Statistical and Dynamical Aspects of Intermediate Energy Nuclear Collisions
(1997) In Cosmic and Subatomic Physics Dissertation Abstract
 Studies of intermediate energy heavy ion reactions have revealed the existence of a number of reducibility and thermal scaling properties in nuclear multifragmentation. In particular, the probability of emitting nfragments is reducible to the probability of emitting a single fragment through the binomial distribution. The resulting onefragment probability shows a dependence on the thermal energy that is characteristic of statistical decay. Similarly, the charge distributions associated with nfragment emission are reducible to the onefragment charge distribution, and thermal scaling is observed. Binomial and Poisson simulations of multifragment decay confirm the above experimental findings.
The reducibility equation... (More)  Studies of intermediate energy heavy ion reactions have revealed the existence of a number of reducibility and thermal scaling properties in nuclear multifragmentation. In particular, the probability of emitting nfragments is reducible to the probability of emitting a single fragment through the binomial distribution. The resulting onefragment probability shows a dependence on the thermal energy that is characteristic of statistical decay. Similarly, the charge distributions associated with nfragment emission are reducible to the onefragment charge distribution, and thermal scaling is observed. Binomial and Poisson simulations of multifragment decay confirm the above experimental findings.
The reducibility equation for the nfragment charge distributions contains a quantity with a value that starts from zero, at low transverse energies, and saturates at high transverse energies. This evolution may signal a transition from a coexistence phase to a vapor phase. In the search for a signal of liquidgas phase transition, the appearance of intermittency is reconsidered. Percolation calculations, as well as data analysis, indicate that an intermittentlike signal appears from classes of events that do not coincide with the critical one.
Information about the dynamical evolution of nuclear sources formed in intermediate energy heavy ion collisions can be gained by means of intensity interferometry. In particular, simultaneous neutronneutron, protonneutron and protonproton interferometry measurements are interesting, since different effects participate differently in the correlations between different types of particle pairs. The simultaneous measurement of particles with nearly equal momenta is a very delicate experimental task, and in particular twoneutron interferometry is plagued by instrumental problems, such as low detection efficiency, background noise and neutron rescattering between detectors (crosstalk). The strength of the measured correlation functions is found to depend on the energy of the particle pair. The measured protonneutron correlation function shows less strength than expected, possibly due to the Coulomb interaction of the proton with the emitting source.
The dynamical aspects of nuclear collisions can be probed by studying meson production. Complete pion production excitation functions can be measured in rampedbeam experiments at storage rings. In such experiments, particular attention must be payed to the delicate problem of translating the measured yields into absolute cross sections. Information on the pion production mechanism can be obtained by comparison of the measured yields with predictions from different model calculations. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/record/29024
 author
 Ghetti, Roberta ^{LU}
 opponent

 Prof BraunMunzinger, Peter, GSI Darmstadt, Germany
 organization
 publishing date
 1997
 type
 Thesis
 publication status
 published
 subject
 keywords
 excitation function., subthreshold pions, pion production, neutron crosstalk, correlation function, interferometry, intermittency, phase transition, thermal scaling, reducibility, multifragmentation, Heavy ion collisions, intermediate energy, Atomic and molecular physics, Atom och molekylärfysik
 in
 Cosmic and Subatomic Physics Dissertation
 pages
 184 pages
 publisher
 Experimental HighEnergy Physics
 defense location
 Department of Physics (Sal B)
 defense date
 19970228 10:15
 external identifiers

 other:ISRN: LUNFD6/NFFK1012SE+184P
 ISSN
 11014202
 ISBN
 919730770X
 language
 English
 LU publication?
 yes
 id
 6ac64d2076a84fed9356c2d02be0b0c6 (old id 29024)
 date added to LUP
 20070612 13:35:06
 date last changed
 20160919 08:44:54
@phdthesis{6ac64d2076a84fed9356c2d02be0b0c6, abstract = {Studies of intermediate energy heavy ion reactions have revealed the existence of a number of reducibility and thermal scaling properties in nuclear multifragmentation. In particular, the probability of emitting nfragments is reducible to the probability of emitting a single fragment through the binomial distribution. The resulting onefragment probability shows a dependence on the thermal energy that is characteristic of statistical decay. Similarly, the charge distributions associated with nfragment emission are reducible to the onefragment charge distribution, and thermal scaling is observed. Binomial and Poisson simulations of multifragment decay confirm the above experimental findings.<br/><br> <br/><br> The reducibility equation for the nfragment charge distributions contains a quantity with a value that starts from zero, at low transverse energies, and saturates at high transverse energies. This evolution may signal a transition from a coexistence phase to a vapor phase. In the search for a signal of liquidgas phase transition, the appearance of intermittency is reconsidered. Percolation calculations, as well as data analysis, indicate that an intermittentlike signal appears from classes of events that do not coincide with the critical one.<br/><br> <br/><br> Information about the dynamical evolution of nuclear sources formed in intermediate energy heavy ion collisions can be gained by means of intensity interferometry. In particular, simultaneous neutronneutron, protonneutron and protonproton interferometry measurements are interesting, since different effects participate differently in the correlations between different types of particle pairs. The simultaneous measurement of particles with nearly equal momenta is a very delicate experimental task, and in particular twoneutron interferometry is plagued by instrumental problems, such as low detection efficiency, background noise and neutron rescattering between detectors (crosstalk). The strength of the measured correlation functions is found to depend on the energy of the particle pair. The measured protonneutron correlation function shows less strength than expected, possibly due to the Coulomb interaction of the proton with the emitting source.<br/><br> <br/><br> The dynamical aspects of nuclear collisions can be probed by studying meson production. Complete pion production excitation functions can be measured in rampedbeam experiments at storage rings. In such experiments, particular attention must be payed to the delicate problem of translating the measured yields into absolute cross sections. Information on the pion production mechanism can be obtained by comparison of the measured yields with predictions from different model calculations.}, author = {Ghetti, Roberta}, isbn = {919730770X}, issn = {11014202}, keyword = {excitation function.,subthreshold pions,pion production,neutron crosstalk,correlation function,interferometry,intermittency,phase transition,thermal scaling,reducibility,multifragmentation,Heavy ion collisions,intermediate energy,Atomic and molecular physics,Atom och molekylärfysik}, language = {eng}, pages = {184}, publisher = {Experimental HighEnergy Physics}, school = {Lund University}, series = {Cosmic and Subatomic Physics Dissertation}, title = {Statistical and Dynamical Aspects of Intermediate Energy Nuclear Collisions}, year = {1997}, }