Precision measurement of the form factors of the semileptonic decay $K^ \pm \to \pi^0 \ell^\pm \nu$ (Kl3)

The NA48/2 experiment at CERN collected a very large sample of charged kaon decays into multiple final states. This data allow measurements related to QCD. We obtained our final measurement of the charged kaon semileptonic decays form factors based on 4.28 million Ke3 and 2.91 million Kmu3 selected decays, with the smallest uncertainty for Ke3 and a competitive result for Kmu3 and leading to the most precise combined Kl3 result coming from the Kaon sector that reduces the form factor uncertainty of $|V_{us} |$.