Nuclear Theory·nucl-th

Tuesday·April 2, 2019

23 papers—13 primary·10 cross-listed

01
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.
nucl-thhep-phPRC(2019)·107 citations
02
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.
nucl-thcond-mat.dis-nncs.LGPRResearch(2020)·7 citations
03
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.
nucl-thhep-phnucl-exPLB(2019)·41 citations
04
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.
nucl-thnucl-exPPNP(2019)·79 citations
05
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.
nucl-thCPC(2019)·6 citations
06
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.
nucl-thhep-phPRD(2020)·17 citations
07
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.
hep-phnucl-exnucl-thAdv.High Energy Phys.(2019)·2 citations
08
$^{93 m}$ 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.
nucl-thPRL(2019)·41 citations
09
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.
nucl-thcond-mat.othercond-mat.str-elPLB(2019)·16 citations
10
$Ab initio$ 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.
nucl-thastro-ph.HEgr-qcPRC(2019)·79 citations
11
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.
nucl-thnucl-exPRL(2019)·21 citations
12
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.
nucl-thhep-phPRD(2019)·21 citations
13
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.
nucl-th0 citations
14
Nuclear Parton Distributions from Lepton-Nucleus Scattering and the Impact of an Electron-Ion Collider
Rabah Abdul Khalek🇳🇱 · Jacob J. Ethier🇳🇱 · Juan Rojo🇳🇱
We present a first determination of the nuclear parton distribution functions (nPDF) based on the NNPDF methodology: nNNPDF1.0. This analysis is based on neutral-current deep-inelastic structure function data and is performed up to NNLO in QCD calculations with heavy quark mass effects. For the first time in the NNPDF fits, the $χ^{2}$ minimization is achieved using stochastic gradient descent with reverse-mode automatic differentiation (backpropagation). We validate the robustness of the fitting methodology through closure tests, assess the perturbative stability of the resulting nPDFs, and compare them with other recent analyses. The nNNPDF1.0 distributions satisfy the boundary condition whereby the NNPDF3.1 proton PDF central values and uncertainties are reproduced at $A = 1$ , which introduces important constraints particularly for low- $A$ nuclei. We also investigate the information that would be provided by an Electron-Ion Collider (EIC), finding that EIC measurements would significantly constrain the nPDFs down to $x ≃ 5 \times 1 0^{- 4}$ . Our results represent the first-ever nPDF determination obtained using a Monte Carlo methodology consistent with that of state-of-the-art proton PDF fits, and provide the foundation for a subsequent global nPDF analyses including also proton-nucleus data.
↳ hep-phhep-exnucl-exnucl-thEPJC(2019)·147 citations
15
Charting the coming synergy between lattice QCD and high-energy phenomenology
T. J. Hobbs🇺🇸 · Bo-Ting Wang🇺🇸 · Pavel M. Nadolsky🇺🇸 · Fredrick I. Olness🇺🇸
Building upon the PDFSense framework developed in Ref. [1], we perform a comprehensive analysis of the sensitivity of present and future high-energy data to a number of quantities commonly evaluated in lattice gauge theory, with a particular focus on the integrated Mellin moments of nucleon parton distribution functions (PDFs), such as $⟨ x ⟩_{u^{+} - d^{+}}$ and $⟨ x ⟩_{g}$ , as well as $x$ -dependent quark quasi-distributions -- in particular, that of the isovector combination. Our results demonstrate the potential for lattice calculations and phenomenological quark distributions informed by high-energy experimental data to cooperatively improve the picture of the nucleon's collinear structure. This will increasingly be the case as computational resources for lattice calculations further expand, and QCD global analyses continue to grow in sophistication. Our sensitivity analysis suggests that a future lepton-hadron collider would be especially instrumental in providing phenomenological constraints to lattice observables.
↳ hep-phhep-exhep-latnucl-thPRD(2019)·45 citations
16
Meson-meson scattering lengths at maximum isospin from lattice QCD
Christopher Helmes🇩🇪 · Christian Jost🇩🇪 · Bastian Knippschild🇩🇪 · Bartosz Kostrzewa🇩🇪 · Liuming Liu🇨🇳 · Ferenc Pittler🇩🇪 · Carsten Urbach🇩🇪 · Markus Werner🇩🇪
We summarize our lattice QCD determinations of the pion-pion, pion-kaon and kaon-kaon s-wave scattering lengths at maximal isospin with a particular focus on the extrapolation to the physical point and the usage of next-to-leading order chiral perturbation theory to do so. We employ data at three values of the lattice spacing and pion masses ranging from around 230 MeV to around 450 MeV, applying Luescher's finite volume method to compute the scattering lengths. We find that leading order chiral perturbation theory is surprisingly close to our data even in the kaon-kaon case for our entire range of pion masses.
↳ hep-lathep-phnucl-thPoS(2019)·5 citations
17
Anisotropic pressure induced by finite-size effects in SU(3) Yang-Mills theory
Masakiyo Kitazawa🇯🇵 · Sylvain Mogliacci🇿🇦 · Isobel Kolbé🇿🇦 · W. A. Horowitz🇿🇦
We study the pressure anisotropy in anisotropic finite-size systems in SU(3) Yang-Mills theory at nonzero temperature. Lattice simulations are performed on lattices with anisotropic spatial volumes with periodic boundary conditions. The energy-momentum tensor defined through the gradient flow is used for the analysis of the stress tensor on the lattice. We find that a clear finite-size effect in the pressure anisotropy is observed only at a significantly shorter spatial extent compared with the free scalar theory, even when accounting for a rather large mass in the latter.
↳ hep-lathep-phnucl-thPRD(2019)·40 citations
18
The non-equilibrium attractor: Beyond hydrodynamics
Michael Strickland🇺🇸
The quark-gluon plasma created in heavy-ion collisions is not in local thermal equilibrium at early times. Despite this, dissipative hydrodynamics describes the evolution of the energy-momentum tensor quite well after only roughly 0.5 - 1 fm/c. This can be understood using the concept of a non-equilibrium dynamical attractor. The attractor is a uniquely identifiable solution to the dynamical equations to which all solutions are drawn as the system evolves. Once solutions collapse onto the non-equilibrium attractor they are ``pseudo-thermalized'' in the sense that they have lost information about the precise initial conditions used, but are not yet in exact local thermal equilibrium. Here I review recent work which demonstrates that there exists a non-equilibrium attractor in full kinetic theory models which goes beyond the usual low-order momentum moments considered in hydrodynamical treatments.
↳ hep-phnucl-thActa Phys.Polon.B(2019)·6 citations
19
Charmed dibaryon resonances in the potential quark model
Makoto Oka🇯🇵 · Saori Maeda🇯🇵 · Yan-Rui Liu🇨🇳
Charmed dibaryon states with the spin-parity $J^{π} = 0^{+}$ , $1^{+}$ , and $2^{+}$ are predicted for the two-body $Y_{c} N$ ( $= Λ_{c}$ , $Σ_{c}$ , or $Σ_{c}^{*}$ ) systems. We employ the complex scaling method for the coupled channel Hamiltonian with the $Y_{c} N$ -CTNN potentials, which were proposed in our previous study. We find four sharp resonance states near the $Σ_{c} N$ and $Σ_{c}^{*} N$ thresholds. From the analysis of the binding energies of partial channel systems, we conclude that these resonance states are Feshbach resonances. We compare the results with the $Y_{c} N$ resonance states in the heavy quark limit, where the $Σ_{c} N$ and $Σ_{c}^{*} N$ thresholds are degenerate, and find that they form two pairs of the heavy-quark doublets in agreement with the heavy quark spin symmetry.
↳ hep-phnucl-thInt.J.Mod.Phys.Conf.Ser.(2019)·8 citations
20
Heavy quark spin multiplet structure of $P_{c} (4312)$ , $P_{c} (4440)$ , and $P_{c} (4457)$
Yuki Shimizu🇯🇵 · Yasuhiro Yamaguchi🇯🇵 · Masayasu Harada🇯🇵
Very recently, the LHCb collaboration has reported the new result about the hidden-charm pentaquarks: $P_{c} (4312)$ near the $D ˉ Σ_{c}$ threshold, and $P_{c} (4440)$ and $P_{c} (4457)$ near $D ˉ^{*} Σ_{c}$ threshold. We study the heavy quark spin (HQS) multiplet structures of these newly $P_{c}$ pentaquarks under the heavy quark spin symmetry based on the hadronic molecular picture. We point out that $P_{c} (4312)$ is the $J^{P} = 1/ 2^{-}$ member of an HQS triplet, and $P_{c} (4440)$ and $P_{c} (4457)$ are the $J^{P} = 3/ 2^{-}$ member of the HQS triplet and an HQS singlet with $J^{P} = 3/ 2^{-}$ . Namely, the $P_{c} (4312)$ and one of $P_{c} (4440)$ and $P_{c} (4457)$ belong to an HQS triplet. The HQS multiplet structure predicts the existence of $J^{P} = 5/ 2^{-}$ state near $D ˉ^{*} Σ_{c}^{*}$ threshold.
↳ hep-phnucl-th67 citations
21
Nature of the D_0 meson in the D pi scattering with chiral symmetry
Takumi Sugiura🇯🇵 · Tetsuo Hyodo🇯🇵
We study the nature of the scalar D_0 meson from the viewpoint of chiral symmetry. With the linear representation of chiral symmetry, we construct the D pi scattering amplitude satisfying the chiral low-energy theorem, in which the D_0 meson appears as an s-wave resonance. We show that the properties of the D_0 meson can be successfully reproduced as the chiral partner of the D meson coupled with the D pi scattering states. At the same time, we find that the spectral function and the pole position of D_0 are not very sensitive to the reduction of the chiral condensate, indicating the importance of the dressing of the bare state by the D pi molecular component.
↳ hep-phnucl-thPRC(2019)·3 citations
22
Unequal rapidity correlators in the dilute limit of JIMWLK
Tuomas Lappi🇫🇮 · Andrecia Ramnath🇫🇮
We study unequal rapidity correlators in the stochastic Langevin picture of Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner (JIMWLK) evolution in the Color Glass Condensate effective field theory. We discuss a diagrammatic interpretation of the long-range correlators. By separately evolving the Wilson lines in the direct and complex conjugate amplitudes, we use the formalism to study two-particle production at large rapidity separations. We show that the evolution between the rapidities of the two produced particles can be expressed as a linear equation, even in the full nonlinear limit. We also show how the Langevin formalism for two-particle correlations reduces to a BFKL picture in the dilute limit and in momentum space, providing an interpretation of BFKL evolution as a stochastic process for color charges.
↳ hep-phnucl-thPRD(2019)·5 citations
23
Complete Matching for Quasi-distribution Functions in Large Momentum Effective Theory
Wei Wang🇨🇳 · Jian-Hui Zhang🇩🇪 · Shuai Zhao🇨🇳 · Ruilin Zhu🇨🇳
We complete the procedure of extracting parton distribution functions (PDFs) using large momentum effective theory (LaMET) at leading power accuracy in the hadron momentum. We derive a general factorization formula for the quasi PDFs in the presence of mixing, and give the corresponding hard matching kernel at $O (α_{s})$ , both for the unpolarized and for the polarized quark and gluon quasi-PDFs. Our calculation is performed in a regularization-independent momentum subtraction scheme. The results allow us to match the nonperturbatively renormalized quasi-PDFs to normal PDFs in the presence of mixing, and therefore can be used to extract flavor-singlet quark PDFs as well as gluon PDFs from lattice simulations.
↳ hep-phhep-latnucl-thPRD(2019)·86 citations

Affiliations

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