Measurement of the absolute branching ratio of the K+→π+π−π+(γ)K+→π+π−π+(γ) decay with the KLOE detector

The absolute branching ratio of the K+→π+π−π+(γ)K+→π+π−π+(γ) decay, inclusive of final-state radiation, has been measured using ∼17 million tagged K+K+ mesons collected with the KLOE detector at DAΦNE, the Frascati ϕ-factory. The result is:BR(K+→π+π−π+(γ))=0.05565±0.00031stat±0.00025systBR(K+→π+π−π+(γ))=0.05565±0.00031stat±0.00025syst a factor ≃ 5 more precise with respect to the previous result. This work completes the program of precision measurements of the dominant kaon branching ratios at KLOE.