Nuclear Theory·nucl-th

Thursday·November 28, 2019

13 papers—8 primary·5 cross-listed

01
Effect of compound nucleus spin correlations on fission fragment angular distribution
Oleksandr Gorbachenko · Sergey Kun
We extend a conventional description of the fusion-fission fragment angular distributions by introducing the correlation between compound nucleus states carrying different total angular momenta. This correlation results in the strong anisotropy and mass-angle correlation of fission fragments for compact saddle-point nuclear shapes for which the conventional description predicts almost isotropic angular distributions. The spin off-diagonal phase relaxation timescale, $≃ 1 0^{- 19}$ sec, obtained from analysis of anomalous fission fragment angular distributions in $^{12}$ C+ $^{236}$ U, $^{16}$ O+ $^{232}$ Th and $^{16}$ O+ $^{238}$ U collisions at the sub-barrier energies is three orders of magnitude longer than the timescale of the compound nucleus thermalization. Expression for the angle-dependent time power spectrum for quasifission is also presented.
nucl-thquant-ph0 citations
02
High-precision nuclear forces from chiral EFT: State-of-the-art, challenges and outlook
E. Epelbaum🇩🇪 · H. Krebs🇩🇪 · P. Reinert🇩🇪
We review a new generation of nuclear forces derived in chiral effective field theory using the recently proposed semilocal regularization method. We outline the conceptual foundations of nuclear chiral effective field theory, discuss all steps needed to compute nuclear observables starting from the effective chiral Lagrangian and consider selected applications in the two- and few-nucleon sectors. We highlight key challenges in developing high-precision tree-body forces, such as the need to maintain consistency between two- and many-body interactions and constraints placed by the chiral and gauge symmetries after regularization.
nucl-thhep-phnucl-exFront.in Phys.(2020)·178 citations
03
Parton Hadron Quantum Molecular Dynamics (PHQMD) -- a Novel Microscopic N-Body Transport Approach for Heavy-Ion Dynamics and Hypernuclei Production
E. Bratkovskaya🇩🇪 · J. Aichelin🇫🇷 · A. Le Fevre🇩🇪 · V. Kireyeu🇷🇺 · V. Kolesnikov🇷🇺 · Y. Leifels🇩🇪 · V. Voronyuk🇷🇺
We present the novel microscopic n-body dynamical transport approach PHQMD(Parton-Hadron-Quantum-Molecular-Dynamics) for the description of particle production and cluster formation in heavy-ion reactions at relativistic energies. The PHQMD extends the established PHSD (Parton-Hadron-String-Dynamics) transport approach by replacing the mean field by density dependent two body interactions in a similar way as in the Quantum Molecular Dynamics (QMD) models. This allows for the calculation of the time evolution of the n-body Wigner density and therefore for a dynamical description of clusters and hypernuclei formation. The clusters are identified with the MST ('Minimum Spanning Tree') or the SACA ('Simulated Annealing Cluster Algorithm') algorithm which - by regrouping the nucleons in single nucleons and noninteracting clusters - finds the most bound configuration of nucleons and clusters. The selected results on clusters and hypernuclei production from Ref. arXiv:1907.03860 are discussed in this contribution.
nucl-thSpringer Proc.Phys.(2020)·2 citations
04
Toroidal States of the $^{12}$ C Nucleus
Cheuk-Yin Wong
Among the states of $^{12}$ C, there is an important subset of $K$ =0 and $K$ = $I$ planar intrinsic states in which the intrinsic motion of the nucleons are confined in the planar region defined by the three-alpha cluster or by their generated toroid. The intrinsic nuclear densities of these states are toroidal in nature. We study these $^{12}$ C toroidal states from the generator-coordinate viewpoints in both the alpha cluster model and the toroidal shell model. Numerical solutions in the toroidal mean field approximation are examined to pave the way for future extensions and refinements.
nucl-thBulg.J.Phys.(2019)·0 citations
05
Comparison of Practical Expressions for E1 Photon Strength Functions
Oleksandr Gorbachenko · Igor Kadenko · Vladimir Plujko · Kateryna Solodovnyk
The closed-form expressions for the photon strength functions (PSF) are tested using the gamma-decay data of OSLO group. The theoretical calculations are performed for the Lorentzian models of PSF for electric and magnetic dipole gamma-rays. The criteria of minimum of least-square value as well as the root-mean-square deviation factor are used. It is shown that a rather good agreement is obtained within the Simple Modified Lorentzian model for E1 PSF modelling.
nucl-thnucl-ex0 citations
06
Neutrinoless Double-Beta Decay and Realistic Shell Model
Nunzio Itaco🇺🇸 · Luigi Coraggio🇮🇹 · Riccardo Mancino🇺🇸
We report on the calculation of the neutrinoless double-beta decay nuclear matrix element for 76Ge within the framework of the realistic shell model. The effective shell-model Hamiltonian and the two-body transition operator describing the decay are derived by way of many-body perturbation theory. Particular attention is focused on the role played by the so-called Pauli blocking effect in the derivation of the effective operator.
nucl-thEPJ Web Conf.(2019)·1 citation
07
Description of nuclear photoexcitation by Lorentzian expressions for electric dipole photon strength function
Vladimir Plujko · Oleksandr Gorbachenko · Kateryna Solodovnyk
The description of photoabsorption cross-sections of cold nuclei by closed-form Lorentzian models of photon strength functions for photoexcitation by electric dipole gamma-rays is considered. Systematics of the GDR parameters are given and input parameters of different analytical models are discussed The experimental data are compared with theoretical calculations for even-even nuclei using criteria of minimum of both least-square value and root-mean-square deviation factor. Simple extensions of the models with energy-dependent widths to high gamma-ray energies $≳$ 30MeV which hold the energy-weighted sum rule for E1 gamma-transitions in good approximation are proposed and tested.
nucl-thnucl-exEPJA(2019)·7 citations
08
Scattering in strong electromagnetic fields: transverse size effects in tBLFQ
Bolun Hu🇨🇳 · Anton Ilderton🇬🇧 · Xingbo Zhao🇨🇳
The framework of 'time-dependent basis light-front quantisation' (tBLFQ) offers a non-perturbative approach to scattering problems in external fields, based on Fock space truncation. Here we extend tBLFQ to include spatio-temporal field inhomogeneities in multiple spacetime directions. This extension is necessary for the proper modelling of e.g. intense laser fields. We focus on the example of nonlinear Compton scattering of an electron on an axicon-type laser, with an emphasis on the transverse structure of the beam. We analyse the impact of field intensity and particle energy, as well as basis truncation effects, on the radiation spectrum of the scattered electron.
nucl-thhep-phPRD(2020)·16 citations
09
Light (anti-)nuclei and (anti-)hypertriton production in $pp$ collisions at $s = 0.90, 2.76$ and $7$ TeV
Nserdin A. Ragab🇨🇳 · Zhi-Lei She🇨🇳 · Gang Chen🇨🇳
Production of light (anti-)nuclei and (anti-)hypertriton within midrapidity ( $∣ y ∣ < 0.5$ ) and $p_{T} < 3.0$ GeV/c in $pp$ interactions at $s$ = 0.90, 2.76 and 7 TeV is investigated by the dynamically constrained phase space coalescence model (DCPC), combined with {\footnotesize{PACIAE}} model. The ALICE data for yields, ratios, as well as transverse momentum distributions of $d$ and $d$ are well reproduced by the model simulations, meanwhile the three basic characters of $^{3} He$ , $^{3} He$ , $_{Λ}^{3} H$ , and $_{Λ}^{3} H$ are also predicted. Besides, we found the yields of light (anti-)nuclei produced are dependent upon their mass number $A$ , namely, their yields sharply decrease with the increasing of $A$ . The strangeness population factor $s_{3} = (_{Λ}^{3} H /^{3} He) / (Λ/p)$ is found to be about 0.7 $\sim$ 0.8, and is comparable with the available experimental results.
