Nuclear Theory·nucl-th

Tuesday·May 15, 2018

21 papers—10 primary·11 cross-listed

01
S- and p-wave structure of $S = - 1$ meson-baryon scattering in the resonance region
D. Sadasivan🇺🇸 · M. Mai🇺🇸 · M. Doring🇺🇸
We perform a simultaneous analysis of s- and p-waves of the $S = - 1$ meson-baryon scattering amplitude using all low-energy experimental data. For the first time, differential cross section data are included for chiral unitary coupled-channel models. From this model s- and p-wave amplitudes are extracted and we observe both well-known $I (J^{P}) = 0 (1/ 2^{-})$ s-wave states as well as a new $I (J^{P}) = 1 (1/ 2^{+})$ state absent in quark models and lattice QCD results. Multiple statistical and phenomenological tests suggest that, while the data clearly require an $I = 1$ p-wave resonance, the new state just accounts for the absence of the decuplet $Σ (1385) 3/ 2^{+}$ in the model.
nucl-thhep-phnucl-exPLB(2019)·31 citations
02
Electron scattering from a deeply bound nucleon on the light-front
Frank Vera🇺🇸 · Misak M. Sargsian🇺🇸
We calculate the cross section of the electron scattering from a bound nucleon within light-front approximation. The advantage of this approximation is the possibility of systematic account for the off-shell effects which become essential in high energy electro-nuclear processes aimed at probing the nuclear structure at small distances. We derive a new dynamical parameter which allows to control the extent of the "off-shellness" of electron - bound-nucleon electromagnetic current for different regions of momentum transfer and initial light-cone momenta of the bound nucleon. The derived cross section is compared with the results of other approaches in treating the off-shell effects in electron-nucleon scattering.
nucl-thhep-phnucl-exPRC(2018)·3 citations
03
Examination of the $^{22}$ C radius determination with interaction cross sections
T. Nagahisa · W. Horiuchi
A nuclear radius of $^{22}$ C is investigated with the total reaction cross sections at medium- to high-incident energies in order to resolve the radius puzzle in which two recent interaction cross section measurements using $^{1}$ H and $^{12}$ C targets show the quite different radii. The cross sections of $^{22}$ C are calculated consistently for these target nuclei within a reliable microscopic framework, the Glauber theory. To describe appropriately such a reaction involving a spatially extended nucleus, the multiple scattering processes within the Glauber theory are fully taken into account, that is, the multi-dimensional integration in the Glauber amplitude is evaluated using a Monte Carlo technique without recourse to the optical-limit approximation. We discuss the sensitivity of the spatially extended halo tail to the total reaction cross sections. The root-mean-square matter radius obtained in this study is consistent with that extracted from the recent cross section measurement on $^{12}$ C target. We show that the simultaneous reproduction of the two recent measured cross sections is not feasible within this framework.
nucl-thnucl-exPRC(2018)·43 citations
04
Quark mean-field model for nuclear matter with or without bag
Zhen-Yu Zhu🇨🇳 · Ang Li🇨🇳 · Jin-Niu Hu🇨🇳 · Hong Shen🇨🇳
We propose the new quark mean-field bag (QMFB) model by incorporating the bag confinement mechanism in the original quark mean-field model. Nuclear matter and neutron star properties are studied with the QMFB model. For the study of the bag effect, we newly fit 12 parameter sets by reproducing the empirical saturation properties of nuclear matter. Quark confinement is found to be mainly demonstrated by the bag after it is included in the model, instead of the confining potential. For nuclear matter, the bag decreases the binding energy and increases the symmetry energy. For neutron star, the bag affects significantly the radius $R$ of a $1.4 M_{⊙}$ star, with the maximum mass only slightly modified. The bag also has a large suppression effect on the well-accepted $R$ vs $L$ dependence, with $L$ the symmetry energy slope at the saturation density.
nucl-thastro-ph.HEhep-thPRC(2019)·27 citations
05
Non-Bessel-Gaussianity and Flow Harmonic Fine-Splitting
Hadi Mehrabpour🇮🇷 · Seyed Farid Taghavi🇮🇷
Both collision geometry and event-by-event fluctuations are encoded in the experimentally observed flow harmonic distribution $p (v_{n})$ and $2 k$ -particle cumulants $c_{n} {2 k}$ . In the present study, we systematically connect these observables to each other by employing Gram-Charlier A series. We quantify the deviation of $p (v_{n})$ from Bessel-Gaussianity in terms of flow harmonic fine-splitting. Subsequently, we show that the corrected Bessel-Gaussian distribution can fit the simulated data better than the Bessel-Gaussian distribution in the more peripheral collisions. Inspired by Gram-Charlier A series, we introduce a new set of cumulants $q_{n} {2 k}$ that are more natural to study distributions near Bessel-Gaussian. These new cumulants are obtained from $c_{n} {2 k}$ where the collision geometry effect is extracted from it. By exploiting $q_{2} {2 k}$ , we introduce a new set of estimators for averaged ellipticity $v ˉ_{2}$ which are more accurate compared to $v_{2} {2 k}$ for $k > 1$ . As another application of $q_{2} {2 k}$ , we show we are able to restrict the phase space of $v_{2} {4}$ , $v_{2} {6}$ and $v_{2} {8}$ by demanding the consistency of $v ˉ_{2}$ and $v_{2} {2 k}$ with $q_{2} {2 k}$ equation. The allowed phase space is a region such that $v_{2} {4} - v_{2} {6} ≳ 0$ and $12 v_{2} {6} - 11 v_{2} {8} - v_{2} {4} ≳ 0$ , which is compatible with the experimental observations.
nucl-thhep-phnucl-exEPJC(2019)·16 citations
06
Dissociation of heavy quarkonia in an anisotropic hot QCD medium in a Quasi-Particle Model
Mohammad Yousuf Jamal🇮🇳 · Indrani Nilima🇮🇳 · Vinod Chandra🇮🇳 · Vineet Kumar Agotiya🇮🇳
The present article is the follow up work of, Phys.\ Rev.\ D {\bf 94}, 094006 (2016), where we have extended the study of quarkonia dissociation in (momentum) anisotropic hot QCD medium. As evident by the experimentally observed collective flow at RHIC and LHC, the momentum anisotropy is present at almost all the stages after the collision and therefore, it is important to include its effects in the analysis. Employing the in-medium (corrected) potential while considering the anisotropy (both oblate and prolate cases) in the medium, the thermal widths and the binding energies of the heavy quarkonia states (s-wave charmonia and s-wave bottomonia specifically, for radial quantum numbers n = 1 and 2) have been determined. The hot QCD medium effects have been included employing a quasi-particle description. The presence of anisotropy has modified the potential and then the thermal widths and the binding energies of these states in a significant manner. The results show a quite visible shift in the values of dissociation temperatures as compared to the isotropic case. Further, the hot QCD medium interaction effects suppress the dissociation temperature as compared to the case where we consider the medium as a non-interacting ultra-relativistic gas of quarks (anti-quarks) and gluons.
nucl-thPRD(2018)·38 citations
07
Nuclear Astrophysics in the New Era of Multimessenger Astronomy
J. Piekarewicz🇺🇸
Neutron stars are unique cosmic laboratories for the exploration of matter under extreme conditions of density and neutron-proton asymmetry. Due to their enormous dynamic range, neutron stars display a myriad of exotic states of matter that are impossible to recreate under normal laboratory conditions. In these three lectures I will discuss how the strong synergy that has developed between nuclear physics and astrophysics will uncover some of the deepest secrets behind these fascinating objects. In particular, I will highlight the enormous impact that the very first detection of gravitational waves from the binary neutron-star merger GW170817 is having in constraining the composition, structure, and dynamics of neutron stars.
nucl-thastro-ph.SRnucl-ex6 citations
08
DREENA-B framework: first predictions of $R_{AA}$ and $v_{2}$ within dynamical energy loss formalism in evolving QCD medium
Dusan Zigic🇷🇸 · Igor Salom🇷🇸 · Jussi Auvinen🇷🇸 · Marko Djordjevic🇷🇸 · Magdalena Djordjevic🇷🇸
Dynamical energy loss formalism allows generating state-of-the-art suppression predictions in finite size QCD medium, employing a sophisticated model of high- $p_{⊥}$ parton interactions with QGP. We here report a major step of introducing medium evolution in the formalism though $1 + 1 D$ Bjorken (``B'') expansion, while preserving all complex features of the original dynamical energy loss framework. We use this framework to provide joint $R_{AA}$ and $v_{2}$ predictions, for the first time within the dynamical energy loss formalism in evolving QCD medium. The predictions are generated for a wide range of observables, i.e. for all types of probes (both light and heavy) and for all centrality regions in both $P b + P b$ and $X e + X e$ collisions at the LHC. Where experimental data are available, DREENA-B framework leads to a good joint agreement with $v_{2}$ and $R_{AA}$ data. Such agreement is encouraging, i.e. may lead us closer to resolving $v_{2}$ puzzle (difficulty of previous models to jointly explain $R_{AA}$ and $v_{2}$ data), though this still remains to be thoroughly tested by including state-of-the-art medium evolution within DREENA framework. While introducing medium evolution significantly changes $v_{2}$ predictions, $R_{AA}$ predictions remain robust and moreover in a good agreement with the experimental data; $R_{AA}$ observable is therefore suitable for calibrating parton-medium interaction model, independently from the medium evolution. Finally, for heavy flavor, we observe a strikingly similar signature of the dead-cone effect on both $R_{AA}$ and $v_{2}$ - we also provide a simple analytical understanding behind this result. Overall, the results presented here indicate that DREENA framework is a reliable tool for QGP tomography.
nucl-thhep-phPLB(2019)·72 citations
09
Nucleon Excited States from Lattice QCD and Hamiltonian Effective Field Theory
Jia-jun Wu🇦🇺 · Jonathan M. M. Hall🇦🇺 · H. Kamano🇯🇵 · Waseem Kamleh🇦🇺 · T.-S. H. Lee🇺🇸 · Derek B. Leinweber🇦🇺 · Zhan-Wei Liu🇨🇳 · Finn M. Stokes🇦🇺 · Anthony W. Thomas🇦🇺
An approach for relating the nucleon excited states extracted from lattice QCD and the nucleon resonances of experimental data has been developed using the Hamiltonian effective field theory (HEFT) method. By formulating HEFT in the finite volume of the lattice, the eigenstates of the Hamiltonian model can be related to the energy eigenstates observed in Lattice simulations. By taking the infinite-volume limit of HEFT, information from the lattice is linked to experiment. The approach opens a new window for the study of experimentally-observed resonances from the first principles of lattice QCD calculations. With the Hamiltonian approach, one not only describes the spectra of lattice-QCD eigenstates through the eigenvalues of the finite-volume Hamiltonian matrix, but one also learns the composition of the lattice-QCD eigenstates via the eigenvectors of the Hamiltonian matrix. One learns the composition of the states in terms of the meson-baryon basis states considered in formulating the effective field theory. One also learns the composition of the resonances observed in Nature. In this paper, we will focus on recent breakthroughs in our understanding of the structure of the $N^{*} (1535)$ , $N^{*} (1440)$ and $Λ^{*} (1405)$ resonances using this method.
nucl-thhep-lathep-ph2 citations
10
Single-particle spatial dispersion and clusters in nuclei
J.-P. Ebran🇫🇷 · E. Khan🇫🇷 · R.-D Lasseri🇫🇷 · D. Vretenar🇭🇷
The spatial dispersion of the single-nucleon wave functions is analyzed using the self-consistent mean-field framework based on nuclear energy density functionals, and with the harmonic oscillator approximation for the nuclear potential. It is shown that the dispersion depends on the radial quantum number n, but displays only a very weak dependence on the orbital angular momentum. An analytic expression is derived for the localization parameter that explicitly takes into account the radial quantum number of occupied single-nucleon states. The conditions for single-nucleon localization and formation of cluster structures are fulfilled in relatively light nuclei with $A \leq 30$ and $n = 1$ states occupied. Heavier nuclei exhibit the quantum liquid phase of nucleonic matter because occupied levels that originate from $n > 1$ spherical states are largely delocalized. Nevertheless, individual $α$ -like clusters can be formed from valence nucleons filling single-particle levels originating from $n = 1$ spherical mean-field states.
nucl-thPRC(2018)·16 citations

Affiliations

first authorsco-authorsvia INSPIRE