Nuclear Theory·nucl-th

Tuesday·April 30, 2019

14 papers—7 primary·7 cross-listed

01
[Submitted on 27 Apr 2019]
Possible chiral doublets in $^{60}$ Ni
J. Peng🇨🇳 · Q. B. Chen🇩🇪
The open problem on whether or not the chirality exists in doublet bands M1 and M4 in light-mass even-even nucleus $^{60}$ Ni is studied by adopting the recently developed fully quantal four- $j$ shells triaxial particle rotor model. The corresponding experimental energy spectra, energy differences between doublet bands, and the available $B (M 1) / B (E 2)$ values are successfully reproduced. The analyses on the basis of the angular momentum components, the azimuthal plots, and the $K$ -plots suggest that the chiral modes exist at $I \geq 12ℏ$ in doublet bands M1 and M4.
Comments:
14 pages, 4 figures, accepted by Phys. Lett. B
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1904.12100 [pdf]
PLB(2019)·20 citations
02
[Submitted on 27 Apr 2019]
Direct capture cross section of $^{9}$ Be(n, $γ$ ) $^{10}$ Be
Peter Mohr
The cross section of the $^{9}$ Be(n, $γ$ ) $^{10}$ Be reaction was calculated in the direct capture model. All parameters of the calculations were adjusted to properties of the $^{9}$ Be + n system at thermal energies. The calculated cross section at thermonuclear energies shows the expected $1/ v$ behavior of $s$ -wave capture at low energies, but increases towards higher energies as typical $p$ -wave capture. Excellent agreement between new experimental data in the astrophysically relevant energy region and the present calculation is found.
Comments:
7 pages, 3 figures, Phys. Rev. C, accepted for publication
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1904.12115 [pdf]
PRC(2019)·3 citations
03
[Submitted on 27 Apr 2019]
Emergence of nuclear clustering in electric-dipole excitations of $^{6}$ Li
S. Satsuka · W. Horiuchi
Nuclear clustering plays an important role, especially in the dynamics of light nuclei. The importance of the emergence of the nuclear clustering was discussed in the recent measurement of the photoabsorption cross sections as it offered the possibility of the coexistence of various excitation modes which are closely related to the nuclear clustering. To understand the excitation mechanism, we study the electric-dipole ( $E 1$ ) responses of $^{6}$ Li with a fully microscopic six-body calculation. The ground-state wave function is accurately described with a superposition of correlated Gaussian (CG) functions with the aid of the stochastic variational method. The final-state wave functions are also expressed by a number of the CG functions including important configurations to describe the six-body continuum states excited by the $E 1$ field. We found that the out-of-phase transitions occur due to the oscillations of the valence nucleons against the $^{4}$ He cluster at the low energies around 10 MeV indicating ``soft'' giant-dipole-resonance(GDR)-type excitations, which are very unique in the $^{6}$ Li system but could be found in other nuclear systems. At the high energies beyond $\sim 30$ MeV typical GDR-type transitions occur. The $^{3}$ He- $^{3}$ H clustering plays an important role to the GDR phenomena in the intermediate energy regions around 20 MeV.
Comments:
13 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1904.12129 [pdf]
PRC(2019)·11 citations
04
[Submitted on 29 Apr 2019]
Implementation of the 8-Nucleon Yakubovsky Formalism for Halo Nucleus 8He
Eskandar Ahmadi Pouya · Ali Akbar Rajabi
In order to study the bound-state structure of the Helium halo nuclei, the 8-nucleon Yakubovsky formalism has been implemented for 8He in a 5-body sub-cluster model, i.e. alpha+n+n+n+n. In this case, the 8-nucleon Yakubovsky equations has been obtained in the form of two coupled equations, based on the two independent components. In addition, by removing the contribution interactions of the 8 and 7s bound nucleons in the formalism, the obtained equations explicitly reduce to the 6-nucleon Yakubovsky equations for 6He, in the case of effective 3-body model, i.e. alpha+n+n. In view of the expectation for the dominant structure of 8He, namely an inert alpha-core and four loosely-bound neutrons, Jacobi configurations of the two components in momentum space have been represented to provide technicalities which were considered useful for a numerical performance, such as bound-state calculations and momentum density distributions for halo-bound neutrons.
Comments:
13 pages, 2 Figures, Original Article, 2019
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1904.12451 [pdf]
0 citations
05
[Submitted on 29 Apr 2019]
Quark matter symmetry energy effect on equation of state for neutron stars
Xuhao Wu🇨🇳 · Akira Ohnishi🇯🇵 · Hong Shen🇨🇳
We study the equation of state of neutron-star matter including the effects of isovector-vector coupling in quark matter. We employ the relativistic mean-field theory with an extended TM1 parameter set to describe hadronic matter and the SU(3) Nambu-Jona-Lasinio model with isovector-vector and hypercharge-vector couplings to describe the quark matter. The deconfinement hadron-quark phase transition is constructed under Gibbs phase equilibrium conditions. It is found that the isovector-vector and hypercharge-vector couplings in quark matter enhance the symmetry energy and hypercharge symmetry energy in neutron-star matter.
Comments:
6 pages, 3 figures, Proceeding of the Xiamen-CUSTIPEN workshop
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1904.12454 [pdf]
AIP Conf.Proc.(2019)·8 citations
06
[Submitted on 29 Apr 2019]
Probing chiral interactions up to next-to-next-to-next-to-leading order in medium-mass nuclei
J. Hoppe · C. Drischler · K. Hebeler · A. Schwenk · J. Simonis
We study ground-state energies and charge radii of closed-shell medium-mass nuclei based on novel chiral nucleon-nucleon (NN) and three-nucleon (3N) interactions, with a focus on exploring the connections between finite nuclei and nuclear matter. To this end, we perform in-medium similarity renormalization group (IM-SRG) calculations based on chiral interactions at next-to-leading order (NLO), N $^{2}$ LO, and N $^{3}$ LO, where the 3N interactions at N $^{2}$ LO and N $^{3}$ LO are fit to the empirical saturation point of nuclear matter and to the triton binding energy. Our results for energies and radii at N $^{2}$ LO and N $^{3}$ LO overlap within uncertainties, and the cutoff variation of the interactions is within the EFT uncertainty band. We find underbound ground-state energies, as expected from the comparison to the empirical saturation point. The radii are systematically too large, but the agreement with experiment is better. We further explore variations of the 3N couplings to test their sensitivity in nuclei. While nuclear matter at saturation density is quite sensitive to the 3N couplings, we find a considerably weaker dependence in medium-mass nuclei. In addition, we explore a consistent momentum-space SRG evolution of these NN and 3N interactions, exhibiting improved many-body convergence. For the SRG-evolved interactions, the sensitivity to the 3N couplings is found to be stronger in medium-mass nuclei.
Comments:
10 pages, 11 figures, published version
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1904.12611 [pdf]
PRC(2019)·68 citations
07
[Submitted on 29 Apr 2019]
Extracting the strangeness freeze-out temperature from net-Kaon data at RHIC
Rene Bellwied🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸 · Paolo Parotto🇺🇸 · Israel Portillo Vazquez🇺🇸 · Claudia Ratti🇺🇸 · Jamie Stafford🇺🇸
Using the moments of the net-kaon distribution calculated within a state of-the-art hadron resonance gas model compared to experimental data from STAR's Beam Energy Scan, we find that the extracted strange freeze-out temperature is incompatible with the light one extracted from net-proton and net-charge fluctuations. Additionally predictions for net- $L amb d a$ fluctuations are made that also appear to be consistent with a higher freeze-out temperature for strange particles. This strangeness freeze-out temperature is roughly $10 - 15$ MeV higher than the corresponding light freeze-out temperature. We also discuss cross-susceptibilities using different identified particles, which may be a further test of this two freeze-out temperature picture. Finally, we lay out the necessary updates needed in relativistic hydrodynamic models to take into account for this two freeze-out temperature scenario and present preliminary results of $Λ$ spectra at RHIC for AuAu $s_{N N} = 200$ GeV collisions that indicate a higher freeze-out temperature is preferred.
Comments:
11 pages, 6 figure, Proceedings for CPOD2018
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1904.12711 [pdf]
PoS(2019)·4 citations
08
[Submitted on 26 Apr 2019] (cross-list from hep-lat)
Short Range Operator Contributions to $0 ν β β$ decay from LQCD
Henry Monge-Camacho🇺🇸 · Evan Berkowitz🇩🇪 · David Brantley🇺🇸 · Chia Cheng Chang🇯🇵 · M.A. Clark🇺🇸 · Arjun Gambhir🇺🇸 · Nicolas Garrón🇬🇧 · Bálint Joó🇺🇸 · Thorsten Kurth🇺🇸 · Amy Nicholson🇺🇸 · Enrico Rinaldi🇺🇸 · Brian Tiburzi🇺🇸 · Pavlos Vranas🇺🇸 · André Walker-Loud🇺🇸
The search for neutrinoless double beta decay of nuclei is believed to be one of the most promising means to search for new physics. Observation of this very rare nuclear process, which violates Lepton Number conservation, would imply the neutrino sector has a Majorana mass component and may also provide an explanation for the universe matter-antimatter asymmetry of the universe. In the case where a heavy intermediate particle is exchanged in this process, QCD contributions from short range interactions become relevant and the calculation of matrix elements with four-quark operators becomes necessary. In these proceedings we will discuss our current progress in the calculation of these four-quark operators from LQCD.
Comments:
Proceedings of the 36th Annual International Symposium on Lattice Field Theory, 22-28 July, 2018, Michigan State University, East Lansing, Michigan
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1904.12055 [pdf]
PoS(2019)·4 citations
09
[Submitted on 28 Apr 2019] (cross-list from nucl-ex)
Neutron skins of atomic nuclei: per aspera ad astra
M. Thiel · C. Sfienti · J. Piekarewicz · C.J. Horowitz · M. Vanderhaeghen
The complex nature of the nuclear forces generates a broad range and diversity of observational phenomena. Heavy nuclei, though orders of magnitude less massive than neutron stars, are governed by the same underlying physics, which is enshrined in the nuclear equation of state. Heavy nuclei are expected to develop a neutron-rich skin where many neutrons collect near the surface. Such a skin thickness is strongly sensitive to the poorly-known density dependence of the symmetry energy near saturation density. An accurate and model-independent determination of the neutron-skin thickness of heavy nuclei would provide a significant first constraint on the density dependence of the nuclear symmetry energy. The determination of the neutron-skin thickness of heavy nuclei has far reaching consequences in many areas of physics as diverse as heavy-ion collisions, polarized electron and proton scattering off nuclei, precision tests of the standard model using atomic parity violation, and nuclear astrophysics. While a systematic and concerted experimental effort has been made to measure the neutron-skin thickness of heavy nuclei, a precise and model-independent determination remains elusive. How to move forward at a time when many new facilities are being commissioned and how to strengthen the synergy with other areas of physics are primary goals of this review.
Comments:
Submitted for publication to Journal of Physics G
Subjects:
Nuclear Experiment (nucl-ex); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1904.12269 [pdf]
J.Phys.G(2019)·150 citations
10
[Submitted on 28 Apr 2019] (cross-list from hep-ph)
Testing the tetraquark mixing framework from QCD sum rules for $a_{0} (980)$
Hee-Jung Lee🇰🇷 · K. S. Kim🇰🇷 · Hungchong Kim🇰🇷
According to a recent proposal of the tetraquark mixing framework, the two light-meson nonets in the $J^{P} = 0^{+}$ channel, namely the light nonet composed of $a_{0} (980)$ , $K_{0}^{*} (800)$ , $f_{0} (500)$ , $f_{0} (980)$ , and the heavy nonet of $a_{0} (1450)$ , $K_{0}^{*} (1430)$ , $f_{0} (1370)$ , $f_{0} (1500)$ , can be expressed by linear combinations of the two tetraquark types, one type containing the spin-0 diquark and the other with the spin-1 diquark. Among various consequences of this mixing model, one surprising result is that the second tetraquark with the spin-1 diquark configuration is more important for the light nonet. In this work, we report that this result can be supported by the QCD sum rule calculation. In particular, we construct a QCD sum rule for the isovector resonance $a_{0} (980)$ using an interpolating field composed of both tetraquark types and then perform the operator product expansion up to dimension 10 operators. Our sum rule analysis shows that the spin-1 diquark configuration is crucial in generating the $a_{0} (980)$ mass. Also, the mixed correlation function constructed from the two tetraquark types is found to have large strength which seems consistent with what the tetraquark mixing framework is advocating. On the other hand, the correlation function from the interpolating field with the spin-0 diquark configuration alone fails to predict the $a_{0} (980)$ mass mostly by the huge negative contribution from dimension 8 operators.
Comments:
12 pages, 9 figures, One error in the code has been corrected. Some changes in the figures have been made. A few references have been added. This is an accepted version to be published in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1904.12311 [pdf]
PRD(2019)·18 citations
11
[Submitted on 28 Apr 2019] (cross-list from hep-lat)
Pion generalized parton distribution from lattice QCD
Jiunn-Wei Chen🇹🇼 · Huey-Wen Lin🇺🇸 · Jian-Hui Zhang🇩🇪
We present the first lattice calculation of the valence-quark generalized parton distribution (GPD) of the pion using the large-momentum effective theory (LaMET) approach. We focus on the zero-skewness limit, where the GPD has a probability-density interpretation in the longitudinal Bjorken $x$ and the transverse impact-parameter distributions. Our calculation is done using clover valence fermions on an ensemble of gauge configurations with $2 + 1 + 1$ flavors (degenerate up/down, strange and charm) of highly improved staggered quarks (HISQ) with lattice spacing $a \approx 0.12$ fm, box size $L \approx 3$ fm and pion mass $m_{π} \approx 310$ MeV. The parton distribution function and the form factor are reproduced as special limits of the GPD as expected. Due to the large errors, this exploratory study does not show a clear preference among different model assumptions about the kinematic dependence of the GPD. To discriminate between these assumptions, future studies using higher-statistics data will be crucial.
Comments:
Version published in Nucl. Phys. B
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1904.12376 [pdf]
NPB(2020)·127 citations
12
[Submitted on 29 Apr 2019] (cross-list from astro-ph.HE)
Role of the Symmetry Energy on the Structure of Neutron Stars with Unified Equations of State
Nicolas Chamel🇧🇪 · John Michael Pearson🇨🇦 · Alexander Y. Potekhin🇷🇺 · Anthea F. Fantina🇫🇷 · Camille Ducoin🇫🇷 · Anup Dutta🇮🇳 · Stéphane Goriely🇧🇪 · Loïc Perot🇧🇪
The role of the symmetry energy on the internal constitution and the global structure of a cold nonaccreted neutron star is studied using a set of unified equations of state. Based on the nuclear energy-density functional theory, these equations of state provide a thermodynamically consistent treatment of all regions of the star and were calculated using the four different Brussels-Montreal functionals BSk22, BSk24, BSk25 and BSk26. Our predictions are compared to various constraints inferred from astrophysical observations including the recent detection of the gravitational wave signal GW170817 from a binary neutron-star merger.
Comments:
15 pages, 6 figures. To appear in the AIP Conference Proceedings of the Xiamen-CUSTIPEN Workshop on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave Astronomy (January 3 - 7, 2019, Xiamen, China)
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1904.12477 [pdf]
AIP Conf.Proc.(2019)·4 citations
13
[Submitted on 29 Apr 2019] (cross-list from hep-ph)
A background estimator for jet studies in p+p and A+A collisions
Yacine Mehtar-Tani🇺🇸 · Alba Soto-Ontoso🇺🇸 · Marta Verweij🇺🇸
Experimentally, jet physics studies face an unavoidable task: distinguishing, at the detector level, the particles produced in the hard partonic scattering from the ones created in unrelated soft processes such as pileup interactions in high-luminosity proton-proton scattering or the underlying event in heavy-ion collisions. The fluctuating nature of the background constitutes the main source of uncertainty for any subtraction algorithm. Aiming at mitigating the effect of such fluctuations, we present a new method to estimate the background contribution to the transverse momentum on a jet-by-jet basis. Our approach is based on estimating the median background momentum density stored above a $p_{T}$ -cut applied at the constituent level and an experimentally accessible correction term related to the signal contribution below the cut. This allows to trade part of the uncertainty due to background contamination for that of the signal below the cut, similarly to SoftKiller method. We propose to reduce the fluctuations of the latter by exploiting intrinsic correlations among the soft and hard sectors of QCD jets. Our data-driven approach is tested against PYTHIA8 and JEWEL di-jet events embedded in a thermal background and compared to the area-median and SoftKiller methods. The main result of this study is a $\sim 5 - 40%$ improvement on the resolution of the reconstructed jet $p_{T}$ compared to previous methods in a high-luminosity proton-proton scenario. Its applicability in a heavy-ion context is also discussed.
Comments:
7 pages, 4 figures, 3 tables, v2: Major modifications: included study on HL-LHC pile-up, improved estimate for heavy-ion collisions. Accepted for publication in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1904.12815 [pdf]
PRD(2019)·3 citations
14
[Submitted on 29 Apr 2019] (cross-list from cond-mat.quant-gas)
Viscosity spectral functions of resonating fermions in the quantum virial expansion
Yusuke Nishida
We consider two-component fermions with a zero-range interaction both in two and three dimensions and study their spectral functions of bulk and shear viscosities for an arbitrary scattering length. Here the Kubo formulas are systematically evaluated up to the second order in the quantum virial expansion applicable to the high-temperature regime. In particular, our computation of the bulk viscosity spectral function is facilitated by expressing it with the contact-contact response function, which can be measured experimentally under the periodic modulation of the scattering length. The obtained formulas are fully consistent with the known constraints on high-frequency tail and sum rule. Although our static shear viscosity agrees with that derived from the kinetic theory, our static bulk viscosity disagrees. Furthermore, the latter for three dimensions exhibits an unexpected non-analyticity of $ζ \sim (ln a^{2}) / a^{2}$ in the unitarity limit $a \to \infty$ , which thus challenges the "crossover" hypothesis.
Comments:
17 single-column pages, 1 multi-panel figure; (v2) minor improvements and added appendix A on the bulk viscosity formula at O(z^3); (v3) published version; (v4) corrected typos in Eq.(73) and added appendix B on the derivation of Eq.(67)
Subjects:
Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th)
arXiv:
1904.12832 [pdf]
Annals Phys.(2019)·33 citations

Affiliations

first authorsco-authorsvia INSPIRE