An meson (spin zero, ) with laboratory energy decays to two photons

PHYSICS · Multi-part · Fermi University Physics · Particle Physics & Quantum Fields · Particles, interactions and experiment · Particles, interactions and experiment

Symmetry and Flavour, Ch Four-vectors at work: boosts, invariants and the shape of a final state

Problem

An η\eta meson (spin zero, mη=547.86 MeVm_\eta = 547.86\,\mathrm{MeV}) with laboratory energy E=20.0 GeVE = 20.0\,\mathrm{GeV} decays to two photons. A calorimeter records a photon only if its energy exceeds a threshold EcE_c. ((a)) Find the smallest possible opening angle between the two photons, in mrad. ((b)) Find the fraction of decays in which both photons are recorded, as a function of EcE_c over the whole range 0≤Ec≤E0\le E_c\le E, and evaluate it for Ec=1.00 GeVE_c = 1.00\,\mathrm{GeV}. ((c)) For Ec=1.00 GeVE_c = 1.00\,\mathrm{GeV}, find the largest opening angle among the recorded decays, in mrad.

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