Title: Title
Author: Philippe CHOMAZ
Last saved by: Administrateur
Company: GANIL

Systematics of Isoscalar Giant Resonances in Exotic Nuclei

Abstract  
The study of the Isoscalar Giant Monopole Resonance (GMR) can give a handle on the nuclear matter equation of state through its link to the nuclear matter incompressibility
The measurement of the GMR and GQR in unstable nuclei remains a major experimental challenge due to low radioactive beam intensities and unfavourable conditions in reverse kinematics. We propose an experimental set-up based on the unique capabilities of active targets, such as MAYA, to measure GMR and GQR in exotic nuclei.

Keywords 
Giant Monopole and Quadrupole Resonance, Nuclear Matter Incompressibility, Nuclear Matter Equation of State, Inelastic d and α scattering

Physics case
 	In addition to being of intrinsic interest like any other collective motion, the study of the GMR is especially important because it relates to the nuclear matter incompressibility K_∞ . 
Since the breathing mode corresponds to small density variations, the monopole energy is a relevant experimental observable to constrain the effective force entering in microscopic calculations of the compressibility. In particular, studying this mode far from stability is expected to characterise the asymmetry energy term of the effective force.
 	The nuclear matter incompressibility is of fundamental importance in describing the nuclear matter : K_∞ is the curvature of the equation of state around the saturation point. It is also a basic parameter in calculations describing neutron stars and supernovae explosions.

Observable
The best probe of the GMR is inelastic scattering of deuterons or alphas. The excitation energy spectra of the studied nucleus and angular distribution must be observed to characterise the GMR and GQR.

Proposed experiment
To measure the GMR and GQR we propose to performe inelastic scattering of deuterons or alphas. 
It is well known that the Giant Resonance cross-sections are peaked at zero degrees in the center of mass frame. In reverse kinematics, it implies to detect deuteron or alpha at very low energies, over a large angular range. With respect to these experimental constraints an active target such as MAYA[1] could be the key to measuring the GMR in unstable nuclei. Low energy recoil particles will be detected in the active target and for higher energy (E>2 MeV) escaping recoils ancillary detectors will be used outside the active volume. For normalization purposes the beam will be counted in a diamond detector for example after traversing the active target.
 The 3D-reconstruction of recoil trajectories in the active target will provide the kinematics of the inelastic scattering and will yield the excitation energy spectrum of the exotic nucleus and angular distributions.

Requirements:
Beam properties
Beam around 50 AMeV with an intensity of at least 10^4 pps. Small angular divergence (<0.5°). Beam spot of a few mm diameter.

Detection
The key detector of the proposed experiment is an active target such as MAYA. Maya is a time and charge projection chamber in which the detector gas is also the target. It ensures three main decisive features compared to a standard silicon detection set-up: a large angular coverage, a low energy threshold and a much thicker equivalent target.
Nethertheless at very low energies (400 keV) some problems of particle identification and sparks with He gas remain. Some improvements of the MAYA active target are expected with ACTAR, a new active target designed presently by the JRA ACTAR in EURONS.

Theoretical support
Improvement of effective interactions and mean field calculations far from stability.