Question

1. For an electron, the number of values the spin quantum number Ms can take on is; Three, four, one, two?

2. what is the threshold energy for the production of an proton-antiproton pair? Emin= MeV

Answer 1

1) answer is two ,( one is +1/2 and other is -1/2)

where m_s is the secondary spin quantum number, ranging from −s to +s in steps of one. This generates 2 s + 1 different values of m_s.

The allowed values for s are non-negative integers or half-integers. Fermions (such as the electron, proton or neutron) have half-integer values, whereas bosons (e.g., photon, mesons) have integer spin values.

2)

If we get an extremely energetic beam of protons. Then, we collide one proton A of the beam with another proton B, at rest. If the kinetic energy is enough, we can create a proton-antiproton pair! The question is, what is the minimum (total) energy, sometimes called threshold energy?What is the minimum kinetic energy, or threshold kinetic energy? And what is the velocity of the incident proton A in order to get the pair production? We are going to solve this really nice problem.

The proton B at rest has and then .

Note that we have and , for the system after the collision when the pair is created.

Using the formulae we have studied

and thus

and this is approximate 2GeV