Nuclear Theory·nucl-th

Tuesday·April 13, 2021

12 papers—7 primary·5 cross-listed

01
Converged ab initio calculations of heavy nuclei
T. Miyagi🇨🇦 · S. R. Stroberg🇺🇸 · P. Navrátil🇨🇦 · K. Hebeler🇩🇪 · J. D. Holt🇨🇦
We propose a novel storage scheme for three-nucleon (3N) interaction matrix elements relevant for the normal-ordered two-body approximation used extensively in ab initio calculations of atomic nuclei. This scheme reduces the required memory by approximately two orders of magnitude, which allows the generation of 3N interaction matrix elements with the standard truncation of $E_{3max} = 28$ , well beyond the previous limit of 18. We demonstrate that this is sufficient to obtain the ground-state energy of $^{132}$ Sn converged to within a few MeV with respect to the $E_{3max}$ truncation.In addition, we study the asymptotic convergence behavior and perform extrapolations to the un-truncated limit. Finally, we investigate the impact of truncations made when evolving free-space 3N interactions with the similarity renormalization group. We find that the contribution of blocks with angular momentum $J_{rel} > 9/2$ to the ground-state energy is dominated by a basis-truncation artifact which vanishes in the large-space limit, so these computationally expensive components can be neglected. For the two sets of nuclear interactions employed in this work, the resulting binding energy of $^{132}$ Sn agrees with the experimental value within theoretical uncertainties. This work enables converged ab initio calculations of heavy nuclei.
nucl-thPRC(2022)·163 citations
02
Detailed Study of the Eikonal Reaction Theory for the breakup of one-neutron halo nuclei
Chloë Hebborn🇺🇸 · Pierre Capel🇧🇪
Background: One-neutron removal reactions are used to study the single-particle structure of unstable nuclei, and in particular the exotic halo nuclei. The Eikonal Reaction Theory (ERT) has been developed by Yahiro, Ogata and Minomo in Prog. Theor. Phys. 126, 167 (2011) to include dynamical effects, which are missing in the usual eikonal description of these reactions. Encouraging results have been obtained for total breakup cross sections in comparison to more elaborate reaction models. Purpose: We extend these comparisons to more differential breakup cross sections expressed as functions of the relative energy or parallel momentum between the core and halo neutron. Method: ERT predictions of these cross sections are compared to state-of-the-art calculations. Results: The hypotheses upon which the ERT is based are confirmed and their range of validity is made clearer. The actual ordering of the evolution operators {affects ERT differential} cross sections and a specific choice leads to excellent agreement with the reference calculation. Dynamical effects in the treatment of the neutron-target interaction can be significant in the parallel-momentum observable. Conclusions: The role of the different interactions in the dynamics of breakup reactions of one-neutron halo nuclei are better understood and improvements to the ERT are suggested.
nucl-thPRC(2021)·2 citations
03
Stability of Neutron Stars with Dark Matter Core Using Three Crustal Types and the Impact on Mass-Radius Relations
Adrian G. Abac (1) · Christopher C. Bernido (2) · Jose Perico H. Esguerra (3) ((1) Max Planck Institute for Gravitational Physics · (2) Research Center for Theoretical Physics · (3) National Institute of Physics)
We investigate the effects of dark matter (DM) on the nuclear equation of state (EoS) and neutron star structure, in the relativistic mean field theory, both in the absence and presence of a crust. The $σ - ω$ model is modified by adding a WIMP-DM component, which interacts with nucleonic matter through the Higgs portal. This model agrees well with previous studies which utilized either a more complicated nuclear model or higher-order terms of the Higgs potential, in that DM softens the EoS, resulting in stars with lower maximum masses. However, instabilities corresponding to negative pressure values in the low-energy density regime of the DM-admixed EoS are present, and this effect becomes more prominent as we increase the DM Fermi momentum. We resolve this by confining DM in the star's core. The regions of instability were replaced by three types of crust: first by the Friedman-Pandharipande-Skyrme (FPS), Skyrme-Lyon (SLy) and BSk19 EoS from the Brussels-Montreal Group, which can be represented by analytical approximations. For a fixed value of the DM Fermi momentum $p_{F}^{D M}$ , the DM-admixed neutron star does not have significant changes in its mass with the addition of the crusts. However, the entire mass-radius relation of the neutron star is significantly affected, with an observed increase in the radius of the star corresponding to the mass. The effect of DM is to reduce the mass of the star, while the crust does not affect the radius significantly, as the value of the $p_{F}^{D M}$ increases.
nucl-thPhys.Dark Univ.(2023)·15 citations
04
Transport Estimations of Final State Interaction Effects on Short-range Correlation Studies Using the $(e, e^{'} p)$ and $(e, e^{'} pp)$ Reactions
N. Wright🇺🇸 · A. Papadopoulou🇺🇸 · J.R. Pybus🇺🇸 · S. Gardiner🇺🇸 · M. Roda🇬🇧 · F. Hauenstein🇺🇸 · A. Ashkenazi🇮🇱 · L.B. Weinstein🇺🇸 · A. Schmidt🇺🇸 · O. Hen🇺🇸
Short range correlated (SRC) nucleon-nucleon pairs in nuclei are typically studied using measurements of electron-induced hard nucleon-knockout reactions (e.g. $(e, e^{'} p)$ and $(e, e^{'} pN)$ ), where the kinematics of the knocked-out nucleons are used to infer their initial state prior to the interaction. The validity of this inference relies on our understanding of the scattering reaction, most importantly how rescattering of the detected nucleons (final state interactions or FSI) distort their kinematical distributions. Recent SRC measurements on medium to heavy nuclei have been performed at high- $x_{B}$ (i.e., anti-parallel kinematics) where calculations of light nuclei indicate that such distortion effects are small. Here we study the impact of FSI on recent $^{12}$ C $(e, e^{'} p)$ and $^{12}$ C $(e, e^{'} pp)$ measurements using a transport approach. We find that while FSI can significantly distort the measured kinematical distributions of SRC breakup events, selecting high- $x_{B}$ anti-parallel events strongly suppresses such distortions. In addition, including the effects of FSI improves the agreement between Generalized Contact Formalism-based calculations and data and can help identify those observables that have minimal sensitivity to FSI effects. This result helps confirm the interpretation of experimental data in terms of initial-state momentum distributions and provides a new tool for the study of SRCs using lepton-scattering reactions.
nucl-thnucl-ex4 citations
05
Nuclear Matrix Elements for Heavy Ion Sequential Double Charge Exchange Reactions
Horst Lenske🇩🇪 · Jessica Bellone🇮🇹 · Maria Colonna🇮🇹 · Danilo Gambacurta🇮🇹
The theoretical approach to a sequential heavy ion double charge exchange reaction is presented. A brief introduction into the formal theory of second-order nuclear reactions and their application to Double Single Charge Exchange (DSCE) reactions by distorted wave theory is given, thereby completing the theoretical background to our recent work [1]. Formally, the DSCE reaction amplitudes are shown to be separable into superpositions of distortion factors, accounting for initial and final state ion--ion interactions, and nuclear matrix elements. A broad space is given to the construction of nuclear DSCE response functions on the basis of polarization propagator theory. The nuclear response tensors resemble the nuclear matrix elements of $2 ν β β$ decay in structure but contain in general a considerable more complex multipole and spin structure. The QRPA theory is used to derive explicit expressions for nuclear matrix elements (NMEs). The differences between the NME of the first and the second interaction vertexes in a DSCE reaction is elucidated. Reduction schemes for the transition form factors are discussed by investigating the closure approximation and the momentum structure of form factors. DSCE unit strength cross sections are derived.
nucl-thnucl-exUniverse(2021)·27 citations
06
Cutoff effects in Hartree-Fock calculations at leading order of chiral effective field theory
M. Sánchez Sánchez🇫🇷 · Dao Duy Duc🇫🇷 · L. Bonneau🇫🇷
We explore the effects on nuclear bulk properties of using regularization cutoffs larger than the nucleon mass within the chiral effective field theory with a power counting that ensures order-by-order renormalization in the two-nucleon system. To do so we calculate ground-state properties of the $^{16}$ O nucleus in the Hartree--Fock approach in a basis made up of plane waves confined in a cube. We find that regularization cutoff effects manifest themselves in two distinct ways: a strong sensitivity to the the counter-terms in attractive singular partial waves (related to the sign of the corresponding low-energy constant) and to the correction for spurious deeply bound states (for high enough cutoffs). In fact the latter happens to deprive the Hartree--Fock approximation of yielding bound solutions in nuclei. We conclude that, when using a leading-order chiral potential in the Nogga--Timmermans--van Kolck's power counting (with a regularization cutoff higher than the nucleon mass), one cannot produce a selfconsistent mean field free of spurious bound-state effects that can serve as a reference state for beyond-mean-field methods. For high regularization cutoffs which yield an attractive $^{3} S_{1}$ contact potential, one can at best incorporate in the mean-field solution a partial correction for spurious bound states. Then the remaining correction has to be added to the residual interaction in a treatment beyond the Hartree--Fock approximation. In fact a ``full'' correction in the $^{3} D_{2}$ channel, with energy shifts of the order of or somewhat larger than those recommended in Phys. Rev. C 103, 054304 (2021), is possible.
nucl-thPRC(2023)·1 citation
07
Interpreting the charge-dependent flow and constraining the chiral magnetic wave with event shape engineering
Chun-Zheng Wang🇨🇳 · Wen-Ya Wu🇨🇳 · Qi-Ye Shou🇨🇳 · Guo-Liang Ma🇨🇳 · Yu-Gang Ma🇨🇳 · Song Zhang🇨🇳
The charge asymmetry (Ach) dependence of anisotropic flow serves as an important tool to search for the chiral magnetic wave (CMW) in heavy-ion collisions. However, the background effect, such as the local charge conservation (LCC) entwined with collective flow, has not yet been unambiguously eliminated in the measurement. With the help of two models, the AMPT with initial quadrupole moment and the blast wave (BW) incorporating LCC, we discuss the features of the LCC-induced and the CMW-induced correlations between Ach and the flow. More importantly, we first propose to use the Event Shape Engineering (ESE) technique to distinguish the background and the signal for the CMW study. This method would be highly desirable in the experimental search for the CMW and provides more insights for understanding the charge-dependent collective motion of the quark-gluon plasma.
nucl-thnucl-exPLB(2021)·16 citations
08
Pion form factor from an AdS deformed background
Miguel Angel Martin Contreras🇨🇱 · Eduardo Folco Capossoli🇧🇷 · Danning Li🇨🇳 · Alfredo Vega🇨🇱 · Henrique Boschi-Filho🇧🇷
We consider a bottom-up AdS/QCD model with a conformal exponential deformation $e^{k z^{2}}$ on a Lorentz invariant AdS background. In this model, we assume the conformal dimension associated with the operator that creates pions at the boundary as $Δ = 3$ . Regarding the infrared scale related to photon field $k_{γ}$ , we analyze two cases: constant and depending on the transferred momentum $q$ . In these two cases, we computed the electromagnetic pion form factor as well as the pion radius. We compare our results with experimental data as well as other theoretical (holographic and non-holographic) models. In particular, for the momentum-dependent infrared scale, we find good agreement with the available experimental data as well as non-holographic models.
↳ hep-phhep-thnucl-thNPB(2022)·21 citations
09
Nonanalyticity, sign problem and Polyakov line in Z3-symmetric heavy quark model at low temperature: Phenomenological model analyses
Hiroaki Kouno🇯🇵 · Kouji Kashiwa🇯🇵 · Takehiro Hirakida🇯🇵
The nonanalyticity and the sign problem in the Z3-symmetric heavy quark model at low temperature are studied phenomenologically. For the free heavy quarks, the nonanalyticity is analyzed in the relation to the zeros of the grand canonical partition function. The Z3-symmetric effective Polyakov-line model (EPLM) in strong coupling limit is also considered as an phenomenological model of Z3-symmetric QCD with large quark mass at low temperature. We examine how the Z3-symmetric EPLM approaches to the original one in the zero-temperature limit. The effects of the Z3-symmetry affect the structure of zeros of the microscopic probability density function at the nonanalytic point. The average value of the Polyakov line can detect the structure, while the other thermodynamic quantities are not sensible to the structure in the zero-temperature limit. The effect of the imaginary quark chemical potential is also discussed. The imaginary part of the quark number density is very sensitive to the symmetry structure at the nonanalytical point. For a particular value of the imaginary quark number chemical potential, large quark number may be induced in the vicinity of the nonanalytical point.
