The quark condensate from K(e(4)) decays

Phys Rev Lett. 2001 May 28;86(22):5008-10. doi: 10.1103/PhysRevLett.86.5008.

Abstract

We show that, independently of the size of the quark condensate, chiral symmetry correlates the two S-wave pipi scattering lengths. In view of this constraint, the new precision data on K(e(4)) decay allow a remarkably accurate determination of these quantities. The result confirms the hypothesis that the quark condensate is the leading order parameter.