Nuclear Theory·nucl-th

Friday·February 11, 2022

16 papers—7 primary·9 cross-listed

01
[Submitted on 9 Feb 2022]
Tensor force effect on the neutron shell closure in super-heavy elements
M. El Adri🇲🇦 · M. Oulne🇲🇦
A systematic study of the effect of tensor force on the evolution of shell structure in even-even super-heavy nuclei in the region of proton numbers Z=114, 120 and 126 and in the region of neutron numbers 178 $\leq$ N $\leq$ 188 is presented. We use, in this investigation, the Hartree-Fock framework by means of different types of Skyrme functionals in two cases with and without tensor force. The Bardeen-Cooper-Schriefer (BCS) approximation has been used to treat the pairing correlations. By investigating structural and decay properties of nuclei under consideration, it is found that N=184 shell gap is more enhanced by the tensor interaction which depends on the isoscalar tensor coupling constant $C_{0}^{J}$ of the used Skyrme interactions. In the case without tensor interaction, this gap is significant only for T22, T24, T42 and SLy5. So, it disappears with T46, T64 and T66, and is too weak for T26, T44 and T62. Without exception, the shell gap at N=184 becomes more pronounced when the tensor part is taken into account.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2202.04691 [pdf]
Eur.Phys.J.Plus(2021)·1 citation
02
[Submitted on 9 Feb 2022]
On the possible existence of a soft dipole mode in 8He
J. Piekarewicz
With an extreme neutron-to-proton ratio of N/Z=3, 8He provides an ideal laboratory for the study of a variety of exotic phenomena, such as the emergence of a soft dipole mode that is dominated by transitions into the continuum. In this contribution, a covariant density functional theory (DFT) framework is used to compute ground-state properties and the dipole response of 8He. Although 8He is admittedly too light for DFT to be applicable, the great merit of the approach is that the spurious contamination associated with the center-of-mass motion is guaranteed to decouple from the physical response. Given that a strong mixing between the isoscalar and isovector dipole modes is expected for a system with such a large neutron-proton asymmetry as 8He, the narrow structures that emerged at low energies in the isovector dipole response are attributed to the shift of the spurious strength to zero (or near zero) excitation energy. Thus, the theoretical framework implemented here disfavors the emergence of a soft dipole mode in 8He.
Comments:
8 pages, 7 figures, and two tables. Submitted to the Physical Review C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2202.04726 [pdf]
PRC(2022)·6 citations
03
[Submitted on 9 Feb 2022]
Weak pion-production and the second resonance region
D.F. Tamayo Agudelo🇨🇴 · A. Mariano🇦🇷 · D.E. Jaramillo Arango🇨🇴
In this work we report the calculation of the total cross section for pion-production by the dispersion of neutrinos on nucleons. We use a consistent formalism for the intermediate resonance states of spin $3/2$ , taking care on the conditions imposed by the invariance on contact transformations and using the Sachs parametrization for the form factors. In addition, we incorporate states in the second resonance region up to 1.6 GeV and implement different approaches for all the dressed resonance propagators. In addition to the $Δ$ (1232), we include the N $^{*}$ (1440),N $^{*}$ (1535)and N $^{*}$ (1520) resonance contributions, and it is shown that this inclusion improve the description of the total cross section regards a model where only the $Δ$ (1230) resonance is considered. Also results for antineutrinos are properly described.
Comments:
Manuscript has been accepted for publication as a Regular Article in Physical Review D
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2202.04760 [pdf]
PRD(2022)·3 citations
04
[Submitted on 10 Feb 2022]
Chiral condensates for neutron stars in hadron-quark crossover; from a parity doublet nucleon model to an NJL quark model
Takuya Minamikawa🇯🇵 · Toru Kojo🇨🇳 · Masayasu Harada🇯🇵
In this contribution, we summarize our recent studies on the chiral invariant mass and the chiral condensates in neutron star matter. We construct a unified equations of state assuming the crossover phase transition from hadronic matter described by a parity doublet model to quark matter by an Nambu--Jona-Lasinio type quark model. We first show that the chiral invariant mass is constrained to be 600 MeV $≲ m_{0} ≲$ 900 MeV from recent observations of neutron stars. We then determine the density dependence of the chiral condensate in the crossover description, and show that the chiral condensates are actually smoothly connected from the hadronic matter where the change is driven by the positive chiral scalar charge in a nucleon, to the quark matter where the change is by the modification of the quark Dirac sea, reflecting the hadron-quark crossover.
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2202.04873 [pdf]
Rev.Mex.Fis.Suppl.(2022)·2 citations
05
[Submitted on 10 Feb 2022]
Isospin symmetry breaking in the charge radius difference of mirror nuclei
Tomoya Naito · Xavier Roca-Maza · Gianluca Colò · Haozhao Liang · Hiroyuki Sagawa
Isospin symmetry breaking (ISB) effects in the charge radius difference $Δ R_{ch}$ of mirror nuclei are studied using the test example of $^{48}$ Ca and $^{48}$ Ni. This choice allows for a transparent study of ISB contributions since paring and deformation effects, commonly required for the study of mirror nuclei, can be neglected in this specific pair. The connection of $Δ R_{ch}$ with the nuclear Equation of State and the effect of ISB on such a relation are discussed according to an Energy Density Functional approach. We find that nuclear ISB effects may shift the estimated value for the symmetry energy slope parameter $L$ by more than 10 MeV while Coulomb corrections can be neglected. ISB effects on the ground-state energy and charge radii in mirror nuclei have been recently predicted by {\it ab initio} calculations to be relatively small, pointing to a negligible effect for the extraction of information on the nuclear EoS. These contrasting results call for a dedicated theoretical effort to solve this overarching problem that impacts not only the neutron skin thickness or the difference in mass and charge radii of mirror nuclei but also other observables such as the Isobaric Analog State energy.
Comments:
Submitted for publication
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2202.05035 [pdf]
PRC(2022)·26 citations
06
[Submitted on 10 Feb 2022]
Quark deconfinement in compact stars through sexaquark condensation
D. Blaschke🇵🇱 · O. Ivanytskyi🇵🇱 · M. Shahrbaf🇵🇱
In this contribution, we present for the first time a scenario according to which early quark deconfinement in compact stars is triggered by the Bose-Einstein condensation (BEC) of a light sexaquark (S) with a mass $m_{S} < 2054$ MeV, that has been suggested as a candidate particle to explain the baryonic dark matter in the Universe. The onset of S BEC marks the maximum mass of hadronic neutron stars and it occurs when the condition for the baryon chemical potential $μ_{b} = m_{S} /2$ is fulfilled in the center of the star, corresponding to $M_{onset} ≲ 0.7 M_{⊙}$ . In the gravitational field of the star the density of the BEC of the S increases until a new state of the matter is attained, where each of the S-states got dissociated into a triplet of color-flavor-locked (CFL) diquark states. These diquarks are the Cooper pairs in the color superconducting CFL phase of quark matter, so that the developed scenario corresponds to a BEC-BCS transition in strongly interacting matter. For the description of the CFL phase, we develop here for the first time the three-flavor extension of the density-functional formulation of a chirally symmetric Lagrangian model of quark matter where confining properties are encoded in a divergence of the scalar self-energy at low densities and temperatures.
Comments:
27 pages, 8 figures, Contribution to the Book "New Phenomena and New States of Matter in the Universe. From Quarks to Cosmos" edited by C. A. Z. Vasconcellos, P. O. Hess and T. Boller
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2202.05061 [pdf]
New Phenomena and New States of Matter in…·10 citations
07
[Submitted on 10 Feb 2022]
Landau parameters and entrainment matrix of cold stellar matter: effect of the symmetry energy and strong magnetic fields
Helena Pais · Oleksii Ivanytskyi · Constança Providência
Nuclear matter properties based on a relativistic approach suitable for the description of multi-component systems are calculated. We use a set of nuclear relativistic mean-field models that satisfy acceptable nuclear matter properties and neutron star observations. The effects of the density dependence of the symmetry energy and of the Landau quantization due to the presence of a strong external magnetic field are discussed. Properties such as the proton fraction, the Landau mass, Landau parameters and entrainment matrix, the adiabatic index and speed of sound are calculated for cold $β$ -equilibrium matter. A large dispersion on the calculated properties is obtained at two to three times saturation density $ρ_{0}$ . The proton Landau mass can be as low as one third of the vacuum nucleon mass at 2-3 $ρ_{0}$ . Similar effects are obtained for the Landau parameters, in particular, the ones involving protons, where the relative dispersion of $F_{pp}^{0}$ and $F_{pp}^{1}$ is as high as 30\% to 50\% at 2-3 $ρ_{0}$ . These parameters are particularly sensitive to the symmetry energy. The effect of the magnetic field on the nuclear properties is small for fields as high as 10 $^{18}$ G except for a small range of densities just above the crust-core transition. Tables with the EoS, and the parameters, are provided in the Supplementary Material section.
Comments:
26 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2202.05231 [pdf]
JCAP(2022)·1 citation
08
[Submitted on 9 Feb 2022] (cross-list from hep-th)
Deconfinement and Error Thresholds in Holography
Ning Bao🇺🇸 · ChunJun Cao🇺🇸 · Guanyu Zhu🇺🇸
We study the error threshold properties of holographic quantum error-correcting codes. We demonstrate that holographic CFTs admit an algebraic threshold, which is related to the confinement-deconfinement phase transition. We then apply geometric intuition from holography and the Hawking-Page phase transition to motivate the CFT result, and comment on potential extensions to other confining theories.
Comments:
6 pages, 3 figures. Updated to match published version
Subjects:
High Energy Physics — Theory (hep-th); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2202.04710 [pdf]
PRD(2022)·11 citations
09
[Submitted on 10 Feb 2022] (cross-list from nucl-ex)
Coherent photoproduction of the neutral pion and eta meson on the deuteron at incident energies below 1.15 GeV
T. Ishikawa🇯🇵 · A. Fix🇷🇺 · H. Fujimura🇯🇵 · H. Fukasawa🇯🇵 · R. Hashimoto🇯🇵 · Q. He🇯🇵 · Y. Honda🇯🇵 · T. Iwata🇯🇵 · S. Kaida🇯🇵 · J. Kasagi🇯🇵 · A. Kawano · S. Kuwasaki🇯🇵 and 26 other authors
Coherent photoproduction of the neutral pion and eta meson on the deuteron, $γ d$ { $\to$ } $π^{0} η d$ , has been experimentally studied at incident photon energies ranging from the reaction threshold to 1.15 GeV. The total cross section demonstrates a rapid rise below 1 GeV. The data are underestimated by the existing theoretical calculations based on quasi-free $π^{0} η$ photoproduction on the nucleon followed by deuteron coalescence. At the same time, the data are rather well reproduced by the calculations taking into account the final-state interaction. We have also measured for the first time the differential cross sections: the $π^{0} η$ invariant-mass distribution $d σ / d M_{π η}$ , the $π^{0} d$ invariant-mass distribution $d σ / d M_{π d}$ , the $η d$ invariant-mass distribution $d σ / d M_{η d}$ , and the distribution over the deuteron emission angle $d σ / d Ω_{d}$ in the overall center-of-mass frame. The measured cross section $d σ / d Ω_{d}$ does not exhibit strongly backward-peaking behavior predicted by the calculations. At all incident energies, an increase in $d σ / d M_{η d}$ near the $η d$ threshold is observed, which indicates a bound or virtual $η d$ state resulting from a strong attraction between $η$ and a deuteron. The possibilities of using coherent $π^{0} η$ photoproduction on a nucleus to study the $η$ -nuclear interaction are also discussed.
Comments:
15 pages, 9 figures
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2202.04776 [pdf]
PRC(2022)·12 citations
10
[Submitted on 10 Feb 2022] (cross-list from hep-ph)
$Λ_{b} \to p$ transition form factors in perturbative QCD
Jia-Jie Han🇨🇳 · Ya Li🇨🇳 · Hsiang-nan Li🇹🇼 · Yue-Long Shen🇨🇳 · Zhen-Jun Xiao🇨🇳 · Fu-Sheng Yu🇨🇳
We reanalyze the $Λ_{b} \to p$ transition form factors in the perturbative QCD (PQCD) approach by including higher-twist light-cone distribution amplitudes (LCDAs) of a $Λ_{b}$ baryon and a proton. The previous PQCD evaluation performed decades ago with only the leading-twist $Λ_{b}$ baryon and proton LCDAs gave the form factors, which are two orders of magnitude smaller than indicated by experimental data. We find that the twist-4 $Λ_{b}$ baryon LCDAs and the twist-4 and -5 proton LCDAs contribute dominantly, and the enhanced form factors become consistent with those from lattice QCD and other nonperturbative methods. The estimated branching ratios of the semileptonic decays $Λ_{b} \to p ℓ ν ˉ_{ℓ}$ and the hadronic decay $Λ_{b} \to p π$ are also close to the data. It implies that the $b$ quark mass is not really heavy enough, and higher-power contributions play a crucial role, similar to the observation made in analyses of $B$ meson transition form factors. With the formalism established in this work, we are ready to study various exclusive heavy baryon decays systematically in the PQCD approach.
Comments:
37 pages, 7 figures, version to be published in Eur.Phys.J.C
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2202.04804 [pdf]
EPJC(2022)·38 citations
11
[Submitted on 10 Feb 2022] (cross-list from hep-ph)
New-physics signatures via $C P$ violation in $η^{(')} \to π^{0} μ^{+} μ^{-}$ and $η^{'} \to η μ^{+} μ^{-}$ decays
Rafel Escribano🇪🇸 · Emilio Royo🇪🇸 · Pablo Sanchez-Puertas🇪🇸
In this work we investigate the prospect of observing new-physics signatures via $C P$ violation in $η^{(')} \to π^{0} μ^{+} μ^{-}$ and $η^{'} \to η μ^{+} μ^{-}$ decays at the REDTOP experiment. We make use of the SMEFT to parametrise the new-physics $C P$ -violating effects and find that the projected REDTOP statistics are not competitive with respect to nEDM experiments. This reasserts the $η \to μ^{+} μ^{-}$ process as the most promising channel to find $C P$ -violation at this experimental facility.
Comments:
12 pages, 1 figure, 1 table; v2 includes a comment about the neutron EDM constraint and possible accidental Wilson coefficient cancellations
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2202.04886 [pdf]
JHEP(2022)·14 citations
12
[Submitted on 10 Feb 2022] (cross-list from quant-ph)
Random-Matrix Approach to Transition-State Theory
H. A. Weidenmüller🇩🇪
To model a complex system intrinsically separated by a barrier, we use two random Hamiltonians, coupled to each other either by a tunneling matrix element or by an intermediate transition state. We study that model in the universal limit of large matrix dimension. We calculate the average probability for transition from scattering channel coupled to the first Hamiltonian to a scattering channel coupled to the second Hamiltonian. Using only the assumption that the sum of transmission coefficients of channels coupled to the second Hamiltonian is large we retrieve transition-state theory in its general form. For tunneling through a very thick barrier independence of formation and decay of the tunneling process hold more generally.
Comments:
6 pages no figures
Subjects:
Quantum Physics (quant-ph); Nuclear Theory (nucl-th)
arXiv:
2202.04914 [pdf]
PRE(2022)·6 citations
13
[Submitted on 10 Feb 2022] (cross-list from hep-ph)
QCD axial anomaly enhances the $η η^{'}$ decay of the hybrid candidate $η_{1} (1855)$
Hua-Xing Chen🇨🇳 · Niu Su🇨🇳 · Shi-Lin Zhu🇨🇳
We study the hybrid mesons with the exotic quantum number $I^{G} J^{P C} = 0^{+} 1^{-+}$ and investigate their decays into the $η η^{'}$ , $a_{1} (1260) π$ , $f_{1} (1285) η$ , $f_{1} (1420) η$ , $K^{*} (892) K ˉ$ , $K_{1} (1270) K ˉ$ , and $K_{1} (1400) K ˉ$ channels. We find that the QCD axial anomaly enhances the decay width of the $η η^{'}$ channel although this mode is strongly suppressed by the small $P$ -wave phase space. Our results support the interpretation of the $η_{1} (1855)$ recently observed by BESIII as the $s ˉ s g$ hybrid meson of $I^{G} J^{P C} = 0^{+} 1^{-+}$ . The QCD axial anomaly ensures the $η η^{'}$ decay mode to be a characteristic signal of the hybrid nature of the $η_{1} (1855)$ .
Comments:
8 pages, 2 figures, 1 table, references added, to be published in Chin. Phys. Lett
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2202.04918 [pdf]
Chin.Phys.Lett.(2022)·55 citations
14
[Submitted on 10 Feb 2022] (cross-list from nucl-ex)
Light Baryon Spectroscopy
Annika Thiel🇩🇪 · Farah Afzal🇩🇪 · Yannick Wunderlich🇩🇪
This review treats the advances in Light Baryon Spectroscopy of the last two decades, which were mainly obtained by measuring meson-production reactions at photon facilities all over the world. We provide a consistent compendium of experimental results, as well as a review of the theoretical methods of amplitude analysis used to analyze the data. The most significant datasets are presented in detail and are listed in combination with a full set of the relevant references. In addition, a brief summary of spin-formalisms, which are ubiquitous in Light Baryon Spectroscopy, as well as a review on complete experiments, are provided. The synthesis of the reviewed knowledge is presented in a full interpretation of the new results on the Light Baryon Spectrum.
Comments:
142 pages, 52 figures, 19 tables; Version 1 has been accepted for publication in "Progress in Particle and Nuclear Physics"; Version 2 contains further detail improvements
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2202.05055 [pdf]
PPNP(2022)·84 citations
15
[Submitted on 10 Feb 2022] (cross-list from nucl-ex)
Beta decay of halo nuclei
Karsten Riisager
Beta decay is a well-established and efficient probe of nuclear structure and provides important information also for halo nuclei. Detailed decay studies of near-dripline nuclei are challenging, but are now feasible due to the technical progress during the last decades in isotope production as well as detection capabilities. The halo structure can change the dynamics of the decay process, most noticably when decays proceed directly to continuum states as seems to be the case in beta-delayed deuteron emission, a process only observed until now for the halo nuclei $^{6}$ He and $^{11}$ Li. The pronounced clustering in halo states also leaves an imprint on the decay patterns, although the isospin symmetry remains important; in several cases the isobaric analogue states of halo states have also been established. Beta-delayed particle emission channels can be expected to dominate the decays of heavier halo nuclei, if not in terms of branching ratio than certainly in terms of beta strength. A remaining challenge is to find experimental as well as theoretical tools to study the multi-neutron final states that appear for most neutron dripline nuclei.
Comments:
22 pages, 5 figures. Contribution to the "Handbook of Nuclear Physics", Springer, 2022, edited by I. Tanihata, H. Toki and T. Kajino
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2202.05075 [pdf]
1 citation
16
[Submitted on 10 Feb 2022] (cross-list from hep-ph)
Dimensional reduction and the generalized pion in a magnetic field within the NJL model
Jingyi Chao🇨🇳 · Yu-Xin Liu🇨🇳
In this work, the mass of the neutral pion is investigated in the presence of background magnetic fields in the framework of the Nambu--Jona-Lasinio model. Taking into account the anisotropic four-fermion interactions, a tensor current arises in the magnetized QCD system, which forms an anomalous magnetic moment (AMM) coupling in the Dirac equation for the quarks. By solving the gap equations, we find that the sign of the dynamically generated AMM is opposite to the sign of the quark's charge and its magnitude is definitely smaller than the constituent mass. We construct two generalized Nambu-Goldstone pions, which emerge as combinations of the quantum fluctuations around the conventional scalar and the emergent tensor chiral condensates. We analytically demonstrate that the Goldstone nature has been spoiled by the dimensional reduction in the two-particle state and the corresponding decreasing mass of the lighter generalized pionic mode is a remnant of the infrared dynamics.
Comments:
12 pages, 1 figure, journal accepted version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2202.05090 [pdf]
PRD(2023)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE