Nuclear Theory·nucl-th

Wednesday·October 27, 2021

11 papers—6 primary·5 cross-listed

01
Predictions and postdictions for relativistic lead and oxygen collisions with Trajectum
Govert Nijs🇺🇸 · Wilke van der Schee🇨🇭
We introduce a global analysis of relativistic heavy ion collisions using Trajectum of a significantly higher precision and including a new option to vary the normalization of the centrality estimator. We use the posterior distribution of our parameters to generate a set of high statistics samples that allows us to make precise predictions including statistical and systematic uncertainties estimated from the model parameter distribution. The results are systematically compared with experiment whereby we also include many observables not included in the global analysis. This includes in particular (extremely) ultracentral anisotropic flow and mean transverse momentum, whereby we find satisfactory agreement with experiment where data is available. Lastly, we compute spectra and anisotropic flow for oxygen-oxygen collisions performed at RHIC and to be performed at the LHC and comment on how these collisions may inform us on properties of the Quark-Gluon-Plasma.
nucl-thhep-phnucl-exPRC(2022)·79 citations
02
Intermittency analysis in relativistic heavy-ion collisions
Zhiming Li🇨🇳 · Jin Wu🇨🇳
Local density fluctuations near the QCD critical point can be probed by an intermittency analysis of power-law behavior on scaled factorial moments in relativistic heavy-ion collisions. We study the second-order scaled factorial moment in Au + Au collisions at $s_{NN}$ = 7.7-200 GeV from the UrQMD model. Since the background subtraction and efficiency correction are two important aspects in this measurement, we propose a cumulative variable method to remove background contribution and a cell-by-cell method for efficiency correction in the intermittency analysis.
nucl-thnucl-exSciPost Phys.Proc.(2022)·0 citations
03
Shell-model study for GT-strengths corresponding to $β$ decay of $^{60}$ Ge and $^{62}$ Ge
Vikas Kumar · Anil Kumar · Praveen C. Srivastava
In the present work, we have reported a comprehensive shell-model study of GT-strengths for recently available experimental data for $^{60}$ Ga and $^{62}$ Ga from RIKEN Nishina Center [Phys. Rev. C 103, 014324 (2021)] populated by $β$ decay of the $^{60}$ Ge and $^{62}$ Ge, respectively. We have performed shell-model calculations in two different model spaces, the first set of calculations in the $f p$ model space using KB3G and GXPF1A interactions, while the second set in $f_{5/2} p g_{9/2}$ model space using JUN45 and jj44b effective interactions. Our shell-model results in $f p$ model space are in a reasonable agreement with the available experimental data.
nucl-thnucl-exNPA(2022)·7 citations
04
Vorticity and $Λ$ polarization in the microscopic transport model PACIAE
Anke Lei🇨🇳 · Dujuan Wang🇨🇳 · Dai-Mei zhou🇨🇳 · Ben-Hao Sa🇨🇳 · Laszlo Pal Csernai🇩🇪
We study the behavior of four types of vorticities in non-central Au+Au collisions at energies $S_{N N}$ = 5--200 GeV using a microscopic transport model PACIAE. The results show that the vorticities decay faster at lower energy and smaller impact parameter. The non-monotonic dependence of the initial vorticities on the collision energies is reconfirmed and the turning point is 10-15 GeV for different vorticities. The global $Λ$ polarization at energies $S_{N N}$ = 7.7--200 GeV is reproduced by introducing an energy density freeze-out criterion.
nucl-thhep-phPRC(2021)·24 citations
05
Comment on Effective-range function methods for charged particle collisions
Orlov Yu. V
The authors of a recent paper [Phys. Rev. C 97(2018) 044003] (Ref. [1]), D. Gaspard and J.-M. Sparenberg, attempt to consider an alternative method for the asymptotic normalization coefficients (ANC) calculating which differs from so-called approximate \Delta method proposed earlier [Phys. Rev. C 96(2017) 034601] (Ref. [2]) by O.L. Ramírez Suárez, and J. M. Sparenberg. The abstract in Ref. [1], in essence, declares that the approximation used in Ref. [2], where a \Delta_l function is introduced to fit the Coulomb-nuclear phase shifts {\delta}_l^{(cs)} at low energies, is not correct, since this \Delta_l function is not analytical at zero energy. In my view, this statement is erroneous. I believe that the origin of this mistake in Ref. [1] is due to adopting the re-normalized scattering amplitude form designed for resonant states, which is not valid for a bound state. It is shown in the fundamental work [Nucl. Phys. B 60 (1973) 443] Ref.[3] by Hamilton et al. that an effective-range function (ERF) K_l(k^2) is a meromorphic in the physical sheet except for the poles of bound states on the imaginary positive axis of the momentum complex plane. In my paper [Nucl. Phys A, 1010 (2021) 122174] Ref. [4], a strict form of the re-normalized scattering amplitude is derived, which can be used for the analytical continuation to a bound state pole. It is found in Ref. 4 that the \Delta_l function has analytical properties similar to those of the K_l(k^2) function. Thus, both functions have no singularities at zero energy.
nucl-th0 citations
06
Neutron Stars and Gravitational Waves: the Key Role of Nuclear Equation of State
P.S. Koliogiannis · A. Kanakis-Pegios · Ch.C. Moustakidis
Neutron stars are the densest known objects in the universe and an ideal laboratory for the strange physics of super-condensed matter. Theoretical studies in connection with recent observational data of isolated neutron stars, as well as binary neutron stars systems, offer an excellent opportunity to provide robust solutions on the dense nuclear problem. In the present work, we review recent studies concerning the applications of various theoretical nuclear models on a few recent observations of binary neutron stars or neutron-star--black-hole systems. In particular, using a simple and well-established model, we parametrize the stiffness of the equation of state with the help of the speed of sound. Moreover, in comparison to the recent observations of two events by LIGO/VIRGO collaboration, GW170817 and GW190425, we suggest possible robust constraints. We also concentrate our theoretical study on the resent observation of a compact object with mass~ $\sim 2.5 9_{- 0.09}^{+ 0.08} M_{⊙}$ (GW190814 event), as a component of a system where the main companion was a black hole with mass $\sim 23 M_{⊙}$ . There is scientific debate concerning the identification of the low mass component, as it falls into the neutron-star--black-hole mass gap. This is an important issue since understanding the nature of GW190814 event will offer rich information concerning the upper limit of the speed of sound in dense matter and the possible phase transition into other degrees of freedom. We systematically study the tidal deformability of a possible high-mass candidate existing as an individual star or as a component in a binary neutron star system. Finally, we provide some applications of equations of state of hot, dense nuclear matter in hot neutron stars, protoneutron stars, and binary neutron star merger remnants.
nucl-thastro-ph.HEFoundations(2021)·13 citations
07
Hadron Production in terms of Green's Functions in Non-Equilibrium Matter
A.V.Koshelkin🇷🇺
Following the quark-hadron duality concept, we show that the number of hadrons generated in the deconfinement matter is entirely determined by the exact non-equilibrium Green's functions of partons in the medium and the vertex function governing the probability of the confinement-deconfinement phase transition. In such an approach, compactifying the standard (3+1) chromodynamics into $QC D_{x y} + QC D_{z t}$ , the rate of the hadrons produced in particle collisions is derived in the explicit form provided that the hadronization is the first order phase transition. The pion production is found to be in good agreement to the experimental results on the pion yield in pp collisions.
↳ hep-phhep-thnucl-thSciPost Phys.Proc.(2022)·0 citations
08
QCD viscosity by combining the gradient flow and sparse modeling methods
Etsuko Itou🇯🇵 · Yuki Nagai🇯🇵
We give a new description to obtain the shear viscosity in QCD at finite temperature. Firstly, we obtain the correlation function of the renormalized energy-momentum tensor using the gradient flow method. Secondly, we estimate the spectral function from the smeared correlation functions using the sparse modeling method. The combination of these two methods looks promising to determine the shear viscosity precisely.
↳ hep-lathep-phnucl-thPoS(2022)·4 citations
09
Machine learning spectral functions in lattice QCD
S.-Y. Chen🇨🇳 · H.-T. Ding🇨🇳 · F.-Y. Liu🇨🇳 · G. Papp🇭🇺 · C.-B. Yang🇨🇳
We study the inverse problem of reconstructing spectral functions from Euclidean correlation functions via machine learning. We propose a novel neural network, SVAE, which is based on the variational autoencoder (VAE) and can be naturally applied to the inverse problem. The prominent feature of the SVAE is that a Shannon-Jaynes entropy term having the ground truth values of spectral functions as prior information is included in the loss function to be minimized. We train the network with general spectral functions produced from a Gaussian mixture model. As a test, we use correlators generated from four different types of physically motivated spectral functions made of one resonance peak, a continuum term and perturbative spectral function obtained using non-relativistic QCD. From the mock data test we find that the SVAE in most cases is comparable to the maximum entropy method (MEM) in the quality of reconstructing spectral functions and even outperforms the MEM in the case where the spectral function has sharp peaks with insufficient number of data points in the correlator. By applying to temporal correlation functions of charmonium in the pseudoscalar channel obtained in the quenched lattice QCD at 0.75 $T_{c}$ on $12 8^{3} \times 96$ lattices and $1.5$ $T_{c}$ on $12 8^{3} \times 48$ lattices, we find that the resonance peak of $η_{c}$ extracted from both the SVAE and MEM has a substantial dependence on the number of points in the temporal direction ( $N_{τ}$ ) adopted in the lattice simulation and $N_{τ}$ larger than 48 is needed to resolve the fate of $η_{c}$ at 1.5 $T_{c}$ .
↳ hep-latcs.LGhep-phhep-th+134 citations
10
The Impact of the New $^{65}$ As(p, $γ$ ) $^{66}$ Se Reaction Rate on the Two-Proton Sequential Capture of $^{64}$ Ge, Weak GeAs Cycles, and Type-I X-Ray Bursts such as the Clocked Burster GS 1826 $-$ 24
Yi Hua Lam · Zi Xin Liu · Alexander Heger · Ning Lu · Adam Michael Jacobs · Zac Johnston
We re-assess $^{65}$ As(p, $γ$ ) $^{66}$ Se reaction rates based on a set of proton thresholds of $^{66}$ Se, $S_{p}$ ( $^{66}$ Se), estimated from the experimental mirror nuclear masses, theoretical mirror displacement energies, and full $p f$ -model space shell-model calculation. The self-consistent relativistic Hartree-Bogoliubov theory is employed to obtain the mirror displacement energies with much reduced uncertainty, and thus reducing the proton-threshold uncertainty up to 161 keV compared to the AME2020 evaluation. Using the simulation instantiated by the one-dimensional multi-zone hydrodynamic code, KEPLER, that closely reproduces the observed GS 1826 $-$ 24 clocked bursts, the present forward and reverse $^{65}$ As(p, $γ$ ) $^{66}$ Se reaction rates based on a selected $S_{p}$ ( $^{66}$ Se) = 2.469 $\pm$ 0.054 MeV, and the latest $^{22}$ Mg( $α$ ,p) $^{25}$ Al, $^{56}$ Ni(p, $γ$ ) $^{57}$ Cu(p, $γ$ ) $^{58}$ Zn, $^{55}$ Ni(p, $γ$ ) $^{56}$ Cu, and $^{64}$ Ge(p, $γ$ ) $^{65}$ As reaction rates, we find that though the GeAs cycles is weakly established in the rapid-proton capture process path, the $^{65}$ As(p, $γ$ ) $^{66}$ Se reaction still strongly characterizes the burst tail end due to the two-proton sequential capture on $^{64}$ Ge, not found by Cyburt et al. (2016) sensitivity study. The $^{65}$ As(p, $γ$ ) $^{66}$ Se reaction influences the abundances of nuclei $A$ = 64, 68, 72, 76, and 80 up to a factor of 1.4. The new $S_{p}$ ( $^{66}$ Se) and the inclusion of the updated $^{22}$ Mg( $α$ ,p) $^{25}$ Al reaction rate increases the production of $^{12}$ C up to a factor of $4.5$ that is not observable and could be the main fuel for superburst. The waiting point status of and two-proton sequential capture on $^{64}$ Ge, weak-cycle feature of GeAs at region heavier than $^{64}$ Ge, and impact of other possible $S_{p}$ ( $^{66}$ Se) are also discussed.
↳ astro-ph.HEnucl-exnucl-thApJ(2022)·17 citations
11
Deep Learning Exotic Hadrons
JPAC Collaboration: L. Ng🇺🇸 · L. Bibrzycki🇵🇱 · J. Nys🇨🇭 · C. Fernandez-Ramirez🇲🇽 · A. Pilloni🇮🇹 · V. Mathieu🇪🇸 · A.J. Rasmusson🇺🇸 · A.P. Szczepaniak🇺🇸
We perform the first model independent analysis of experimental data using Deep Neural Networks to determine the nature of an exotic hadron. Specifically, we study the line shape of the $P_{c} (4312)$ signal reported by the LHCb collaboration and we find that its most likely interpretation is that of a virtual state. This method can be applied to other near-threshold resonance candidates.
↳ hep-phhep-exnucl-thPRD(2022)·30 citations

Affiliations

first authorsco-authorsvia INSPIRE