Nuclear Theory·nucl-th

Monday·November 28, 2022

22 papers—12 primary·10 cross-listed

01
Supersolidity of $α$ cluster structure in $^{40}$ Ca
S. Ohkubo
$α$ cluster structure in nuclei has been long understood based on the geometrical configuration picture. By using the spatially localized Brink $α$ cluster model in the generator coordinate method, it is shown that the $α$ cluster structure has the apparently opposing duality of crystallinity and condensation, a property of supersolids. To study the condensation aspects of the $α$ cluster structure a field theoretical superfluid cluster model (SCM) is introduced, in which the order parameter of condensation is incorporated by treating rigorously the Nambu-Goldstone mode due to spontaneous symmetry breaking of the global phase. The $α$ cluster structure of $^{40}$ Ca, which has been understood in the crystallinity picture, is studied by the SCM with ten $α$ clusters. It is found that the $α$ cluster structure of $^{40}$ Ca is reproduced by the SCM in addition to $^{12}$ C reported in a previous paper, which gives support to the duality of the $α$ cluster structure. The emergence of the mysterious $0^{+}$ state at the lowest excitation energy near the $α$ threshold energy is understood to be a manifestation of the Nambu-Goldstone zero mode, a soft mode, due to the condensation aspect of the duality similar to the Hoyle state in $^{12}$ C. The duality of $α$ cluster structure with incompatible crystallinity and coherent wave nature due to condensation is the consequence of the Pauli principle, which causes clustering.
nucl-thPRC(2022)·2 citations
02
Stability of the manifold boundary approximation method for reductions of nuclear structure models
M. Imbrišak · K. Nomura
The framework of nuclear energy density functionals has been employed to describe nuclear structure phenomena for a wide range of nuclei. Recently, statistical properties of a given nuclear model, such as parameter confidence intervals and correlations, have received much attention, particularly when one tries to fit complex models. We apply information-theoretic methods to investigate stability of model reductions by the manifold boundary approximation method (MBAM). In an illustrative example of the density-dependent point-coupling model of the relativistic energy density functional, utilizing Monte Carlo simulations, it is found that main conclusions obtained from the MBAM procedure are stable under variation of the model parameters. Furthermore, we find that the end of the geodesic occurs when the determinant of the Fisher information metric vanishes, thus effectively separating the parameter space into two disconnected regions.
nucl-thPRC(2023)·2 citations
03
Employing ternary fission of $^{242}$ Pu as a probe of very neutron rich matter
J.B. Natowitz · H. Pais · G. Röpke
Detailed assessments of the ability of recent theoretical approaches to modeling existing experimental data for ternary fission confirm earlier indications that the dominant mode of cluster formation in ternary fission is clusterization in very neutron rich, very low density, essentially chemically equilibrated, nucleonic matter. An extended study and comparison of these approaches applied to ternary fission yields in the thermal neutron induced reaction $^{241}$ Pu( $n_{th}$ ,f) has been undertaken to refine the characterization of the source matter. The resonance gas approximation has been improved taking in-medium effects on the binding energies into account. A temperature of 1.29 MeV, density of $6.7 \times 1 0^{- 5}$ nucleons/fm $^{3}$ and proton fraction $Y_{p}$ = 0.035 are found to provide a good representation of yields of the ternary emitted light particles and clusters. In particular, results for $Z = 1$ and 2 isotopes are presented. Isotopes with larger $Z$ are discussed, and the roles of medium and continuum effects, even at very low density are illustrated.
nucl-thPRC(2023)·10 citations
04
Jet radius and momentum splitting fraction with dynamical grooming in heavy-ion collisions
Lei Wang🇨🇳 · Jin-Wen Kang🇨🇳 · Qing Zhang🇨🇳 · Shuwan Shen🇨🇳 · Wei Dai🇨🇳 · Ben-Wei Zhang🇨🇳 · Enke Wang🇨🇳
We investigate the medium modifications of momentum splitting fraction and groomed jet radius with both dynamical grooming and soft drop algorithms in heavy-ion collisions. In the calculation, the partonic spectrum of initial hard scattering in p+p collisions is provided by the event generator PYTHIA 8, and the energy loss of fast parton traversing in a hot/dense QCD medium is simulated with the Linear Boltzmann Transport (LBT) model. We predict the normalized distributions of the groomed jet radius $θ_{g}$ and momentum splitting fraction $z_{g}$ with the dynamical grooming algorithm in Pb+Pb collisions at $s_{NN}$ = 5.02 TeV, then compare these quantities in dynamical grooming at $a = 0.1$ , with that in soft drop at $z_{cut} = 0.1$ and $β = 0$ . It is found that the normalized distribution ratios Pb+Pb/p+p with respect to $z_{g}$ in $z_{cut} = 0.1$ , $β = 0$ soft drop case are close to unity and those in $a = 0.1$ dynamical grooming case show enhancement at small $z_{g}$ , and Pb+Pb/p+p with respect to $θ_{g}$ in the dynamical grooming case demonstrate weaker modification than those in the soft drop counterparts. We further calculate the groomed jet number averaged momentum splitting fraction $⟨ z_{g} ⟩_{jets}$ and averaged groomed jet radius $⟨ θ_{g} ⟩_{jets}$ in p+p and A+A for both grooming cases in three $p_{T}^{ch, jet}$ intervals, and find that the originally generated well balanced groomed jets will become more momentum imbalanced and less jet size narrowing due to jet quenching, and weaker medium modification of $z_{g}$ and $θ_{g}$ in $a = 0.1$ dynamical grooming case than in the soft drop counterparts.
nucl-thhep-phChin.Phys.Lett.(2023)·14 citations
05
$(I, J^{P}) = (1, 1/ 2^{+})$ $Σ N N$ quasibound state
H. Garcilazo🇲🇽 · A. Valcarce🇪🇸
JLab has recently found indications of the possible existence of a $Σ N N$ resonance at $(3.14 \pm 0.84) - i (2.28 \pm 1.2)$ MeV. In the past, using models that exploit symmetries between the two-baryon sector with and without strangeness, hyperon-nucleon interactions have been derived that reproduce the experimental data of the strangeness $- 1$ sector. We make use of these interactions to review existing Faddeev studies of the $Λ N N$ - $Σ N N$ system that show theoretical evidences about a $(I, J^{P}) = (1, 1/ 2^{+})$ $Σ N N$ quasibound state near threshold. The calculated position of the pole is at 2.92 $- i$ 2.17 MeV, in reasonable agreement with the experimental findings.
nucl-thhep-phSymmetry(2022)·8 citations
06
Deep-neural-network approach to solving the ab initio nuclear structure problem
Yilong Yang · Pengwei Zhao
Predicting the structure of quantum many-body systems from the first principles of quantum mechanics is a common challenge in physics, chemistry, and material science. Deep machine learning has proven to be a powerful tool for solving condensed matter and chemistry problems, while for atomic nuclei it is still quite challenging because of the complicated nucleon-nucleon interactions, which strongly couple the spatial, spin, and isospin degrees of freedom. By combining essential physics of the nuclear wave functions and the strong expressive power of artificial neural networks, we develop FeynmanNet, a deep-learning variational quantum Monte Carlo approach for \emph{ab initio} nuclear structure. We show that FeynmanNet can provide very accurate solutions of ground-state energies and wave functions for $^{4}$ He, $^{6}$ Li, and even up to $^{16}$ O as emerging from the leading-order and next-to-leading-order Hamiltonians of pionless effective field theory. Compared to the conventional diffusion Monte Carlo approaches, which suffer from the severe inherent fermion-sign problem, FeynmanNet reaches such a high accuracy in a variational way and scales polynomially with the number of nucleons. Therefore, it paves the way to a highly accurate and efficient \emph{ab initio} method for predicting nuclear properties based on the realistic interactions between nucleons.
nucl-thcond-mat.dis-nnquant-phPRC(2023)·44 citations
07
Do short range correlations inhibit the appearance of the nuclear pasta?
