Nuclear Theory·nucl-th

Wednesday·July 15, 2020

17 papers—9 primary·8 cross-listed

01
Satisfying the compressibility sum rule in neutron matter
Mateusz Buraczynski · Samuel Martinello · Alexandros Gezerlis
The static-response function of strongly interacting neutron matter contains crucial information on this interacting many-particle system, going beyond ground-state properties. In the present work, we tackle this problem with quantum Monte Carlo (QMC) approaches at several different densities, using both phenomenological forces and (for the first time) chiral effective field theory interactions. We handle finite-size effects via self-consistent energy-density functional (EDF) calculations for 8250 particles in a periodic volume. We combine these QMC and EDF computations in an attempt to produce a model-independent extraction of the static response function. Our results are consistent with the compressibility sum rule, which encapsulates the limiting behavior of the response function starting from the homogeneous equation of state, without using the sum rule as an input constraint. Our predictions on inhomogeneous neutron matter can function as benchmarks for other many-body approaches, thereby shedding light on the physics of neutron-star crusts and neutron-rich nuclei.
nucl-thastro-ph.HEcond-mat.quant-gasPLB(2021)·9 citations
02
Charge radii of exotic neon and magnesium isotopes
S. J. Novario · G. Hagen · G. R. Jansen · T. Papenbrock
We compute the charge radii of even-mass neon and magnesium isotopes from neutron number N = 8 to the dripline. Our calculations are based on nucleon-nucleon and three-nucleon potentials from chiral effective field theory that include delta isobars. These potentials yield an accurate saturation point and symmetry energy of nuclear matter. We use the coupled-cluster method and start from an axially symmetric reference state. Binding energies and two-neutron separation energies largely agree with data and the dripline in neon is accurate. The computed charge radii have an estimated uncertainty of about 2-3% and are accurate for many isotopes where data exist. Finer details such as isotope shifts, however, are not accurately reproduced. Chiral potentials correctly yield the subshell closure at N = 14 and also a decrease in charge radii at N = 8 (observed in neon and predicted for magnesium). They yield a continued increase of charge radii as neutrons are added beyond N = 14 yet underestimate the large increase at N = 20 in magnesium.
nucl-thPRC(2020)·106 citations
03
Proton induced deuteron knockout reaction as a probe of an isoscalar proton-neutron pair in nuclei
Yoshiki Chazono · Kenichi Yoshida · Kazuki Yoshida · Kazuyuki Ogata
The isoscalar $p n$ pair is expected to emerge in nuclei having the similar proton and neutron numbers but there is no clear experimental evidence for it. We aim to clarify the correspondence between the $p n$ pairing strength in many-body calculation and the triple differential cross section (TDX) of proton-induced deuteron knockout ( $p, p d$ ) reaction on $^{16}$ O. The radial wave function of the isoscalar $p n$ pair with respect to the center of $^{16}$ O is calculated with the energy density functional (EDF) approach and is implemented in the distorted wave impulse approximation (DWIA) framework. The $p n$ pairing strength $V_{0}$ in the EDF calculation is varied and the corresponding change in the TDX is investigated. A clear $V_{0}$ dependence of the TDX is found for the $^{16}$ O( $p, p d$ ) $^{14}$ N( $1_{2}^{+}$ ) at $101.3$ MeV. The nuclear distortion is found to make the $V_{0}$ dependence stronger. Because of the clear $V_{0}$ -TDX correspondence, the ( $p, p d$ ) reaction will be a promising probe for the isoscalar $p n$ pair in nuclei. For quantitative discussion, further modification of the description of the reaction process will be necessary.
nucl-thPRC(2021)·5 citations
04
Nucleon localization function in rotating nuclei
Tong Li · Mengzhi Chen · Chunli Zhang · Witold Nazarewicz · Markus Kortelainen
Background: An electron localization function was originally introduced to visualize bond structures in molecules. It became a useful tool to describe electron configurations in atoms, molecules and solids. In nuclear physics, a nucleon localization function (NLF) has been used to characterize clusters in light nuclei, fragment formation in fission and pasta phases in the inner crust of neutron stars. Purpose: We use the NLF to study the nuclear response to fast rotation. Methods: We generalize the NLF to the case of nuclear rotation. The extended expressions involve both time-even and time-odd local densities. Since current density and density gradient contribute to the NLF primarily at the surface, we propose a simpler spatial measure given by the kinetic-energy density. Illustrative calculations for the superdeformed yrast band of $^{152}$ Dy were carried out by using the cranked Skyrme-Hartree-Fock method. We also employed the cranked harmonic-oscillator model to gain insights into patterns revealed by the NLF at high angular momentum. Results: In a deformed rotating nucleus, several NLFs can be introduced, depending on the definition of the spin-quantization axis and self-consistent symmetries of the system. The oscillating pattern of the NLF can be explained by a constructive interference between the kinetic-energy and particle densities. The nodal pattern seen in the NLF along the major axis of a rotating nucleus comes from single-particle orbits with large aligned angular momentum. The variation of the NLF along the minor axis is traced back to deformation-aligned orbits. Conclusions: The NLF allows a simple interpretation of the shell structure evolution in the rotating nucleus in terms of the angular-momentum alignment of individual nucleons. We expect that the NLF will be useful for the characterization of other collective modes and time-dependent processes.
nucl-thPRC(2020)·10 citations
05
From nuclei to neutron stars: simple binding energy computer modelling in the classroom (Part 1)
A. Pastore · A. M. Romero · C. Diget · A. Rios · K. Leech · P. Stokoe
We present a simple activity based on the liquid-drop model which allows secondary school students to explore the uses of mathematical models and gain an intuitive understanding of the concept of binding energy, and in particular the significance of positive binding energy. Using spreadsheets provided as Supplementary Material, students can perform simple manipulations on the different coefficients of the model to understand the role of each of its five terms. Students can use the spreadsheets to determine model parameters by optimising the agreement with real atomic mass data. %This will subsequently be used to predict the limit of existence of the Segré chart and to find the minimum mass of a neutron star. This activity can be used as the starting point of a discussion about theoretical models, their validation when it comes to describing experimental data and their predictive power towards unexplored regimes.
nucl-thphysics.ed-phPhys.Educ.(2021)·2 citations
06
Spinodal instabilities of spin polarized asymmetric nuclear matter
Artur Polls · Isaac Vidana
We analyze the spinodal instabilities of spin polarized asymmetric nuclear matter at zero temperature for several configurations of the neutron and proton spins. The calculations are performed with the Brueckner--Hartree--Fock (BHF) approach using the Argonne V18 nucleon-nucleon potential plus a three-nucleon force of Urbana type. An analytical parametrization of the energy density, which reproduces with good accuracy the BHF results, is employed to determine the spinodal instability region. We find that, independently of the of the orientation of the neutron and proton spins, the spinodal instability region shinks when the system is polarized, being its size smaller smaller when neutron and proton spins are antiparallel than when they are oriented in a parallel way. We find also that the spinodal instability is always dominated by total density fluctuation independently of the degree of polarization of the system, and that restoration of the isospin symmetry in the liquid phase, {\it i.e.,} the so-called isospin distillation or fragmentation effect, becomes less efficient with the polarization of the system.
nucl-thPRC(2020)·1 citation
07
Analysis of the $^{3} He (α, γ)^{7} Be$ and $^{3} H (α, γ)^{7} Li$ astrophysical direct capture reactions in a modified potential-model approach
E.M. Tursunov · S.A. Turakulov · A.S. Kadyrov
Astrophysical $S$ factors and reaction rates of the direct radiative capture processes $^{3} He (α, γ)^{7} Be$ and $^{3} H (α, γ)^{7} Li$ , as well as the primordial abundance of the $^{7} Li$ element, are estimated in the framework of a modified two-body potential model. It is shown that suitable modification of phase-equivalent $α -^{3} He$ potentials in the $d$ waves can improve the description of the astrophysical $S$ factor for the direct $^{3} He (α, γ)^{7} Be$ radiative capture reaction at energies above 0.5 MeV. An estimated $^{7} Li/H$ abundance ratio of $(4.89 \pm 0.18) \times 1 0^{- 10}$ is in very good agreement with the recent measurement of $(5.0 \pm 0.3) \times 1 0^{- 10}$ by the LUNA collaboration.
nucl-thastro-ph.COnucl-exNPA(2021)·15 citations
08
Stable bound states of $N$ 's, $Λ$ 's, and $Ξ$ 's
H. Garcilazo🇲🇽 · A. Valcarce🇪🇸 · J. Vijande🇪🇸
We review our recent work about the stability of strange few-body systems containing $N$ 's, $Λ$ 's, and $Ξ$ 's. We make use of local central Yukawa-type Malfliet-Tjon interactions reproducing the low-energy parameters and phase shifts of the nucleon-nucleon system and the latest updates of the hyperon-nucleon and hyperon-hyperon ESC08c Nijmegen potentials. We solve the three- and four-body bound-state problems by means of Faddeev equations and a generalized Gaussian variational method, respectively. The hypertriton, $Λ n p$ $(I) J^{P} = (1/2) 1/ 2^{+}$ , is bound by 144 keV; the recently discussed $Λ nn$ $(I) J^{P} = (1/2) 1/ 2^{+}$ system is unbound, as well as the $ΛΛ nn$ $(I) J^{P} = (1) 0^{+}$ system, being just above threshold. Our results indicate that the $Ξ N N$ , $ΞΞ N$ and $ΞΞ N N$ systems with maximal isospin might be bound.
nucl-thhep-phRev. Mex. F\'is. 63, 411-422 (2017)·0 citations
09
Insights into nuclear saturation density from parity violating electron scattering
C. J. Horowitz🇺🇸 · J. Piekarewicz🇺🇸 · Brendan Reed🇺🇸
The saturation density of nuclear matter $ρ_{0}$ is a fundamental nuclear physics property that is difficult to predict from fundamental principles. The saturation density is closely related to the interior density of a heavy nucleus, such as $^{208}$ Pb. We use parity violating electron scattering to determine the average interior weak charge and baryon densities in $^{208}$ Pb. This requires not only measuring the weak radius $R_{wk}$ but also determining the surface thickness of the weak charge density $a$ . We obtain $ρ_{0} = 0.150 \pm 0.010$ fm $^{- 3}$ , where the 7\% error has contributions form the PREX error on the weak radius, an assumed 10\% uncertainty in the surface thickness $a$ , and from the extrapolation to infinite nuclear matter. These errors can be improved with the upcoming PREX II results and with a new parity violating electron scattering experiment, at a somewhat higher momentum transfer, to determine $a$ .
nucl-thnucl-exPRC(2020)·56 citations
10
Valence parton distribution of pion from lattice QCD: Approaching continuum
Xiang Gao🇺🇸 · Luchang Jin🇺🇸 · Christos Kallidonis🇺🇸 · Nikhil Karthik🇺🇸 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸 · Charles Shugert🇺🇸 · Sergey Syritsyn🇺🇸 · Yong Zhao🇺🇸
We present a high-statistics lattice QCD determination of the valence parton distribution function (PDF) of the pion, with a mass of 300 MeV, using two very fine lattice spacings of $a = 0.06$ fm and 0.04 fm. We reconstruct the $x$ -dependent PDF, as well as infer the first few even moments of the PDF using leading-twist 1-loop perturbative matching framework. Our analyses use both RI-MOM and ratio-based schemes to renormalize the equal-time bi-local quark-bilinear matrix elements of pions boosted up to 2.4 GeV momenta. We use various model-independent and model-dependent analyses to infer the large- $x$ behavior of the valence PDF. We also present technical studies on lattice spacing and higher-twist corrections present in the boosted pion matrix elements.
