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Nuclear Theory·nucl-th

Tuesday·April 30, 2024

15 papers—7 primary·8 cross-listed

All15Primary7Cross-lists8
  1. 01

    Contribution to differential and modification in small systems from color fluctuation effects

    Dennis V. Perepelitsa🇺🇸

    A major complication in the search for jet quenching in proton- or deuteron-nucleus collision systems is the presence of physical effects which influence the experimental determination of collision centrality in the presence of a hard process. For example, in the proton color fluctuation picture, protons with a large Bjorken- () parton interact more weakly with the nucleons in the nucleus, leading to a smaller (larger) than expected yield in large (small) activity events. A recent measurement by PHENIX compared the yield of neutral pion and direct photon production in +Au collisions, under the argument that the photon yields correct for such biases, and the difference between the two species is thus attributable to final-state effects (i.e., jet quenching). The main finding suggests a significant degree of jet quenching for hard processes in small systems. In this paper, I argue that the particular photon and pion events selected by PHENIX arise from proton configurations with significantly different Bjorken- distributions, and thus are subject to different magnitudes of modification in the color fluctuation model. Using the results of a previous global analysis of RHIC and LHC data, I show that potentially all of the pion-to-photon difference in PHENIX data can be described by a proton color fluctuation picture at a quantitative level before any additional physics from final-state effects is required. This finding reconciles the interpretation of the PHENIX measurement with others at RHIC and LHC, which have found no observable evidence for jet quenching in small systems.

    nucl-thhep-phnucl-exPRC(2024)·18 citations
  2. 02

    Fission Fragment Yields Of U Evaluated By The CCONE Code System

    Futoshi Minato · Osamu Iwamoto

    Fission fragment yield evaluations are one of the important nuclear data studies. Fission accompanies various physical observables such as prompt fission neutron, prompt fission gamma, and delayed-neutrons. When evaluating fission fragment yields, a study including correlations among those observables is essentially required. However, fission fragment yield data in the past JENDL libraries have been made by focusing only on experimental fragment yields, decay heats, and delayed neutron yields, and they have not been expanded into a wider range of fission observables. This is because the evaluation method adopted in the JENDL libraries could not study fission fragment yields and particle emissions from fragments simultaneously. To solve this problem, a calculation system with CCONE code is newly developed to estimate not only independent and cumulative fission fragment yields but also prompt fission neutron, prompt fission gamma, decay heats, and delayed-neutrons simultaneously. This system enables us to study a correlation between various fission observables. To determine lots of parameters in this system efficiently, a Gaussian process and a least square fitting are adopted. We tested the calculation system through a thermal neutron-induced fission on U. In this paper, we demonstrate the performance of the parameter search method and show that experimental fission fragment yield data and other observables resulting from fission are reproduced well by the new calculation system.

    nucl-thPRC(2024)·0 citations
  3. 03

    Prolate-oblate shape transitions and O(6) symmetry in even-even nuclei: A theoretical overview

    Dennis Bonatsos · Andriana Martinou · S.K. Peroulis · T.J. Mertzimekis · N. Minkov

    Prolate to oblate shape transitions have been predicted in an analytic way in the framework of the Interacting Boson Model (IBM), determining O(6) as the symmetry at the critical point. Parameter-independent predictions for prolate to oblate transitions in various regions on the nuclear chart have been made in the framework of the proxy-SU(3) and pseudo-SU(3) symmetries, corroborated by recent non-relativistic and relativistic mean field calculations along series of nuclear isotopes, with parameters fixed throughout, as well as by shell model calculations taking advantage of the quasi-SU(3) symmetry. Experimental evidence for regions of prolate to oblate shape transitions is in agreement with regions in which nuclei bearing the O(6) dynamical symmetry of the IBM have been identified, lying below major shell closures. In addition, gradual oblate to prolate transitions are seen when crossing major nuclear shell closures, in analogy to experimental observations in alkali clusters.

    nucl-thPhys.Scripta(2024)·18 citations
  4. 04

    Three-body analysis reveals the significant contribution of minor He -wave component in LiHe cross section

    Shoya Ogawa · Kazuki Yoshida · Yoshiki Chazono · Kazuyuki Ogata

    Li is usually treated as an three-body system, and the validity of this picture is important for understanding Li reactions. The (,) reaction is a powerful method to study the structure of valence nucleons in Li. Recently, the new experimental data of the Li(,)He reaction have been obtained and should be analyzed. We investigate the Li(,)He reaction using the three-body wave function of Li and study the validity of this model. We calculate the Li wave function by using Gaussian expansion method, and the function is used to obtain the relative wave function between and He. We combine the relative wave function with the distorted wave impulse approximation. Our results reproduce the experimental data of the triple differential cross section within about 10\% difference in the absolute values, and contributions from both - and -wave states of He in Li are found to be important. We can qualitatively understand the Li(,)He reaction by describing Li with the three-body model. Contribution from the -wave component is important in reproducing the experimental data in the zero recoil-momentum region.

    nucl-thPRC(2025)·2 citations
  5. 05

    Exploring system size dependence of jet modification in heavy-ion collisions

    Yang He🇨🇳 · Mengxue Zhang🇨🇳 · Maowu Nie🇨🇳 · Shanshan Cao🇨🇳 · Li Yi🇨🇳

    In relativistic heavy-ion collisions, jet quenching in quark-gluon plasma (QGP) has been extensively studied, revealing important insights into the properties of the color deconfined nuclear matter. Over the past decade, there has been a surge of interest in the exploration of QGP droplets in small collision systems like + or +A collisions driven by the observation of collective flow phenomena. However, the absence of jet quenching, a key QGP signature, in these systems poses a puzzle. Understanding how jet quenching evolves with system size is crucial for uncovering the underlying physics. In this study, we employ the linear Boltzmann transport (LBT) model to investigate jet modification in Ru+Ru, Zr+Zr, and Au+Au collisions at GeV. Our findings highlight the system size sensitivity exhibited by jet nuclear modification factor () and jet shape (), contrasting to the relatively weak responses of jet mass (), girth () and momentum dispersion () to system size variations. These results offer invaluable insights into the system size dependence of the QGP properties and await experimental validation at the Relativistic Heavy-Ion Collider.

    nucl-thhep-phnucl-exPRC(2024)·2 citations
  6. 06

    Implication of odd-even staggering in the charge radii of calcium isotopes

    Rong An · Xiang Jiang · Na Tang · Li-Gang Cao · Feng-Shou Zhang

    Inspired by the profoundly observed odd-even staggering and the inverted parabolic-like shape in charge radii along calcium isotopic chain, the ground state properties of calcium isotopes are investigated by constraining the root-mean-square (rms) charge radii under the covariant energy density functionals with effective forces NL3 and PK1. In this work, the pairing correlations are tackled by solving the state-dependent Bardeen-Cooper-Schrieffer equations. The calculated results suggest that the binding energies obtained by the radius constraint method have been slightly changed by about . But for charge radii, the corresponding results deriving from NL3 and PK1 forces have been increased by about and , respectively. This means that charge radius is a more sensitive quantity in the calibrated protocol. Meanwhile, it is found that the reproduced charge radii of calcium isotopes are attributed to the rather strong isospin dependence of effective potential. The odd-even oscillation behavior can also be presented in the proton Fermi energies along calcium isotopic family, but keep opposite trends with respect to the corresponding binding energies and charge radii. As encountered in charge radii, the weakened odd-even oscillation behavior is still emerged from the proton Fermi energies at the neutron numbers and as well, but not in binding energies.

    nucl-thnucl-exCommun.Theor.Phys.(2025)·0 citations
  7. 07

    Disentangling the development of collective flow in high energy proton proton collisions with a multiphase transport model

    Liang Zheng🇨🇳 · Lian Liu🇨🇳 · Zi-Wei Lin🇺🇸 · Qi-Ye Shou🇨🇳 · Zhong-Bao Yin🇨🇳

    In this work, we investigate the collective flow development in high energy proton proton (pp) collisions with a multiphase transport model (AMPT) based on PYTHIA8 initial conditions with a sub-nucleon structure. It is found that the PYTHIA8 based AMPT model can reasonably describe both the charged hadron productions and elliptic flow experimental data measured in pp collisions at TeV. By turning on the parton and hadron rescatterings in AMPT separately, we find that the observed collective flow in pp collisions is largely developed during the parton evolution, while no significant flow effect can be generated with the pure hadronic rescatterings. It is also shown that the parton escape mechanism is important for describing both the magnitude of the two-particle cumulant and the sign of the four-particle cumulants. We emphasize that the strong mass ordering of the elliptic flow results from the coalescence process in the transport model and can thus be regarded as unique evidence related to the creation of deconfined parton matter in high energy pp collisions.

    nucl-thhep-phnucl-exEPJC(2024)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE