Nuclear Theory·nucl-th

Friday·December 24, 2021

11 papers—5 primary·6 cross-listed

01
Resonant tunneling of deuteron-triton fusion in strong high-frequency electromagnetic fields
Binbing Wu · Hao Duan · Jie Liu
We investigate deuteron-triton (DT) fusion in the presence of linearly polarized strong electromagnetic fields in high-frequency limit, in which a complex spherical square-well potential is exploited to describe the nuclear potential. Within the framework of the Kramers-Henneberger (KH) transformation, we have calculated the total and angular differential fusion cross sections by investigating the asymptotical phase shifts of the Coulomb wavefunctions. With introducing a dimensionless quantity of $n_{d}$ representing the ratio of the particle quiver oscillation amplitude to the radius of nuclear potential, we find that, even though the tunneling probability of passing through the Coulomb repulsive potential keeps almost identical to that in the absence of electromagnetic fields, the peak of total fusion sections shows an apparent shift from the well known value of 110 keV to 78 keV for $n_{d} = 0.01$ . The angular differential cross sections also show some resonance peaks that shift from zero inclination angle to $π /2$ with increasing the parameter $n_{d}$ . The corresponding astrophysical $S$ -factors are found to be enhanced by several times in amplitudes. With the help of Wentzel-Kramers-Brillouin (WKB) approximate wavefunctions, the shape-resonance tunneling mechanism of the above findings are uncovered and some implications are discussed.
nucl-thPRC(2022)·11 citations
02
Electrical conductivity of the quark-gluon plasma from the low energy limit of photon and dilepton spectra
Stefan Floerchinger🇩🇪 · Charlotte Gebhardt🇩🇪 · Klaus Reygers🇩🇪
Fluid dynamic considerations are used to determine the electric current spectral density in the regime of small energies and momenta. The spectral density in this regime is parameterized by the electric conductivity, the charge susceptibility, and the relaxation time for the electric current, which is needed for relativistic causality. Experimentally, the spectral function can be accessed through the production rates of photons and dileptons in the expanding quark-gluon plasma. We use fluid dynamic simulations of high energy nuclear collisions, together with the transport limit of the spectral density, to obtain photon and dielectron spectra for different values of the conductivity and relaxation times. The yields of photon and dileptons produced in the plasma are compared to the background from decays of short-lived hadrons. We discuss how experiments can constrain the electrical conductivity and associated relaxation time of the quark-gluon plasma.
nucl-thhep-phnucl-exPLB(2023)·18 citations
03
Bose-Einstein condensation in finite drops of alpha particles
L. M. Satarov · I. N. Mishustin · H. Stoecker
Ground-state properties of finite drops of alpha particles (Q-balls) are studied within a field-theoretical approach in the mean-field approximation. The strong interaction of alphas is described by the scalar field with a sextic Skyrme-like potential. The radial profiles of scalar- and Coulomb fields are found by solving the coupled system of Klein-Gordon and Poisson equations. The formation of shell-like nuclei, with vanishing density around the center, is predicted at high enough attractive strength of Skyrme potential. The equilibrium values of energy and baryon number of Q-balls and Q-shells are calculated for different sets of interaction parameters. Empirical binding energies of alpha-conjugate nuclei are reproduced only if the gradient term in the Lagrangian is strongly enhanced. It is demonstrated that this enhancement can be explained by a finite size of alpha particles.
nucl-thPRC(2022)·3 citations
04
Artificial Intelligence Supported Shell-Model Calculations for Light Sn Isotopes
Serkan Akkoyun · Abderrahmane Yakhelef
The region around the doubly magic nuclide $^{100} S n$ is very interesting for nuclear physics studies in terms of structure, reaction and nuclear astrophysics. The main ingredients in nuclear structure studies using the shell model are the single-particle energies and the two-body matrix elements. To obtain the former, experimental data of $^{101} S n$ isotope spectrum are necessary. Since there is not enough experimental data, different approaches are used in the literature to obtain single-particle energies. In sn100pn interaction, the hole excitation spectrum was used in $^{131} S n$ to determine neutron single-particle energies. The other approach is the use of the lightest isotope, $^{107} S n$ , which figures the model space orbitals. In this study, we estimated the spectrum of the $^{101} S n$ isotope by artificial neural network method in order to obtain neutron single-particle energies. After the training was carried out by using the experimental spectra of the nuclei around $^{100} S n$ isotope, the $^{101} S n$ spectrum was obtained. Subsequently, neutron SPEs of the model space orbitals are defined. Shell model calculations for $^{102 - 108} S n$ isotopes are carried out and results are compared to the experimental data and results obtained using the widely used interaction in the region, sn100pn. According to the results, it is seen that the Sn isotope spectra obtained with the new SPE values are more compatible with the experimental data.
