Determination of two-loop ππ scattering amplitude parameters
نویسندگان
چکیده
منابع مشابه
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....
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A family of threshold parameters which probe the stability of chiral predictions is considered. The relevant criteria for the choice of threshold parameters are discussed. Sum rules for these quantities are derived from dispersion relations and evaluated from effective range formulae. Good agreement with two-loop chiral estimates for many of these quantities is found and interesting discrepanci...
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We discuss ππ scattering in the framework of chiral perturbation theory. In particular, we recall the predictions [1] for the threshold parameters and for the phase shift difference δ 0 − δ 1 1 . 1 Notation The scattering amplitude for ππ scattering, π(p1)π (p2) → π (p3)π (p4) , reads 〈π(p4)π (p3)out|π (p1)π (p2)in〉 = 〈π (p4)π (p3)in|π (p1)π (p2)in〉 + i(2π)δ(Pf − Pi)T (s, t, u) , where T (s, t,...
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By using the Renormalization Group Equations in Chiral Perturbation Theory, one can calculate the double chiral logs that appear at two loops in any matrix element. We calculate them in the ππ scattering amplitude, where they represent the potentially largest two loop contribution. It is shown that their correction is reasonably small. ♯ Work supported in part by Schweizerischer Nationalfonds/ ...
متن کاملThe Inverse Amplitude Method in ππ Scattering in Chiral Perturbation Theory to Two Loops
The inverse amplitude method is used to unitarize the two loop ππ scattering amplitudes of SU(2) Chiral Perturbation Theory in the I = 0, J = 0, I = 1, J = 1 and I = 2, J = 0 channels. An error analysis in terms of the low energy one-loop parameters l̄1,2,3,4, and existing experimental data is undertaken. A comparison to standard resonance saturation values for the two loop coefficients b̄1,2,3,4...
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ژورنال
عنوان ژورنال: Nuclear Physics B
سال: 1996
ISSN: 0550-3213
DOI: 10.1016/0550-3213(96)00187-3