A statistical procedure for the identification of positrons in the PAMELA experiment

Abstract

The PAMELA satellite experiment has measured the cosmic-ray positron fraction between 1.5 GeV and 100 GeV. The need to reliably discriminate between the positron signal and proton background has required the development of an ad hoc analysis procedure. In this paper, a method for positron identification is described and its stability and capability to yield a correct background estimate is shown. The analysis includes new experimental data, the application of three different fitting techniques for the background sample and an estimate of systematic uncertainties due to possible inaccuracies in the background selection. The new experimental results confirm both solar modulation effects on cosmic-rays with low rigidities and an anomalous positron abundance above 10 GeV

Modulation of Galactic Protons in the Heliosphere During the Unusual Solar Minimum of 2006 to 2009

“…In this context, we present observed galactic proton spectra, from 100 MeV to 50 GeV, for (Adriani et al, 2009a) and positron galactic abundances (Adriani et al, 2009b;Boezio et al, 2009). The high-resolution PAMELA spectrometer also allows to perform hydrogen and helium spectral measurements up to 1.2 TV (Adriani et al, 2011), which is the highest limit achieved by this kind of experiments.…”

“…The high-resolution PAMELA spectrometer also allows to perform hydrogen and helium spectral measurements up to 1.2 TV (Adriani et al, 2011), which is the highest limit achieved by this kind of experiments. Adriani et al (2013) Table 1 for 2006, 2007, 2008 and 2009, respectively. These averaged values are used as observationally motivated input to our model, with the diffusion coefficients and drift coefficient (being theoretically motivated) recalculated every time for the four selected time periods. The period over which the averaging is done has to be long enough to assure that these modulation conditions are settled throughout the heliosphere.…”

Impact of Fermi-LAT and AMS-02 results on cosmic-ray astrophysics

“…This can be compared with analyses finding δ ≈ 0.44 ± 0.03 and a source injection index of 2.34 [21] using the form D(R) = D 0 β(R/R 0 ) δ for the diffusion coefficient. PAMELA analysis finds δ ∼ = 0.4 [22].…”

Leptonic dark matter annihilation in the evolving universe: constraints and implications

“…The γ-ray emission produced in the leptonic DM annihilation generally include two components: the inverse Compton (IC) component through interactions between electrons/positrons and the cosmological radiation field such as the CMB, and the direct FSR 1 We adopt the parameters fitted using fixed background approach given in Ref. [44] (Table I).…”

“…Recently, observations of the cosmic ray (CR) positron fraction by the PAMELA experiment [1], the total electron and positron spectra by the ATIC [2] experiment, the PPB-BETS [3] experiment, the HESS [4,5] experiment and the Fermi [6] experiment all show interesting excesses when compared with the expectations of the conventional astrophysical background.…”