Observation techniques of high-energy gamma rays using air showers have remarkably progressed via the Tibet AS
γ
, HAWC, and LHAASO experiments. These observations have significantly contributed to ...gamma-ray astronomy in the northern sky’s sub-PeV region. Moreover, in the southern sky, the ALPACA experiment is underway at 4,740 m altitude on the Chacaltaya plateau in Bolivia. This experiment estimates the gamma-ray flux from the difference between the number of on-source and off-source events by real data, utilizing the gamma-ray detection efficiency calculated through Monte Carlo simulations, which in turn depends on the hadronic interaction models. Even though the number of cosmic-ray background events can be experimentally estimated, this model dependence affects the estimation of gamma-ray detection efficiency. However, previous reports have assumed that the model dependence is negligible and have not included it in the error of gamma-ray flux estimation. Using ALPAQUITA, the prototype experiment of ALPACA, we quantitatively evaluated the model dependence on hadronic interaction models for the first time. We evaluate the model dependence on hadronic interactions as less than 3.6 % in the typical gamma-ray flux estimation performed by ALPAQUITA; this is negligible compared with other uncertainties such as energy scale uncertainty in the energy range from 6 to 300 TeV, which is dominated by the Monte Carlo statistics. This upper limit of 3.6 % model dependence is expected to apply to ALPACA.
The ALPACA experiment is a new international project between Bolivia and Japan. It is going to consist of an 83,000 m2 surface air-shower array and a 5,400 m2 underground water Cherenkov muon ...detector array, and the experimental site is at Mt. Chacaltaya plateau at an altitude of 4,740 m. Its main target is to observe 100 TeV gamma rays and explore high-energy gamma-ray sources in the southern sky. This is because such high-energy gamma rays hold the key to identify the origin of cosmic rays at the knee region of the energy spectrum. So far many high-energy gamma-ray sources have been found in the southern sky. They are emitting gamma rays of several tens of TeV, so some of them could be PeVatrons which accelerate cosmic rays to PeV energy region in the Galaxy. By observing them in higher energy region, we will obtain new knowledge of cosmic-ray acceleration to the knee region, and discover new gamma-ray sources. As the prototype experiment of ALPACA, the ALPAQUITA experiment is now under construction. In a MC simulation, we found that ALPAQUITA has the ability of detecting bright gamma-ray sources in the southern hemisphere such as Vela X within 1 year.
Aromatase is one of the key estrogen-producing enzymes and is regarded as one of the therapeutic targets in estrogen receptor-positive breast cancer patients. Human colon carcinoma has also been ...recently proposed as being an estrogen-responsive malignancy, but the detailed status of aromatase has not yet been reported. Therefore, in this study, we evaluated the aromatase expression in colon carcinoma using immunohistochemistry and real-time polymerase chain reaction. Aromatase mRNA was significantly higher (p=0.03) in colon carcinoma than in the corresponding non-neoplastic mucosa (n=31). Aromatase immunoreactivity tended to be positively associated with the intratumoral concentration of estrogens (n=53), and in particular, the concentration of estradiol was significantly higher (p=0.02) in aromatase-positive cases in men. Aromatase immunoreactivity was detected in the cytoplasm of the carcinoma cells in 217/328 (65%) examined colon carcinoma cases. Aromatase immunoreactivity was significantly positively correlated with tubular differentiation, and inversely correlated with Ki-67 labeling index, although not necessarily correlated with the clinical outcome of the patients. All these results demonstrate that colon carcinoma expresses functional aromatase, and that estrogens are locally synthesized in the tumor tissues. The findings reported here could contribute to a better understanding of the actions of estrogen in colon carcinoma.
We analyze the large-scale two-dimensional sidereal anisotropy of multi-TeV cosmic rays (CRs) by the Tibet Air Shower Array, with the data taken from 1999 November to 2008 December. To explore ...temporal variations of the anisotropy, the data set is divided into nine intervals, each with a time span of about one year. The sidereal anisotropy of magnitude, about 0.1%, appears fairly stable from year to year over the entire observation period of nine years. This indicates that the anisotropy of TeV Galactic CRs remains insensitive to solar activities since the observation period covers more than half of the 23rd solar cycle.
We have upgraded the new Tibet ASgamma experiment in China since 2014 to measure the chemical composition of cosmic rays around the knee. This hybrid experiment consist of an air-shower-core detector ...array (YAC-II) to detect high energy electromagnetic component, the Tibet air-shower array (Tibet-III) and a large underground water-Cherenkov muon-detector array (MD). We have carried out a detailed air-shower Monte Carlo (MC) simulation to study the performance of the hybrid detectors by using CORSIKA (version 7.5000), which includes EPOS-LHC, QGSJETII-04, SIBYLL2.1 and SIBYLL2.3 hadronic interaction models. The preliminary results of the interaction model checking above 50 TeV energy region are reported in this paper, and the primary proton and helium spectra in the energy range 50 TeV to 10
15
eV was derived from YAC-I data and is smoothly connected with direct observation data at lower energies and also with our previously reported works at higher energies within statistical errors. The knee of the (P+He) spectra is located around 400 TeV. The interaction model dependence in deriving the primary (P+He) spectra is found to be small (less than 25% in absolute intensity, 10% in position of the knee), and the composition model dependence is less than 10% in absolute intensity.
A hybrid experiment has been started by the ASγ experiment at Yangbajing (4300m a.s.l.) in Tibet since May 2009, that consists of a high-energy air-shower-core array (YAC-I) and a high-density ...air-shower array (Tibet-III). In this paper, we report our results to check the hadronic interaction models SIBYLL2.3, SIBYLL2.1, EPOS-LHC and QGSJETII-04 in the multi-tens TeV energy region using YAC-I+Tibet-III experimental data from May 2009 through January 2010. The effective live time is calculated as 106.05 days. The results show that the description of transverse momentum, inelastic cross-section and inelasticity for the 4 hadronic interaction models is consistent with YAC-I experimental data within 15% systematic errors range in the forward region below 100 TeV. Among them, the EPOS-LHC model is the best hadronic interaction model. Furthermore, we find that the H4a composition model is the best one below the 100 TeV energy region.
For observations of cosmic gamma rays of several TeV or more, many experimental groups conduct ground-based air shower observation experiments. New projects such as Andes Large area PArticle detector ...for Cosmic ray physics and Astronomy (ALPACA) are also underway. In these experiments, an accurate trigger time measurement system is required when sudden cosmic phenomena are observed. To record such sudden astronomical phenomena, we have developed an event-trigger time recording system that accurately measures the arrival times of air showers. The system consists of a commercial global navigation satellite system module, a high-precision clock, a multi-hit type time-to-digital converter with a reset function for accurate time measurement, and a network-time-protocol server installed on a computer. It was confirmed that the time accuracy compared to UTC was approximately 1μs, and the time deviation was approximately 11.4 ns with one standard deviation. The developed system is versatile and can also be used for the ALPACA experiment. It is expected that the time accuracy of this system can be improved to approximately ±40 ns.
We analyze the temporal variation of the solar diurnal anisotropy of the multi-TeV cosmic-ray intensity observed with the Tibet air shower array from 2000 to 2009, covering the maximum and minimum of ...the 23rd solar cycle. We comfirm that a remarkable additional anisotropy component is superposed on the Compton-Getting anisotropy at 4.0 TeV, while its amplitude decreases at higher energy regions. In constrast to the additional anisotropy reported by the Matsushiro experiment at 0.6 TeV, we find the residual component measured by Tibet at multi-TeV energies is consistent with being stable, with a fairly constant amplitude of 0.041% ± 0.003% and a phase at around 07.17 ± 00.16 local solar time at 4.0 TeV. This suggests the additional anisotropy observed by the Tibet experiment could result from mechanisms unrelated to solar activities.
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