Berlin 2005 – scientific programme

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T: Teilchenphysik

T 306: QCD I

T 306.1: Talk

Friday, March 4, 2005, 16:30–16:45, TU H2035

Measurement of the hadronic cross section at KLOE — •Debora Leone — Institut für Exp. Kernphysik, Universität Karlruhe, Postfach 3640, 76021 Karlsruhe

The KLOE-experiment at the electron-positron collider DAΦNE uses the radiative return to measure the hadronic cross section σ(e⁺e⁻ → π⁺π⁻). The energy of DAΦNE is fixed at √s=M_Φ=1020 MeV, but the emission of one (or more) photons in the initial state (ISR) reduces the collision energy, allowing us to cover the two pion inveriant mass M_ππ in the region from the two pions threshold to m_Φ. The precise measurement of this cross section is used to calculate the hadronic contribution to the muon anomaly a_µ. A first measurement, in which thr ISR-photons are detected at small polar angles, has already been performed at KLOE (hep-ex/0407048). Here we present the status of a complementary analysis at large photon polar angles. This allows us to measure the two-pion cross section at low masses below 600 MeV.