Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Precise Measurement of Cosmic-Ray Proton and Helium Spectra with the BESS Spectrometer

T. Sanuki, M. Motoki, H. Matsumoto, E. S. Seo, J. Z. Wang, K. Abe, K. Anraku, Y. Asaoka, M. Fujikawa, M. Imori, T. Maeno, Y. Makida, N. Matsui, H. Matsunaga, J. Mitchell, T. Mitsui, A. Moiseev, J. Nishimura, M. Nozaki, S. Orito, J. Ormes, T. Saeki, M. Sasaki, Y. Shikaze, T. Sonoda, R. Streitmatter, J. Suzuki, K. Tanaka, I. Ueda, N. Yajima, T. Yamagami, A. Yamamoto, T. Yoshida, K. Yoshimura

TL;DR

This study delivers a high-precision measurement of cosmic-ray proton and helium spectra using the BESS spectrometer during the 1998 balloon flight, leveraging a uniform $1$-Tesla magnetic field and a high-resolution tracking system to determine magnetic rigidity with minimal deformation. A dedicated Cherenkov-triggered high-energy mode and strict single-track, high-efficiency event-selection enable robust proton ($1$–$120$ GeV) and helium ($1$–$54$ GeV/n) flux determinations, corrected for detector, interaction, and atmospheric secondary effects via GEANT-based simulations. The resulting top-of-atmosphere fluxes carry uncertainties of $\pm 5\%$ for protons and $\pm 10\%$ for helium, and the findings favor lower atmospheric neutrino flux predictions at higher energies, providing crucial inputs for modeling secondary cosmic-ray components and neutrino production.

Abstract

We report cosmic-ray proton and helium spectra in energy ranges of 1 to 120 GeV and 1 to 54 GeV/nucleon, respectively, measured by a balloon flight of the BESS spectrometer in 1998. The magnetic-rigidity of the cosmic-rays was reliably determined by highly precise measurement of the circular track in a uniform solenoidal magnetic field of 1 Tesla. Those spectra were determined within overall uncertainties of +-5 % for protons and +- 10 % for helium nuclei including statistical and systematic errors.

Precise Measurement of Cosmic-Ray Proton and Helium Spectra with the BESS Spectrometer

TL;DR

This study delivers a high-precision measurement of cosmic-ray proton and helium spectra using the BESS spectrometer during the 1998 balloon flight, leveraging a uniform -Tesla magnetic field and a high-resolution tracking system to determine magnetic rigidity with minimal deformation. A dedicated Cherenkov-triggered high-energy mode and strict single-track, high-efficiency event-selection enable robust proton (– GeV) and helium (– GeV/n) flux determinations, corrected for detector, interaction, and atmospheric secondary effects via GEANT-based simulations. The resulting top-of-atmosphere fluxes carry uncertainties of for protons and for helium, and the findings favor lower atmospheric neutrino flux predictions at higher energies, providing crucial inputs for modeling secondary cosmic-ray components and neutrino production.

Abstract

We report cosmic-ray proton and helium spectra in energy ranges of 1 to 120 GeV and 1 to 54 GeV/nucleon, respectively, measured by a balloon flight of the BESS spectrometer in 1998. The magnetic-rigidity of the cosmic-rays was reliably determined by highly precise measurement of the circular track in a uniform solenoidal magnetic field of 1 Tesla. Those spectra were determined within overall uncertainties of +-5 % for protons and +- 10 % for helium nuclei including statistical and systematic errors.

Paper Structure

This paper contains 4 sections, 4 figures.

Table of Contents

  1. INTRODUCTION
  2. THE BESS SPECTROMETER
  3. DATA ANALYSIS
  4. EXPERIMENTAL RESULTS AND CONCLUSION

Figures (4)

  • Figure 1: Cross-sectional view of the BESS instrument.
  • Figure 2: Deflection uncertainty for protons. Each area of the histogram is normalized to unity.
  • Figure 3: Proton bands in (a) $dE/dx$ (top-TOF) vs rigidity plane; and (b) 1/$\beta$ vs rigidity plane after proton $dE/dx$ selection. $dE/dx$ in the bottom-TOF is also checked. The superimposed graphs show the proton selection criteria above 10 GV. Helium nuclei were selected in the same manner.
  • Figure 4: Absolute differential proton and helium spectra. Filled squares show results of the BESS--98 experiment. The spectra obtained by other experiments are also shown by different symbols indicated in the figure. Dashed lines show assumed spectra in the atmospheric neutrino flux calculation.