A study of pion pair production in the two-photon process

Abstract We studied the e + e − →e + e − π + π − interaction with the untagged two-photon sample obtained by the TOPAZ detector at the TRISTAN e + e − collider. The sample was taken in the energy region s =55.0−60.8 GeV . One of the QED backgrounds, e + e − →e + e − , was clearly removed by the measurement of d E /d x by the TOPAZ-TPC. The π + π − invariant mass spectrum is well reproduced by the f 2 (1270) resonance, the Born term and their interference. We determined the radiative width of the f 2 (1270) to be 2.27±0.47(stat.)±0.11(syst.) keV.