↳ hep-phnucl-thEur.Phys.J.Plus(2020)·5 citations
10
Infrared renormalon effects in color dipole TMD PDF at small- $x$
Nahid Vasim🇮🇳 · Raktim Abir🇮🇳
The uncertainties from the infrared renormalons in the (color dipole) gluon distribution is estimated. It is shown that non-linear saturation effects at small- $x$ shift the first IR pole at the Borel plane from $2/ β_{2}$ to $1/ β_{2}$ . As a consequence the estimated uncertainty is found to be $O (Λ_{QCD}^{2})$ instead of $O (Λ_{QCD}^{4})$ .
↳ hep-phhep-thnucl-thNPB(2020)·1 citation
11
Quark condensate seesaw mechanism for neutrino mass
A. Babič🇨🇿 · S. Kovalenko🇨🇱 · M. I. Krivoruchenko🇷🇺 · F. Šimkovic🇨🇿
We study a mechanism of generation of Majorana neutrino mass due to spontaneous breaking of chiral symmetry (SBCS) accompanied by the formation of a quark condensate. The effect of the condensate is transmitted to the neutrino sector via Lepton-Number Violating (LNV) lepton-quark dimension- $7$ operators known in the literature as an origin of the neutrino-mass-independent mechanism of neutrinoless double-beta ( $0 ν β β$ ) decay. The smallness of neutrino masses is due to a large ratio between the LNV scale and the scale of the SBCS. This is a new realization of the seesaw mechanism, which we dub the Quark Condensate SeeSaw (QCSS). We examine the predictions of the QCSS for $0 ν β β$ -decay and neutrino mass spectrum. We will show that our model predicts the normal neutrino mass ordering and narrow ranges of the neutrino masses.
↳ hep-phnucl-thPRD(2021)·10 citations
12
Exploring the QCD phase diagram via reweighting from isospin chemical potential
Bastian B. Brandt🇩🇪 · Francesca Cuteri🇩🇪 · Gergely Endrodi🇩🇪 · Sebastian Schmalzbauer🇩🇪
We investigate the QCD phase diagram for small values of baryon and strange quark chemical potentials from simulations at non-zero isospin chemical potential. Simulations at pure isospin chemical potential are not hindered by the sign problem and pion condensation can be observed for sufficiently large isospin chemical potentials. We study how the related phase boundary evolves with baryonic and strange chemical potentials via reweighting in quark chemical potentials and discuss our results. Furthermore, we propose and implement an alternative method to approach nonzero baryon (and strange quark) chemical potentials. This method involves simulations where physical quarks are paired with auxiliary quarks in unphysical "isospin" doublets and a decoupling of the auxiliary quarks by mass reweighting.
↳ hep-lathep-phnucl-thPoS(2019)·10 citations
13
Evading the model sign problem in the PNJL model with repulsive vector-type interaction via path optimization
Akira Ohnishi🇯🇵 · Yuto Mori🇯🇵 · Kouji Kashiwa🇯🇵
We discuss the sign problem in the Polyakov loop extended Nambu--Jona-Lasinio model with repulsive vector-type interaction by using the path optimization method. In this model, both of the Polyakov loop and the vector-type interaction cause the model sign problem, and several prescriptions have been utilized even in the mean field treatment. In the path optimization method, integration variables are complexified and the integration path (manifold) is optimized to evade the sign problem, or equivalently to enhance the average phase factor. Within the homogeneous field ansatz, the path is optimized by using the feedforward neural network. We find that the assumptions adopted in previous works, $Re A_{8} ≃ 0$ and $Re ω ≃ 0$ , can be justified from the Monte-Carlo configurations sampled on the optimized path. We also derive the Euler-Lagrange equation for the optimal path to satisfy. The two optimized paths, the solution of the Euler-Lagrange equation and the variationally optimized path, agree with each other in the region with large statistical weight.
↳ hep-lathep-phnucl-thPoS(2019)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE