Production Of Light Fragments Research Articles

Production of High-Transverse-Momentum Deuterons and Tritons at an Angle of 40{{}^{circ}} in Proton–Nucleus Interactions at a Beam Energy of 50 GeV

Data on the production of positively charged particles emitted at an angle of 40{}^{circ} (in the laboratory frame) with transverse momenta of up to 2.7 GeV/c in the interaction of 50-GeV/c protons with carbon, aluminum, copper, and tungsten nuclear targets are presented. Particular attention is given to studying the production of light nuclear fragments, such as deuterons (d) and tritons (t). An analysis of data on d and t particles gives grounds to state that these fragments arise via a local mechanism of their direct knockout from nuclei. The results were obtained in the SPIN experiment at the Institute for High Energy Physics (IHEP, Protvino).

Monte-Carlo Generator of Heavy Ion Collisions DCM-SMM

The new monte-carlo generator of heavy ion collisions, DCM-SMM, based on Dubna Cascade Model (DCM-QGSM) and Statistical Multifragmentation Model (SMM) is described. The model aimed to generate particle--nucleus and nucleus--nucleus collisions at a wide range of energy was created to provide the computer simulation support to new experimental facilities BMN and MPD at the accelerator complex NICA. It can simulate the production of both light particles and nuclear fragments and hyperfragments on the event by event basis.

Light fragment production at CERN Super Proton Synchrotron

Recent data on the deutron and $^3$He production in central Pb+Pb collisions at the CERN Super Proton Synchrotron (SPS) energies measured by the NA49 collaboration are analyzed within the model of the three-fluid dynamics (3FD) complemented by the coalescence model for the light-fragment production. The simulations are performed with different equations of state---with and without deconfinement transition. It is found that scenarios with the deconfinement transition are preferable for reproduction rapidity distributions of deuterons and $^3$He, the corresponding results well agree with the experimental data. At the same time the calculated transverse-mass spectra of $^3$He at midrapidity do not that nice agree with the experimental data. The latter apparently indicates that coalescence coefficients should be temperature and/or momentum dependent.

Production of energetic light fragments in extensions of the CEM and LAQGSM event generators of the Monte Carlo transport code MCNP6

We extend the cascade-exciton model (CEM), and the Los Alamos version of the quark-gluon string model (LAQGSM), event generators of the Monte-Carlo N-particle transport code version 6 (MCNP6), to describe production of energetic light fragments (LF) heavier than 4He from various nuclear reactions induced by particles and nuclei at energies up to about 1 TeV/nucleon. In these models, energetic LF can be produced via Fermi break-up, preequilibrium emission, and coalescence of cascade particles. Initially, we study several variations of the Fermi break-up model and choose the best option for these models. Then, we extend the modified exciton model (MEM) used by these codes to account for a possibility of multiple emission of up to 66 types of particles and LF (up to 28Mg) at the preequilibrium stage of reactions. Then, we expand the coalescence model to allow coalescence of LF from nucleons emitted at the intranuclear cascade stage of reactions and from lighter clusters, up to fragments with mass numbers A < 8, in the case of CEM, and A < 13, in the case of LAQGSM. Next, we modify MCNP6 to allow calculating and outputting spectra of LF and heavier products with arbitrary mass and charge numbers. The improved version of CEM is implemented into MCNP6. Finally, we test the improved versions of CEM, LAQGSM, and MCNP6 on a variety of measured nuclear reactions. The modified codes give an improved description of energetic LF from particle- and nucleus-induced reactions; showing a good agreement with a variety of available experimental data. They have an improved predictive power compared to the previous versions and can be used as reliable tools in simulating applications involving such types of reactions.

Production of cumulative particles and light nuclear fragments at high p T values beyond the fragmentation region of nuclei in pA collisions at a proton energy of 50 GeV

The first data on the production of cumulative π+, p, and light nuclear fragments d and t emitted from a nucleus with a high transverse momentum at an angle of 35° in the laboratory system have been reported. The data have been obtained at the SPIN setup at the interaction of a 50-GeV proton beam extracted from the U-70 accelerator (IHEP, Protvino) with C, Al, Cu, and W nuclei.

Symmetry energy dependence of light fragment production in heavy-ion collisions

We study the pre-equilibrium light cluster emission in low to intermediate energy heavy ion collisions in transport simulations as a means to obtain information about the density and momentum dependence of the nuclear symmetry potential, i.e. about the asy-stiffness and the neutron-proton effective mass splitting of the symmetry energy. We find that the study of n/p and t/He-3 ratios as a function of the energy of the emitted particles may allow to disentangle these two behaviors The t/He-3 ratios appear to carry similar information as the n/p ratios, making this a promising option for experimental investigations. More n-rich systems enhance the sensitivity to the symmetry energy, while double ratios between n-rich and n-poor systems tend to reduce it. A preliminary comparison to experimental data for the Xe-136, Xe-124 + (124, 112) Sn systems is also shown.

