Darmstadt 2008 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 2: Elektromagnetische und Hadronische Sonden

HK 2.3: Vortrag

Montag, 10. März 2008, 14:45–15:00, 1C

New measurements of the σ(e⁺e⁻→π⁺π⁻γ) cross section and
extractions of |F_π|² and a_µ^ππ with the KLOE experiment — •Paolo Beltrame — IEKP - University of Karlsruhe (KIT)

The KLOE experiment at the φ factory DAΦNE is using ISR to measure σ(e⁺e⁻→π⁺π⁻γ) and σ(e⁺e⁻→µ⁺µ⁻γ), with an absolute normalisation obtained from Bhabha scattering. ππγ events are obtained with two different selection criteria: (a) requiring photon emission at small angles (SA) (b) tagged photons detected in the calorimeter (LA). With the two samples we cover the complete range of 2m_π <√s′ = M_ππ < m_φ. Using a theoretical radiator function H(s) we extract the pion form factor |F_π|² and obtain the two-pion contribution to a_µ^had. An alternative way to obtain |F_π|² is via the ratio of σ(e⁺e⁻→π⁺π⁻γ) over σ(e⁺e⁻→µ⁺µ⁻γ). Results to be presented come from the analysis of 240 pb⁻¹ collected in 2002, with very small statistical error (∼0.1%) and improved systematic uncertainties (∼1%). Furthermore, using a run of 200 pb⁻¹ of data taken at √s=1 GeV, we can minimize the contribution of resonant background processes.