Nuclear Theory·nucl-th

Wednesday·March 25, 2020

12 papers—4 primary·8 cross-listed

01
Propagation of non-linear waves in hot, ideal, and non-extensive quark-gluon plasma
Trambak Bhattacharyya🇷🇺 · Abhik Mukherjee🇷🇺
We study the propagation of energy density perturbation in a hot, ideal quark-gluon medium in which quarks and gluons follow the Tsallis-like momentum distributions. We have observed that a non-extensive MIT bag equation of state obtained with the help of the quantum Tsallis-like distributions gives rise to a breaking wave solution of the equation dictating the evolution of energy density perturbation. However, the breaking of waves is delayed when the value of the Tsallis q parameter and the Tsallis temperature T are higher.
nucl-thhep-exhep-phEPJC(2020)·11 citations
02
High precision studies of soft dipole mode in two-neutron halo nuclei: $^{6}$ He case
L.V. Grigorenko · N.B. Shulgina · M.V. Zhukov
The "soft dipole" E1 strength function is calculated for the transition from the $^{6}$ He $0^{+}$ ground state to the $1^{-}$ continuum $^{4}$ He+ $n$ + $n$ . The calculations were performed within the hyperspherical harmonics formalism. The sensitivity of the results to the $^{6}$ He ground state structure and to final state interactions, are analyzed. The large-basis calculations show the reliably converged results for soft dipole strength function and for momentum correlations of the $^{6} \mbox H e \to^{4}$ He+ $n$ + $n$ dissociation products. Transition mechanisms are analyzed based on the momentum correlations. The comparison with experimental data is provided.
nucl-thPRC(2020)·11 citations
03
Sensitivity of the Mean Field Dynamics to the Spatial Distribution in Nuclear One-body Dissipations
Yong-Zhong Xing · Wei-Cheng Fu · Xiao-Bin Liu · Fei-Ping Lu · Hong-Fei Zhang · Yu-Ming Zheng
Started from the static excited finite atomic nucleus, we have simulated the dynamical propagation of the nucleons using Quantum Molecular Dynamics model (QMD) without the collision term and calculated the Largest Lyapunov Exponent (LLE). The sensitivity of the nonlinear mean field dynamics to the initial conditions, in particular to the initial spatial distribution of the nucleons in certain thermodynamical stable condition, has been confirmed numerically by calculating the LLE defined in the event space. Comparatively, the Lyapunov-like exponent defined in phase space represents more clearly the sensitivity of the nonlinear dynamics to the mechanical stability of the initial conditions within the nuclear reaction time at intermediate energies. These conclusions are not only helpful for us to understand more deeply the mechanism of the nuclear reaction dynamics at intermediate energies, but it is also beneficial for clarifying further the concrete performances of deterministic chaos in the heavy-ion collisions.
nucl-thNPA(2020)·1 citation
04
Properties of spherical and deformed nuclei using regularized pseudopotentials in nuclear DFT
K. Bennaceur🇫🇷 · J. Dobaczewski🇬🇧 · T. Haverinen🇫🇮 · M. Kortelainen🇫🇮
We developed new parameterizations of local regularized finite-range pseudopotentials up to next-to-next-to-next-to-leading order (N3LO), used as generators of nuclear density functionals. When supplemented with zero-range spin-orbit and density-dependent terms, they provide a correct single-reference description of binding energies and radii of spherical and deformed nuclei. We compared the obtained results to experimental data and discussed benchmarks against the standard well-established Gogny D1S functional.
nucl-thJ.Phys.G(2020)·13 citations
05
The dual properties of chiral and isospin asymmetric dense quark matter formed of two-color quarks
T. G. Khunjua🇺🇸 · K. G. Klimenko🇷🇺 · R. N. Zhokhov🇷🇺
In this paper the phase structure of dense baryon matter composed of $u$ and $d$ quarks with two colors has been investigated in the presence of baryon $μ_{B}$ , isospin $μ_{I}$ and chiral isospin $μ_{I 5}$ chemical potentials in the framework of Nambu--Jona-Lasinio model. In the chiral limit, it has been shown that the duality between phases with spontaneous chiral symmetry breaking and condensation of charged pions, found in the three color case, remains valid in the two color case. In addition, it has been shown that there are two more dualities in the phase diagram in two color case, namely (as in the case with $μ_{I 5} = 0$ ), at $μ_{I 5} \neq = 0$ the general $(μ, μ_{I}, μ_{I 5})$ -phase portrait of the model has dual symmetry between the phase with condensation of charged pions and the phase with diquark condensation. This duality stays exact even in the physical point, $m_{0} \neq = 0$ . And at $m_{0} = 0$ the $(μ, μ_{I}, μ_{I 5})$ -phase portrait becomes even more symmetrical, since dual symmetry between phases with spontaneous chiral symmetry breaking and diquark condensation appears. It is shown that due to the dualities the phase diagram is extremely symmetric and has interlacing structure. One can show that the phase portrait of two-color NJL model can be obtained just by duality properties from the results of investigations of three-color NJL model (it was noticed only after the numerical calculations have been performed). Three-color case shares only one duality of the two color one, and one can only see a facet of this enormously symmetric picture in the case of three colors. Using dualities only, it is possible to show that there are no mixed phases (phases with two non-zero condensates). This prediction of dualities is of great use, because for sure it can be shown by the direct calculations but it would be enormously more complicated and time-consuming numerically.
↳ hep-phhep-thnucl-thJHEP(2020)·28 citations
06
Lattice QCD and baryon-baryon interactions: HAL QCD method
Sinya Aoki🇯🇵 · Takumi Doi🇯🇵
In this article, we review the HAL QCD method to investigate baryon-baryon interactions such as nuclear forces in lattice QCD. We first explain our strategy in detail to investigate baryon-baryon interactions by defining potentials in field theories such as QCD. We introduce the Nambu-Bethe-Salpeter (NBS) wave functions in QCD for two baryons below the inelastic threshold. We then define the potential from NBS wave functions in terms of the derivative expansion, which is shown to reproduce the scattering phase shifts correctly below the inelastic threshold. Using this definition, we formulate a method to extract the potential in lattice QCD. Secondly, we discuss pros and cons of the HAL QCD method, by comparing it with the conventional method, where one directly extracts the scattering phase shifts from the finite volume energies through the Lüscher's formula. We give several theoretical and numerical evidences that the conventional method combined with the naive plateau fitting for the finite volume energies in the literature so far fails to work on baryon-baryon interactions due to contaminations of elastic excited states. On the other hand, we show that such a serious problem can be avoided in the HAL QCD method by defining the potential in an energy-independent way. We also discuss systematics of the HAL QCD method, in particular errors associated with a truncation of the derivative expansion. Thirdly, we present several results obtained from the HAL QCD method, which include (central) nuclear force, tensor force, spin-orbital force, and three nucleon force. We finally show the latest results calculated at the nearly physical pion mass, $m_{π} ≃ 146$ MeV, including hyperon forces which lead to form $ΩΩ$ and $N Ω$ dibaryons.
↳ hep-lathep-phnucl-thFront.in Phys.(2020)·81 citations
07
Classifying Pole of Amplitude Using Deep Neural Network
Denny Lane B. Sombillo🇵🇭 · Yoichi Ikeda🇯🇵 · Toru Sato🇯🇵 · Atsushi Hosaka🇯🇵
Most of exotic resonances observed in the past decade appear as peak structure near some threshold. These near-threshold phenomena can be interpreted as genuine resonant states or enhanced threshold cusps. Apparently, there is no straightforward way of distinguishing the two structures. In this work, we employ the strength of deep feed-forward neural network in classifying objects with almost similar features. We construct a neural network model with scattering amplitude as input and nature of pole causing the enhancement as output. The training data is generated by an S-matrix satisfying the unitarity and analyticity requirements. Using the separable potential model, we generate a validation data set to measure the network's predictive power. We find that our trained neural network model gives high accuracy when the cut-off parameter of the validation data is within $400$ - $800 \mbox M e V$ . As a final test, we use the Nijmegen partial wave and potential models for nucleon-nucleon scattering and show that the network gives the correct nature of pole.
↳ hep-phhep-exnucl-exnucl-thPRD(2020)·29 citations
08
Iterative Bayesian Monte Carlo for nuclear data evaluation
E. Alhassan · D. Rochman · A. Vasiliev · M. Wohlmuther · M. Hursin · A.J. Koning · H. Ferroukhi
In this work, we explore the use of an iterative Bayesian Monte Carlo (IBM) procedure for nuclear data evaluation within a Talys Evaluated Nuclear data Library (TENDL) framework. In order to identify the model and parameter combinations that reproduce selected experimental data, different physical models implemented within the TALYS code, were sampled and varied simultaneously to produce random input files with unique model combinations. All the models considered were assumed to be equal a priori. Parameters to these models were then varied simultaneously using the TALYS code system to produce a set of random ENDF files which were processed into x-y tables for comparison with selected experimental data from the EXFOR database within a Bayesian framework. To improve our fit to experimental data, we iteratively update our 'best' file - the file that maximises the likelihood function - by re-sampling model parameters around this file. The method proposed has been applied for the evaluation of p+Cd-111 and Co-59 between 1 - 100 MeV incident energy region. Finally, the adjusted files were compared with experimental data from the EXFOR database as well as with evaluations from the TENDL-2017 and JENDL-4.0/HE nuclear data libraries.
↳ physics.data-annucl-thNucl.Sci.Tech.(2022)·18 citations
09
Four-jet production via double parton scattering in $p A$ collisions at the LHC
B. Blok (Technion)🇮🇱 · F.A. Ceccopieri (Technion)🇮🇱
We present predictions for the double parton scattering (DPS) four-jet production cross sections in $p A$ collisions at the LHC. Relying on the experimental capabilities to correlate centrality with impact parameter $B$ of the proton-nucleus collision, we discuss a strategy to extract the double parton scattering contributions in $p A$ collisions, which gives direct access to double parton distribution in the nucleon. We show that the production cross sections via DPS of four jets, out of which two may be light- or heavy-quark jets, are large enough to allow the method to be used already with data accumulated in 2016 $p A$ run.
↳ hep-phhep-exnucl-exnucl-thPRD(2020)·2 citations
10
Actinide and lanthanide molecules to search for strong CP-violation
Leonid V. Skripnikov🇷🇺 · Nikolai S. Mosyagin🇷🇺 · Anatoly V. Titov🇷🇺 · Victor V. Flambaum🇦🇺
The existence of the fundamental CP-violating interactions inside the nucleus leads to the existence of the nuclear Schiff moment. The Schiff moment potential corresponds to the electric field localized inside the nucleus and directed along its spin. This field can interact with electrons of an atom and induce the permanent electric dipole moment (EDM) of the whole system. The Schiff moment and corresponding electric field are enhanced in the nuclei with the octupole deformation leading to the enhanced atomic EDM. There is also a few-order enhancement of the T,P-violating effects in molecules due to the existence of energetically close levels of opposite parity. We study the Schiff moment enhancement in the class of diatomic molecules with octupole-deformed lanthanide and actinide nuclei: $^{227}$ AcF, $^{227}$ AcN, $^{227}$ AcO $^{+}$ , $^{229}$ ThO, $^{153}$ EuO $^{+}$ and $^{153}$ EuN. Projecting the existing experimental achievements to measure EDM in diamagnetic molecules with spherical nucleus ( $^{205}$ TlF) to the considered systems one can expect a very high sensitivity to the quantum chromodynamics parameter $θ ˉ$ and other hadronic CP-violation parameters surpassing the current best limits by several orders of magnitude. It can have a dramatic impact on the modern understanding of the nature of CP-violating fundamental interactions.
↳ physics.atom-phhep-phnucl-thphysics.chem-phPhys.Chem.Chem.Phys.(2020)·32 citations
11
Generalizing the relativistic quantization condition to include all three-pion isospin channels
Maxwell T. Hansen🇨🇭 · Fernando Romero-López🇪🇸 · Stephen R. Sharpe🇺🇸
We present a generalization of the relativistic, finite-volume, three-particle quantization condition for non-identical pions in isosymmetric QCD. The resulting formalism allows one to use discrete finite-volume energies, determined using lattice QCD, to constrain scattering amplitudes for all possible values of two- and three-pion isospin. As for the case of identical pions considered previously, the result splits into two steps: The first defines a non-perturbative function with roots equal to the allowed energies, $E_{n} (L)$ , in a given cubic volume with side-length $L$ . This function depends on an intermediate three-body quantity, denoted $K_{df, 3}$ , which can thus be constrained from lattice QCD input. The second step is a set of integral equations relating $K_{df, 3}$ to the physical scattering amplitude, $M_{3}$ . Both of the key relations, $E_{n} (L) \leftrightarrow K_{df, 3}$ and $K_{df, 3} \leftrightarrow M_{3}$ , are shown to be block-diagonal in the basis of definite three-pion isospin, $I_{π π π}$ , so that one in fact recovers four independent relations, corresponding to $I_{π π π} = 0, 1, 2, 3$ . We also provide the generalized threshold expansion of $K_{df, 3}$ for all channels, as well as parameterizations for all three-pion resonances present for $I_{π π π} = 0$ and $I_{π π π} = 1$ . As an example of the utility of the generalized formalism, we present a toy implementation of the quantization condition for $I_{π π π} = 0$ , focusing on the quantum numbers of the $ω$ and $h_{1}$ resonances.
↳ hep-lathep-phnucl-thJHEP(2020)·99 citations
12
QCD Challenges from pp to A-A Collisions
J. Adolfsson🇸🇪 · A. Andronic🇩🇪 · C. Bierlich🇸🇪 · P. Bozek🇵🇱 · S. Chakraborty🇸🇪 · P. Christiansen🇸🇪 · D. D. Chinellato🇧🇷 · R. J. Fries🇺🇸 · G. Gustafson🇸🇪 · H. van Hees🇩🇪 · P. M. Jacobs🇺🇸 · D. J. Kim🇫🇮 and 28 other authors
This paper is a write-up of the ideas that were presented, developed and discussed at the third International Workshop on QCD Challenges from pp to A-A, which took place in August 2019 in Lund, Sweden. The goal of the workshop was to focus on some of the open questions in the field and try to come up with concrete suggestions for how to make progress on both the experimental and theoretical sides. The paper gives a brief introduction to each topic and then summarizes the primary results.
↳ hep-phhep-exnucl-exnucl-thEPJA(2020)·38 citations

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