Nuclear Theory·nucl-th

Thursday·September 8, 2016

13 papers—6 primary·7 cross-listed

01
[Submitted on 6 Sept 2016]
Partial-Wave Analysis of Nucleon-Nucleon Elastic Scattering Data
Ron L. Workman🇺🇸 · William J. Briscoe🇺🇸 · Igor I. Strakovsky🇺🇸
Energy-dependent and single-energy fits to the existing nucleon-nucleon database have been updated to incorporate recent measurements. The fits cover a region from threshold to 3 GeV, in the laboratory kinetic energy, for proton-proton scattering, with an upper limit of 1.3 GeV for neutron-proton scattering. Experiments carried out at the COSY-WASA and COSY-ANKE facilities have had a significant impact on the partial-wave solutions. Results are discussed in terms of both partial-wave and direct reconstruction amplitudes.
Comments:
15 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1609.01741 [pdf]
PRC(2016)·53 citations
02
[Submitted on 6 Sept 2016]
Quantal Nucleon Diffusion I: Central Collisions of Symmetric Nuclei
S. Ayik · O. Yilmaz · B. Yilmaz · A. S. Umar
Quantal diffusion mechanism of nucleon exchange is studied in the central collisions of several symmetric heavy-ion collisions in the framework of the Stochastic Mean-Field (SMF) approach. Since at bombarding energies below the fusion barrier, di-nuclear structure is maintained, it is possible to describe nucleon exchange as a diffusion process familiar from deep-inelastic collisions. Quantal diffusion coefficients, including memory effects, for proton and neutron exchanges are extracted microscopically employing the SMF approach. The quantal calculations of neutron and proton variances are compared with the semi-classical results.
Comments:
9 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1609.01772 [pdf]
17 citations
03
[Submitted on 7 Sept 2016]
Event-by-event generation of vorticity in heavy-ion collisions
Wei-Tian Deng🇨🇳 · Xu-Guang Huang🇺🇸
In a noncentral heavy-ion collision, the two colliding nuclei have finite angular momentum in the direction perpendicular to the reaction plane. After the collision, a fraction of the total angular momentum is retained in the produced hot quark-gluon matter and is manifested in the form of fluid shear. Such fluid shear creates finite flow vorticity. We study some features of such generated vorticity, including its strength, beam energy dependence, centrality dependence, and spatial distribution.
Comments:
V1: 4 pages,3 figures. Contribution to the Proceedings of SQM2016, Berkeley, California, USA, June 27 - July 01, 2016
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1609.01801 [pdf]
J.Phys.Conf.Ser.(2017)·8 citations
04
[Submitted on 7 Sept 2016]
Relativistic Brueckner-Hartree-Fock theory for finite nuclei
Shihang Shen · Jinniu Hu · Haozhao Liang · Jie Meng · Peter Ring · Shuangquan Zhang
Starting with a bare nucleon-nucleon interaction, for the first time the full relativistic Brueckner-Hartree-Fock equations are solved for finite nuclei in a Dirac-Woods-Saxon basis. No free parameters are introduced to calculate the ground-state properties of finite nuclei. The nucleus $^{16}$ O is investigated as an example. The resulting ground-state properties, such as binding energy and charge radius, are considerably improved as compared with the non-relativistic Brueckner-Hartree-Fock results and much closer to the experimental data. This opens the door for \emph{ab initio} covariant investigations of heavy nuclei.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1609.01866 [pdf]
Chin.Phys.Lett.(2016)·57 citations
05
[Submitted on 7 Sept 2016]
Spectra and elliptic flow of thermal photons from full overlap U+U collisions at RHIC
Pingal Dasgupta🇮🇳 · Rupa Chatterjee🇮🇳 · Dinesh K. Srivastava🇮🇳
We calculate $p_{T}$ spectra and elliptic flow for tip-tip and body-body configurations of full overlap uranium-uranium (U+U) collisions using a hydrodynamic model with smooth initial density distribution and compare the results with those obtained from Au+Au collisions at RHIC. Production of thermal photons is seen to be significantly larger for tip-tip collisions compared to body-body collisions of uranium nuclei in the region $p_{T} >$ 1 GeV. The thermal photon spectrum from body-body collisions is found to be close to the spectrum from most central Au+Au collisions at RHIC. The elliptic flow parameter calculated for body-body collisions is found to be large and comparable to the $v_{2} (p_{T})$ for mid-central collisions of Au nuclei. On the other hand, as expected, the $v_{2} (p_{T})$ is close to zero for tip-tip collisions. The qualitative nature of the photon spectra and elliptic flow for the two different orientations of uranium nuclei is found to be independent of the initial parameters of the model calculation. We show that the photon results from fully overlapping U+U collisions are complementary to the results from Au+Au collisions at RHIC.
