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lthistlewood2013 English 10 cards

Cards in this deck (10)

1Name three quantities that are conserved in all particle reactions.Quantities that are always conserved in particle reactions are charge, baryon number and lepton number.
2What is the baryon number of an electron? Explain your answer.Zero
Why? For baryons, B = +1. For antibaryons B = -1. For all other particles (including electrons), B = 0
3Can this reaction take place? Explain your answerNo, the reaction cannot occur because charge is not conserved.
LHS: Q = +1 + (-1) = 0
RHS: Q = +1 + (+1) = +2
4Can this reaction take place? Explain your answerYes, the reaction can occur because charge, baryon number and lepton number are all conserved.
5Is baryon number conserved in this proposed particle reaction?Yes, baryon number is conserved.
LHS: B = +1 + 0 = +1
RHS: B = 0 + (+1) = +1
6Name these particles, and give their charges and baryon numbers.The first particle is a neutral K meson ('kaon').
The second particle is a positive pi meson ('pion').
Both particles are mesons and, therefore, have baryon numbers of zero (because they are not baryons).
7Name these particles, and give their charges, baryon numbers, and lepton numbersThe particles are (from the left), a neutron, proton, and an antineutron.
Charges are 0, +1 and 0.
The proton and neutron are both baryons and have baryon numbers (B) of +1. The antineutron is an antibaryon and has B = -1.
All three particles have a lepton number of zero (because they are not leptons).
8Is lepton number conserved in this proposed reaction?Yes, lepton number is conserved.
LHS: L = -1 + 0 = -1
RHS: L = -1 + 0 = -1
(The antineutrino and positron are both antileptons)
9Is lepton number conserved in this proposed reaction?No, lepton number is not conserved in either the electron or muon family.
Electron family:
LHS: L = 0 + 0 = 0
RHS: L = 0 + (-1) = (-1)
Muon family:
LHS: L = -1 + 0 = -1
RHS: L = 0 + 0 = 0
10What is the lepton number of a positron? Explain your answer.L = -1
Why?
For leptons, L = +1.
For antileptons (e.g. the positron) L = -1.