Nuclear Theory·nucl-th

Wednesday·March 13, 2019

13 papers—7 primary·6 cross-listed

01
[Submitted on 11 Mar 2019]
Ab initio optical potentials and nucleon scattering on medium mass nuclei
A. Idini · C. Barbieri · P. Navrátil
We derive ab initio optical potentials from self-consistent Green's function (SCGF) theory and compute the elastic scattering of neutrons off oxygen and calcium isotopes. The comparison with scattering data is satisfactory at low scattering energies. The method is benchmarked against no-core shell model with continuum (NCSMC) calculations, showing that virtual excitations of the target are crucial to predict proper fragmentation and absorption at higher energies. This is a significant step toward deriving optical potentials for medium mass nuclei and complex many-body systems in general.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1903.04581 [pdf]
PRL(2019)·88 citations
02
[Submitted on 11 Mar 2019]
The Role of Baryon Number Conservation in Measurements of Fluctuations
Claude A Pruneau🇺🇸
I discuss the role and impact of net-baryon number conservation in measurements of net proton fluctuations in heavy-ion collisions. I show that the magnitude of the fluctuations is entirely determined by the strength of two particle correlations. At LHC and top RHIC energy, this implies the fluctuations are proportional to the integral of the balance function (BF), $B^{p p ˉ}$ of protons and anti-protons, while in the context of the RHIC beam energy scan (BES), one must also account for correlations of "stopped" protons. The integral of $B^{p p ˉ}$ measured in a $4 π$ detector depends on the relative cross-sections of processes yielding $p p ˉ$ and those balancing the proton baryon number via the production of other anti-baryons. The accepted integral of $B^{p p ˉ}$ further depends on the shape and width of the BF relative to the width of the acceptance. The magnitude of the measured second order cumulant of net proton fluctuations thus has much less to do with QCD susceptibilities than with the creation/transport of baryons and anti-baryons in heavy-ion collisions, and most particularly the impact of radial flow on the width of the BF. I thus advocate that net-proton fluctuations should be studied by means of differential BF measurements rather integral correlators.
Comments:
8 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex)
arXiv:
1903.04591 [pdf]
PRC(2019)·38 citations
03
[Submitted on 12 Mar 2019]
Potential model for nuclear astrophysical fusion reactions with a square-well potential
R. Ogura · K. Hagino · C.A. Bertulani
The potential model for nuclear astrophysical reactions requires a considerably shallow nuclear potential when a square-well potential is employed to fit experimental data. We discuss the origin of this apparently different behavior from that obtained with a smooth Woods-Saxon potential, for which a deep potential is often employed. We argue that due to the sharp change of the potential at the boundary the radius parameter tends to be large in the square-well model, which results in a large absorption radius. The wave function then needs to be suppressed in the absorption region, which can eventually be achieved by using a shallow potential. We thus clarify the reason why the square-well potential has been able to reproduce a large amount of fusion data.
Comments:
4 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1903.04736 [pdf]
PRC(2019)·5 citations
04
[Submitted on 12 Mar 2019]
Suitable resolution for EOS tables in neutron star investigation
Houyuan Chen · Dehua Wen · Na Zhang
Inasmuch as the hydrostatic structure of interior neutron stars uniquely depends on the equation of state (EOS), the inverse constraints on EOS from astrophysical observation have been important methods to reveal the properties of the high-density matter. Up to date, most of EOSs for neutron-star matter are given in tabulations, but these numeric tables could be quite different in resolution. To guarantee both the accuracy and efficiency in computing Tolman-Oppenheimer-Volkoff (TOV) equation, a concise standard for generating EOS tables with suitable resolution is investigated in this work. It is shown that the EOS tables with 50 points logarithmic-uniformly located at supra-nuclear density segment [ $ρ_{0}, 10 ρ_{0}$ ], where $ρ_{0}$ is the nuclear saturation density) would correspond to the interpolation-induced errors at $\sim 0.02%$ for the gravitational mass $M$ and $\sim 0.2%$ for the tidal deformability $Λ$ .
Comments:
10 pages, 4 figures, Accepted to CPC publication
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1903.04875 [pdf]
CPC(2019)·4 citations
05
[Submitted on 8 Mar 2019]
Mathematical aspects of the nuclear glory phenomenon; backward focusing and Chebyshev polynomials
Vladimir B. Kopeliovich🇷🇺
The angular dependence of the cumulative particles production off nuclei near the kinematical boundary for multistep process is defined by characteristic polynomials in angular variables, describing spatial momenta of the particles in intermediate and final states. Physical argumentation, exploring the small phase space method, leads to the appearance of equations for these polynomials in $cos (θ / N)$ , where $θ$ is the polar angle of the momentum of final (cumulative) particle, the integer $N$ being the multiplicity of the process (the number of interactions). It is shown explicitly how these equations appear, and the recurrent relations between polynomials with different $N$ are obtained. Factorization properties of characteristic polynomials found previously, are extended, and their connection with known in mathematics Chebyshev polynomials of 2-d kind is established. As a result, differential cross section of the cumulative particle production has characteristic behaviour $d σ \sim 1/ π - θ$ near the strictly backward direction ( $θ = π$ , the backward focusing effect). Such behaviour takes place for any multiplicity of the interaction, beginning with $n = 3$ , elastic or inelastic (with resonance excitations in intermediate states), and can be called the nuclear glory phenomenon, or 'Buddha's light' of cumulative particles.
Comments:
arXiv admin note: substantial text overlap with arXiv:1403.1992
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th)
arXiv:
1903.04904 [pdf]
0 citations
06
[Submitted on 12 Mar 2019]
On the spin-observables in pseudoscalar meson photoproduction
K. Nakayama🇺🇸
Spin-observables in pseudoscalar meson photoproduction is discussed. This work is complementary to the earlier works on this topic. Here, the reaction amplitude is expressed in Pauli-spin basis which allows to calculate all the observables straightforwardly. We make use of the fact that the underlying reflection symmetry about the reaction plane can be most conveniently and easily exploited in this basis to help finding the non-vanishing and independent observables in this reaction. The important issue of complete experiments is reviewed. By expressing the reaction amplitude in Pauli-spin basis, many sets of eight observables - distinct from those found in earlier works from the amplitude in transversity basis - capable of determining the reaction amplitude up to an overall phase are found. It is also shown that some of the combinations of the spin observables are suited for studying certain aspects of the reaction dynamics. We, then, carry out a (strictly) model-independent partial-wave analysis, in particular, of the peculiar angular behavior of the beam asymmetry observed in eta' photoproduction very close to threshold [P. Levi Sandri et al. 2015 Eur. Phys. J. A 51, 77]. This work should be useful, especially, for newcomers in the field of baryon spectroscopy, where the photoproduction reactions are a major tool for probing the baryon spectra.
Comments:
47 pages, 3 figures, 6 tables,
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1903.05015 [pdf]
J.Phys.G(2019)·5 citations
07
[Submitted on 12 Mar 2019]
Exploring the influence of bulk viscosity of QCD on dilepton tomography
Gojko Vujanovic🇺🇸 · Jean-François Paquet🇺🇸 · Chun Shen🇺🇸 · Gabriel S. Denicol🇧🇷 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦 · Ulrich Heinz🇺🇸
The collective behavior of hadrons and of electromagnetic radiation in heavy-ion collisions has been widely used to study the properties of the the Quark-Gluon Plasma (QGP). Indeed this collectivity, as measured by anisotropic flow coefficients, can be used to constrain the transport properties of QGP. The goal of this contribution is to investigate the influence of the specific bulk viscosity ( $ζ / s$ ) on dilepton production, both at Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) energies. We explore the sensitivity of dileptons to dynamical features that bulk viscosity induces on the evolution of a strongly-interacting medium, and highlight what makes them a valuable probe in the pursuit to also constrain $ζ / s$ .
Comments:
25 pages, 16 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1903.05078 [pdf]
PRC(2020)·40 citations
08
[Submitted on 11 Mar 2019] (cross-list from hep-ph)
The Dynamical Diquark Model: First Numerical Results
Jesse F. Giron🇺🇸 · Richard F. Lebed🇺🇸 · Curtis T. Peterson🇺🇸
We produce the first numerical predictions of the dynamical diquark model of multiquark exotic hadrons. Using Born-Oppenheimer potentials calculated numerically on the lattice, we solve coupled and uncoupled systems of Schroedinger equations to obtain mass eigenvalues for multiplets of states that are, at this stage, degenerate in spin and isospin. Assuming reasonable values for these fine-structure splittings, we obtain a series of bands of exotic states with a common parity eigenvalue that agree well with the experimentally observed charmoniumlike states, and we predict a number of other unobserved states. In particular, the most suitable fit to known pentaquark states predicts states below the charmonium-plus-nucleon threshold. Finally, we examine the strictest form of Born-Oppenheimer decay selection rules for exotics and, finding them to fail badly, we propose a resolution by relaxing the constraint that exotics must occur as heavy-quark spin-symmetry eigenstates.
Comments:
27 pages, 1 PDF figure. Version accepted by JHEP. Includes new results and discussion reflecting the recent LHCb pentaquark discoveries
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1903.04551 [pdf]
JHEP(2019)·67 citations
09
[Submitted on 11 Mar 2019] (cross-list from nucl-ex)
Probe Chiral Magnetic Effect with Signed Balance Function
A.H. Tang🇺🇸
In this paper a pair of observables are proposed as alternative ways, by examining the fluctuation of net momentum-ordering of charged pairs, to study the charge separation induced by the Chiral Magnetic Effect (CME) in relativistic heavy ion collisions. They are, the out-of-plane to in-plane ratio of fluctuation of the difference between signed balance functions measured in pair's rest frame, and the ratio of it to similar measurement made in the laboratory frame. Both observables have been studied with simulations including flow-related backgrounds, and for the first time, backgrounds that are related to resonance's global spin alignment. The two observables have similar positive responses to signal, and opposite, limited responses to identifiable backgrounds arising from resonance flow and spin alignment. Both observables have also been tested with two realistic models, namely, a multi-phase transport (AMPT) model and the anomalous-viscous fluid dynamics (AVFD) model. These two observables, when cross examined, will provide useful insights in the study of CME-induced charge separation.
Comments:
13 pages, 21 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1903.04622 [pdf]
CPC(2020)·51 citations
10
[Submitted on 12 Mar 2019] (cross-list from hep-lat)
Chiral phase transition temperature in (2+1)-Flavor QCD
H.-T. Ding🇨🇳 · P. Hegde🇮🇳 · O. Kaczmarek🇨🇳 · F. Karsch🇩🇪 · Anirban Lahiri🇩🇪 · S.-T. Li🇨🇳 · Swagato Mukherjee🇺🇸 · H. Ohno🇯🇵 · P. Petreczky🇺🇸 · C. Schmidt🇩🇪 · P. Steinbrecher🇺🇸
We present a lattice QCD based determination of the chiral phase transition temperature in QCD with two degenerate, massless quarks and a physical strange quark mass. We propose and calculate two novel estimators for the chiral transition temperature for several values of the light quark masses, corresponding to Goldstone pion masses in the range of $58 MeV ≲ m_{π} ≲ 163 MeV$ . The chiral phase transition temperature is determined by extrapolating to vanishing pion mass using universal scaling analysis. Finite volume effects are controlled by extrapolating to the thermodynamic limit using spatial lattice extents in the range of $2.8$ - $4.5$ times the inverse of the pion mass. Continuum extrapolations are carried out by using three different values of the lattice cut-off, corresponding to lattices with temporal extent $N_{τ} = 6, 8$ and $12$ . After thermodynamic, continuum and chiral extrapolations we find the chiral phase transition temperature $T_{c}^{0} = 13 2_{- 6}^{+ 3}$ MeV.
Comments:
published version in journal
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1903.04801 [pdf]
PRL(2019)·306 citations
11
[Submitted on 12 Mar 2019] (cross-list from hep-ph)
Gauge ambiguity of the quark spectrum in the Color Glass Condensate
Francois Gelis🇫🇷 · Naoto Tanji🇮🇹
In the Color Glass Condensate, the inclusive spectrum of produced quarks in a heavy ion collision is obtained as the Fourier transform of a $2$ -fermion correlation function. Due to its non-locality, the two points of this function must be linked by a Wilson line in order to have a gauge invariant result, but when the quark spectrum is evaluated in a background that has a non-zero chromo-magnetic field, this procedure suffers from an ambiguity related to the choice of the contour defining the Wilson line. In this paper, we use an analytically tractable toy model of the background field in order to study this contour dependence. We show that for a straight contour, unphysical contributions to the spectrum in $p_{⊥}^{- 2}$ and $p_{⊥}^{- 3}$ cancel, leading to a spectrum with a tail in $p_{⊥}^{- 4}$ . If the contour defining the Wilson line deviates from a straight line, the path dependence is at most of order $p_{⊥}^{- 5}$ if its curvature is bounded, and of order $p_{⊥}^{- 4}$ otherwise. When the contour is forced to go through a fixed point, the path dependence is even larger, of order $p_{⊥}^{- 2}$ .
Comments:
28 pages, 9 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1903.04807 [pdf]
NPA(2019)·2 citations
12
[Submitted on 12 Mar 2019] (cross-list from astro-ph.HE)
Unified equations of state for cold non-accreting neutron stars with Brussels-Montreal functionals. I. Role of symmetry energy
J. M. Pearson🇨🇦 · N. Chamel🇧🇪 · A. Y. Potekhin🇷🇺 · A. F. Fantina🇧🇪 · C. Ducoin🇫🇷 · A. K. Dutta🇨🇦 · S. Goriely🇧🇪
The theory of the nuclear energy-density functional is used to provide a unified and thermodynamically consistent treatment of all regions of cold non-accreting neutron stars. In order to assess the impact of our lack of complete knowledge of the density dependence of the symmetry energy on the constitution and the global structure of neutron stars, we employ four different functionals. All of them were precision fitted to essentially all the nuclear-mass data with the Hartree-Fock-Bogoliubov method and two different neutron-matter equations of state based on realistic nuclear forces. For each functional, we calculate the composition, the pressure-density relation, and the chemical potentials throughout the star. We show that uncertainties in the symmetry energy can significantly affect the theoretical results for the composition and global structure of neutron stars. To facilitate astrophysical applications, we construct analytic fits to our numerical results.
Comments:
36 pages, 31 figures, 29 tables; corrected according to an erratum (2019, accepted)
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1903.04981 [pdf]
MNRAS(2018)·270 citations
13
[Submitted on 12 Mar 2019] (cross-list from hep-ph)
The $ss s ˉ s ˉ$ tetraquark states and the newly observed structure $X (2239)$ by BESIII Collaboration
Qi-Fang Lü🇨🇳 · Kai-Lei Wang🇨🇳 · Yu-Bing Dong🇨🇳
We investigate the mass spectrum of the $ss s ˉ s ˉ$ tetraquark states within the relativized quark model. By solving the Schrödinger-like equation with the relativized potential, the masses of the $S -$ and $P -$ wave $ss s ˉ s ˉ$ tetraquarks are obtained. The screening effects are also taken into account. It is found that the observed resonant structure $X (2239)$ in the $e^{+} e^{-} \to K^{+} K^{-}$ process by BESIII Collaboration can be assigned as a $P -$ wave $1^{--}$ $ss s ˉ s ˉ$ tetraquark state. Furthermore, the radiative transition and strong decay behaviors of this structure are also estimated, which can provide helpful information for future experimental searches.
Comments:
7 pages, 2 figures. Add the strong decay behaviors. Version accepted by Chinese Physics C
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1903.05007 [pdf]
CPC(2020)·33 citations

Affiliations

first authorsco-authorsvia INSPIRE