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Homework Help: Help with Nuclear processes with the rules of quantum physics

  1. May 22, 2012 #1
    1. The problem statement, all variables and given/known data
    The nuclear processes obey certain rules. I.e.
    Conservation of energy and mass
    Conservation of charge
    Conservation of spin
    Conservation of momentum
    Conservation of lepton and baryon numbers

    Use the following examples to discuss these various rules in the following situations:

    1. The positron (beta plus) decay of oxygen -16 to nitrogen -16

    2. Thermal neutron fission of uranium -235

    3. The interaction of a gamma ray photon with a nucleus in a bubble chamber liquid to produce an electron positron pair

    4. It is suggested that a proton can react with a pi particle to form a kaon. The quark compositions of these mesons are K0 down plus anti strange and pi down and anti up. Deduce whether the reaction is possible.

    2. Relevant equations
    Question 4.
    p+ + π - --> K0 + n0

    3. The attempt at a solution

    I understand each of the laws briefly. Im unsure how to explain the answers.

    Heres my answer for Q1:
    In β+ decay, or "positron emission", the weak interaction converts a nucleus into its next-lower neighbour on the periodic table while emitting an positron (e+) and an electron neutrino (νe). If oxygen-16 was to undergo positron emission (beta plus decay), a proton in its nucleus would transform into a neutron (mediated by the weak force). The oxygen-16 would become nitrogen-16, and we'd see a positron and a neutrino appear. This obeys the law of conservation of energy as; Albert Einstein announced his discovery of the equation E = mc2 and the Law of Conservation of Mass-Energy: the total amount of mass and energy in the universe is constant. In this beta decay the mass remains constant.
  2. jcsd
  3. May 22, 2012 #2
    what couldn't you answer on your own?
  4. May 23, 2012 #3
    The 4th question is what im really stuck on. I dont understand the quark compositions of these mesons are K0 down plus anti strange and pi down and anti up.

    And wether the reaction is even possible. I thought the reaction would need 2 π particles?
  5. May 23, 2012 #4
    Why 2 πs?

    p + π- gives n0 K0

    in quark level that is:
    (udu)+(u*d) --> (udd)+(s* d)

    with * i indicate the anti particle, and the way i wrote the quarks will allow you to see that a u* and a u from the initial particles, anihilliate, and create something that afterwards becomes d s*.
    This in a Feynman Diagram can be shown much easier.
    That something must be "chargeless" and at the same time it can allow the change of flavor (cos you get from something strangeless something that has a strange quark). Now is this possible or impossible?
  6. May 24, 2012 #5
    Because a plus and minus = equal?

    I dont understand the anti strange and anti up.
  7. May 25, 2012 #6
    each quark has its antiquark pair, which have opposite quantum numbers (charge,flavor,baryonic number,...). It is like electron-positron. So for up there is the antiup, for down there is the antidown, for strange there is the antstrange, and so on for c,b,t.

    What you must think about is whether the strangeness can change during an interaction.
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