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T: Fachverband Teilchenphysik

T 95: Flavour-Physik

T 95.6: Talk

Thursday, March 3, 2016, 18:00–18:15, VMP6 HS F

Branching fraction measurement of the very rare decay K^±→ µ^±ν_µe⁺ e⁻ — •Radoslav Marchevski for the NA62 collaboration — Johannes Gutenberg Universität, Mainz, Germany

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 the biggest part 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 measurement of the 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.