A classic sum rule by Das et al. is extended to seven of the low-energy constants Ki, introduced by Urech, which parameterize electromagnetic corrections at chiral order O(ep). Using the spurionâ€¦ (More)

The low-energy Ï€Ï€ amplitude is computed explicitly to two-loop accuracy in the chiral expansion. It depends only on six independent (combinations of) low-energy constants which are not fixed byâ€¦ (More)

We discuss matrix elements of the strangeness changing vector current using their relation, due to analyticity, with Ï€K scattering in the P -wave. We take into account experimental phase-shiftâ€¦ (More)

Electromagnetic decays of the scalar mesons are shown to be constrained by chiral symmetry as a consequence of the fact that, in the chiral limit, the two and threepoint functions< SSâˆ’PP > and< V V Sâ€¦ (More)

The corrections induced by light quark masses to the current algebra result for the Ï€0 lifetime are reexamined. We consider next-to-next-to-leading order corrections and we compute all the one-loopâ€¦ (More)

Information on how fast the < qÌ„q > condensate in QCD-like theories varies as a function of Nf , the number of different flavour massless quarks, can be inferred from real QCD using chiralâ€¦ (More)

We pursue the analysis of a set of generalized DGMLY sum rules for the electromagnetic chiral parameters at order e2p2 and discuss implications for effective Lagrangians with resonances. We exploit aâ€¦ (More)

A sum rule due to Das et al. is reanalyzed using a euclidian space approach and a Pad e resummation procedure. It is shown that the result is essentially determined by the matrix elements ofâ€¦ (More)

We derive constraints on combinations of O(p) chiral coupling constants by matching a recent two-loop calculation of the Ï€K scattering amplitude with a set of sum rules. We examine the validity ofâ€¦ (More)

With the aim of generating new constraints on the OZI suppressed couplings of chiral perturbation theory a set of six equations of the Roy and Steiner type for the Sand P waves of the Ï€K scatteringâ€¦ (More)