Nuclear Theory·nucl-th

Tuesday·September 26, 2023

10 papers—6 primary·4 cross-listed

01
Why is $Pb^{208}$ the heaviest stable nuclide?
B. P. Kosyakov🇷🇺 · E. Yu. Popov🇷🇺 · M. A. Vronsky🇷🇺
In an effort to understand nuclei in terms of quarks we develop an effective theory to low-energy quantum chromodynamics in which a single quark contained in a nucleus is driven by a mean field due to other constituents of the nucleus. We analyze the reason why the number of $d$ quarks in light stable nuclei is much the same as that of $u$ quarks, while for heavier nuclei beginning with $Ca^{40}$ , the number of $d$ quarks is greater than the number of $u$ quarks. To account for the finiteness of the periodic table, we invoke a version of gauge/gravity duality between the dynamical affair in stable nuclei and that in extremal black holes. With the assumption that the end of stability for heavy nuclei is dual to the occurrence of a naked singularity, we find that the maximal number of protons in stable nuclei is $Z_{m a x}^{H} \approx 82$ .
nucl-thhep-phEPJC(2024)·3 citations
02
What can we learn from recent $2 ν β β$ experiments?
Dong-Liang Fang🇨🇳
With recent measurements of the two neutrino double beta decay high precision electron spectra, combining with charge exchange or $β$ -decay experimental data, we give severe constraints over the current nuclear many body calculations. Our calculation shows that QRPA approach can well reproduce the measured spectra for the two open shell nuclei, $^{82}$ Se and $^{100}$ Mo. For the closed shell nucleus $^{136}$ Xe, QRPA can also reproduce the spectra with proper treatments. We also find that considering the high-lying state reduction, Nuclear Shell Model can also well reproduce the spectra as well as B(GT) strength under a unique quenched $g_{A}$ . For $^{136}$ Xe, we find that the flip of the sign for the decay strength will lead the spectra to go beyond HSD. These results call for future high precision measurement of charge-exchange reaction.
nucl-thnucl-exCPC(2024)·2 citations
03
Strangelets formation in high energy heavy-ion collisions
Huai-Min Chen🇨🇳 · Cheng-Jun Xia🇨🇳 · Guang-Xiong Peng🇨🇳
The properties of phase diagram of strange quark matter in equilibrium with hadronic matter at finite temperature are studied, where the quark phase and hadron phase are treated by baryon density-dependent quark mass model and hadron resonance gas model with hard core repulsion factor, respectively. The thermodynamic conditions for the formation of metastable strange quark droplets ("strangelets") in relativistic nuclear collisions are discussed. We obtained a rich structure of the phase diagram at finite temperature, and study the dynamical trajectories of an expanding strange fireball. Our results indicate that the strangeness fraction fs, perturbation parameter C, and confinement parameter D have strong influence on the properties of phase diagram and the formation of strangelets. Consider the isentropic expansion process, we found that the initial entropy per baryon is less than or equal to 5, which gives a large probability for the formation of strangelets. Furthermore, a sufficiently large strangeness fraction fs and one-gluon-exchange interaction and sufficiently small confinement interaction create possibilities for the formation of strangelets. On the contrary, the fireball will always complete the hadronization process when fs=0 or C>=0 or D^{1/2}>=170 MeV.
nucl-thhep-phPRD(2024)·8 citations
04
Hybrid Strangeon Stars
Chen Zhang🇨🇳 · Yong Gao🇨🇳 · Cheng-Jun Xia🇨🇳 · Renxin Xu🇨🇳
It was conjectured that the basic units of the ground state of bulk strong matter may be strange-clusters called strangeons, and they can form self-bound strangeon stars that are highly compact. Strangeon stars can develop a strange quark matter (SQM) core at high densities, particularly in the color-flavor-locking phase, yielding a branch of hybrid strangeon stars. We explore the stellar structure and astrophysical implications of hybrid strangeon stars. We find that hybrid strangeon stars can meet various astrophysical constraints on pulsar masses, radii, and tidal deformabilities. Finally, we show that the strangeon-SQM mixed phase is not preferred if the charge-neutrality condition is imposed at the strangeon-SQM transition region.
nucl-thastro-ph.HEgr-qchep-phPRD(2023)·19 citations
05
Emergence of hydrodynamics in expanding relativistic plasmas
Jean-Paul Blaizot🇫🇷
I consider a simple set of equations that govern the expansion of boost-invariant plasmas of massless particles. These equations describe the transition from a collisionless regime at early time to hydrodynamics at late time. Their mathematical structure encompasses all versions of second order hydrodynamics. We emphasize that the apparent success of Israel-Stewart hydrodynamics at early time has little to do with ``hydrodynamics'' proper, but rather with a particular feature of Israel-Stewart equations that allows them to effectively mimic the collisionless regime.
nucl-th1 citation
06
Examining the influence of hadronic interactions on the directed flow of identified particles in RHIC Beam Energy Scan energies using UrQMD model
Aswini Kumar Sahoo🇮🇳 · Prabhupada Dixit🇮🇳 · Md Nasim🇮🇳 · Subhash Singha🇨🇳
The directed flow of identified particles can serve as a sensitive tool for investigating the interactions during initial and final states in heavy ion collisions. This study examines the rapidity-odd directed flow ( $v_{1}$ ) and its slope ( $d v_{1} / d y$ ) for $π^{\pm}$ , $K^{\pm}$ , p, and $p ˉ$ in Au+Au collisions at different collision centralities and beam energies ( $s_{N N}$ = 7.7, 11.5, 14.5, 19.6, 27, and 39 GeV) using the UrQMD model. We investigate the impact of late-stage hadronic interactions on charge dependent $v_{1} (y)$ and its slope by modifying the duration of the hadronic cascade lifetime ( $τ$ ). The energy dependence of $d v_{1} / d y$ for p ( $p ˉ$ ) exhibits distinct pattern compared to $π^{\pm}$ and $K^{\pm}$ . Notably, we observe a change in the sign reversal position of proton $d v_{1} / d y$ at different beam energies with varying $τ$ in central and mid-central collisions. Moreover, the difference in $d v_{1} / d y$ between positively and negatively charged hadrons ( $Δ d v_{1} / d y$ ) demonstrates a stark centrality dependence for different particle species. The deuteron displays a significant increase in $d v_{1} / d y$ with increasing $τ$ compared to p and n. This investigation underscores the importance of considering the temporal evolution and duration of the hadronic phase when interpreting the sign reversal, charge splitting of $v_{1}$ and light nuclei formation at lower RHIC energies.
nucl-thnucl-exMod.Phys.Lett.A(2024)·4 citations
07
Investigating nonflow contribution subtraction in d-Au collisions with AMPT model
Zuman Zhang🇨🇳 · Sha Li🇨🇳 · Ning Yu🇨🇳 · Qiao Wu🇨🇳
This paper presents research that focuses on nonflow contribution subtraction in heavy-ion collisions, using a multiphase transport model (AMPT). Specifically, the study aims to investigate the behavior of charged particle elliptic flow ( $v_{2}$ ) in d-Au collisions at a collision energy of $s_{NN} = 200$ GeV and to determine the impact of nonflow sources, such as jet correlations and resonance decays, in small collision systems. To reduce nonflow effects, the per-trigger yield distribution in peripheral d-Au collisions or pp collisions with the same collision energy is subtracted. Our results show that the nonflow effects in central and mid-central collisions are not strongly dependent on subtracting the per-trigger yield distribution in peripheral d-Au collisions or pp collisions. Furthermore, the elliptic flow of charged particles, after removing nonflow effects through two subtracting methods from this work, exhibits consistency in various collision centrality classes. We also discuss comparisons with measurements from d-Au collisions at $s_{NN} = 200$ GeV. Overall, this work provides valuable insights and serves as a reference for researchers studying nonflow contribution subtraction in experiments with small collision systems.
↳ nucl-exnucl-thEPJA(2023)·3 citations
08
Bubble nucleation in the two-flavor quark-meson model
Junrong Wang🇨🇳 · Ziwan Yu🇨🇳 · Hong Mao🇨🇳
We investigate the dynamics of a first-order quark-hadron transition via homogeneous thermal nucleation in the two-flavor quark-meson model. The contribution of the fermionic vacuum loop in the effective thermodynamics potential and phase diagram together with the location of critical end point (CEP) have been obtained in the temperature and chemical potential plane. For a weak and strong first-order phase transition, by taking the temperature as a variable, the critical bubble profiles, the evolutions of the surface tension and the saddle-point action in the presence of a nucleation bubble are numerically calculated in detail when fixing the chemical potentials at $μ = 306 MeV$ and $μ = 309 MeV$ . Our results show that the system could be trapped in the metastable state for a long time as long as the temperature is between the metastable region characterized by the up and low spinodal lines. Moreover, the surface tension at criticality will rise up to about $4 MeV/f m^{2}$ when the chemical potential is very high. Such a small value of the surface tension would favor a mixed phase in the cores of compact stars and may have an important implication in astrophysics.
↳ hep-phnucl-thCPC(2024)·7 citations
09
A New Model for Jet Energy Loss in Heavy Ion Collisions
Alexander Lind🇫🇷 · Iurii Karpenko🇫🇷 · Martin Rohrmoser🇵🇱 · Joerg Aichelin🇫🇷 · Pol Gossiaux🇫🇷 · Klaus Werner🇫🇷
We present a new model for jet quenching from coherent radiation in a brick medium. The jet energy loss is simulated as a perturbative final-state vacuum parton shower followed by a medium-induced shower originating from elastic and radiative collisions with the medium constituents. Coherency is achieved by starting with trial gluons that act as field dressing of the initial jet parton. These are formed according to a Gunion-Bertsch seed. The QCD version of the LPM effect is attained by increasing the phase of the trial gluons through elastic scatterings with the medium. Above a phase threshold, the trial gluons will be realised and can produce coherent radiation themselves. The model has been implemented in a Monte Carlo code and has been validated by successfully reproducing the BDMPS-Z prediction for the energy spectrum. The realistic case with minimal assumptions are also produced and shown. In particular, we show the influence of various parameters on the energy spectrum and transverse momentum distribution, such as the in-medium quark masses, the energy transfer in the recoil process, and the phase accumulation criteria, especially for low and intermediate energy gluons. Future studies will allow for the interface with full simulations of the quark-gluon-plasma with hydrodynamic evolution, such as vHLLE, along with subsequent hadronisation of the jet partons in order to produce realistic distributions that can be directly compared to LHC and RHIC data.
↳ hep-phnucl-thPoS(2024)·0 citations
10
High precision measurement of the $^{99}$ Tc $β$ spectrum
Michael Paulsen🇩🇪 · Philipp Ranitzsch🇩🇪 · Martin Loidl🇫🇷 · Matias Rodrigues🇫🇷 · Karsten Kossert🇩🇪 · Xavier Mougeot🇫🇷 · Abilasha Singh🇫🇷 · Sylvain Leblond🇫🇷 · Jörn Beyer🇩🇪 · Lina Bockhorn🇩🇪 · Christian Enss🇩🇪 · Mathias Wegner · Sebastian Kempf · Ole Nähle🇩🇪
Highly precise measurements of the $^{99}$ Tc beta spectrum were performed in two laboratories using metallic magnetic calorimeters. Independent sample preparations, evaluation methods and analyses yield consistent results and the spectrum could be measured down to less than 1 keV. Consistent beta spectra were also obtained via cross-evaluations of the experimental data sets. An additional independent measurement with silicon detectors in a $4 π$ configuration confirms the spectrum shape above 25 keV. Detailed theoretical calculations were performed including nuclear structure and atomic effects. The spectrum shape was found to be sensitive to the effective value of the axial-vector coupling constant. Combining measurements and predictions, we extracted $Q_{β} =$ 295.82(16) keV and $g_{A}^{eff} = 1.530 (83)$ . Furthermore, we derived the mean energy of the beta spectrum $E_{β}$ =98.45(20) keV, $lo g f = - 0.47660 (22)$ and $lo g f t = 12.3478 (23)$ .
↳ nucl-exnucl-thphysics.ins-detPRC(2024)·16 citations

Affiliations

first authorsco-authorsvia INSPIRE