Astroparticle Physics

156 7 Secondary Cosmic RaysCygnus X3,a hadron accelerator?muon astronomyNeutral pions are usually produced in proton interactions.Therefore, the source should also be able to produce chargedpions and via their decay muons and muon neutrinos. Becauseof their short lifetime, muons would never survive the33 000 light-year distance from Cygnus X3 to Earth, so thata possible muon signal must be caused by neutrino-inducedmuons. Unfortunately, muons and multi-muons observed inthe Frejus experiment from the directions of Cygnus X3are predominantly of atmospheric origin and do not confirmthat Cygnus X3 is a strong source of high-energy particles(Fig. 7.24). The primary particles themselves acceleratedin the source could in principle point back to the sourcewhen measured on Earth. However, the arrival direction ofprimary charged particles from Cygnus X3 could also havebeen completely randomized by the irregular galactic magneticfield. Muon production by neutrinos from Cygnus X3would have been a rare event which would have required anextremely massive detector to obtain a significant rate.46°FREJUS44°Fig. 7.24Sky map of muons andmulti-muons from the direction ofCygnus X3. The cross indicates theoptically known position ofCygnus X3. The circles aroundCygnus X3 with angles of ±2 ◦ and±5 ◦ correspond to a possiblefuzziness, caused by multiplescattering of muons in rock {24}declination 42°40°38°36°34°296°300° 304° 308° 312° 316° 320°right ascension 7.4 Extensive Air Showers“Science never solves a problem withoutcreating ten more.”George Bernard ShawExtensive air showers are cascades initiated by energetic primaryparticles which develop in the atmosphere. An exten-sive air shower (EAS) has an electromagnetic, a muonic, acomponentsof an extensive air shower