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T: Fachverband Teilchenphysik

T 90: Seltene Zerfälle II

T 90.4: Talk

Thursday, March 12, 2015, 17:30–17:45, L.09.21 (HS 13)

Precise Measurement of the very rare Decay K^±→ µ^±ν_µe⁺ e⁻ — •Radoslav Marchevski — JGU Mainz

The rare decay K^±→ µ^±ν_µe⁺ e⁻ proceeds via a K^±→ µ^±ν_µ decay with a radiated photon, which subsequently undergoes an internal conversion. While most of the decay rate is due to final state radiation from the outgoing muon, events with high invariant e⁺e⁻ masses give access to direct photon emission from the weak vertex.

The NA48/2 Collaboration has collected the world largest sample on K^± decays. We report the precise measurement of the K^±→ µ^±ν_µe⁺ e⁻ branching fraction for m_ee > 140 MeV/c² and compare the result to the predictions of Chiral Perturbation Theory. The simultaneous collection of K⁺ and K⁻ decays in the NA48/2 experiment in addition allows the search for CP violation in this decay.