Searches for Lepton Number Violation and Resonances in the K± → πμμ Decays by NA48/2 at CERN

The NA48/2 experiment at CERN collected a large sample of charged kaon decays into final stateswith multiple charged particles in 2003-2004. A new upper limit on the rate of the leptonnumber violating decayK±→ π∓μ±μ±obtained from this sample is reported: Β(K±→ π∓μ±μ±)< 8.6 × 10-11 at 90% CL.Searches for two-body resonances in the K±→ πμμ decays(includingheavy neutral leptonsN4and inflatonsχ)in the accessible range of massesand lifetimes are also presented.In the absence of a signal, upper limits are set on the productsof branching ratios B(K±→ μ±N4)B(N4→ π∓μ±)and B(K±→ π± χ) B(χ → μ+μ‒) as functions of theresonance mass and lifetime. These limits are in the10-10–10-9 range for resonance lifetimes below 100 p