Nuclear Theory·nucl-th

Thursday·September 8, 2016

13 papers—6 primary·7 cross-listed

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

Probing nuclear bubble structure via neutron star asteroseismology

Molecular components in Ds0∗​(2317) and Ds1​(2460) mesons

Flavor structure of Λ baryons from lattice QCD: From strange to charm quarks

Many Facets of Strangeness Nuclear Physics with Stored Antiprotons

Experimental results on charge fluctuations in heavy-ion collisions

Tagged spectator DIS on a polarized spin-1 target

Practical quasi parton distribution functions

Affiliations

Molecular components in $D_{s0}^{*} (2317)$ and $D_{s1} (2460)$ mesons

Flavor structure of $Λ$ baryons from lattice QCD: From strange to charm quarks