Precision Measurement of Cosmic-Ray Antiproton Spectrum

Abstract

The energy spectrum of cosmic-ray antiprotons (p's) has been measured in the range 0.18 to 3.56 GeV, based on 458p's collected by BESS in recent solar-minimum period. We have detected for the first time a distinctive peak at 2 GeV ofp's originating from cosmic-ray interactions with the interstellar gas. The peak spectrum is reproduced by theoretical calculations, implying that the propagation models are basically correct and that different cosmic-ray species undergo a universal propagation. Future BESS flights toward the solar maximum will help us to study the solar modulation and the propagation in detail and to search for primaryp components.PACS numbers: 98.70.Sa, 95.85.RyThe origin of cosmic-ray antiprotons (p's) has attracted much attention since their observation was first reported by Golden et al. [1]. Cosmic-rayp's should certainly be produced by the interaction of Galactic high-energy cosmic-rays with the interstellar medium. The energy spectrum of these "secondary"p's is expected to show a characteristic peak around 2 GeV, with sharp decreases of the flux below and above the peak, a generic feature which reflects the kinematics ofp production. The secondaryp's offer a unique probe [2] of cosmic-ray propagation and of solar modulation. As other possible sources of cosmic-rayp's, one can conceive novel processes, such as annihilation of neutralino dark matter or evaporation of primordial black holes [3]. Thep's from these "primary" sources, if they exist, are expected to be prominent at low energies [4] and to exhibit large solar modulations [5]. Thus they are distinguishable in principle from the secondaryp component.The detection of the secondary peak and the search for a possible low-energy primaryp component have been difficult to achieve, because of huge backgrounds and the extremely small flux especially at low energies. The first [1] and subsequent [6] evidence for cosmic-rayp's were reported at relatively high energies, where it was not possible to positively identify thep's with a mass measurement. The first "mass-identified" and thus unambiguous detection of cosmic-rayp's was performed by BESS '93 [7] in the low-energy region (4 events at 0.3 to 0.5 GeV), which was followed by IMAX [8] and CAPRICE [9] detections. The BESS '95 measured the spectrum [10] at solar minimum, based on 43p's over the range 0.18 to 1.4 GeV. We report here a new high-statistics measurement of thep spectrum based on 458 events in the energy 1

Mixed higgsino dark matter from a large SU(2) gaugino mass

“…Indirect detection of neutralinos is also possible via the detection of anti-particles from neutralino annihilations in the galactic halo. Proposed and on-going experiments include searches for positrons [62] (HEAT [63], Pamela [64] and AMS-02 [65]), antiprotons [66] (BESS [67], Pamela, AMS-02) and anti-deuterons (D) (BESS [68], AMS-02, GAPS [69]). For positrons and antiprotons we evaluate the averaged differential antiparticle flux in a projected energy bin centered at a kinetic energy of 20 GeV, where we expect an optimal statistics and signal-to-background ratio at space-borne antiparticle detectors [45,70].…”

PAMELA: a satellite experiment for antiparticles measurement in cosmic rays

“…PAMELA expected energy range is shown. References are: Golden et al [7], [8], Bogomolov et al [9] and references therein, LEAP 87 [10], PBAR 87 [11], MASS 91 [12], IMAX 92 [13], BESS 93 [14], CAPRICE 94 [15], BESS 95+97 [16], CAPRICE 98 [17], HEAT-pbar 00 [18], and BESS 99 and 00 [19]. Lines represent theoretical calculations based on a purely secondary production of antiprotons [20].…”

Constraining the Higgs portal with antiprotons

“…Using data describing thep/p flux, on the contrary, we can safely combine different datasets. Thep/p data employed in our analysis come from the BESS [47,48], Table 1. Phenomenological parameters describing the five benchmark propagation models (first column) used in our analysis.…”