= SPEAR psi energy-scan experiment
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At SPEAR, counterrotating <Electron> and <Positron> beams collided inside a magnetic <particle detector>. Finer steps in stored-beam <energy> resolved a sharp production peak. A magnetometer and measured orbit positions monitored the energy settings; <Bhabha scattering> normalized the <cross sections>. The paper attributed the observed width to beam-energy spread and radiation effects, reporting an upper limit on intrinsic width. Its <muon> identification system was not functioning: the non-electron two-body excess was not conclusively a <muon> pair.<Discovery of a Narrow Resonance in e+e- Annihilation by J.-E. Augustin>[Discovery of a Narrow Resonance in electron–positron Annihilation, pp. 1406–1408: scan, energy monitoring, normalization, width limit and two-body identification caveat]{ref}
A scan must compare normalized production rates, since more selected events can result from more beam encounters or different <detection efficiency>. A proposed diagnostic is to revisit energies on either side of the peak while monitoring the energy calibration and event selection. Such neighboring settings test the local production background; their event totals alone are not an independent measurement of the intrinsic <decay width>.
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