S. Haino

Measurement of the cosmic-ray antiproton spectrum at solar minimum with a long-duration balloon flight over Antarctica

The energy spectrum of cosmic-ray antiprotons (ps) from 0.17 to 3.5 GeV has been measured using 7886 ps detected by BESS-Polar II during a long-duration flight over Antarctica near solar minimum in December 2007 and January 2008. This shows good consistency with secondary p calculations. Cosmologically primary ps have been investigated by comparing measured and calculated p spectra. BESS-Polar II data show no evidence of primary ps from the evaporation of primordial black holes.

Measurements of cosmic-ray proton and helium spectra from the BESS-Polar long-duration balloon flights over Antarctica

The BESS-Polar Collaboration measured the energy spectra of cosmic-ray protons and helium during two long-duration balloon flights over Antarctica in December 2004 and December 2007, at substantially different levels of solar modulation. Proton and helium spectra probe the origin and propagation history of cosmic rays in the galaxy, and are essential to calculations of the expected spectra of cosmic-ray antiprotons, positrons, and electrons from interactions of primary cosmic-ray nuclei with the interstellar gas, and to calculations of atmospheric muons and neutrinos. We report absolute spectra at the top of the atmosphere for cosmic-ray protons in the kinetic energy range 0.2-160 GeV and helium nuclei 0.15-80 GeV/nucleon. The corresponding magnetic rigidity ranges are 0.6-160 GV for protons and 1.1-160 GV for helium. These spectra are compared to measurements from previous BESS flights and from ATIC-2, PAMELA, and AMS-02. We also report the ratio of the proton and helium fluxes from 1.1 GV to 160 GV and compare to ratios from PAMELA and AMS-02.

Measurements of galactic cosmic-ray hydrogen and helium isotopes with the BESS-polar II instrument

Nicolas Picot-Clémente∗†, K. Abe2, H. Fuke3, S. Haino4, T. Hams5, M. Hasegawa4, A. Horikoshi4, A. Itazaki2, K.C. Kim1, T. Kumazawa4, A. Kusumoto2, M.H. Lee1, Y. Makida4, S. Matsuda4, Y. Matsukawa2, K. Matsumoto4, J.W. Mitchell5, A.A. Moiseev5, J. Nishimura1, M. Nozaki4, R. Orito2, J.F. Ormes6, K. Sakai5, M. Sasaki5, E.S. Seo1, Y. Shikaze2, R. Shinoda7, R.E. Streitmatter5, J. Suzuki4, Y. Takasugi2, K. Takeuchi2, K. Tanaka4, N. Thakur6, T. Yamagami4, A. Yamamoto4, T. Yoshida3, K. Yoshimura4 1 Institute for Physical Science and Technology, University of Maryland, College Park MD 20742, USA 2 Kobe University, Kobe, Hyogo 657-8501, Japan 3 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (ISAS/JAXA), Sagamihara, Kanagawa 252-5210, Japan 4 High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan 5 National Aeronautics and Space Administration, Goddard Space Flight Center (NASA/GFSC), Greenbelt, MD 20771, USA 6 University of Denver, Denver, CO 80208, USA 7 The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan

Search for cosmic-ray antideuterons with BESS-Polar

Although cosmic-ray antideuterons can be produced in primary cosmic-ray interactions with the interstellar medium in the same way as cosmic-ray antiprotons, the probability is much smaller, especially at low energies, because of the very low production cross-section and strict kinematic requirement compared to secondary antiproton production. The lack of significant astrophysical background indicates that a search for low-energy antideuterons could be a good probe for a novel production mechanisms such as pair-annihilation of neutralino dark matter or evaporation of primordial black holes. The BESS-Polar program has accumulated cosmic-ray data in near solar minimum conditions with more than ten times the statistics of those obtained by BESS flights during the previous solar minimum period. Based on these data, we perform a new antideuteron search with unprecedented sensitivity.

Precise Measurements of Hydrogen and Helium Isotopes with BESS-Polar II

A precise knowledge of cosmic-ray hydrogen and helium isotopes provides important information to better understand Galactic cosmic-ray propagation. Deuteron and helium 3 species are mainly secondary particles created by the spallation of primary proton and helium 4 particles during their propagation in the Galaxy. Secondary-to-primary ratios thus bring direct information on the average amount of material traversed by cosmic rays in the interstellar medium. The Balloon-borne Experiment with Superconducting Spectrometer BESS-Polar II flew over Antarctica for 24.5 days from December 2007 through January 2008, during the 23rd solar cycle minimum. The instrument is made of complementary particle detectors which allow to precisely measure the charge, velocity and rigidity of incident cosmic rays. It can accurately separate and precisely measure cosmic-ray hydrogen and helium isotopes between 0.2 and 1.5 GeV/nucleon. These data, which are the most precise to date, will be reported and their implications will be discussed.

BESS-polar measurements of the cosmic-ray proton and helium spectra

K. Sakai∗1,9†, K. Abe2‡ , H. Fuke3, S. Haino4§ , T. Hams1,9, M. Hasegawa4, A. Horikoshi4, A. Itazaki2, K. C. Kim5, T. Kumazawa4, A. Kusumoto2, M. H. Lee5, Y. Makida4, S. Matsuda4, Y. Matsukawa2, K. Matsumoto4, J. W. Mitchell1, Z. Myers5, J. Nishimura6, M. Nozaki4, R. Orito2¶, J. F. Ormes7, N. Picot-Clemente5, M. Sasaki1,9, E. S. Seo5, Y. Shikaze2, R. Shinoda6, R. E. Streitmatter1, J. Suzuki4, Y. Takasugi2, K. Takeuchi2, K. Tanaka4, N. Thakur1, T. Yamagami3‖, A. Yamamoto4, T. Yoshida3 and K. Yoshimura8 1 NASA-Goddard Space Flight Center (NASA-GSFC), Greenbelt,MD 20771, USA 2 Kobe University, Kobe, Hyogo 657-8501, Japan 3 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency

Search for Novel Origins of Cosmic-ray Antiprotons and Antimatter with BESS-Polar Flight over Antarctica.

The primary aims of the BESS-Polar program are precise measurements of the low-energy antiproton spectrum and search for cosmologically significant antimatter, which would provide new clues to understand the early Universe. The second flight (BESS-Polar II) over Antarctica was successfully carried out in Dec 2007 Jan 2008. We performed 24.5days scientific observation just at the solar minimum. The payload worked well during the flight and 4.7 billion cosmic-ray events were collected. Based on the BESS-Polar II data, we present recent preliminary results of cosmic-ray antiproton measurements and sensitive search for antimatter. 35th International Conference of High Energy Physics ICHEP2010, July 22-28, 2010 Paris France

BESS-Polar: Search for Antihelium

We have searched for antihelium in cosmic-rays since 1993 using a series of nine conventional BESS northern latitude balloon flights and two long-duration BESS-Polar Antarctic balloon flights. The BESS-Polar spectrometer is an evolutionary development of the previous BESS instruments, adapted to long duration flight. No antihelium candidate was found in the rigidity ranges of 0.6-20 GV among 8 × 10 6 helium nuclei events for BESS-Polar I and in the rigidity range of 0.6-14 GV among 4 × 10 7 events for BESS-Polar II, respectively. A resultant upper limit of 6.9 × 10 −8 for the abundance ratio of antihelium/helium at the top of the atmosphere in the rigidity range of 1-14 GV was set by combining all the BESS and BESS-Polar flight data. This is the most stringent limit obtained to date.

Cosmic ray helium isotopes from the BESS-Polar I experiment

The first flight of the Balloon-Borne Experiment with a Superconducting Spectrometer (BESS-Polar I) in Antarctica collected about 900 million cosmic ray events during 8.5 days in 2004. Particle charge was determined from energy loss in the scintillators, rigidity by reconstructing each particle trajectory in the magnetic field, and velocity by utilizing time of flights counters. These measurements can clearly identify hydrogen and helium isotopes among the incoming particles. These isotopes are generally believed to result from nuclear interactions of primaries with the interstellar medium. Measurement of their flux is expected to provide important information on cosmic ray sources and particle propagation in interstellar space. The presentation will focus on determination of the helium isotope flux in the kinetic energy per nucleon range 0.1 GeV/n to about 1.5 GeV/n. After quickly introducing the BESS-Polar I detector, the dedicated analysis to differentiate isotopes will be described. Finally, the energy spectra will be presented and compared to previous measurements.

Transient variations in cosmic ray proton fluxes from BESS-Polar I

BESS (Balloon-borne Experiment with a Superconducting Spectrometer ) had its first circumpolar flight from Williams Field near McMurdo Station, Antarctica from Dec. 13 to 21, 2004. Ou r sub-1% precision reveals BESS-Polar I proton fluxes exhibit transient variations at the few1% level. The time prog ression of proton flux has three main features; a rising flux at the beginning of the flight, a transition region around Dec. 17, followed by quasi-periodic variation. Neutron monitor data show that the BESS-Polar I flight occurred during the recov ery phase of a small Forbush decrease. The solar wind plasma and particle data show that this flight took place during the tail end of a high-energy, multiple-eruption solar energetic particle (SEP) event. A high speed solar wind stream arrived n ear the Earth around Dec. 17, 2004. We present the flux progression as a function of energy between 0.1 100.0 GeV a nd suggest possible physical interpretations.