The reaction e + + e μ + + μ is studied using a collider with equal

The reaction e⁺+ e^ˆ’†’ μ⁺+ μ^ˆ’is studied using a collider with equal beam energies of 3 GeV. The differential cross-section in natural units is given by

where E_CM is the total centre-of-mass energy and θ is the angle between the initial e^ˆ’ and the final μ^ˆ’. If the detector can only record an event if the μ⁺μ^ˆ’ pair makes an angle of at least 25⁰ relative to the beam line, what fraction of events will be recorded? What is the total cross-section for this reaction in nanobarns? If the reaction is recorded for 10⁷ s at a luminosity of L = 10³¹/cm² s, how many events are expected?

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a? (1+ cos² 0), AECM do UP 4E?