Renormalization of the and scalar resonances in a nuclear medium

Abstract

The meson meson interaction in the scalar sector in the presence of a nuclear medium is studied with particular attention to the change of the properties of the f 0 (980) and a 0 (980) resonances. By using a chiral unitary approach which generates the f 0 and a 0 resonances and reproduces their free properties, we find that the position of the resonances in the medium is barely changed but their widths are considerably broadened. New many body corrections generating from higher orders in the chiral Lagrangian plus the contribution from N*h excitations, not considered before in connection with the ππ interaction in the nuclear medium, are also investigated.

Chiral approach to the rho meson in nuclear matter

“…This approach combines constraints from chiral symmetry breaking and unitarity, and has proved very successful in describing mesonic properties in vacuum at low and intermediate energies [26]. The effects of the nuclear medium on the mesons have already been analyzed in this framework, for the scalar isoscalar (I = J = 0), "σ" channel [27,28]. There have been several attempts to translate the nuclear matter results into observable magnitudes, which can be compared with experimental results [29,30].…”

General properties of the pion production reaction in nuclear matter

“…The phase space of the 45 Sc(π + , π + π ± N ) 44 X reactions are represented by the shaded diagrams. The curves are from [15,16,17] data (full squares) in the lower panels are the ππ invariant mass distributions in deuterium, namely, of the elementary reactions π + n(p) → π + π − p(p) and π + p(n) → π + π + n(n) [7]. The data are compared with the model predictions (full line) described in Sec.…”

“…Furthermore, the nuclear medium does not appreciably change the ππ interaction in the I=2 J=0 channel with respect to the vacuum. [15,16,17]. The pion incident energy is given in each panel.…”

“…Θ π + π − is characterised by a negligible strength below ∼ 60 • . In this angular span, the strength [15,16,17].…”

“…13, is the kinetic energy of a single pion. In the π + → π + π − channel, positive (full diamonds) and negative (open [15,16,17]. diamonds) pion distributions can barely be distinguished throughout the energy range examined.…”