| Popis: |
We solve a set of integral equations which, exploiting unitarity and analyticity, determine the behaviour of the S- and P-wave phase shifts near threshold in terms of two subtraction constants proportional to the scattering lengths a + 0+ and a + 1+ . These constants also fix the values of the scattering lengths (volumes) and effective ranges a − 0+ , a ± 1− , a − 1+ , b ± 0+ which in turn can be fix the ∑-term. Here we investigate, in particular, the role of b + 0+ in ∑, and the π − p scattering length a π − p 0+ in the light of existing data. |
