Nuclear Theory·nucl-th

Tuesday·April 2, 2019

23 papers—13 primary·10 cross-listed

01
[Submitted on 28 Mar 2019]
Longitudinal spin polarization in a thermal model
Wojciech Florkowski🇵🇱 · Avdhesh Kumar🇵🇱 · Radoslaw Ryblewski🇵🇱 · Aleksas Mazeliauskas🇨🇭
We use a thermal model with single freeze-out to determine longitudinal polarization of $Λ$ hyperons emitted from a hot and rotating hadronic medium. We consider the top RHIC energies and use the model parameters determined in the previous analyses of particle spectra and elliptic flow. Using a direct connection between the spin polarization tensor and thermal vorticity, we reproduce earlier results which indicate a quadrupole structure of the longitudinal component of the polarization three-vector with an opposite sign compared to that found in the experiment. We further use only the spatial components of the thermal vorticity in the laboratory system to define polarization and show that this leads to the correct sign and magnitude of the quadrupole structure. This procedure resembles a non-relativistic connection between the polarization three-vector and vorticity employed in other works. In general, our results bring further evidence that the spin polarization dynamics in heavy-ion collisions may be not directly related to the thermal vorticity. The additional material explains the construction of the hydrodynamicaly consistent gradients of fluid velocity and temperature in thermal models with the help of the perfect-fluid equations of motion.
Comments:
11 pages, 6 figures, hydrodynamically consistent temperature gradients included in the definition of thermal vorticity at freeze-out, an author added
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1904.00002 [pdf]
PRC(2019)·107 citations
02
[Submitted on 29 Mar 2019]
Statistical learnability of nuclear masses
Andrea Idini
After more than 80 years from the seminal work of Weizsäcker and the liquid drop model of the atomic nucleus, deviations from experiments of mass models ( $\sim$ MeV) are orders of magnitude larger than experimental errors ( $≲$ keV). Predicting the mass of atomic nuclei with precision is extremely challenging. This is due to the non--trivial many--body interplay of protons and neutrons in nuclei, and the complex nature of the nuclear strong force. Statistical theory of learning will be used to provide bounds to the prediction errors of model trained with a finite data set. These bounds are validated with neural network calculations, and compared with state of the art mass models. Therefore, it will be argued that the nuclear structure models investigating ground state properties explore a system on the limit of the knowledgeable, as defined by the statistical theory of learning.
Subjects:
Nuclear Theory (nucl-th); cond-mat.dis-nn (cond-mat.dis-nn); Machine Learning (cs.LG)
arXiv:
1904.00057 [pdf]
PRResearch(2020)·7 citations
03
[Submitted on 29 Mar 2019]
Extraction of the Heavy-Quark Potential from Bottomonium Observables in Heavy-Ion Collisions
Xiaojian Du🇺🇸 · Shuai Y.F. Liu🇺🇸 · Ralf Rapp🇺🇸
The in-medium color potential is a fundamental quantity for understanding the properties of the strongly coupled quark-gluon plasma (sQGP). Open and hidden heavy-flavor (HF) production in ultrarelativistic heavy-ion collisions (URHICs) has been found to be a sensitive probe of this potential. Here we utilize a previously developed quarkonium transport approach in combination with insights from open HF diffusion to extract the color-singlet potential from experimental results on $Υ$ production in URHICs. Starting from a parameterized trial potential, we evaluate the $Υ$ transport parameters and conduct systematic fits to available data for the centrality dependence of ground and excited states at RHIC and the LHC. The best fits and their statistical significance are converted into a temperature-dependent potential. Including nonperturbative effects in the dissociation rate guided from open HF phenomenology, we extract a rather strongly coupled potential with substantial remnants of the long-range confining force in the QGP.
Comments:
8 pages, 15 figures; version accepted for publication in PLB
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1904.00113 [pdf]
PLB(2019)·41 citations
04
[Submitted on 30 Mar 2019]
Transport approaches for the Description of Intermediate-Energy Heavy-Ion Collisions
Jun Xu🇨🇳
The transport approach is a useful tool to study dynamics of non-equilibrium systems. For heavy-ion collisions at intermediate energies, where both the smooth nucleon potential and the hard-core nucleon-nucleon collision are important, the dynamics are properly described by two families of transport models, i.e., the Boltzmann-Uehling-Uhlenbeck approach and the quantum molecular dynamics approach. These transport models have been extensively used to extract valuable information of the nuclear equation of state, the nuclear symmetry energy, and microscopic nuclear interactions from intermediate-energy heavy-ion collision experiments. On the other hand, there do exist deviations on the predications and conclusions from different transport models. Efforts on the transport code evaluation project are devoted in order to understand the model dependence of transport simulations and well control the main ingredients, such as the initialization, the mean-field potential, the nucleon-nucleon collision, etc. A new era of accurately extracting nuclear interactions from transport model studies is foreseen.
Comments:
57 pages, 36 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1904.00131 [pdf]
PPNP(2019)·79 citations
05
[Submitted on 31 Mar 2019]
Production of the exotic neutron-deficient isotopes near N, Z = 50 in multinucleon transfer reactions
Xinxin Xu · Gen Zhang · Jingjing Li · Bing Li · Cheikh A. T. Sokhna · Xinrui Zhang · Xiuxiu Yang · Shihui Cheng · Yuhai Zhang · Zhishuai Ge · Cheng LiZhong Liu · Fengshou Zhang
The multinucleon transfer reaction in the collisions of $^{40}$ Ca+ $^{124}$ Sn at $E_{c.m.} = 128.5$ MeV is investigated by using the improved quantum molecular dynamics model. The measured angular distributions and isotopic distributions of the products are reproduced reasonably well by the calculations. The multinucleon transfer reactions of $^{40}$ Ca+ $^{112}$ Sn, $^{58}$ Ni+ $^{112}$ Sn, $^{106}$ Cd+ $^{112}$ Sn, and $^{48}$ Ca+ $^{112}$ Sn are also studied. It shows that the combinations of neutron-deficient projectile and target are advantageous to produce the exotic neutron-deficient nuclei near $N, Z$ = 50. The charged particles emission plays an important role at small impact parameters in the deexcitation processes of the system. The production cross sections of the exotic neutron-deficient nuclei in multinucleon transfer reactions are much larger than those measured in the fragmentation and fusion-evaporation reactions. Several new neutron-deficient nuclei can be produced in $^{106}$ Cd+ $^{112}$ Sn reaction. The corresponding production cross sections for the new neutron-deficient nuclei, $^{101, 102}$ Sb, $^{103}$ Te, and $^{106, 107}$ I, are 2.0 nb, 4.1 nb, 6.5 nb, 0.4 $μ$ b and 1.0 $μ$ b, respectively.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1904.00398 [pdf]
CPC(2019)·6 citations
06
[Submitted on 31 Mar 2019]
Excited $B_{c}$ States via Continuum QCD
Lei Chang🇨🇳 · Muyang Chen🇨🇳 · Yu-xin Liu🇨🇳
We study the most recently observed excited $B_{c}$ states with the Dyson-Schwinger equation and the Bethe-Salpeter equation approach of continuum QCD. The obtained $M_{B_{c}^{+} (2 S)} = 6.813 (16) GeV$ , $M_{B_{c}^{*+} (2 S)} = 6.841 (18) GeV$ and the mass splitting $M_{B_{c}^{+} (2 S)} - M_{B_{c}^{*+} (2 S)}^{rec} \approx 0.039 GeV$ agree with the observations very well. Moreover we predict the leptonic decay constant $f_{B_{c}^{+} (2 S)} = - 0.165 (10) GeV$ , $f_{B_{c}^{*+} (2 S)} = - 0.161 (7) GeV$ respectively.
Comments:
5 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1904.00399 [pdf]
PRD(2020)·17 citations
07
[Submitted on 31 Mar 2019]
Introduction to the transverse-momentum-weighted technique in the twist-3 collinear factorization approach
Hongxi Xing🇨🇳 · Shinsuke Yoshida🇨🇳
The twist-3 collinear factorization framework has drawn much attention in recent decades as a successful approach in describing the data for single spin asymmetries (SSAs). Many SSAs data have been experimentally accumulated in a variety of energies since the first measurement was done in late 70s and it is expected that the future experiments like Electron-Ion collider will provide us with more data. In order to perform a consistent and precise description of the data taken in different kinematic regimes, the scale evolution of the collinear twist-3 functions and the perturbative higher order hard part coefficients are mandatory. In this paper, we introduce the techniques for next-to-leading order (NLO) calculation of transverse-momentum-weighted SSAs, which can be served as a useful tool to derive the QCD evolution equation for twist-3 functions, and to verify the QCD collinear factorization for twist-3 observables at NLO, as well as to obtain the finite NLO hard part coefficients.
Comments:
15 pages, 4 figures, invited review article for the special issue "Transverse Momentum Dependent Observables from Low to High Energy: Factorization, Evolution, and Global Analyses" of the journal "Advances in High Energy Physics", accepted for publication
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1904.00416 [pdf]
Adv.High Energy Phys.(2019)·2 citations
08
[Submitted on 28 Mar 2019]
$^{93 m}$ Mo isomer depletion via beam-based nuclear excitation by electron capture
Yuanbin Wu · Christoph H. Keitel · Adriana Pálffy
A recent nuclear physics experiment [C. J. Chiara {\it et al.}, Nature (London) {\bf 554}, 216 (2018)] reports the first direct observation of nuclear excitation by electron capture (NEEC) in the depletion of the $^{93 m}$ Mo isomer. The experiment used a beam-based setup in which Mo highly charged ions with nuclei in the isomeric state $^{93 m}$ Mo at 2.4 MeV excitation energy were slowed down in a solid-state target. In this process, nuclear excitation to a higher triggering level led to isomer depletion. The reported excitation probability $P_{exc} = 0.01$ was solely attributed to the so-far unobserved process of NEEC in lack of a different known channel of comparable efficiency. In this work, we investigate theoretically the beam-based setup and calculate excitation rates via NEEC using state-of-the-art atomic structure and ion stopping power models. For all scenarios, our results disagree with the experimental data by approximately nine orders of magnitude. This stands in conflict with the conclusion that NEEC was the excitation mechanism behind the observed depletion rate.
Comments:
6 pages, 3 figures; minor modifications made; accepted for publication in Physical Review Letters
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1904.00809 [pdf]
PRL(2019)·41 citations
09
[Submitted on 1 Apr 2019]
Universal physics of bound states of a few charged particles
C. H. Schmickler🇩🇪 · H.-W. Hammer🇩🇪 · A. G. Volosniev🇩🇪
We study few-body bound states of charged particles subject to attractive zero-range/short-range plus repulsive Coulomb interparticle forces. The characteristic length scales of the system at zero energy are set by the Coulomb length scale $D$ and the Coulomb-modified effective range $r_{eff}$ . We study shallow bound states of charged particles with $D ≫ r_{eff}$ and show that these systems obey universal scaling laws different from neutral particles. An accurate description of these states requires both the Coulomb-modified scattering length and the effective range unless the Coulomb interaction is very weak ( $D \to \infty$ ). Our findings are relevant for bound states whose spatial extent is significantly larger than the range of the attractive potential. These states enjoy universality -- their character is independent of the shape of the short-range potential.
Comments:
8 pages, 6 figures, extended discussion, results unchanged, to appear in Phys. Lett. B
Subjects:
Nuclear Theory (nucl-th); cond-mat.other (cond-mat.other); Strongly Correlated Electrons (cond-mat.str-el)
arXiv:
1904.00913 [pdf]
PLB(2019)·16 citations
10
[Submitted on 1 Apr 2019]
$Ab initio$ constraints on thermal effects of the nuclear equation of state
Arianna Carbone · Achim Schwenk
We exploit the many-body self-consistent Green's function method to analyze finite-temperature properties of infinite nuclear matter and to explore the behavior of the thermal index used to simulate thermal effects in equations of state for astrophysical applications. We show how the thermal index is both density and temperature dependent, unlike often considered, and we provide an error estimate based on our $ab initio$ calculations. The inclusion of many-body forces is found to be critical for the density dependence of the thermal index. We also compare our results to a parametrization in terms of the density dependence of the nucleon effective mass. Our study questions the validity of predictions made for the gravitational-wave signal from neutron-star merger simulations with a constant thermal index.
Comments:
11 pages, 7 figures, added references
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
arXiv:
1904.00924 [pdf]
PRC(2019)·79 citations
11
[Submitted on 1 Apr 2019]
Comment on "Is a Trineutron Resonance Lower in Energy than a Tetraneutron Resonance?" [arXiv:1612.01502]
A. Deltuva🇱🇹 · R. Lazauskas🇫🇷
The quantum Monte Carlo study [S. Gandolfi, H.-W. Hammer, P. Klos, J. E. Lynn, and A. Schwenk, Phys. Rev. Lett. {\bf 118}, 232501 (2017), arXiv:1612.01502] of few-neutron resonant states provided results incompatible with rigorous few-body calculations. In this Comment we point out serious shortcomings in the work by Gandolfi et al, leading to misinterpretation of unbound few-body systems.
Comments:
1 figure
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1904.00925 [pdf]
PRL(2019)·21 citations
12
[Submitted on 1 Apr 2019]
Novel scheme for parametrizing the chemical freeze-out surface in Heavy Ion Collision Experiments
Sumana Bhattacharyya🇮🇳 · Deeptak Biswas🇮🇳 · Sanjay K. Ghosh🇮🇳 · Rajarshi Ray🇮🇳 · Pracheta Singha🇮🇳
We introduce a new prescription for obtaining the chemical freeze-out parameters in the heavy-ion collision experiments using the Hadron Resonance Gas model. The scheme is found to reliably estimate the freeze-out parameters and predict the hadron yield ratios, which themselves were never used in the parametrization procedure.
Comments:
7 pages, 10 figures. arXiv admin note: text overlap with arXiv:1911.04828
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1904.00959 [pdf]
PRD(2019)·21 citations
13
[Submitted on 1 Apr 2019]
Halo breakup and the Coulomb-nuclear interference problem
B. Mukeru J. Lubian · Lauro Tomio
The Coulomb-nuclear interference is studied as a function of the projectile ground-state binding energy in the 8Li + 12C and 8Li + 208Pb breakup reactions, by considering an arbitrary range for the 8Li ground-state binding energies {\epsilon}b, varying from the experimental one 2.03 MeV down to 0.01 MeV. Regardless the target mass, we first show that the Coulomb breakup cross section is stronger dependent on {\epsilon}b than the nuclear breakup cross section, due to the long-range nature of the Coulomb forces and to the electromagnetic transition matrix elements. For example, in case of 8Li + 208Pb reaction at Elab = 60MeV, it is found that |{\sigma}_int|\simeq 4\times{\sigma}_nucl $, w hi l e$ {\sigma}_Coul\simeq 35\times{\sigma_nucl}$. This shows clearly that small nuclear contribution in a Coulomb-dominated reaction does not imply insignificant Coulomb-nuclear interference. Such result can be mainly attributed to peripheral interference phenomenon, represented by a function of the binding energy, which determines the peripheral range of nuclear forces, where Coulomb and nuclear forces strongly interfere destructively.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1904.00974 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE