At the -factories

PHYSICS · Multi-part · Fermi University Physics · Particle Physics & Quantum Fields · Particles, interactions and experiment · Interacting fields, Feynman diagrams and QED

Symmetry and Flavour, Ch From amplitude to rate: Lorentz-invariant phase space, widths and cross sections

Problem

At the

B

-factories,

e^+e^-

collisions occur at

\sqrt s = 10.58\,\mathrm{GeV}

(the

\Upsilon(4S)

energy). Treating

e^+e^-\to\mu^+\mu^-

as pure QED and using the result

\sigma = 86.8\,\mathrm{nb}/(s/\mathrm{GeV^2})

, ((a)) calculate the predicted cross section in picobarns at this energy. ((b)) the BaBar experiment collected an integrated luminosity of

500\,\mathrm{fb^{-1}}

over its running. Estimate how many

\mu^+\mu^-

pairs this process alone produced.

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