Comments:
7 pages, 6 figures, Discussions and references added. To appear in Physical Review C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1609.01949 [pdf]
PRC(2017)·20 citations
06
[Submitted on 7 Sept 2016]
Nucleus--nucleus interactions in the inner crust of neutron stars
D. Kobyakov · C. J. Pethick
The interaction between nuclei in the inner crust of neutron stars consists of two contributions, the so-called "direct" interaction and an "induced" one due to density changes in the neutron fluid. For large nuclear separations $r$ the contributions from nuclear forces to each of these terms are shown to be nonzero. In the static limit they are equal in magnitude but have opposite signs and they cancel exactly. We analyze earlier results on effective interactions in the light of this finding. We consider the properties of long-wavelength collective modes and, in particular, calculate the degree of mixing between the lattice phonons and the phonons in the neutron superfluid. Using microscopic theory, we calculate the net non-Coulombic contribution to the nucleus--nucleus interaction and show that, for large $r$ , the leading term is due to exchange of two phonons and varies as $1/ r^{7}$ : it is an analog of the Casimir--Polder interaction between neutral atoms.
Comments:
11 pages, 4 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1609.01976 [pdf]
PRC(2016)·19 citations
07
[Submitted on 7 Sept 2016] (cross-list from astro-ph.HE)
Probing nuclear bubble structure via neutron star asteroseismology
Hajime Sotani · Kei Iida · Kazuhiro Oyamatsu
We consider torsional oscillations that are trapped in a layer of spherical-hole (bubble) nuclear structure, which is expected to occur in the deepest region of the inner crust of a neutron star. Because this layer intervenes between the phase of slab nuclei and the outer core of uniform nuclear matter, torsional oscillations in the bubble phase can be excited separately from usual crustal torsional oscillations. We find from eigenmode analyses for various models of the equation of state of uniform nuclear matter that the fundamental frequencies of such oscillations are almost independent of the incompressibility of symmetric nuclear matter, but strongly depend on the slope parameter of the nuclear symmetry energy $L$ . Although the frequencies are also sensitive to the entrainment effect, i.e., what portion of nucleons outside bubbles contribute to the oscillations, by having such a portion fixed, we can successfully fit the calculated fundamental frequencies of torsional oscillations in the bubble phase inside a star of specific mass and radius as a function of $L$ . By comparing the resultant fitting formula to the frequencies of quasi-periodic oscillations (QPOs) observed from the soft-gamma repeaters, we find that each of the observed low-frequency QPOs can be identified either as a torsional oscillation in the bubble phase or as a usual crustal oscillation, given generally accepted values of $L$ for all the stellar models considered here.
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1609.01802 [pdf]
MNRAS(2017)·48 citations
08
[Submitted on 7 Sept 2016] (cross-list from hep-ph)
Molecular components in $D_{s0}^{*} (2317)$ and $D_{s1} (2460)$ mesons
Pablo G. Ortega🇨🇭 · Jorge Segovia🇩🇪 · David R. Entem🇪🇸 · Francisco Fernández🇪🇸
Different experiments have confirmed that the $D_{s 0}^{*} (2317)$ and $D_{s 1} (2460)$ mesons are very narrow states located, respectively, below the $D K$ and $D^{*} K$ thresholds. This is markedly in contrast with the expectations of naive quark models and heavy quark symmetry. We address the mass shifts of the $c s ˉ$ ground states with quantum numbers $J^{P} = 0^{+}$ ( $D_{s 0}^{*} (2317)$ ) and $J^{P} = 1^{+}$ ( $D_{s 1} (2460)$ ) using a nonrelativistic constituent quark model in which quark-antiquark and meson-meson degrees of freedom are incorporated. The quark model has been applied to a wide range of hadronic observables and thus the model parameters are completely constrained. We observe that the coupling of the $0^{+}$ $(1^{+})$ meson sector to the $D K$ $(D^{*} K)$ threshold is a key feature in lowering the masses of the corresponding $D_{s 0}^{*} (2317)$ and $D_{s 1} (2460)$ states predicted by the naive quark model, but also in describing the $D_{s 1} (2536)$ meson as the $1^{+}$ state of the $j_{q}^{P} = 3/ 2^{+}$ doublet predicted by heavy quark symmetry and thus reproducing its strong decay properties. Two features of our formalism cannot be address nowadays by other approaches: the coupling of the $D$ -wave $D^{*} K$ threshold in the $J^{P} = 1^{+}$ $c s ˉ$ channel and the computation of the probabilities associated with different Fock components in the physical state.
Comments:
Contribution to the proceedings of the 14th International Workshop on Meson Production, Properties and Interaction (MESON2016). June 2-7, 2016. Krakow, Poland
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1609.01846 [pdf]
EPJ Web Conf.(2016)·3 citations
09
[Submitted on 7 Sept 2016] (cross-list from hep-lat)
Flavor structure of $Λ$ baryons from lattice QCD: From strange to charm quarks
Philipp Gubler🇰🇷 · Toru T. Takahashi🇯🇵 · Makoto Oka🇯🇵
We study $Λ$ baryons of spin-parity $\frac{1}{2}^{\pm}$ with either a strange or charm valence quark in full 2+1 flavor lattice QCD. Multiple $S U (3)$ singlet and octet operators are employed to generate the desired single baryon states on the lattice. Via the variational method, the couplings of these states to the different operators provide information about the flavor structure of the $Λ$ baryons. We make use of the gauge configurations of the PACS-CS Collaboration and chirally extrapolate the results for the masses and $S U (3)$ flavor components to the physical point. We furthermore gradually change the hopping parameter of the heaviest quark from strange to charm to study how the properties of the $Λ$ baryons evolve as a function of the heavy quark mass. It is found that the baryon energy levels increase almost linearly with the quark mass. Meanwhile, the flavor structure of most of the states remains stable, with the exception of the lowest $\frac{1}{2}^{-}$ state, which changes from a flavor singlet $Λ$ to a $Λ_{c}$ state with singlet and octet components of comparable size. Finally, we discuss whether our findings can be interpreted with the help of a simple quark model and find that the negative-parity $Λ_{c}$ states can be naturally explained as diquark excitations of the light $u$ and $d$ quarks. On the other hand, the quark-model picture does not appear to be adequate for the negative-parity $Λ$ states, suggesting the importance of other degrees of freedom to describe them.
Comments:
14 pages, 8 figures, 5 tables; v2 (published version in PRD): title slightly changed, discussion about systematic uncertainties extended, typos fixed, references added
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.01889 [pdf]
PRD(2016)·22 citations
10
[Submitted on 7 Sept 2016] (cross-list from nucl-ex)
Many Facets of Strangeness Nuclear Physics with Stored Antiprotons
Josef Pochodzalla🇩🇪 · Sebastian Bleser🇩🇪 · Alicia Sanchez Lorente🇩🇪 · Marta Martinez Rojo🇩🇪 · Marcell Steinen🇩🇪 · Jürgen Gerl🇩🇪 · Jasmina Kojouharova🇩🇪 · Ivan Kojouharova🇩🇪
Stored antiprotons beams in the GeV range represent a unparalleled factory for hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of strange hadronic systems with unprecedented precision. The behavior of hyperons and -- for the first time -- of antihyperons in nuclear systems can be studied under well controlled conditions. The exclusive production of $Λ Λ ˉ$ and $Σ^{-} Λ ˉ$ pairs in antiproton-nucleus interactions probe the neutron and proton distribution in the nuclear periphery and will help to sample the neutron skin. For the first time, high resolution $γ$ -spectroscopy of doubly strange nuclei will be performed, thus complementing measurements of ground state decays of double hypernuclei with mesons beams at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange $Ξ$ -atoms are feasible and even the production of $Ω^{-}$ -atoms will be within reach. The latter might open the door to the $∣ s ∣$ =3 world in strangeness nuclear physics, by the study of the hadronic $Ω^{-}$ -nucleus interaction and the very first measurement of a spectroscopic quadrupole moment of a baryon which will be a benchmark test for our understanding of hadron structure.
Comments:
Proceddings of HYP2015
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1609.01916 [pdf]
JPS Conf.Proc.(2017)·7 citations
11
[Submitted on 7 Sept 2016] (cross-list from nucl-ex)
Experimental results on charge fluctuations in heavy-ion collisions
D. K. Mishra🇮🇳 · P. Garg🇺🇸 · P. K. Netrakanti🇮🇳 · L. M. Pant🇮🇳 · A. K. Mohanty🇮🇳
We present a subset of experimental results on charge fluctuation from the heavy-ion collisions to search for phase transition and location of critical point in the QCD phase diagram. Measurements from the heavy-ion experiments at the SPS and RHIC energies observe that total charge fluctuations increase from central to peripheral collisions. The net-charge fluctuations in terms of dynamical fluctuation measure $ν_{(+-, d y n)}$ are studied as a function of collision energy (\sqsn) and centrality of the collisions. The product of $ν_{(+-, d y n)}$ and $⟨ N_{c h} ⟩$ shows a monotonic decrease with collision energies, which indicates that at LHC energy the fluctuations have their origin in the QGP phase. The fluctuations in terms of higher moments of net-proton, net-electric charge and net-kaon have been measured for various \sqsn. Deviations are observed in both $S σ$ and $κ σ^{2}$ for net-proton multiplicity distributions from the Skellam and hadron resonance gas model for \sqsn $<$ 39 GeV. Higher moment results of the net-electric charge and net-kaon do not observe any significant non-monotonic behavior as a function of collision energy. We also discuss the extraction of the freeze-out parameters using particle ratios and experimentally measured higher moments of net-charge fluctuations. The extracted freeze-out parameters from experimentally measured moments and lattice calculations, are found to be in agreement with the results obtained from the fit of particle ratios to the thermal model calculations.
Comments:
14 pages, 10 figures; Substantial text modification and equivalent to that published version in Adv. in High. Eng. Physics
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1609.01920 [pdf]
Adv.High Energy Phys.(2017)·4 citations
12
[Submitted on 7 Sept 2016] (cross-list from hep-ph)
Tagged spectator DIS on a polarized spin-1 target
W. Cosyn🇧🇪 · M. Sargsian🇺🇸 · C. Weiss🇺🇸
We discuss the process of deep-inelastic electron scattering (DIS) on the polarized deuteron with detection of a nucleon in the nuclear fragmentation region ("spectator tagging"). We cover (a) the general structure of the semi-inclusive DIS cross section on a spin-1 target; (b) the tagged structure functions in the impulse approximation, where deuteron structure is described by the $N N$ light-front wave function; (c) the extraction of free neutron structure through on-shell extrapolation in the recoil proton momentum. As an application we consider the extraction of the neutron spin structure function $g_{1 n}$ through polarized electron scattering on the longitudinally polarized deuteron with proton tagging and on-shell extrapolation. Such measurements would be possible at an Electron-Ion Collider (EIC) with polarized deuteron beams and forward proton detectors.
Comments:
6 pages, 2 figures. Proceedings of XXIV International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS 2016), DESY Hamburg, Germany, 11-15 April, 2016
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1609.01970 [pdf]
PoS(2016)·2 citations
13
[Submitted on 7 Sept 2016] (cross-list from hep-lat)
Practical quasi parton distribution functions
Tomomi Ishikawa🇺🇸 · Yan-Qing Ma🇨🇳 · Jian-Wei Qiu🇺🇸 · Shinsuke Yoshida🇯🇵
A completely new strategy to calculate parton distribution functions on the lattice has recently been proposed. In this method, lattice calculable observables, called quasi distributions, are related to normal distributions. The quasi distributions are known to contain power-law UV divergences arise from a Wilson line in the non-local operator, while the normal distributions only have logatithmic UV divergences. We propose possible method to subtract the power divegence to make the matching of the quasi with the normal distributions well-defined. We also demonstrate the matching of the quasi quark distribution between continuum and lattice implementing the power divergence subtraction. The matching calculations are carried out by one-loop perturbation.
Comments:
28 pages, 7 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.02018 [pdf]
94 citations

Affiliations

first authorsco-authorsvia INSPIRE