Mateus R. Pelicer🇧🇷 · Débora P. Menezes🇧🇷 · Mariana Dutra🇧🇷 · Odilon Lourenço🇧🇷
It is well known that strongly correlated neutron-proton pairs, the short-range correlations (SRC), can modify many of the nuclear properties. In this work we have introduced, for the first time, short range correlations in the calculation of the nuclear pasta phase at zero temperature and checked how they affect its size and internal structure. We have used two different parameterizations of relativistic models in a mean field approximation and the coexistence phase approximation as a first estimation of the effects. We have seen that for very asymmetric neutron-proton-electon matter, the pasta phase shrinks considerably as compared with the results without SRC and all internal structures vanish, except the simple spherically symmetric one, the droplets. Our results indicate a possible disappearance of these complicated structures as the temperature increases.
nucl-thastro-ph.HEEPJA(2023)·5 citations
08
Microscopic description of $α$ , $2 α$ , and cluster decays of $^{216 - 220}$ Rn and $^{220 - 224}$ Ra
J. Zhao🇨🇳 · J.-P. Ebran🇫🇷 · L. Heitz🇫🇷 · E. Khan🇫🇷 · F. Mercier🇫🇷 · T. Niksic🇭🇷 · D. Vretenar🇭🇷
Alpha and cluster decays are analyzed for heavy nuclei located above $^{208}$ Pb on the chart of nuclides: $^{216 - 220}$ Rn and $^{220 - 224}$ Ra, that are also candidates for observing the $2 α$ decay mode. A microscopic theoretical approach based on relativistic Energy Density Functionals (EDF), is used to compute axially-symmetric deformation energy surfaces as functions of quadrupole, octupole and hexadecupole collective coordinates. Dynamical least-action paths for specific decay modes are calculated on the corresponding potential energy surfaces. The effective collective inertia is determined using the perturbative cranking approximation, and zero-point and rotational energy corrections are included in the model. The predicted half-lives for $α$ -decay are within one order of magnitude of the experimental values. In the case of single $α$ emission, the nuclei considered in the present study exhibit least-action paths that differ significantly up to the scission point. The differences in alpha-decay lifetimes are not only driven by Q values, but also by variances of the least-action paths prior to scission. In contrast, the $2 α$ decay mode presents very similar paths from equilibrium to scission, and the differences in lifetimes are mainly driven by the corresponding Q values. The predicted $^{14}$ C cluster decay half-lives are within three orders of magnitudes of the empirical values, and point to a much more complex pattern compared to the alpha-decay mode.
nucl-thPRC(2023)·20 citations
09
Studying the process $γ d \to π^{0} η d$
A. Martinez Torres🇧🇷 · K. P. Khemchandani🇧🇷 · E. Oset🇪🇸
In these proceedings we present our recent results on the study of the process $γ d \to π^{0} η d$ , where the existence of a dibaryon in the $η d$ invariant mass distribution has been recently claimed. As we will show, many of the relevant aspects observed in the experiment, as the shift of the $η d$ and $π d$ invariant mass distributions with respect to phase space can be described with our model, where no dibaryon is formed. Instead, we consider the interaction of the $γ$ with the nucleons forming the deuteron to proceed through $γ N \to Δ (1700) \to η Δ (1232) \to η π^{0} N$ , followed by the rescattering of the $π$ and $η$ with the other nucleon of the deuteron. Theoretical uncertainties related to different parameterizations of the deuteron wave function are investigated
nucl-thhep-phActa Phys.Polon.A(2022)·1 citation
10
Exotic properties of N^*(1895) and its impact on photoproduction of light hyperons
K. P. Khemchandani🇧🇷 · A. Martinez Torres🇧🇷 · Sang-Ho Kim🇰🇷 · Seung-il Nam🇰🇷 · A. Hosaka🇯🇵
In this work, we outline the findings of our recent study of the properties of $N^{*} (1895)$ and its consequential impacts on the cross sections of the photoproduction of $Λ (1405)$ . Further, we discuss the possibility of the existence of an isovector state, with the mass similar to $Λ (1405)$ , which we refer to as $Σ (1400)$ . With the idea of motivating experimental investigations of $Σ (1400)$ , we have studied its photoproduction process and determined the respective cross sections and polarization observables. We have studied also the coupling of $N^{*} (1895)$ to $K Σ (1400)$ and found that it gives an important contribution to the cross sections near the threshold. In the process, we have determined the branching ratios of the decay of $N^{*} (1895)$ , to the final states involving $Λ (1405)$ and $Σ (1400)$ , to be in the range of 6-7 MeV. Our findings can motivate consideration of alternative processes in partial wave analyses of experimental data, when studying the properties of $N^{*} (1895)$ .
nucl-thActa Phys.Polon.A(2022)·2 citations
11
Density-Induced Hadron-Quark Crossover via the Formation of Cooper Triples
Hiroyuki Tajima🇯🇵 · Shoichiro Tsutsui🇯🇵 · Takahiro M. Doi🇯🇵 · Kei Iida🇯🇵
We discuss the hadron--quark crossover accompanied by the formation of Cooper triples (three-body counterpart of Cooper pairs) by analogy with the Bose--Einstein condensate to Bardeen--Cooper--Schrieffer crossover in two-component fermionic systems. Such a crossover is different from a phase transition, which often involves symmetry breaking. We calculate the in-medium three-body energy from the three-body $T$ -matrix with a phenomenological three-body force characterizing a bound hadronic state in vacuum. With increasing density, the hadronic bound-state pole smoothly undergoes a crossover toward the Cooper triple phase where the in-medium three-body clusters coexist with the quark Fermi sea. The relation to the quarkyonic matter model can also be found in a natural manner.
nucl-thastro-ph.HEcond-mat.quant-gashep-phSymmetry(2023)·7 citations
12
Towards microscopic optical potentials in deformed nuclei
Andrea Idini · Jimmy Rotureau · Johan Boström · Jimmy Ljungberg · B. Gillis Carlsson
A microscopic and consistent description of both nuclear structure and reactions is instrumental to extend the predictivity of models calculating scattering observables. In particular, this is crucial in the case of exotic nuclei not yet discovered. In this manuscript, we will present the plan of the Lund effort for a symmetry breaking description of bound and scattering observables using a generator coordinate method model based on an effective Hamiltonian constrained with a (Skyrme) functional. Following this, we will illustrate the steps to construct an optical potential for deformed nuclei from microscopic wavefunctions obtained with projected generator coordinate method from Hartree-Fock-Bogoliubov basis.
nucl-thJ.Phys.Conf.Ser.(2023)·4 citations
13
A study of the relativistic corrections to polarized tritium $β$ -decay
Gianluca Cavoto🇮🇹 · Angelo Esposito🇮🇹 · Guglielmo Papiri🇮🇹 · Antonio Davide Polosa🇮🇹
Forthcoming experiments like Project8 and Ptolemy aim at investigating with high precision the end-point of the tritium $β$ -decay spectrum sensitive to the neutrino mass. In light of this, using the standard parametrization in terms of nuclear polar form factors, we analyze the complete relativistic expression for the spectrum of the $β$ -electron emitted by a tritium nucleus. Given the small parameters in the problem, we systematically discuss the approximations that can be made, and present the first two corrections to the standard lowest order formula. We particularly discuss the case of an initially polarized target, and the consequences on the spectrum as a function of the neutrino mass. We show that, while it induces an angular anisotropy that can be measured by future experiments, such anisotropy cannot be used as an additional handle to constrain the neutrino mass.
↳ hep-phnucl-thPRC(2023)·3 citations
14
Entropy Suppression through Quantum Interference in Electric Pulses
Gerald V. Dunne🇺🇸 · Adrien Florio🇺🇸 · Dmitri E. Kharzeev🇺🇸
The Schwinger process in strong electric fields creates particles and antiparticles that are entangled. The entropy of entanglement between particles and antiparticles has been found to be equal to the statistical Gibbs entropy of the produced system. Here we study the effect of quantum interference in sequences of electric pulses, and show that quantum interference suppresses the entanglement entropy of the created quantum state. This is potentially relevant to quantum-enhanced classical communications. Our results can be extended to a wide variety of two-level quantum systems.
↳ hep-phhep-thnucl-thquant-phPRD(2023)·8 citations
15
Dynamical fermions, centre vortices, and emergent phenomena
Derek Leinweber🇦🇺 · James Biddle🇦🇺 · Waseem Kamleh🇦🇺 · Adam Virgili (CSSM, University of Adelaide)🇦🇺
The non-trivial ground-state vacuum fields of QCD form the foundation of matter. Here we examine the centre vortices identified within the ground-state fields of lattice QCD. We aim to understand the manner in which dynamical fermions in the QCD vacuum alter the centre-vortex structure. Using modern visualisation techniques, the centre-vortex structure of pure-gauge and dynamical-fermion fields is quantified and compared. We then explore the impact this modified structure has on measures of confinement and dynamical mass generation. The string tension of the static quark potential, positivity-violation in the gluon propagator, and dynamical mass generation in the overlap quark propagator are of particular interest. The impact of dynamical fermions is significant and provides new insights into the role of centre vortices in underpinning both confinement and dynamical chiral symmetry breaking in QCD.
↳ hep-lathep-phnucl-thEPJ Web Conf.(2022)·6 citations
16
Sea-quark loop contributions to the $d ˉ$ - $u ˉ$ asymmetry in the proton
Derek B. Leinweber🇦🇺 · Anthony W. Thomas (CSSM, University of Adelaide)🇦🇺
QCD interactions for equal-mass fermion flavors are flavor blind. This fact is often used to state that disconnected sea-quark loop contributions are equal for $u$ and $d$ quarks in the mass symmetric case and therefore these disconnected sea-quark loop contributions cannot contribute to the well-known $d ˉ - u ˉ$ asymmetry in the proton. Instead, it is argued that one must look to the connected sector of lattice QCD correlation functions to find this difference. In this presentation, we note that these statements are true provided unphysical contributions in the sea-quark loop sector are included, contributions from baryons that do not appear in the physical spectrum. To respect the Pauli principle, these unphysical contributions from the disconnected sea-quark loop sector must cancel equally unphysical contributions in the connected sector. The remaining disconnected sea-quark loop contributions no longer have a balance between $d ˉ$ and $u ˉ$ . Upon considering only physically observed baryons in the loop contributions, we illustrate an important contribution from the sea-quark loop sector to $d ˉ - u ˉ$ that enhances the leading connected contribution by 12\%.
↳ hep-phhep-latnucl-thPRD(2024)·4 citations
17
Measurement of hadron masses in 2-color finite density QCD
Kotaro Murakami🇯🇵 · Daiki Suenaga🇯🇵 · Kei Iida🇯🇵 · Etsuko Itou🇯🇵
We investigate hadron spectra in 2-color QCD using lattice simulation with $N_{f} = 2$ at low temperature and finite density in which there appears not only the hadronic phase but also the superfluid phase. We first calculate the pion and rho meson spectrum, which is well-known from previous works. The spectral ordering of these mesons flips around the quark chemical potential $μ = m_{π}^{0} /2$ ( $m_{π}^{0}$ : the pion mass at $μ = 0$ ), where the phase transition between the hadronic and superfluid phases occurs. For $μ ≳ m_{π}^{0} /2$ , the effective mass for the pion linearly increases while the one for the rho meson monotonically decreases. Furthermore, we measure hadron spectra with the isospin $I = 0$ and the angular momentum $J^{P} = 0^{\pm}$ . The effective masses for the meson, diquark, and antidiquark with the same quantum number become degenerate just below $μ = m_{π}^{0} /2$ , and the three hadrons have the same mass in the superfluid phase. It suggests that mixing occurs between spectra associating with mesons and baryons due to the $U (1)_{B}$ symmetry breaking. This phenomenon can be explained in the linear sigma model with the approximate $S U (4)$ Pauli-Gursey symmetry.
