Nuclear Theory·nucl-th

Tuesday·August 11, 2020

22 papers—9 primary·13 cross-listed

01
Unveiling the correlations of tidal deformability with the nuclear symmetry energy parameters
Tuhin Malik · B. K. Agrawal · Constança Providência · J. N. De
The chi-squared based covariance approach allows one to estimate the correlations among desired observables related to nuclear matter directly from a set of fit data without taking recourse to the distributions of the nuclear matter parameters (NMPs). Such an approach is applied to study the correlations of tidal deformability of neutron star with the slope and the curvature parameters of nuclear symmetry energy governed by an extensive set of fit data on the finite nuclei together with the maximum mass of the neutron star. The knowledge of the distributions of NMPs consistent with the fit data is implicitly inbuilt in the Hessian matrix which is central to this covariance approach. Comparing our results with those obtained with the explicit use of the distributions of NMPs, we show that the appropriate correlations among NMPs as induced by the fit data are instrumental in strengthening the correlations of the tidal deformability with the symmetry energy parameters, without it, the said correlations tend to disappear. The interplay between isoscalar and isovector NMPs is also emphasized.
nucl-thastro-ph.HEgr-qcPRC(2020)·28 citations
02
Direct photon emission and influence of dynamical wave packets in an extended quantum molecular dynamics model
C.Z. Shi · Y. G. Ma · X. G. Cao · D. Q. Fang · W. B. He · C. Zhong
Direct photon produced from first proton-neutron ( $p$ - $n$ ) collision during the early stage of heavy ion reaction is a sensitive probe to reflect energy and momentum distribution of nucleons. In this work, we embedded the hard photon production channel in an extended quantum molecular dynamics (EQMD) model, and took the direct photon as a possible probe to improve namely the Fermi motion in the EQMD model. A possible scheme is offered to handle the dynamical wave packet width within incoherent bremsstrahlung process. Direct photons calculated by our modified EQMD were compared with data of $^{14}$ N + $^{12}$ C at beam energies $E / A$ = 20, 30 and 40 MeV, and it is found that the yield, inverse slope and angular distribution of direct photons could be reasonably reproduced. In addition, asymmetric reaction systems of $^{4}$ He + C and $^{4}$ He + Zn at $E / A$ = 53 MeV are also simulated in this work. It is found that the symmetric angular distribution in the nucleon-nucleon ( $N$ - $N$ ) center-of-mass (c.m.) frame and the velocity of $t h e γ$ -emission source can be reasonably obtained from our method although there is some quantitative differences.
nucl-thnucl-exPRC(2020)·11 citations
03
Screening of nucleon electric dipole moments in atomic systems
Kota Yanase🇯🇵
The electric dipole moments (EDMs) of diamagnetic atoms are expected to be sensitive to charge-parity violation particularly in nuclei through the nuclear Schiff moment. I explicitly demonstrate that the well-known form of the Schiff moment operator originating from the nucleon EDM is obtained by considering the screening of the nucleon EDMs in a neutral atom. Consequently, an additional contribution to the Schiff moment arises from the screening of the nuclear EDM induced by the interaction of the nucleon EDMs with the protons. This correction to the Schiff moment of $^{199}$ Hg is evaluated in the independent particle model.
nucl-thPRC(2021)·13 citations
04
The comparative role of 7Li(n,{\gamma}) reaction in primordial nucleosynthesis
N.A. Burkova🇰🇿 · S.B. Dubovichenko🇰🇿 · A.V. Dzhazairov-Kakhramanov🇰🇿 · S.Zh. Nurakhmetova🇰🇿
Within the framework of the modified potential cluster model with forbidden states and their classification according to Young diagrams, the possibility of describing experimental data on the total cross sections of the neutron radiative capture on 7Li is considered. It is shown that the model used and the methods for constructing potentials make it possible to correctly describe the behavior of experimental cross sections at energies of 5 meV (5 10-3 eV) to 1 MeV(1 10+6 eV), where experimental data are available. Based on the obtained total cross sections up to 5 MeV, the reaction rate was calculated and its analytical approximation was carried out. It was shown that the 7Li(n,g)8Li reaction dominates at T9 < 0.1-0.2 as against with the burning of 7Li in reactions 7Li(3H,n)9Be and 7Li(4He,g)11B.
nucl-thJ.Phys.G(2021)·2 citations
05
Hadronic effects on charmonium elliptic flows in heavy-ion collisions
Baoyi Chen · Liu Jiang · Yunpeng Liu
Transport and Langevin equations are employed to study hadronic medium effects on charmonium elliptic flows in heavy-ion collisions. In Pb-Pb collisions, the anisotropic energy density of the quark-gluon plasma (QGP) in the transverse plane is transformed into hadron momentum anisotropy after the phase transition. Charmonia with high transverse momentum $p_{T}$ are produced via the primordial hard process and undergo different degrees of dissociation along different paths in the QGP. They then scatter with light hadrons in the hadron phase. Both contributions to the charmonium elliptic flows are studied at moderate and high transverse momenta. The elliptic flows of the prompt $J / ψ$ are found to be considerably enhanced at high transverse momentum when the charmonium diffusion coefficients in the hadronic medium are parametrized through the geometry scale approximation. This hadronic medium effect is negligible for quarkonia with larger mass such as bottomonia.
nucl-thhep-phPRC(2021)·1 citation
06
The non-resonance shake mechanism of the neutrinoless double electronic capture
F.F. Karpeshin🇷🇺 · M.B. Trzhaskovskaya🇷🇺 · L.F. Vitushkin🇷🇺
It is generally accepted that double neutrinoless electron capture is a resonance process. The calculations of the probability of shaking with the ionization of the electron shell occurring during the transformation of 152Gd and 164Er nuclei are performed below. These nuclides have the lowest resonance defect among all known nuclei, being considered as main candidates for discovering the neutrinoless mode of the transformation. The results show predominant contribution of the new mechanism for most of the candidate nuclei. The value of this amendment rapidly increases with an increasing resonance defect. Thus, in principle, double neutrinoless electron capture appears not to be a resonance process at all.
nucl-thPhys.Atom.Nucl.(2020)·9 citations
07
Dynamical spectral structure of density fluctuation near QCD critical point
Md Hasanujjaman🇮🇳 · Golam Sarwar🇮🇳 · Mahfuzur Rahaman🇮🇳 · Abhijit Bhattacharyya🇮🇳 · Jan-e Alam🇮🇳
The expression for the dynamical spectral structure of the density fluctuation near the QCD critical point has been derived using linear response theory within the purview of Israel-Stewart relativistic viscous hydrodynamics. The change in spectral structure of the system as it moves toward critical end point has been studied. The effects of the critical point have been introduced in the system through a realistic equation of state and the scaling behaviour of various transport coefficients and thermodynamic response functions. We have found that the Brillouin and the Rayleigh peaks are distinctly visible when the system is away from critical point but the peaks tend to merge near the critical point. The sensitivity of structure of the spectral function on wave vector ( $k$ ) of the sound wave has been demonstrated. It has been shown that the Brillouin peaks get merged with the Rayleigh peak because of the absorption of sound waves in the vicinity of the critical point.
nucl-thhep-exhep-phEPJA(2021)·8 citations
08
Charge-exchange dipole excitations in deformed nuclei
Kenichi Yoshida
Background: The electric giant-dipole resonance (GDR) is the most established collective vibrational mode of excitation. A charge-exchange analog, however, has been poorly studied in comparison with the spin (magnetic) dipole resonance (SDR). Purpose: I investigate the role of deformation on the charge-exchange dipole excitations and explore the generic features as an isovector mode of excitation. Methods: The nuclear energy-density functional method is employed for calculating the response functions based on the Skyrme--Kohn--Sham--Bogoliubov method and the proton-neuton quasiparticle-random-phase approximation. Results: The deformation splitting into $K = 0$ and $K = \pm 1$ components occurs in the charge-changing channels and is proportional to the magnitude of deformation as is well known for the GDR. For the SDR, however, a simple assertion based on geometry of a nucleus cannot be applied for explaining the vibrational frequencies of each $K$ -component. A qualitative argument on the strength distributions for each component is given based on the non-energy-weighted sum rules taking nuclear deformation into account. The concentration of the electric dipole strengths in low energy and below the giant resonance is found in neutron-rich unstable nuclei. Conclusions: The deformation splitting occurs generically for the charge-exchange dipole excitions as in the neutral channel. The analog pygmy dipole resonance can emerge in deformed neutron-rich nuclei as well as in spherical systems.
