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土屋 晴文
Progress of Theoretical and Experimental Physics (Internet), 2026(4), p.043F01_1 - 043F01_23, 2026/04
被引用回数：0Monte Carlo simulations were conducted using the Particle and Heavy Ion Transport code System (PHITS) to investigate the role of secondary cosmic rays in the generation of long-duration bursts from thunderclouds and to clarify the conditions of the electric field region responsible for particle acceleration. The simulations utilized realistic secondary cosmic-ray spectra, including gamma rays, electrons, positrons, and muons, as input. The simulation results indicate that gamma rays provide the dominant supply of seed electrons for long-duration bursts, regardless of the geometry or strength of the electric field region. They also reveal the structure and strength of the electric field region required to produce gamma rays exceeding several tens of MeV, which have so far been detected only by high-altitude observations. Furthermore, the fluxes of long-duration bursts estimated from the simulation results were compared with observational data to constrain the properties of the electric field region. In particular, the comparison with measurements at Yangbajing, located at an altitude of 4.3 km, helps narrow down the possible range of electric field strengths and configurations.
-ray halo beyond 100 TeV雨森 道紘*; 瀧田 正人*; 土屋 晴文; Tibet AS Collaboration*; 他78名*
Science Advances (Internet), 12(10), p.eadv8173_1 - eadv8173_6, 2026/03
被引用回数：0The extended -ray halo surrounding an old pulsar wind nebula (PWN) is an ideal place to investigate both the acceleration and diffusion processes of cosmic rays. In this work, we report the -ray halo observed with high precision by the Tibet AS experiment at the world/s highest-energy above 100 tera-electron volt (TeV). We determined the acceleration limit at about 100 TeV, beyond which the electron/positron flux suppresses exponentially, while we measured the morphology of the -ray halo at three different energies. We also found that the energy dependence of the diffusion coefficient is consistent with the Kolmogorov magnetohydrodynamic (MHD) turbulence and determined the turbulence property at scales smaller than 1 parsec. The measurements indicate that the energy of electrons/positrons is insufficient to amplify the strong MHD turbulence around itself, thereby suppressing the diffusion coefficient.
Guembou Shouop, C. J.; 土屋 晴文
Communications Engineering (Internet), 5, p.11_1 - 11_14, 2026/01
Neutron Resonance Transmission Analysis (NRTA) is a powerful non-destructive assay for material characterisation, traditionally requiring large, fixed and costly facilities. Here, we present a compact NRTA system utilising a small 
Cf spontaneous neutron source to analyse nuclear materials, offering a mobile and cost-effective alternative to accelerator, D-T, or laser-driven neutron sources. The pilot design, with a total size of 130 cm
50 cm50 cm, has an unprecedentedly short flight path of 42 cm, enabling time-of-flight measurements on nuclear material samples. The system's performance is demonstrated through NRTA measurements of simulated samples, including indium, hafnium, and cadmium metal plates. The resulting transmission spectra allow accurate isotope identification below 5 eV. These results underscore the system's potential for enhancing nuclear security, safeguards, and nonproliferation, particularly in scenarios where mobility, rapid deployment, and flexibility are critical. This work is supported by the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT) under the subsidy for the "promotion for strengthening nuclear security and the like."
Cf中性子源を用いた卓上型中性子共鳴透過分析装置の開発土屋 晴文; Guembou Shouop, C. J.
第46回日本核物質管理学会年次大会会議論文集(インターネット), 4 Pages, 2025/12
Neutron Resonance Transmission Analysis (NRTA) is a non-destructive assay capable of identifying and quantifying nuclear materials with high precision, making it a promising tool for applications in nuclear security, safeguards, and non-proliferation. Conventional NRTA systems typically employ accelerators or neutron generators as neutron sources. As a result, they are large, require heavy shielding, and are difficult to implement in facilities with limited space or in field environments. To overcome these limitations, we developed a table-top NRTA system that utilizes a Cf neutron source instead of an accelerator or a neutron generator. The apparatus has dimensions of approximately 130 cm 50 cm 50 cm, enabling easy transport and on-site deployment. Performance tests were conducted using indium and silver plates as surrogate samples for nuclear materials. The experimental transmission spectra exhibited resonance dips consistent with those of expected transmission spectra incorporating the system response function. From these comparisons, the isotopic areal densities were successfully quantified within experimental uncertainty. This study demonstrates, for the first time, that isotope identification and quantitative evaluation can be achieved using a table-top NRTA system without accelerators and neutron generators, and suggests its potential applicability to nuclear facilities, ports, and other space-limited locations.
