0439718 - ÚJF 2015 RIV US eng J - Journal Article
Bydžovský, Petr - Kaminski, R. - Nazari, V.
Modified pi pi amplitude with sigma pole.
Physical Review D: Particles, Fields, Gravitation and Cosmology. Roč. 90, č. 11 (2014), s. 116005. ISSN 1550-7998
R&D Projects: GA ČR(CZ) GAP203/12/2126
Institutional support: RVO:61389005
Keywords : scattering data * equation * phase-shifts
Subject RIV: BE - Theoretical Physics
Impact factor: 4.643, year: 2014

A set of well-known once subtracted dispersion relations with imposed crossing symmetry condition is used to modify unitary multichannel S (pi pi, K (K) over bar, and eta eta) and P (pi pi, rho 2 pi, and rho sigma) wave amplitudes mostly below 1 GeV. Before the modifications, these amplitudes significantly did not satisfy the crossing symmetry condition and did not describe the pi pi threshold region. Moreover, the pole of the S wave amplitude related with the f(0)(500) meson (former f(0)(600) or sigma) had much smaller imaginary part and bigger real one in comparison with those in the newest Particle Data Group Tables. Here, these amplitudes are supplemented by near threshold expansion polynomials and refitted to the experimental data in the effective two pion mass from the threshold to 1.8 GeV and to the dispersion relations up to 1.1 GeV. In result the self consistent, i.e., unitary and fulfilling the crossing symmetry condition, S and P wave amplitudes are formed and the sigma pole becomes much narrower and lighter. To eliminate doubts about the uniqueness of the so obtained sigma pole position short and purely mathematical proof of the uniqueness of the results is also presented.
Permanent Link: http://hdl.handle.net/11104/0242939