↳ hep-phhep-latnucl-thPRD(2021)·1 citation
10
Generating function for nucleus-nucleus scattering amplitudes in Glauber theory
Yu.M. Shabelski🇷🇺 · A.G. Shuvaev🇷🇺
A new approach to deal with the scattering amplitudes in Glauber theory is proposed. It relies on the use of generating function, that has been explicitly found. The method is applied to the analytical calculation of the nucleus-nucleus elastic scattering amplitudes in the all interaction orders of the Glauber theory.
↳ hep-phnucl-thPRC(2021)·9 citations
11
Detailed analysis of excited state systematics in a lattice QCD calculation of $g_{A}$
Jinchen He🇨🇳 · David A. Brantley🇺🇸 · Chia Cheng Chang🇯🇵 · Ivan Chernyshev🇺🇸 · Evan Berkowitz🇺🇸 · Dean Howarth🇺🇸 · Christopher Körber🇺🇸 · Aaron S. Meyer🇺🇸 · Henry Monge-Camacho🇺🇸 · Enrico Rinaldi🇺🇸 · Chris Bouchard🇬🇧 · M.A. Clark🇺🇸 and 5 other authors
Excited state contamination remains one of the most challenging sources of systematic uncertainty to control in lattice QCD calculations of nucleon matrix elements and form factors: early time separations are contaminated by excited states and late times suffer from an exponentially bad signal-to-noise problem. High-statistics calculations at large time separations $≳ 1$ fm are commonly used to combat these issues. In this work, focusing on $g_{A}$ , we explore the alternative strategy of utilizing a large number of relatively low-statistics calculations at short to medium time separations (0.2--1 fm), combined with a multi-state analysis. On an ensemble with a pion mass of approximately 310 MeV and a lattice spacing of approximately 0.09 fm, we find this provides a more robust and economical method of quantifying and controlling the excited state systematic uncertainty. A quantitative separation of various types of excited states enables the identification of the transition matrix elements as the dominant contamination. The excited state contamination of the Feynman-Hellmann correlation function is found to reduce to the 1% level at approximately 1 fm while for the more standard three-point functions, this does not occur until after 2 fm. Critical to our findings is the use of a global minimization, rather than fixing the spectrum from the two-point functions and using them as input to the three-point analysis. We find that the ground state parameters determined in such a global analysis are stable against variations in the excited state model, the number of excited states, and the truncation of early-time or late-time numerical data.
↳ hep-lathep-phnucl-thPRC(2022)·23 citations
12
Electromagnetic transition form factors and Dalitz decays of hyperons
Stefan Leupold (Uppsala U.)🇸🇪 · Nora Salone (Uppsala U. and NCBJ, Warsaw)🇸🇪
Dalitz decays of a hyperon resonance to a ground-state hyperon and an electron-positron pair can give access to some information about the composite structure of hyperons. We present expressions for the multi-differential decay rates in terms of general transition form factors for spin-parity combinations J^P = 1/2^+/-, 3/2^+/- of the hyperon resonance. Even if the spin of the initial hyperon resonance is not measured, the self-analyzing weak decay of the "final" ground-state hyperon contains information about the relative phase between combinations of transition form factors. This relative phase is non-vanishing because of the unstable nature of the hyperon resonance. If all form factor combinations in the differential decay formulae are replaced by their respective values at the photon point, one obtains a QED type approximation, which might be interpreted as characterizing hypothetical hyperons with point-like structure. We compare the QED type approximation to a more realistic form factor scenario for the lowest-lying singly-strange hyperon resonances. In this way we explore which accuracy in the measurements of the differential Dalitz decay rates is required in order to distinguish the composite-structure case from the pointlike case. Based on the QED type approximation we obtain as a by-product a rough prediction for the ratio between the Dalitz decay width and the corresponding photon decay width.
↳ hep-phnucl-thEPJA(2021)·11 citations

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first authorsco-authorsvia INSPIRE