Heavy Ion Interactions Research Articles

Monte Carlo model for neutrino-nucleus interactions: past, present and future

Quantum Chromodynamics (QCD) is the correct theory of strong interactions. The main direction of investigations in physics of elementary particles and nuclear physics is testing of QCD. QCD predicts that at high energy density there will be a transformation from ordinary nuclear matter to a plasma of free quarks and gluons, the Quark-Gluon Plasma (QGP). In order to reach new knowledge of QCD from the interaction of relativistic heavy ions, one needs directly comparable data sets from systems of various sizes, different energies and different experimental probes. Lepton-nucleus scattering provides a nontrivial possibility to study space-time evolution of jets inside the nuclear matter. Using QCD-inspired time dependent cross sections for pre-hadrons we have introduced a space-time model for propagation and hadronization of quark and gluon jets in the nuclear matter in DIS. The aim of this work is to examine a multiproduction process of charged-current deep inelasticvμ-nucleus and nuclear emulsion scattering and estimate quantitatively the value of the formation time. These studies may help to explain the jet quenching in heavy ion collisions. In conclusion, the role of neutrino generators in modern neutrino experiments with nuclear targets will be discussed.

Influence of the tensor force on the microscopic heavy-ion interaction potential

Background: The tensor interaction is known to play an important role in the nuclear structure studies of exotic nuclei. However, most microscopic studies of low-energy nuclear reactions neglect the tensor force, resulting in a lack of knowledge concerning the effect of the tensor force on HIC...... Purpose: The theoretical study of the influence of the tensor force on heavy-ion interaction potentials is required to further our understanding of the microscopic mechanisms entailed in fusion dynamics. Method: The full Skyrme tensor force is implemented into the static Hartree-Fock and dynamic density-constrained time-dependent Hartree-Fock (DC-TDHF) theory to calculate both static (frozen density) and dynamic microscopic interaction potentials for reactions involving exotic and stable nuclei. Results: The static potentials are found to be systematically higher than the dynamical results, which are attributed to the microscopic dynamical effects included in TDHF. We also show that the dynamical potential barriers vary more significantly by the inclusion of tensor force than the static barriers. The influence of isoscalar and isovector tensor terms is also investigated with the TIJ set of forces. For light systems, the tensor force is found to have an imperceptible effect on the nucleus-nucleus potential. However, for medium and heavy spin-unsaturated reactions, the potentials may change from a fraction of an MeV to almost 2 MeV by the inclusion of tensor force, indicating a strong impact of the tensor force on sub-barrier fusion. Conclusions: The tensor force could indeed play a large role in the fusion of nuclei, with spin-unsaturated systems seeing a systematic increase in ion-ion barrier height and width. This fusion hindrance is partly due to static, ground state effects from the inclusion of the tensor force, though additional hindrance appears when studying nuclear dynamics.

Chaotic Multiparticle Production in Ring and Jet Structured Events in Heavy Ion Interaction: A Study in Multidimensional Phase Space

Two different classes of events exist in case of 16O–AgBr interactions at 60 AGeV, namely, ring-like and jet-like structured events. We have performed a rigorous study on the erratic behaviour of produced particles in ring-like and jet-like events in 16O–AgBr interactions at 60 AGeV with the help of entropy index μq. We have analysed the data in two dimensional phase space. The data reveal different pionisation for ring-like and jet-like events.

Exploring the shape of the γ-ray spectrum around the “π0-bump”

The “pion-decay” bump is a distinct signature of the differential energy spectrum of γ-rays between 100 MeV and 1 GeV produced in hadronic interactions of accelerated particles (cosmic rays) with the ambient gas. We use recent parametrisations of relevant cross-sections to study the formation of the “pion-decay” bump. The γ-ray spectrum below the maximum of this spectral feature can be distorted because of contributions of additional radiation components, in particular, due to the bremsstrahlung of secondary electrons and positrons, the products of decays of π±-mesons, accompanying the π0-production. At energies below 100 MeV, a non-negligible fraction of γ-ray flux could originate from interactions of sub-relativistic heavy ions. We study the impact of these radiation channels on the formation of the overall γ-ray spectrum based on a time-dependent treatment of evolution of energy distributions of the primary and secondary particles in the γ-ray production region.

Evidence of centrality dependent fractal behavior in high energy heavy ion interactions: Hint of two different sources

Studies on large density fluctuations in produced particle spectra in high energy interactions provide enough information regarding the dynamics of the process of particle production. Various analyses have revealed self-similarity in particle production process. The concept of self-similarity is indicative of fractal geometry. The present analysis reports an exhaustive study on centrality dependence of event-by-event fluctuation of pions produced in16O-AgBr interactions at 60 A GeV using a non conventional tool based on complex network analysis, viz. visibility graph method. The analysis reveals different fractal behaviour as well as different clustering property for different centrality events and the amount of fractality and average clustering coefficient decrease with the increase of centrality. Estimation of Hurst exponent hints towards two different sources of fluctuation, fractional Brownian motion (fBm) and fractional Gaussian noises (fGn) for two different centrality classes.

Dynamics of changes in structural properties of AlN ceramics after Xe+22 ion irradiation

Investigation of mechanisms of defect formation as a result of the interaction of heavy ions with ceramic materials and subsequent structural disturbances in the volume is considerably interesting for the prediction of ceramics behavior whose radiation resistance is determined by defects created during irradiation. Also, the energy losses arising from the interaction of incident particles with target atoms, as well as an increase in temperature upon irradiation, can have a significant effect on defects formation and their subsequent evolution in the structure. The paper presents the results of studying of defect formation processes in AlN ceramics under irradiation with Xe+22 ions with fluence from 5 × 1011 to 1.2 × 1014 ion/cm2. The change in the main crystallographic characteristics, as well as the decrease in the magnitude of the Griffiths criterion and the stresses in the lattice, indicates the processes of defect formation and their subsequent evolution in the structure.

Anti-aggregation of gold nanoparticles for metal ion discrimination: A promising strategy to design colorimetric sensor arrays

The first report of anti-aggregation-based sensor arrays is presented. The strategy is based on the competitive interaction of citrate-capped gold nanoparticles (AuNPs) and heavy metal ions (i.e., Hg(II), Ag(I), Fe(III), and Pb(II)) with three aggregation reagents (i.e., cysteine, melamine, and arginine). In the presence of aggregation reagent, the color and UV–vis spectra of AuNPs are changed indicating the aggregation of AuNPs. Addition of the aggregation reagents which are firstly treated with the ions, causes AuNPs turn from the aggregation to the dispersion state. The anti-aggregation capability of ions towards various aggregation reagents is different because of distinct stability constants of ion-aggregation reagent complexes. The combinatorial colorimetric response of all sensor elements enables discrimination among the ions in various concentrations, as well as mixtures of them by linear discriminant analysis (LDA). Moreover, heavy metal ions are well-distinguished in river and fish samples with an accuracy of 100%.

Integrated Simulation of Fragmentation, Evaporation, and Gamma-decay Processes in the Interaction of Cosmic-ray Heavy Ions with the Atmosphere using PHITS

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Development of Continuum-Atomistic Approach for Modeling Metal Irradiation by Heavy Ions

Over the last several decades active research in the field of materials irradiation by high-energy heavy ions has been worked out. The experiments in this area are labor-consuming and expensive. Therefore the improvement of the existing mathematical models and the development of new ones based on the experimental data of interaction of high-energy heavy ions with materials are of interest. Presently, two approaches are used for studying these processes: a thermal spike model and molecular dynamics methods. The combination of these two approaches – the continuous-atomistic model – will give the opportunity to investigate more thoroughly the processes of irradiation of materials by high-energy heavy ions. To solve the equations of the continuous-atomistic model, a software package was developed and the block of molecular dynamics software was tested on the heterogeneous cluster HybriLIT.

Radial Flow in a Multiphase Transport Model at FAIR Energies

Azimuthal distributions of radial velocities of charged hadrons produced in nucleus-nucleus (AB) collisions are compared with the corresponding azimuthal distribution of charged hadron multiplicity in the framework of a multiphase transport (AMPT) model at two different collision energies. The mean radial velocity seems to be a good probe for studying radial expansion. While the anisotropic parts of the distributions indicate a kind of collective nature in the radial expansion of the intermediate “fireball,” their isotropic parts characterize a thermal motion. The present investigation is carried out keeping the upcoming Compressed Baryonic Matter (CBM) experiment to be held at the Facility for Antiproton and Ion Research (FAIR) in mind. As far as high-energy heavy-ion interactions are concerned, CBM will supplement the Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) experiments. In this context our simulation results at high baryochemical potential would be interesting, when scrutinized from the perspective of an almost baryon-free environment achieved at RHIC and LHC.

2nd-order optical model of the isotopic dependence of heavy ion absorption cross sections for radiation transport studies

Abstract Heavy ion absorption cross sections play an important role in radiation transport codes used in risk assessment and for shielding studies of galactic cosmic ray (GCR) exposures. Due to the GCR primary nuclei composition and nuclear fragmentation leading to secondary nuclei heavy ions of charge number, Z with 3 ≤ Z ≥ 28 and mass numbers, A with 6 ≤ A ≥ 60 representing about 190 isotopes occur in GCR transport calculations. In this report we describe methods for developing a data-base of isotopic dependent heavy ion absorption cross sections for interactions. Calculations of a 2nd-order optical model solution to coupled-channel solutions to the Eikonal form of the nucleus-nucleus scattering amplitude are compared to 1st-order optical model solutions. The 2nd-order model takes into account two-body correlations in the projectile and target ground-states, which are ignored in the 1st-order optical model. Parameter free predictions are described using one-body and two-body ground state form factors for the isotopes considered and the free nucleon-nucleon scattering amplitude. Root mean square (RMS) matter radii for protons and neutrons are taken from electron and muon scattering data and nuclear structure models. We report on extensive comparisons to experimental data for energy-dependent absorption cross sections for over 100 isotopes of elements from Li to Fe interacting with carbon and aluminum targets. Agreement between model and experiments are generally within 10% for the 1st-order optical model and improved to less than 5% in the 2nd-order optical model in the majority of comparisons. Overall the 2nd-order optical model leads to a reduction in absorption compared to the 1st-order optical model for heavy ion interactions, which influences estimates of nuclear matter radii.

Abstract ID: 61 Validation of Geant4 nuclear reaction models for hadrontherapy and preliminary results with SMF and Blob

Reliable nuclear fragmentation models are of utmost importance in hadrontherapy, where Monte Carlo (MC) simulations are used to compute the input parameters of the treatment planning software, to validate the deposited dose calculation, to evaluate the biological effectiveness of the radiation, to correlate the β + emitters production in the patient body with the delivered dose, and to allow a non-invasive treatment verification. Despite of its large use, the models implemented in Geant4 have shown severe limitations in reproducing the measured secondaries yields in ions interaction below 100 MeV/A, in term of production rates, angular and energy distributions [1] , [2] , [3] . We will present a benchmark of the Geant4 models with double-differential cross section and angular distributions of the secondary fragments produced in the 12C fragmentation at 62 MeV/A on thin carbon target, such a benchmark includes the recently implemented model INCL++ [4] , [5] . Moreover, we will present the preliminary results, obtained in simulating the same interaction, with SMF [6] and BLOB [7] . Both, SMF and BLOB are semiclassical one-body approaches to solve the Boltzmann-Langevin equation. They include an identical treatment of the mean-field propagation, on the basis of the same effective interaction, but they differ in the way fluctuations are included. In particular, while SMF employs a Uehling-Uhlenbeck collision term and introduces fluctuations as projected on the density space, BLOB introduces fluctuations in full phase space through a modified collision term where nucleon-nucleon correlations are explicitly involved. Both of them, SMF and BLOB, have been developed to simulate the heavy ion interactions in the Fermi-energy regime. We will show their capabilities in describing 12C fragmentation foreseen their implementation in Geant4.

Heavy flavour production in proton–lead and lead–lead collisions with LHCb

The LHCb experiment offers the unique opportunity to study heavy-ion interactions in the forward region (2<η<5), in a kinematic domain complementary to the other 3 large experiments at the LHC. The detector has excellent capabilities for reconstructing quarkonia and open charm states, including baryons, down to zero pT. It can separate the prompt and displaced charm components. In pPb collisions, both forward and backward rapidities are covered thanks to the possibility of beam reversal. Results include measurements of the nuclear modification factor and forward-backward ratio for charmonium, open charm and bottomonium states. These quantities are sensitive probes for nuclear effects in heavy flavour production. Perspectives are given with the large accumulated luminosity during the 2016 pPb run at the LHC. In 2015, LHCb participated successfully for the first time in the PbPb data-taking. The status of the forward prompt J/ψ nuclear modification factor measurement in lead-lead collisions is discussed.

Simultaneous removal of cadmium, zinc and manganese using electrocoagulation: Influence of operating parameters and electrolyte nature

In the present study, the influence of operating parameters and electrolyte nature on the simultaneous removal of toxic metals (cadmium, zinc and manganese) from synthetic smelting wastewater by batch electrocoagulation was investigated. This wastewater contained high concentrations of anion–cation electrolytes. Results indicated that the efficiency of heavy metals removal can be enhanced by increasing the solution pH and current density. The Fe–Fe electrode combination is more effective than the other combinations (Al–Al, Al–Fe and Fe–Al). The interaction of heavy metal ions showed that the increase of initial Zn2+ concentration adversely affects on Cd2+ removal. In addition, the single chloride system exhibits the optimum removal efficiency on Mn2+. Single sulfate and binary anion systems exert a more positive effect on Cd2+ and Zn2+ removal because of the stronger charge neutralization and destabilization of iron hydroxide flocs. Increases of Ca2+ and Mg2+ ions exert a significant negative effect on metal removal. However, the addition of a small amount of sodium chloride into a high sulfate and hardness solution can accelerate the removal of heavy metals. Finally, the sludge samples generated from electrocoagulation were characterized by XRD and SEM–EDS analyses.

D0 meson production in pPb and PbPb collisions at [formula omitted] with LHCb

The LHCb experiment has the unique property to study open heavy flavors in heavy ion interactions in the forward and backward hemisphere, thanks to its forward acceptance 2<η<5, and the possibility to study proton-lead collisions for both orientations of the beams. In 2015, LHCb also participated successfully for the first time in the lead-lead data-taking. First studies showed that up to semi-central PbPb collisions can be analysed. Furthermore, using the possibility to inject gas into the interaction region, it is in the unique position to do fixed target physics. Results including measurement of the forward-backward production of prompt D0 in pPb collisions at sNN=5 TeV are presented. Prospects for D0 production measurement in PbPb and fixed-target collisions are also presented.

Rapidity distributions of hadrons in the HydHSD hybrid model

A multistage hybrid model intended for describing heavy-ion interactions in the energy region of the NICA collider under construction in Dubna is proposed. The model combines the initial, fast, interaction stage described by the model of hadron string dynamics (HSD) and the subsequent evolution that the expanding system formed at the first stage experiences at the second stage and which one treats on the basis of ideal hydrodynamics; after the completion of the second stage, the particles involved may still undergo rescattering (third interaction stage). The model admits three freeze-out scenarios: isochronous, isothermal, and isoenergetic. Generally, the HydHSD hybrid model developed in the present study provides fairly good agreement with available experimental data on proton rapidity spectra. It is shown that, within this hybrid model, the two-humped structure of proton rapidity distributions can be obtained either by increasing the freeze-out temperature and energy density or by more lately going over to the hydrodynamic stage. Although the proposed hybrid model reproduces rapidity spectra of protons, it is unable to describe rapidity distributions of pions, systematically underestimating their yield. It is necessary to refine the model by including viscosity effects at the hydrodynamic stage of evolution of the system and by considering in more detail the third interaction stage.

Pre-compound emission in low-energy heavy-ion interactions

Recent experimental studies have shown the presence of pre-compound emission component in heavy ion reactions at low projectile energy ranging from 4 to 7 MeV/nucleons. In earlier measurements strength of the pre-compound component has been estimated from the difference in forward-backward distributions of emitted particles. Present measurement is a part of an ongoing program on the study of reaction dynamics of heavy ion interactions at low energies aimed at investigating the effect of momentum transfer in compound, precompound, complete and incomplete fusion processes in heavy ion reactions. In the present work on the basis of momentum transfer the measurement of the recoil range distributions of heavy residues has been used to decipher the components of compound and pre-compound emission processes in the fusion of 16 O projectile with 159 Tb and 169 Tm targets. The analysis of recoil range distribution measurements show two distinct linear momentum transfer components corresponding to pre-compound and compound nucleus processes are involved. In order to obtain the mean input angular momentum associated with compound and pre-compound emission processes, an online measurement of the spin distributions of the residues has been performed. The analysis of spin distribution indicate that the mean input angular momentum associated with pre-compound products is found to be relatively lower than that associated with compound nucleus process. The pre-compound components obtained from the present analysis are consistent with those obtained from the analysis of excitation functions.

Secondary light-ion transport from intermediate-energy hadron experiments

The aim of this research is to produce double differential thick target yields, angular distributions and integrated yields for the inclusive production of neutrons, protons, deuterons, tritons, 3 He, and 4 He from intermediate heavy-ion interactions on thick targets of aluminium, polyethylene and other targets of interest to the radiation shielding program as specified by the National Aeronautics and Space Administration (NASA). In tandem with the experimental research, transport model calculations of these thick target yields were also performed. The first such experimental run was conducted in May 2015, with the expectation of improved experimental results at a following March 2016 run at the NASA Space Radiation Laboratory (NSRL) on the campus of Brookhaven National Laboratory (BNL). The May 2015 commissioning run served to test the electronics of the experimental setup, as well as the various detectors and other equipment under the conditions in which the following measurements will be run. The series of future accelerator-based experiments will rely on the inclusion of two separate upstream and downstream targets. Analysis of the data from both sets of detectors – liquid scintillator and sodium iodide – using both pulse height and time-of-flight methods will allow NASA to perform uncertainty quantification and sensitivity analysis on their transport codes and future shielding studies.

Precompound emission in low-energy heavy-ion interactions from recoil range and spin distributions of heavy residues: A new experimental method

Recent investigations of heavy-ion reactions at low incident energies have indicated the presence of precompound emission component in considerable strength. In most cases the strength of the precompound component is estimated from the difference in forward-backward distributions of emitted light fast particles and also from the analysis of the measured excitation functions. This paper reports a new method of deciphering the relative contributions of compound and precompound components associated with fusion of $^{16}\mathrm{O}$ with $^{159}\mathrm{Tb},^{169}\mathrm{Tm}$, and $^{181}\mathrm{Ta}$ targets by measuring the recoil ranges of heavy residues in an absorbing medium along with the online measurement of the spin distributions in reaction residues produced in the fusion $^{16}\mathrm{O}$ beam with $^{159}\mathrm{Tb}$ and $^{169}\mathrm{Tm}$ targets. Analysis of recoil range and spin distributions of the residues shows two distinct linear momentum-transfer components corresponding to precompound and compound nucleus processes. The input angular momentum associated with precompound products is found to be relatively lower than that associated with compound nucleus process. The precompound components obtained from the present analysis are consistent with those obtained from the analysis of excitation functions.

Monte Carlo studies of the interaction of relativistic ions with nuclear emulsion

Interaction of high energy heavy ions with nuclear emulsion simulated using MCNPX 2.7 and its associated Monte Carlo codes. The simulations were performed for interactions of 4.1 AGeV/c 22Ne ions with nuclear emulsion event by event via batch files written for this purpose. It is shown that MCNPX correctly simulates the spallation as well as “complete destruction” interactions using the same physics principles and models. Cross-sections for interaction of 4.1 AGeV/c 22Ne ions with emulsion, Ag and Br in emulsion and rest of the nuclei in the emulsion were determined. Good agreements between calculations and experimental results were obtained.