Alpha-decay events in a nuclear emulsion are standard calibration sources for the relation between the track length and the kinetic energy in each emulsion sheet. We developed an efficient classifier ...that sorts such alpha-decay events from various vertex-like objects in an emulsion using a convolutional neural network (CNN). We trained the CNN using 15885 images of vertex-like objects, including 906 alpha-decay events, and tested it using a dataset of 46948 images including 255 alpha-decay events. The precision and recall scores of the classification using the previous method without a CNN for the same dataset were 0.081 ± 0.006 and 0.788 ± 0.056, respectively. In contrast, our trained models achieved an average precision score of 0.760 ± 0.006 for the test dataset, after extensively tuning the hyperparameters of the CNN. Moreover, for the model obtained, the discrimination threshold of the classification can be adjusted arbitrarily according to the trade-off between the precision and recall scores. Furthermore, the developed classifier obtained a precision of 0.571 ± 0.017 when the recall score was assigned a value of 0.788. Finally, the developed CNN method reduced the need for additional human visual inspection, required after classification, by a factor of approximately 1/7, compared to the former method without a CNN, proving the feasibility of the proposed classifier.
We revisit previous measurements for the hypertriton binding energy with nuclear emulsion which were published in 1968 and 1973. Using Monte Carlo simulations, the systematic error of the hypertriton ...binding energy in emulsion measurements has been estimated to be approximately 28 keV. We corroborate the recent works that re-evaluate the hypertriton binding energy by using the former emulsion measurements in the present work, and the ambiguities and difficulties of the reevaluation are observed. Considering the need of new precise measurements with a well-controlled systematic error, we introduce a new approach by analyzing the existing nuclear emulsion data from the J-PARC E07 experiment, from which the binding energy of hypertriton could be determined, with both statistical and systematic errors, to be approximately 30 keV with 400 events.
Ξ
−
atomic X-ray spectroscopy is one of the most useful methods for investigation of the Ξ-nucleus strong interaction. A serious problem in the measurement is the significant background coming from ...in-flight Ξ
−
decay. For the first Ξ
−
atomic X-ray spectroscopy experiment, a novel method of identifying stopped Ξ
−
events using nuclear emulsion was developed to reject background photons from in-flight Ξ
−
decay. We succeeded in reducing the background to 1/170 by this method employing coincidence measurements using the nuclear emulsion and X-ray detectors.
Abstract
Ξ− atomic X-ray spectroscopy is one of the most useful methods for investigation of the Ξ–nucleus strong interaction. Since the X-ray energy is shifted and/or broadened due to the Ξ–nucleus ...strong interaction compared to those calculated from electromagnetic interaction alone, the measurement of the energy shift, ΔE, and the width, Γ, give us information on the Ξ–nucleus potential. A serious problem in the measurement is the significant background derived from in-flight Ξ− decay. A novel method of identifying stopped Ξ− events using the nuclear emulsion was developed to realize the first Ξ− atomic X-ray spectroscopy experiment as the J-PARC E07 experiment, which also aimed at searching for ΛΛ and Ξ− hypernuclei in the emulsion. The X-rays emitted from Ξ− Br and Ξ− Ag atoms were measured using germanium detectors. No clear peaks were observed in the obtained spectra. However, we succeeded in reducing the background to 1/170 by this method employing coincidence measurements using nuclear emulsion and X-ray detectors.
A high-resolution measurement method based on X-ray microscopy was developed to analyze double-strangeness hypernuclear events with a complex topology in a nuclear emulsion. In a feasibility study ...performed on
α
-decay events in emulsions, the resolution of the X-ray microscopy in the focal plane was found to be 0.2
μ
m
, which shows an improvement by
∼
2.4
times to that of the optical microscopy used for conventional analysis. The extent to which the emulsion underwent modification as a result of X-ray irradiation was also evaluated. The modification mainly occurred in the form of a change in its thickness; however, this affection was adequately small to perform X-ray imaging if the duration of the irradiation was sufficiently short. Stereo imaging with X-ray microscopy improved the resolution by
∼
2.5
times to 0.28
μ
m
along the optical axis compared with the depth of field of the optical microscope, 0.7
μ
m
. We applied the developed method to the study of a double-strangeness hypernuclear event. The uncertainty on the position of the vertex point and the binding energy of the
Ξ
-
and
14
N system was improved from 3
μ
m
to 0.04
μ
m
and
±
3
MeV to
±
0.86
MeV, respectively. The binding energy was deduced to be
-
1.23
±
0.86
MeV
, and this result indicates that a
Ξ
-
atomic state is produced in the observed event.
This study developed a novel method for detecting hypernuclear events recorded in nuclear emulsion sheets using machine learning techniques. The artificial neural network-based object detection model ...was trained on surrogate images created through Monte Carlo simulations and image-style transformations using generative adversarial networks. The performance of the proposed model was evaluated using α-decay events obtained from the J-PARC E07 emulsion data. The model achieved approximately twice the detection efficiency of conventional image processing and reduced the time spent on manual visual inspection by approximately 1/17. The established method was successfully applied to the detection of hypernuclear events. This approach is a state-of-the-art tool for discovering rare events recorded in nuclear emulsion sheets without any real data for training.
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