Nuclear Theory·nucl-th

Tuesday·March 2, 2021

17 papers—10 primary·7 cross-listed

01
Effect of deuteron breakup on the deuteron- $Ξ$ correlation function
Kazuyuki Ogata🇯🇵 · Tokuro Fukui🇯🇵 · Yuki Kamiya🇨🇳 · Akira Ohnishi🇯🇵
The hadron-deuteron correlation function has attracted many interests as a potential method to access the three-hadron interactions. However, the weakly-bound nature of deuteron has not been considered in the preceding studies. In this study, the breakup effect of deuteron on the deuteron- $Ξ^{-}$ ( $d$ - $Ξ^{-}$ ) correlation function $C_{d Ξ^{-}}$ is investigated. The $d$ - $Ξ^{-}$ scattering is described by a nucleon-nucleon- $Ξ$ three-body reaction model. The continuum-discretized coupled-channels method, which is a fully quantum-mechanical and non-perturbative reaction model, is adopted. $C_{d Ξ^{-}}$ turns out to be sensitive to the strong interaction and enhanced by the deuteron breakup effect by 6--8 % for the $d$ - $Ξ^{-}$ relative momentum below about 70 MeV/ $c$ . Low-lying neutron-neutron continuum states are responsible for this enhancement. Within the adopted model, the deuteron breakup effect on $C_{d Ξ^{-}}$ is found to be appreciable but not very significant. Except for the enhancement by several percent, studies on $C_{d Ξ^{-}}$ without the deuteron breakup effect can be justified.
nucl-thPRC(2021)·23 citations
02
Symmetry projection to coupled-cluster singles and doubles wave function through the Monte Carlo method
Takahiro Mizusaki🇯🇵 · Peter Schuck🇫🇷
A new method for calculating the symmetry-projected energy of coupled-cluster singles and doubles (CCSD) wave function through the Monte Carlo method is proposed. We present benchmark calculations in considering the three-level Lipkin model which is a simple and minimal model with two phases: spherical and deformed ones. It is demonstrated that this new method gives good ground state energy and low-lying spectra.
nucl-thPRC(2021)·2 citations
03
The description of giant dipole resonance key parameters with multitask neural networks
J. H. Bai (1)🇨🇳 · Z. M. Niu (2 and 3)🇨🇳 · B. Y. Sun (1)🇨🇳 · Y. F. Niu (1) ((1) School of Nuclear Science and Technology, Lanzhou University, Lanzhou, China, (2) School of Physics and Materials Science, Anhui University, Hefei, China, (3) Institute of Physical Science and Information Technology, Anhui University, Hefei, China)🇨🇳
Giant dipole resonance (GDR) is one of the fundamental collective excitation modes in nucleus. Continuous efforts have been made to the evaluation of GDR key parameters in different nuclear data libraries. We introduced multitask learning (MTL) approach to learn and reproduce the evaluated experimental data of GDR key parameters, including both GDR energies and widths. Compared to the theoretical GDR parameters in RIPL-3 library, the accuracies of MTL approach are almost doubled for 129 nuclei with experimental data. The significant improvement is largely due to the right classification of unimodal nuclei and bimodal nuclei by the classification neural network. Based on the good performance of the neural network approach, an extrapolation to 79 nuclei around the $β$ -stability line without experimental data is made, which provides an important reference to future experiments and data evaluations. The successful application of MTL approach in this work further proofs the feasibility of studying multi-output physical problems with multitask neural network in nuclear physics domain.
nucl-thPLB(2021)·28 citations
04
Quadrupole radiation and $e^{+} e^{-}$ pair production in the collision of nonrelativistic nuclei
I.V. Obraztsov · A.I. Milstein
We analyze the one-photon mechanism of $e^{+} e^{-}$ pair production in the collision of nonrelativistic nuclei. The contribution of electric quadrupole radiation of virtual photon to the corresponding cross section is found. The effect of the finite nuclear size is considered in detail. A comparison is made with the contribution of electric dipole radiation of virtual photon and with the contribution of the two-photon pair production mechanism. It is shown that the contribution of electric quadrupole radiation is dominant in a wide range of relative velocities. The cross section for the production of $e^{+} e^{-}$ pair with the capture of an electron by one of the nuclei is also analyzed.
nucl-thphysics.atom-phPLB(2021)·5 citations
05
Analysis of critical parameters for nonrelativistic models in symmetric nuclear matter
Mariana Dutra🇧🇷 · Odilon Lourenço🇧🇷 · Xavier Viñas🇪🇸 · C. Mondal🇪🇸
In this work we have analyzed several features of symmetric nuclear matter (SNM) at finite temperature described by different zero- and finite-range nonrelativistic families of models, namely, Skyrme, Gogny, Momentum-dependent interaction (MDI), Michigan three-range Yukawa (M3Y) and Simple Effective Interaction (SEI). We have calculated the critical parameters (CP) associated to the liquid-gas phase coexistence for nuclear matter from these parametrizations and show that they are in agreement with their experimental and theoretical values obtained in the literature. Our study also points out to a strong evidence of universality presented by the hadronic models, namely, model independence in the gaseous phase and distinguishability among different interactions in the liquid phase. We have performed a correlation study among different CP and SNM properties. Such studies involving different finite range interactions are scarce in literature. The analyzed models show an overall increasing trend of the critical temperature as a function of critical pressure.
nucl-thPRC(2021)·3 citations
06
Role of unitary correlation operator on high-momentum antisymmetrized molecular dynamics using bare NN interaction for 3H and 4He
Qing Zhao · Masahiro Isaka · Takayuki Myo · Mengjiao Lyu · Hiroshi Toki · Hisashi Horiuchi · Hiroki Takemoto · Niu Wan
We extend the high-momentum antisymmetrized molecular dynamics (HMAMD) by incorporating the short-range part of the unitary correlation operator method (UCOM) as the variational method of finite nuclei. In this HMAMD+UCOM calculation of light nuclei, the HMAMD is mainly in charge of the tensor correlation with up to the four-body correlation, while the short-range correlation is further improved by using the UCOM. The binding energies of the 3H and 4He nuclei are calculated with this HMAMD+UCOM using the AV8' bare nucleon-nucleon (NN) interaction. The different roles of the short-range and tensor correlations from the HMAMD and UCOM are analyzed in the numerical results. Compared with the previous calculations based on the different variational methods, this newly extended HMAMD+UCOM method can almost provide the consistent results with the ab initio results.
nucl-thPTEP(2021)·4 citations
07
Multiple $S U (3)$ algebras in interacting boson model and shell model: Results for $(β, γ$ ) bands and scissors $1^{+}$ band
V.K.B. Kota · R. Sahu
Shell model and interacting boson model spaces admit multiple $S U^{(α)} (3)$ algebras generating the same rotational spectra but different $E 2$ decay properties, depending on the phases $α$ in the quadrupole generator. In the ground ( $g$ ) $K = 0^{+}$ bands in nuclei this is demonstrated recently using systems with nucleons in a single oscillator shell [Kota, Sahu and Srivastava, Bulg. J. Phys. {\bf 46}, 313 (2019); Eur. Phys. J. Special Topics {\bf 229}, 2389 (2020)]. Going beyond these preliminary studies, results are presented here for $E 2$ decay properties of $β$ and $γ$ bands members, as generated by multiple $S U (3)$ algebras, using $s d g$ IBM and $s d g i$ IBM examples. In addition, results are presented for the $E 2$ and $M 1$ decay properties of the levels of the $1^{+}$ scissors band in heavy nuclei using $s d g$ IBM-2 and $s d g i$ IBM-2. The scissors $1^{+}$ band properties are also studied using a shell model example with six protons in $(p f)$ shell and twelve neutrons in $(s d g)$ shell. These results establish that: (i) with multiple $S U (3)$ algebras, it is possible to have rotational bands with very weak $E 2$ strengths among the levels where normally one expects strong strengths; (ii) $E 2$ decay of the levels of $β$ and $γ$ bands to the ground band are quite different for some of the $S U^{(α)} (3)$ algebras with strong dependence on $α$ ; (iii) it is possible to have the scissors $1^{+}$ band with the $E 2$ and $M 1$ decay of the low-lying levels of this band to the $g$ band are strong or weak depending on $α$ .
nucl-thNPA(2021)·4 citations
08
Topology change, emergent symmetries and compact star matter
Yong-Liang Ma🇨🇳 · Mannque Rho🇫🇷
Topology effects have being extensively studied and confirmed in strongly correlated condensed matter physics. In the large color number limit of QCD, baryons can be regarded as topological objects -- skyrmions -- and the baryonic matter can be regarded as a skyrmion matter. We review in this paper the generalized effective field theory for dense compact-star matter constructed with the robust inputs obtained from the skyrmion approach to dense nuclear matter, relying to possible ``emergent" scale and local flavor symmetries at high density. All nuclear matter properties from the saturation density $n_{0}$ up to several times $n_{0}$ can be fairly well described. A uniquely novel -- and unorthdox -- feature of this theory is the precocious appearance of the pseudo-conformal sound velocity $v_{s}^{2} / c^{2} \approx 1/3$ , with the non-vanishing trace of the energy momentum tensor of the system. The topology change encoded in the density scaling of low energy constants is interpreted as the quark-hadron continuity in the sense of Cheshire Cat Principle (CCP) at density $\gsim 2 n_{0}$ in accessing massive compact stars. We confront the approach with the data from GW170817 and GW190425.
nucl-thastro-ph.HEhep-phAAPPS Bull.(2021)·19 citations
09
Resolution of the spin paradox in the Nilsson model
Hadi Sobhani🇮🇷 · Hassan Hassanabadi🇮🇷 · Dennis Bonatsos🇬🇷
In the well-known Nilsson diagrams, depicting the dependence of the nuclear single-particle energy levels on quadrupole deformation, a spin paradox appears {as the deformation sets in, leading from spherical shapes to prolate deformed shapes with cylindrical symmetry}. Bunches of levels corresponding to a spherical shell model orbital, sharing the same orbital angular momentum and the same total angular momentum, appear to correspond to Nilsson energy levels, labeled by asymptotic quantum numbers in cylindrical coordinates, some of which have spin up, while some others have spin down. Furthermore, for some orbitals the correspondence between spherical shell model quantum numbers and Nilsson asymptotic quantum numbers is not the same for protons and for neutrons. Introducing a new rule of correspondence between the two sets of quantum numbers, we show that the spin paradox is resolved and full agreement between the proton and neutron Nilsson diagrams is established. The form of the Nilsson diagrams as a function of the quadrupole deformation remains unchanged, the only difference between the new diagrams and the traditional ones being the mutual exchange of the Nilsson labels for certain pairs of single-particle energy levels.
nucl-thquant-phEur.Phys.J.Plus(2021)·7 citations
10
Pseudo-gauge dependence of quantum fluctuations of energy in a hot relativistic gas of fermions
Arpan Das🇵🇱 · Wojciech Florkowski🇵🇱 · Radoslaw Ryblewski🇵🇱 · Rajeev Singh🇵🇱
Explicit expressions for quantum fluctuations of energy in subsystems of a hot relativistic gas of spin- $1/2$ particles are derived. The results depend on the form of the energy-momentum tensor used in the calculations, which is a feature described as pseudo-gauge dependence. However, for sufficiently large subsystems the results obtained in different pseudo-gauges converge and agree with the canonical-ensemble formula known from statistical physics. As different forms of the energy-momentum tensor of a gas are a priori equivalent, our finding suggests that the concept of quantum fluctuations of energy in very small thermodynamic systems is pseudo-gauge dependent. On the practical side, the results of our calculations determine a scale of coarse graining for which the choice of the pseudo-gauge becomes irrelevant.
nucl-thhep-phhep-thPRD(2021)·28 citations
11
Recent progresses on QCD phases in a strong magnetic field -- views from Nambu--Jona-Lasinio model
Gaoqing Cao🇨🇳
In this review, we summarize recent progress on the possible phases of quantum chromodynamics (QCD) in the presence of a strong magnetic field, mainly from the views of the chiral effective Nambu--Jona-Lasinio model. Four kinds of phase transitions are explored in detail: chiral symmetry breaking and restoration, neutral pseudoscalar superfluidity, charged pion superfluidity and charged rho superconductivity. In particular, we revisit the unsolved problems of inverse magnetic catalysis effect and competition between the chiral density wave and solitonic modulation phases. It is shown that useful results can be obtained by adopting self-consistent schemes.
↳ hep-phnucl-thEPJA(2021)·59 citations
12
Multi-particle systems on the lattice and chiral extrapolations: a brief review
Maxim Mai🇺🇸 · Michael Döring🇺🇸 · Akaki Rusetsky🇩🇪
The extraction of two- and three-body hadronic scattering amplitudes and the properties of the low-lying hadronic resonances from the finite-volume energy levels in lattice QCD represents a rapidly developing field of research. The use of various modifications of the Lüscher finite-volume method has opened a path to calculate infinite-volume scattering amplitudes on the lattice. Many new results have been obtained recently for different two- and three-body scattering processes, including the extraction of resonance poles and their properties from lattice data. Such studies, however, require robust parametrizations of the infinite-volume scattering amplitudes, which rely on basic properties of $S$ -matrix theory and -- preferably -- encompass systems with quark masses at and away from the physical point. Parametrizations of this kind, provided by unitarized Chiral Perturbation Theory, are discussed in this review. Special attention is paid to three-body systems on the lattice, owing to the rapidly growing interest in the field. Here, we briefly survey the formalism, chiral extrapolation, as well as finite-volume analyses of lattice data.
↳ hep-lathep-phnucl-thEur.Phys.J.ST(2021)·92 citations
13
Rosenbluth separation of $d σ_{L} / dt$ and $d σ_{T} / dt$ in $π^{0}$ deeply virtual electroproduction from the proton
I. Korover🇺🇸 · R.G. Milner🇺🇸
We report on a Rosenbluth separation using previously published data by the CLAS collaboration in Hall B, Jefferson Lab for exclusive $π^{0}$ deeply virtual electroproduction (DVEP) from the proton at a mean $Q^{2}$ of $\approx$ 2 (GeV/c) $^{2}$ . The central question we address is the applicability of factorization in $π^{0}$ DVEP at these kinematics. The results of our Rosenbluth separation clearly demonstrate the dominance of the longitudinal contribution to the cross section. The extracted longitudinal and transverse contributions are in agreement with previous data from Hall A at Jefferson Lab, but over a much wider $- t$ range (0.12 - 1.8 (GeV/c) $^{2}$ ). The measured dominance of the longitudinal contribution at $Q^{2} \approx$ 2 (GeV/c) $^{2}$ is consistent with the expectation of the handbag factorization theorem. We find that $σ_{L} (t) \sim 1/ (- t)$ for $- t >$ 0.5 (GeV/c) $^{2}$ . Determination of both longitudinal and transverse contributions to the deeply virtual $π^{0}$ electroproduction cross section allows extraction of additional GPDs.
↳ hep-phnucl-exnucl-th2 citations
14
High-precision determination of the $K_{e 3}$ radiative corrections
Chien-Yeah Seng🇩🇪 · Daniel Galviz🇩🇪 · Mikhail Gorchtein🇩🇪 · Ulf-G. Meißner🇩🇪
We report a high-precision calculation of the Standard Model electroweak radiative corrections in the $K \to π e^{+} ν (γ)$ decay as a part of the combined theory effort to understand the existing anomaly in the determinations of $V_{u s}$ . Our new analysis features a chiral resummation of the large infrared-singular terms in the radiative corrections and a well-under-control strong interaction uncertainty based on the most recent lattice QCD inputs. While being consistent with the current state-of-the-art results obtained from chiral perturbation theory, we reduce the existing theory uncertainty from $1 0^{- 3}$ to $1 0^{- 4}$ . Our result suggests that the Standard Model electroweak effects cannot account for the $V_{u s}$ anomaly.
↳ hep-phhep-exhep-latnucl-ex+1PLB(2021)·35 citations
15
Weakly bound $H$ dibaryon from SU(3)-flavor-symmetric QCD
Jeremy R. Green🇨🇭 · Andrew D. Hanlon🇩🇪 · Parikshit M. Junnarkar🇩🇪 · Hartmut Wittig🇩🇪
We present the first study of baryon-baryon interactions in the continuum limit of lattice QCD, finding unexpectedly large lattice artifacts. Specifically, we determine the binding energy of the $H$ dibaryon at a single quark-mass point. The calculation is performed at six values of the lattice spacing $a$ , using O( $a$ )-improved Wilson fermions at the SU(3)-symmetric point with $m_{π} = m_{K} \approx 420$ MeV. Energy levels are extracted by applying a variational method to correlation matrices of bilocal two-baryon interpolating operators computed using the distillation technique. Our analysis employs Lüscher's finite-volume quantization condition to determine the scattering phase shifts from the spectrum and vice versa, both above and below the two-baryon threshold. We perform global fits to the lattice spectra using parametrizations of the phase shift, supplemented by terms describing discretization effects, then extrapolate the lattice spacing to zero. The phase shift and the binding energy determined from it are found to be strongly affected by lattice artifacts. Our estimate of the binding energy in the continuum limit of three-flavor QCD is $B_{H}^{SU(3)_{f}} = 4.56 \pm 1.1 3_{stat} \pm 0.6 3_{syst}$ MeV.
↳ hep-lathep-phnucl-thPRL(2021)·139 citations
16
Transition distribution amplitudes and hard exclusive reactions with baryon number transfer
B. Pire🇫🇷 · K. Semenov-Tian-Shansky🇷🇺 · L. Szymanowski🇵🇱
Baryon-to-meson and baryon-to-photon transition distribution amplitudes (TDAs) arise in the collinear factorized description of a class of hard exclusive reactions characterized by the exchange of a non-zero baryon number in the cross channel. These TDAs extend the concepts of generalized parton distributions (GPDs) and baryon distribution amplitudes (DAs). In this review, we discuss the general properties and physical interpretation of baryon-to-meson and baryon-to-photon TDAs. We argue that these non-perturbative objects are a convenient complementary tool to explore the structure of baryons at the partonic level. We present an overview of hard exclusive reactions admitting a description in terms of TDAs. We discuss the first signals from hard exclusive backward meson electroproduction at JLab with the 6 GeV electron beam and explore further experimental opportunities to access TDAs at JLab@12 GeV, PANDA, J-PARC and EIC.
↳ hep-phhep-exnucl-thPhys.Rept.(2021)·37 citations
17
Emergent Hadrons and Diquarks
Kenji Fukushima🇯🇵 · Jan M. Pawlowski🇩🇪 · Nils Strodthoff🇩🇪
We discuss the emergence of a low-energy effective theory with quarks, mesons, diquarks and baryons at vanishing and finite baryon density from first principle QCD. The present work also includes an overview on diquarks at vanishing and finite density, and elucidates the physics of transitional changes from baryonic matter to quark matter including diquarks. This set-up is discussed within the functional renormalisation group approach with dynamical hadronisation. In this framework it is detailed how mesons, diquarks, and baryons emerge dynamically from the renormalisation flow of the QCD effective action. Moreover, the fundamental degrees of freedom of QCD, quarks and gluons, decouple from the dynamics of QCD below the respective mass gaps. The resulting global picture unifies the different low energy effective theories used for low and high densities within QCD, and allows for a determination of the respective low energy constants directly from QCD.
↳ hep-phhep-thnucl-thAnnals Phys.(2022)·42 citations

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