Implications of the AMS-02 positron fraction in cosmic rays

2013/04/30 by Qiang Yuan, Xiao-Jun Bi, Guo-Ming Chen +4 · 2 citations
Physics and Astronomy · #Annihilation #Astronomy #Astrophysics #Cosmic ray #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Dark matter #Electron #Fermi Gamma-ray Space Telescope #Nuclear physics #PAMELA detector #Particle physics theoretical and experimental studies #Physics #Positron #Proton #Pulsar #Spectral index #Spectral line #Ultra-high-energy cosmic ray #astro-ph.HE #hep-ph

paper · pdf · doi:10.1016/j.astropartphys.2014.05.005

published as Astropart. Phys. 60 (2015) 1 · Accepted for publication in Astroparticle Physics

arxiv created 2014/05/14 · openalex publication_date 2014/05/20 · arxiv updated 2014/07/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

The AMS-02 collaboration has just released its first result of the cosmic positron fraction e⁺/(e^-+e⁺) with high precision up to ∼ 350 GeV. The AMS-02 result shows the same trend with the previous PAMELA result, which requires extra electron/positron sources on top of the conventional cosmic ray background, either from astrophysical sources or from dark matter annihilation/decay. In this paper we try to figure out the nature of the extra sources by fitting to the AMS-02 e⁺/(e^-+e⁺) data, as well as the electron and proton spectra by PAMELA and the (e^-+e⁺) spectrum by Fermi and HESS. We adopt the GALPROP package to calculate the propagation of the Galactic cosmic rays and the Markov Chain Monte Carlo sampler to do the fit. We find that the AMS-02 data have implied essential difference from the PAMELA data. There is \rm tension between the AMS-02 e⁺/(e^-+e⁺) data and the Fermi/HESS (e^-+e⁺) spectrum, that the AMS-02 data requires less contribution from the extra sources than Fermi/HESS. Then we redo the fit without including the Fermi/HESS data. In this case both the pulsars and dark matter annihilation/decay can explain the AMS-02 data. The pulsar scenario has a soft inject spectrum with the power-law index ∼ 2, while the dark matter scenario needs τ⁺τ^- final state with mass ∼ 600 GeV and a boost factor ∼ 200.

Citations

• A Markov Chain Monte Carlo technique to sample transport and source parameters of Galactic cosmic rays
• Cosmic ray acceleration in supernova remnants and the FERMI/PAMELA data
• PAMELA Measurements of Cosmic-Ray Proton and Helium Spectra
• Systematic uncertainties in the determination of the local dark matter density
• Nuclear enhancement factor in calculation of Galactic diffuse gamma-rays: A new estimate with DPMJET-3
• Precise Measurement of Cosmic‐Ray Proton and Helium Spectra with the BESS Spectrometer
• PAMELA data and leptonically decaying dark matter
• TeV Gamma Rays from Geminga and the Origin of the GeV Positron Excess
• Pulsars as the sources of high energy cosmic ray positrons
• Markov chain Monte Carlo study on dark matter property related to the cosmice±excesses
• Is the PAMELA anomaly caused by supernova explosions near the Earth?
• An anomalous positron abundance in cosmic rays with energies 1.5–100 GeV
• Cosmic-Ray Propagation and Interactions in the Galaxy
• First Result from the Alpha Magnetic Spectrometer on the International Space Station: Precision Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5–350 GeV
• Energy Spectrum of Cosmic-Ray Electrons at TeV Energies
• Testing Astrophysical Models for the PAMELA Positron Excess with Cosmic Ray Nuclei
• A Markov Chain Monte Carlo technique to sample transport and source parameters of Galactic cosmic rays

Cited by

• Excesses of cosmic ray spectra from a single nearby source
• Theoretical Interpretation of Pass 8 Fermi-LAT e+ + e− Data