München 2006 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 56: Elektromagnetische und Hadronische Sonden

HK 56.6: Vortrag

Freitag, 24. März 2006, 15:30–15:45, F

Study of the reaction pi+pi-gamma at KLOE — •Debora Leone — Institute fuer Experimentelle Kernphysik, Universitaet Karlsruhe, Postfach 3640, 76021 Karlsruhe

The KLOE experiment at the electron-positron collider DAPHNE has recently proven the feasibility of using initial state radiation (ISR) in e+e- annihilations for precision measurements of the hadronic cross section. This new method, dubbed Radiative Return, allows us to measure hadronic cross sections over a variable energy range M^2(hadr)$<$s at particle factories which operate at a fixed centre-of-mass energy s. In the recently published KLOE measurement of the pion form factor, the events used had been where the ISR photon is emitted at small polar angles, which reduces background from FSR but leads to a suppression of the threshold region $M^2(pi+pi-) < 0.35 GeV^2. We are now performing a complementary analysis using events using ISR photons emitted at large angles to the beam, hence are tagged and the threshold region becomes accessible. Preliminary results for the cross section are presented, as well as a measurement of the charge asymmetry, which allows a unique test of the FSR model used for the description of the photon radiation from pions.