Precision measurement of the form factors of the charged kaon semileptonic decays $K^\pm_{l3}$ by the NA48/2 experiment at CERN

The final result on the charged kaon semileptonic form factors from the NA48/2 experiment is presented. The measurement is based on 4.28 million $K^{\pm}_{e3}$ and 2.91 million $K^{\pm}_{\mu 3}$ events collected in 2004 with very low background ($< 0.1 \%$ and $\sim 0.2 \%$, respectively). The joint analysis of these samples provides the most precise combined measurement of $K^{\pm}_{l3}$ form factors.