High-energetic primary cosmic-ray particles collide with particles from the earth athmosphere, producing Ko, pº, π°, π+ and л¯. K° and pº decay to л+л¯ pairs and the charged pions decay into (anti)muons or electrons/positrons and neutrinos (see information about the particles and the air in the appendix). a) Both Kg and p meson decay into two pions. Explain why the life time of the p meson is much shorter than that of the Kg particle. Draw Feynman diagrams of both decays. b) The charged pions decay mainly into muons and neutrinos. State the type of supression which prevents the charged pions from decaying into electrons/positrons and electron neu- trinos. The muons are created in approximately 15 km altitude. Assuming they have an energy of 1 GeV, calculate the fraction of muons which reach the surface of the earth before they decay. c) The ratio between muon and electron neutrinos on the surface is expected to be approx- imately 2:1. State briefly a type of experiment at the surface which could detect these neutrinos, name the type of interaction that takes place and state how the experiment distinguishes between electron and muon neutrinos. Explain whether the experiment is ex- pected to observe the electron and muon neutrino ratio approximately as calculated above. d) The primary cosmic rays can also produce a 7º, which decays into two photons. A π is produced in 15 km altitude with an energy of E(70) = 100 GeV. Describe the interactions of the decay products with the air and calculate the spatial extension of the phenomenon. How can we detect such a process from the surface of the earth?