↳ hep-lathep-phnucl-thPoS(2023)·18 citations
18
Transverse momentum decorrelation of the flow vector in Pb-Pb collisions at $s_{NN}$ = 5.02 TeV
Emil Gorm Nielsen🇩🇰 · You Zhou🇩🇰
The individual studies of the anisotropic flow vector, flow angle and flow magnitude fluctuations with multi-particle correlations provide insight into the initial conditions and properties of the quark-gluon plasma (QGP) created in high-energy heavy-ion collisions. Recent measurements of these fluctuations have been available and the comparison to hydrodynamic models shows unique sensitivities to the initial conditions of the system, but also a puzzling dependence on the specific shear viscosity $η / s$ . In this paper, a systematic study with A Multi-Phase Transport (AMPT) model using different tunings of the initial conditions, partonic cross section and hadronic interactions investigates the $p_{T}$ -dependent flow vector, flow angle and flow magnitude fluctuations. It is found that the transport model reasonably describes the flow vector, flow angle and flow magnitude fluctuations observed in data and that the fluctuations are driven by fluctuations in the initial state. The comparison of data and model presented in this paper enables further constraints on the initial conditions of the heavy-ion collisions.
↳ nucl-exnucl-thEPJC(2023)·12 citations
19
Helicity conservation in perfect electromagnetic and chiral fluids
Cristina Manuel🇪🇸 · Juan M. Torres-Rincon🇪🇸
We derive the total helicity conservation law for a perfect electromagnetic relativistic fluid. As the conservation equation contains the derivative of the magnetic helicity, it can be reshaped as having the same form as the chiral anomaly equation if the fluid is isentropic. We also take the non-relativistic limit of the helicity conservation law, and check the agreement with the Abanov-Wiegmann equation at zero temperature, but we provide further corrections in the more general case. We then consider chiral fluids, when the chiral anomaly equation has to be incorporated in the hydrodynamical equations, together with other chiral transport effects which exist in the presence of a chiral imbalance. We finally study how the chiral imbalance modifies the helicity conservation law.
↳ hep-phhep-thnucl-thPRD(2023)·4 citations
20
Hadrons at high temperature: an update from the FASTSUM collaboration
Jon-Ivar Skullerud🇮🇪 · Gert Aarts🇬🇧 · Chris Allton🇬🇧 · M. Naeem Anwar🇬🇧 · Ryan Bignell🇬🇧 · Tim Burns🇬🇧 · Sergio Chaves García-Mascaraque🇬🇧 · Simon Hands🇬🇧 · Rachel Horohan D'Arcy🇮🇪 · Benjamin Jäger🇩🇰 · Seyong Kim🇰🇷 · Maria Paola Lombardo🇮🇹 and 7 other authors
We present the most recent results from the FASTSUM collaboration for hadron properties at high temperature. This includes the temperature dependence of the light and charmed meson and baryon spectrum, as well as properties of heavy quarkonia. The results are obtained using anisotropic lattices with a fixed scale approach. We also present the status of our next generation gauge ensembles.
↳ hep-lathep-phnucl-thEPJ Web Conf.(2022)·7 citations
21
Inverse Problem Approach for Non-Perturbative QCD: Theoretical Foundation
Ao-Sheng Xiong🇨🇳 · Fu-Sheng Yu🇨🇳 · Yong Zheng🇨🇳 · Ting Wei🇨🇳
A novel theoretical framework, the inverse problem approach, is proposed to calculate non-perturbative quantities in quantum chromodynamics (QCD). Based on the dispersion relation of quantum field theory, this approach determines unknown low-energy non-perturbative quantities from known high-energy perturbative inputs via solving an inverse problem. The resulting inverse problem is rigorously proven to be ill-posed, with the solutions being unique but unstable. To address this instability, the well-established Tikhonov regularization is employed, yielding stable approximate solutions that converge to the true values as input errors vanish. The key features of this approach are illustrated through three toy models, demonstrating that solution precision can be systematically improved through reduced input errors and optimized regularization strategies.
↳ hep-thhep-exhep-lathep-ph+121 citations
22
Hidden-flavor pentaquarks
H. Garcilazo🇲🇽 · A. Valcarce🇪🇸
We have recently studied hidden-charm pentaquarks, $c c ˉ q q q$ , using dynamical correlations between the heavy quarks arising from the Coulomb-like nature of the short-range interaction. A pattern was obtained that compares well with the experimental data. We extend our description to other flavor sectors which can be framed within the same type of structures discussed in the original paper. A detailed comparison is made with other results in the literature and with experimental data. Predictions will be a useful tool to discriminate between different models of multiquark system dynamics.
↳ hep-phnucl-thPRD(2022)·9 citations

Affiliations

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