Preequilibrium Emission of Light Fragments in Spallation Reactions

The ability to describe production of light fragments (LF) is important for many applications, such as cosmic-ray-induced single event upsets (SEUs), radiation protection, and cancer therapy with proton and heavy-ion beams. The cascade-exciton model (CEM) and the Los Alamos version of the quark-gluon string model (LAQGSM) event generators in the LANL transport code MCNP6, describe quite well the spectra of fragments with sizes up to 4He across a broad range of target masses and incident energies (up to ∼ 5 GeV for CEM and up to ∼ 1 TeV/A for LAQGSM). However, they do not predict the high-energy tails of LF spectra heavier than 4He well. Most LF with energies above several tens of MeV are emitted during the precompound stage of a reaction. The current versions of our event generators do not account for precompound emission of LF larger than 4He. The aim of our work is to generalize the precompound model to include such processes, leading to increased predictive power of LF production. Extending the model in this way provides preliminary results that have much better agreement with experimental data.

Production of Energetic Light Fragments in Spallation Reactions

Different reaction mechanisms contribute to the production of light fragments (LF) from nuclear reactions. Available models cannot accurately predict emission of LF from arbitrary reactions. However, the emission of LF is important for many applications, such as cosmic-ray-induced single event upsets, radiation protection, and cancer therapy with proton and heavy-ion beams, to name just a few. The cascade-exciton model (CEM) and the Los Alamos version of the quark-gluon string model (LAQGSM), as implemented in the CEM03.03 and LAQGSM03.03 event generators used in the Los Alamos transport code MCNP6, describe quite well the spectra of fragments with sizes up to 4He across a broad range of target masses and incident energies. However, they do not predict high-energy tails for LF heavier than 4He. The standard versions of CEM and LAQGSM do not account for preequilibrium emission of LF larger than 4He. The aim of our work is to extend the preequilibrium model to include such processes. We do this by including the emission of fragments heavier than 4He at the preequilibrium stage, and using an improved version of the Fermi Break-up model, providing improved agreement with various experimental data.

Pulmonary Extranodal Marginal Zone Lymphoma Of MALT Type Associated With Pulmonary Amyloidosis - Two Case Reports

Background Light chain (AL) amyloidosis is typically a systemic disease resulting from the malignant production and deposition of immunoglobulin light chain fragments in various tissues. Pulmonary AL amyloidosis is uncommon but can be seen concomitantly with non-Hodgkin lymphoma (NHL) as one of two distinct syndromes. In the more common presentation, a NHL, typically lymphoplasmacytic lymphoma or extranodal marginal zone lymphoma, produces a measurable serum/urine M-protein or light chain resulting in a systemic AL amyloidosis. There have also been sporadic reports of a less common, nodular form of pulmonary AL amyloidosis due to peritumoral amyloid deposition in patients with pulmonary extranodal marginal zone lymphoma of MALT type. This latter association is probably under-recognized. Here we present two cases from our institution with important diagnostic and therapeutic implications. Case 1 A 60 year old male was found to have bilateral pulmonary nodules. A percutaneous biopsy of the largest lesion in the left perihilar region revealed a MALT lymphoma. He was treated with eight cycles of R-CVP with a partial response. Significant residual disease led to further treatment with radioimmunotherapy using ibritumomab tiuxetan but without additional radiographic improvement. Due to concerns about the persistence of multiple pulmonary nodules, the original diagnostic biopsy was stained with Congo red to reveal amyloid deposition. No measurable monoclonal protein was present in the serum or urine. He has been observed now for an additional 4 years without evidence of progression. This patient has pulmonary amyloidosis in a nodular pattern in conjunction with a pulmonary MALT lymphoma. Pathologic review has shown the individual pulmonary nodules to be composed of both lymphoma and amyloid. The decrease in the size of the nodules with initial chemotherapy indicates a response to therapy, likely of the lymphoma component. The lack of response to typically effective additional therapy and the stability of the nodules over an extended period of time lead us to conclude that the residual nodules are likely to be primarily composed of amyloid. The initial lack of recognition of the amyloid component was disadvantageous and made determination of treatment response difficult. Case 2 A 37 year old male with HIV was found to have multiple pulmonary nodules. Pulmonary wedge resection revealed an extranodal marginal zone lymphoma of MALT type and amyloidosis that was confirmed as AL type by laser dissection and mass spectroscopy. Initial PET/CT demonstrated widespread FDG-avid lymphadenopathy and non-FDG-avid pulmonary nodules. There was no other evidence of systemic amyloidosis. The patient has been treated with three cycles of bendamustine and rituximab. Restaging PET/CT has shown a decrease in FDG-avid lymphadenopathy but no significant improvement in the size or number of pulmonary nodules. His chemotherapy is being continued. This patient has pulmonary AL amyloidosis in association with a stage IV extranodal marginal zone lymphoma. At first glance, the patient appears to have had a discordant response to initial treatment. However, the diagnosis of amyloidosis allows us to determine that his lymphoma has responded to therapy and the lack of response seen in the lungs is likely due to the presence of persistent amyloid. If the diagnosis of pulmonary amyloidosis was not made or known, this may have been mistakenly considered as refractory disease resulting in an unnecessary change in therapy. Conclusion The association between pulmonary amyloidosis and extranodal marginal zone lymphoma of MALT type may be more prevalent than previously recognized. All cases of pulmonary MALT lymphoma should be carefully examined for evidence of amyloid deposition. If proven, imaging studies, serum/urine electrophoresis and serum free light chain studies and organ assessments will help to determine whether the amyloid is a nodular form due to local deposition of light chain fragments or a systemic amyloidosis secondary to NHL. The former has a better prognosis than its systemic counterpart since the amyloidosis is typically localized to the lungs, has a more indolent course and is unlikely to involve other organs. As the above cases highlight, assessment of lymphoma response is greatly complicated by the concurrent presence of amyloid and PET/CT may be particularly useful in this scenario. Disclosures: No relevant conflicts of interest to declare.

Fragmentation and momentum correlations in heavy-ion collisions

The role of momentum correlations is studied in the production of light and medium mass fragments by imposing momentum cut in clusterization the phase space. Our detailed investigation shows that momentum cut has major role to play in the emission of fragments.

Influence of the N/Z degree of freedom on the decay modes of excited nuclear complex formed in Kr+Ca reactions at 5.5 AMeV

The N/Z degree of freedom is expected to play a crucial role in the decay modes of excited nuclei and in the competition between strongly dissipative and fusion mechanisms. In this contribution we present results obtained in 78,82 Kr+40 Ca reactions at 5.5 AMeV using the INDRA detector at GANIL. Discussion will be dedicated to various characteristics of the production of light fragments as for example, kinetic energy distributions, odd-even staggering of the cross-sections and excitation energy stored in fragments. These observables seem to reflect the interplay between the N/Z and angular momentum degrees of freedom at the separation phase. The set of data provides some hints for further explorations in the context of reaction with neutron rich projectile to be delivered in a near future.

Effect of the symmetry energy on nuclear stopping and its relation to the production of light charged fragments

We present a complete systematics (excitation function, impact parameter, system size, isospin asymmetry, and equations of state dependences) of global stopping and fragment production for heavy-ion reactions in the energy range between 50 and 1000 MeV/nucleon in the presence of symmetry energy and an isospin-dependent cross section. It is observed that the degree of stopping depends weakly on the symmetry energy and strongly on the isospin-dependent cross section. However, the symmetry energy and isospin-dependent cross section has an effect of the order of more than 10% on the emission of light charged particles (LCP's). It means that nuclear stopping and LCP's can be used as a tool to get the information of an isospin-dependent cross section. Interestingly, the LCP's emission in the presence of symmetry energy is found to be highly correlated with the global stopping.

Cumulative production of three-nucleon nuclei in 16Op collisions at a momentum of 3.25 GeV/c per nucleon

The production of cumulative three-nucleon nuclei (3H and 3He) in 16Op collisions at a momentum of 3.25 GeV/c per nucleon were studied for the first time under conditions of 4π geometry. The slope parameter of the cross section for the production of cumulative three-nucleon nuclei was determined, and new data on correlations of the yields of A = 3 cumulative nuclei, charged particles, and fragments in 16Op interactions are reported. The properties of cumulative and noncumulative events were found to be substantially different, and evidence for the presence of a common universal feature in the mechanisms for the cumulative production of hadrons and light nuclear fragments was obtained.

Centrality and energy dependence of proton, light fragment and hyperon production

Recent results of the NA49 Collaboration are discussed. These include the energy dependence of stopping and the production of the light fragments t and 3He. New data on the system size dependence of hyperon production at 40A and 158A GeV are also presented.

The Zero-Degree Detector system for fragmentation studies

The measurement of nuclear fragmentation cross-sections requires the detection and identification of individual projectile fragments. If light and heavy fragments are recorded in the same detector, it may be impossible to distinguish the signal from the light fragment. To overcome this problem, we have developed the Zero-degree Detector System (ZDDS). The ZDDS enables the measurement of cross-sections for light fragment production by using pixelated detectors to separately measure the signals of each fragment. The system has been used to measure the fragmentation of beams as heavy as Fe at the NASA Space Radiation Laboratory at Brookhaven National Laboratory and the Heavy Ion Medical Accelerator in Chiba, Japan.

Isotopic effects of fragment-yields in proton induced reactions on Sn isotopes

Analysis of isotopic characteristics of products related to the inclusive data measured using activation method in proton reactions at the energies 0.66, 1.0 and 8.1 GeV with separated tin isotopes is presented. Experimental results are systematized in form of cross section ratios for two targets of different isotope composition. Scaling behavior is observed for reactions with heavy residuals in the same manner as in light fragment production processes. These results are discussed in the light of relevant recent data. Finally, dependence of scaling parameters on the target neutron excess is observed.

Disappearance of shell effects and persistence of an even-odd staggering in the fragment production in nuclear reactions at relativistic energies

The isotopic distributions of fragments produced in the spallation of uranium are strongly influenced by the fission of the excited prefragments, highly fissile nuclei. The competition between fission and evaporation around the doubly-magic nucleus Pb is discussed. The light fragments from Fe beam are produced with a strong enhancement of even-even nuclei compared to the odd-odd in the region of nuclei with equal number of neutrons and protons, N ∼ Z. This staggering in the production of light fragments is not observed in the production of heavy fragments, and is in contradiction with the basis of the statistical model of deexcitation of a hot nucleus. Pairing interaction as a function of the excitation energy and as a function of the isospin of the nucleus are questioned.

Mass dependence in the production of light fragments in heavy-ion collisions

Using the quantum molecular dynamics model coupled with the minimum spanning tree clusterization algorithm, we investigate the system-size effects in the production of light mass fragments (with mass $&lt;~10).$ This was achieved by simulating the collision of symmetric nuclei like $\mathrm{Ca}+\mathrm{Ca},$ $\mathrm{Ni}+\mathrm{Ni},$ $\mathrm{Nb}+\mathrm{Nb},$ $\mathrm{Xe}+\mathrm{Xe},$ $\mathrm{Er}+\mathrm{Er},$ $\mathrm{Au}+\mathrm{Au},$ and $\mathrm{U}+\mathrm{U}$ at incident energies between 50 MeV/nucleon and 1 GeV/nucleon and over full range of impact parameter. Our detailed analysis shows that the triggering of the multifragmentation and its saturation is delayed in heavier systems. The striking result, which is independent of the incident energy as well as of the impact parameter, is that the mass dependence of the multiplicity of any kind of fragment exhibits a power law behavior $\ensuremath{\propto}{A}_{\mathrm{tot}}^{\ensuremath{\tau}},$ where $``{A}_{\mathrm{tot}}''$ is the mass of the composite system. Similar mass dependencies have already been reported in the literature for the fusion process at low incident energy as well as for the production of kaon and collective flow (and its disappearance) at intermediate energies. As reported for the production of kaons, the parameter $\ensuremath{\tau}$ depends on the colliding geometry as well as on the incident energy. No unique dependence of $\ensuremath{\tau}$ (such as, in the case of disappearance of flow) exists. The value of the parameter $\ensuremath{\tau}$ in central low energy collisions is close to 2/3, which suggests the dominance of the mean field. On the other hand, a linear dependence occurs at higher incident energies. Similar trends can also be seen in the preliminary reports of the FOPI experiments.

Statistical analysis of light fragment production from medium energy proton-induced reactions

The light fragment production reactions for 10 MeV to 3 GeV protons incident on 16 O , 27 Al , nat Fe , 93 Nb and nat Ag are analyzed by a combination of an intranuclear cascade model and a generalized evaporation model which includes light nuclei up to Mg as ejectiles. The results suggested that an evaporation process is a significant source of light fragment lighter than or equal to Be produced from targets heavier than O.

Target-dependence of light fragment production in photonuclear reactions at intermediate energies

Yields of7Be,10Be,22Na,24Na and28Mg produced fromnatB,natC,natO,23Na,27Al,natSi,natS,natCl,natK,natCa,natV,55Mn,natFe,59Co,natNi,natCu,89Y,natAg,natIn,141Pr,159Tb,165Ho and197Au in irradiations with bremsstrahlung having maximum end-point energies up to 1200 MeV were measured by γ-ray spectrometry (7Be,22Na,24Na and28Mg) and accelerator mass spectrometry (10Be). The yields of heavier fragments,39Cl,43, 44m, 44g, 46, 47, 48Sc,59Fe, and56, 57, 58, 60Co, were also measured by γ-ray spectrometry in order to survey the relative contribution of fragmentation to spallation and/or fission in the mass yield curves. A distinct difference of the target mass-dependence of these yields has made it possible to disentangle the contributions of photospallation and photofragmentation processes. It was found that the neutron-to-proton ratios of targets strongly affect the formation of the nuclei by fragmentation as revealed in the yields of the isotopic pairs as well as of the single isotopes. The photon results were compared with those of proton-induced reactions, and no clear effect due to the difference of the initial interactions of photons and protons with nuclei was found in the fragment yields.