Probing the CR positron/electron ratio at few hundreds GeV through Moon shadow observation with the MAGIC telescopes

摘要

The antimatter components measured in the Cosmic Ray (CR) flux are thought as secondary particles inducedby the propagation of galactic CRs within the galaxy. Recent results from the PAMELA experiment show an unexpectedincrease of the positron electron ratio above 10 GeV. There could be different interpretations to explain that result, themost discussed ones being the signature of nearby compact astrophysical source(s) or of dark matter annihilation/decay.Probing the positron-fraction rise above 100 GeV would help to disentangle among different scenarios. Imaging Atmo-sphericCherenkov Telescopes (IACT) can extract the cosmic lepton signal from the hadronic CR background betweena few hundred GeV and a few TeV and reconstruct energy and incident direction with a very good resolution. In ad-dition,by using the natural spectrometer formed by the Moon and the geomagnetic field, it is possible to measure thepositron/electron ratio at the TeV regime through the observation of the CR Moon shadow. Despite the technique isparticularly challenging because of the high background light induced by the Moon and the treatment of data, the MAG-ICcollaboration has performed for the first time such observations in 2010 and 2011. Here we present the observationstrategy and the performance achieved during this campaign.