Event generator to construct cross sections for the multiphonon excitation of a set of collective vibrational modes

The construction of differential cross sections as a function of excitation energy for systems with a collection of low- and high-lying intrinsic vibrational modes has been attempted in the past. A prescription is proposed that simplifies the implementation of such calculation schemes with a remarkable reduction in computational time.Comment: 6 pages, 3 figures, to be published in Phys. Rev.

Transfer reactions in the sudden limit of the pairing-rotor model

The transfer of multiple pairs of particles in heavy-ion reactions is studied in the sudden limit of the macroscopic pairing-rotor model

Study of Giant Pairing Vibrations with neutron-rich nuclei

We investigate the possible signature of the presence of giant pairing states at excitation energy of about 10 MeV via two-particle transfer reactions induced by neutron-rich weakly-bound projectiles. Performing particle-particle RPA calculations on $^{208}$Pb and BCS+RPA calculations on $^{116}$Sn, we obtain the pairing strength distribution for two particles addition and removal modes. Estimates of two-particle transfer cross sections can be obtained in the framework of the 'macroscopic model'. The weak-binding nature of the projectile kinematically favours transitions to high-lying states. In the case of (~^6He, \~^4He) reaction we predict a population of the Giant Pairing Vibration with cross sections of the order of a millibarn, dominating over the mismatched transition to the ground state.Comment: Talk presented in occasion of the VII School-Semina r on Heavy Ion Physics hosted by the Flerov Laboratory (FLNR/JINR) Dubna, Russia from May 27 to June 2, 200

On nucleon exchange mechanism in heavy-ion collisions at near-barrier energies

Nucleon drift and diffusion mechanisms in central collisions of asymmetric heavy-ions at near-barrier energies are investigated in the framework of a stochastic mean-field approach. Expressions for diffusion and drift coefficients for nucleon transfer deduced from the stochastic mean-field approach in the semiclassical approximation have similar forms familiar from the phenomenological nucleon exchange model. The variance of fragment mass distribution agrees with the empirical formula $\sigma^2_{AA}(t)= N_{\rm exc}(t)$. The comparison with the time-dependent Hartree-Fock calculations shows that, below barrier energies, the drift coefficient in the semiclassical approximation underestimates the mean number of nucleon transfer obtained in the quantal framework. Motion of the window in the dinuclear system has a significant effect on the nucleon transfer in asymmetric collisions.Comment: 10 pages, 10 figures, submitted for publicatio

Cliente muerto no paga

Desde el punto de vista económico, el confinamiento es, sin dudas, la clave que impide a la economía funcionar normalmente. Lo que no pudo la amenaza nuclear, aquello en lo que fracasaron sistemas totalitarios del control social ultraplanificado, la opresión política, racial y religiosa, lo ha conseguido la interrupción del comercio. Comercio y cooperación, como se verá, han sido vitales en la recuperación de la paz. En días como estos, deudores y acreedores son la misma cosa, y la interrupción del flujo económico implica que nadie puede pagar porque nadie puede trabajar y porque a su vez nadie puede cobrar. Mantener la economía pequeña de los pequeños emprendimientos, de la vida familiar, del pequeño comercio, es darle la primera base de sustentación a todo el sistema. Como solían enseñar Schuman y Monet, padres de la idea a la Gran Europa, el mejor preventivo de la guerra es evitar la escasez. Donde ha escasez hay que buscar poner abundancia, no a través del conflicto, sino de la cooperación, aún cuando haya que sacrificar algo en pos del todo.From an economic point of view, confinement is undoubtedly the key that prevents the economy from functioning normally. What the nuclear threat failed, what totalitarian systems of ultraplanned social control failed, political, racial and religious oppression, has been achieved by the interruption of trade. Trade and cooperation, as will be seen, have been vital in the recovery of peace. On days like these, debtors and creditors are the same thing, and the interruption of the economic flow implies that nobody can pay because nobody can work and because in turn nobody can collect. Keeping the economy small for small businesses, family life, small businesses, is to give the first base of support to the entire system. As Schuman and Monet, fathers of the idea, used to teach Greater Europe, the best preventative of war is to avoid scarcity. Where there is scarcity, one must seek to put abundance, not through conflict, but through cooperation, even when something has to be sacrificed in pursuit of the whole.publishedVersionFil: Dasso, Ariel G. Universidad Nacional de Córdoba. Facultad de Derecho; Argentina

Simple estimates of excitation energy sharing between heavy and light fragments in heavy-ion reactions

Qualitative arguments are used to estiamte the ratio of excitation energies between heavy and light fragments for asymmetric heavy-ion collisions. The value of this quantity is linked to the relative role played by inelastic and transfer degrees of freedom and thereby to an approximate function of the total kinetic energy loss. A numerical analysis that confirms the trends anticipated by the simple arguments is performed for the reactions 56Fe+ 238U and 86Kr+ 208Pb at bombarding energies in the laboratory of 476 and 1565 MeV, respectivelyComisión Asesora de Investigación Científica y Técnica 2868-8

Progressive transformation of a flux rope to an ICME

The solar wind conditions at one astronomical unit (AU) can be strongly disturbed by the interplanetary coronal mass ejections (ICMEs). A subset, called magnetic clouds (MCs), is formed by twisted flux ropes that transport an important amount of magnetic flux and helicity which is released in CMEs. At 1 AU from the Sun, the magnetic structure of MCs is generally modeled neglecting their expansion during the spacecraft crossing. However, in some cases, MCs present a significant expansion. We present here an analysis of the huge and significantly expanding MC observed by the Wind spacecraft during 9 and 10 November, 2004. After determining an approximated orientation for the flux rope using the minimum variance method, we precise the orientation of the cloud axis relating its front and rear magnetic discontinuities using a direct method. This method takes into account the conservation of the azimuthal magnetic flux between the in- and out-bound branches, and is valid for a finite impact parameter (i.e., not necessarily a small distance between the spacecraft trajectory and the cloud axis). Moreover, using the direct method, we find that the ICME is formed by a flux rope (MC) followed by an extended coherent magnetic region. These observations are interpreted considering the existence of a previous larger flux rope, which partially reconnected with its environment in the front. These findings imply that the ejected flux rope is progressively peeled by reconnection and transformed to the observed ICME (with a remnant flux rope in the front part).Comment: Solar Physics (in press