Wide angle acceptance and high-speed track recognition in nuclear emulsion

A nuclear emulsion film is a three-dimensional tracking device that is widely used in cosmic-ray and high energy physics experiments. Scanning with a wide angle acceptance is crucial for obtaining track information in emulsion films. This study presents a new method developed for wide angle acceptance and high-speed track recognition of nuclear emulsion films for neutrino-nucleus interaction measurements. The nuclear emulsion technique can be used to measure tracks of charged particles from neutrino interactions with a low momentum threshold. The detection of the particles with a wide angle acceptance is essential for obtaining detailed information on the interactions in the sub- and multi-GeV neutrino energy region. In the new method developed for a neutrino interaction measurement in J-PARC called NINJA, the angle acceptance is covered up to $|\tan\theta_{x(y)}| < 5.0$ (80% of all solid angles) with $150\,\mathrm{m^2/year}$. This method can also be used to improve the angle accuracy and recognition efficiency of the tracks.