Nuclear Theory·nucl-th

Monday·March 2, 2020

10 papers—5 primary·5 cross-listed

01
[Submitted on 27 Feb 2020]
$β$ decay of even-A nuclei within the interacting boson model based on nuclear density functional theory
K. Nomura🇭🇷 · R. Rodríguez-Guzmán🇰🇼 · L. M. Robledo🇪🇸
We compute the $β$ -decay $f t$ -values within the frameworks of the energy density functional (EDF) and the interacting boson model (IBM). Based on the constrained mean-field calculation with the Gogny-D1M EDF, the IBM Hamiltonian for an even-even nucleus and essential ingredients of the interacting boson-fermion-fermion model (IBFFM) for describing the neighboring odd-odd nucleus are determined in a microscopic way. Only the boson-fermion and residual neutron-proton interaction strengths are determined empirically. The Gamow-Teller (GT) and Fermi (F) transition rates needed to compute the $β$ -decay $f t$ -values are obtained without any additional parameter or quenching of the $g_{A}$ factor. The observed $\ft$ values for the $β^{+}$ decays of the even-even Ba into odd-odd Cs nuclei, and of the odd-odd Cs to the even-even Xe nuclei, with mass $A \approx 130$ are reasonably well described. The predicted GT and F transition rates represent a sensitive test of the quality of the IBM and IBFFM wave functions.
Comments:
10 pages, 2 figures, 4 tables. arXiv admin note: text overlap with arXiv:1912.01846
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2002.12357 [pdf]
PRC(2020)·19 citations
02
[Submitted on 27 Feb 2020]
Neutral baryonic systems with strangeness
H. Garcilazo🇲🇽 · A. Valcarce🇪🇸 · J. Vijande🇪🇸
We review the status as regards the existence of three- and four-body bound states made of neutrons and $Λ$ hyperons. For interesting cases, the coupling to neutral baryonic systems made of charged particles of different strangeness has been addressed. There are strong arguments showing that the $Λ nn$ system has no bound states. $ΛΛ nn$ strong stable states are not favored by our current knowledge of the strangeness $- 1$ and $- 2$ baryon-baryon interactions. However, a possible $Ξ^{-} t$ quasibound state decaying to $ΛΛ nn$ might exist in nature. Similarly, there is a broad agreement about the nonexistence of $ΛΛ n$ bound states. However, the coupling to $Ξ N N$ states opens the door to a resonance above the $ΛΛ n$ threshold.
Comments:
Invited Review. 22 pages. arXiv admin note: text overlap with arXiv:1911.07194"
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2002.12365 [pdf]
IJMPE(2020)·1 citation
03
[Submitted on 27 Feb 2020]
Dalitz plots and lineshape of $a_{1} (1260)$ from a relativistic three-body unitary approach
Daniel Sadasivan🇺🇸 · Maxim Mai🇺🇸 · Hakan Akdag🇩🇪 · Michael Döring🇺🇸
We formulate the final state interaction of the $a_{1} (1260)$ resonance decay in a manifestly three-body unitary parameterization and fit it to the $a_{1} (1260)$ lineshape measured by the ALEPH experiment. Dalitz plots calculated from this fit are presented. The work demonstrates the feasibility to numerically solve a previously derived amplitude and its generalization to isobars with spin and coupled channels. The model can also be applied to other meson decays and modified for the finite-volume problem as it arises in lattice QCD due to its manifest unitarity.
Comments:
14 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2002.12431 [pdf]
PRD(2020)·36 citations
04
[Submitted on 28 Feb 2020]
System response to the initial energy-momentum tensor in relativistic heavy-ion collisions
Jefferson Sousa🇧🇷 · Jorge Noronha🇺🇸 · Matthew Luzum🇧🇷
The evolution of a relativistic heavy-ion collision is typically understood as a process that transmutes the initial geometry of the system into the final momentum distribution of observed hadrons, which can be described via a cumulant expansion of the initial distribution of energy density and is represented at leading order as the well-known eccentricity scaling of anisotropic flow. We summarize a proposed extension of this framework to include the contribution from initial momentum-space properties, as encoded in other components of the energy-momentum tensor. Numerical tests validate this proposal.
Comments:
Proceedings for Quark Matter 2019
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2002.12735 [pdf]
NPA(2021)·4 citations
05
[Submitted on 28 Feb 2020]
Effects of high- $j$ orbitals, pairing and deformed neutron shells on upbendings of ground-state bands in neutron-rich even-even isotopes $^{170 - 184}$ Hf
Xiao-Tao He · Yang Cao · Xiao-Ling Gan
The ground-state bands (GSBs) in the even-even hafnium isotopes $^{170 - 184}$ Hf are investigated by using the cranked shell model (CSM) with pairing correlations treated by the particle-number conserving (PNC) method. The experimental kinematic moments of inertia are reproduced very well by theoretical calculations. The second upbending of the GSB at high frequency $ℏ ω \approx 0.5$ MeV observed (predicted) in $^{172}$ Hf ( $^{170, 174 - 178}$ Hf) attributes to the sudden alignments of the proton high- $j$ orbitals $π 1 i_{13/2}$ $(1/ 2^{+} [660])$ , $π 1 h_{9/2}$ $(1/ 2^{-} [541])$ and orbital $π 1 h_{11/2}$ $(7/ 2^{-} [523])$ . The first upbendings of GSBs at low frequency $ℏ ω = 0.2 - 0.3$ MeV in $^{170 - 178}$ Hf, which locate below the deformed neutron shell $N = 108$ , attribute to the alignment of the neutron orbital $ν 1 i_{13/2}$ . For the heavier even-even isotopes $^{180 - 184}$ Hf, compared to the lighter isotopes, the first band-crossing is delayed to the high frequency due to the existence of the deformed shells $N = 108, 116$ . The upbendings of GSBs in $^{180 - 184}$ Hf are predicted to occur at $ℏ ω \approx 0.5$ MeV, which come from the sharp raise of the simultaneous alignments of both proton $π 1 i_{13/2}$ , $π 1 h_{9/2}$ and neutron $ν 2 g_{9/2}$ orbitals. The pairing correlation plays a very important role in the rotational properties of GSBs in even-even isotopes $^{180 - 184}$ Hf. Its effects on upbendings and band-crossing frequencies are investigated.
Comments:
14pages,12figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2002.12807 [pdf]
PRC(2020)·1 citation
06
[Submitted on 27 Feb 2020] (cross-list from hep-ph)
Influence of hadronic resonances on the chemical freeze-out in heavy-ion collisions
P. Alba🇩🇪 · V. Mantovani Sarti🇩🇪 · J. Noronha-Hostler🇺🇸 · P. Parotto🇺🇸 · I. Portillo-Vazquez🇩🇪 · C. Ratti🇺🇸 · J. M. Stafford🇺🇸
Detailed knowledge of the hadronic spectrum is still an open question, which has phenomenological consequences on the study of heavy-ion collisions. A previous lattice QCD study concluded that additional strange resonances are missing in the currently tabulated lists provided by the Particle Data Group (PDG). That study identified the list labeled PDG2016+ as the ideal spectrum to be used as an input in thermal-model-based analyses. In this work, we determine the effect of additional resonances on the freeze-out parameters of systems created in heavy-ion collisions. These parameters are obtained from thermal fits of particle yields and net-particle fluctuations. For a complete picture, we compare several hadron lists including both experimentally discovered and theoretically predicted states. We find that the inclusion of additional resonances mildly influences the extracted parameters -- with a general trend of progressively lowering the temperature -- but is not sufficient to close the gap in temperature between light and strange hadrons previously observed in the literature.
Comments:
13 pages, 8 figures, v2: typos corrected, references updated
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2002.12395 [pdf]
PRC(2020)·52 citations
07
[Submitted on 27 Feb 2020] (cross-list from hep-ph)
The dijet mass distribution in heavy ion collisions
Jared Reiten🇺🇸
In these proceedings, we review the production of both light and heavy flavor dijets in heavy ion collisions and highlight a promising observable to expose their distinct signatures. We propose the modification of dijet invariant mass distributions in heavy ion collisions as a novel observable that exhibits striking sensitivity to the quark-gluon plasma transport properties and heavy quark mass effects on in-medium parton showers. This observable has the advantage of amplifying the effects of jet quenching in contrast to conventional observables, such as the dijet momentum imbalance shift, which involve cancellations of such effects and, hence, result in less pronounced signals. Predictions are presented for Au+Au collisions at $s_{N N}$ = 200 GeV to guide the future sPHENIX program at the Relativistic Heavy Ion Collider.
Comments:
6 pages, 4 figures; Proceedings of the XLIX International Symposium on Multiparticle Dynamics
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2002.12442 [pdf]
EPJ Web Conf.(2020)·0 citations
08
[Submitted on 28 Feb 2020] (cross-list from hep-th)
Fractal structure of Yang-Mills fields
Airton Deppman🇧🇷 · Eugenio Megias🇪🇸 · Debora P. Menezes🇧🇷
The origin of non-extensive thermodynamics in physical systems has been under intense debate for the last decades. Recent results indicate a connection between non-extensive statistics and thermofractals. After reviewing this connection, we analyze how scaling properties of Yang-Mills theory allow the appearance of self-similar structures in gauge fields. The presence of such structures, which actually behave as fractals, allows for recurrent non-perturbative calculations of vertices. It is argued that when a statistical approach is used, the non-extensive statistics is obtained, and the Tsallis entropic index, $q$ , is deduced in terms of the field theory parameters. The results are applied to QCD in the one-loop approximation, resulting in a good agreement with the value of $q$ obtained experimentally.
Comments:
12 pages, 4 figures. Talk given by E.Megias at the 8th International Conference on New Frontiers in Physics (ICNFP 2019), 21-29 Aug 2019, Kolymbari, Crete, Greece
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2002.12667 [pdf]
Phys.Scripta(2020)·7 citations
09
[Submitted on 28 Feb 2020] (cross-list from hep-ph)
Charge-dependent flow induced by electromagnetic fields in heavy ion collisions
U. Gürsoy🇳🇱 · D.E. Kharzeev🇺🇸 · E. Marcus🇳🇱 · K. Rajagopal🇺🇸 · C. Shen🇺🇸
The colliding heavy ions create extremely strong magnetic and electric fields that significantly affect the evolution of the produced quark-gluon plasma (QGP). The knowledge of these fields is essential for establishing the role of topological fluctuations in the QGP through the chiral magnetic effect and related anomaly-induced phenomena. In this talk, we describe our work on the evolution of the QGP in electric and magnetic fields in the framework of hydrodynamics supplemented, in a perturbative fashion, by the dynamical electromagnetism. The evolution of the QGP fluid is described within the iEBE-VISHNU framework. We find that the electromagnetically induced currents result in a charge-odd directed flow $Δ v_{1}$ and a charge-odd $Δ v_{3}$ flow both of which are odd in rapidity. While the predicted magnitude of these charge-odd flows agrees with the data from RHIC and LHC, the sign of the predicted asymmetry between the flows of positive and negative hadrons is opposite to the data.
Comments:
4 pages, 3 figures, contribution to the proceedings of Quark Matter 2019 conference
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2002.12818 [pdf]
NPA(2021)·4 citations
10
[Submitted on 28 Feb 2020] (cross-list from astro-ph.HE)
Redshift factor and diffusive equilibrium of unbound neutrons in the single nucleus model of accreting neutron star crust
P.Haensel · J.L.Zdunik
Using a Wigner-Seitz approximation with spherical cells, we re-analyze a widely used single nucleus model of accreting neutron star crust. We calculate beta disequilibrium within the crust, which is sizable, and implies that neutron and baryon chemical potentials, $μ_{n}$ and $μ_{b}$ , are not equal. We include also non-equilibrium reactions, driven by matter compression, and proceeding in the reaction layers. The constancy of $e^{Φ} μ_{n}$ , where the spacetime metric component $g_{00} = e^{2Φ}$ , in the shells between the reaction layers is not applicable, because single electron captures are blocked, so that the neutron fraction is fixed, and therefore neutrons are not an independent component of the crust matter. The absence of neutron diffusion in the shells between the reaction layers, stems from the constancy of the neutron fraction (concentration) in these shells. In the reaction layers, the outward force resulting from neutron fraction gradient is balanced by the inward gravitational force acting on unbound neutrons. Neglecting the thickness of the reaction layers compared to the shell thickness, we obtain condition $e^{Φ (r)} f_{Q} (r) g (r) =$ constant, where $g$ is Gibbs energy per nucleon, undergoing discontinuous drops on the reaction surfaces, and $f_{Q} (r) g (r) = g (r)$ is a continuous function, due to the factor $f_{Q} (r)$ canceling the discontinuities (drops) in $g (r)$ . The function $f_{Q} (r)$ is calculated using the Tolman-Oppenheimer-Volkov equations from $f_{Q} (P)$ and $g (P)$ obtained from the equation of state (EOS) with discontinuites. The constancy of of $e^{Φ (r)} g (r)$ is an extension of the standard relation $e^{Φ (r)} μ_{b} (r) =$ constant, valid in hydrostatic equilibrium for catalyzed crust.
Comments:
To be submitted for publication. Remarks and comments on the present paper will be welcome by the authors
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2002.12827 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE