Multifragmentation induced by relativistic α projectiles

Barth, Rolf F.; Oeschler, H.; Avdeyev, S. P.; Karnaukhov, V.A.; Kuznetsov, W.D.; Petrov, L.A.; Bochkarev, O.V.; Chulkov, L. V.; Kuzmin, E. A.; Karcz, W.; Neubert, W.; Norbeck, E.

doi:10.1103/physrevlett.72.1604

Cited by 33 publications

(23 citation statements)

References 12 publications

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“…The experiments using light projectiles of mass A ≤ 4 confirm the finding that very high bombarding energies are needed in asymmetric systems in order to achieve the complete disassembly of a heavy spectator nucleus with large probability [37,38].…”

Section: Fragmentation At High Bombarding Energiessupporting

confidence: 58%

Universality of spectator fragmentation at relativistic bombarding energies

et al. 1996

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Multi-fragment decays of 129 Xe, 197 Au, and 238 U projectiles in collisions with Be, C, Al, Cu, In, Au, and U targets at energies between E/A = 400 MeV and 1000 MeV have been studied with the ALADIN forward-spectrometer at SIS. By adding an array of 84 SiCsI(Tl) telescopes the solid-angle coverage of the setup was extended to θ lab = 16 • . This permitted the complete detection of fragments from the projectile-spectator source.The dominant feature of the systematic set of data is the Z bound universality that is obeyed by the fragment multiplicities and correlations. These observables are invariant with respect to the entrance channel if plotted as a function of Z bound , where Z bound is the sum of the atomic numbers Z i of all projectile fragments with Z i ≥ 2. No significant dependence on the bombarding energy nor on the target mass is observed. The dependence of the fragment multiplicity on the projectile mass follows a linear scaling law.The reasons for and the limits of the observed universality of spectator fragmentation are explored within the realm of the available data and with model studies. It is found that the universal properties should persist up to much higher bombarding energies than explored in this work and that they are consistent with universal features exhibited by the intranuclear cascade and statistical multifragmentation models.

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Section: Fragmentation At High Bombarding Energiessupporting

confidence: 58%

Universality of spectator fragmentation at relativistic bombarding energies

et al. 1996

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“…Heavy ion reactions at relativistic energies offer a wide range of possibilities to study the multi-fragment decay of highly excited nuclei [1][2][3][4][5][6][7][8]. In collisions of heavy nuclei at incident energies exceeding values of about 100 MeV per nucleon [2], highly excited and equilibrated spectator systems are formed which decay by multifragmentation [9] in good agreement with statistical predictions [10,11].…”

Section: Introductionmentioning

confidence: 89%

“…5, the three apparent temperatures defined in eqs. (3)(4)(5) are shown as a function of the equilibrium temperature T input for the parameters N/Z = 1.49 (value of 197 Au) and density ρ = 0.3 · ρ 0 (where ρ 0 is the saturation density of nuclei). The relations between T HeLi,0 or T Hedt,0 and T input are almost linear and the corrections required in these two cases are practically identical, except at the highest temperatures.…”

Section: Experimental Temperaturesmentioning

confidence: 99%

Breakup temperature of target spectators in 197Au + 197Au collisions at E/A = 1000 MeV

Odeh

Bassini

et al. 1997

Z Phys A - Particles and Fields

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Breakup temperatures were deduced from double ratios of isotope yields for target spectators produced in the reaction 197 The good agreement with the breakup temperatures measured previously for projectile spectators at an incident energy of 600 MeV per nucleon confirms the universality established for the spectator decay at relativistic bombarding energies. The measured temperatures also agree with the breakup temperatures predicted by the statistical multifragmentation model. For these calculations a relation between the initial excitation energy and mass was derived which gives good simultaneous agreement for the fragment charge correlations.The energy spectra of light charged particles, measured at θ lab = 150• , exhibit Maxwellian shapes with inverse slope parameters much higher than the breakup temperatures. The statistical multifragmentation model, because Coulomb repulsion and sequential decay processes are included, yields light-particle spectra with inverse slope parameters higher than the breakup temperatures but considerably below the measured values. The systematic behavior of the differences suggests that they are caused by light-charged-particle emission prior to the final breakup stage. Keywords:197 Au projectiles and targets, E/A = 600 and 1000 MeV; measured fragment cross sections, isotopic yield ratios; deduced breakup temperatures, pre-breakup emission; analysis using quantum statistical and statistical multifragmentation models.

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“…Since the pion momenta are comparable to the Fermi momentum of the nucleons in the nucleus, the pions heat the nucleus in a soft radiationlike way [4], probably even softer and more efficient than can be expected in proton-or other lightion-induced spallation reactions, which have also been exploited recently for this purpose [5][6][7].…”

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confidence: 99%

Heating of Nuclei with Energetic Antiprotons

Goldenbaum¹,

Bohne²,

Eades³

et al. 1996

Phys. Rev. Lett.

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The annihilation of energetic (1.2 GeV) antiprotons is exploited to deposit maximum thermal excitation (up to 1000 MeV) in massive nuclei (Cu, Ho, Au, and U) while minimizing the contribution from collective excitation such as rotation, shape distortion, and compression. Excitation energy distributions ds͞dE ‫ء‬ are deduced from eventwise observation of the whole nuclear evaporation chain with two 4p detectors for neutrons and charged particles. The nuclei produced in this way are found to decay predominantly statistically, i.e., by evaporation.[ S0031-9007(96) The study of such decay modes of very highly excited nuclei as fission, multifragmentation, cracking, and vaporization is presently a major objective in nuclear physics because of its bearing on the lesser-known bulk properties of hot nuclear matter, such as heat capacity, specific heat, viscosity, and phase transitions. Unfortunately, the decay pattern is also very sensitive to the dynamics of the excitation process, especially when collective degrees of freedom like rotation, shape distortion, and compression are strongly induced. These may have to be envisaged in the most often used [1-3] heavy-ion reactions. This ambiguity makes it difficult to correlate the observed decay pattern with either thermally or dynamically induced decay.In order to minimize the influence of the entrance channel on the decay modes, we have, for the first time, investigated the nuclear excitation following annihilation of energetic antiprotons. Antiprotons annihilate on a single nucleon at the surface of, or even inside the nucleus, thereby producing a pion cloud containing an average of about 5 particles. Because of the high centerof-mass velocity (b c.m.0.63) of this cloud, it is focused forward into the nucleus. Since the pion momenta are comparable to the Fermi momentum of the nucleons in the nucleus, the pions heat the nucleus in a soft radiationlike way [4], probably even softer and more efficient than can be expected in proton-or other lightion-induced spallation reactions, which have also been exploited recently for this purpose [5][6][7].Intranuclear cascade (INC) calculations have been found to provide a reasonable description of this mechanism. They predict that the spin remains low (below maximum 25h) and that shape distortion and density compression are negligible [8], in contrast to what is expected in heavy-ion reactions. The reaction time for achievement of equilibrium conditions is only about 30 fm͞c or 10 222 s [9], which is much shorter in general than the dynamical period in heavy-ion reactions [10]. This is all the more important at high temperature (T ഠ 6 MeV) when the characteristic evaporation time reduces to t , 10 222 s, implying little cooling of the compound nucleus during heating.In this Letter we concentrate on the use of a new method to determine the thermal excitation energy produced with energetic antiprotons. This method is based on the eventwise observation of the whole nuclear evaporation chain, including both neutrons and charged particles...

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Multifragmentation induced by relativistic α projectiles

Cited by 33 publications

References 12 publications

Universality of spectator fragmentation at relativistic bombarding energies

Universality of spectator fragmentation at relativistic bombarding energies

Breakup temperature of target spectators in 197Au + 197Au collisions at E/A = 1000 MeV

Heating of Nuclei with Energetic Antiprotons

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