Belle II computing using the method which does not need GRID middleware. In this paper, overview of the Belle II computing and activities of the Nagoya team are described.