Energy and angular momentum sharing in dissipative collisions

Primary and secondary masses of heavy reaction products have been deduced from kinematics and E-ToF measurements, respectively, for the direct and reverse collisions of 93Nb and 116Sn at 25 AMeV. Light charged particles have also been measured in coincidence with the heavy fragments. Direct experimental evidence of the correlation of energy-sharing with net mass transfer has been found using the information from both the heavy fragments and the light charged particles. The ratio of Hydrogen and Helium multiplicities points to a further correlation of angular momentum sharing with net mass transfer.Comment: 21 pages, 20 figures. Submitted to European Physics Journal

Particle and light fragment emission in peripheral heavy ion collisions at Fermi energies

A systematic investigation of the average multiplicities of light charged particles and intermediate mass fragments emitted in peripheral and semiperipheral collisions is presented as a function of the beam energy, violence of the collision and mass of the system. The data have been collected with the "Fiasco" setup in the reactions 93Nb+93Nb at 17, 23, 30, 38AMeV and 116Sn+116Sn at 30, 38AMeV. The midvelocity emission has been separated from the emission of the projectile-like fragment. This last component appears to be compatible with an evaporation from an equilibrated source at normal density, as described by the statistical code Gemini at the appropriate excitation energy. On the contrary, the midvelocity emission presents remarkable differences for what concerns both the dependence of the multiplicities on the energy deposited in the midvelocity region and the isotopic composition of the emitted light charged particles.Comment: 18 pages, 17 figures, Revtex

Utilidad de las respuestas rápidas de estrés para evaluar la evolución del tratamiento en un canino con fobia social

El miedo es un estado emocional aversi­vo ante una amenaza real o percibida como peligro externo. Esta emoción produce respuestas autonómicas que alteran la homeostasis del individuo. Cuando esta situación se prolonga en el tiempo, el estado de salud se afecta. El objetivo de este trabajo fue relacionar el reflejo pupilar y las frecuencia cardíaca y respiratoria con la producción de saliva, concentración de cortisol y respuestas conductuales, para evaluar la evolución del tratamiento con paroxetina (1 mg/kg cada 12 horas) y terapia conductual en una perra boxer con fobia social, en el primer mes post adopción. Ambas frecuencias se mantuvieron normales durante toda la experiencia (FC 76 a 98 lpm y FR 18 a 40 mrm). Sin embargo, en el día 1 la frecuencia cardíaca fue más alta que en los días 15 y 30 (p<0,05). Con respecto a la dilatación pupilar, en el día uno se observó midria­sis y a partir del día 15 el reflejo pupilar fue normal. Si bien la producción de saliva fue más abundante en el primer día que en los días 15 y 30 (p<0,05), las concentraciones de cortisol durante todo el periodo no arrojaron diferencias significativas, presentando el valor absoluto más alto el día 15 (1,22 μg/dl). Tanto las variables para los comportamientos de mantenimien­to como para los comportamientos sociales fueron significativamente diferentes a lo largo de la experiencia (p<0,001). Por otra parte, no se presentaron efectos adversos atribuibles a la paroxetina y la paciente recuperó el apetito, entrando en celo a los dos meses después. Los parámetros clínicos asociados al sistema nervioso autónomo resultan de interés práctico para evaluar la progresión del tratamiento del paciente canino con fobia

Linear electronics for Si-detectors and its energy calibration for use in heavy ion experiments

Abstract The design and implementation of linear electronics based on small-size, low-power charge preamplifiers and shaping amplifiers, used in connection with Si-detector telescopes employed in heavy ion experiments, are presented. Bench tests and "under beam" performances are discussed. In particular, the energy calibration and the linearity test of the overall system (Si-detector and linear and digital conversion electronics) has been performed with a procedure which avoids the pulse height defect problems connected with the detection of heavy ions. The procedure, basically, consists of using bursts of MeV protons, releasing up to GeV energies inside the detector, with low ionization density

Space and Time pattern of mid-velocity IMF emission in peripheral heavy-ion collisions at Fermi energies

The emission pattern in the V_perp - V_par plane of Intermediate Mass Fragments with Z=3-7 (IMF) has been studied in the collision 116Sn + 93Nb at 29.5 AMeV as a function of the Total Kinetic Energy Loss of the reaction. This pattern shows that for peripheral reactions most of IMF's are emitted at mid-velocity. Coulomb trajectory calculations demonstrate that these IMF's are produced in the early stages of the reaction and shed light on geometrical details of these emissions, suggesting that the IMF's originate both from the neck and the surface of the interacting nuclei.Comment: 4 pages, 3 figures, RevTex 3.1, submitted to Phys. Rev. Letter

Fiasco: a multidetector optimized for semiperipheral heavy ion collisions at Fermi energies

The Fiasco multidetector is a low-threshold apparatus, optimized for the investigation of peripheral to semi-central collisions in heavy ion reactions at Fermi energies. It consists of three types of detectors. The first detector layer is a shell of 24 position-sensitive Parallel Plate Avalanche Detectors (PPADs), covering about 70% of the forward hemisphere, which measure the velocity vectors of the heavy ðZ\10Þ reaction products. Below and around the grazing angle, behind the most forward PPADs, there are 96 DE–E silicon telescopes (with thickness of 200 and 500 mm; respectively); they are mainly used to measure the energy of the projectile-like fragment and to identify its charge and, via the time-of-flight of the PPADs, also its mass. Finally, behind most of the PPADs there are 158 (or 182, depending on the configuration) scintillation detectors, mostly of the phoswich type, which cover 25–30% of the forward hemisphere; they identify both light charged particles ðZ ¼ 1; 2Þ and intermediate mass fragments ð3pZt20Þ; measuring also their time-of-flight. r 2003 Elsevier B.V. All rights reserved

Angular momentum sharing in dissipative collisions

Light charged particles emitted by the projectile-like fragment were measured in the direct and reverse collision of $^{93}$Nb and $^{116}$Sn at 25 AMeV. The experimental multiplicities of Hydrogen and Helium particles as a function of the primary mass of the emitting fragment show evidence for a correlation with net mass transfer. The ratio of Hydrogen and Helium multiplicities points to a dependence of the angular momentum sharing on the net mass transfer.Comment: 8 pages, 2 figure

N and Z odd-even staggering in Kr + Sn collisions at Fermi energies

The odd-even staggering of the yield of final reaction products has been studied as a function of proton (Z) and neutron (N) numbers for the collisions 84 Kr+112 Sn and 84 Kr+124 Sn at 35 MeV/nucleon, in a wide range of elements (up to Z ~ 20). The experimental data show that staggering effects rapidly decrease with increasing size of the fragments. Moreover the staggering in N is definitely larger than the one in Z. Similar general features are qualitatively reproduced by the GEMINI code. Concerning the comparison of the two systems, the staggering in N is in general rather similar, being slightly larger only for the lightest fragments produced in the n-rich system. In contrast the staggering in Z, although smaller than that in N, is sizably larger for the n-poor system with respect to the n-rich one.Comment: 6 pages, 5 figures, Revtex forma