Pion-Pion Phase-Shifts and the Value of Quark-Antiquark Condensate in the Chiral Limit
Abstract
We use low energy pion-pion phase-shifts in order to make distinction between the alternatives for the value of the quark-antiquark condensate B0 in the chiral limit. We will consider the amplitude up to and including O(p4) contributions within the Standard and Generalized Chiral Perturbation Theory frameworks. They are unitarized by means of Pad\'e approximants in order to fit experimental phase-shifts in the resonance region. As the best fits correspond to α = β = 1, we conclude that pion-pion phase-shift analysis favors the standard ChPT scenario, which assumes just one, large leading order parameter < q q >_0.
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