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R. Enomoto

Publications and source records attributed to R. Enomoto.

33 records · Page 2Linked to original sources
arXiv2002

Detection of diffuse TeV gamma-ray emission from the nearby starburst galaxy NGC 253

We report the TeV gamma-ray observations of the nearby normal spiral galaxy NGC 253. At a distance of $\sim$2.5 Mpc, NGC 253 is one of the nearest starburst galaxies. This relative closeness, coupled with the high star formation rate in the galaxy, make it a good candidate TeV gamma-ray source. Observations were carried out in 2000 and 2001 with the CANGAROO-II 10 m imaging atmospheric Cerenkov telescope. TeV gamma-ray emission is detected at the $\sim 11σ$ level with a flux of $(7.8 \pm 2.5)\times 10^{-12} {\rm cm}^{-2} {\rm sec}^{-1}$ at energies $>$0.5 TeV. The data indicate that the emission region is broader than the point spread function of our telescope.

astro-ph↗
arXiv2002

Development of an atmospheric Cherenkov imaging camera for the CANGAROO-III experiment

A Cherenkov imaging camera for the CANGAROO-III experiment has been developed for observations of gamma-ray induced air-showers at energies from 10$^{11}$ to 10$^{14}$ eV. The camera consists of 427 pixels, arranged in a hexagonal shape at 0.17$^\circ$ intervals, each of which is a 3/4-inch diameter photomultiplier module with a Winston-cone--shaped light guide. The camera was designed to have a large dynamic range of signal linearity, a wider field of view, and an improvement in photon collection efficiency compared with the CANGAROO-II camera. The camera, and a number of the calibration experiments made to test its performance, are described in detail in this paper.

astro-ph↗
arXiv2002

Observation of gamma-rays greater than 10 TeV from Markarian 421

We have observed Markarian 421 in January and March 2001 with the CANGAROO-II imaging Cherenkov telescope during an extraordinarily high state at TeV energies. From 14 hours observations at very large zenith angles, $\sim70^\circ$, a signal of 298 $\pm$ 52 gamma-ray--like events (5.7 $σ$) was detected at $E>10$ TeV, where a higher sensitivity is achieved than those of usual observations near the zenith, owing to a greatly increased collecting area. Under the assumption of an intrinsic power-law spectrum, we derived a differential energy spectrum $dN/dE = (3.3 \pm 0.9_{stat.} \pm 0.3_{syst.})\times10^{-13} (E/10 {Te V})^{-(4.0 ^{+0.9}_{-0.6}_{stat.} \pm 0.3_{syst.})}$ ph./cm$^2$/sec/TeV, which is steeper than those previously measured around 1 TeV, and supports the evidence for a cutoff in the spectrum of Markarian 421. However, the 4 $σ$ excess at energies greater than 20 TeV in our data favors a cutoff energy of $\sim$8 TeV, at the upper end of the range previously reported from measurements at TeV energies.

astro-ph↗
arXiv2002

The acceleration of cosmic-ray protons in the supernova remnant RX J1713.7-3946

Protons with energies up to 10^15 eV are the main component[1] of cosmic rays, but evidence for the specific locations where they could have been accelerated to these energies has been lacking[2]. Electrons are known to be accelerated to cosmic-ray energies in supernova remnants[3, 4], and the shock waves associated with such remnants, when they hit the surrounding interstellar medium, could also provide the energy to accelerate protons. The signature of such a process would be the decay of pions (pi0), which are generated when the protons collide with atoms and molecules in an interstellar cloud: pion decay results in g-rays with a particular spectral-energy distribution[5, 6]. Here we report the observation of cascade showers of optical photons resulting fromg-rays at energies of 10^12 eV hitting Earth's upper atmosphere, in the direction of the supernova remnant RX J1713.7-3946. The spectrum is a good match to that predicted by pion decay, and cannot be explained by other mechanisms.

astro-ph↗
arXiv2001

Likelihood Analysis of sub-TeV Gamma-rays from RXJ1713-39

We have detected gamma-rays from RXJ1713$-$39 in the energy range between 400 GeV and 5 TeV using a new kind of analysis: likelihood analysis. The statistical significance of the measurement is greater than 8 $σ$. The details of this analysis method are presented.

astro-ph↗
arXiv2001

The CANGAROO-III Project: Status report

We report on the status of the construction of an array of four 10 m atmospheric Cherenkov telescopes for gamma-ray astronomy, near Woomera, in South Australia -- the CANGAROO-III project. The first telescope of this array is the upgraded version of the CANGAROO-II 7 m telescope and has been in operation since March 2000. The second telescope, an improved version of the first, is being constructed for installation in late 2001. Stereoscopic observation of sub TeV gamma-rays with the two 10 m telescopes will begin in 2002 and the full array will be operational in 2004.

astro-ph↗
arXiv2001

Search for gamma-rays above 10 TeV from Markarian 421 in a high state with the CANGAROO-II telescope

A preliminary result from Markarian 421 observations in the energy region above 10 TeV with the CANGAROO-II 10 m telescope is presented. In January 2001, the HEGRA group reported that Markarian 421 had become very active, with flux levels up to 4 times that of the Crab Nebula. As a result, we observed Mkn 421 during six nights from January 24th to February 1st, and four nights from March 1st to 4th. Observations were carried out using the very large zenith angle technique ($\sim$70 degree) and the energy threshold is estimated from Monte Carlo simulations to be around 10 TeV. We have detected gamma-ray emission in this energy range.

astro-ph↗
arXiv1998

The monitoring system for the aerogel Cherenkov counter of the BELLE detector

We report on a design and performances of a monitoring system developed for the aerogel Cherenkov counters (ACC) of the BELLE detector. The system consists of blue LEDs, a diffuser box, and optical distributors which distribute the LED light to the ACC modules. The employed LED (NSPB series) has been observed to have high reliability on the long term stability and the temprature dependence. The diffuser box is employed to reduce the intrinsic non-uniformity of the LED light intensity. The overall performances of the present monitoring system on uniformity and intensity of the light output have been found to satisfy all the requirements for the monitoring.

hep-ex↗
arXiv1995

Recent results from TRISTAN

The TRISTAN results from 1994 to 1995 are reviewed in this report. The physics results dominated the $γγ$ physics. Therefore, only these are selected in this article. We have systematically investigated jet productions, the $γ$-structure function, and charm pair productions in $γγ$ processes. The results, discussions, and future prospects are presented.

hep-ex↗
arXiv1995

Observation of Excess $Λ(\barΛ)$ Production in Two-Photon Processes at TRISTAN

We have carried out inclusive measurements of $Λ(\barΛ)$ production in two-photon processes at TRISTAN. The mean $\sqrt{s}$ was 58 GeV and the integrated luminosity was 265 pb$^{-1}$. Inclusive $Λ(\barΛ)$ samples were obtained under such conditions as no-electron, anti-electron, and remnant-jet tags. The data were compared with theoretical calculations. The measured cross sections are two-times larger than the leading-order theoretical predictions, suggesting the necessity of next-to-leading-order Monte-Carlo generator.

hep-ex↗
arXiv1994

$K^0(\bar{K^0})$ Production in Two-Photon Processes at TRISTAN

We have carried out an inclusive measurement of $K^0(\bar{K^0})$ production in two-photon processes at TRISTAN. The mean $\sqrt{s}$ was 58 GeV and the integrated luminosity was 199 pb$^{-1}$. High-statistics $K_s$ samples were obtained under such conditions as no-, anti-electron, and remnant-jet tags. The remnant-jet tag, in particular, allowed us, for the first time, to measure the cross sections separately for the resolved-photon and direct processes.

hep-ex↗
arXiv1994

New Tagging Method of B Flavor of Neutral B Meson in CP Violation Measurement in Asymmetric B-Factory Experiment

In CP violation measurements in asymmetric B-factory experiments, a determination of the B flavor of the neutral B mesons is necessary. A new method to this purpose using only three vectors of charged particles has been developed. This method (weighted charge method) does not require either lepton identification or charged-kaon identification. The tagging efficiency, probability for incorrect tagging, and effective tagging efficiency of this method are 43.1, 18.3, and 17.3\%, respectively.

hep-ex↗
arXiv1994

A Measurement of the $D^{*\pm}$ Cross Section in Two-Photon Processes

We have measured the inclusive $D^{*\pm}$ production cross section in a two-photon collision at the TRISTAN $e^+e^-$ collider. The mean $\sqrt{s}$ of the collider was 57.16 GeV and the integrated luminosity was 150 $pb^{-1}$. The differential cross section ($dσ(D^{*\pm})/dP_T$) was obtained in the $P_T$ range between 1.6 and 6.6 GeV and compared with theoretical predictions, such as those involving direct and resolved photon processes.

hep-ex↗