Standard Model and Beyond · Problem 5.1

The Strong Interactions and QCD

Physics — Particle Physics · r-ratio-integer-charge-quarks

Problem

The ratio R(s)=σ(e+e−→hadrons)/σ(e+e−→μ+μ−)R(s) = \sigma(e^+e^- \to \text{hadrons})/\sigma(e^+e^- \to \mu^+\mu^-) is mentioned as excluding an alternative quark model involving integer electric charges (Nambu and Han, 1974), under the assumption that the quarks can be treated as pointlike. Calculate the lowest-order prediction for RR in this integer-charge quark model and compare it with the QCD prediction.

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