Nuclear Theory·nucl-th

Tuesday·August 16, 2022

10 papers—6 primary·4 cross-listed

01
Skyrme-Hartree-Fock-Bogoliubov mass models on a 3D mesh: II. Time-reversal symmetry breaking
Wouter Ryssens🇧🇪 · Guillaume Scamps🇧🇪 · S. Goriely🇧🇪 · Michael Bender🇫🇷
Models based on nuclear energy density functionals can provide access to a multitude of observables for thousands of nuclei in a single framework with microscopic foundations. Such models can rival the accuracy of more phenomenological approaches, but doing so requires adjusting parameters to thousands of nuclear masses. To keep such large-scale fits feasible, several symmetry restrictions are generally imposed on the nuclear configurations. One such example is time-reversal invariance, which is generally enforced via the Equal Filling Approximation (EFA). Here we lift this assumption, enabling us to access the spin and current densities in the ground states of odd-mass and odd-odd nuclei and which contribute to the total energy of such nuclei through so-called "time-odd" terms. We present here the Skyrme-based BSkG2 model whose parameters were adjusted to essentially all known nuclear masses without relying on the EFA, refining our earlier work [G. Scamps et al., EPJA 57, 333 (2021), arXiv:2011.07904]. Moving beyond ground state properties, we also incorporated information on the fission barriers of actinide nuclei in the parameter adjustment. The resulting model achieves a root-mean-square (rms) deviation of (i) 0.678 MeV on 2457 known masses, (ii) 0.027 fm on 884 measured charge radii, (iii) 0.44 MeV and 0.47 MeV, respectively, on 45 reference values for primary and secondary fission barriers of actinide nuclei, and (iv) 0.49 MeV on 28 fission isomer excitation energies. We limit ourselves here to a description of the model and the study the impact of lifting the EFA on ground state properties such as binding energies, deformation and pairing, deferring a detailed discussion of fission to a forthcoming paper.
nucl-thEPJA(2022)·43 citations
02
There and Sharp Again: The Circle Journey of Nucleons and Energy Deposition
Giuliano Giacalone🇩🇪
A central question in high-energy nuclear phenomenology is how the geometry of the quark-gluon plasma (QGP) formed in relativistic nuclear collisions is precisely shaped. In our understanding of such processes, two features are especially crucial for the determination of the QGP geometry, respectively, the nucleon size and the energy deposition scheme. This contribution reports on the (circular) evolution of such features in state-of-the-art model incarnations of heavy-ion collisions over the past seven years. Ideas for future directions of investigation are pointed out.
nucl-thhep-exhep-phnucl-ex14 citations
03
Testing the collectivity in large and small colliding systems with test particles
Han-Sheng Wang🇨🇳 · Guo-Liang Ma🇨🇳
We propose a test-particle method to probe the transport dynamics of the establishment and development of collective flow in large and small systems of heavy-ion collisions. We place test particles as passengers into the partonic medium created by Au $+$ Au midcentral collisions at $s_{N N}$ = 200 GeV and $p$ $+$ Pb central collisions at $s_{N N}$ = 5.02 TeV, using a multiphase transport model. With the help of test particles in two extreme test cases, we demonstrate that parton collisions play an important role in establishing and developing collectivity in large and small colliding systems. The collectivity established by final state parton collisions is much stronger in large colliding systems compared to small colliding systems. The collectivity from the initial state can persist or survive more easily in small colliding systems than in large colliding systems due to fewer parton collisions. Our study provides a new method to understand the origin of collectivity in large and small colliding systems at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider.
nucl-thhep-phnucl-exPRC(2022)·4 citations
04
Relativistic correction to the dissociation temperature of B_c mesons in the hot medium
Guangyu Li🇨🇳 · Baoyi Chen🇨🇳 · Yunpeng Liu🇨🇳
By solving two body Dirac equations with potentials at finite temperature, we calculated the dissociation temperature T_d of B_c mesons in the quark-gluon plasma. It is found that the T_d becomes higher with the relativistic correction than the T_d from the Schroedinger equation. Both the short range interaction and the constant term of the potential at the long-range scale have a contribution to the shift of T_d, while the spin interaction is negligible.
nucl-thhep-phCPC(2023)·1 citation
05
Unified description of high-energy nuclear collisions based on dynamical core--corona picture
Yuuka Kanakubo🇯🇵
I establish the dynamical core--corona initialization framework (DCCI2) as a state-of-the-art dynamical framework that is capable of describing small and large colliding systems at the LHC energies. Under the core--corona picture, contributions from both equilibrated (core) and non-equilibrated (corona) components are implemented. I describe the dynamical separation of the system into the core and corona at the initial stage by incorporating the core--corona picture into the novel dynamical initialization framework. With DCCI2, I simulate $p$ + $p$ collisions at $s = 7, 13$ TeV and $P b$ + $P b$ collisions at $s_{NN} = 2.76$ TeV. Especially, I extract the fractions of core and corona components in final hadron yields in $p$ + $p$ and $P b$ + $P b$ collisions as functions of multiplicity, and reveal that the core components become dominant at $⟨ d N_{ch} / d η ⟩_{∣ η ∣ < 0.5} \approx 20$ . I also find that the corona contribution at very low $p_{T}$ (below $p_{T} \approx 1$ GeV) is non-negligible even in $P b$ + $P b$ collisions and show that such contributions significantly affect $p_{T}$ -integrated flow coefficients. These results strongly suggest the importance of considering non-equilibrated components to extract transport coefficients of quark-gluon plasma from model-to-data comparisons quantitatively.
nucl-thhep-phnucl-ex2 citations
06
A Semi-analytical Method of Calculating Nuclear Collision Trajectory in the QCD Phase Diagram
Zi-Wei Lin🇺🇸 · Todd Mendenhall🇺🇸
The finite nuclear thickness affects the energy density $ϵ (t)$ and conserved-charge densities such as the net-baryon density $n_{B} (t)$ produced in heavy ion collisions. While the effect is small at high collision energies where the Bjorken energy density formula for the initial state is valid, the effect is large at low collision energies, where the nuclear crossing time is not small compared to the parton formation time. The temperature $T (t)$ and chemical potentials $μ (t)$ of the dense matter can be extracted from the densities for a given equation of state (EOS). Therefore, including the nuclear thickness is essential for the determination of the $T$ - $μ_{B}$ trajectory in the QCD phase diagram for relativistic nuclear collisions at low to moderate energies such as the RHIC-BES energies. In this proceeding, we will first discuss our semi-analytical method that includes the nuclear thickness effect and its results on the densities $ϵ (t), n_{B} (t), n_{Q} (t)$ , and $n_{S} (t)$ . Then, we will show the extracted $T (t), μ_{B} (t), μ_{Q} (t)$ , and $μ_{S} (t)$ for a quark-gluon plasma using the ideal gas EOS with quantum or Boltzmann statistics. Finally, we will show the results on the $T$ - $μ_{B}$ trajectories in relation to the possible location of the QCD critical end point. This semi-analytical model provides a convenient tool for exploring the trajectories of nuclear collisions in the QCD phase diagram.
nucl-thRev.Mex.Fis.Suppl.(2022)·2 citations
07
Repulsive vector interaction as a trigger for the non-conformal peak in $V_{s}^{2}$
Marcus Benghi Pinto🇧🇷
Considering the NJL model with a repulsive vector channel, parametrized by $G_{V}$ , I show that one may generate a non-monotonic behavior for the speed of sound which peaks at $V_{s}^{2} > 1/3$ . This can be achieved by assuming $G_{V}$ to be density dependent so that the resulting EoS is stiff/repulsive at low densities and soft/non-repulsive at high densities. The interpolation between the two regimes happens through a cross-over which takes place after the first order chiral transition sets in. The model explicitly shows that a non-conformal peak in $V_{s}^{2}$ is not in tension with the QCD trace anomaly being positive at all densities, supporting recent claims in this direction. A brief discussion on how the running coupling may affect the mass-radius relation is carried out in the context of simple non-strange quark stars.
↳ hep-phnucl-th5 citations
08
$X (3872)$ and $T_{cc}$ : structures and productions in heavy ion collisions
Hyeongock Yun🇰🇷 · Daeho Park🇰🇷 · Sungsik Noh🇰🇷 · Aaron Park🇰🇷 · Woosung Park🇰🇷 · Sungtae Cho🇰🇷 · Juhee Hong🇰🇷 · Yongsun Kim🇰🇷 · Sanghoon Lim🇰🇷 · Su Houng Lee🇰🇷
We argue why the recently observed $T_{cc}$ could either be a compact multiquark configuration or a loosely bound molecular configuration composed of charmed mesons, whereas the $X (3872)$ is most likely a molecular configuration. The argument is based on different short range interactions for these tetraquark states coming from the color-color and color-spin interaction in a quark model, and the presence of a common strong D-wave mixing at larger distance similar to the deuteron case, which for the molecular configurations lead to large sizes. Such an analogy at large distance allows us to calculate the transverse momentum dependence of the loosely bound molecular configuration of tetraquarks produced in heavy ion collisions using the coalescence model that successfully reproduces the deutron data using the proton spectra. The ratio of the integrated $X (3872)$ yield obtained from our method to the $ψ (2 S)$ yield obtained from statistical hadronization model method is calculated to be $0.806 \pm 0.234$ , which is a factor of 2.47 larger than that obtained by using statistical model predictions for both particles and in line with the data from the CMS experiment. As the previously calculated transverse momentum distribution of the $T_{cc}$ assuming the structure to be a compact multiquark configuration is markedly different, experimental measurements of the transverse distribution of the tetraquark states will discriminate between their two possible structures.
↳ hep-phnucl-thPRC(2023)·33 citations
09
Information entropy of nuclear electromagnetic transitions in AdS/QCD
Roldao da Rocha🇧🇷
Electromagnetic transitions involving nucleons and their resonances are here presented in the fermionic sector of the AdS/QCD soft-wall model, using the differential configurational entropy (DCE) as a measure of information entropy. The DCE is employed to derive adjustable parameters that define the minimal and nonminimal couplings in the nuclear interaction with a gauge vector field, in the nucleonic $γ N \to N^{*} (1535)$ transition. The values obtained comply with phenomenological data with good accuracy.
↳ hep-thnucl-thNPB(2023)·7 citations
10
Fluctuations of conserved charges in strong magnetic fields from lattice QCD
Heng-Tong Ding🇨🇳 · Sheng-Tai Li🇨🇳 · Jun-Hong Liu🇨🇳 · Xiao-Dan Wang🇨🇳
We present the first lattice QCD results of the second order fluctuations of and correlations among net baryon number, electric charge and strangeness in (2+1)-flavor lattice QCD in the presence of a background magnetic field with physical pion mass $m_{π} = 135$ MeV. To mimic the magnetic field strength produced in the early stage of heavy-ion collision experiments we use 6 different values of the magnetic field strength up to $\sim$ 10 $m_{π}^{2}$ . We find that the correlations between baryon number and electric charge along the transition line are substantially affected by magnetic fields in the current $e B$ window, which could be useful for probing the existence of a magnetic field in heavy-ion collision experiments.
↳ hep-lathep-phnucl-exnucl-thActa Phys.Polon.Supp.(2023)·16 citations

Affiliations

first authorsco-authorsvia INSPIRE