吉田 哲也

Prepared for 28th International Cosmic Ray Conferences (ICRC 2003), Tsukuba, Japan, 31 Jul - 7 Aug 2003. <br /> Published in *Tsukuba 2003, Cosmic Ray* 1163-1166<br /> <br /> 0&quot; target=&quot;_blank&quot;&gt;&lt;/a&gt;&lt;a href=&quot;http://www-rccn.icrr.u-tokyo.ac.jp/icrc2003/PROCEEDINGS/PDF/291.pdf

Prepared for 28th International Cosmic Ray Conferences (ICRC 2003), Tsukuba, Japan, 31 Jul - 7 Aug 2003. <br /> Published in *Tsukuba 2003, Cosmic Ray* 1797-1800<br /> <br /> 0&quot; target=&quot;_blank&quot;&gt;&lt;/a&gt; &lt;a href=&quot;http://www-rccn.icrr.u-tokyo.ac.jp/icrc2003/PROCEEDINGS/PDF/445.pdf

Prepared for 8th Accelerator and Particle Physics Institute (APPI 2003), Appi, Iwate, Japan, 25-28 Feb 2003. <br /> Published in *Appi 2003, Accelerator and particle physics* 284-293

BESS

J-GLOBAL ID 200902109906977366 <br /> 整理番号 02A0351952 <br /> JST資料番号 G0925B <br />

Prepared for 7th Accelerator and Particle Physics Institute (APPI 2002), Appi, Iwate Ken, Japan, 13-16 Feb 2002. <br /> Published in *Appi 2002, Accelerator and particle physics* 117-138 <br />

We have searched for antihelium nuclei in cosmic rays using the data obtained from balloon flights of the BESS magnetic spectrometer. The search was mainly based on track-quality selection, followed by rigidity analysis, and on the time-of-flight and dE/dx measurements by the scintillation counter hodoscope. We analysed all the data collected during 1993-2000 with a common analysis procedure. No antihelium nuclei events were found in the energy range from 1 to 14 GV. In order to determine a new upper limit, we have simulated the loss in the air and in the instrument of He (He) using the GEANT/GHEISHA code. Combined with the data collected in 1993 through 2000, a new 95 % confidence upper limit for the ratio of He/He at the top of the atmosphere of 6.8 × 10-7 has been obtained to be after correcting for the interactions in the air and in the instruments.

The BESS-Polar experiment with long-duration balloon flights at Antarctica aims at extremely sensitive measurement of low energy antiprotons to search for novel primary origins in the early Universe, and to study cosmic-ray propagation and solar modulation. The search for cosmic antimatter is a fundamental objective to study baryon asymmetry in the Universe. The BESS experiment with high rigidity resolution and large geometrical acceptance will maximize advantages of long duration flights at Antarctica where the rigidity cut-off is lowest. A very compact and thin superconducting magnet spectrometer is being developed to maximize the detector performance in low energies. The BESS-Polar project and progress of the development are described.

An accelerator experiment was performed using a low-energy antiproton beam to measure antiproton detection efficiency of BESS, a balloon-borne spectrometer with a superconducting solenoid. Measured efficiencies showed good agreement with calculated ones derived from the BESS Monte Carlo simulation based on GEANT/GHEISHA. With detailed verification of the BESS simulation, the relative systematic error of detection efficiency derived from the BESS simulation has been determined to be +/-5%, compared with the previous estimation of +/- 15% which was the dominant uncertainty for measurements of cosmic-ray antiproton flux. (C) 2002 Elsevier Science B.V. All rights reserved.

Prepared for 5th RESCEU International Symposium on New Trends in Theoretical and Observations Cosmology, Tokyo, Japan, 13-16 Nov 2001. <br /> Published in *Tokyo 2001, New trends in theoretical and observational cosmology* 111-118

27th International Cosmic Ray Conference (ICRC 2001), Hamburg, Germany, 7-15 Aug 2001.<br /> Published in *Hamburg 2001, Cosmic ray* 1699-1700<br /> <br /> 0&quot; target=&quot;_blank&quot;&gt;&lt;/a&gt; &lt;a href=&quot;http://www.copernicus.org/icrc/papers/ici6875_p.pdf

Contributed to 27th International Cosmic Ray Conference (ICRC 2001), Hamburg, Germany, 7-15 Aug 2001, Hamburg, Germany. <br /> Published in *27th International Cosmic Ray Conference (ICRC 2001), Hamburg, Germany, 7-15 Aug 2001, Vol.3* 950-953<br /> <br /> 0&quot; target=&quot;_blank&quot;&gt;&lt;/a&gt; &lt;a href=&quot;http://www.copernicus.org/icrc/papers/ici7271_p.pdf

BESS<br /> <br /> 0&quot; target=&quot;_blank&quot;&gt;&lt;/a&gt; &lt;a href=&quot;http://www.copernicus.org/icrc/papers/ici7127_p.pdf

BESS<br /> <br /> 0&quot; target=&quot;_blank&quot;&gt;&lt;/a&gt; &lt;a href=&quot;http://www.copernicus.org/icrc/papers/ici7339_p.pdf

BESS<br /> <br /> 0&quot; target=&quot;_blank&quot;&gt;&lt;/a&gt; &lt;a href=&quot;http://www.copernicus.org/icrc/papers/ici6699_p.pdf

Contributed to 27th International Cosmic Ray Conference (ICRC 2001), Hamburg, Germany, 7-15 Aug 2001. <br /> Published in *27th International Cosmic Ray Conference (ICRC 2001), Hamburg, Germany, 7-15 Aug 2001, Vol.3* pp. 927-930 Also in *Hamburg 2001, Cosmic ray*<br /> <br /> 0&quot; target=&quot;_blank&quot;&gt;0&lt;/a&gt; &lt;a href=&quot;http://www.copernicus.org/icrc/papers/ici6926_p.pdf

A series of Balloon-borne Experiments with a Superconducting Spectrometer, BESS, has been made since 1993. We report here the absolute cosmic-ray proton and helium spectra in energy ranges of 1 to 120 GeV and I to 54 GeV/nucleon, respectively, as measured by the 1998 balloon flight of the BESS spectrometer. Those spectra were determined within overall uncertainties of +/-5 % for protons and +/- 10 % for helium nuclei including statistical and systematic errors. The covered energy range is relevant to the atmospheric neutrinos observed as "fully contained events" in Super-Kamiokande. In order to extend the energy range up to around I TeV, we have started to design and develop new tracking detectors. Those energy spectra in a higher energy region will help to estimate the interstellar spectra of primary cosmic rays and the absolute fluxes of "up-going muons." (C) 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

The BESS spectrometer has measured the energy spectrum of cosmic-ray antiprotons successively in 1993, 1995, 1997 and 1998. In total, 848 antiprotons were clearly identified in energy range 0.18 to 4.20 GeV based on magnetic-rigidity, time-of-flight, energy loss, and Cherenkov radiation measurements. The measured antiproton spectra and antiproton/proton ratios were nearly identical at the upper end of the instrumental energy range, which is consistent with theoretical calculations. In the low energy region. our data show variations that are somewhat larger than expected. This might be due to statistical fluctuation, or might suggest a contribution of primary antiprotons from novel sources. (C) 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

BESS

BESS

We have obtained the absolute spectra of H and He by analyzing data collected by a series of annual flights of the Balloon borne Experiment with a Superconducting solenoid Spectrometer payload. This instrument is configured with a cylindrical magnet, a Time-of-Flight system, a set of cylindrical multiwire drift chambers inside and outside the magnet, and a central tracking device Jet chamber. The analysis involves Monte Carlo simulations of the effective geometry factor, studies of various efficiencies, and corrections for the ionization energy loss, attenuation and atmospheric secondaries. Variations of the H and He fluxes at different levels of solar modulation are presented. (C) 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

The absolute fluxes of the cosmic-ray antiproton are measured at solar minimum in the energy range 0.2 to 3.2 GeV, based on 460 antiprotons unambiguously detected by BESS spectrometer during its '95 and '97 balloon flights from Lynn Lake, Canada. In the resultant antiproton spectrum we have detected a clear peak around 2 GeV and measured its flux to 10% accuracy. The position and the absolute flux of the peak agree with the prediction of the Standard Leaky Box model for the "secondary" antiprotons. At low energies below I GeV, we observe an excess antiproton flux over the simple Standard Leaky Box prediction. This might indicate that the propagation mechanism needs to be modified, or might suggest a contribution of low-energy antiproton component from novel sources such as evaporating primordial black holes or the annihilating neutralino dark matter. Data from '98 and future Rights are expected to help us to clarify the situation. (C) 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

We describe the design and performance of a large-area scintillator hodoscope onboard the BESS rigidity spectrometer an instrument with an acceptance of 0.3 m2 sr. The hodoscope is configured such that 10 and 12 counters are, respectively, situated in upper and lower layers. Each counter is viewed from its ends by 2.5 in. fine-mesh photomultiplier tubes placed in a stray magnetic field of 0.2 T. Various beam-test data are presented. Use of cosmic-ray muons at ground-level confirmed 50 ps timing resolution for each layer, giving an overall time-of-flight resolution of 70 ps rms using a pure Gaussian-resolution function. Comparison with previous measurements on a similar scintillator hodoscope indicates good agreement with the scaling law that timing resolution is proportional to 1/√Npc, where Npc is the effective number of photoelectrons.

Prepared for 26th International Cosmic Ray Conference (ICRC 99), Salt Lake City, Utah, 17-25 Aug 1999. <br /> In *Salt Lake City 1999, Cosmic ray, vol. 3* 93-96.<br /> http://adsabs.harvard.edu/abs/1999ICRC....3...93T

Prepared for 26th International Cosmic Ray Conference (ICRC 99), Salt Lake City, Utah, 17-25 Aug 1999. <br /> In *Salt Lake City 1999, Cosmic ray, vol. 3* 85-88.

Prepared for 26th International Cosmic Ray Conference (ICRC 99), Salt Lake City, Utah, 17-25 Aug 1999. <br /> In *Salt Lake City 1999, Cosmic ray, vol. 3* 37-40. <br />

BESS<br /> KEK-PREPRINT-98-119<br /> May 27, 1998 (ISTS-98)<br /> <br /> Author list (Full version)<br /> A. Yamamoto <br /> KEK, Tsukuba <br /> S. Orito <br /> Tokyo U. <br /> <br /> J. Ormes <br /> NASA, Goddard <br /> <br /> T. Yoshida <br /> KEK, Tsukuba <br /> <br /> K. Yoshimura, K. Abe, K. Anraku, Y. Asaoka, M. Fujikawa, M. Imori, T. Maeno <br /> Tokyo U. <br /> <br /> Y. Makida <br /> KEK, Tsukuba <br /> <br /> H. Matsumoto <br /> Kobe U. <br /> <br /> N. Matsui, H. Matsunaga <br /> Tokyo U. <br /> <br /> J. Mitchell <br /> NASA, Goddard <br /> <br /> T. Mitsui <br /> Kobe U. <br /> <br /> A. Moiseev <br /> NASA, Goddard <br /> <br /> M. Motoki <br /> Tokyo U. <br /> <br /> J. Nishimura <br /> Sagamihara, Inst. Space Astron. Sci. <br /> <br /> M. Nozaki <br /> Kobe U. <br /> <br /> T. Saeki, T. Sanuki <br /> Tokyo U. <br /> <br /> M. Sasaki <br /> Kobe U. <br /> <br /> E. Seo <br /> Maryland U. <br /> <br /> Y. Shikaze, T. Sonoda <br /> Tokyo U. <br /> <br /> R. Streitmatter <br /> NASA, Goddard <br /> <br /> J. Suzuki, K. Tanaka <br /> KEK, Tsukuba <br /> <br /> I. Ueda <br /> Tokyo U. <br /> <br /> N. Yajima, T. Yamagami <br /> Sagamihara, Inst. Space Astron. Sci.

http://adsabs.harvard.edu/abs/1997ICRC....3..373S

We have searched for antihelium in the galactic cosmic rays using data obtained on the flight of the Balloon-borne Experiment with a Superconducting Spectrometer (BESS) launched from Lynn Lake, Manitoba, in northern Canada on 1995 July 25. The balloon reached an altitude of 36.5 km with a residual overburden of 5 g cm(-2). The total observation time was 12.2 kr with a live-time fraction of 0.61. No antihelium was observed after selections based on dE/dx and event quality cuts at rigidities between 1.6 and 16 GV/c; we infer that 536,420 helium nuclei survived the same cuts. This result leads to an upper limit to the &lt;(He)over bar&gt;/He abundance ratio of 8.1 x 10(-6) (95% confidence level), a factor of 2.7 over the lowest previous limit. Because this limit is for the first time at the level where predicted limits become astrophysically interesting (Ahlen et al.), we have reexamined the transport of cosmic rays in intergalactic space. We show that little can be learned about distant (&gt; 10 Mpc) domains of antimatter from a null result.

Balloon-borne experiment using a superconducting spectrometer were carried out successfully in northern Canada, in summer 1993 to 1995. In `93 flight, seven antiprotons were detected in the kinetic range between cen 200 and 600 MeV. The corresponding cosmic ray antiproton flux at the top of the atmosphere is fond to be 6.4(-3.5)(+5.5) x 10(-3)(m(2) sr s GeV)(-1). In '95 flight. improvement on the TOF resolution resulted to the observation of the forty antiprotons in the kinetic energy region 175 MeV to 1.3 GeV. The analysis on '95 flight is under way. (C) 1997 COSPAR.

BESS

Spectrometer and Balloon Borne Experiment<br /> http://www.isas.ac.jp/publications/hokokuSP/index1996.html

http://www.isas.ac.jp/publications/hokokuSP/index1996.html