E. Ramakrishnan

Signals for a transition from surface to bulk emission in thermal multifragmentation.

Excitation-energy-gated two-fragment correlation functions have been studied between E(*)/A = (2-9)A MeV for equilibriumlike sources formed in 8-10 GeV/c pi(-) and p+197Au reactions. Comparison with an N-body Coulomb-trajectory code shows an order of magnitude decrease in the fragment emission time in the interval E(*)/A = (2-5)A MeV, followed by a nearly constant breakup time at higher excitation energy. The decrease in emission time is strongly correlated with the onset of multifragmentation and thermally induced radial expansion, consistent with a transition from surface-dominated to bulk emission expected for spinodal decomposition.

Isospin dependence of isobaric ratio and its relation to temperature

Abstract A dependence of the isobaric ratio Y( 3 H)/Y( 3 He ) on the N / Z ratio of the reconstructed quasiprojectile for the reaction of 28 Si beam with 112,124 Sn targets at two different projectile energies of 30 and 50 MeV/nucleon is presented. We demonstrate a linear dependence of the observable ln( Y( 3 H)/Y( 3 He ) ) on the N / Z ratio of the quasiprojectile and show the dependence of the slope on the reconstructed excitation energy of the quasiprojectile. We relate this slope dependence at a given excitation energy to the temperature of the fragmenting system. Using the model assumptions of the statistical multifragmentation model, a method of temperature determination is proposed. A caloric curve is constructed and compared to the result of the double isotope ratio method for the same set of the data and to the results of other studies.

Isospin dependence of isobaric ratio Y(H-3) / Y(He-3) and its possible statistical interpretation

Abstract A dependence of the isobaric ratio Y( 3 H)/Y( 3 He ) on the N / Z ratio of the reconstructed quasiprojectile for the reaction of 28 Si beam with 112,124 Sn targets at two different projectile energies of 30 and 50 MeV/nucleon is presented. We demonstrate a linear dependence of the observable ln( Y( 3 H)/Y( 3 He ) ) on the N / Z ratio of the quasiprojectile and show the dependence of the slope on the reconstructed excitation energy of the quasiprojectile. We relate this slope dependence at a given excitation energy to the temperature of the fragmenting system. Using the model assumptions of the statistical multifragmentation model, a method of temperature determination is proposed. A caloric curve is constructed and compared to the result of the double isotope ratio method for the same set of the data and to the results of other studies.

Breakup time scale studied in the 8 GeV/c pi- + 197Au reaction

Experimental data from the reaction of an 8.0 GeV/c pi- beam incident on a 197Au target have been analyzed in order to investigate the integrated breakup time scale for hot residues. Alpha-particle energy spectra and particle angular distributions supported by a momentum tensor analysis suggest that at large excitation energy, above 3-5 MeV/nucleon, light-charged particles are emitted prior to or at the same time as the emission of the heavy fragments. Comparison with the SMM and GEMINI models is presented. A binary fission-like mechanism fits the experimental data at low excitation energies, but seems unable to reproduce the data at excitation energies above 3-5 MeV/nucleon.

Caloric curve of 8 GeV/c negative pion and antiproton + Au reactions

The relationship between nuclear temperature and excitation energy of hot nuclei formed by 8 GeV/c negative pion and antiproton beams incident on 197Au has been investigated with the ISiS 4-pidetector array at the BNL AGS accelerator. The double-isotope-ratio technique was used to calculate the temperature of the hot system. The two thermometers used (p/d-3He/4He) and (d/t-3He/4He) are in agreement below E*/A ~ 7 MeV when corrected for secondary decay. Comparison of these caloric curves to those from other experiments shows some differences that may be attributable to instrumentation and analysis procedures. The caloric curves from this experiment are also compared with the predictions from the SMM multifragmentation model.

Caloric curve of8GeV/cπ−,p¯+197Aureactions

The relationship between nuclear temperature and excitation energy of hot nuclei formed by 8 GeV/c negative pion and antiproton beams incident on 197Au has been investigated with the ISiS 4-pidetector array at the BNL AGS accelerator. The double-isotope-ratio technique was used to calculate the temperature of the hot system. The two thermometers used (p/d-3He/4He) and (d/t-3He/4He) are in agreement below E*/A ~ 7 MeV when corrected for secondary decay. Comparison of these caloric curves to those from other experiments shows some differences that may be attributable to instrumentation and analysis procedures. The caloric curves from this experiment are also compared with the predictions from the SMM multifragmentation model.

Thermal expansion effects in the 8-GeV/c pi- + Au-197 reaction

Fragment kinetic energy spectra for reactions induced by 8.0 GeV/c

Heating nuclei with 8 GeV/c antiprotons

\rm{\pi^-}

Effects of in-medium cross sections and optical potential on thermal-source formation in p+{sup 197}Au reactions at 6.2-14.6 GeV/c

beams incident on a

Heating of nuclear matter and multifragmentation : antiprotons vs. pions.

\rm{^{197}}