Development of a Large-Area Aerogel Cherenkov Counter Onboard BESS

This paper describes the development of a threshold type aerogel Cherenkov counter with a large sensitive area of 0.6 m$^2$ to be carried onboard the BESS rigidity spectrometer to detect cosmic-ray antiprotons. The design incorporates a large diffusion box containing 46 finemesh photomultipliers, with special attention being paid to achieving good performance under a magnetic field and providing sufficient endurance while minimizing material usage. The refractive index of the aerogel was chosen to be 1.03. By utilizing the muons and protons accumulated during the cosmic-ray measurements at sea level, a rejection factor of 10$^4$ was obtained against muons with $\beta \approx 1$, while keeping 97% efficiency for protons below the threshold.Comment: 13 pages, LaTex, 9 eps figures included, submitted to NIM

Measurements of Atmospheric Antiprotons

We measured atmospheric antiproton spectra in the energy range 0.2 to 3.4 GeV, at sea level and at balloon altitude in the atmospheric depth range 4.5 to 26 g/cm^2. The observed energy spectra, including our previous measurements at mountain altitude, were compared with estimated spectra calculated on various assumptions regarding the energy distribution of antiprotons that interacted with air nuclei.Comment: Accepted for publication in PL

Measurements of Proton, Helium and Muon Spectra at Small Atmospheric Depths with the BESS Spectrometer

The cosmic-ray proton, helium, and muon spectra at small atmospheric depths of 4.5 -- 28 g/cm^2 were precisely measured during the slow descending period of the BESS-2001 balloon flight. The variation of atmospheric secondary particle fluxes as a function of atmospheric depth provides fundamental information to study hadronic interactions of the primary cosmic rays with the atmosphere.Comment: 21 pages, 11 figures, 4 table

Validating Variational Bayes Linear Regression Method With Multi-Central Datasets.

PurposeTo validate the prediction accuracy of variational Bayes linear regression (VBLR) with two datasets external to the training dataset.MethodThe training dataset consisted of 7268 eyes of 4278 subjects from the University of Tokyo Hospital. The Japanese Archive of Multicentral Databases in Glaucoma (JAMDIG) dataset consisted of 271 eyes of 177 patients, and the Diagnostic Innovations in Glaucoma Study (DIGS) dataset includes 248 eyes of 173 patients, which were used for validation. Prediction accuracy was compared between the VBLR and ordinary least squared linear regression (OLSLR). First, OLSLR and VBLR were carried out using total deviation (TD) values at each of the 52 test points from the second to fourth visual fields (VFs) (VF2-4) to 2nd to 10th VF (VF2-10) of each patient in JAMDIG and DIGS datasets, and the TD values of the 11th VF test were predicted every time. The predictive accuracy of each method was compared through the root mean squared error (RMSE) statistic.ResultsOLSLR RMSEs with the JAMDIG and DIGS datasets were between 31 and 4.3 dB, and between 19.5 and 3.9 dB. On the other hand, VBLR RMSEs with JAMDIG and DIGS datasets were between 5.0 and 3.7, and between 4.6 and 3.6 dB. There was statistically significant difference between VBLR and OLSLR for both datasets at every series (VF2-4 to VF2-10) (P < 0.01 for all tests). However, there was no statistically significant difference in VBLR RMSEs between JAMDIG and DIGS datasets at any series of VFs (VF2-2 to VF2-10) (P > 0.05).ConclusionsVBLR outperformed OLSLR to predict future VF progression, and the VBLR has a potential to be a helpful tool at clinical settings

Precise Measurements of Atmospheric Muon Fluxes with the BESS Spectrometer

The vertical absolute fluxes of atmospheric muons and muon charge ratio have been measured precisely at different geomagnetic locations by using the BESS spectrometer. The observations had been performed at sea level (30 m above sea level) in Tsukuba, Japan, and at 360 m above sea level in Lynn Lake, Canada. The vertical cutoff rigidities in Tsukuba (36.2 N, 140.1 E) and in Lynn Lake (56.5 N, 101.0 W) are 11.4 GV and 0.4 GV, respectively. We have obtained vertical fluxes of positive and negative muons in a momentum range from 0.6 to 20 GeV/c with systematic errors less than 3 % in both measurements. By comparing the data collected at two different geomagnetic latitudes, we have seen an effect of cutoff rigidity. The dependence on the atmospheric pressure and temperature, and the solar modulation effect have been also clearly observed. We also clearly observed the decrease of charge ratio of muons at low momentum side with at higher cutoff rigidity region.Comment: 35 pages, 9 figures. Submitted to Astroparticle Physic

The plerion nebula in IC 443: the XMM-Newton view

\xmm ~observations of the X-ray feature 1SAX J0617.1+2221 in the IC443 supernova remnant are reported.We resolve the structure of the nebula into a compact core with a hard spectrum of photon index $\gamma= 1.63^{+0.11}_{-0.10}$ in the 2--10 keV energy range. The nebula also has an extended (\sim 8\arcmin \times 5\arcmin) X-ray halo, much larger than the radio emission extension. The photon index softens, following a linear scaling with distance from the centroid, similar to other known X-ray plerions. The index range is compatible with synchrotron burn-off models. All the observational evidence points toward a confirmation of the plerionic nature of the nebula, as recently suggested by a \ch observation, but with characteristics more similar to "non Crab-like" plerions. We discuss the implications on the synchrotron nebula magnetic field if the $>100$ MeV emission reported by {\it CGRO EGRET} is produced by the synchrotron emission. We also constrain the thermal emission of the central object, arguing that the surface temperature should be around 0.1 keV, although other possible fits cannot be excluded on the base of the \xmm dataComment: 6 pages, 5 figures, accepted for publication in A&A. Color PDF file ftp://astro.estec.esa.nl/pub/sciproj/fbocchin_h2804.pdf. Color PS file http://www.astropa.unipa.it/biblioteca/OAPA_preprints/h2804.ps.g

Measurements of 0.2 to 20 GeV/n cosmic-ray proton and helium spectra from 1997 through 2002 with the BESS spectrometer

We measured low energy cosmic-ray proton and helium spectra in the kinetic energy range 0.215 - 21.5 GeV/n at different solar activities during a period from 1997 to 2002. The observations were carried out with the BESS spectrometer launched on a balloon at Lynn Lake, Canada. A calculation for the correction of secondary particle backgrounds from the overlying atmosphere was improved by using the measured spectra at small atmospheric depths ranging from 5 through 37 g/cm^2. The uncertainties including statistical and systematic errors of the obtained spectra at the top of atmosphere are 5-7 % for protons and 6-9 % for helium nuclei in the energy range 0.5 - 5 GeV/n.Comment: 27 pages, 7 Tables, 9 figures, Submitted to Astroparticle Physic

X-Ray Observations of the supernova remnant G21.5-0.9

We present the analysis of archival X-ray observations of the supernova remnant (SNR) G21.5-0.9. Based on its morphology and spectral properties, G21.5-0.9 has been classified as a Crab-like SNR. In their early analysis of the CHANDRA calibration data, Slane et al. (2000) discovered a low-surface-brightness, extended emission. They interpreted this component as the blast wave formed in the supernova (SN) explosion. In this paper, we present the CHANDRA analysis using a total exposure of ~150 ksec. We also include ROSAT and ASCA observations. Our analysis indicates that the extended emission is non-thermal -- a result in agreement with XMM observations. The entire remnant of radius ~ 2'.5 is best fitted with a power law model with a photon index steepening away from the center. The total unabsorbed flux in the 0.5-10 keV is 1.1E-10 erg/cm2/s with an 85% contribution from the 40" radius inner core. Timing analysis of the High-Resolution Camera (HRC) data failed to detect any pulsations. We put a 16% upper limit on the pulsed fraction. We derive the physical parameters of the putative pulsar and compare them with those of other plerions (such as the Crab and 3C 58). G21.5-0.9 remains the only plerion whose size in X-rays is bigger than in the radio. Deep radio observations will address this puzzle.Comment: 23 pages including 11 figures and 3 tables; accepted by ApJ June 22, 2001; to appear in Oct 20, 2001 issue of Ap