↳ hep-lathep-exhep-phnucl-ex+1PRD(2020)·124 citations
11
Why is LaMET an effective field theory for partonic structure?
Xiangdong Ji🇺🇸
Partons are effective degrees of freedom describing the structure of hadrons involved in high-energy collisions. Familiar theories of partons are QCD light-front quantization and soft-collinear effective theory, both of which are intrinsically Minkowskian and appear unsuitable for classical Monte Carlo simulations. A ``new'' form of the parton theory has been formulated in term of the old-fashioned, Feynman's infinite momentum frame, in which the parton degrees of freedom are filtered through infinite-momentum external states. The partonic structure of hadrons is then related to the matrix elements of static (equal-time) correlators in the state $∣ P^{z} = \infty ⟩$ . This representation lays the foundation of large-momentum effective theory (LaMET) which approximates parton physics through a systematic $M / P^{z}$ expansion of the lattice QCD matrix elements at a finite but large momentum $P^{z}$ , and removes the residual logarithmic- $P^{z}$ dependence by the standard effective-field-theory matching and running.
↳ hep-phhep-lathep-thnucl-thAAPPS Bull.(2020)·23 citations
12
Hyperfine structure of $^{173} Yb^{+}$ : toward resolving the $^{173} Yb$ nuclear octupole moment puzzle
Di Xiao · Jiguang Li · Wesley C. Campbell · Thomas Dellaert · Patrick McMillin · Anthony Ransford · Conrad Roman · Andrei Derevianko
Hyperfine structure (HFS) of atomic energy levels arises due to interactions of atomic electrons with a hierarchy of nuclear multipole moments, including magnetic dipole, electric quadrupole and higher rank moments. Recently, a determination of the magnetic octupole moment of the $^{173} Yb$ nucleus was reported from HFS measurements in neutral $^{173} Yb$ [PRA 87, 012512 (2013)], and is four orders of magnitude larger than the nuclear theory prediction. Considering this substantial discrepancy between the spectroscopically extracted value and nuclear theory, here we propose to use an alternative system to resolve this tension, a singly charged ion of the same $^{173} Yb$ isotope. Utilizing the substantial suite of tools developed around $Yb^{+}$ for quantum information applications, we propose to extract nuclear octupole and hexadecapole moments from measuring hyperfine splittings in the extremely long lived first excited state ( $4 f^{13} (^{2} F^{o}) 6 s^{2}$ , $J = 7/2$ ) of $^{173} Yb^{+}$ . We present results of atomic structure calculations in support of the proposed measurements.
↳ physics.atom-phnucl-thPRA(2020)·10 citations
13
Hydrodynamization in systems with detailed transverse profiles
Aleksi Kurkela🇨🇭 · Seyed Farid Taghavi🇩🇪 · Urs Achim Wiedemann🇨🇭 · Bin Wu🇨🇭
The observation of fluid-like behavior in nucleus-nucleus, proton-nucleus and high-multiplicity proton-proton collisions motivates systematic studies of how different measurements approach their fluid-dynamic limit. We have developed numerical methods to solve the ultra-relativistic Boltzmann equation for systems of arbitrary size and transverse geometry. Here, we apply these techniques for the first time to the study of azimuthal flow coefficients $v_{n}$ including non-linear mode-mode coupling and to an initial condition with realistic event-by-event fluctuations. We show how both linear and non-linear response coefficients extracted from $v_{n}$ develop as a function of opacity from free streaming to perfect fluidity. We note in particular that away from the fluid-dynamic limit, the signal strength of linear and non-linear response coefficients does not reduce uniformly, but that their hierarchy and relative size shows characteristic differences.
↳ hep-phnucl-thPLB(2020)·40 citations
14
Shear viscosity of classical Yang-Mills field
Hidefumi Matsuda🇯🇵 · Teiji Kunihiro🇯🇵 · Berndt Müller🇺🇸 · Akira Ohnishi🇯🇵 · Toru T. Takahashi🇯🇵
We investigate the shear viscosity $η$ of the classical Yang-Mills (CYM) field on a lattice by using the Green-Kubo formula, where the shear viscosity is calculated from the time-correlation function of the energy-momentum tensor in equilibrium. Dependence of the shear viscosity $η (g, T)$ on the coupling $g$ and temperature $T$ is represented by a scaling function $f_{η} (g^{2} T)$ as $η (g, T) = T f_{η} (g^{2} T)$ due to the scaling-invariant property of the CYM. The explicit functional form of $f_{η} (g^{2} T)$ is successfully determined from the calculated shear viscosity: It turns out that $η (g, T)$ of the CYM field is proportional to $1/ g^{1.10 - 1.88}$ at weak coupling, which is a weaker dependence on $g$ than that in the leading-order perturbation theory but consistent with that of the "anomalous viscosity" $η \propto 1/ g^{1.5}$ under the strong disordered field. The obtained shear viscosity is also found to be roughly consistent with that estimated through the analysis of the anisotropy of the pressure of the CYM dynamics in the expanding geometry with recourse to a hydrodynamic equation.
↳ hep-phhep-latnucl-thPRD(2020)·5 citations
15
James Chadwick: ahead of his time
Gerhard Ecker
James Chadwick is known for his discovery of the neutron. Many of his earlier findings and ideas in the context of weak and strong nuclear forces are much less known. This biographical sketch attempts to highlight the achievements of a scientist who paved the way for contemporary subatomic physics.
↳ physics.hist-phhep-exhep-phnucl-ex+10 citations
16
Multi-particle quantum-statistical correlation functions in a Hubble-expanding hadron gas
Mate Csanad🇭🇺 · Antal Jakovac🇭🇺 · Sandor Lokos🇭🇺 · Ayon Mukherjee🇭🇺 · Srikanta Kumar Tripathy🇭🇺
Quantum-statistical correlation measurements in high-energy physics represent an important tool to obtain information about the space-time structure of the particle-emitting source. There are several final state effects which may modify the measured femtoscopic correlation functions. One of these may be the interaction of the investigated particles with the expanding hadron gas, consisting of the other final state particles. This may cause the trajectories - and hence the phases - of the quantum-correlated pairs to be modified compared to free streaming. The resulting effect and could be interpreted as an Aharonov-Bohm-like phenomenon, in the sense that the possible paths of a quantum-correlated pair represent a closed loop, with an internally present field caused by the hadron gas. In this paper, the possible role of the effect in heavy-ion experiments is presented with analytical calculations and a simple numerical model. The modification of the strength of multi-particle Bose-Einstein correlation functions is investigated, and the is found that in case of sufficiently large source density, this effect may play a non-negligible role.
↳ hep-phnucl-thGribov-90 Memorial Volume, pp. 261-273 (2…·4 citations
17
Dark Nucleosynthesis: Cross-sections and Astrophysical Signals
Rakhi Mahbubani🇬🇧 · Michele Redi🇮🇹 · Andrea Tesi🇮🇹
We investigate dark matter bound-state formation and its implication for indirect-detection experiments. We focus on the case where dark matter is a baryon of a strongly-coupled dark sector and provide generic formulae for the formation of shallow nuclear bound states on emission of photons, and W and Z gauge bosons. These processes can occur via electric and magnetic transitions, and give rise to indirect signals that are testable in monochromatic and diffuse photon measurements by Fermi and HESS. We also study the validity of factorizing the bound-state formation cross section into a short-distance nuclear part multiplied by Sommerfeld-enhancement factors. We find that the short-distance nuclear potential often violates factorization, modifying in particular the location of the peaks associated with zero-energy bound states. Finally we revisit bound-state formation of a (weakly-coupled) Minimal DM quintuplet including isospin-breaking effects, and find it gives rise to indirect-detection signals that are compatible with current bounds.
↳ hep-phastro-ph.COnucl-thJCAP(2021)·23 citations

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