Thu·Nov 21, 2024Thursday·November 21, 2024

1. 01*

   Untangling the interplay of the Equation-of-State and the Collision Term towards the generation of Directed and Elliptic Flow at intermediate energies

   Tom Reichert🇩🇪 · Jörg Aichelin🇫🇷

   The mechanism for generating directed and elliptic flow in heavy-ion collisions is investigated and quantified for the SIS18 and SIS100 energy regimes. The observed negative elliptic flow $v_2$, at midrapidity has been explained either via (in-plane) shadowing or via (out-of-plane) squeeze-out. To settle this question, we employ the Ultra-relativistic Quantum Molecular Dynamics model (UrQMD) to calculate Au+Au collisions at E${}_{\mathrm{lab}}=0.6A$ GeV, E${}_{\mathrm{lab}}=1.23A$ GeV and $\sqrt{s_{\mathrm{NN}}}=3.0$ GeV using a hard Skyrme type Equation-of-State to calculate the time evolution and generation of directed flow and elliptic flow. We quantitatively distinguish the impact of collisions and of the potential on $v_1$ and $v_2$ during the evolution of the system. These calculations reveal that in this energy regime the generation of $v_1$ and $v_2$ follows from a highly intricate interplay of different processes and is created late, after the system has reached its highest density and has created a matter bridge between projectile and target remnant, which later breaks. Initially, we find a strong out-of-plane pressure. Then follows a strong stopping and the built up of an in-plane pressure. The $v_2$, created by both processes, compensate to a large extend. The finally observed $v_2$ is caused by the potential, reflects the freeze-out geometry and can neither be associated to squeeze-out nor to shadowing. The results are highly relevant for experiments at GSI, RHIC-FXT and the upcoming FAIR facility, but also for experiments at FRIB, and strengthens understanding on the Equation-of-State at large baryon densities.

   ↳ nucl-thnucl-exPRC(2025)·12 citations
2. 02*

   Examining the potential synthesis of new elements with ${}^{294}$Og

   Shuai Zhang🇨🇳 · Gao-Chan Yong🇨🇳 · J. L. Rodríguez-Sánchez🇪🇸 · J. Cugnon🇧🇪

   In the relentless pursuit of expanding the periodic table, the discovery of element 119 remains elusive, despite two decades of dedicated research efforts. The traditional fusion-evaporation approach, although fruitful in the past, now appears to be approaching its operational limits. This scenario sets the stage for considering innovative methodologies essential for further advancements in the field of superheavy elements. Here, we introduce a pioneering strategy aimed at synthesizing element 119 by adapting and extending the nuclear reaction processes previously successful in producing element ${}^{294}$Og. This involved the fusion of ${}^{48}$Ca and ${}^{249}$Cf. Building on this, our novel approach incorporates an additional reactive target -- specifically, hydrogen -- positioned strategically behind the ${}^{249}$Cf. This configuration is designed to facilitate an immediate secondary reaction of the nascent ${}^{294}$Og with hydrogen, potentially forging new pathways to element 119. Preliminary insights also suggest that employing isotopes like deuterium or helium-3 as targets may not only enhance the production rates of element 119 but might also pave the way for the synthesis of even heavier elements, extending up to elements 120 and 121. We delve into the technicalities and feasibility of employing a dual-target method using a ${}^{48}$Ca beam, exploring new horizons in the quest for the superheavy unknown.

   ↳ nucl-thnucl-ex0 citations
3. 03*

   Constraining the Phase-Transition EoS using the Energy Dependence of Directed Flow

   Zhi-Min Wu🇨🇳 · Gao-Chan Yong🇨🇳 · Qingfeng Li🇨🇳

   We propose a hybrid equation of state (VDF+MIT EoS) to describe the hadron-quark phase transition in dense nuclear matter. By coupling this EoS with the AMPT-HC transport model and comparing to recent experimental data on proton and $\Lambda$ directed flow $v_1$, we constrain the transition to likely occur near $5{\rho }_0$--$6{\rho }_0$, ruling out transitions below $3{\rho }_0$. Furthermore, we introduce the energy derivative of the mid-rapidity $v_1$ slope, $d(d{v}_1/dy)/d(\sqrt{s_{NN}})$, as a weakly model-dependent observable. Its zero crossing provides a direct signature of the phase transition critical point, offering a new tool for mapping the QCD phase diagram in future experiments.

   ↳ nucl-thnucl-exPRD(2026)·1 citation
4. 04*

   Exploring hadron-quark phase transition in heavy-ion collisions using particle emission ratios in heavy and light reaction systems

   Xun Zhu🇨🇳 · Gao-Chan Yong🇨🇳

   Based on the AMPT model, which incorporates both hadronic and quark degrees of freedom, we studied the productions of lambda, kaon, proton, and pion in reaction systems ${}^{40}$Ca+${}^{40}$Ca, ${}^{48}$Ca+${}^{48}$Ca, and ${}^{197}$Au+${}^{197}$Au. It is found that the ratios of identical particle emissions from heavy and light reaction systems, especially the emission ratios of strange particles ${\Lambda }^0$ or K${}^{+}$ in heavy and light reaction systems, are highly sensitive to the hadron-quark phase transition in heavy-ion collisions. Detailed explanations and validations of these results are given.

   ↳ nucl-thnucl-exPLB(2025)·1 citation
5. 05*

   Novel features of asymmetric nuclear matter from terrestrial experiments and astrophysical observations of neutron stars

   Tsuyoshi Miyatsu🇰🇷 · Myung-Ki Cheoun🇰🇷 · Kyungsik Kim🇰🇷 · Koichi Saito🇯🇵

   The accurate measurement of neutron skin thickness of ${}^{208}$Pb by the PREX Collaboration suggests a large value of the nuclear symmetry energy slope parameter, $L$, whereas the smaller $L$ is preferred to account for the small neutron-star radii from NICER observations. To resolve this discrepancy between nuclear experiments and astrophysical observations, new effective interactions have been developed using relativistic mean-field models with the isoscalar- and isovector-meson mixing. We investigate the effects of $\delta$-nucleon coupling and $\sigma$--$\delta$ mixing on the ground-state properties of finite nuclei, as well as the characteristics of isospin-asymmetric nuclear matter and neutron stars. Additionally, we explore the role of the quartic $\rho$-meson self-interaction in dense nuclear matter to mitigate the stiff equation of state for neutron stars resulting from the large $\delta$-nucleon coupling. It is found that the nuclear symmetry energy undergoes a sudden softening at approximately twice the saturation density of nuclear matter, taking into account the PREX-2 result, the recent NICER observation of PSR J0437$-$4715, and the binary neutron star merger, GW170817.

   ↳ nucl-thnucl-exFront.in Phys.(2024)·9 citations
6. 06*

   Dispersive Determination of Nucleon Gravitational Form Factors

   Xiong-Hui Cao🇨🇳 · Feng-Kun Guo🇨🇳 · Qu-Zhi Li🇨🇳 · De-Liang Yao🇨🇳

   Being closely connected to the origin of the nucleon mass, the gravitational form factors of the nucleon have attracted significant attention in recent years. We present the first model-independent determinations of the gravitational form factors of the pion and nucleon at the physical pion mass, using a data-driven dispersive approach. The so-called "last global unknown property" of the nucleon, the $D$-term, is determined to be $-3.38_{-0.35}^{+0.34}$. The root mean square radius of the scalar trace density inside the nucleon is determined to be $(0.97\pm 0.03)\text{fm}$. Notably, this value is larger than the proton charge radius, suggesting a modern structural view of the nucleon where gluons, responsible for most of the nucleon mass, are distributed over a larger spatial region than quarks, which dominate the charge distribution, indicating that the radius of the trace density may be regarded as a confinement radius. We also predict the nucleon angular momentum and mechanical radii, providing further insights into the intricate internal structure of the nucleon.

   ↳ hep-phhep-exhep-latnucl-ex+1Nature Commun.(2025)·57 citations
7. 07*

   Probing small neutron skin variations in isotope pairs by hyperon-antihyperon production in antiproton--nucleus interactions

   Falk Schupp🇩🇪 · Josef Pochodzalla🇩🇪 · Michael Bölting🇩🇪 · Martin Christiansen🇩🇪 · Theodoros Gaitanos🇬🇷 · Horst Lenske🇩🇪 · Marcell Steinen🇩🇪

   We propose a new method to study the evolution of the neutron periphery between different isotopes by considering antiproton--nucleus interactions close to the production threshold of $\Lambda \overline{\Lambda }$ and ${\Sigma }^{-}\overline{\Lambda }$ pairs. At low energies, $\Lambda \overline{\Lambda }$ pairs are produced in $\overline{\text{p}}+\text{p}$ collisions, while ${\Sigma }^{-}\overline{\Lambda }$ pairs can only be produced in $\overline{\text{p}}+\text{n}$ interactions. Within a simple geometrical picture we show that the double ratio for the production of ${\Sigma }^{-}\overline{\Lambda }$ and $\Lambda \overline{\Lambda }$ pairs for two different isotopes are related to the variation of the neutron skin thickness between the two nuclei. Performing high statistics calculations with the Gießen Boltzmann--Uehling--Uhlenbeck (GiBUU) transport model for several isotope pairs covering a wide range of elements we verify a strong correlation between the double ratio from the full transport simulations and the schematic model. This correlation enables us to quantify the potential of the proposed method for precise studies of neutron skin variations in isotope chains.

   ↳ nucl-thnucl-exPRC(2025)·2 citations
8. 08*

   Lattice QCD and the Neutron Electric Dipole Moment

   Keh-Fei Liu🇺🇸

   The recent lattice QCD calculations of the neutron and proton electric dipole moments (EDMs) and the CP-violating $\pi \mathrm{NN}$ coupling constant due to the $\theta$ term are reviewed. Progress towards nucleon EDM calculations, including the Weinberg three-gluon operator, and the quark chromoelectric dipole moment operator and their renormalization, is also discussed.

   ↳ hep-lathep-phnucl-exnucl-thAnn.Rev.Nucl.Part.Sci.(2025)·15 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.