Leipzig 2002 – scientific programme

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T: Teilchenphysik

T 106: Test des Standardmodells

T 106.2: Talk

Monday, March 18, 2002, 14:25–14:40, HS 8

Status and first physics results of the KLOE experiment — •Barbara Valeriani — IEKP-Universit"t Karlsruhe Postfach 3640 76021 Karlsruhe

The KLOE experiment at DAΦNE - the e ⁺ e ⁻ collider in Frascati working at the φ(1020 MeV) resonance - has started data taking in 1999. The φ factory DAΦNE and the excellent performances of the detector KLOE allow to cover a wide physics program. First results on kaon decays and on radiative decays of the φ meson are presented.
The measurement of the cross section e ⁺ e ⁻ → π ⁺ π ⁻ has become one of the highlights of the KLOE program after the recent precise measurement of the muon anomalous magnetic moment performed at BNL. A precise theoretical evaluation of a_µ is necessary to isolate possible new physics contributions. KLOE can contribute to reduce the uncertainty of the theoretical determination of a_µ, dominated by the hadronic contribution to the vacuum polarisation by measuring the cross section σ (e ⁺ e ⁻ → π ⁺ π ⁻) in the energy range from the two pion threshold up to the φ mass. This measurement is performed at the fixed energy of DAΦNE of 1020 MeV by studying the π ⁺ π ⁻ γ final state: photons emitted by electrons or positrons in the initial state lower the center of mass energy of the hadronic system.
The measurement is also relevant for a precise theoretical determination of the running electromagnetic coupling constant.