# hw9 - Physics 226 Assignment#9 Due Wednesday June 3 2015...

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Physics 226 Assignment #9 May 27, 2015 Due Wednesday, June 3, 2015 Due Friday, June 5, 2015 1. (5 pts) Terminology: scalar means J = 0, vector means J = 1, isoscalar means I = 0, isodoublet means I = 1 / 2, isovector means I = 1, strange means having S 6 = 0. Decuplet baryons refers to the 10 lightest J = 3 / 2 baryons made from u , d , and s quarks. Octet baryons refers to the 8 lightest J = 1 / 2 baryons made from u , d , and s quarks. “ How does it decay? ” means give both the (dominant) decay products and the interactions responsible. (a) What is the isovector octet baryon with I 3 = - 1? How does it decay? (b) Are there any isoscalar strange mesons? (c) What is the isovector decuplet antibaryon with I 3 = - 1? How does it decay? (d) What are the lightest vector isodoublet mesons? How do they decay? (e) What is the doubly strange ( S = 2) antibaryon with smallest I 3 ? How does it decay? 2. (7 pts) At high energy, E c . m . m μ c 2 , the cross-section for e + e - μ + μ - scattering due to electromagnetic interactions must have the form σ = C ~ a c b α p /s q , for some exponents a, b, p, q and overall dimensionless coefficient C , which turns out to equal 4 π/ 3. Here α e 2 / (4 π 0 ~ c ) is the fine structure constant, and s ≡ - ( p e

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