Köln 2004 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 32: Theory V

HK 32.5: Talk

Wednesday, March 10, 2004, 15:45–16:00, D

σ Meson in the NN Interaction and in the Production Process^∗ — •M. Kaskulov, H. Clement, and E. Doroshkevich — Physikalisches Institut, Universität Tübingen, Germany

Conventionally the scalar-isoscalar NN interaction is treated by σ (or correlated two-pion) exchange, which is lifted on its mass shell in the two-pion production reaction. In the Valencia model [1] the production process in the near-threshold region proceeds nearly exclusively via the excitation of the Roper resonance with its successive decay into Δπ and Nσ, with the relative branching of these decay routes being adjusted to data [2]. However, in these calculations no dynamic ππ correlations have been taken into account for the sigma channel. In our ansatz for this problem we include ππ rescattering in agreement with ππ phase shifts both in σ exchange and in σ production. In the first case this leads to an extra, repulsive, potential term, which improves the description of higher partial waves. In the latter case we obtain a quantitative description of the experimental differential data for the pp → ppπ⁺π⁻ reaction close to threshold without invoking explicitely excitation and decay of the Roper resonance.

[1] L. Alvarez-Ruso et al., Nucl. Phys. A633, 519 (1998)

[2] W. Brodowski et al., PRL 88, 192301 (2002); PRC 67, 052202(R) (2003) ^∗supported by BMBF (06 TU 201), DFG (Europ. Graduiertenkolleg) and Landesforschungsschwerpunkt ( Quasiteilchen )