Nuclear Theory·nucl-th

Tuesday·June 4, 2019

15 papers—10 primary·5 cross-listed

01
The structure of cold neutron star with a quark core within the MIT and NJL models
T. Yazdizadeh🇮🇷 · G. H. Bordbar🇮🇷
Neutron star due to their high interior matter density are expected to be composed of a quark core, a mixed quark-hadron matter, and a layer of hadronic matter. Thus, in this paper, we compute the equation of state of these parts of neutron star to evaluate its structure properties. We use two models for describing EOS of quark matter, NJL and MIT bag models, and employ three approaches in this work. A density dependent bag constant satisfy the quark confinement in the simple MIT bag model. We also study the interaction behavior of quarks, firstly one gluon exchange within MIT bag model and the secondly dynamical mass will be held as effective interaction that roles between particles. Density dependence of quark mass is obtained from NJL self consistent model. NJL model is a effective manner for justify the chiral symmetry. Applying the Gibbs conditions the equation of state of the quarks and hadrons mixed phase is obtained. Since the hadronic matter is under the influence of strong force of nucleons, we calculate the equation of state of this phase using a powerful variational many-body technique. Finally, we calculate the mass and radius of a cold neutron star with a quark core by numerically solving the TOV equation. To check our used EOS, we compare our results with the recent observational data. Our results are in a good agreement with some observed compact objects such as $S A X J 1748.9 - 2021$ , $4 U 1608 - 52$ and $V e l a X - 1$ .
nucl-thastro-ph.HEhep-phIran.J.Sci.Technol.A(2019)·8 citations
02
Magnetic field in nuclear collisions at ultra high energies
V. A. Okorokov (National Research Nuclear University MEPhI)🇷🇺
The magnetic field created in proton-proton and nucleus-nucleus collisions at ultra high energies are studied with models of point-like charges and hard sphere for distribution of the constituents for vacuum conditions. The various beam ions are considered from light to heavy nuclei at energies corresponded to the nominal energies of proton beam within the projects of further accelerator facilities high-energy Large Hadron Collider (HE-LHC) and Future Circular Collider (FCC). The magnetic field strength immediately after collisions reaches the value tens of GeV $^{2}$ while the approach with point-like charges some overestimate the amplitude of the field in comparison with more realistic hard sphere model. The absolute value of magnetic field rapidly decrease with time and increases with growth of atomic number. The amplitude for $e B$ is estimated at level $100$ GeV $^{2}$ in order to magnitude for quark-quark collisions at energies corresponded to the nominal energies of proton beams. These estimations are close to the range for onset of $W$ boson condensation.
nucl-thMDPI Physics(2019)·4 citations
03
The possibility of $^{14}$ C cluster as a building block of medium mass nuclei
N. Itagaki · A. V. Afanasjev · D. Ray
The possibility of the $^{14}$ C cluster being a basic building block of medium mass nuclei is discussed. Although $α$ cluster structures have been widely discussed in the light $N \approx Z$ mass region, the neutron to proton ratio deviates from unity in the nuclei near $β$ -stability line and in neutron-rich nuclei. Thus, more neutron-rich objects with $N > Z$ could become the building blocks of cluster structures in such nuclei. The $^{14}$ C nucleus is strongly bound and can be regarded as such a candidate. In addition, the path to the lowest shell-model configuration at short relative distances is closed for the $^{14}$ C+ $^{14}$ C structure contrary to the case of the $^{12}$ C+ $^{12}$ C structure; this allows to keep appreciable separation distance between the $^{14}$ C clusters. The recent development of antisymmetrized quasi-cluster model (AQCM) allows us to utilize $j j$ -coupling shell model wave function for each cluster in a simplified way. The AQCM results for the $^{14}$ C+ $^{14}$ C structure in $^{28}$ Mg are compared with the ones of cranked relativistic mean field (CRMF) calculations. Although theoretical frameworks of these two models are quite different, they give similar results for the nucleonic densities and rotational properties of the structure under investigation. The existence of linear chain three $^{14}$ C cluster structure in $^{42}$ Ar has also been predicted in AQCM. These results confirm the role of the $^{14}$ C cluster as a possible building block of cluster structures in medium mass nuclei.
nucl-thnucl-exPRC(2020)·18 citations
04
An update on fine-tunings in the triple-alpha process
Timo A. Lähde🇩🇪 · Ulf-G. Meißner🇩🇪 · Evgeny Epelbaum🇩🇪
The triple-alpha process, whereby evolved stars create carbon and oxygen, is believed to be fine-tuned to a high degree. Such fine-tuning is suggested by the unusually strong temperature dependence of the triple-alpha reaction rate at stellar temperatures. This sensitivity is due to the resonant character of the triple-alpha process, which proceeds through the so-called "Hoyle state" of $^{12}$ C with spin-parity $0^{+}$ . The question of fine-tuning can be studied within the {\it ab initio} framework of nuclear lattice effective field theory, which makes it possible to relate {\it ad hoc} changes in the energy of the Hoyle state to changes in the fundamental parameters of the nuclear Hamiltonian, which are the light quark mass $m_{q}$ and the electromagnetic fine-structure constant. Here, we update the effective field theory calculation of the sensitivity of the triple-alpha process to small changes in the fundamental parameters. In particular, we consider recent high-precision lattice QCD calculations of the nucleon axial coupling $g_{A}$ , as well as new and more comprehensive results from stellar simulations of the production of carbon and oxygen. While the updated stellar simulations allow for much larger {\it ad hoc} shifts in the Hoyle state energy than previously thought, recent lattice QCD results for the nucleon S-wave singlet and triplet scattering lengths now disfavor the scenario of no fine-tuning in the light quark mass $m_{q}$ .
nucl-thastro-ph.SRhep-phhep-thEPJA(2020)·19 citations
05
EoS from terrestrial experiments: static and dynamic polarizations of nuclear density
H. Sagawa · S. Yoshida · Li-Gang Cao
We critically examine nuclear matter and neutron matter equation of state (EoS) parameters by using best available terrestrial experimental results. The nuclear incompression modulus $K_{\infty}$ is re-examined in comparisons with RPA results of modern relativistic and non-relativistic EDF and up-to-date experimental data of isoscalar giant monopole resonance energy of $^{208}$ Pb. The symmetry energy expansion coefficients $J$ , $L$ and $K_{sy m}$ are examined by recent FRDM mass model and the neutron skin of $^{48}$ Ca extracted from $(p, p^{'})$ experiments.
nucl-thAIP Conf.Proc.(2019)·7 citations
06
Shell model results for $^{47 - 58}$ Ca isotopes in the $f p$ , $f p g_{9/2}$ and $f p g_{9/2} d_{5/2}$ model spaces
Bharti Bhoy · Praveen C. Srivastava · Kazunari Kaneko
We have reported shell-model results for $^{47 - 58}$ Ca isotopes in the $f p$ , $f p g_{9/2}$ and $f p g_{9/2} d_{5/2}$ model spaces using realistic $N N$ interaction. We have also performed a systematic shell-model study using interactions derived from in-medium similarity-renormalization group (IM-SRG) targeted for a particular nucleus with chiral $N N$ and $3 N$ forces. The results obtained are in a reasonable agreement with the available experimental data in $f p$ model space with $N N$ interaction. It is shown that the $g_{9/2}$ and $d_{5/2}$ orbitals play an important role for heavier neutron-rich $^{54 - 58}$ Ca isotopes, while it is marginal for $^{47 - 52}$ Ca. We have also examined spectroscopic factor strengths using $N N$ and $N N + 3 N$ interactions for recently available experimental data.
nucl-thnucl-exJ.Phys.G(2020)·12 citations
07
Sound velocity in dense stellar matter with strangeness and compact stars
Chengjun Xia🇨🇳 · Zhenyu Zhu🇨🇳 · Xia Zhou🇨🇳 · Ang Li🇨🇳
The phase state of dense matter in the intermediate density range ( $\sim$ 1-10 times the nuclear saturation density) is both intriguing and unclear and could have important observable effects in the present gravitational wave era of neutron stars. As the matter density increases in compact stars, the sound velocity is expected to approach the conformal limit ( $c_{s} / c = 1/ 3$ ) at high densities and should also fulfill the causality limit ( $c_{s} / c < 1$ ). However, its detailed behavior remains a hot topic of debate. It was suggested that the sound velocity of dense matter could be an important indicator for a deconfinement phase transition, where a particular shape might be expected for its density dependence. In this work, we explore the general properties of the sound velocity and the adiabatic index of dense matter in hybrid stars, as well as in neutron stars and quark stars. Various conditions are employed for hadron-quark phase transition with varying interface tension. We find that the expected behavior of the sound velocity can also be achieved by the nonperturbative properties of the quark phase, in addition to a deconfinement phase transition. And it leads to a more compact star with a similar mass. We then propose a new class of quark star equation of states, which could be tested by future high-precision radius measurements of pulsar-like objects.
nucl-thastro-ph.HEastro-ph.SRhep-phCPC(2021)·58 citations
08
Turning the nuclear energy density functional method into a proper effective field theory: reflections
R.J. Furnstahl🇺🇸
Nuclear energy density functionals (EDFs) have a long history of success in reproducing properties of nuclei across the table of the nuclides. They capture quantitatively the emergent features of bound nuclei, such as nuclear saturation and pairing, yet greater accuracy and improved uncertainty quantification are actively sought. Implementations of phenomenological EDFs are suggestive of effective field theory (EFT) formulations and there are hints of an underlying power counting. Multiple paths are possible in trying to turn the nuclear EDF method into a proper EFT. I comment on the current situation and speculate on how to proceed using an effective action formulation.
nucl-thEPJA(2020)·43 citations
09
Mapping the Phases of Quantum Chromodynamics with Beam Energy Scan
Adam Bzdak🇵🇱 · ShinIchi Esumi🇯🇵 · Volker Koch🇺🇸 · Jinfeng Liao🇺🇸 · Mikhail Stephanov🇺🇸 · Nu Xu🇺🇸
We review the present status of the search for a phase transition and critical point as well as anomalous transport phenomena in Quantum Chromodynamics (QCD), with an emphasis on the Beam Energy Scan program at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. We present the conceptual framework and discuss the observables deemed most sensitive to a phase transition, QCD critical point, and anomalous transport, focusing on fluctuation and correlation measurements. Selected experimental results for these observables together with those characterizing the global properties of the systems created in heavy ion collisions are presented. We then discuss what can be already learned from the currently available data about the QCD critical point and anomalous transport as well as what additional measurements and theoretical developments are needed in order to discover these phenomena.
nucl-thhep-lathep-phnucl-exPhys.Rept.(2020)·616 citations
10
Limiting fragmentation as an initial state probe in heavy ion collisions
Kayman J. Gonçalves🇧🇷 · Andre V. Giannini🇯🇵 · David D. Chinellato🇧🇷 · Giorgio Torrieri🇧🇷
We discuss limiting fragmentation within a few currently popular phenomenological models. We show that popular Glauber-inspired models of particle production in heavy ion collisions, such as the two-component model, generally fail to reproduce limiting fragmentation when all energies and system sizes experimentally available are considered. This is due to the energy-dependence of number of participants and number of collisions. We quantify this violation in terms of the model parameters. We also make the same calculation within a Color Glass Condensate scenario and show that the dependence of the saturation scale on the number of participants generally leads to violation of limiting fragmentation. We further argue that wounded parton models, provided the nucleon size and parton density vary predominantly with Bjorken $x$ , could in principle reproduce both multiplicity dependence with energy and limiting fragmentation. We suggest, therefore, that an experimental measurement of deviation from limiting fragmentation in heavy ion collisions, for different system sizes and including the experimentally available range of energies, is a powerful test of initial state models.
nucl-thhep-phPRC(2019)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE