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HK: Fachverband Hadronen und Kerne

HK 35: Hadron Structure and Spectroscopy II

HK 35.2: Group Report

Tuesday, March 17, 2009, 17:00–17:30, H-ZO 30

Exclusive hadronic cross sections from BaBar — •Miriam Fritsch — Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, Germany

Measuring the inclusive hadronic cross section in e⁺e⁻ is of major interest for the determination of the Standard Model prediction of the anomalous magnetic moment of the muon a_µ. The hadronic contribution a_µ^had can be derived from measured total cross sections of exclusive hadronic reactions with the help of a dispersion relation. Decreasing the experimental uncertainties on these channels is of utmost importance to improve the Standard Model prediction. The reaction channel e⁺ e⁻ → π⁺ π⁻ has the biggest impact on the calculation.

This talk presents exclusive hadronic cross sections measured with the technique of Initial State Radiation (ISR). A huge dataset was taken with the BaBar detector at the B-factory PEP-II at SLAC (Stanford, USA), an electron-positron storage ring with fixed CM-energy of 10.58 GeV. Using the ISR method we get access to the energy range from the threshold up to 4.5 GeV. The first preliminary measurement of the ππ-channel and other channels important for the the muon anomaly will be presented, as well as the measurement of time-like baryonic form factors.