Probing the Concept of Statistical Independence of Intermediate-Mass Fragment Production in Heavy-Ion Collisions

It is found that the total IMF-transverse-energy (E_t) spectra in multi-IMF events are well represented by synthetic spectra obtained by folding of the single-IMF spectrum. Using the experimental IMF multiplicity distribution, the observed trends in the IMF multiplicity distribution for fixed values of E_t are reproduced. The synthetic distributions show binomial reducibility and Arrhenius-like scaling, similar to that reported in the literature. Similar results are obtained when the above folding-type synthesis is replaced with one based on mixing events with different IMF multiplicities. For statistically independent IMF emission, the observed binomial reducibility and Arrhenius-type scaling are merely reflections of the shape of the single-IMF transverse-energy spectrum. Hence, a valid interpretation of IMF distributions in terms of a particular production scenario has to explain independently the observed shape of the single-IMF E_t spectrum.Comment: 13 pages with 8 figur

An experimental survey of the production of alpha decaying heavy elements in the reactions of 238^{238}U +232^{232}Th at 7.5-6.1 MeV/nucleon

The production of alpha particle decaying heavy nuclei in reactions of 7.5-6.1 MeV/nucleon $^{238}$U +$^{232}$Th has been explored using an in-beam detection array composed of YAP scintillators and gas ionization chamber-Si telescopes. Comparisons of alpha energies and half-lives for the observed products with those of the previously known isotopes and with theoretically predicted values indicate the observation of a number of previously unreported alpha emitters. Alpha particle decay energies reaching as high as 12 MeV are observed. Many of these are expected to be from decay of previously unseen relatively neutron rich products. While the contributions of isomeric states require further exploration and specific isotope identifications need to be made, the production of heavy isotopes with quite high atomic numbers is suggested by the data.Comment: 12 pages, 12 figure

Dissipative orbiting in ^{136}Xe+^{209}Bi reactions at 28 and 62 AMeV

Correlations between the energy, charge and the deflection angle of the projectile-like fragments were studied for the ^{136}Xe + ^{209}Bi reaction at E∕A = 28 and 62 MeV. These correlations are seen to exhibit features characteristic of dissipative orbiting, commonly found at bombarding energies of a few MeV/nucleon above the interaction barrier, but also reported in the Fermi-energy domain. It was found, that in the studied bombarding energy range, the reaction cross section is still dominated by the dissipative binary reactions of well defined projectile- and target-like fragments

Elements Discrimination in the Study of Super-Heavy Elements using an Ionization Chamber

Dedicated ionization chamber was built and installed to measure the energy loss of very heavy nuclei at 2.7 MeV/u produced in fusion reactions in inverse kinematics (beam of 208Pb). After going through the ionization chamber, products of reactions on 12C, 18O targets are implanted in a Si detector. Their identification through their alpha decay chain is ambiguous when their half-life is short. After calibration with Pb and Th nuclei, the ionization chamber signal allowed us to resolve these ambiguities. In the search for rare super-heavy nuclei produced in fusion reactions in inverse or symmetric kinematics, such a chamber will provide direct information on the nuclear charge of each implanted nucleus.Comment: submitted to NIMA, 10 pages+4 figures, Latex, uses elsart.cls and grahpic

Isotopic Dependence of the Nuclear Caloric Curve

The A/Z dependence of projectile fragmentation at relativistic energies has been studied with the ALADIN forward spectrometer at SIS. A stable beam of 124Sn and radioactive beams of 124La and 107Sn at 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. Chemical freeze-out temperatures are found to be nearly invariant with respect to the A/Z of the produced spectator sources, consistent with predictions for expanded systems. Small Coulomb effects (\Delta T \approx 0.6 MeV) appear for residue production near the onset of multifragmentation.Comment: 11 pages, 3 figures, accepted for publ. in Phys. Rev. Let

Tracing a phase transition with fluctuations of the largest fragment size: Statistical multifragmentation models and the ALADIN S254 data

A phase transition signature associated with cumulants of the largest fragment size distribution has been identified in statistical multifragmentation models and examined in analysis of the ALADIN S254 data on fragmentation of neutron-poor and neutron-rich projectiles. Characteristics of the transition point indicated by this signature are weakly dependent on the A/Z ratio of the fragmenting spectator source. In particular, chemical freeze-out temperatures are estimated within the range 5.9 to 6.5 MeV. The experimental results are well reproduced by the SMM model.Comment: 7 pages, 3 figures, Proceedings of the International Workshop on Multifragmentation and Related Topics (IWM2009), Catania, Italy, November 2009

KRATTA, a triple telescope array for charged reaction products

KRATTA, a new, low threshold, broad energy range triple telescope array has been built to measure the energy, emission angles and isotopic composition of light charged reaction products. It has been equipped with fully digital chains of electronics. The array performed very well during the ASY-EOS experiment, conducted in May 2011 at GSI. The structure and performance of the array are presented using the first experimental results