ICRC2015

Methods for cosmic ray anisotropy searches with AMS-02

4 Aug 2015, 11:45

15m

World Forum

Oral contribution CR-EX Parallel CR15 Direct/Aniso

Speaker

Iris Gebauer (KIT - Karlsruhe Institute of Technology (DE))

Description

The Alpha Magnetic Spectrometer (AMS-02) is a state-of-the-art particle detector designed to operate as an external module on the International Space Station (ISS). In the absence of atmospheric disturbance, cosmic ray fluxes between 0.5 GeV and a few TeV can be measured with high precision. In 2014, the AMS collaboration provided precise measurements of the electron and positron fluxes, which indicate an additional source of positrons among the various cosmic particles. Possible candidates for this source are local pulsars, a local source of positrons produced in proton-gas interactions or the annihilation of dark matter. In the first two cases a possible anisotropy in the $e^{\pm}$ incoming direction at Earth, caused by the finite extension of the production site, might be detectable. To determine the level of isotropy in the AMS-02 data it is necessary to compare the measured $e^{\pm}$ arrival directions to reference maps, which simulate the AMS-02 measurement of an isotropic sky. A common choice of reference maps are proton count maps, assuming that a possible anisotropy in proton arrival directions is significantly lower than that for $e^{\pm}$. We present a method to determine the upper limits on an anisotropy in proton arrival directions. Two different methods to search for anisotropies in the $e^{\pm}$ fluxes, an expansion into multipoles and a direct bin-to-bin comparison, will be presented. We demonstrate the performance of the method using AMS-02 data.