Norman H. Fuchs

Determination of two-loop ππ scattering amplitude parameters

The chiral expansion of the ππ amplitude to the order of two loops was expressed in terms of six independent parameters in a previous paper: four of these are shown here to satisfy sum rules. Their derivation, where crossing symmetry plays a key role, is explained. Their convergence properties are studied and their practical evaluation, in terms of the available data on ππ phase shifts above 0.5 GeV, is discussed. Below 0.5 GeV the chiral amplitude itself is employed, such that the parameters are determined in a self-consistent way. Some care is devoted to the estimate of the errors.

Is the quark mass ratio ms/m̂ as large as 25?

Abstract The Dashen-Weinstein sum rule for deviations from the Goldberger-Treiman relation allows a measurement of m s / m . The present data indicate m s / m ⩽10.6±4.2 , implying a considerably lower value of the condensate 〈qq〉 than usually belived. A new precision K N scattering experiment designed in view of a better determination of the coupling constants gΛNK and gΣNK is urgently called for.

Contributions of order O ( m quark 2 ) to K l 3 form factors and unitarity of the CKM matrix

K\pi

MARKOV CHAIN ANALYSIS OF RANDOM WALKS IN DISORDERED MEDIA

scattering and

Direct single-instanton contributions to finite-energy sum rules

K_{\mu 4}

Rotation invariance and the structure of the S-wave ππ cross section

decays are studied at leading order of improved chiral perturbation theory. It is shown that high precision

An experimental test of the single channel Lovelace-Wagner-Veneziano model☆

K_{\mu 4}

Approximate solutions for large transfer matrix problems

experiments at, e.g., DA

A unified quantum-chromodynamics picture of broken chiral symmetry

\Phi