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1299_Physics ProblemsTechnical Physics

# 1299_Physics ProblemsTechnical Physics - 640 P46.53...

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640 Particle Physics and Cosmology P46.53 The total energy in neutrinos emitted per second by the Sun is: 0 4 4 1 5 10 1 1 10 11 2 23 . . . a f e j π × L N M O Q P = × W W. Over 10 9 years, the Sun emits 3 6 10 39 . × J in neutrinos. This represents an annihilated mass m c 2 39 3 6 10 = × . J m = × 4 0 10 22 . kg . About 1 part in 50 000 000 of the Sun’s mass, over 10 9 years, has been lost to neutrinos. P46.54 p p p + + + + π X We suppose the protons each have 70.4 MeV of kinetic energy. From conservation of momentum for the collision, particle X has zero momentum and thus zero kinetic energy. Conservation of system energy then requires M c M c M c M c K M c K X p p p p p 2 2 2 2 2 + + = + + + π e j e j M c M c K M c X 2 2 2 2 938 3 2 70 4 139 6 939 5 = + = + = p p MeV MeV MeV MeV π . . . . a f X must be a neutral baryon of rest energy 939.5 MeV. Thus X is a neutron . *P46.55 (a) If 2 N particles are annihilated, the energy released is 2 2 Nmc . The resulting photon momentum is p E c Nmc c Nmc = = = 2 2 2 . Since the momentum of the system is conserved, the
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