Left Hand Singularities, Hadron Form Factors and the Properties of the Sigma Meson

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  • 23 November 2000
Abstract
By applying analyticity and single channel unitarity we derive a new formula which is very useful to analyze the role of the left-hand singularities in hadron form factors and in the determination of the resonance parameters. Chiral perturbation theory is used to estimate the left-hand cut effects in pi pi scattering processes. We find that in the IJ=11 channel the left-hand cut effect is negligible and in the IJ=20 channel the phase shift is dominated by the left-hand cut effect. In the IJ=00 channel the left-hand cut contribution to the phase shift is in the direction opposite to the experimental data and therefore it extrudes the necessity of the existence of the sigma resonance. Both the mass and the width of the sigma resonance are found to be around 550MeV.

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