Nuclear Theory·nucl-th

Friday·October 12, 2018

12 papers—6 primary·6 cross-listed

01
Non-local interactions in the $(d, p)$ surrogate method for $(n, γ)$ reactions
Weichuan Li · Gregory Potel · Filomena Nunes
Single-neutron transfer reactions populating states in the continuum are interesting both for structure and astrophysics. In their description often global optical potentials are used for the nucleon-target interactions, and these interactions are typically local. In our work, we study the effects of nonlocality in $(d, p)$ reactions populating continuum states. This work is similar to that of [1] but now for transfer to the continuum. A theory for computing cross sections for inclusive processes $A (d, p) X$ was explored in [2]. Therein, local optical potentials were used to describe the nucleon-target effective interaction. The goal of the present work is to extend the theory developed in [2] to investigate the effects of including nonlocality in the effective interaction on the relevant reaction observables. We implement the R--matrix method to solve the non--local equations both for the nucleon wavefunctions and the propagator. We then apply the method to systematically study the inclusive process of $(d, p)$ on $^{16}$ O, $^{40}$ Ca, $^{48}$ Ca and $^{208}$ Pb at 10, 20 and 50 MeV. We compare the results obtained when non--local interactions are used with those obtained when local equivalent interactions are included. We find that nonlocality affects different pieces of the model in complex ways. Depending on the beam energy and the target, the non-elastic breakup can either increase or decrease. While the non-elastic transfer cross section for each final spin state can change considerably, the main prediction of the model [2], namely the shape of the spin distributions, remains largely unaltered by nonlocality. [1] L. J. Titus and F. M. Nunes. Testing the Perey effect. Phys. Rev. C, 89:034609, Mar 2014. [2] G. Potel, F. M. Nunes, and I. J. Thompson. Establishing a theory for deuteron-induced surrogate reactions. Phys. Rev. C, 92:034611, Sep 2015.
nucl-thPRC(2018)·12 citations
02
Blind spots of probing the high-density symmetry energy in heavy-ion collisions
Gao-Chan Yong🇨🇳
The nuclear symmetry energy, especially at suprasaturation densities, plays crucial roles in many astrophysical studies. However, nowadays the high-density behavior of the symmetry energy is still very controversial in nuclear community. To constrain the high-density behavior of the symmetry energy, neutron-rich nuclei collisions at medium energies are considered to be one of the most effective methods. While probing the high-density symmetry energy by using heavy-ion collisions, blind spots may exist. In the framework of the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, the blind spots of probing the high-density symmetry energy by the n/p ratio in the central Au+Au reaction at 300 MeV/nucleon are demonstrated. It is found that the nucleon observable neutron to proton ratio n/p in heavy-ion collisions cannot effectively probe the high-density symmetry energy when the high-density symmetry energy is less density-dependent.
nucl-thnucl-exPLB(2018)·5 citations
03
In-medium properties of a $Ξ N$ interaction derived from chiral effective field theory
J. Haidenbauer🇩🇪 · U.-G. Meißner🇩🇪
The in-medium properties of a baryon-baryon interaction for the strangeness $S = - 2$ sector derived within chiral effective field theory up to next-to-leading order are investigated. The considered $Ξ N$ interaction is in line with available empirical constraints on the $ΛΛ$ $S$ -wave scattering length and on $Ξ N$ elastic and inelastic cross sections. In particular, there are no near-threshold bound states in the $Ξ N$ system. A conventional $G$ -matrix calculation for this interaction is performed and reveals that the single-particle potential of the $Ξ$ -hyperon in nuclear matter is moderately attractive as suggested by recent experimental evidence for the existence of $Ξ$ -hypernuclei.
nucl-thEPJA(2019)·60 citations
04
Phase structure of neutron $^{3} P_{2}$ superfluids in strong magnetic fields in neutron stars
Shigehiro Yasui🇯🇵 · Chandrasekhar Chatterjee🇯🇵 · Muneto Nitta🇯🇵
We discuss the effect of a strong magnetic field on neutron $^{3} P_{2}$ superfluidity. Based on the attraction in the $^{3} P_{2}$ pair of two neutrons, we derive the Ginzburg-Landau equation in the path-integral formalism by adopting the bosonization technique and leave the next-to-leading order in the expansion of the magnetic field $B$ . We determine the $(T, B)$ phase diagram with temperature $T$ , comprising three phases: the uniaxial nematic (UN) phase for $B = 0$ , D $_{2}$ -biaxial nematic (BN) and D $_{4}$ -BN phases in finite $B$ and strong $B$ such as magnetars, respectively, where D $_{2}$ and D $_{4}$ are dihedral groups. We find that, compared with the leading order in the magnetic field known before, the region of the D $_{2}$ -BN phase in the $(T, B)$ plane is extended by the effect of the next-to-leading-order terms of the magnetic field. We also present the thermodynamic properties, such as heat capacities and spin susceptibility, and find that the spin susceptibility exhibits anisotropies in the UN, D $_{2}$ -BN, and D $_{4}$ -BN phases. This information will be useful to understand the internal structures of magnetars.
nucl-thastro-ph.HEcond-mat.supr-conhep-phPRC(2019)·21 citations
05
Two-phonon structures for beta-decay theory
A. P. Severyukhin · N. N. Arsenyev · I. N. Borzov · R. G. Nazmitdinov · S. Åberg
The $β$ -decay rates of $^{60}$ Ca have been studied within a microscopic model, which is based on the Skyrme interaction T45 to construct single-particle and phonon spaces. We observe a redistribution of the Gamow-Teller strength due to the phonon-phonon coupling, considered in the model. For $^{60}$ Sc, the spin-parity of the ground state is found to be $1^{+}$ . We predict that the half-life of $^{60}$ Ca is 0.3 ms, while the total probability of the $β x n$ emission is 6.1%. Additionally, the random matrix theory has been applied to analyse the statistical properties of the $1^{+}$ spectrum populated in the $β$ -decay to elucidate the obtained results.
nucl-thEPJ Web Conf.(2018)·0 citations
06
Determination of the photodisintegration reaction rates involving charged particles: systematical calculations and proposed measurements based on Extreme Light Infrastructure - Nuclear Physics (ELI-NP)
H.Y. Lan · Y. Xu · W. Luo · D.L. Balabanski · S. Goriely · M. La Cognata · C. Matei · A. Anzalone · S. Chesnevskaya · G.L. Guardo · D. Lattuada · R.G. Pizzone and 5 other authors
Photodisintegration reaction rates involving charged particles are of relevance to the p-process nucleosynthesis that aims at explaining the production of the stable neutron-deficient nuclides heavier than iron. In this study, the cross sections and astrophysical rates of (g,p) and (g,a) reactions for about 3000 target nuclei with 10<Z<100 ranging from stable to proton dripline nuclei are computed. To study the sensitivity of the calculations to the optical model potentials (OMPs), both the phenomenological Woods-Saxon and the microscopic folding OMPs are taken into account. The systematic comparisons show that the reaction rates, especially for the (g,a) reaction, are dramatically influenced by the OMPs. Thus the better determination of the OMP is crucial to reduce the uncertainties of the photodisintegration reaction rates involving charged particles. Meanwhile, a gamma-beam facility at ELI-NP is being developed, which will open new opportunities to experimentally study the photodisintegration reactions of astrophysics interest. Considering both the important reactions identified by the nucleosynthesis studies and the purpose of complementing the experimental results for the reactions involving p-nuclei, the measurements of six (g,p) and eight (g,a) reactions based on the gamma-beam facility at ELI-NP and the ELISSA detector for the charged particles detection are proposed, and the GEANT4 simulations are correspondingly performed. The minimum required energies of the gamma-beam to measure these reactions are estimated. It is shown that the direct measurements of these photonuclear reactions within the Gamow windows at T_9=2.5 for p-process are fairly feasible and promising at ELI-NP. The expected experimental results will be used to constrain the OMPs of the charged particles, which can eventually reduce the uncertainties of the reaction rates for the p-process nucleosynthesis.
nucl-thastro-ph.SRnucl-exPRC(2018)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE

Non-local interactions in the (d,p) surrogate method for (n,γ) reactions

Blind spots of probing the high-density symmetry energy in heavy-ion collisions

In-medium properties of a ΞN interaction derived from chiral effective field theory

Phase structure of neutron 3P2​ superfluids in strong magnetic fields in neutron stars

Two-phonon structures for beta-decay theory

Determination of the photodisintegration reaction rates involving charged particles: systematical calculations and proposed measurements based on Extreme Light Infrastructure - Nuclear Physics (ELI-NP)

Affiliations

Non-local interactions in the $(d, p)$ surrogate method for $(n, γ)$ reactions

In-medium properties of a $Ξ N$ interaction derived from chiral effective field theory

Phase structure of neutron $^{3} P_{2}$ superfluids in strong magnetic fields in neutron stars