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Nuclear Theory·nucl-th

Tuesday·September 24, 2019

14 papers—7 primary·7 cross-listed

All14Primary7Cross-lists7
  1. 01

    Constraining level densities through quantitative correlations with cross-section data

    G. P. A. Nobre · D. A. Brown · M. W. Herman · A. Golas

    The adopted level densities (LD) for the nuclei produced through different reaction mechanisms significantly impact the calculation of cross sections for the many reaction channels. Common LD models make simplified assumptions regarding the overall behavior of the total LD and the intrinsic spin and parity distributions of the excited states. However, very few experimental constraints are taken into account: LD at neutron separation energy coming from average resonance spacings, whenever they have been previously measured, and the sometimes subjective extrapolation of discrete levels. These, however, constrain the LD only for very specific spins, parities and excitation energies. This work aims to establish additional experimental constraints on LD through quantitative correlations between cross sections and LD. This allows for the fitting and determination of detailed structures in LD. For this we use the microscopic Hartree-Fock-Bogoliubov (HFB) LD to associate variations predicted by the model with the structure observed in double-differential spectra at low outgoing neutron energy, which is dominated by the LD input. We also use \nuc{56}{Fe} () as an example cross sections are extremely sensitive to LD. For comparison purposes we also perform calculations with the GC model. With this approach we are able to perform fits of the LD based on actual experimental data, constraining the model and ensuring its consistency. This approach can be particularly useful in extrapolating the LD to nuclei for which high-excited discrete levels and/or resonance spacings are unknown. It also predicts inelastic gamma cross sections that can significantly differ from more standard phenomenological LD.

    nucl-thPRC(2020)·8 citations
  2. 02

    Antiproton production in heavy-ion collisions at subthreshold energies

    Zhao-Qing Feng🇨🇳

    Within the framework of the Lanzhou quantum molecular dynamics model, the deep subthreshold antiproton production in heavy-ion collisions has been investigated thoroughly. The elastic scattering, annihilation and charge exchange reactions associated with antiproton channels are implemented in the model. The attractive antiproton potential extracted from the G-parity transformation of the nucleon selfenergies enhance the antiproton yields to some extent. The calculated invariant spectra are consistent with the available experimental data. The primordial antiproton yields increase with the mass number of colliding system. However, the annihilation reactions reduce the antiproton production and enable independent to colliding partners. Antiflow phenomena of antiprotons correlated to the mean-field potential and annihilation mechanism is found in comparison with proton flows.

    nucl-thCPC(2020)·1 citation
  3. 03

    Strangeness and hypernuclear production in fragmentation reactions induced by antikaons

    Zhao-Qing Feng🇨🇳

    Formation mechanism of hyperfragments with strangeness s=-1 and s=-2 in collisions of antikaons on nuclei has been investigated within a microscopic transport model. Dynamics of pseudoscalar mesons and hyperons is modeled within the transport model, in which all possible reaction channels for creating hyperons such as the elastic scattering, resonance production and decay, strangeness exchange reaction and direct strangeness production in meson-baryon and baryon-baryon collisions have been included. A coalescence approach is developed for constructing hyperfragments in phase space and the decay process is described with a statistical approach. It is found that the production is correlated to the K formation and the hyperons and are created within a broad rapidity region. The production cross sections of nucleonic fragments and hyperfragments weakly depends on the incident momentum. The yields of hyperfragments are the six order of magnitude of hyperfragments.

    nucl-thPRC(2020)·6 citations
  4. 04

    Modeling photon--induced reactions on U actinide targets

    M. Sin · R. Capote · M.W. Herman · A. Trkov · B.V. Carlson

    Comprehensive calculations of cross sections of photon induced reactions on U targets for incident photon energies from 3 up to 30 MeV are undertaken with the statistical model code EMPIRE-3.2 Malta. Results are compared with the experimental data from EXFOR and with the current evaluations. The differences and the similarities between the models and parameters used in calculations of photon- and neutron-induced reactions on the same nuclei are discussed with focus on fission. The role of the extended optical model for fission in improving the description of the measured data and in determining consistent sets of barrier parameters is pointed out.

    nucl-thPRC(2021)·6 citations
  5. 05

    Signatures of octupole shape phase transitions in radioactive nuclei

    Kosuke Nomura

    We analyze the octupole deformations and the related collective excitations in medium-heavy and heavy nuclei based on the microscopic framework of the nuclear energy density functional theory. Constrained self-consistent mean-field calculation with a given energy density functional is performed to provide for each nucleus a potential energy surface with axial quadrupole and octupole shape degrees of freedom. Spectroscopic properties are computed by means of the interacting-boson Hamiltonian, which is determined by mapping the fermionic potential energy surface onto the bosonic counterpart. The overall systematics of the calculated spectroscopic observables exhibit phase transitional behaviors between stable octupole deformation and octupole vibration characteristic of the octupole-soft potential within the set of nuclei in light actinide and rare-earth regions, Th, Ra, Sm, Gd, and Ba isotopes, where octupole shapes are most likely to occur.

    nucl-thJ.Phys.Conf.Ser.(2020)·0 citations
  6. 06

    A quartet BCS-like theory

    V. V. Baran · D. S. Delion

    We introduce a BCS-like theory for the quartet correlations induced by the isovector pairing interaction. It is based on a coherent state of BCS type and, unlike usual mean field approaches, it displays a vanishing pair anomalous density . We find good agreement between our theory and the exact results. We discuss how the pairing and quarteting correlations share some similar qualitative features within the BCS approach. However, there is no sharp quarteting phase transition. We also present various ways in which our theory may be further developed.

    nucl-thPLB(2020)·23 citations
  7. 07

    Quantifying multinucleon effect in Argon using high-pressure TPC

    Jaydip Singh🇮🇳 · Srishti Nagu🇮🇳 · Jyotsna Singh🇮🇳 · R.B. Singh🇮🇳

    Neutrino oscillation experiments use heavy nuclear targets to achieve sufficient interaction rates. Nuclear effects are introduced in the experimental environment by the use of these targets and need to be quantified as they add to the systematic errors. In the low energy region(around 1 GeV) multinucleon events are also present along with Quasi Elastic(QE) and Delta interactions. Therefore if these multinucleon events are not incorporated in the data set properly, we end up with an inaccurate reconstruction of neutrino energy. In our work, we have illustrated the importance of incorporation of multinucleon events for the reduction of systematic errors in physics predictions by DUNE-Near Detector(ND). To achieve this we have presented the event distribution ratio of Ar/C, Ar/Ar, and C/C as a function of squared four-momentum transfer by employing different nuclear models. This analysis recommends the addition of 2p2h or multinucleon events in the event sample and promotes model with Random Phase Approximations(RPA) effect for the analysis of the event sample to overcome or reduce the systematic uncertainties.

    nucl-thhep-phNPB(2020)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE