The KLOE experiment at the φ - factory DAΦNE in Frascati near Rome is the first to have employed Initial State Radiation (ISR) to precisely determine the e +e -→π +π -(γ) cross section below 1 GeV. Such a measurement is particularly important to test the Standard Model (SM) calculation for the (g-2) of the muon, where a long standing 3σ discrepancy is observed.In 2005 and 2008 KLOE published two measurements of the π +π - cross section with the photon emitted at small angles, and an independent measurement of the π +π - cross section with the photon emitted at large angles using data at a collision energy of 1 GeV (i.e., 20 MeV below the φ-peak) was published in 2010. While the measurements were normalized to the DAΦNE luminosity using large angle Bhabha scattering, a new analysis has been performed which derives the pion form factor directly from measuring the bin-by-bin π +π -γ/μ +μ -γ ratio. We present the preliminary results of this new measurement, as well as the previously published ones, and the impact on the evaluation of the hadronic contribution to the muon anomaly

KLOE measurement of with Initial State Radiation and the contribution to the muon anomaly

GIARDINA, Giorgio 42;MANDAGLIO, GIUSEPPE;
2012

Abstract

The KLOE experiment at the φ - factory DAΦNE in Frascati near Rome is the first to have employed Initial State Radiation (ISR) to precisely determine the e +e -→π +π -(γ) cross section below 1 GeV. Such a measurement is particularly important to test the Standard Model (SM) calculation for the (g-2) of the muon, where a long standing 3σ discrepancy is observed.In 2005 and 2008 KLOE published two measurements of the π +π - cross section with the photon emitted at small angles, and an independent measurement of the π +π - cross section with the photon emitted at large angles using data at a collision energy of 1 GeV (i.e., 20 MeV below the φ-peak) was published in 2010. While the measurements were normalized to the DAΦNE luminosity using large angle Bhabha scattering, a new analysis has been performed which derives the pion form factor directly from measuring the bin-by-bin π +π -γ/μ +μ -γ ratio. We present the preliminary results of this new measurement, as well as the previously published ones, and the impact on the evaluation of the hadronic contribution to the muon anomaly
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11570/2124067
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