K. Ishiguro

Comprehensive track reconstruction tool "NETSCAN 2.0'' for the analysis of the OPERA Emulsion Cloud Chamber

NETSCAN is a track reconstruction algorithm used in Emulsion Cloud Chambers (ECC). NETSCAN and Emulsion Cloud Chambers were used in the DONUT experiment to detect Tau-neutrinos interactions. The algorithm has been revised in order to cope with the OPERA event analysis performed in Japan. A new version of NETSCAN was necessary to effectively analyze the most massive emulsion experiment in history with limited resources.

Development and utilization of ``Plate Changer'' system for neutrino interaction locations in OPERA emulsion target

In the OPERA experiment, so-called Scan Back method is used to locate neutrino interaction vertices in the emulsion target named ECC (Emulsion Cloud Chamber). In Scan Back method, tracks detected in the most downstream emulsion plate in ECCs are followed to upstream plate by plate until it reaches to the interaction points. In order to treat a number of neutrino interactions recorded in OPERA, dedicated systems called Plate Changer has been developed and utilized to neutrino event location in Japan. The details of the system have been described in this report. Until the end of November 2012, 6223 Scan Back trials have been performed using this system, and strongly contributed to the detection of tau neutrino appearance.

First neutrino event detection with nuclear emulsion at J-PARC neutrino beamline

Precise neutrino–nucleus interaction measurements in the sub-multi-GeV region are important to reduce the systematic uncertainty in future neutrino oscillation experiments. Furthermore, an excess of νe interactions, as a possible interpretation of the existence of a sterile neutrino, has been observed in such an energy region. The nuclear emulsion technique can measure all the final state particles with low energy threshold for a variety of targets (Fe, C, H2O, and so on). Its sub- μm position resolution allows measurements of the νe cross-section with good electron/gamma separation capability. We started a new experiment at J-PARC to study sub-multi-GeV neutrino interactions by introducing the nuclear emulsion technique. The J-PARC T60 experiment has been implemented as a first step in such a project. Systematic neutrino event analysis with full scanning data in the nuclear emulsion detector was performed for the first time. The first neutrino event detection and its analysis are described in this paper.

First demonstration of gamma-ray imaging using a balloon-borne emulsion telescope

We promote the precise gamma-ray observation project Gamma-Ray Astro-Imager with Nuclear Emulsion (GRAINE), which uses balloon-borne emulsion gamma-ray telescopes. The emulsion telescope realizes observations with high angular resolution, polarization sensitivity, and large aperture area in the 0.01--100 GeV energy region. Herein, we report the data analysis of emulsion tracks and the first demonstration of gamma-ray imaging via an emulsion telescope by using the flight data from the balloon experiment performed in 2015 (GRAINE 2015). The emulsion films were scanned by the latest read-out system for a total area of 41 m

First demonstration of an emulsion multi-stage shifter for accelerator neutrino experiments in J-PARC T60

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GRAINE 2015, a balloon-borne emulsion

in three months, and then the gamma-ray event selection was automatically processed. Millions of electron-pair events are accumulated in the balloon-borne emulsion telescope. The emulsion telescope detected signals from a calibration source (gamma rays from the interaction of cosmic rays with an aluminum plate) with a high significance during the balloon observation and created a gamma-ray image consistent with the source size and the expected angular resolution in the energy range of 100--300 MeV. The flight performance obtained in the GRAINE 2015 experiment proves that balloon-borne emulsion telescope experiments with larger area are feasible while maintaining expected imaging performance.

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We describe the first ever implementation of an emulsion multi-stage shifter in an accelerator neutrino experiment. The system was installed in the neutrino monitor building in J-PARC as a part of a test experiment T60 and stable operation was maintained for a total of 126.6 days. By applying time information to emulsion films, various results were obtained. Time resolutions of 5.3 to 14.7 s were evaluated in an operation spanning 46.9 days (time resolved numbers of 3.8--1.4