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: 04 4 15 10 11 10 11 2 23 .. . a f ej π × L N M O Q P W W . Over 10 9 years, the Sun emits 36 10 39 . × J in neutrinos. This represents an annihilated mass mc 23 9 36 10 . J m 40 10 22 k g . About 1 part in 50 000 000 of the Sun’s mass, over 10 9 years, has been lost to neutrinos. P46.54 pp p +→+ + + 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 Mc M c Mc K X p pppp 22 2 2 2 ++ = + + + Mc Mc K Mc X 22 2 2 938 3 2 70 4 139 6 939 5 =+ −= + = pp MeV MeV MeV MeV ... . 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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This note was uploaded on 12/15/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .

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