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Nuclear Theory·nucl-th

Wednesday·August 24, 2022

12 papers—7 primary·5 cross-listed

All12Primary7Cross-lists5
  1. 01

    Quantifying uncertainties due to irreducible three-body forces in deuteron-nucleus reactions

    Linda Hlophe · Konstantinos Kravvaris · Sofia Quaglioni

    \noindent{\bf Background:} Deuteron-induced nuclear reactions are an essential tool for probing the structure of nuclei as well as astrophysical information such as cross sections. The deuteron-nucleus system is typically described within a Faddeev three-body model consisting of a neutron (), a proton (), and the target nucleus () interacting through pairwise phenomenological potentials. While Faddeev techniques enable the exact description of the three-body dynamics, their predictive power is limited in part by the omission of irreducible neutron-proton-nucleus three-body force (-- 3BF). {\bf Results:} By comparing the Faddeev and NCSM/RGM results, we show that the irreducible -- 3BF has a non-negligible effect on bound state and scattering observables alike. Specifically, the Faddeev approach %are yields a Li ground state that is approximately ~keV shallower than the one obtained with the NCSM/RGM. Additionally, the Faddeev calculations for + scattering yield a resonance that is located approximately ~keV higher in energy compared to the NCSM/RGM result. The shape of the + angular distributions computed using the two approaches also differ, owing to the discrepancy in the predictions of the resonance energy.

    nucl-thPRC(2023)·4 citations
  2. 02

    Decoding the nuclear symmetry energy event-by-event in heavy-ion collisions with machine learning

    Yongjia Wang🇨🇳 · Zepeng Gao🇨🇳 · Hongliang Lü🇨🇳 · Qingfeng Li🇨🇳

    Inferences of the nuclear symmetry energy from heavy-ion collisions are currently based on the comparison of measured observables and transport model simulations. Only the expectation values of observables over all considered events are used in these approaches, however, observables can be obtained event-by-event both in experiments and transport model simulations. By using the light gradient boosting machine (LightGBM), a modern machine-learning algorithm, we present a framework for inferring the density-dependent nuclear symmetry energy from observables in heavy-ion collisions on the event-by-event analysis. The ultrarelativistic quantum molecular dynamics (UrQMD) model simulations are used as training data. The symmetry energy slope parameter extracted with LightGBM event-by-event from test data also by UrQMD has an average spread of approximately 30~MeV from the truth, and is found to be robust against variations in model parameters. In addition, LightGBM can identify features that have the greatest effect on the physics of interest, thereby offering valuable insights. Our study suggests that the present framework can be a powerful tool and may offer a new paradigm to study the underlying physics in heavy-ion collisions.

    nucl-thnucl-exPLB(2022)·18 citations
  3. 03

    Isospin blocking and its effects in heavy-ion collisions

    Ya-Fei Guo🇨🇳 · Gao-Chan Yong🇨🇳

    A concept of \emph{isospin blocking} in the process of isospin diffusion in heavy-ion collisions is raised. Generally, in the process of isospin diffusion, isospin asymmetry would diffuse from the place with large asymmetry to the place with small asymmetry. However, our study shows that the isospin diffusion could be blocked in case the local value of the symmetry energy is larger. We dub this phenomenon ``isospin blocking''. To check this behavior, in the framework of an Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, isospin diffusions in the isotope Sn+Sn reactions at 270 MeV/nucleon are studied. It is shown that the value of the after-diffusion asymmetry is distinctly blocked if the local symmetry energy is large. The effects of the isospin blocking on the isospin asymmetry of dilute and dense matter and the final ratio in heavy ion collisions are demonstrated.

    nucl-thnucl-exPRC(2022)·0 citations
  4. 04

    Influence of entrance channel on production cross section of exotic actinides in multinucleon transfer reactions

    PengHui Chen · Chang Geng · XiangHua Zeng · Zhao-Qing Feng

    Within the framework of the dinuclear system model, the influence of mass asymmetry and the isospin effect on the production of exotic actinides have been investigated systematically. The isotopic yields populate in multinucleon transfer reactions of Ca(48), Kr(86), Xe(136), and U(238) bombarding on Cm(248) are analyzed and compared to the available experimental data. Systematics on the production of unknown actinides from Ac to Lr via the available stable elements on the earth (from Ar to U) as projectiles-induced reactions with Th, U and Cm are investigated thoroughly. Potential energy surface and total kinetic energy distribution for the reaction system are calculated and can be used to predict the production cross-section trends. It is found that the heavier projectile leads to the wider isotopic chain distribution for the same target. The heavier target-based reactions prefer to produce plenty of exotic actinides through both mechanisms of deep-inelastic and quasi-fission reactions. Isospin relaxation plays a crucial role in the colliding process, resulting in actinide isotopic distribution tends to shift to the drip lines. Massive new actinides have been predicted at the level of nanobarn to millibarn. The optimal projectile-target combinations and beam energies were proposed for the forthcoming experiments.

    nucl-thPRC(2022)·6 citations
  5. 05

    Optimization of the number of intrinsic states included in the discrete Generator Coordinate Method

    Jaime Martínez-Larraz · Tomás R. Rodríguez

    We present a mechanism to efficiently pre-select the number of intrinsic many-body states that are used to define the many-body wave functions within the discrete Generator Coordinate Method (GCM). This procedure, based on the proper definition of a natural basis of orthonormal states, does not require the evaluation of the non-diagonal Hamiltonian kernels to do the selection and helps to reduce the numerical instabilities. The performance of the method is analyzed in detail in the ground state and excited states of some selected nuclei computed with the Gogny energy density functional.

    nucl-thPRC(2022)·8 citations
  6. 06

    Probing system size dependence at high baryon density by systematic comparison of Ag+Ag and Au+Au reactions at 1.23 GeV

    Tom Reichert🇩🇪 · Apiwit Kittiratpattana🇩🇪 · Pengcheng Li🇩🇪 · Jan Steinheimer🇩🇪 · Marcus Bleicher🇩🇪

    We present UrQMD predictions for the comparison of the recently measured Ag+Ag and Au+Au runs at a beam energy of = 1.23~GeV explored by the HADES experiment. To this aim, different centrality definitions are investigated: We suggest that in the case of particle production, both systems should be compared at the same number of participating nucleons, while for a comparison of the (elliptic) flow, a selection on the initial state eccentricity - as in high energy reaction - is better suited. Generally, we find good agreement between both system, if these centrality criteria are used. Specifically, the deuteron yields per participant and the pion to proton ratios are shown to scale with except for very central Ag+Ag reactions due to stronger stopping in such reactions. The elliptic flow in both systems follows inital state eccentricity scaling, albeit with the opposite sign as compared to high energies, suggesting a strong relation between final flows and the initial state also at the low energies explored here. The observation of this scaling might then allow to obtain further information on the expansion properties (and the EoS) of matter at high baryon densities.

    nucl-thnucl-exJ.Phys.G(2023)·3 citations
  7. 07

    Few nucleons scattering in pionless effective field theory

    Martin Schäfer🇮🇱 · Betzalel Bazak🇮🇱

    We present a comprehensive theoretical study of low-energy few nucleon scattering for systems with . To this end, we utilize pionless effective field theory, which we employ at next-to-leading order. We show that at this level the theory yields accurate predictions for the low-energy scattering parameters in all studied channels. These predictions are on par with the best experimental evaluations and the available theoretical calculations. We confirm the recent observation that a four-body force is needed at next-to-leading-order and find that for nuclear systems it only appears in a single spin-isospin channel.

    nucl-thPRC(2023)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE