Galactic secondary positron flux at the Earth

By T. Delahaye, F. Donato, N. Fornengo, J. Lavalle, R. Lineros, P. Salati, R. T. .. LAPTHAnnecy, CNRS-SPM, 9. Universite'deSavoie, U. Torino and 1 more. 2008

206 citations recorded by the source corpus.

Context. Secondary positrons are produced by spallation of cosmic rays within the interstellar gas. Measurements have been typically expressed in terms of the positron fraction, which exhibits an increase above 10 GeV. Many scenarios have been proposed to explain this feature, among them some additional primary positrons originating from dark matter annihilation in the Galaxy. Aims. The PAMELA satellite has provided high quality data that has enabled high accuracy statistical analyses to be made, showing that the increase in the positron fraction extends up to about 100 GeV. It is therefore of paramount importance to constrain theoretically the expected secondary positron flux to interpret the observations in an accurate way. Methods. We focus on calculating the secondary positron flux by using and comparing different up-to-date nuclear cross-sections and by considering an independent model of cosmic ray propagation. We carefully study the origins of the theoretical uncertainties in the positron flux. Results. We find the secondary positron flux to be reproduced well by the available observations, and to have theoretical uncertainties that we quantify to be as large as about one order of magnitude. We also discuss the positron fraction issue and find that our predictions may be consistent with the data taken before PAMELA. For PAMELA data, we find that an excess is probably present after considering uncertainties in the positron flux, although its amplitude depends strongly on the assumptions made in relation to the electron flux. By fitting the current electron data, we show that when considering a soft electron spectrum, the amplitude of the excess might be far lower than usually claimed. Conclusions. We provide fresh insights that may help to explain the positron data with or without new physical model ingredients. PAMELA observations and the forthcoming AMS-02 mission will allow stronger constraints to be aplaced on the cosmic-ray transport parameters, and are likely to reduce drastically the theoretical uncertainties.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/212411323990906c6c46fbc3620f416ab9f7b027

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Nuclear and High Energy Physics

1. E. Quataert
2. A. Strong
3. T. Thompson
4. N. Fornengo
5. Troy A. Porter
6. R. Lineros
7. S. Profumo
8. J. Lavalle

Citations in the corpus

• Galactic electrons and positrons at the Earth: new estimate of the primary and secondary fluxes (2010, methodology): “The increase in the positron fraction inferred from the PAMELA data is barely consistent with what is expected for secondary positrons (e.g. Delahaye et al. 2009), except for those secondaries produced and accelerated in sources (Berezhko et al. 2003; Blasi 2009; Mertsch & Sarkar 2009; Ahlers et…”
• Antinuclei in heavy-ion collisions (2018, background): “This observation cannot be explained by considering only secondary production of positrons [282, 283, 284].”
• THE PHYSICS OF THE FAR-INFRARED–RADIO CORRELATION. I. CALORIMETRY, CONSPIRACY, AND IMPLICATIONS (2009, background): “Above ∼ 1 GeV, the observed positron flux exceeds the predicted flux even in detailed models (see Moskalenko & Strong 1998; Beatty et al. 2004; Adriani et al. 2009; but see Delahaye et al. 2009).”
• On possible interpretations of the high energy electron–positron spectrum measured by the Fermi Large Area Telescope (2009, methodology): “While previous electron data were affected by large uncertainty on the normalization and the slope of the electron background, to accommodate the PAMELA positron fraction with a steep electron spectrum and standard secondary e+ production was already a hard task (see e.g. Delahaye et al. 2009 [61]).”
• Interpretation of AMS-02 electrons and positrons data (2014, background): “where we have neglected the effect of convection and reacceleration [12].”
• Dark Matter Searches with Astroparticle Data (2011, background): “Some recent work illustrates their effect for predictions of CR positron spectra using analytic propagation model solutions (e.g., Delahaye et al., 2009).”