nucl-thPRC(2022)·2 citations
05
Angular Power Spectrum and Elliptic Flow from Event Maps in Heavy Ion Collisions
Hannah Anderson🇺🇸 · Shengquan Tuo🇺🇸
Azimuthal and polar angle distributions of particles produced in heavy ion collisions carry important information about the early state of the system and the evolution of the Quark Gluon Plasma. The pixelization code HEALPix was created by the Jet Propulsion Laboratory to analyze the cosmic microwave background. As has been shown using public data from the ALICE experiment, its two-dimensional representation of a sphere containing pixels of equal area has a broader application to heavy ion collisions. The angular power spectrum, an application of HEALPix, is directly related to the particle flow and is calculated through the angles theta and phi on the sphere. The elliptic flow is calculated from simulated AMPT events and publicly available CMS data. We show that HEALPix can be used to detect the presence of elliptic flow for lead-lead collisions and thus has broader applications in the study of QGP in heavy ion collisions.
nucl-th0 citations
06
Dense and Hot QCD at Strong Coupling
Tuna Demircik🇰🇷 · Christian Ecker🇩🇪 · Matti Järvinen🇰🇷
We present a novel framework for the equation of state of dense and hot Quantum Chromodynamics (QCD), which focuses on the region of the phase diagram relevant for neutron star mergers and core-collapse supernovae. The model combines predictions from the gauge/gravity duality with input from lattice field theory, QCD perturbation theory, chiral effective theory and statistical modeling. It is therefore, by construction, in good agreement with theoretical constraints both at low and high densities and temperatures. The main ingredients of our setup are the non-perturbative V-QCD model based on the gauge/gravity duality, a van der Waals model for nucleon liquid, and the DD2 version of the Hempel-Schaffner-Bielich statistical model of nuclear matter. By consistently combining these models, we also obtain a description for the nuclear to quark matter phase transition and its critical endpoint. The parameter dependence of the model is represented by three (soft, intermediate and stiff) variants of the equation of state, all of which agree with observational constraints from neutron stars and their mergers. We discuss resulting constraints for the equation of state, predictions for neutron stars and the location of the critical point.
↳ hep-phastro-ph.HEgr-qchep-th+1PRX(2022)·66 citations
07
Angular Momentum Eigenstates of the Isotropic 3-D Harmonic Oscillator: Phase-Space Distributions and Coalescence Probabilities
Michael Kordell II🇺🇸 · Rainer J. Fries🇺🇸 · Che Ming Ko🇺🇸
The isotropic 3-dimensional harmonic oscillator potential can serve as an approximate description of many systems in atomic, solid state, nuclear, and particle physics. In particular, the question of 2 particles binding (or coalescing) into angular momentum eigenstates in such a potential has interesting applications. We compute the probabilities for coalescence of two distinguishable, non-relativistic particles into such a bound state, where the initial particles are represented by generic wave packets of given average positions and momenta. We use a phase-space formulation and hence need the Wigner distribution functions of angular momentum eigenstates in isotropic 3-dimensional harmonic oscillators. These distribution functions have been discussed in the literature before but we utilize an alternative approach to obtain these functions. Along the way, we derive a general formula that expands angular momentum eigenstates in terms of products of 1-dimensional harmonic oscillator eigenstates.
↳ quant-phnucl-thAnnals Phys.(2022)·12 citations
08
Radiative (anti)neutrino energy spectra from muon, pion, and kaon decays
Oleksandr Tomalak🇺🇸
To describe low-energy (anti)neutrino fluxes in modern coherent elastic neutrino-nucleus scattering experiments as well as high-energy fluxes in precision-frontier projects such as the Enhanced NeUtrino BEams from kaon Tagging (ENUBET) and the Neutrinos from STORed Muons (nuSTORM), we evaluate (anti)neutrino energy spectra from radiative muon ( $μ^{-} \to e^{-} ν ˉ_{e} ν_{μ} (γ), μ^{+} \to e^{+} ν_{e} ν ˉ_{μ} (γ)$ ), pion $π_{ℓ 2}$ ( $π^{-} \to μ^{-} ν ˉ_{μ} (γ), π^{+} \to μ^{+} ν_{μ} (γ)$ ), and kaon $K_{ℓ 2}$ ( $K^{-} \to μ^{-} ν ˉ_{μ} (γ), K^{+} \to μ^{+} ν_{μ} (γ)$ ) decays. We compare detailed $O (α)$ distributions to the well-known tree-level results, investigate electron-mass corrections and provide energy spectra in analytical form. Radiative corrections introduce continuous and divergent spectral components near the endpoint, on top of the monochromatic tree-level meson-decay spectra, which can change the flux-averaged cross section at $6 \times 1 0^{- 5}$ level for the scattering on $^{40} Ar$ nucleus with (anti)neutrinos from the pion decay at rest. Radiative effects modify the expected (anti)neutrino fluxes from the muon decay around the peak region by $3 - 4$ permille, which is a precision goal for next-generation artificial neutrino sources.
↳ hep-phhep-exnucl-exnucl-thPLB(2022)·16 citations
09
Influence of the nuclear symmetry energy slope on observables of compact stars with $Δ$ -admixed hypernuclear matter
Vivek Baruah Thapa🇮🇳 · Monika Sinha🇮🇳
In this work, we study the effects of nuclear symmetry energy slope on neutron star dense matter equation of state and its impact on neutron star observables (mass-radius, tidal response). We construct the equation of state within the framework of covariant density functional theory implementing coupling schemes of non-linear and density-dependent models with viability of heavier non-nucleonic degrees of freedom. The slope of symmetry energy parameter ( $L_{sym}$ ) is adjusted following density-dependence of isovector meson coupling to baryons. We find that smaller values of $L_{sym}$ at saturation favour early appearance of $Δ$ -resonances in comparison to hyperons leading to latter's threshold at higher matter densities. We also investigate the dependence of $L_{sym}$ on tidal deformability and compactness parameter of a $1.4 M_{⊙}$ neutron star for different equation of states and observe similar converging behaviour for larger $L_{sym}$ values.
↳ astro-ph.HEnucl-thPRC(2022)·11 citations
10
Classical and Quantum Evolution in a Simple Coherent Neutrino Problem
Joshua D. Martin🇺🇸 · A. Roggero🇺🇸 · Huaiyu Duan🇺🇸 · J. Carlson🇺🇸 · V. Cirigliano🇺🇸
The extraordinary neutrino flux produced in extreme astrophysical environments like the early universe, core-collapse supernovae and neutron star mergers may produce coherent quantum neutrino oscillations on macroscopic length scales. The Hamiltonian describing this evolution can be mapped into quantum spin models with all-to-all couplings arising from neutrino-neutrino forward scattering. To date many studies of these oscillations have been performed in a mean-field limit where the neutrinos time evolve in a product state. In this paper we examine a simple two-beam model evolving from an initial product state and compare the mean-field and many-body evolution. The symmetries in this model allow us to solve the real-time evolution for the quantum many-body system for hundreds or thousands of spins, far beyond what would be possible in a more general case with an exponential number ( $2^{N}$ ) of quantum states. We compare mean-field and many-body solutions for different initial product states and ratios of one- and two-body couplings, and find that in all cases in the limit of infinite spins the mean-field (product state) and many-body solutions coincide for simple observables. This agreement can be understood as a consequence of the fact that the typical initial condition represents a very local but dense distribution about a mean energy in the spectrum of the Hamiltonian. We explore quantum information measures like entanglement entropy and purity of the many-body solutions, finding intriguing relationships between the quantum information measures and the dynamical behavior of simple physical observables.
↳ hep-phastro-ph.HEnucl-thPRD(2022)·47 citations
11
Long-time tails in the SYK chain from the effective field theory with a large number of derivatives
Navid Abbasi🇨🇳
We study the nonlinear energy diffusion through the SYK chain in the framework of Schwinger-Keldysh effective field theory. We analytically construct the interacting effective Lagrangian up to $4 0^{t h}$ order in the derivative expansion. According to this effective Lagrangian, we calculate the first order loop correction of the energy density response function, the pole of which is the dispersion relation of energy diffusion. As expected, we see that the standard derivative expansion of that dispersion relation, $ω = - i D_{(1)} k^{2} - i D_{(2)} k^{4} + O (k^{6})$ , breaks down due to the long-time tails. However, we find that the nonlinear contribution of order $n$ to the self-energy is proportional to $(k^{2})^{n + 1/2}$ . This suggests to modify the dispersion relation by splitting it into two dispersion relations and double the number of transport coefficients at any order as $ω = - i k^{2} (D_{(1, 1)} \pm i D_{(1, 2)} (k^{2})^{1/2}) - i k^{4} (D_{(2, 1)} \pm i D_{(2, 2)} (k^{2})^{1/2}) + O (k^{6})$ . We find that the modified series, which include the effect of long-time tails, are convergent. The radius of convergence is proportional to the ratio of thermal conductivity to diffusion constant.
↳ hep-thcond-mat.str-elnucl-thJHEP(2022)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE