Nuclear Theory·nucl-th

Friday·August 3, 2018

10 papers—4 primary·6 cross-listed

01
[Submitted on 1 Aug 2018]
Pauli-principle driven correlations in four-neutron nuclear decays
P. G. Sharov🇷🇺 · L. V. Grigorenko🇷🇺 · A. Ismailova🇷🇺 · M. V. Zhukov🇸🇪
Mechanism of simultaneous non-sequential four-neutron ( $4 n$ ) emission (or `true' $4 n$ -decay) has been considered in phenomenological five-body approach. This approach is analogous to the model of the direct decay to the continuum often applied to $2 n$ - and $2 p$ -decays. It is demonstrated that $4 n$ -decay fragments should have specific energy and angular correlations reflecting strong spatial correlations of `valence' nucleons orbiting in their $4 n$ -precursors. Due to the Pauli exclusion principle, the valence neutrons are pushed to the symmetry-allowed configurations in the $4 n$ -precursor structure, which causes a `Pauli focusing' effect. Prospects of the observation of the Pauli focusing have been considered for the $4 n$ -precursors $^{7}$ H and $^{28}$ O. Fingerprints of their nuclear structure or/and decay dynamics are predicted.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1808.00513 [pdf]
JETP Lett.(2019)·6 citations
02
[Submitted on 1 Aug 2018]
Exact restoration of Galilei invariance in density functional calculations with quantum Monte Carlo
P. Massella🇮🇹 · F. Barranco🇪🇸 · D. Lonardoni🇺🇸 · A. Lovato🇮🇹 · F. Pederiva🇮🇹 · E. Vigezzi🇮🇹
Galilean invariance is usually violated in self-consistent mean-field calculations that employ effective density-dependent nuclear forces. We present a novel approach, based on variational quantum Monte Carlo techniques, suitable to preserve this symmetry and assess the effect of its violation, seldom attempted in the past. To this aim, we generalize the linear optimization method to encompass the density-dependence of effective Hamiltonians, and study $^{4}$ He, $^{16}$ O, and $^{40}$ Ca ground-state properties employing the Gogny interaction.
Comments:
24 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1808.00518 [pdf]
J.Phys.G(2020)·15 citations
03
[Submitted on 1 Aug 2018]
Empirical signatures of shape phase transitions in nuclei with odd nucleon numbers
D. Bucurescu🇷🇴 · N.V. Zamfir🇷🇴
Nuclear level density at low excitation energies is proposed as an indicator of the first order phase transitions in nuclei. The new signature, a maximum value of the level density at the critical point, appears to be sensitive to the detailed way the phase transition takes place in different nuclear regions: it is consistent with phase coexistence in the N=90 region, and with a rapid crossing of the two phases, without their coexistence/mixing at the critical point in the N=60 region, respectively. Candidates for critical point nuclei are proposed for odd-mass and odd-odd nuclei, using correlations between relative excitation energies, and their ratios, for structures (bands) based on unique-parity orbitals.
Comments:
This manuscript has been published in Phys. Rev. C 98, 024301 (2018). This is the preprint version
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1808.00526 [pdf]
PRC(2018)·11 citations
04
[Submitted on 2 Aug 2018]
Direct and indirect $α$ transfer in the elastic $^{16}$ O+ $^{12}$ C scattering
Nguyen Tri Toan Phuc · Nguyen Hoang Phuc · Dao T. Khoa
The extensive elastic $^{16}$ O+ $^{12}$ C scattering data measured at low energies show consistently an oscillating enhancement of the elastic cross section at backward angles that is difficult to describe within the conventional optical model. Given the significant $α$ spectroscopic factors predicted for the dissociation $^{16}$ O $\to α +^{12}$ C by the shell model (SM) and $α$ -cluster model calculations, the contribution of the $α$ transfer channels to the elastic $^{16}$ O+ $^{12}$ C scattering should not be negligible, and is expected to account for the enhanced oscillation of the elastic cross section at backward angles. To reveal the impact of the $α$ transfer, a systematic coupled reaction channels (CRC) analysis of the elastic $^{16}$ O+ $^{12}$ C scattering has been performed where the multistep couplings between the elastic and inelastic scattering channels, the direct and indirect $α$ transfer channels were treated explicitly, using the real optical potentials and inelastic scattering form factors determined by the double-folding model. We show that a consistent CRC description of the elastic $^{16}$ O+ $^{12}$ C data at different energies can be obtained over the whole angular region, using the $α$ spectroscopic factors determined recently in the large scale SM calculation. The present CRC results are, therefore, of interest not only for the nuclear scattering studies but also provide an important spectroscopic information on the cluster dissociation of $^{16}$ O.
Comments:
Accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1808.00651 [pdf]
PRC(2018)·15 citations
05
[Submitted on 1 Aug 2018] (cross-list from astro-ph.HE)
Long-term GRMHD Simulations of Neutron Star Merger Accretion Disks: Implications for Electromagnetic Counterparts
Rodrigo Fernández🇨🇦 · Alexander Tchekhovskoy🇺🇸 · Eliot Quataert🇺🇸 · Francois Foucart🇺🇸 · Daniel Kasen🇺🇸
We investigate the long-term evolution of black hole accretion disks formed in neutron star mergers. These disks expel matter that contributes to an $r$ -process kilonova, and can produce relativistic jets powering short gamma-ray bursts. Here we report the results of a three-dimensional, general-relativistic magnetohydrodynamic (GRMHD) simulation of such a disk which is evolved for long enough ( $\sim 9$ s, or $\sim 6 \times 1 0^{5} r_{g} / c$ ) to achieve completion of mass ejection far from the disk. Our model starts with a poloidal field, and fully resolves the most unstable mode of the magnetorotational instability. We parameterize the dominant microphysics and neutrino cooling effects, and compare with axisymmetric hydrodynamic models with shear viscosity. The GRMHD model ejects mass in two ways: a prompt MHD-mediated outflow and a late-time, thermally-driven wind once the disk becomes advective. The total amount of unbound mass ejected ( $0.013 M_{⊙}$ , or $≃ 40%$ of the initial torus mass) is twice as much as in hydrodynamic models, with higher average velocity ( $0.1 c$ ) and a broad electron fraction distribution with a lower average value ( $0.16$ ). Scaling the ejected fractions to a disk mass of $\sim 0.1 M_{⊙}$ can account for the red kilonova from GW170817 but underpredicts the blue component. About $\sim 1 0^{- 3} M_{⊙}$ of material should undergo neutron freezout and could produce a bright kilonova precursor in the first few hours after the merger. With our idealized initial magnetic field configuration, we obtain a robust jet and sufficient ejecta with Lorentz factor $\sim 1 - 10$ to (over)produce the non-thermal emission from GW1708107.
Comments:
accepted by MNRAS, reorganized discussion of hydro vs MHD and initial conditions, updated Figs 9 and 12 to illustrate effect of unbinding criterion and low density cut
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1808.00461 [pdf]
MNRAS(2019)·290 citations
06
[Submitted on 2 Aug 2018] (cross-list from hep-ph)
Transition radiation as a probe of chiral anomaly
Xu-Guang Huang🇨🇳 · Kirill Tuchin🇺🇸
A fast charged particle crossing the boundary between the chiral matter and vacuum radiates the transition radiation. Its most remarkable features --- the resonant behavior at a certain emission angle and the circular polarization of the spectrum --- depend on the parameters of the chiral anomaly in a particular material/matter. The chiral transition radiation can be used to investigate the chiral anomaly in such diverse media as the quark-gluon plasma, the Weyl semimetals, and the axionic dark matter.
Comments:
6 pages; v2: typo fixed, discussion added
Subjects:
High Energy Physics — Phenomenology (hep-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Nuclear Theory (nucl-th)
arXiv:
1808.00635 [pdf]
PRL(2018)·20 citations
07
[Submitted on 2 Aug 2018] (cross-list from hep-ph)
Initial correlations of the Glasma energy-momentum tensor
Javier L. Albacete🇪🇸 · Pablo Guerrero-Rodríguez🇪🇸 · Cyrille Marquet🇫🇷
We present an analytical calculation of the covariance of the energy-momentum tensor associated to the gluon field produced in ultra-relativistic heavy ion collisions at early times, the Glasma. This object involves the two-point and single-point correlators of the energy-momentum tensor ( $⟨ T^{μν} (x_{⊥}) T^{σ ρ} (y_{⊥})⟩$ and $⟨ T^{μν} (x_{⊥})⟩$ , respectively) at proper time $τ = 0^{+}$ . Our approach is based on the Color Glass Condensate effective theory, which allows us to map the fluctuations of the valence color sources in the colliding nuclei to those of the energy-momentum tensor of the produced gluon fields via the solution of the classical equations of motion in the presence of external currents. The color sources in the two colliding nuclei are characterized by Gaussian correlations, albeit in more generality than in the McLerran-Venugopalan model, allowing for non-trivial impact parameter and transverse dependence of the two-point correlator. We compare our results to those obtained under the Glasma Graph approximation, finding agreement in the limit of short transverse separations. However, important differences arise at larger transverse separations, where our result displays a slower fall-off than the Glasma Graph result ( $r^{- 2}$ vs $r^{- 4}$ power-law decay), indicating that the color screening of the correlations in the transverse plane occurs at distances larger than $1/ Q_{s}$ by a logarithmic factor sensitive to the infrared. In the Glasma flux tube picture, this implies that the color domains are larger than originally estimated.
Comments:
Final published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1808.00795 [pdf]
JHEP(2019)·34 citations
08
[Submitted on 1 Aug 2018] (cross-list from hep-ph)
$p_{t}$ - dependence of the flow coefficients for pp collisions in the color string scenario. Monte-Carlo simulations
M.A. Braun🇷🇺 · C. Pajares🇪🇸
In the color string picture with fusion and percolation the dependence of the flow coefficients $v_{n}$ on the transverse momentum is studied for pp collisions the LHC energy respectively. Monte-Carlo simulations are used to locate simple strings and their fused clusters. The results favorably agree with the CMS data in the region $0.2 \leq p_{t} \leq 3.$ GeV/c appropriate for the string scenario.
Comments:
10 pages, 6 figures. arXiv admin note: text overlap with arXiv:1407.4590
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1808.00833 [pdf]
EPJA(2018)·5 citations
09
[Submitted on 2 Aug 2018] (cross-list from hep-ph)
Electron-photon deep inelastic scattering at small x in holographic QCD
Akira Watanabe🇨🇳 · Hsiang-nan Li🇹🇼
We study the electron-photon deep inelastic scattering at small Bjorken variable x in the framework of holographic QCD, employing the Pomeron exchange to describe the involved strong interaction. With the Brower-Polchinski-Strassler-Tan Pomeron exchange kernel and appropriate wave functions for the incident and target particles, which are defined in the five-dimensional AdS space, we obtain the photon structure functions. It is shown that our predictions agree with the experimental data measured at LEP and with those derived from a known parameterization of the photon parton distribution functions.
Comments:
7 pages, 4 figures, prepared for the proceedings of the XXVI International Workshop on Deep Inelastic Scattering and Related Subjects (DIS2018)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1808.00918 [pdf]
PoS(2018)·0 citations
10
[Submitted on 2 Aug 2018] (cross-list from hep-ph)
Semi-inclusive back-to-back production of a hadron pair and a single hadron in $e^{+} e^{-}$ annihilation
Hrayr H. Matevosyan🇦🇺 · Aram Kotzinian🇦🇲 · Anthony W. Thomas🇦🇺
Inclusive hadron production in $e^{+} e^{-}$ annihilation has long been used to study both single hadron fragmentation functions (FF) and dihadron fragmentation functions (DiFF). In particular, the polarized DiFFs can be accessed in electron-positron annihilation by measuring azimuthal correlations between two back-to-back pairs of hadrons in the center of mass system, where the relevant structure functions can be expressed as convolutions of two (polarized) DiFFs. Here we explore the advantages of measuring the inclusive back-to-back production of a single hadron on one side against a hadron pair on the opposite side of the detector in two jet events. The leading twist cross section for this process contains convolutions of the corresponding single hadron FFs on one side and the DiFFs for the hadron pair on the other side, which furnishes several interesting new opportunities. A measurement of the unpolarized cross section with a number of different types of observed hadrons will help in untangling the quark flavor dependence of the unpolarized DiFFs, when the results are analyzed together with the inclusive measurements of dihadron pairs, such as those recently performed by the $BELLE$ collaboration. Even more interesting, with a polarized hyperon on one side we can study the quark spin-dependent DiFFs of an unpolarized hadron pair on the other side. This, in turn, will allow us to test the universality of the spin-dependent DiFFs entering the cross sections of electron-positron annihilation and semi-inclusive deep inelastic scattering processes.
Comments:
21 pages, 1 figure. V2: Updated to version published in JHEP with minor revisions of the text, corrected typos and an additional reference
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1808.00954 [pdf]
JHEP(2018)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE