Nuclear Theory·nucl-th

Tuesday·January 12, 2021

13 papers—7 primary·6 cross-listed

01
[Submitted on 8 Jan 2021]
Implications of PREX-II on the equation of state of neutron-rich matter
Brendan T. Reed🇺🇸 · F. J. Fattoyev🇺🇸 · C. J. Horowitz🇺🇸 · J. Piekarewicz🇺🇸
Laboratory experiments sensitive to the equation of state of neutron rich matter in the vicinity of nuclear saturation density provide the first rung in a "density ladder" that connects terrestrial experiments to astronomical observations. In this context, the neutron skin thickness of 208Pb (Rskin) provides a stringent laboratory constraint on the density dependence of the symmetry energy. In turn, an improved value of Rskin has been reported recently by the PREX collaboration. Exploiting the strong correlation between Rskin and the slope of the symmetry energy L within a specific class of relativistic energy density functionals, we report a value of L=(106 +/- 37)MeV -- that systematically overestimates current limits based on both theoretical approaches and experimental measurements. The impact of such a stiff symmetry energy on some critical neutron-star observables is also examined.
Comments:
5 pages, 4 figures. Manuscript accepted for publication in the Physical Review Letters
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
2101.03193 [pdf]
PRL(2021)·574 citations
02
[Submitted on 9 Jan 2021]
NMEs for $0 ν β β (0^{+} \to 2^{+})$ of two-nucleon mechanism for $^{76}$ Ge
Dong-Liang Fang🇨🇳 · Amand Faessler🇩🇪
In this work we present the first beyond closure calculation for the neutrinoless double beta decay ( $0 ν β β$ ) of $^{76}$ Ge to the first $2^{+}$ states of $^{76}$ Se. The isospin symmetry restored Quasi-particle random phase approximation (QRPA) method with the CD-Bonn realistic force is adopted for the nuclear structure calculations. We analyze the structure of the two nucleon mechanism nuclear matrix elements, and estimate the uncertainties from the nuclear many-body calculations. We find $g_{pp}$ plays an important role for the calculations and if quenching is included, suppression for the transition matrix element $M_{λ}$ is found. Our results for the transition matrix elements are about one order of magnitude larger than previous projected Hatree-Fock-Boglyubov results with the closure approximation.
Comments:
10 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2101.03299 [pdf]
PRC(2021)·9 citations
03
[Submitted on 9 Jan 2021]
Angular Momentum of Fission Fragments from Microscopic Theory
Petar Marević🇺🇸 · Nicolas Schunck🇺🇸 · Jorgen Randrup🇺🇸 · Ramona Vogt🇺🇸
During nuclear fission, a heavy nucleus splits into two rotating fragments. The associated angular momentum is large, yet the mechanism of its generation and its dependence on the mass of fragments remain poorly understood. In this Letter, we provide the first microscopic calculations of angular momentum distributions in fission fragments for a wide range of fragment masses. For the benchmark case of $^{239}$ Pu( $n_{th}$ ,f), we find that the angular momentum of the fragments is largely determined by the nuclear shell structure and deformation, and that the heavy fragments therefore typically carry less angular momentum than their light partners. We use the fission model $FREYA$ to simulate the emission of neutrons and photons from the fragments. The dependence of the angular momenta on fragment mass after the emission of neutrons and statistical photons is linear for the heavy fragments and either constant or weakly linear for the light fragments, consistent with the universal sawtooth pattern suggested by recent experimental data. Finally, we observe that using microscopic angular momentum distributions modifies the number of emitted photons significantly.
Comments:
7 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2101.03406 [pdf]
PRC(2021)·53 citations
04
[Submitted on 10 Jan 2021]
Fission fragment mass yields of Th to Rf even-even nuclei
Krzysztof Pomorski · Jose M. Blanco · Pavel V. Kostryukov · Artur Dobrowolski · Bozena Nerlo-Pomorska · Michal Warda · Zhigang Xiao · Yongjing Chen · Lile Liu · Jun-Long Tian · Xinyue Diao · Qianghua Wu
Fission properties of the actinide nuclei are deduced from theoretical analysis. We investigate potential energy surfaces and fission barriers and predict the fission fragment mass-yields of actinide isotopes. The results are compared with experimental data where available. The calculations were performed in the macroscopic-microscopic approximation with the Lublin-Strasbourg Drop (LSD) for the macroscopic part and the microscopic energy corrections were evaluated in the Yukawa-folded potential. The Fourier nuclear shape parametrization is used to describe the nuclear shape, including the non-axial degree of freedom. The fission fragment mass-yields of considered nuclei are evaluated within a 3D collective model using the Born-Oppenheimer approximation.
Comments:
11 pages, 12 figures, submitted to the Chinese Physics C. arXiv admin note: text overlap with arXiv:2001.08652
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2101.03527 [pdf]
CPC(2021)·16 citations
05
[Submitted on 11 Jan 2021]
$Δ$ -admixed neutron stars: spinodal instabilities and dUrca processes
Adriana R. Raduta🇷🇴
Within the covariant density functional theory of nuclear matter we build equations of state of $Δ$ -admixed compact stars. Uncertainties in the interaction of $Δ (1232)$ resonance states with nuclear matter, due to lack of experimental data, are accounted for by varying the coupling constants to scalar and vector mesonic fields. We find that, over a wide range of the parameter space allowed by nuclear physics experiments and astrophysical observations, cold catalyzed star matter exhibits a first order phase transition which persists also at finite temperature and out of $β$ -equilibrium in the neutrino-transparent matter. Compact stars featuring such a phase transition in the outer core have small radii and, implicitly, tidal deformabilities. The parameter space is identified where simultaneously $Δ$ -admixed compact stars obey the astrophysical constraint on maximum mass and allow for dUrca processes, which is otherwise forbidden.
Comments:
9 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2101.03718 [pdf]
PLB(2021)·42 citations
06
[Submitted on 11 Jan 2021]
Nuclear reactions in artificial traps
Peng Guo🇨🇳 · Bingwei Long🇨🇳
Coupled-channel two-particle systems bound by a harmonic trap are discussed in the present paper. We derive the formula that relates the energy levels of such trapped systems to phase shifts and inelasticity of coupled-channel reactions. The formula makes it possible to extract amplitudes of inelastic nuclear reactions from ab initio calculations of discrete levels of many-nucleon systems in a harmonic trap.
Comments:
7 pages
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2101.03901 [pdf]
J.Phys.G(2022)·25 citations
07
[Submitted on 11 Jan 2021]
Quark matter contribution to the heat capacity of magnetized neutron stars
E. J. Ferrer🇺🇸 · V. de la Incera🇺🇸 · P. Sanson🇺🇸
In this paper, we find the heat capacity of the magnetic dual chiral density wave (MDCDW) phase of dense quark matter and use it to explore the feasibility of this phase for a neutron star interior. MDCDW is a spatially inhomogeneous phase of quark matter known to be favored at intermediate densities over the chirally symmetric phase and the color-flavor-locked superconducting phase. By comparing our result to the lower limit of the core heat capacity established from observations of transiently accreting neutron stars, we show that the heat capacity of MDCDW quark matter is well above that lower limit and hence cannot be ruled out. This result adds to a wealth of complementary investigations, all of which has served to strengthen the viability of a neutron star interior made of MDCDW quark matter. For completeness, we review the contributions to the heat capacity of the main neutron star ingredients at low, high and intermediate densities, with and without the presence of a magnetic field.
Comments:
To appear in PRD
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2101.04032 [pdf]
PRD(2021)·15 citations
08
[Submitted on 9 Jan 2021] (cross-list from hep-ph)
Studies on the $K^{*} Σ$ bound-state via $K^{+} p \to K^{+} ϕ p$
Seung-il Nam🇰🇷
In the present work, we investigate the hidden-strangeness production process in the $S = + 1$ channel via $K^{+} p \to K^{+} ϕ p$ , focussing on the exotic \textit{pentaquark} molecular $K^{*} Σ$ bound state, assigned by $P_{s}^{+} (2071, 3/ 2^{-})$ . For this purpose, we employ the effective Lagrangian approach in the tree-level Born approximation. Using the experimental and theoretical inputs for the exotic state and for the ground-state hadron interactions, the numerical results show a small but obvious peak structure from $P_{s}^{+}$ with the signal-to-background ratio $\approx 1.7 %$ , and it is enhanced in the backward-scattering region of the outgoing $K^{+}$ in the center-of-mass frame. We also find that the contribution from the $K^{*} (1680, 1^{-})$ meson plays an important role to reproduce the data. The proton-spin polarizations are taken into account to find a way to reduce the background. The effects of the possible $27$ -plet pentaquark $Θ_{27}^{++}$ is discussed as well.
Comments:
10 pages, 15 figures, accepted for publication via PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2101.03317 [pdf]
PRD(2021)·7 citations
09
[Submitted on 10 Jan 2021] (cross-list from hep-ph)
Hybrid nature of the abnormal solutions of the Bethe-Salpeter equation in the Wick-Cutkosky model
J. Carbonell · V.A. Karmanov ans H. Sazdjian
In the Wick-Cutkosky model, where two scalar massive constituents interact by means of the exchange of a scalar massless particle, the Bethe-Salpeter equation has solutions of two types, called "normal" and "abnormal". In the non-relativistic limit, the normal solutions correspond to the usual Coulomb spectrum, whereas the abnormal ones do not have non-relativistic counterparts -- they are absent in the Schrödinger equation framework. We have studied, in the formalism of the light-front dynamics, the Fock-space content of the abnormal solutions. It turns out that, in contrast to the normal ones, the abnormal states are dominated by the massless exchange particles (by 90 \% or more), what provides a natural explanation of their decoupling from the two-body Schrödinger equation. Assuming that one of the massive constituents is charged, we have calculated the electromagnetic elastic form factors of the normal and abnormal states, as well as the transition form factors. The results on form factors confirm the many-body nature of the abnormal states, as found from the Fock-space analysis. The abnormal solutions have thus properties similar to those of hybrid states, made here essentially of two massive constituents and several or many massless exchange particles. They could also be interpreted as the Abelian scalar analogs of the QCD hybrid states. The question of the validity of the ladder approximation of the model is also examined.
Comments:
22 pages, 20 figures, 2 tables. Accepted in Eur. Phys. J. C
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2101.03566 [pdf]
EPJC(2021)·6 citations
10
[Submitted on 11 Jan 2021] (cross-list from hep-ph)
Light-front dynamic analysis of the longitudinal charge density using the solvable scalar field model in (1+1) dimensions
Yongwoo Choi🇰🇷 · Ho-Meoyng Choi🇰🇷 · Chueng-Ryong Ji🇺🇸 · Yongseok Oh🇰🇷
We investigate the electromagnetic form factor $F (q^{2})$ of the meson by using the solvable $ϕ^{3}$ scalar field model in $(1 + 1)$ dimensions. As the transverse rotations are absent in $(1 + 1)$ dimensions, the advantage of the light-front dynamics (LFD) with the light-front time $x^{+} = x^{0} + x^{3}$ as the evolution parameter is maximized in contrast to the usual instant form dynamics (IFD) with the ordinary time $x^{0}$ as the evolution parameter. In LFD, the individual $x^{+}$ -ordered amplitudes contributing to $F (q^{2})$ are invariant under the boost, i.e., frame-independent, while the individual $x^{0}$ -ordered amplitudes in IFD are not invariant under the boost but dependent on the reference frame. The LFD allows to get the analytic result for the one-loop triangle diagram which covers not only the spacelike ( $q^{2} < 0$ ) but also timelike region ( $q^{2} > 0$ ). Using the analytic results, we verify that the real and imaginary parts of the form factor satisfy the dispersion relations in the entire $q^{2}$ space. Comparing with the results in $(3 + 1)$ dimensions, we discuss the transverse momentum effects on $F (q^{2})$ . We also discuss the longitudinal charge density in terms of the boost invariant variable $z ~ = p^{+} x^{-}$ in LFD.
Comments:
15 pages, 12 figures; Slight changes have been made in the title and abstract. Version to appear in Phys. Rev. D
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2101.03656 [pdf]
PRD(2021)·5 citations
11
[Submitted on 11 Jan 2021] (cross-list from hep-ph)
Hot spots and gluon field fluctuations as causes of eccentricity in small systems
S. Demirci🇫🇮 · T. Lappi🇫🇮 · S. Schlichting🇩🇪
We calculate eccentricities in high energy proton-nucleus collisions, by calculating correlation functions of the energy density field of the Glasma immediately after the collision event at proper time tau = 0. We separately consider the effects of color charge and geometrical hot spot fluctuations, analytically performing the averages over both in a dilute-dense limit. We show that geometric fluctuations of hot spots inside the proton are the dominant source of eccentricity whereas color charge fluctuations only give a negligible correction. The size and number of hot spots are the most important parameters characterizing the eccentricities.
Comments:
21 pages, 9 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2101.03791 [pdf]
PRD(2021)·24 citations
12
[Submitted on 11 Jan 2021] (cross-list from hep-ph)
Remarks on Static Three-Quark Potentials, String Breaking and Gauge/String Duality
Oleg Andreev🇷🇺
Making use of the gauge/string duality, it is possible to study some aspects of the string breaking phenomenon in the three quark system. Our results point out that the string breaking distance is not universal and depends on quark geometry. The estimates of the ratio of the string breaking distance in the three quark system to that in the quark-antiquark system would range approximately from $\frac{2}{3}$ to $1$ . In addition, it is shown that there are special geometries which allow more than one breaking distance.
Comments:
v2: 30 pages, 19 figures, 1 table, discussion improved, title modified, references added, accepted version for PRD; v3: references updated
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2101.03858 [pdf]
PRD(2021)·22 citations
13
[Submitted on 11 Jan 2021] (cross-list from nucl-ex)
Experimental evidence of (M1+E2) mixed character of the 9.2 keV transition in $^{227}$ Th and its consequence for spin-interpretation of low-lying levels
A. Kovalík (1 and 2) · A. Kh. Inoyatov (1 and 3) · L. L. Perevoshchikov (1) · M. Ryšavý (2). D. V. Filosofov (1) · P. Alexa (4) · J. Kvasil (5) ((1) JINR Dubna, (2) NPI Řež near Prague, (3) Institute of Applied Physics, Tashkent, (4) Technical University, Ostrava, (5) Institute of Particle and Nuclear Physics, Prague)
The 9.2 keV nuclear transition in $^{227}$ Th populated in the $β$ -decay of $^{227}$ Ac was studied by means of the internal conversion electron spectroscopy. Its multipolarity was proved to be of mixed character M1+E2 and the spectroscopic admixture parameter $δ^{2}$ (E2/M1)=0.695 $\pm$ 0.248 (| $δ$ (E2/M1)|=0.834 $\pm$ 0.210) was determined. Nonzero value of $δ$ (E2/M1) raises a question about the existing theoretical interpretation of low-lying levels of $^{227}$ Th.
Comments:
14 pages, 3 figures; typo in abstract corrected
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2101.04075 [pdf]
PLB(2021)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE