Nuclear Theory·nucl-th

Wednesday·September 5, 2018

23 papers—13 primary·10 cross-listed

01
Stability of the neutron-proton-electron matter under strong magnetic fields: the covariant Vlasov approach
Sidney Avancini · B. P. Bertolino · Aziz Rabhi · Jianjun Fang · Helena Pais · Constança Providência
The neutron-proton-electron(npe) matter under a strong magnetic field is studied in the context of the covariant Vlasov approach. We use a Walecka-type hadronic model and the dispersion relations for the longitudinal and transverse modes are obtained. The instability regions for longitudinal and transverse modes are also studied. The crust-core transition of a magnetized neutron star is discussed.
nucl-thastro-ph.HEPRC(2018)·9 citations
02
Bubble Structure in Magic Nuclei
G. Saxena🇮🇳 · M. Kumawat🇮🇳 · M. Kaushik · S. K. Jain🇮🇳 · Mamta Aggarwal🇮🇳
The existence of bubble nuclei identified by the central depletion in nucleonic density is studied for the conventional magic N (Z) $=$ 8, 20, 28, 40, 50, 82, 126 isotones (isotopes) and recently speculated magic N $=$ 164, 184, 228 superheavy isotones. Many new bubble nuclei are predicted in all regions. Study of density profiles, form factor, single particle levels and depletion fraction (DF) across the periodic chart reveals that the central depletion is correlated to shell structure and occurs due to unoccupancy in s-orbit (2s, 3s, 4s) and inversion of (2s, 1d) and (3s, 1h) states in nuclei upto Z $\leq$ 82. Bubble effect in superheavy region is a signature of the interplay between the Coulomb and nn-interaction and depletion fraction (DF) is found to increase with Z (Coulomb repulsion) and decrease with isospin. Our results are consistent with the available data. The occupancy in s-state in $^{34}$ Si increases with temperature which appears to quench the bubble effect.
nucl-thnucl-exPLB(2019)·46 citations
03
Unitary limit and linear scaling of neutrons in harmonic trap with tuned CD-Bonn and square-well interactions
Yi-Yuan Cheng🇨🇳 · Thomas T. S. Kuo🇺🇸 · Ruprecht Machleidt🇺🇸 · Yu-Min Zhao🇨🇳
We study systems of finite-number neutrons in a harmonic trap at the unitary limit. Two very different types of neutron-neutron interactions are applied, namely, the meson-theoretic CD-Bonn potential and hard-core square-well interactions, all tuned to possess infinite scattering lengths, and with effective ranges comparable to or larger than the trap size. The potentials are renormalized to equivalent, scattering-length preserving low-momentum potentials, $V_{low - k}$ , with which the particle-particle hole-hole ring diagrams are summed to all orders to yield the ground-state energy $E_{0}$ of the finite neutron system. We find the ratio $E_{0} / E_{0}^{free}$ (where $E_{0}^{free}$ denotes the ground-state energy of the corresponding non-interacting system) to be remarkably independent from variations of the harmonic trap parameter, the number of neutrons, the decimation momentum of $V_{low - k}$ , and the type and effective range of the unitarity potential. Our results support a special virial linear scaling relation of $E_{0}$ . Certain properties of Landau's quasi-particles for trapped neutrons at the unitary limit are also discussed.
nucl-thPLB(2019)·4 citations
04
Effective operators in two-nucleon systems
James P. Vary🇺🇸 · Robert Basili🇺🇸 · Weijie Du🇺🇸 · Matthew Lockner🇺🇸 · Pieter Maris🇺🇸 · Soham Pal🇺🇸 · Shiplu Sarker🇺🇸
Effective Hamiltonians and effective electroweak operators are calculated with the Okubo-Lee-Suzuki formalism for two-nucleon systems. Working within a harmonic oscillator basis, first without and then with a confining harmonic oscillator trap, we demonstrate the effects of renormalization on observables calculated for truncated basis spaces. We illustrate the renormalization effects for the root-mean-square point-proton radius, electric quadrupole moment, magnetic dipole moment, Gamow-Teller transition and neutrinoless double-beta decay operator using nucleon-nucleon interactions from chiral Effective Field Theory. Renormalization effects tend to be larger in the weaker traps and smaller basis spaces suggesting applications to heavier nuclei with transitions dominated by weakly-bound nucleons would be subject to more significant renormalization effects within achievable basis spaces.
nucl-thPRC(2018)·11 citations
05
Complete experiments in pseudoscalar meson photoproduction revisited
K. Nakayama🇺🇸
By exploiting the underlying symmetries of the relative phases of the pseudoscalar meson photoproduction amplitude, we determine all the possible sets of four double-spin observables that resolve the phase ambiguity of the amplitude in transversity basis up to an overall phase. The present results corroborate the original findings by Chiang and Tabakin [Phys. Rev. C 55, 2054 (1997)]. However, it is found that the completeness condition of four double-spin observables to resolve the phase ambiguity holds only when the relative phases do not meet the condition of equal magnitudes. In situations where this condition occurs, it is shown that one needs extra chosen observables, resulting in the minimum number of observables required to resolve the phase ambiguity to reach up to eight, depending on the particular set of four double-spin observables considered. Furthermore, a way of gauging when the condition of equal magnitudes occurs is provided.
nucl-thhep-phPRC(2019)·12 citations
06
Stability of alpha-chain States against Break-up and Binary Disintegrations
Akihiro Tohsaki🇯🇵 · Naoyuki Itagaki🇯🇵
We focus upon the raison d'etre of the alpha-chain states on the basis of the fully microscopic framework, where the Pauli principle among all the nucleons is fully taken into account. Our purpose is to find out the limiting number of alpha clusters, on which the linear alpha-cluster state can stably exist. How many alpha-clusters can stably make an alpha-chain state? We examine the properties of equally separated alpha clusters on a straight line and compare its stability with that on a circle. We also confirm its stability in terms of break-up and binary disintegrations including alpha-decay and fission modes. For the effective nucleon-nucleon interaction, we employ the F1 force, which has finite-range three-body terms and guarantees overall saturation properties of nuclei. This interaction also gives reasonable binding energy and size of the alpha particle and the alpha-alpha scattering phase shift. The result astonishes us because we can point out a possible existence of alpha-chain states with vast numbers of alpha clusters.
nucl-thPTEP(2019)·3 citations
07
The Self-energy of Nucleon for the Anomalous Magnetic Moment
Susumu Kinpara🇯🇵
The anomalous part of the magnetic moment of nucleon is studied. The electromagnetic vertex of nucleon is calculated using the pseudovector coupling pion-nucleon interaction. The self-energy of nucleon suggested in the previous study is applied to the internal line.
nucl-th2 citations
08
Effect of Confinement of Gluons and One Pion Exchange in Nucleon-Nucleon Interaction
V K Nilakanthan🇮🇳 · V C Shastry🇮🇳 · S Raghavendra🇮🇳 · K B Vijaya Kumar🇮🇳
The Nucleon-Nucleon interaction in the singlet ( $^{1} S_{0}$ ) and triplet ( $^{3} S_{1}$ ) channels have been studied in the framework of Relativistic Harmonic Model using the Resonating Group Method in Born-Oppenheimer approximation. The full Hamiltonian consists of the kinetic energy, two body confinement potential, confined one gluon exchange potential and one pion exchange potential. Contribution of Confined One Gluon Exchange Potential and One Pion Exchange Potential to the adiabatic nucleon-nucleon interaction potential is discussed.
nucl-thhep-phEur.Phys.J.Plus(2019)·3 citations
09
Effective Field Theory in The Study of Long Range Nuclear Parity Violation on Lattice
Feng-Kun Guo🇨🇳 · Chien-Yeah Seng🇨🇳
A non-zero signal $A_{γ}^{np} = (- 3.0 \pm 1.4 \pm 0.2) \times 1 0^{- 8}$ of the gamma-ray asymmetry in the neutron-proton capture was recently reported by the NPDGamma Collaboration which provides the first determination of the $Δ I = 1$ parity-odd pion-nucleon coupling constant $h_{π}^{1} = (2.6 \pm 1.2 \pm 0.2) \times 1 0^{- 7}$ . The ability to reproduce this value from first principles serves as a direct test of our current understanding of the interplay between the strong and weak interaction at low energy. To motivate new lattice studies of $h_{π}^{1}$ , we review the current status of the theoretical understanding of this coupling, which includes our recent work that relates it to a nucleon mass-splitting by a soft-pion theorem. We further investigate the possibility of calculating the mass-splitting on the lattice by providing effective field theory parameterizations of all the involved quark contraction diagrams. We show that the lattice calculations of the easier connected diagrams will provide information of the chiral logarithms in the much harder quark loop diagrams and thus help in the chiral extrapolation of the latter.
nucl-thhep-lathep-phnucl-exEPJC(2019)·12 citations
10
Isolating dynamical net-charge fluctuations
Rudolph Rogly🇫🇷 · Giuliano Giacalone🇫🇷 · Jean-Yves Ollitrault🇫🇷
We modify the usual definitions of cumulants of net-charge fluctuations in a way that isolates dynamical fluctuations. The new observables, which we call dynamical cumulants, are robust with respect to trivial correlations induced by volume fluctuations and global charge conservation. We illustrate the potential of dynamical cumulants by carrying out Monte Carlo simulations where all correlations are trivial. The results of our simulations agree well with Relativistic Heavy Ion Collider (RHIC) data, and are used to illustrate that dynamical cumulants consistently isolate dynamical fluctuations.
nucl-thhep-phnucl-exPRC(2019)·9 citations
11
Asymmetry of the neutrino mean free path in hot neutron matter under strong magnetic fields
Julio Torres Patiño🇦🇷 · Eduardo Bauer🇦🇷 · Isaac Vidaña🇮🇹
The neutrino mean free path in neutron matter under a strong magnetic field is evaluated for the inelastic scattering reaction and studied as a function of the neutron matter density in the range $0.05 \leq ρ \leq 0.4$ fm $^{- 3}$ for several temperatures up to 30 MeV and magnetic field strengths B=0 G, $1 0^{18}$ G and $2.5 \times 1 0^{18}$ G. Polarized neutron matter is described within the non--relativistic Brueckner--Hartree--Fock (BHF) approach using the Argonne V18 nucleon-nucleon potential supplemented with the Urbana IX three-nucleon force. Explicit expressions of the cross section per unit volume for the scattering of a neutrino with a spin up or spin down neutron are derived from the Fermi Golden rule. Our results show that the mean free path depends strongly on the angle of the incoming neutrino, leading to an asymmetry in this quantity. This asymmetry depends on the magnetic field intensity and on the density, but it is rather independent of the temperature. For a density of $0.16$ fm $^{- 3}$ at a temperature T $= 30$ MeV, the asymmetry in the mean free path is found to be of $\sim 15%$ for B= $1 0^{18}$ G and $\sim 38%$ for B= $2.5 \times 1 0^{18}$ G.
nucl-thPRC(2019)·9 citations
12
Electromagnetic and weak decays of baryons in the unquenched quark model
Roelof Bijker🇲🇽 · Gustavo Guerrero-Navarro🇲🇽 · Emmanuel Ortiz-Pacheco🇲🇽
In this contribution, we discuss the electromagnetic and weak decays of baryons in the unquenched quark model and show that the observed discrepancies between the experimental data and the predictions of the constituent quark model can be accounted for in large part by the effects of sea quarks. Finally, the obtained results are discussed in terms of flavor-symmetry breaking.
nucl-thhep-phJ.Phys.Conf.Ser.(2018)·0 citations
13
Individual low-energy E1 toroidal and compression states in light nuclei: deformation effect, spectroscopy and interpretation
V.O. Nesterenko🇷🇺 · J. Kvasil🇨🇿 · A. Repko🇸🇰 · P.-G. Reinhard🇩🇪
The existence of individual low-energy E1 toroidal and compression states (TS and CS) in $^{24}$ Mg was predicted recently in the framework of quasiparticle random-phase-approximation (QRPA) model with Skyrme forces. It was shown that the strong axial deformation of $^{24}$ Mg is crucial to downshift the toroidal strength to the low-energy region and thus make the TS the lowest E1(K=1) dipole state. In this study, we explain this result by simple mean-field arguments. Comparing TS in two strongly axial nuclei, $^{24}$ Mg and $^{20}$ Ne, we show that the lowest TS is not not a universal phenomenon but rather a peculiarity of $^{24}$ Mg. The spectroscopy of TS and CS is analyzed and some additional interpretation of these states is suggested.
nucl-thEPJ Web Conf.(2018)·4 citations
14
Theoretical perspective for the future experiments on parton densities
S. Kumano (KEK/J-PARC)🇯🇵
I explain the current status of parton-distribution-function (PDF) studies and future experimental prospects on their determinations. First, unpolarized PDFs of the nucleon are introduced as a field of precision QCD physics including higher-order $α_{s}$ corrections. Second, nuclear PDFs and polarized nucleonic PDFs are discussed. Third, the determination of fragmentation functions is explained. Forth, the three-dimensional (3D) structure functions are discussed in connection with the origin of the nucleon spin and gravitational form factors of hadrons. By the 3D structure functions, gravitational sources and the origin of nucleon mass could be clarified in the microscopic level of quarks and gluons. Furthermore, 3D structure studies of hadrons could be used for clarifying internal structure of exotic hadron candidates, nuclear composition of ultra-high-energy cosmic rays, and color-entanglement phenomena. The PDF field will be developed further along with progress in other fields of science.
↳ hep-phhep-exhep-latnucl-ex+1PoS(2018)·3 citations
15
Meson correlation functions at high temperature QCD: $S U (2)_{C S}$ symmetry vs. free quarks
C. Rohrhofer🇦🇹 · Y. Aoki🇯🇵 · G. Cossu🇬🇧 · L. Ya. Glozman🇦🇹 · S. Hashimoto🇯🇵 · S. Prelovsek🇸🇮
We report on the progress of understanding spatial correlation functions in high temperature QCD. We study isovector meson operators in $N_{f} = 2$ QCD using domain-wall fermions on lattices of $N_{s} = 32$ and different quark masses. It has previously been found that at $\sim 2 T_{c}$ these observables are not only chirally symmetric but in addition approximately $S U (2)_{C S}$ and $S U (4)$ symmetric. In this study we increase the temperature up to $5 T_{c}$ and can identify convergence towards an asymptotically free scenario at very high temperatures.
↳ hep-lathep-phhep-thnucl-thPoS(2018)·5 citations
16
Neutron-antineutron oscillations from lattice QCD
Enrico Rinaldi🇺🇸 · Sergey Syritsyn🇺🇸 · Michael L. Wagman🇺🇸 · Michael I. Buchoff🇺🇸 · Chris Schroeder🇺🇸 · Joseph Wasem🇺🇸
Fundamental symmetry tests of baryon number violation in low-energy experiments can probe beyond the Standard Model (BSM) explanations of the matter-antimatter asymmetry of the universe. Neutron-antineutron oscillations are predicted to be a signature of many baryogenesis mechanisms involving low-scale baryon number violation. This work presents first-principles calculations of neutron-antineutron matrix elements needed to accurately connect measurements of the neutron-antineutron oscillation rate to constraints on $∣Δ B ∣ = 2$ baryon number violation in BSM theories. Several important systematic uncertainties are controlled by using a state-of-the-art lattice gauge field ensemble with physical quark masses and approximate chiral symmetry, performing nonperturbative renormalization with perturbative matching to the $MS$ scheme, and studying excited state effects in two-state fits. Phenomenological implications are highlighted by comparing expected bounds from proposed neutron-antineutron oscillation experiments to predictions of a specific model of post-sphaleron baryogenesis. Quantum chromodynamics is found to predict at least an order of magnitude more events in neutron-antineutron oscillation experiments than previous estimates based on the "MIT bag model" for fixed BSM parameters. Lattice artifacts and other systematic uncertainties that are not controlled in this pioneering calculation are not expected to significantly change this conclusion.
↳ hep-lathep-phnucl-thPRL(2019)·45 citations
17
Relating hadronic CP-violation to higher-twist distributions
Chien-Yeah Seng🇨🇳
The nucleon sigma term of the isoscalar and isovector quark chromo-magnetic dipole moments are essential inputs for the determination of the CP-odd pion-nucleon couplings induced by quark chromo-electric dipole moments. We demonstrate that the former can be mapped to the third moment of the nucleon twist-three chiral-odd distribution functions $e^{q} (x)$ which are in principle measurable in semi-inclusive deep inelastic scattering processes. We perform a survey on existing model calculations as well as experimental data on $e^{u} (x) + e^{d} (x)$ and derive a predicted range for the isoscalar chromo-magnetic dipole moment sigma term.
↳ hep-phhep-exnucl-thPRL(2019)·19 citations
18
$η^{'}$ and $η$ mesons at high T when the U_A(1) and chiral symmetry breaking are tied
Davor Horvatić🇭🇷 · Dalibor Kekez🇭🇷 · Dubravko Klabučar🇭🇷
The approach to the eta'-eta complex employing chirally well-behaved quark-antiquark bound states and incorporating the non-Abelian axial anomaly of QCD through the generalization of the Witten-Veneziano relation, is extended to finite temperatures. Employing the chiral condensate has led to a sharp chiral and U_A(1) symmetry restoration, but with the condensates of quarks with realistic explicit chiral symmetry breaking, which exhibit a smooth, crossover chiral symmetry restoration in qualitative agreement with lattice QCD results, we get a crossover U_A(1) transition, with smooth and gradual melting of anomalous mass contributions. This way we obtain a substantial drop of the eta' mass around the chiral transition temperature, but no eta mass drop. This is consistent with the present empirical evidence.
↳ hep-phnucl-thPRD(2019)·20 citations
19
FRIB and the GW170817 Kilonova
A. Aprahamian🇺🇸 · R. Surman🇺🇸 · A. Frebel🇺🇸 · G.C. McLaughlin🇺🇸 · A. Arcones🇩🇪 · A.B. Balantekin🇺🇸 · J. Barnes🇺🇸 · Timothy C. Beers🇺🇸 · Erika M. Holmbeck🇺🇸 · Jinmi Yoon🇺🇸 · Maxime Brodeur🇺🇸 · T.M. Sprouse🇺🇸 and 36 other authors
In July 2018 an FRIB Theory Alliance program was held on the implications of GW170817 and its associated kilonova for r-process nucleosynthesis. Topics of discussion included the astrophysical and nuclear physics uncertainties in the interpretation of the GW170817 kilonova, what we can learn about the astrophysical site or sites of the r process from this event, and the advances in nuclear experiment and theory most crucial to pursue in light of the new data. Here we compile a selection of scientific contributions to the workshop, broadly representative of progress in r-process studies since the GW170817 event.
↳ astro-ph.HEastro-ph.SRnucl-th13 citations
20
Women Scientists Who Made Nuclear Astrophysics
C. V. Hampton🇺🇸 · M. Lugaro🇭🇺 · P. Papakonstantinou🇰🇷 · P. G. Isar🇷🇴 · B. Nordström🇩🇰 · N. Özkan🇹🇷 · M. Aliotta🇬🇧 · A. Ćiprijanović🇷🇸 · S. Curtis🇺🇸 · M. Di Criscienzo🇮🇹 · J. den Hartogh🇭🇺 · A. S. Font🇬🇧 and 15 other authors
Female role models reduce the impact on women of stereotype threat, i.e., of being at risk of conforming to a negative stereotype about one's social, gender, or racial group. This can lead women scientists to underperform or to leave their scientific career because of negative stereotypes such as, not being as talented or as interested in science as men. Sadly, history rarely provides role models for women scientists; instead, it often renders these women invisible. In response to this situation, we present a selection of twelve outstanding women who helped to develop nuclear astrophysics.
↳ physics.hist-phastro-ph.EPastro-ph.GAastro-ph.HE+3Springer Proc.Phys.(2019)·0 citations
21
Bound state formation in the $D D K$ system
A. Martinez Torres🇧🇷 · K. P. Khemchandani🇨🇳 · Li-Sheng Geng🇨🇳
We study the $D D K$ system in a coupled channel approach, by including $D D_{s} η$ and $D D_{s} π$ , and find that the dynamics involved in the system forms a bound state with isospin $1/2$ and mass $4140$ MeV when one of the $D K$ pair is resonating in isospin 0, forming the $D_{s 0}^{*} (2317)$ . The state can be interpreted as a $D D_{s 0}^{*} (2317)$ molecule like state with exotic quantum numbers: doubly charged, doubly charmed, and with single strangeness.
↳ hep-phnucl-thPRD(2019)·42 citations
22
Effects of neutrino mixing upon electron fraction in core collapse supernovae
M.M. Saez🇦🇷 · M.E. Mosquera🇦🇷 · O. Civitarese🇦🇷
The inclusion of massive neutrinos affects the cross sections involved in the formation of heavy nuclei, modifying their abundances. Rapid neutron capture processes (r-process) are often associated with explosive events such as core-collapse supernovae. In this work we study the effects of active and sterile neutrino oscillations and interactions, upon the calculation of neutrino fluxes, the baryonic density and the electron fraction of the material. We have considered two different initial distribution functions of the neutrinos and different combinations of mixing parameters (including {\theta} 34 = 0). We use the formalism of density matrices for the calculations and included the effects of neutrino oscillations, interactions with matter and self-neutrino interactions. We found that the interactions of the neutrinos with matter and with themselves change the electron fraction, affecting the onset of the r-process.
↳ hep-phastro-ph.SRnucl-thphysics.space-phBol.A.A.Astron.(2018)·0 citations
23
Identifying a first-order phase transition in neutron star mergers through gravitational waves
Andreas Bauswein🇩🇪 · Niels-Uwe F. Bastian🇵🇱 · David B. Blaschke🇵🇱 · Katerina Chatziioannou🇨🇦 · James A. Clark · Tobias Fischer🇵🇱 · Micaela Oertel🇫🇷
We identify an observable imprint of a first-order hadron-quark phase transition at supranuclear densities on the gravitational-wave (GW) emission of neutron star mergers. Specifically, we show that the dominant postmerger GW frequency f_peak may exhibit a significant deviation from an empirical relation between f_peak and the tidal deformability if a strong first-order phase transition leads to the formation of a gravitationally stable extended quark matter core in the postmerger remnant. A comparison of the GW signatures from a large, representative sample of microphysical, purely hadronic equations of state indicates that this imprint is only observed in those systems which undergo a strong first-order phase transition. Such a shift of the dominant postmerger GW frequency can be revealed by future GW observations, which would provide evidence for the existence of a strong first-order phase transition in the interior of neutron stars.
↳ astro-ph.HEhep-phnucl-thPRL(2019)·471 citations

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