Nuclear Theory·nucl-th

Thursday·February 21, 2019

11 papers—5 primary·6 cross-listed

01
[Submitted on 20 Feb 2019]
Green's function method for the spin and pseudospin symmetries in the single-particle resonant states
Ting-Ting Sun · Wan-Li Lu · Long Qian · Yu-Xiao Li
We investigate the spin and pseudospin symmetry in the single-particle resonant states by solving the Dirac equation containing a Woods-Saxon potential with Green's function method. Taking double-magic nucleus $^{208}$ Pb as an example, three spin doublets $3 d$ , $2 h$ , and $1 j$ and three pseudospin doublets $3 p ~$ , $1 i ~$ , and $1 j ~$ are obtained for the single-neutron resonant states. By analyzing the energy splittings, we find that the threshold effect plays an important role in resonant pseudospin doubles. Besides, there is a reversed level structure of pseudospin doublets in the continuum. Differently, all the width splittings of either the spin doublets or the pseudospin doublets are systematically positive and the splittings are very small except $1 j ~$ doublet. Further studies show that the splittings of the energies and widths for the resonant (pseudo)spin doublets are independent. Besides, the similarity properties of the wave functions of the spin and pseudospin doublets still maintain well in resonant states.
Comments:
10 pages, 8 figures, 1 table. arXiv admin note: text overlap with arXiv:1710.02923
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1902.07442 [pdf]
PRC(2019)·21 citations
02
[Submitted on 20 Feb 2019]
Continuum Skyrme-Hartree-Fock-Bogoliubov theory with Green's function method for odd- $A$ nuclei
Ting-Ting Sun · Zi-Xin Liu · Long Qian · Bing Wang · Wei Zhang
To study the exotic odd nuclear systems, the self-consistent continuum Skyrme-Hartree-Fock-Bogoliubov theory formulated with Green's function technique is extended to include blocking effects with the equal filling approximation. Detailed formula are presented.To perform the integrals of the Green's function properly, the contour paths $C_{b}^{-}$ and $C_{b}^{+}$ introduced for the blocking effects should include the blocked quasi-particle state but can not intrude into the continuum area. By comparing with the box-discretized calculations, the great advantages of the Green's function method in describing the extended density distributions, resonant states, and the couplings with the continuum in exotic nuclei are shown. Finally, taking the neutron-rich odd nucleus $^{159}$ Sn as an example, the halo structure is investigated by blocking the quasi-particle state $1 p_{1/2}$ . It is found that it is mainly the weakly bound states near the Fermi surface that contribute a lot for the extended density distributions at large coordinate space.
Comments:
11 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1902.07518 [pdf]
PRC(2019)·15 citations
03
[Submitted on 20 Feb 2019]
Benchmarking a Non-Equilibrium Approach to Photon Emission in Relativistic Heavy-Ion Collisions
Anna Schäfer🇩🇪 · Juan M. Torres-Rincon🇺🇸 · Jonas Rothermel🇩🇪 · Niklas Ehlert🇩🇪 · Charles Gale🇨🇦 · Hannah Elfner🇩🇪
In this work, the production of photons through binary scattering processes is investigated for equilibrated hadronic systems. More precisely, a non-equilibrium hadronic transport approach to describe relativistic heavy-ion collisions is benchmarked with respect to photon emission. Cross sections for photon production in $π + ρ \to π + γ$ and $π + π \to ρ + γ$ scattering processes are derived from an effective chiral field theory and implemented into the hadronic transport approach, SMASH (Simulating Many Accelerated Strongly-interacting Hadrons). The implementation is verified by systematically comparing the thermal photon rate to theoretical expectations. Further, the impact of form factors is discussed, scattering processes mediated by $ω$ mesons are found to contribute significantly to the total photon production. Several comparisons of the yielded photon rates are performed: to parametrizations of the very same rates, as used in hydrodynamic simulations, to previous works relying on different cross sections for the production of direct photons from the hadronic stage, and to partonic rates. Finally, the impact of considering the finite width of the $ρ$ meson is investigated, where a significant enhancement of photon production in the low-energy region is observed. This benchmark is the first step towards a consistent treatment of photon emission in hybrid hydrodynamics+transport approaches and a genuine dynamical description.
Comments:
14 pages, 15 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1902.07564 [pdf]
PRD(2019)·26 citations
04
[Submitted on 20 Feb 2019]
A systematic study of the factors affecting central depletion in nuclei
G. Saxena · M. Kumawat · B. K. Agrawal · Mamta Aggarwal
A systematic study of the central depletion of proton density has been performed in the isotonic chains of nuclei with neutron numbers $N = 20$ and $28$ using different variants of the relativistic mean-field (RMF) models. These models include either the non-linear contributions from the mesons with the coupling constants being density independent or the non-linearity of the mesonic fields realized through the density dependent coupling strengths. The central depletion in deformed nuclei tends to disappear irrespective of the occupancy of $2 s_{1/2}$ state in contrast to the spherical nuclei in which the unoccupancy of $2 s_{1/2}$ state leads to the central depletion. Due to the differences in the strength of spin-orbit potentials in these models, the central depletions are found to be model dependent. The influence of the central depletion on the neutron-skin thickness is also investigated. It appears that the effects of the central depletion do not percolate far enough to display its finger prints on the trends of the neutron-skin thickness.
Comments:
17 pages, 9 figures, Accepted in Journal of Physics G: Nuclear and Particle Physics
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1902.07592 [pdf]
J.Phys.G(2019)·13 citations
05
[Submitted on 18 Feb 2019]
Calculation of an $A = 3$ bound-state matrix element in pionless effective field theory
Hilla De-Leon🇮🇱 · Lucas Platter🇺🇸 · Doron Gazit🇮🇱
In this paper, we establish a general framework for calculating pionless matrix elements between $A = 3$ bound-states up to next-to-leading-order. This framework is useful for pionless calculations of electroweak observables, such as $^{3}$ H, $^{3}$ He magnetic moments and $^{3}$ H $β$ decay. Starting from a Bethe-Salpeter equation, we prove that for a bound-state, the three-nucleon wave-function normalization can be expressed diagrammatically in a way that is equivalent to the unit operator between two identical three-nucleon bound-states. This diagrammatic form of the identity matrix element is the foundation for constructing an $A = 3$ matrix element of a general operator. We show that this approach can be used to calculate the energy difference between $^{3}$ H and $^{3}$ He due to the Coulomb interaction, and to calculate the NLO corrections to the $^{3}$ H and $^{3}$ He scattering amplitudes due to effective range corrections.
Comments:
27 pages, 12 figures. arXiv admin note: text overlap with arXiv:1611.10004
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1902.07677 [pdf]
4 citations
06
[Submitted on 19 Feb 2019] (cross-list from hep-th)
Holographic Signatures of Critical Collapse
Paul M. Chesler🇺🇸 · Benson Way🇨🇦
Critical phenomena in gravitational collapse exhibit the universal features of self-similarity, critical scaling, and the appearance of a naked singularity. We study critical collapse in AdS, focusing on holographic field theory observables. We demonstrate that the echoing period, critical exponent, and signatures of the naked singularity can all be extracted from the holographic stress tensor.
Comments:
5 pages, 7 figures, published version
Subjects:
High Energy Physics — Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1902.07218 [pdf]
PRL(2019)·11 citations
07
[Submitted on 20 Feb 2019] (cross-list from hep-ph)
Conference Summary of QNP2018
S. Kumano (KEK/J-PARC)🇯🇵
This report is the summary of the Eighth International Conference on Quarks and Nuclear Physics (QNP2018). Hadron and nuclear physics is the field to investigate high-density quantum many-body systems bound by strong interactions. It is intended to clarify matter generation of universe and properties of quark-hadron many-body systems. The QNP is an international conference which covers a wide range of hadron and nuclear physics, including quark and gluon structure of hadrons, hadron spectroscopy, hadron interactions and nuclear structure, hot and cold dense matter, and experimental facilities. First, I introduce the current status of the hadron and nuclear physics field related to this conference. Next, the organization of the conference is explained, and a brief overview of major recent developments is discussed by selecting topics from discussions at the plenary sessions. They include rapidly-developing field of gravitational waves and nuclear physics, hadron interactions and nuclear structure with strangeness, lattice QCD, hadron spectroscopy, nucleon structure, heavy-ion physics, hadrons in nuclear medium, and experimental facilities of EIC, GSI-FAIR, JLab, J-PARC, Super-KEKB, and others. Nuclear physics is at a fortunate time to push various projects at these facilities. However, we should note that the projects need to be developed together with related studies in other fields such as gravitational physics, astrophysics, condensed-matter physics, particle physics, and fundamental quantum physics.
Comments:
10 pages, LaTeX, 1 style file, 3 figure files, Proceedings of Eighth International Conference on Quarks and Nuclear Physics (QNP2018), November 13-17, 2018, Tsukuba, Japan
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1902.07368 [pdf]
JPS Conf.Proc.(2019)·0 citations
08
[Submitted on 20 Feb 2019] (cross-list from hep-ph)
Impact of form factor uncertainties on interpretations of coherent elastic neutrino-nucleus scattering data
D. Aristizabal Sierra🇨🇱 · Jiajun Liao🇨🇳 · D. Marfatia🇺🇸
The standard model coherent elastic neutrino-nucleus scattering (CE $ν$ NS) cross section is subject to nuclear form factor uncertainties, mainly driven by the root-mean-square radius of the neutron density distribution. Motivated by COHERENT phases I-III and future multi-ton direct detection dark matter searches, we evaluate these uncertainties in cesium iodide, germanium, xenon and argon detectors. We find that the uncertainties become relevant for momentum transfers $q ≳ 20$ MeV and are essentially independent of the form factor parameterization. Consequently, form factor uncertainties are not important for CE $ν$ NS induced by reactor or solar neutrinos. Taking into account these uncertainties, we then evaluate their impact on measurements of CE $ν$ NS at COHERENT, the diffuse supernova background (DSNB) neutrinos and sub-GeV atmospheric neutrinos. We also calculate the relative uncertainties in the number of COHERENT events for different nuclei as a function of recoil energy. For DSNB and atmospheric neutrinos, event rates at a liquid argon detector can be uncertain to more than 5%. Finally, we consider the impact of form factor uncertainties on searches for nonstandard neutrino interactions, sterile neutrinos and neutrino generalized interactions. We point out that studies of new physics using CE $ν$ NS data are affected by neutron form factor uncertainties, which if not properly taken into account may lead to the misidentification of new physics signals. The uncertainties quantified here are also relevant for dark matter direct detection searches.
Comments:
13 pages, 7 figures, 1 table. Version to appear in JHEP
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1902.07398 [pdf]
JHEP(2019)·104 citations
09
[Submitted on 20 Feb 2019] (cross-list from hep-th)
Nuclear states and spectra in holographic QCD
Koji Hashimoto🇯🇵 · Yoshinori Matsuo🇹🇼 · Takeshi Morita🇯🇵
A new method to study nuclear physics via holographic QCD is proposed. Multiple baryons in the Sakai-Sugimoto background are described by a matrix model which is a low energy effective theory of D-branes of the baryon vertices. We study the quantum mechanics of the matrix model and calculate the eigenstates of the Hamiltonian. The obtained states are found to coincide with known nuclear and baryonic states, and have appropriate statistics and charges. Calculated spectra of the baryon/nucleus for small baryon numbers show good agreement with experimental data. For hyperons, the Gell-Mann--Okubo formula is approximately derived. Baryon resonances up to spin $5/2$ and isospin $5/2$ and dibaryon spectra are obtained and compared with experimental data. The model partially explains even the magic numbers of light nuclei, $N = 2, 8$ and $20$ .
Comments:
65 pages; v2: 69 pages, discussions on the magic number are clarified; v3: 75 pages, published version
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1902.07444 [pdf]
JHEP(2019)·16 citations
10
[Submitted on 20 Feb 2019] (cross-list from hep-ph)
Neutron Skin in CsI and Low-Energy Effective Weak Mixing Angle from COHERENT Data
Xu-Run Huang🇨🇳 · Lie-Wen Chen🇨🇳
Both the neutron skin thickness $Δ R_{n p}$ of atomic nuclei and the low-energy neutrino-nucleon ( $ν N$ ) interactions are of fundamental importance in nuclear and particle physics, astrophysics as well as new physics beyond the standard model (SM) but largely uncertain currently, and the coherent elastic neutrino-nucleus scattering (CE $ν$ NS) provides a clean way to extract their information. New physics beyond the SM may cause effectively a shift of the SM weak mixing angle $θ_{W}$ in low-energy $ν N$ interactions, leading to an effective weak mixing angle $θ_{W}^{*}$ . By analyzing the CE $ν$ NS data of the COHERENT experiment, we find that while a one-parameter fit to the COHERENT data by varying $Δ R_{n p}$ produces $Δ R_{n p}^{CsI} ≃ 0.6 8_{- 1.13}^{+ 0.91}$ fm for CsI with an unrealistically large central value by fixing $sin^{2} θ_{W}^{*}$ at the low-energy SM value of $sin^{2} θ_{W}^{SM} = 0.23857$ , a two-dimensional fit by varying $Δ R_{n p}$ and $sin^{2} θ_{W}^{*}$ leads to a strong positive correlation between $Δ R_{n p}$ and $sin^{2} θ_{W}^{*}$ with significantly smaller central values of $Δ R_{n p}^{CsI} ≃ 0.2 4_{- 2.03}^{+ 2.30}$ fm and $sin^{2} θ_{W}^{*} = 0.2 1_{- 0.10}^{+ 0.13}$ . Although the uncertainty is too large to claim a determination of $Δ R_{n p}^{CsI}$ and $sin^{2} θ_{W}^{*}$ , the present study suggests that the multi-dimensional fit is important in future analyses of high-precision CE $ν$ NS data. The implication of the possible deviation of $sin^{2} θ_{W}^{*}$ from $sin^{2} θ_{W}^{SM}$ on new physics beyond the SM is also discussed.
Comments:
6 pages, 2 figures. Presentation improved and discussions added. Accepted version to appear in PRD as a Rapid Communication
Subjects:
High Energy Physics — Phenomenology (hep-ph); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1902.07625 [pdf]
PRD(2019)·45 citations
11
[Submitted on 20 Feb 2019] (cross-list from hep-ph)
Constraining energy loss from high- $p_{T}$ azimuthal asymmetries
Carlota Andres🇺🇸 · Néstor Armesto🇪🇸 · Harri Niemi🇫🇮 · Risto Paatelainen🇫🇮 · Carlos A. Salgado🇪🇸
The nuclear modification factor $R_{AA}$ has been satisfactorily described by various jet quenching models. Nonetheless, all these formalisms, until very recently, underpredicted the high- $p_{T}$ (> 10 GeV) elliptic flow $v_{2}$ . We find that the simultaneous description of these observables requires to strongly suppress the quenching for the first $\sim 0.6$ fm after the collision. This shows the potential of jet quenching observables to constrain the dynamics of the initial stages of the evolution.
Comments:
Proceedings of the Hard Probes 2018 conference. 4 pages. 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1902.07643 [pdf]
PoS(2019)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE