Measurement of the complete nuclide production and kinetic energies of the system<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">Xe</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>136</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>+hydrogen at 1 GeV per nucleon

Napolitani, P.; Schmidt, K.‐H.; Tassan‐Got, L.; Armbruster, P.; Enqvist, T.; Heinz, A.; Henzl, V.; Henzlová, D.; Kelić, A.; Pleskač, R.; Ricciardi, M. V.; Schmitt, C.; Yordanov, O.; Audouin, L.; Bernas, M.; Lafriaskh, A.; Rejmund, F.; Stéphan, C.; Benlliure, J.; Casarejos, E.; Ordonez, M. F.; Pereira, J.; Boudard, A.; Fernández, Beatriz; Leray, S.; Villagrasa, C.; Volant, C.

doi:10.1103/physrevc.76.064609

Cited by 83 publications

(75 citation statements)

References 54 publications

(65 reference statements)

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“…In the parametrization by Wahl, the smooth behavior is represented by the geometric mean between odd and even yield values. Odd-even effects were discovered also in light complex fragments produced in high-energy fragmentation and spallation reactions [15,16,17,18,19,20,21]. The staggering consisted again in an intensification of the yields of even charges Z with respect to odd ones, although the reaction mechanism, the shape of the charge distributions and the investigated mass region were obviously different from those of low-energy fission experiments.…”

Section: Introductionmentioning

confidence: 96%

Methods for a quantitative evaluation of odd-even staggering effects

Olmi¹,

Piantelli²

2015

Eur. Phys. J. A

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Abstract. Odd-even effects, also known as staggering effects, are a common feature observed in the yield distributions of fragments produced in different types of nuclear reactions. We review old methods, and we propose new ones, for a quantitative estimation of these effects as a function of proton or neutron number of the reaction products. All methods are compared on the basis of Monte Carlo simulations. We find that some are not well suited for the task, the most reliable ones being those based either on a non-linear fit with a properly oscillating function or on a third (or fourth) finite difference approach. In any case, high statistic is of paramount importance to avoid that spurious structures appear just because of statistical fluctuations in the data and of strong correlations among the yields of neighboring fragments.

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Section: Introductionmentioning

confidence: 96%

Methods for a quantitative evaluation of odd-even staggering effects

Olmi¹,

Piantelli²

2015

Eur. Phys. J. A

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“…The first experimental approach we focus on is a campaign of inverse-kinematics experiments, performed at GSI (Darmstadt): the FRagment Separator [35] (FRS), a high-resolution magnetic achromat [36], was employed to measure the nuclide production in several spallation reactions at around 1AGeV [33,[37][38][39][40][41][42][43][44][45][46][47][48][49][50]. In some systems it was possible to measure the isotopic cross sections of the IMF and the corresponding zero-angle invariant-velocity distributions; these distributions are constructed by selecting only the velocity vectors aligned along the beam direction (they are evidently different from longitudinal projections of the whole velocity distributions).…”

Section: A Experimental Observables: An Examplementioning

confidence: 99%

“…1 presents some of those experimental results taken from ref. [49], and resumes few essential steps of the data analysis [51].…”

Section: A Experimental Observables: An Examplementioning

confidence: 99%

Frustrated fragmentation and re-aggregation in nuclei: A non-equilibrium description in spallation

Napolitani

Colonna

2015

Phys. Rev. C

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Heavy nuclei bombarded with protons and deuterons in the 1 GeV range have a large probability of undergoing a process of evaporation and fission; less frequently, the prompt emission of few intermediate-mass fragments can also be observed.We employ a recently developed microscopic approach, based on the Boltzmann-Langevin transport equation, to investigate the role of mean-field dynamics and phase-space fluctuations in these reactions.We find that the formation of few IMF's can be confused with asymmetric fission when relying on yield observables, but it can not be assimilated to the statistical decay of a compound nucleus when analysing the dynamics and kinematic observables: it can be described as a fragmentation process initiated by phase-space fluctuations, and successively frustrated by the mean-field resilience. As an extreme situation, which corresponds to non-negligible probability, the number of fragments in the exit channel reduces to two, so that fission-like events are obtained by re-aggregation processes.This interpretation, inspired by nuclear-spallation experiments, can be generalised to heavy-ion collisions from Fermi to relativistic energies, for situations when the system is closely approaching the fragmentation threshold. I. CONTEXTSeveral decades passed from Serber's early description [1] of nuclear reactions induced by nucleons and light nuclei at few hundred MeV per nucleon. In their standard outline, such reactions, generally called spallation, could be described as a fast excitation of an atomic nucleus, followed by a slower decay process [2,3]: depending on the phase space available [4,5], the system undergoes a sequence of more or less asymmetric splits [6, 7] ranging from particle evaporation to fission. It was found already in pioneering studies [8][9][10][11][12][13][14][15][16][17], that the most excited systems can also produce intermediate-mass fragments (IMF), and lead to a richer phenomenology comparable with nucleus-nucleus collisions and nuclear fragmentation [18][19][20][21]. Further research focused on the study of thermodynamic observables from spallation reactions in the relativistic domain [22][23][24][25], in connection with the liquid-gas phase transition in nuclear matter [26,27], and in parallel with the research on the multifragmentation process observed in ion-ion collisions in the Fermi-energy domain [28][29][30][31][32].Several fields of application, from energy and environment to neutron sources and exotic beams, stimulated intense research on protons and deuterons in the 1 GeV range impinging on heavy nuclei. The production of some specific light nuclides with large kinetic energy resulted of great relevance in several technical issues (radiation damages, fragilisation of structural materials in acceleratordriven systems, side effects in medical hadron-therapies). This despite the minor contribution of the whole IMF production to the total reaction cross section, which was found to amount to few millibarn. In more recent experiments, the possibility of correlati...

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“…Moreover, there is some controversy over IMF production cross sections from 1-GeV p+ 136 Xe system; the two existing measurements [26,27] disagree of about a factor of 3 for 10 Z 30. This situation prevents us from providing a unique, predictive Charge number…”

Section: Spallation Reactionsmentioning

confidence: 99%

“…Experimental [26,27] and calculated residual charge distributions for 1-GeV p+ 136 Xe. The two symbols for Gorbinet et al 's data correspond to different techniques (see text for more details).…”

Section: Spallation Reactionsmentioning

confidence: 99%

Simultaneous fitting of statistical-model parameters to symmetric and asymmetric fission cross sections

Mancusi

Charity

2013

J. Phys.: Conf. Ser.

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Abstract. The de-excitation of compound nuclei has been successfully described for several decades by means of statistical models. However, accurate predictions require some fine-tuning of the model parameters. This task can be simplified by studying several entrance channels, which populate different regions of the parameter space of the compound nucleus.Fusion reactions play an important role in this strategy because they minimise the uncertainty on the entrance channel by fixing mass, charge and excitation energy of the compound nucleus. If incomplete fusion is negligible, the only uncertainty on the compound nucleus comes from the spin distribution. However, some de-excitation channels, such as fission, are quite sensitive to spin. Other entrance channels can then be used to discriminate between equivalent parameter sets.The focus of this work is on fission and intermediate-mass-fragment emission cross sections of compound nuclei with 70 A 240. The statistical de-excitation model is GEMINI++. The choice of the observables is natural in the framework of GEMINI++, which describes fragment emission using a fissionlike formalism. Equivalent parameter sets for fusion reactions can be resolved using the spallation entrance channel. This promising strategy can lead to the identification of a minimal set of physical ingredients necessary for a unified quantitative description of nuclear de-excitation. IntroductionThe de-excitation of an excited nucleus is a qualitatively well-understood phenomenon which is often described by means of statistical models. However, such models contain a great deal of free parameters and ingredients that are often underconstrained by the available experimental data. Quantitatively accurate predictions usually require some tuning of the model parameters.The fusion entrance channel is a particularly powerful tool to explore the sensitivity of the deexcitation model to the compound-nucleus parameters (mass, charge, excitation energy and spin); if the cross sections for incomplete fusion and pre-equilibrium emission are negligible with respect to the fusion cross section for a given projectile-target combination, the compound nucleus can essentially be regarded as having a fixed mass, charge and total excitation energy (intrinsic plus collective), thereby fixing three of the four parameters that describe it. The requirement of complete fusion, however, puts an upper limit on the energy of the projectile and, thus, on the excitation energies that can be studied with this method. Because of this and other similar limitations on the entrance channel, one is actually able to construct different parameter sets that can describe the same experimental data to a similar degree of accuracy; in this sense, statistical de-excitation models contain partly degenerate ingredients, and that limits their predictive power.

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Measurement of the complete nuclide production and kinetic energies of the systemXe136+hydrogen at 1 GeV per nucleon

Cited by 83 publications

References 54 publications

Methods for a quantitative evaluation of odd-even staggering effects

Methods for a quantitative evaluation of odd-even staggering effects

Frustrated fragmentation and re-aggregation in nuclei: A non-equilibrium description in spallation

Simultaneous fitting of statistical-model parameters to symmetric and asymmetric fission cross sections

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