1156_PartUniversity Physics Solution

# 1156_PartUniversity Physics Solution - Particle Physics and...

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Particle Physics and Cosmology 44-9 (c) 2 ph e 22 Em c = so 2 ph e c = ph hc E λ = so 2 e hc mc = and 34 31 8 e 6.63 10 J s 2.43 pm (9.11 10 kg)(3.00 10 m/s) h ×⋅ == = ×× These are gamma ray photons. EVALUATE: The total charge of the electron/positron system is zero and the photons have no charge, so charge is conserved in the particle-antiparticle annihilation. 44.50. (a) If the π decays, it must end in an electron and neutrinos. The rest energy of (139.6 MeV) is shared between the electron rest energy (0.511 MeV) and kinetic energy (assuming the neutrino masses are negligible). So the energy released is 139.6 MeV – 0.511 MeV = 139.1 MeV. (b) Conservation of momentum leads to the neutrinos carrying away most of the energy. 44.51. (a) The baryon number is 0, the charge is e + , the strangeness is 1, all lepton numbers are zero, and the particle is . K + (b) The baryon number is 0, the charge is e , the strangeness is 0, all lepton numbers are zero, and the particle is . (c) The baryon numbers is –1, the charge is 0, the strangeness is zero, all lepton numbers are 0, and the particle is an antineutron. (d) The baryon number is 0, the charge is e + , the strangeness is 0, the muonic lepton number is –1, all other lepton numbers are 0, and the particle is . μ + 44.52. 34 21 14 21 1.054 10 J s 7 . 61 0 s 1 . 3 91 0 J 8 7k eV 7.6 10 s tE t −− Δ= × = = × = Δ× = . 5 2 0.087 MeV 2.8 10 . 3097 MeV ψ E Δ × 44.53. 34 22 9 (1.054 10 J s) 1.5 10 s. (4.4 10 eV)(1.6 10 J/eV) E × × = 44.54. IDENTIFY and SET UP: + KK . φ →+ The total energy released is the energy equivalent of the mass decrease. (a) EXECUTE: The mass decrease is + () (K) . mm m The energy equivalent of the mass decrease is + 2 . mc mc mc The rest mass energy 2 mc for the meson is given in Problem 44.53, and the values for + Kand K are given in Table 44.3. The energy released then is 1019.4 MeV 2(493.7 MeV) −= 32.0 MeV. The + K gets half this, 16.0 MeV.

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1156_PartUniversity Physics Solution - Particle Physics and...

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