Nuclear Theory·nucl-th

Thursday·May 16, 2019

8 papers—5 primary·3 cross-listed

01
[Submitted on 15 May 2019]
Bound to unbound states transitions of heavy quarkonia in the cooling phase of QGP
Nirupam Dutta🇮🇳 · Partha Bagchi🇮🇳 · Jobin Sebastian🇮🇳
Emphasizing the possibility of moderate suppression of heavy quarkonium states, we invite some attention towards the issue of real time evolution of quarkonia during the cooling phase of quark gluon plasma(QGP). In this context, we have used time dependent perturbation theory to show that $Υ (1 S)$ , $Υ (2 S)$ , $J /Ψ$ can further be dissociated in the medium at a temperature below their dissociation thresholds even though they survive the Debye screening. We have presented and compared the dissociation probabilities and dissociation rates of these states in real and complex valued potential in this article. We realise that our method is an approximate way to analyse the short time behaviour of quarkonium in real valued potential and for long time behaviour one must adopt a non perturbative technique for solving schrödinger equation of quarkonium bound states in evolving QGP. On the other hand the perturbation technique seems to be valid enough to deal with the same for a complex valued quark anti-quark potential.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1905.06061 [pdf]
J.Subatomic Part.Cosmol.(2025)·4 citations
02
[Submitted on 15 May 2019]
Statistical properties of thermal neutron capture cross section calculated with randomly generated resonance parameters
N. Furutachi · F. Minato · O. Iwamoto
We investigated the probability distribution of the thermal neutron capture cross section ( $σ_{t h}$ ) deduced stochastically with the resonance parameters randomly sampled from Wigner and Porter-Thomas distributions. We found that the typical probability distribution has an asymmetric shape. While there is a long tail on the large $σ_{t h}$ side due to a resonance happening to be close to the thermal energy, the multi-resonance contribution considerably reduces the probability on the small $σ_{t h}$ side. We also found that the probability distributions have a similar shape if nuclei have an average resonance spacing sufficiently larger than an average radiation width. We compared the typical probability distribution with the distribution of the experimental values of 193 nuclei, and found a good agreement between them.
Comments:
8 pages, 6 figures, to be submitted to Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1905.06096 [pdf]
PRC(2019)·0 citations
03
[Submitted on 14 May 2019]
Rossby modes in neutron stars as sources of gravitational waves
Sujan Roy🇮🇳 · Somnath Mukhopadhyay🇮🇳 · Joydev Lahiri🇮🇳 · Debasis Atta · Partha Roy Chowdhury🇮🇳 · D. N. Basu🇮🇳
In the present work, we explore the Rossby mode instabilities in neutron stars as sources of gravitational waves. The intensity and time evolution of the emitted gravitational waves in terms of the amplitude of the strain tensor are estimated in the slow rotation approximation using $β$ -equilibrated neutron star matter obtained from density dependent M3Y effective interaction. For a wide range of neutron star masses, the fiducial gravitational and various viscous time scales, the critical frequencies and the time evolutions of the frequencies are calculated. The dissipative mechanism of the Rossby modes is considered to be driven by the shear viscosity along the boundary layer of the solid crust-liquid core interface as well as in the core and the bulk viscosity. It is found that neutron stars with slower frequency of rotation, for the same mass, radius and surface temperature, are expected to emit gravitational waves of higher intensity.
Comments:
9 pages including 8 figures and 1 table. arXiv admin note: text overlap with arXiv:1711.10794; text overlap with arXiv:1302.1204 by other authors
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1905.06158 [pdf]
Annals Phys.(2020)·6 citations
04
[Submitted on 15 May 2019]
Model-independent form-factor constraints for electromagnetic spin-1 currents
Helmut Haberzettl🇺🇸
Using local gauge invariance in the form of the Ward-Takahashi identity and the fact that properly constructed current operators must be free of kinematic singularities, it is shown that the magnetic moment $μ$ and the quadrupole moment $Q$ of an elementary spin-1 particle with mass $m$ and charge $e$ are related by $2 m μ + m^{2} Q = e$ , thus constraining the normalizations of the Sachs form factors. This relation holds true as a matter of course at the tree level in the standard model, but we prove it remains true in general for dressed spin-1 states derived from elementary fields. General expressions for spin-1 propagators and currents with arbitrary hadronic dressing are given showing the result to be independent of any dressing effect or model approach.
Comments:
Slightly revised version, as published in PRD. This version corrects an erroneous statement in the first version based on a numerical error
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1905.06299 [pdf]
PRD(2019)·11 citations
05
[Submitted on 15 May 2019]
Extrapolation of nuclear structure observables with artificial neural networks
W.G. Jiang · G. Hagen · T. Papenbrock
Calculations of nuclei are often carried out in finite model spaces. Thus, finite-size corrections enter, and it is necessary to extrapolate the computed observables to infinite model spaces. In this work, we employ extrapolation methods based on artificial neural networks for observables such as the ground-state energy and the point-proton radius. We extrapolate results from no-core shell model and coupled-cluster calculations to very large model spaces and estimate uncertainties. Training the network on different data typically yields extrapolation results that cluster around distinct values. We show that a preprocessing of input data, and the inclusion of correlations among the input data, reduces the problem of multiple solutions and yields more stable extrapolated results and consistent uncertainty estimates. We perform extrapolations for ground-state energies and radii in $^{4}$ He, $^{6}$ Li, and $^{16}$ O, and compare the predictions from neural networks with results from infrared extrapolations.
Comments:
9 pages, 8 figures, details added, accepted by Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1905.06317 [pdf]
PRC(2019)·57 citations
06
[Submitted on 15 May 2019] (cross-list from astro-ph.HE)
Roles of crust and core in the tidal deformability of neutron stars
A. M. Kalaitzis🇦🇺 · T. F. Motta🇦🇺 · A. W. Thomas🇦🇺
With the recent measurement of GW170817 providing constraints on the tidal deformability of a neutron star, it is very important to understand what features of the equation of state have the biggest effect on it. We therefore study the contribution of the crust to the tidal deformability and the moment of inertia of a neutron star for a variety of well-known equations of state. It is found that the contributions to these quantities from the low density crust are typically quite small and as a result the determination of the tidal deformability provides an important constraint on the equation of state of dense matter.
Comments:
5 pages, 5 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1905.05907 [pdf]
IJMPE(2019)·13 citations
07
[Submitted on 15 May 2019] (cross-list from hep-th)
Aspects of the QCD $θ$ -vacuum
Thomas Vonk🇩🇪 · Feng-Kun Guo🇨🇳 · Ulf-G. Meißner🇩🇪
This paper addresses two aspects concerning the $θ$ -vacuum of Quantum Chromodynamics. First, large- $N_{c}$ chiral perturbation theory is used to calculate the first two non-trivial cumulants of the distribution of the winding number, i.\,e. the topological susceptibility, $χ_{top}$ , and the fourth cumulant, $c_{4}$ , up to next-to-leading order. Their large- $N_{c}$ scaling is discussed, and compared to lattice results. It is found that $χ_{top} = O (N_{c}^{0})$ , as known before, and $c_{4} = O (N_{c}^{- 3})$ , correcting the assumption of $O (N_{c}^{- 2})$ in the literature. Second, we discuss the properties of QCD at $θ \sim π$ using chiral perturbation theory for the case of $2 + 1$ light flavors, i.\,e. by taking the strange quark mass heavier than the degenerate up and down quark masses. It is shown that --- in accordance with previous findings for $N_{f} = 2$ and $N_{f} = 3$ mass-degenerate flavors --- in the region $θ \sim π$ two vacuum states coexist, which become degenerate at $θ = π$ . The wall tension of the energy barrier between these degenerate vacua is determined as well as the decay rate of a false vacuum.
Comments:
Accepted for publication in JHEP. 35 pages, 5 figures
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1905.06141 [pdf]
JHEP(2019)·15 citations
08
[Submitted on 10 May 2019] (cross-list from nucl-ex)
Energy of the $^{229}$ Th nuclear clock transition
Benedict Seiferle · Lars von der Wense · Pavlo V. Bilous · Ines Amersdorffer · Christoph Lemell · Florian Libisch · Simon Stellmer · Thorsten Schumm · Christoph E. Düllmann · Adriana Pálffy · Peter G. Thirolf
The first nuclear excited state of $^{229}$ Th offers the unique opportunity for laser-based optical control of a nucleus. Its exceptional properties allow for the development of a nuclear optical clock which offers a complementary technology and is expected to outperform current electronic-shell based atomic clocks. The development of a nuclear clock was so far impeded by an imprecise knowledge of the energy of the $^{229}$ Th nuclear excited state. In this letter we report a direct excitation energy measurement of this elusive state and constrain this to 8.28 $\pm$ 0.17 eV. The energy is determined by spectroscopy of the internal conversion electrons emitted in-flight during the decay of the excited nucleus in neutral $^{229}$ Th atoms. The nuclear excitation energy is measured via the valence electronic shell, thereby merging the fields of nuclear- and atomic physics to advance precision metrology. The transition energy between ground and excited state corresponds to a wavelength of 149.7 $\pm$ 3.1 nm. These findings set the starting point for high-resolution nuclear laser spectroscopy and thus the development of a nuclear optical clock of unprecedented accuracy. A nuclear clock is expected to have a large variety of applications, ranging from relativistic geodesy over dark matter research to the observation of potential temporal variation of fundamental constants.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Instrumentation and Detectors (physics.ins-det)
arXiv:
1905.06308 [pdf]
Nature(2019)·152 citations

Affiliations

first authorsco-authorsvia INSPIRE