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Further study of the pi-pi S-wave isoscalar amplitude below the K - Kbar threshold

R. Kaminski·L. Lesniak·K. Rybicki
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Abstract

We continue the analysis of S-wave production amplitudes for the reaction pi- p -> pi+ pi- n involving the data obtained by the CERN--Cracow-Munich collaboration on a transversely polarized target at 17.2 GeV/c pi- momentum. This study deals with the region below the K - Kbar threshold. In particular, we study the "up-steep" solution containing a narrow S-wave resonance under the rho(770). This solution exhibits a considerable inelasticity (eta) which does not have any physical interpretation. Assuming that this inelasticity behaviour represents an unlikely fluctuation we impose eta = 1 for all data points. This leads to non-physical results in one third of the pi+pi- effective mass bins and in the remaining mass bins some parameters behave in a queer way. The situation is even worse for the "down-steep" solution. We conclude that the 17.2 GeV data cannot be described by a relatively narrow f0(750). The "down-flat" and "up-steep" solutions which easily pass the eta = 1 constraint exhibit a slow increase of phase shifts in the rho(770) mass range.

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R. Kaminski, L. Lesniak, K. Rybicki. 1999-12-17. Further study of the pi-pi S-wave isoscalar amplitude below the K - Kbar threshold. https://arxiv.org/abs/hep-ph/9912354

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