Pion production in heavy ion reactions near absolute thresholds

Conference · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5254455

Stachel, J; Braun-Munzinger, P; Paul, P; Zhang, P H; Obenshain, F E; Plasil, F; Young, G R

Pion production in heavy ion collisions at energies below the free nucleon-nucleon threshold, i.e., at energies, where the pion mass exceeds the kinetic energy of a projectile nucleon in the zero momentum frame, has been discussed for a long time in terms of probing the intrinsic Fermi motion in the projectile and target nuclei. However, as the beam energy is lowered, this process gets more and more unlikely and below a certain energy it should not be observed anymore. In a sharp cut-off Fermi gas model this occurs at E/sub lab/=50 MeV/u. However, as long as the total center of mass energy exceeds the pion mass, pions still can be produced by a cooperative sharing of the beam energy of several (or all) projectile nucleons. The experiments presented here are meant to extend the experimental information into that kinematic domain and represent the up to now lowest beam energy, where pion production has been identified unambiguously. The production of a pion of 100 MeV kinematic energy with a 35 MeV/u /sup 14/N beam requires Fermi momenta as high as approx.350 MeV/c or alternatively 60% of the total beam energy. The information from the present experiments together with the results of previous experiments at higher beam energies of 44 MeV/u and 60 to 84 MeV/u allows one to distinguish between the alternative production mechanisms.

• Research Organization: State Univ. of New York, Stony Brook (USA). Dept. of Physics; Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5254455
• Report Number(s): CONF-840882-7; ON: DE85016305
• Country of Publication: United States
• Language: English

Related Subjects

651525* -- Nuclear Properties & Reactions
A=39-58
Experimental-- Nuclear Reactions & Scattering-- (-1987)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ANGULAR DISTRIBUTION
BOSONS
CHARGED-PARTICLE REACTIONS
CROSS SECTIONS
DATA
DISTRIBUTION
ELEMENTARY PARTICLES
ELEMENTS
ENERGY
ENERGY SPECTRA
EXPERIMENTAL DATA
HADRONS
HEAVY ION REACTIONS
INFORMATION
MASS SPECTRA
MESONS
METALS
MULTIPLE PRODUCTION
NICKEL
NITROGEN 14 REACTIONS
NUCLEAR REACTIONS
NUMERICAL DATA
PARTICLE PRODUCTION
PIONIZATION
PIONS
PIONS NEUTRAL
PSEUDOSCALAR MESONS
SPECTRA
THRESHOLD ENERGY
TRANSITION ELEMENTS