Download Physics 2115 Nuclear Physics

Physics 2115 Elementary Particles and Cosmology
Final Homework Assignment
Answer the following 5 QUESTIONS. Submit at Final Exam.
Not only particles such as electron and protons, but also entire atoms can be classified as
fermions or bosons, depending on whether their overall spin quantum numbers are
respectively, half-integer or integer. Consider the helium isotopes 3He and 4He. Which
of following statements is correct?
a. Both are fermions.
b. Both are bosons.
c. 4He is a fermion and 3He is a boson.
d. 3He is a fermion and 4He is a boson.
(The two helium electrons form a closed shell and play no role in this
determination.)
2. An electron cannot decay into two neutrinos. Which of the following
conservation laws would be violated if it did?
a. Energy
b. Angular Momentum
c. Charge
d. Lepton Number
e. Linear Momentum
f. Baryon Number
3. A proton cannot decay into two neutrinos. Which of the following conservation
laws would be violated if it did?
a. Energy (assume the proton is stationary)
b. Angular Momentum
c. Charge
d. Lepton Number
e. Linear Momentum
f. Baryon Number
4. Consider a neutrino whose symbol is   . Is it (a) quark, a lepton, a meson, or a
baryon? (b) Is it a particle or an anti-particle? (c) Is it a boson or a fermion? (d)
Is it stable against spontaneous decay?
5. A + particle has these quantum numbers: strangeness S = –1, charge q = +1, and
spin s = ½. Which of the following quark combinations produces it?
a. DDS
b. S S
c. UUS
d. SSU
e. UU S