Improved KL→π±e∓ν form factor and phase space integral with reduced model uncertainty

Using the published KTeV sample of 2x10(6) K-L ->pi(+/-)e(-/+)nu decays 1 and a new form factor expansion with a rigorous bound on higher order terms 2, we present a new determination of the K-L ->pi(+/-)e(-/+)nu form factor and phase space integral. Compared to the previous KTeV result 1, the uncertainty in the new form factor expansion is negligible and results in an overall uncertainty in the phase space integral (I-K(e)) that is a factor of 2 smaller: I-K(e)=0.15392 +/- 0.00048.