Y. Nakatsuka

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.

A Test Experiment to Develop a Neutrino Detector with Emulsions for Neutrino-Nucleus Cross Section Measurements at J-PARC

We would like to perform a test experiment to develop a new neutrino detector with nuclear emulsions at the near detector hall of the J-PARC neutrino beam line. The physics aim is to detect neutrino interactions with high efficiency and measure the cross sections of neutrino (νμ/νμ, νe/νe)-nucleus charged/neutral current interactions in around 1 GeV energy region. First, we will perform a preliminary run to study environmental background inside the near detector hall. Then, we will perform a test run to study performance of the new detector and establish the analysis method to study neutrino interactions in the low energy region. Finally, we will perform data taking of physics runs to measure cross sections of neutrino-nucleus interactions with high efficiency.

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

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