Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,*,Cosmic Rays-Overview,Outside earths atmosphere,these are charged particles,86%protons,These,primary,cosmic ray particles interact with air high in the atmosphere(15 km),creating showers of secondary particles,By time the secondaries reach sea level,the muons dominate the flux,The detectable(vertical)rate at sea level is 1/cm,2,/min (e.g.in CRDs),Outside the solar system,CRs have an energy density of 1 eV/cm,3,Starlight:0.6 eV/cm,3,1 eV=1.6 10,-19,J,30%of natural radiation,Provide charge and seeds for lightning,from QuarkNet CRD manual,June 28,2006,1,composition of primaries,90%protons(,not,anti-protons),The remainder mostly follow solar system abundances(eg meteorites and solar photosphere),Spallation of O and C nuclei,for example,create more Li,Be,B than is typical of solar system,cosmic rays,solar system,June 28,2006,2,energy and origin of primaries,Steeply falling,power law energy spectrum,For E1014 eV,spectrum and flux are consistent with acceleration by shock waves from supernovae(“Fermi acceleration),For larger energy,mechanism is unknown(black hole at galactic center?),For E1019 eV,protons would not be captured by galactic magnetic field(310-10 T),So higher energy CRs must be extra-galactic.but GZK cutoff.a mystery,3,cosmic rays at earths surface(secondaries),Primaries interact at z15 km,producing a shower of(mostly)short-lived particles.,e.g.pion(,)lifetime is 2.610,-8,s,The long-lived secondaries are:,e,photons:mostly absorbed,neutrinos():practically invisible,muons(,):,=lifetime is 2.210,-6,s,Without time dilation,muons would travel dc=660 m,with a survival fraction e,-0.66/15,10,-10,Instead,for a 10 GeV muon,=10/0,1=100,then mean distance is 66 km.(OK),Detectable(vertical)flux is 1/cm,2,/min,Simulated event:,start,.,end,Movie,Sim tool,4,5,6,7,8,