和田 有希*; Wu, T.*; 鴨川 仁*; Wang, D.*; 岡田 豪*; 南斗 秀仁*; 澤野 達也*; 久保 守*; 米徳 大輔*; Diniz, G. Z.*; et al.
Journal of Geophysical Research; Atmospheres, 130(24), p.e2025JD043927_1 - e2025JD043927_16, 2025/12
被引用回数：0 パーセンタイル：0.00(Meteorology & Atmospheric Sciences)We report two gamma-ray glows observed on December 22, 2023, during a winter thunderstorm in Japan, using an array of four radiation detectors. The first glow, detected by one sensor, was quenched by a lightning discharge. The second glow appeared 2-3 minutes later and was tracked by three other detectors. Radar observations suggest both glows originated from the same thundercloud cell. However, the detection timing of the second glow was inconsistent with simple thundercloud movement, indicating temporal variations in intrinsic glow brightness. A three-dimensional lightning mapping observation suggests that a discharge activity depleted the electric field that generated the first glow, and that the electric field having produced the second glow has been rapidly recovered. In addition, the radar observations also detected a descent of the thundercloud core between the two glows, which may have developed an electrified region and the second glow enough to be observed by the detectors. Tracking gamma-ray glows is crucial for understanding electrified regions in thunderclouds and associated gamma-ray glows.
藤 暢輔; 大図 章; 土屋 晴文; 古高 和禎; 北谷 文人; 米田 政夫; 前田 亮; 小泉 光生
EPJ Web of Conferences, 329, p.06001_1 - 06001_4, 2025/06
被引用回数：1 パーセンタイル：93.90(Physics, Nuclear)There is no acceptable and practicable single nondestructive method for the assay of Special Nuclear Materials (SNM) and Minor Actinides (MA) in highly radioactive nuclear materials. The Japan Atomic Energy Agency (JAEA) and the Joint Research Centre (JRC) of the European Commission have been developing an active neutron nondestructive assay (NDA) system for nuclear non-proliferation and nuclear security. We utilize four different NDA techniques, namely Differential Die-Away Analysis (DDA), Prompt Gamma-ray Analysis (PGA), Neutron Resonance Transmission Analysis (NRTA) and Delayed Gamma-ray Analysis (DGA). The techniques give us different and useful analytical results, which could provide complementary information. We developed a combined NDA system, which enables the simultaneous measurements of DDA and PGA in the first phase of the collaboration. The improved DDA is possible to quantify a small amount of the fissile mass as low as 1mg (Pu-239). In the second phase, we developed an advanced NDA system which allows us to measure by NRTA as well as DDA and PGA. The third phase has started to study a compact NRTA system from 2022 for four years. NRTA would be the most promising method for highly radioactive nuclear materials. An overview of the projects and the recent results will be presented. This research was implemented under the subsidiary for nuclear promotion of MEXT (the Ministry of Education, Culture, Sports, Science and Technology of Japan).
和田 有希*; 森本 健志*; Wu, T.*; Wang, D.*; 菊池 博史*; 中村 佳敬*; 吉川 英一*; 牛尾 知雄*; 土屋 晴文
Science Advances (Internet), 11(21), p.eads6906_1 - eads6906_10, 2025/05
被引用回数：1 パーセンタイル：0.00(Multidisciplinary Sciences)Lightning discharges can produce transient gamma-ray emissions called terrestrial gamma-ray flashes (TGFs), which originates from electrons accelerated to relativistic energies in strong electric fields. However, it is not yet understood how lightning produces an enormous number of relativistic electrons in dense atmospheres. We present that, thanks to a ground-based observation with optical, radio frequency and high-energy measurements focused on television transmission towers in Kanazawa, Japan, a TGF and a cloud-to-ground discharge of 
kA occurred when a downward negative leader was colliding with an upward positive leader from the tower. Because the cloud-to-ground current followed the TGF by 30 
s, the TGF started when two leaders approached each other. Our results indicate that an immense number of electrons were produced and accelerated to relativistic energies in a strong and compact electric-field region between the two leaders.
Guembou Shouop, C. J.; 土屋 晴文
Nuclear Instruments and Methods in Physics Research A, 1072, p.170189_1 - 170189_14, 2025/03
被引用回数：5 パーセンタイル：73.33(Instruments & Instrumentation)The development of a compact mobile neutron resonance transmission analysis (NRTA) instrument is in progress for measuring nuclear materials in the field of nuclear nonproliferation and nuclear security. The present paper focuses on research/developments on designing the source, moderators and shielding for the table-top NRTA system utilising a Cf spontaneous neutron. To this end, three source configurations were assessed using Monte Carlo (MC) simulations-based Particle and Heavy Ion Transport code System (PHITS) by evaluating each configuration's neutron/gamma fluxes. Experimental validation of the MC simulation was conducted using an EJ270 plastic scintillation detector, a 
Bq Cf source, and a thin In sample. The Monte Carlo simulations and experimental results confirmed that an optimal configuration for the table-top NRTA system involves sandwiching the Cf source between the polyethylene (PE) moderator (PE closer to the detector) and the W reflector. Furthermore, the MC simulations showed that resonance dips from NatU and Pu (energy lines of 1.06 and 2.60 eV of 
Pu and 0.30 eV of 
Pu) can be observed in the Time-of-Flight spectra obtained using the table-top NRTA system with an appropriate collimator for a small pellet sample. The preliminary experimental results with a 2 mm thick In sample displayed the 1.46 eV resonance dip of 
In, showing that the table-top NRTA system using a Cf neutron source can measure TOF spectra and observe dips caused by low energy resonances in a sample. These findings suggest the system is well-suited for measuring small pellet samples of Pu and U.
土屋 晴文; 日比野 欣也*; 川田 和正*; 大西 宗博*; 瀧田 正人*; 宗像 一起*; 加藤 千尋*; 霜田 進*; Shi, Q.*; Wang, S.*; et al.
Progress of Earth and Planetary Science (Internet), 11, p.26_1 - 26_14, 2024/05
被引用回数：2 パーセンタイル：0.00(Geosciences, Multidisciplinary)From 1998 to 2017, neutron monitors located at an altitude of 4300 m on the Tibetan plateau detected 127 long-duration bursts of high-energy radiation in association with thunderclouds. These bursts typically lasted for 10-40 min, and 89% of them occurred between 10:00 and 24:00 local time. They were also found to be more likely to occur at night, especially during 18:00-06:00 local time period. The observed diurnal and seasonal variations in burst frequency were consistent with the frequencies of lightning and precipitation on the Tibetan plateau. Based on 19 years of data, the present study suggests that an annual variation in burst frequency has a periodicity of 
16 years and a lag of 3 years relative to solar activity.
和田 有希*; 鴨川 仁*; 久保 守*; 榎戸 輝揚*; 林 省吾*; 澤野 達也*; 米徳 大輔*; 土屋 晴文
Journal of Geophysical Research; Atmospheres, 128(21), p.e2023JD039354_1 - e2023JD039354_20, 2023/11
被引用回数：4 パーセンタイル：31.82(Meteorology & Atmospheric Sciences)During the 2020-2021 winter season, we detected 6 gamma-ray glows at Kanazawa University, Japan. Negative surface electric fields (E-fields) were observed by a field mill during all the glow cases. In five of the six cases, the maximum E-field reached 
kV m
, and the E-field during the glow detection was the strongest in 3 hours before and after the detection time. Therefore, negative charges should have been dominant in the thunderclouds that produced the gamma-ray glows, and electrons were probably accelerated and multiplied by the E-fields between a predominantly negative charge layer and a localized positive charge layer below. In addition, we extracted 8 non-detection cases in the 2020-2021 winter season, in which surface E-fields were stronger than kV m. In 5 of the 8 cases, radar echoes were inadequately developed, suggesting insufficient charge accumulation. On the other hand, the remaining 3 cases had well-developed radar echoes, and there was no significant difference from the detection cases.
土屋 晴文; 藤 暢輔; 大図 章; 古高 和禎; 北谷 文人; 前田 亮; 米田 政夫
Journal of Nuclear Science and Technology, 60(11), p.1301 - 1312, 2023/11
被引用回数：6 パーセンタイル：71.79(Nuclear Science & Technology)An integrated active neutron non-destructive analysis (NDA) system, Active-N, was developed to gain knowledge of active neutron NDA techniques that are applicable to measurements of nuclear materials in highly radioactive nuclear fuels. Active-N, equipped with a D-T neutron generator, combines three complementary active neutron NDA techniques: Differential Die-away Analysis (DDA), Prompt Gamma-ray Analysis (PGA), and Neutron Resonance Transmission Analysis (NRTA). In this paper, we provide an overview of Active-N and then demonstrate that the compact NRTA system in Active-N can quantify nuclear materials. Monte Carlo simulations were conducted to determine the design of the compact NRTA system including a moderator, flight tubes, and a detector shield. To investigate how accurately the compact NRTA system determines areal densities in a sample, measurements were performed with a Pu pellet-type sample as well as metallic plate samples of In and Ag. The experimental areal densities of Pu, In and 
Ag were consistent with those calculated for the individual nuclei. These results show that it is feasible to develop a compact NRTA system capable of determining the contents of nuclear materials in nuclear fuels. This research was implemented under the subsidy for nuclear security promotion of MEXT.
雨森 道紘*; 土屋 晴文; Tibet AS Collaboration*; 他116名*
Astrophysical Journal, 954(2), p.200_1 - 200_7, 2023/09
被引用回数：7 パーセンタイル：50.38(Astronomy & Astrophysics)Gamma rays from HESS J1849-000, a middle-aged TeV pulsar wind nebula (PWN), are observed by the Tibet air shower array and the muon detector array. The detection significance of gamma rays reaches 
and 
levels above 25 TeV and 100 TeV, respectively. The energy spectrum measured between 40 TeV 
E 320 TeV for the first time is described with a simple power-law function of dN/dE = 
. The gamma-ray energy spectrum from the sub-TeV to sub-PeV ranges including the results of previous studies can be modeled with the leptonic scenario, Inverse Compton Scattering by high-energy electrons accelerated by the PWN of PSR J1849-0001, but the scenario requires sophisticated theoretical modeling. On the other hand, the gamma-ray energy spectrum can be simply modeled with the hadronic scenario in which gamma rays are generated from the decay of neutral pions produced by collisions between accelerated cosmic-ray protons and the ambient molecular cloud found in the gamma-ray emitting region. The cutoff energy of cosmic-ray protons 
is estimated at 
, suggesting that protons are accelerated up to the PeV energy range. Our study proposes that HESS J1849-000 should be further investigated as a new candidate for a Galactic PeV cosmic-ray accelerator, or "PeVatron".
和田 有希*; Wu, T.*; Wang, D.*; 榎戸 輝揚*; 中澤 知洋*; 森本 健志*; 中村 佳敬*; 篠田 太郎*; 土屋 晴文
Journal of Geophysical Research; Atmospheres, 128(15), p.e2023JD038606_1 - e2023JD038606_9, 2023/08
被引用回数：5 パーセンタイル：39.69(Meteorology & Atmospheric Sciences)A gamma-ray glow, a minute-lasting burst of high-energy photons from a thundercloud, was detected by ground-based apparatus at Kanazawa University, Japan, in a winter thunderstorm on 18 December 2018. The gamma-ray glow was quenched by a lightning flash within a brief time window of 40 ms. The lightning flash produced several low-frequency (LF) E-change pulses that were temporally coincident withthe termination of the gamma-ray glow, and that were located within 0.5 km from the observation site by the Fast Antenna Lightning Mapping Array. The LF pulses had the same polarity as a positive cloud-to-ground current and a normal-polarity in-cloud current. Since this polarity is against the upward electric field for producing the gamma-ray glow (accelerating electrons to the ground), we infer that the glow was terminated by a normal-polarity in-cloud discharge activity between a middle negative layer and an upper positive layer.
鶴見 美和*; 榎戸 輝掲*; 一方井 祐子*; Wu, T.*; Wang, D.*; 篠田 太郎*; 中澤 知洋*; 辻 直樹*; Diniz, G.*; 片岡 淳*; et al.
Geophysical Research Letters, 50(13), p.e2023GL103612_1 - e2023GL103612_9, 2023/07
被引用回数：13 パーセンタイル：75.44(Geosciences, Multidisciplinary)Gamma-ray glows are observational evidence of relativistic electron acceleration due to the electric field in thunderclouds. However, it is yet to be understood whether such relativistic electrons contribute to the initiation of lightning discharges. To tackle this question, we started the citizen science "Thundercloud Project," where we map radiation measurements of glows from winter thunderclouds along Japan's sea coast area. We developed and deployed 58 compact gamma-ray monitors at the end of 2021. On 30 December 2021, five monitors simultaneously detected a glow with its radiation distribution horizontally extending for 2 km. The glow terminated coinciding with a lightning flash at 04:08:34 JST, which was recorded by the two radio-band lightning mapping systems, FALMA and DALMA. The initial discharges during the preliminary breakdown started above the glow, that is, in vicinity of the electron acceleration site. This result provides one example of possible connections between electron acceleration and lightning initiation.
和田 有希*; 松本 崇弘*; 榎戸 輝揚*; 中澤 知洋*; 湯浅 孝行*; 古田 禄大*; 米徳 大輔*; 澤野 達哉*; 岡田 豪*; 南戸 秀仁*; et al.
Physical Review Research (Internet), 3(4), p.043117_1 - 043117_31, 2021/12
In 2015 the Gamma-Ray Observation of Winter Thunderstorms (GROWTH) collaboration launched a mapping observation campaign for high-energy atmospheric phenomena related to thunderstorms and lightning discharges. This campaign has developed a detection network of gamma rays with up to 10 radiation monitors installed in Kanazawa and Komatsu cities, Ishikawa Prefecture, Japan, where low-charge-center winter thunderstorms frequently occur. During four winter seasons from October 2016 to April 2020, in total 70 gamma-ray glows, minute-lasting bursts of gamma rays originating from thunderclouds, were detected. Their average duration is 58.9 sec. Among the detected events, 77% were observed in nighttime. The gamma-ray glows can be classified into temporally-symmetric, temporally-asymmetric, and lightning-terminated types based on their count-rate histories. An averaged energy spectrum of the gamma-ray glows is well fitted with a power-law function with an exponential cutoff, whose photon index, cutoff energy, and flux are 0.613 
0.009, 4.68 0.04 MeV, and (1.013 0.003) 10
erg cm
s (0.2-20.0 MeV), respectively. The present paper provides the first catalog of gamma-ray glows and their statistical analysis detected during winter thunderstorms in the Kanazawa and Komatsu areas.
久富 章平*; 中澤 知洋*; 和田 有希*; 辻 結菜*; 榎戸 輝揚*; 篠田 太郎*; 森本 健志*; 中村 佳敬*; 湯浅 孝行*; 土屋 晴文
Journal of Geophysical Research; Atmospheres, 126(18), p.e2021JD034543_1 - e2021JD034543_12, 2021/09
被引用回数：24 パーセンタイル：75.66(Meteorology & Atmospheric Sciences)Around 17:00 on January 12, 2020 (UTC), radiation detectors installed at two locations with a 1.35 km separation in Kanazawa City, Japan, captured a total of four gamma-ray enhancements. The first pair was simultaneously observed at the two locations at 17:03 and were abruptly terminated by a lightning discharge. The remaining two enhancements were also nearly simultaneously observed 3 min later, and one of them was also terminated by another lightning discharge. At the last termination, a downward terrestrial gamma-ray flash and a negative energetic in-cloud pulse were observed. Both pairs were associated with thundercloud cells. In the first pair, simultaneous detection in two locations 1.35 km apart suggests either a gamma-ray glow emerged in-between and time variability of its intensity were directly observed or there were two (or more) gamma-ray glows in the cell which reached the two detectors coincidentally. In the latter pair, the peak time in the downwind detector was 40 s later than that of the upwind detector. If the irradiation region moved with the cell, it would have taken 110 s. The discrepancy suggests either the glow moved 2.5 times faster than the cell or there were two (or more) glows in the cell. Also, the fact that the thunderstorm cell hosting the latter glows experienced the lightning discharge 3 min before suggests that the strong electric field in the cell can develop within a few minutes.
藤 暢輔; 大図 章; 土屋 晴文; 古高 和禎; 北谷 文人; 米田 政夫; 前田 亮; 小泉 光生
Proceedings of INMM & ESARDA Joint Virtual Annual Meeting (Internet), 8 Pages, 2021/08
Since neutrons have exceptional ability to penetrate high-density materials and can induce fission, they are used in non-destructive analysis such as, Differential Die-Away Analysis (DDA), Prompt Gamma-ray Analysis (PGA) and Neutron Resonance Transmission Analysis (NRTA). The different analytical methods give us complementary information, which are particularly useful for the quantification of Special Nuclear Materials in highly radioactive nuclear materials, including spent fuel. The Japan Atomic Energy Agency (JAEA) and the Joint Research Centre (JRC) of the European Commission are collaborating to develop an active neutron NDA system for nuclear non-proliferation and nuclear security. In the second phase of the project, an integrated active neutron NDA system: Active-N which enables the simultaneous measurements of DDA, PGA and NRTA has been developed. The DDA detects fission neutrons, and it can determine small amounts of the fissile mass. PGA is utilized for the quantification of neutron absorber and particularly useful for the detection of explosives. NRTA can be used to quantify almost all medium and high-Z elements and considered as one of the most accurate NDA. In this presentation, we will provide an overview of Active-N and report the recent experimental results. This research was implemented under the subsidy for nuclear security promotion of MEXT: Ministry of Education, Culture, Sports, Science and Technology.
雨森 道紘*; 土屋 晴文; Tibet AS
Collaboration*; 他111名*
Physical Review Letters, 127(3), p.031102_1 - 031102_6, 2021/07
被引用回数：22 パーセンタイル：79.57(Physics, Multidisciplinary)We report observations of gamma-ray emissions with energies in the 100-TeV energy region from the Cygnus region in our Galaxy. Two sources are significantly detected in the directions of the Cygnus OB1 and OB2 associations. Based on their positional coincidences, we associate one with a pulsar PSR J2032 + 4127 and the other mainly with a pulsar wind nebula PWN G75.2 + 0.1, with the pulsar moving away from its original birthplace situated around the centroid of the observed gamma-ray emission. This work would stimulate further studies of particle acceleration mechanisms at these gamma-ray sources.
土屋 晴文; 榎戸 輝揚*; 和田 有希*; 古田 禄大; 中澤 知洋*; 湯浅 孝行*; 楳本 大悟*; 牧島 一夫*; GROWTH Collaboration*
Proceedings of Science (Internet), 358, p.1163_1 - 1163_6, 2021/07
Since 2006, the GROWTH experiment has been successfully operating at the coastal area of Japan Sea. The GROWTH experiment aims at elucidating how particles in lightning and thunderclouds are accelerated to relativistic energies to produce gamma rays and occasionally neutrons. According to observations done by the GROWTH experiment, it is found that there are two types of radiation bursts associated with winter thunderstorms. One is long bursts lasting for a few tens of seconds to a few minutes, being not clearly related to lightning. The other is short bursts in association with lightning. To better understand the production mechanism of these radiation bursts, we have developed a small-type of radiation detectors and increased observational points with the new detectors. In this presentation, we show an overview of observations done by the GROWTH experiment. Then we focus on recent several findings observed by the new detectors. One, which is categorized into long bursts, implies a relationship between a long burst and an intra/inter-cloud discharge. Another is a combination of short bursts and long ones, showing simultaneous detections of prompt gamma rays extending up to 10 MeV and the 511-keV annihilation ones. These gamma-ray signals demonstrate the occurrence of photonuclear reactions in lightning. Based on these results, we discuss the production mechanism of gamma rays related to thunderstorms.
雨森 道紘*; 土屋 晴文; Tibet AS Collaboration*; 他93名*
Nature Astronomy (Internet), 5(5), p.460 - 464, 2021/05
被引用回数：84 パーセンタイル：97.21(Astronomy & Astrophysics)Cosmic rays (protons and other atomic nuclei) are believed to gain energies of petaelectronvolts (PeV) and beyond at astrophysical particle accelerators called "PeVatrons" inside our Galaxy. Although a characteristic feature of a PeVatron is expected to be a hard gamma-ray energy spectrum that extends beyond 100 teraelectronvolts (TeV) without a cut-off, none of the currently known sources exhibit such a spectrum owing to the low maximum energy of accelerated cosmic rays or owing to insufficient detector sensitivity around 100 TeV. Here, we report the observation of gamma-ray emission from the supernova remnant G106.3+2.7 above 10 TeV. This work provides flux data points up to and above 100 TeV and indicates that the very-high-energy gamma-ray emission above 10 TeV is well correlated with a molecular cloud rather than with the pulsar PSR J2229+6114. Regarding the gamma-ray emission mechanism of G106.3+2.7, this morphological feature appears to favour a hadronic origin via the 
decay caused by accelerated relativistic protons over a leptonic origin via the inverse Compton scattering by relativistic electrons. Furthermore, we point out that an X-ray flux upper limit on the synchrotron spectrum would provide important information to firmly establish the hadronic scenario as the mechanism of particle acceleration at the source.
