Nuclear Theory·nucl-th

Wednesday·December 27, 2017

20 papers—14 primary·6 cross-listed

01
Is it possible to study neutrinoless $β β$ decay by measuring double Gamow-Teller transitions?
Javier Menéndez🇯🇵 · Noritaka Shimizu🇯🇵 · Kentaro Yako🇯🇵
Searches of neutrinoless double-beta decay require information on the value of the nuclear matrix elements that rule the process to plan and interpret experiments. At present, however, even the matrix elements obtained with the most reliable many-body approaches do not agree to each other better than a factor two or three. A usual test of the many-body calculations is the comparison to several nuclear observables, but so far no nuclear structure property has been found to show a good correlation to neutrinoless double-beta decay. Here we propose that double charge-exchange experiments can offer a very valuable tool to provide insights on neutrinoless double-beta decay. Double charge-exchange reactions are being currently performed in various laboratories worldwide and aim to find the novel nuclear collectivity given by double Gamow-Teller excitations. Our results suggest a good linear correlation between double Gamow-Teller transitions to the ground state of the final nucleus and neutrinoless double-beta decay nuclear matrix elements. The correlation seems robust across $p f$ -shell nuclei.
nucl-thhep-exhep-phnucl-exJ.Phys.Conf.Ser.(2018)·8 citations
02
Neutron Transfer Reactions for Deformed Nuclei Using Sturmian Basis States
V.G. Gueorguiev · J.E. Escher
We study the spin-parity distribution P(J $^{π}$ ,E) of $^{156}$ Gd excited states above the neutron separation energy $S_{n} = 8.536$ MeV \cite{156Gd_list_of_levels} that are expected to be populated via the 1-step neutron pickup reaction $^{157}$ Gd( $^{3}$ He, $^{4}$ He) $^{156}$ Gd. In analogy with the rotor plus particle model \cite{Bohr&Mottelson-II}, we view excited states in $^{156}$ Gd as rotational excitations built on intrinsic states consisting of a neutron hole in the $^{157}$ Gd core, that is, a neutron removal from a deformed Woods-Saxon type single-particle state \cite{Woods-Saxon:1954} in $^{157}$ Gd. The particle-core interaction usually dominated by a Coriolis coupling are accounted via first order perturbation theory \cite{VGGueorguiev:07062002}. The reaction cross section to each excited state in $^{156}$ Gd is calculated as coherent contribution using a standard reaction code \cite{CHUCK} based on spherical basis states. The spectroscopic factor associated with each state is the expansion coefficient of the deformed neutron state in a spherical Sturmian basis along with the spherical form factors \cite{VGGueorguiev:07062002}. The total cross section, as a function of the excitation energy, is generated using Lorentzian smearing distribution function. Our calculations show that, within the assumptions and computational modeling, the reaction $^{3}$ He+ $^{157}$ Gd $\to$ $^{4}$ He+ $^{156}$ Gd $^{⋆}$ has a smooth formation probability P(J $^{π}$ ,E) within the energy range relevant to the desired reaction $^{155}$ Gd+n $\to$ $^{156}$ Gd $^{⋆}$ . The formation probability P(J $^{π}$ ,E) resembles a Gaussian distribution with centroids and widths that differ for positive and negative parity states.
nucl-thBulg.J.Phys.(2017)·1 citation
03
On the moment of inertia of PSR J0348+0432
Xian-Feng Zhao
The moment of inertia of the massive neutron star PSR J0348+0432 is studied in the framework of the relativistic mean field theory by choosing suitable hyperon coupling constants. By this method, we find that the suggested radius of the massive neutron star PSR J0348+0432 is in the range $R = 12.957 \sim 12.246$ km by the observation $M$ =1.97 $\sim$ 2.05 M $_{⊙}$ . We also find that the suggested moment of inertia $I$ of the massive neutron star PSR J0348+0432 is in the range $I$ =1.9073 $\times$ 10 $^{45} \sim$ 1.5940 $\times 1 0^{45}$ g.cm $^{2}$ by the observation $M$ =1.97 $\sim$ 2.05 M $_{⊙}$ . Massive pulsars hint that the interaction inside them should be very "strong". Though hyperons considered will reduce the maximum mass, but in principle we may have models predicting maximum masses higher than 2 M $_{⊙}$ by choosing suitable parameters, in a degree of freedom of hadron. Our calculations have proved the above and perfectly agree with the results both of Aaron W et al and Pétri J et al.
nucl-thChin.J.Phys.(2016)·12 citations
04
The hyperons in the massive neutron star PSR J0348+0432
Xian-Feng Zhao🇨🇳
Whether the massive neutron star PSR J0348+0432 can become a hyperon star is examined in the framework of the relativistic mean field theory by adjusting the hyperon coupling constants. It is found that at the central baryon number density of the massive neutron star PSR J0348+0432, the relative particle number density of hyperons is smaller than those of neutrons and so it can not change into a hyperon star. In its center, it is mainly composed of $Λ$ , $Ξ^{-}$ and a few $Ξ^{0}$ . We also found that for the neutron star with a maximum mass of 1.4 M $_{⊙}$ , it can change into a hyperon star and the hyperon star transition density is 0.668 fm $^{- 3}$ , at which the hyperons are only composed of $Λ$ . At its center, the hyperons are also only composed of $Λ$ and the ratio of the hyperons is a little larger than that of the neutrons. This illustrates that the NS1.4M $_{⊙}$ has just changed into a hyperon star.
nucl-thChin.J.Phys.(2015)·3 citations
05
Examination of the influence of the f $_{0}$ (975) and $ϕ$ (1020) mesons on the surface gravitional redshift of the neutron star PSR J0348+0432
Xian-Feng Zhao🇨🇳
The effect of the mesons $f_{0} (975)$ and $ϕ (1020)$ on the surface gravitional redshift of the neutron star PSR J0348+0432 is examined in the framework of the relativistic mean field theory by choosing the suitable hyperon coupling constants. We find that compared with that without considering the mesons $f_{0} (975)$ and $ϕ (1020)$ , the value range of the radius $R$ of the neutron star PSR J0348+0432 would be changed from a narrow range 12.964 km $\sim$ 12.364 km to a wider range 12.941 km $\sim$ 11.907 km corresponding to the observation mass M=1.97 M $_{⊙}$ $\sim$ 2.05 M $_{⊙}$ . We also find that the value range of the surface gravitational redshift $z$ of the neutron star PSR J0348+0432 changes from 0.3469 $\sim$ 0.3997 to 0.3480 $\sim$ 0.4263 corresponding to the observation mass M=1.97 M $_{⊙}$ $\sim$ 2.05 M $_{⊙}$ as the mesons $f_{0} (975)$ and $ϕ (1020)$ being considered. These mean the radius $R$ and the surface gravitational redshift $z$ all will be constrained in a wider scope as the mesons $f_{0} (975)$ and $ϕ (1020)$ being considered. We also can see that the difference of the radius and the surface gravitational redshift is not so large whether the mesons $f_{0} (975)$ and $ϕ (1020)$ being considered or not. This indicates that the mesons $f_{0} (975)$ and $ϕ (1020)$ do not play a major role in the massive neutron star PSR J0348+0432.
nucl-thPRC(2015)·12 citations
06
The properties of the neutron star PSR J0348+0432
Xian-Feng Zhao🇨🇳
The properties of the massive neutron star PSR J0348+0432 is calculated in the framework of the relativistic mean field theory by choosing the suitable hyperon coupling constants. It is found that the central energy density $ϵ_{c}$ and the central pressure $p_{c}$ of the massive neutron star PSR J0348+0432 respectively are 1.5 times larger and 3.6 times larger than those of the canonical mass neutron star. It is also found that in the neutron star PSR J0348+0432 there are five kinds of baryons appearing: n, p, $Λ$ , $Ξ^{-}$ and $Ξ^{0}$ but in the canonical mass neutron star there are only three kinds of particles appearing: n, p and $Λ$ . In our models, the positive well depth $U_{Σ}^{(N)}$ will restrict the production of the hyperons $Σ^{-}$ , $Σ^{0}$ and $Σ^{+}$ and therefore either in the neutron star PSR J0348+0432 or in the canonical mass neutron star the hyperons $Σ^{-}$ , $Σ^{0}$ and $Σ^{+}$ all do not appear. In addition, our results also show that the radius $R$ of the massive neutron star PSR J0348+0432 is less than that of the canonical mass neutron star while the gravitational redshift of the former is larger than that of the latter.
nucl-thInt.J.Mod.Phys.D(2015)·26 citations
07
Can the massive neutron star PSR J0348+0432 be a hyperon star?
Xian-Feng Zhao🇨🇳
Whether the massive neutron star PSR J0348+0432 can change into a hyperon star is studied in the framework of the relative mean field theory by choosing the suitable hyperon coupling constants. We find that whether the mesons $σ^{*}$ and $ϕ$ being considered or not, the neutron star PSR J0348+0432 all can change into a hyperon star and the hyperon star transition density are the same for the two cases. We also find that the canonical mass neutron star also can change into a hyperon star in a minor hyperon star transition density as the mesons $σ^{*}$ and $ϕ$ are not considered. Our results confirms some of recent conclusions.
nucl-thActa Phys.Polon.B(2017)·5 citations
08
Nucleon-to-Delta transition form factors in chiral effective field theory using the complex-mass scheme
M. Hilt🇩🇪 · T. Bauer🇩🇪 · S. Scherer🇩🇪 · L. Tiator🇩🇪
We calculate the form factors of the electromagnetic nucleon-to- $Δ$ -resonance transition to third chiral order in manifestly Lorentz-invariant chiral effective field theory. For the purpose of generating a systematic power counting, the complex-mass scheme is applied in combination with the small-scale expansion. We fit the results to available empirical data.
nucl-thhep-phnucl-exPRC(2018)·19 citations
09
Generalized isobaric multiplet mass equation and its application to the Nolen-Schiffer anomaly
J. M. Dong · Y. H. Zhang · W. Zuo · J. Z. Gu · L. J. Wang · Y. Sun
The Wigner Isobaric Multiplet Mass Equation (IMME) is the most fundamental prediction in nuclear physics with the concept of isospin. However, it was deduced based on the Wigner-Eckart theorem with the assumption that all charge-violating interactions can be written as tensors of rank two. In the present work, the charge-symmetry breaking (CSB) and charge-independent breaking (CIB) components of the nucleon-nucleon force, which contribute to the effective interaction in nuclear medium, are established in the framework of Brueckner theory with AV18 and AV14 bare interactions. Because such charge-violating components can no longer be expressed as an irreducible tensor due to density dependence, its matrix element cannot be analytically reduced by the Wigner-Eckart theorem. With an alternative approach, we derive a generalized IMME (GIMME) that modifies the coefficients of the original IMME. As the first application of GIMME, we study the long-standing question for the origin of the Nolen-Schiffer anomaly found in the Coulomb displacement energy of mirror nuclei. We find that the naturally-emerged CSB term in GIMME is largely responsible for explaining the Nolen-Schiffer anomaly.
nucl-thPRC(2018)·23 citations
10
Investigation of $α$ clustering with knockout reactions
Kazuki Yoshida · Kazuyuki Ogata · Yoshiko Kanada-En'yo
Our goal is to reveal how the $α$ cluster amplitude is probed through $α$ knockout reactions depending on reaction conditions, e.g., the incident energy. We consider $^{20}$ Ne( $p$ , $p α$ ) $^{16}$ O and $^{120}$ Sn( $p$ , $p α$ ) $^{116}$ Cd at 100-400 MeV within the distorted wave impulse approximation (DWIA) framework. We introduce a masking function which shows how the reaction amplitude in the nuclear interior is suppressed and defines the probed region of the $α$ cluster wave function. It is clearly shown by means of the masking function that the $α$ knockout reaction probes the $α$ cluster amplitude in the nuclear surface region, which is the direct measure of well-developed $α$ cluster states. A simplified form of the masking function is introduced and the incident energy dependence of the masking effect is investigated. $α$ knockout reaction can probe the $α$ cluster amplitude in the nuclear surface region by choosing proper kinematics owing to the masking effect originated from absorptions of distorting potentials, and is a suitable method to investigate how $α$ cluster states are spatially developed.
nucl-thPRC(2018)·24 citations
11
Interplay between isoscalar and isovector correlations in neutron-rich nuclei
I. Hamamoto · H. Sagawa
The interplay between isoscalar and isovector correlations in the 1 $^{-}$ states in neutron-rich (N $\neq =$ Z) even-even nuclei is studied, taking examples of the nuclei, $_{8}^{22}$ O $_{14}$ and $_{8}^{24}$ O $_{16}$ . The excitation modes explored are isovector dipole and isoscalar compression dipole modes. The self-consistent Hartree-Fock plus the random-phase approximation with the Skyrme interaction, SLy4, is solved in coordinate space so as to take properly into account the continuum effect. The isovector peak induced by isoscalar correlation, the isoscalar peak induced by isovector correlation, and the possible collective states made by both isoscalar and isovector correlations, ("iS-iV pigmy resonance"), are shown. The strong neutron-proton interaction in nuclei can be responsible for controlling the isospin structure of normal modes. It is explicitly shown that in the scattering by isoscalar (isovector) particles on N $\neq =$ Z even-even nuclei isovector (isoscalar) strength in addition to isoscalar (isovector) strength may be populated.
nucl-thPRC(2017)·3 citations
12
Effects of causality on the fluidity and viscous horizon of quark-gluon plasma
Mahfuzur Rahaman🇮🇳 · Jan-e Alam🇮🇳
The second order Israel-Stewart-M $u ¨$ ller relativistic hydrodynamics has been applied to study the effects of causality on the acoustic oscillation in relativistic fluid. Causal dispersion relations have been derived with non-vanishing shear viscosity, bulk viscosity and thermal conductivity at non-zero temperature and chemical potential. These relations have been used to investigate the fluidity of Quark Gluon Plasma (QGP) at finite temperature ( $T$ ). Results of the first order dissipative hydrodynamics have been obtained as limiting case of the second order theory. The effects of the causality on the fluidity near the transition point and on viscous horizon are found to be significant. We observe that the inclusion of causality reduces the fluidity of QGP. It has also been shown that the inclusion of large magnetic field in the causal hydrodynamics alters the fluidity of QGP
nucl-thPRC(2018)·5 citations
13
Evolution of Charge Fluctuations and Correlations in the Hydrodynamic Stage of Heavy Ion Collisions
Scott Pratt🇺🇸 · Jane Kim🇺🇸 · Chris Plumberg🇺🇸
Charge fluctuations for a baryon-neutral quark-gluon plasma have been calculated in lattice gauge theory. These fluctuations provide a well-posed rigorous representation of the quark chemistry of the vacuum for temperatures above T_c >~ 155 MeV. Due to the finite lifetime and spatial extent of the fireball created in relativistic heavy ion collisions, charge-charge correlations can only equilibrate for small volumes due to the finite time required to transport charge. This constraint leads to charge correlations at finite relative position that evolve with time. The source and evolution of such correlations is determined by the evolution of the charge fluctuation and the diffusion constant for light quarks. Here, calculations are presented for the evolution of such correlations superimposed onto hydrodynamic simulations. Results are similar to preliminary measurements from STAR, but significant discrepancies remain.
nucl-thPRC(2018)·17 citations
14
Pairing dynamics and time dependent density functional theory
P. Magierski · J. Grineviciute · K. Sekizawa
We discuss issues related to pairing dynamics in nuclear large amplitude collective motion. The examples of effects which are not properly described within BCS theory are presented. In the second part we review properties of TDDFT and in particular we discuss the time-dependent local density approximation (TDSLDA) starting from the stationary action principle.
nucl-thActa Phys.Polon.B(2018)·6 citations

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