Subthreshold pion production in the reaction sup 139 La + sup 139 La yields. pi. sup + + X

Thesis/Dissertation · Thu Jan 01 00:00:00 EST 1987

OSTI ID:5467216

Miller, J

Charged pion production has been measured in the reaction of {sup 139}La + {sup 139}La{yields} {pi}{sup {plus minus}} + X at three bean energies (246, 183 and 138 MeV/nucleon) below the nucleon-nucleon threshold. Associated multiplicity for charged participants was obtained using a 110-element scintillator multiplicity array. Data were taken over the angular range of 21{degree}-67{degree} in the laboratory (equivalent to 30{degree}-90{degree} in the center of mass). Dependence of the spectra upon pion charge, energy and angle, beam energy, system mass and associated multiplicity was investigated. Based on the isotropic angular distributions and the associated multiplicities for pion production, it appears that subthreshold pions in the range of the experiment are produced predominantly from a source at rest in the center of mass and involving a large number of nucleons. The general character of the subthreshold pion spectra is comparable to previous results above threshold. However, the scaling of the subthreshold pion yield with system mass deviates from the dependence observed in light systems, to an extent which cannot be explained by a simple nucleon-nucleon model. Charge dependent structure in the pion spectra was also found, which was analyzed in the framework of both Coulomb distortion and clustering models. It was concluded that while evidence of collective effects in subthreshold pion production was not clear, it would be very worthwhile to conduct a systematic investigation of pion production for all charge states and over a range of angles, system masses and beam energies, below threshold.

• Research Organization: California Univ., Davis, CA (USA)
• OSTI ID: 5467216
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
LANTHANUM 139 REACTIONS
PIONIZATION
LANTHANUM 139 TARGET
ANGULAR DISTRIBUTION
CLUSTER EMISSION MODEL
MESONS
MEV RANGE 100-1000
MULTIPLICITY
PIONS MINUS
PIONS PLUS
THRESHOLD ENERGY
BOSONS
CHARGED-PARTICLE REACTIONS
DISTRIBUTION
ELEMENTARY PARTICLES
ENERGY
ENERGY RANGE
HADRONS
HEAVY ION REACTIONS
MATHEMATICAL MODELS
MEV RANGE
MULTIPERIPHERAL MODEL
MULTIPLE PRODUCTION
NUCLEAR REACTIONS
PARTICLE MODELS
PARTICLE PRODUCTION
PERIPHERAL MODELS
PIONS
PSEUDOSCALAR MESONS
TARGETS
651720* - Nuclear Properties & Reactions
A=90-149
Experimental