nucl-thPRC(2020)·4 citations
09
Quartic cumulant of baryon number in the presence of QCD critical point
D. Mroczek🇺🇸 · J. Noronha-Hostler🇺🇸 · A. R. Nava Acuna🇺🇸 · C. Ratti🇩🇪 · P. Parotto🇺🇸 · M.A. Stephanov🇺🇸
In the context of the ongoing search for the QCD critical point at the Relativistic Heavy-Ion Collider, we study the equation of state near the critical point in the temperature and baryon chemical potential plane. We use the parametric representation introduced in earlier literature, which maps the universal 3D Ising equation of state onto the QCD phase diagram using several non-universal parameters. We focus on the quartic cumulant of the baryon number, or baryon number susceptibility~ $χ_{4}^{B}$ , which can be accessed experimentally via net-proton fluctuation kurtosis measurements. It was originally predicted, through universality arguments based on the {\em leading} singular contribution, that $χ_{4}^{B}$ and net-proton kurtosis should show a specific non-monotonic behavior due to the critical point. In particular, when following the freeze-out curve on the phase diagram by decreasing beam energy, the kurtosis is expected to dip, and then peak, when the beam energy scan passes close to the critical point. We study the effects of the non-universal and thus far unknown parameters of the Ising-to-QCD mapping on the behavior of~ $χ_{4}^{B}$ . We find that, while the peak remains a solid feature, the presence of the critical point does not necessarily cause a dip in $χ_{4}^{B}$ on the freezeout line {\em below} the transition temperature. The critical point contribution to the dip appears only for a narrow set of mapping parameters, when subleading singular terms are sufficiently suppressed.
nucl-thhep-phnucl-exPRC(2021)·53 citations
10
The Wigner-Eckart Theorem for Reducible Symmetric Cartesian Tensor Operators
Antonio O. Bouzas🇲🇽
We explicitly establish a unitary correspondence between spherical irreducible tensor operators and cartesian tensor operators of any rank. That unitary relation is implemented by means of a basis of integer-spin wave functions that constitute simultaneously a basis of the spaces of cartesian and spherical irreducible tensors. As a consequence, we extend the Wigner--Eckart theorem to cartesian irreducible tensor operators of any rank, and to totally symmetric reducible ones. We also discuss the tensorial structure of several standard spherical irreducible tensors such as ordinary, bipolar and tensor spherical harmonics, spin-polarization operators and multipole operators. As an application, we obtain an explicit expression for the derivatives of any order of spherical harmonics in terms of tensor spherical harmonics.
↳ quant-phhep-phnucl-thRept.Math.Phys.(2016)·1 citation
11
MeV Gamma Rays from Fission: A Distinct Signature of Actinide Production in Neutron Star Mergers
Xilu Wang · Nicole Vassh · Trevor Sprouse · Matthew Mumpower · Ramona Vogt · Jorgen Randrup · Rebecca Surman
Neutron star mergers (NSMs) are the first verified sites of rapid neutron capture (r-process) nucleosynthesis, and could emit gamma rays from the radioactive isotopes synthesized in the neutron-rich ejecta. These MeV gamma rays may provide a unique and direct probe of the NSM environment as well as insight into the nature of the r process, just as observed gammas from the 56Ni radioactive decay chain provide a window into supernova nucleosynthesis. In this work, we include the photons from fission processes for the first time in estimates of the MeV gamma-ray signal expected from an NSM event. We consider NSM ejecta compositions with a range of neutron richness and find a dramatic difference in the predicted signal depending on whether or not fissioning nuclei are produced. The difference is most striking at photon energies above ~3.5 MeV and at a relatively late time, several days after the merger event, when the ejecta is optically thin. We estimate that a Galactic NSM could be detectable by a next generation gamma-ray detector such as AMEGO in the MeV range, up to ~10^4 days after the merger, if fissioning nuclei are robustly produced in the event.
↳ astro-ph.HEnucl-thApJL(2020)·37 citations
12
Nuclear fission in intense laser fields
Jintao Qi🇨🇳 · Libin Fu🇨🇳 · Xu Wang🇨🇳
Rapid-advancing intense laser technologies enable the possibility of a direct laser-nucleus coupling. In this paper the effect of intense laser fields on a series of nuclear fission processes, including proton decay, alpha decay, and cluster decay, is theoretically studied with the help of nuclear double folding potentials. The results show that the half-lives of these decay processes can be modified by non-negligible amounts, for example on the order of 0.01 or 0.1 percents in intense laser fields available in the forthcoming years. In addition to numerical results, an approximate analytical formula is derived to connect the laser-induced modification to the decay half-life and the decay energy.
↳ physics.atom-phnucl-thPRC(2020)·24 citations
13
Axial and pseudoscalar form factors from charged current quasielastic neutrino-nucleon scattering
Oleksandr Tomalak🇺🇸
We study the scattering of neutrinos on polarized and unpolarized free nucleons, and also the polarization of recoil particles in these scatters. In contrast to electromagnetic processes, the parity-violating weak interaction gives rise to large spin asymmetries at leading order. Future polarization measurements could provide independent access to the proton axial structure and allow the first extraction of the pseudoscalar form factor from neutrino data without the conventional partially conserved axial current (PCAC) ansatz and assumptions about the pion-pole dominance. The pseudoscalar form factor can be accessed with precise measurements with muon (anti)neutrinos of a few hundreds $MeV$ of energy or with tau (anti)neutrinos. The axial form factor can be extracted from scattering measurements using accelerator neutrinos of all energies.
↳ hep-phhep-exnucl-exnucl-thPRD(2021)·15 citations
14
Exploring the Collective Phenomenon at the Electron-Ion Collider
Yu Shi🇨🇳 · Lei Wang🇨🇳 · Shu-Yi Wei🇮🇹 · Bo-Wen Xiao🇨🇳 · Liang Zheng🇨🇳
Based on rare fluctuations in strong interactions, we argue that there is a strong physical resemblance between the high multiplicity events in photo-nuclear collisions and those in $p A$ collisions, in which interesting long range collective phenomena are discovered. This indicates that the collectivity can also be studied in certain kinematic region of the upcoming Electron-Ion Collider (EIC) where the incoming virtual photon has a sufficiently long lifetime. Using a model in the Color Glass Condensate formalism, we first show that the initial state interactions can explain the recent ATLAS azimuthal correlation results measured in the photo-nuclear collisions, and then we provide quantitative predictions for the long range correlations in $e A$ collisions in the EIC regime. With the unprecedented precision and the ability to change the size of the collisional system, the high luminosity EIC will open a new window to explore the physical mechanism responsible for the collective phenomenon.
↳ hep-phhep-exnucl-exnucl-thPRD(2021)·23 citations
15
Chirality Production with Mass Effects-Schwinger Pair Production and the Axial Ward Identity
Patrick Copinger🇯🇵 · Shi Pu🇨🇳
The anomalous generation of chirality with mass effects via the axial Ward identity and its dependence on the Schwinger mechanism is reviewed, utilizing parity violating homogeneous electromagnetic background fields. The role vacuum asymptotic states play on the interpretation of expectation values is examined. It is discussed that observables calculated with an in-out scattering matrix element predict a scenario under Euclidean equilibrium. A notable ramification of which is a vanishing of the chiral anomaly. In contrast, it is discussed observables calculated under an in-in, or real-time, formalism predict a scenario out-of equilibrium, and capture effects of mean produced particle anti-particle pairs due to the Schwinger mechanism. The out-of equilibrium chiral anomaly is supplemented with exponential quadratic mass suppression as anticipated for the Schwinger mechanism. Similar behavior in and out-of equilibrium is reviewed for applications including the chiral magnetic effect and chiral condensate.
↳ hep-phhep-thnucl-thInt.J.Mod.Phys.A(2020)·23 citations
16
Geometric Quantum Information Structure in Quantum Fields and their Lattice Simulation
Natalie Klco🇺🇸 · Martin J. Savage🇺🇸
An upper limit to distillable entanglement between two disconnected regions of massless non-interacting scalar field theory has an exponential decay defined by a geometric decay constant. When regulated at short distances with a spatial lattice, this entanglement abruptly vanishes beyond a dimensionless separation, defining a negativity sphere. In two spatial dimensions, we determine this geometric decay constant between a pair of disks and the growth of the negativity sphere toward the continuum through a series of lattice calculations. Making the connection to quantum field theories in three-spatial dimensions, assuming such quantum information scales appear also in quantum chromodynamics (QCD), a new relative scale may be present in effective field theories describing the low-energy dynamics of nucleons and nuclei. We highlight potential impacts of the distillable entanglement structure on effective field theories, lattice QCD calculations and future quantum simulations.
↳ quant-phhep-lathep-phnucl-thPRD(2021)·35 citations
17
From Ji to Jaffe-Manohar orbital angular momentum in Lattice QCD using a direct derivative method
M. Engelhardt🇺🇸 · J. R. Green🇨🇭 · N. Hasan🇩🇪 · S. Krieg🇩🇪 · S. Meinel🇺🇸 · J. Negele🇺🇸 · A. Pochinsky🇺🇸 · S. Syritsyn🇺🇸
A Lattice QCD approach to quark orbital angular momentum in the proton based on generalized transverse momentum-dependent parton distributions (GTMDs) is enhanced methodologically by incorporating a direct derivative technique. This improvement removes a significant numerical bias that had been seen to afflict results of a previous study. In particular, the value obtained for Ji quark orbital angular momentum is reconciled with the one obtained independently via Ji's sum rule, validating the GMTD approach. Since GTMDs simultaneously contain information about the quark impact parameter and transverse momentum, they permit a direct evaluation of the cross product of the latter. They are defined through proton matrix elements of a quark bilocal operator containing a Wilson line; the choice in Wilson line path allows one to continuously interpolate from Ji to Jaffe-Manohar quark orbital angular momentum. The latter is seen to be significantly enhanced in magnitude compared to Ji quark orbital angular momentum, confirming previous results.
↳ hep-lathep-phnucl-thPRD(2020)·26 citations
18
Magnetic moments of the octet, decuplet, low-lying charm, and low-lying bottom baryons in a nuclear medium
Kazuo Tsushima🇧🇷
We study the magnetic moments of the octet, decuplet, low-lying charm, and low-lying bottom baryons with nonzero light quarks in symmetric nuclear matter using the quark-meson coupling (QMC) model, which satisfies the constraint for the allowed maximum change (swelling) of the in-medium nucleon size derived from the $y$ -scaling data for $^{3}$ He $(e, e^{'})$ and $^{56}$ Fe $(e, e^{'})$ . The present QMC model also satisfies the expected allowed maximum enhancement of the nucleon magnetic moments in nuclear matter. Moreover, it has been proven that the calculated in-medium to free proton electromagnetic form factor (EMFF) ratios calculated within the QMC model, reproduce well the proton EMFF super ratio extracted from $^{4} He (e, e^{'} p)^{3} H$ at Jefferson Laboratory (JLab). The medium modifications of the magnetic moments are estimated by evaluating the in-medium to free space baryon magnetic moment ratios to compensate the MIT bag deficiency to describe the free space octet baryon magnetic moments, where ratios are often measured directly in experiments even without knowing the absolute values, such as the free and bound proton electromagnetic form factors, as well as the European Muon Collaboration (EMC) effect to extract the structure function $F_{2}$ ratio of the bound to free nucleons by the corresponding cross section ratio. We also present the results calculated with the different current quark mass values for the strange and bottom quarks to see the possible impact. Furthermore, for a practical use, we give the explicit density dependent parametrizations for the vector potentials of the baryons and light- $(u, d)$ quarks, as well as for the effective masses of the baryons treated in this study, and of the mesons, $ω, ρ, K, K^{*}, η, η^{'}, D, D^{*}, B$ , and $B^{*}$ .
↳ hep-phastro-ph.HEhep-exnucl-ex+1PTEP(2022)·34 citations
19
Breakdown of smooth solutions to the Müller-Israel-Stewart equations of relativistic viscous fluids
Marcelo M. Disconzi🇺🇸 · Vu Hoang🇺🇸 · Maria Radosz🇺🇸
We consider equations of Müller-Israel-Stewart type describing a relativistic viscous fluid with bulk viscosity in four-dimensional Minkowski space. We show that there exists a class of smooth initial data that are localized perturbations of constant states for which the corresponding unique solutions to the Cauchy problem break down in finite time. Specifically, we prove that in finite time such solutions develop a singularity or become unphysical in a sense that we make precise. We also show that in general Riemann invariants do not exist in 1+1 dimensions for physically relevant equations of state and viscosity coefficients. Finally, we present a more general version of a result by Y. Guo and A.S. Tahvildar-Zadeh: we prove large-data singularity formation results for perfect fluids under very general assumptions on the equation of state, allowing any value for the fluid sound speed strictly less than the speed of light.
↳ math.APmath-phmath.MPnucl-thLett. Math. Phys. Vol 113, No 3 (2023)·15 citations
20
Color, Flavor, Temperature and Magnetic Field Dependence of QCD Phase Diagram: Magnetic Catalysis and its Inverse
Aftab Ahmad🇵🇰 · Adnan Bashir🇲🇽 · Marco A. Bedolla🇲🇽 · J.J. Cobos-Martínez🇲🇽
We study dynamical chiral symmetry breaking for quarks in the fundamental representation of $S U (N_{c})$ for $N_{f}$ number of light quark flavors. We also investigate the phase diagram of quantum chromodynamics at finite temperature $T$ and/or in the presence of a constant external magnetic field $e B$ . The unified formalism for this analysis is provided by a symmetry-preserving Schwinger-Dyson equations treatment of a vector $\times$ vector contact interaction model which encodes several well-established features of quantum chromodynamics to mimic the latter as closely as possible. Deconfinement and chiral symmetry restoration are triggered above a critical value of $N_{f}$ at $T = 0 = e B$ . On the other hand, increasing temperature itself screens strong interactions, thus ensuring that a smaller value of $N_{f}$ is sufficient to restore chiral symmetry at higher temperatures. We also observe the well-known phenomenon of magnetic catalysis for a strong enough magnetic field. However, we note that if the effective coupling strength of the model decreases as a function of magnetic field, it can trigger inverse magnetic catalysis in a certain window of this functional dependence. Our model allows for the simultaneous onset of dynamical chiral symmetry breaking and confinement for each case. Qualitative as well as quantitative predictions of our simple but effective model are in reasonably satisfactory agreement with lattice results and other reliable and refined predictions based upon intricate continuum studies of quantum chromodynamics.
↳ hep-phnucl-thJ.Phys.G(2021)·16 citations
21
Polarization Rotation of Chiral Fermions in Vortical Fluid
Defu Hou🇨🇳 · Shu Lin🇨🇳
The rotation of polarization occurs for light interacting with chiral materials. It requires the light states with opposite chiralities interact differently with the materials. We demonstrate analogous rotation of polarization also exists for chiral fermions interacting with quantum electrodynamics plasma with vorticity using chiral kinetic theory. We find that the rotation of polarization is perpendicular both to vorticity and fermion momentum. The effect also exists for chiral fermions in quantum chromodynamics plasma with vorticity. It could lead to generation of a vector current when the probe fermions contain momentum anisotropy.
↳ hep-phcond-mat.mes-hallnucl-thPLB(2021)·18 citations
22
A Hybrid Renormalization Scheme for Quasi Light-Front Correlations in Large-Momentum Effective Theory
Xiangdong Ji🇺🇸 · Yizhuang Liu🇨🇳 · Andreas Schäfer🇩🇪 · Wei Wang🇨🇳 · Yi-Bo Yang🇨🇳 · Jian-Hui Zhang🇨🇳 · Yong Zhao🇺🇸
In large-momentum effective theory (LaMET), calculating parton physics starts from calculating coordinate-space- $z$ correlation functions $h ~ (z, a, P^{z})$ in a hadron of momentum $P^{z}$ in lattice QCD. Such correlation functions involve both linear and logarithmic divergences in lattice spacing $a$ , and thus need to be properly renormalized. We introduce a hybrid renormalization procedure to match these lattice correlations to those in the continuum $MS$ scheme, without introducing extra non-perturbative effects at large $z$ . We analyze the effect of $O (Λ_{QCD})$ ambiguity in the Wilson line self-energy subtraction involved in this hybrid scheme. To obtain the momentum-space distributions, we recommend to extrapolate the lattice data to the asymptotic $z$ -region using the generic properties of the coordinate space correlations at moderate and large $P^{z}$ , respectively.
↳ hep-phhep-exhep-latnucl-ex+1NPB(2021)·143 citations

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