Nuclear Theory·nucl-th

Tuesday·September 15, 2020

17 papers—8 primary·9 cross-listed

09
[Submitted on 11 Sept 2020] (cross-list from hep-ph)
Signals of the QCD axion with mass of 17 MeV/c^2: nuclear transitions and light meson decays
Daniele S. M. Alves🇺🇸
The QCD axion remains experimentally viable in the mass range of O(10 MeV) if (i) it couples predominantly to the first generation of SM fermions; (ii) it decays to $e^{+} e^{-}$ with a short lifetime $τ_{a} ≲ 1 0^{- 13}$ s; and (iii) it has suppressed isovector couplings, i.e., if it is piophobic. Remarkably, these are precisely the properties required to explain recently observed anomalies in nuclear de-excitations, to wit: the $e^{+} e^{-}$ emission spectra of isoscalar magnetic transitions of $^{8}$ Be and $^{4}$ He nuclei showed a "bump-like" feature peaked at $m_{e^{+} e^{-}} \sim 17$ MeV. In this article, we argue that on-shell emission of the QCD axion (with the aforementioned properties) provides an extremely well-motivated, compatible explanation for the observed excesses in these nuclear de-excitations. The absence of anomalous features in other measured transitions is also naturally explained: piophobic axion emission is strongly suppressed in isovector magnetic transitions, and forbidden in electric transitions. This QCD axion hypothesis is further corroborated by an independent observation: a $2 - 3 σ$ deviation in the measurement of $Γ (π^{0} \to e^{+} e^{-})$ from the Standard Model theoretical expectation. This article also includes detailed estimations of various axionic signatures in rare light meson decays, which take into account contributions from low-lying QCD resonance exchange, and, in the case of rare Kaon decays, the possible effective implementations of $Δ S = 1$ octet enhancement in chiral perturbation theory. These inherent uncertainties of the effective description of the strong interactions at low energies result in large variations in the predictions for hadronic signals of the QCD axion; in spite of this, the estimated ranges for rare meson decay rates obtained here can be probed in the near future in $η / η^{'}$ and Kaon factories.
Comments:
V3: Two-column layout; 27 pages (22 pages + references); 5 figures. Revised NA64's upper bound on the axion lifetime, and added note commenting on this issue. Apart from this, V3 matches the content of the published version in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2009.05578 [pdf]
PRD(2021)·55 citations
10
[Submitted on 11 Sept 2020] (cross-list from hep-ph)
Coupled Transport Equations for Quarkonium Production in Heavy Ion Collisions
Xiaojun Yao🇺🇸 · Weiyao Ke🇺🇸 · Yingru Xu🇺🇸 · Steffen A. Bass🇺🇸 · Berndt Müller🇺🇸
Motivated by recent applications of the open quantum system formalism to understand quarkonium transport in the quark-gluon plasma, we develop a set of coupled Boltzmann equations for open heavy quark-antiquark pairs and quarkonia. Our approach keeps track of the correlation between the heavy quark-antiquark pair from quarkonium dissociation and thus is able to account for both uncorrelated and correlated recombination. By solving the coupled Boltzmann equations for current heavy ion collision experiments, we find correlated recombination is crucial to describe the data of bottomonia nuclear modification factors. To further test the importance of correlated recombination in experiments, we propose a new observable: $\frac{R _{AA} [ χ _{b} ( 1 P )]}{R _{AA} [ Υ ( 2 S )]}$ . Future measurements of this ratio will help distinguish calculations with and without correlated recombination.
Comments:
5 pages, 2 figures; proceedings for 10th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (Hard Probe 2020)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2009.05658 [pdf]
PoS(2021)·2 citations
11
[Submitted on 11 Sept 2020] (cross-list from astro-ph.SR)
The luminosity constraint in the era of precision solar physics
Diego Vescovi🇮🇹 · Carlo Mascaretti🇮🇹 · Francesco Vissani🇮🇹 · Luciano Piersanti🇮🇹 · Oscar Straniero🇮🇹
The luminosity constraint is a very precise relationship linking the power released by the Sun as photons and the solar neutrino fluxes. Such a relation, which is a direct consequence of the physical processes controlling the production and the transport of energy in the solar interior, is of great importance for the studies of solar neutrinos and has a special role for the search of neutrinos from the CNO cycle, whose first detection with a 5 $σ$ significance has been recently announced by the Borexino collaboration. Here we revise the luminosity constraint, discussing and validating its underlying hypotheses, in the light of latest solar neutrino and luminosity measurements. We generalize the current formulation of the luminosity constraint relation so that it can be easily used in future analysis of solar neutrino data, and we provide a specific application showing the link between CNO and pp neutrino fluxes.
Comments:
24 pages, 3 figures, 7 tables. Accepted for publication in JPhG
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2009.05676 [pdf]
J.Phys.G(2020)·11 citations
12
[Submitted on 12 Sept 2020] (cross-list from astro-ph.HE)
Constraint on phase transition with the multimessenger data of neutron stars
Shao-Peng Tang🇨🇳 · Jin-Liang Jiang🇨🇳 · Wei-Hong Gao🇨🇳 · Yi-Zhong Fan🇨🇳 · Da-Ming Wei🇨🇳
The equation of state (EoS) of the neutron star (NS) matter remains an enigma. In this work we perform the Bayesian parameter inference with the gravitational wave data (GW170817) and mass-radius observations of some NSs (PSR J0030+0451, PSR J0437-4715, and 4U 1702-429) using the phenomenologically constructed EoS models to search for a potential first-order phase transition. Our phenomenological EoS models take the advantages of current widely used parametrizing methods, which are flexible enough to resemble various theoretical EoS models. We find that the current observation data are still not informative enough to support/rule out phase transition, due to the comparable evidences for models with and without phase transition. However, the bulk properties of the canonical $1.4 M_{⊙}$ NS and the pressure at around $2 ρ_{sat}$ are well constrained by the data, where $ρ_{sat}$ is the nuclear saturation density. Moreover, strong phase transition at low densities is disfavored, and the $1 σ$ lower bound of transition density is constrained to $1.84 ρ_{sat}$ .
Comments:
9 pages, 5 figures, published in PRD
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2009.05719 [pdf]
PRD(2021)·33 citations
13
[Submitted on 12 Sept 2020] (cross-list from hep-ph)
Production of the bottomonium-like states $Z_{b}$ states at $e$ - $h$ and ultraperipheral $h$ - $h$ collisions
Xiao-Yun Wang🇨🇳 · Wei Kou🇨🇳 · Qing-Yong Lin🇨🇳 · Ya-Ping Xie🇨🇳 · Xurong Chen🇨🇳 · Alexey Guskov🇷🇺
The photoproduction of bottomonium-like states $Z_{b} (10610)$ and $Z_{b} (10650)$ via $γ p$ scattering is studied within an effectiv Lagrangian approach and the vector-meson-dominance model. The Regge model is employed to calculate the photoproduction of $Z_{b}$ states via $t$ -channel with $π$ exchange.The numerical results show that the values of the total cross-sections of $Z_{b} (10610)$ and $Z_{b} (10650)$ can reach 0.09 nb and 0.02 nb, respectively, near the center of mass energy of 22 GeV. The experimental measurements and studies on the photoproduction of $Z_{b}$ states near energy region around $W ≃ 22$ GeV is suggested. Moreover, with the help of eSTARlight and STARlight programs, one obtains the cross-sections and event numbers of $Z_{b} (10610)$ production in electron-ion collision (EIC) and Ultraperipheral collisions (UPCs). The results show that a considerable number of events from $Z_{b} (10610)$ can be produced on the relevant experiments of EICs and UPCs. Also, one calculates the rates and kinematic distributions for $γ p \to Z_{b} n$ in $e p$ and $p A$ collisions via EICs and UPCs, and the relevant results will provide an important reference for the RHIC, LHC, EIC-US, LHeC, and FCC experiments to search for the bottomonium-like $Z_{b}$ states.
Comments:
9 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2009.05789 [pdf]
CPC(2021)·2 citations
14
[Submitted on 13 Sept 2020] (cross-list from physics.atom-ph)
On deformability of atoms---comparative study between atoms and atomic nuclei
Tomoya Naito · Shimpei Endo · Kouichi Hagino · Yusuke Tanimura
Atomic nuclei can be spontaneously deformed into non-spherical shapes as many-nucleon systems. We discuss to what extent a similar deformation takes place in many-electron systems. To this end, we employ several many-body methods, such as the unrestricted Hartree-Fock method, post-Hartree-Fock methods, and the density functional theory, to compute the electron density distribution in atoms. We show that the electron density distribution of open-shell atoms is deformed due solely to the single-particle valence orbitals, while the core part remains spherical. This is in contrast to atomic nuclei, which can be deformed collectively. We qualitatively discuss the origin for this apparent difference between atoms and nuclei by estimating the energy change due to deformation. We find that nature of the interaction plays an essential role for the collective deformation.
Comments:
48 pages, 7 figures, 13 tables
Subjects:
Atomic Physics (physics.atom-ph); cond-mat.other (cond-mat.other); Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
arXiv:
2009.05955 [pdf]
J.Phys.B(2021)·2 citations
15
[Submitted on 14 Sept 2020] (cross-list from hep-ph)
Tribaryons in a constituent quark model
Aaron Park🇰🇷 · Su Houng Lee🇰🇷
We calculate the matrix elements of the color-spin interaction for all possible multi-quark states of tribaryons in flavor SU(3) broken case. For that purpose, we construct the flavor $\otimes$ color $\otimes$ spin wave functions of the tribaryons, which are taken to be antisymmetric to satisfy the Pauli exclusion principle. Furthermore, we analyze the diquark structure of the tribaryon configurations using the symmetric and antisymmetric basis set of flavor, color and spin states.
Comments:
13 pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2009.06220 [pdf]
PRD(2020)·3 citations
16
[Submitted on 14 Sept 2020] (cross-list from hep-ph)
Suppression of decay widths in singly heavy baryons induced by the $U_{A} (1)$ anomaly
Yohei Kawakami🇯🇵 · Masayasu Harada🇯🇵 · Makoto Oka🇯🇵 · Kei Suzuki🇯🇵
We study strong and radiative decays of excited singly heavy baryons (SHBs) using an effective chiral Lagrangian based on the diquark picture proposed in Ref. [1]. The effective Lagrangian contains a $U_{A} (1)$ anomaly term, which induces an inverse mass ordering between strange and non-strange SHBs with spin-parity $1/ 2^{-}$ . We find that the effect of the $U_{A} (1)$ anomaly combined with flavor-symmetry breaking modifies the Goldberger-Treiman relation for the mass difference between the ground state $Λ_{Q} (1/ 2^{+})$ and its chiral partner $Λ_{Q} (1/ 2^{-})$ , and $Λ_{Q} (1/ 2^{-}) Λ_{Q} (1/ 2^{+}) η$ coupling, which results in suppression of the decay width of $Λ_{Q} (1/ 2^{-}) \to Λ_{Q} (1/ 2^{+}) η$ . We also investigate the other various decays such as $Λ_{Q} (1/ 2^{-}) \to Σ_{Q} (1/ 2^{+}, 3/ 2^{+}) π π$ , $Λ_{Q} (1/ 2^{-}) \to Σ_{Q} (1/ 2^{+}) π$ , $Λ_{Q} (1/ 2^{-}) \to Σ_{Q} (1/ 2^{+}, 3/ 2^{+}) γ$ , and $Λ_{Q} (1/ 2^{-}) \to Λ_{Q} (1/ 2^{+}) π^{0}$ for wide range of mass of $Λ_{Q} (1/ 2^{-})$ .
Comments:
9 pages, 6 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2009.06243 [pdf]
PRD(2020)·14 citations
17
[Submitted on 2 Aug 2020] (cross-list from nlin.PS)
The solitary wave in advanced nuclear energy system
Jin Feng Huang
The solitary wave naturally arises in many areas of mathematical physics, including in nonlinear optics, plasma physics, quantum field theory, and fluid mechanics. In the past few years, for an advanced nuclear energy system, a particular class of traveling wave reactor called the Constant Axial shape of Neutron flux, nuclide number densities and power shape During Life of Energy production (CANDLE) reactor has been proposed, and an analytical solution has been desired since it could reveal the global characters of the solution. In this study, from the perspective of the solitary wave, the analytical solution of this advanced nuclear energy system is demonstrated through coupling the one-group neutron diffusion equation with the burnup equation. The tanh-function method is applied to solve that nonlinear partial differential equation. The relationship between the velocity of the solitary wave, wave amplitude, or neutron flux and the evolution of the nuclide is revealed by the analytical method. The results demonstrate that the neutron flux is proportional to the wave velocity. The results also imply that the amplitude of the neutron flux is proportional to the square root of the diffusion coefficient but is inversely proportional to the initial 238U density.
Comments:
22 pages, 6 figures
Subjects:
nlin.PS (nlin.PS); Nuclear Theory (nucl-th); Plasma Physics (physics.plasm-ph)
arXiv:
2009.06359 [pdf]
Nucl.Sci.Eng.(2022)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE