a. During the decay of the π meson, two photons with energy ε1 and ε2 were formed, which fly in opposite directions. Determine the decaying meson velocity. The relation between energy and momentum for a photon is ε = pc, where c is the speed of light.
b. During the decay of a neutral particle, two photons are detected flying at angles θ1 and θ2 to the direction of the particle's motion. Determine the speed of the decayed particle.
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