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Nuclear Theory·nucl-th

Monday·November 12, 2018

9 papers—7 primary·2 cross-listed

All9Primary7Cross-lists2
  1. 01

    New Results for the p7Be-->8Bgamma Astrophysical S-factor from 10 keV to 5 MeV and Reactions Rate from 0.01 to 10 T9

    Dubovichenko S.B. · Burkova N.A. · Dzhazairov-Kakhramanov A.V. · Tkachenko A.S

    The astrophysical S-factor for the process p7Be --> 8Bgamma of radiative capture by the 8B ground state is described up to 5 MeV, within the modified potential cluster model. The signatures of the S-factor resonances at 0.632, 2.18 and 3.36 MeV due to M1 and E2 transitions from the scattering of resonance 3P1, 3F3 and 3D2 waves to the ground 3P2 state are illuminated using total cross sections, astrophysical S-factors and reaction rates at temperatures from 0.01 to 10.0 T9. Experimental data on the S-factor are reproduced well in the range 100 keV to 3 MeV. The importance of the input of the 0.632 MeV resonance to the reaction rate is proved. Our calculations (performed in advance) confirm the latest data for the S-factor at 19 keV.

    nucl-thNPA(2019)·11 citations
  2. 02

    New results for radiative 3He(2H,gamma)5Li capture at astrophysical energy and its possible role in accumulation of 6Li at the BBN

    S. B. Dubovichenko · N. A. Burkova · A. V. Dzhazairov-Kakhramanov · Tkachenko A.S. · Kezerashvili R.Ya. · Zazulin D.M

    Big Bang Nucleosynthesis (BBN) relevance reactions 3He(2H,{\gamma})5Li, 3H(3He,{\gamma})6Li, 5Li(n,{\gamma})6Li as a key to approach for scenario of 6Li formation are treated. The rates of reaction for these processes are analyzed. Comparison of the reactions rates and the prevalence of light elements leads to the assumption that the two-step process 2H + 3He --> 5Li + {\gamma} and n + 5Li --> 6Li + {\gamma} can make a significant contribution to the formation of 6Li at the BBN at least at temperatures T9 of the order of unity. Calculations of the total cross sections, astrophysical S-factor, and reaction rates have been performed for 3He(2H,{\gamma})5Li radiative capture within the modified potential cluster model with forbidden states, which follow from the classification of the orbital cluster states according to Young diagrams. Numerical data and corresponding parametrizations cover the energy range up to 5 MeV and temperature range T9<10. An updated compilation of detailed data for the reaction 3He(2H,{\gamma})5Li are presented.

    nucl-thNPA(2019)·7 citations
  3. 03

    Towards resolving the H lifetime puzzle

    Avraham Gal🇮🇱 · Humberto Garcilazo🇲🇽

    Recent H lifetime measurements in relativistic heavy ion collision experiments have yielded values shorter by (308)% than the free lifetime , thereby questioning the naive expectation that for a weakly bound hyperon. Here we apply the closure approximation introduced by Dalitz and coworkers to evaluate the H lifetime, using H wavefunctions generated by solving three-body Faddeev equations. Our result, disregarding pion final-state interaction (FSI), is =(0.900.01). In contrast to previous works, pion FSI is found attractive, reducing further to =(0.810.02). We also evaluate for the first time , finding it considerably longer than , contrary to the shorter lifetime values suggested by the GSI HypHI experiment for this controversial hypernucleus.

    nucl-thhep-phnucl-exPLB(2019)·44 citations
  4. 04

    A first sketch: Construction of model defect priors inspired by dynamic time warping

    Georg Schnabel🇸🇪 · Henrik Sjöstrand🇸🇪

    Model defects are known to cause biased nuclear data evaluations if they are not taken into account in the evaluation procedure. We suggest a method to construct prior distributions for model defects for reaction models using neighboring isotopes of Fe as an example. A model defect is usually a function of energy and describes the difference between the model prediction and the truth. Of course, neither the truth nor the model defect are accessible. A Gaussian process (GP) enables to define a probability distribution on possible shapes of a model defect by referring to intuitively understandable concepts such as smoothness and the expected magnitude of the defect. Standard specifications of GPs impose a typical length-scale and amplitude valid for the whole energy range, which is often not justified, e.g., when the model covers both the resonance and statistical range. In this contribution, we show how a GP with energy-dependent length-scales and amplitudes can be constructed from available experimental data. The proposed construction is inspired by a technique called dynamic time warping used, e.g., for speech recognition. We demonstrate the feasibility of the data-driven determination of model defects by inferring a model defect of the nuclear models code TALYS for (n,p) reactions of isotopes with charge number between 20 and 30. The newly introduced GP parametrization besides its potential to improve evaluations for reactor relevant isotopes, such as Fe, may also help to better understand the performance of nuclear models in the future.

    nucl-thnucl-exphysics.data-anEPJ Web Conf.(2019)·6 citations
  5. 05

    Semiclassical and quantum shell-structure calculations of the moment of inertia

    D.V. Gorpinchenko🇺🇦 · A.G. Magner🇺🇦 · J. Bartel🇫🇷

    Shell corrections to the moment of inertia (MI) are calculated for a Woods-Saxon potential of spheroidal shape and at different deformations. This model potential is chosen to have a large depth and a small surface diffuseness which makes it resemble the analytically solved spheroidal cavity in the semiclassical approximation. For the consistent statistical-equilibrium collective rotations, the MI is obtained within the cranking model in an approach which goes beyond the quantum perturbation approximation based on the non perturbative energy spectrum. For the calculation of the MI shell corrections , the Strutinsky smoothing procedure is used to obtain the average occupation numbers of the particle density generated by the resolution of the Woods-Saxon eigenvalue problem. One finds that the major-shell structure of , as determined in the adiabatic approximation, is rooted, for large as well as for small surface deformations, in the same inhomogenuity of the distribution of single-particle states near the Fermi surface as the energy shell corrections . This fundamental property is in agreement with the semiclassical results obtained analytically within the non perturbative periodic orbit theory for any potential well, in particular for the spheroidal cavity, and for any deformation, even for large deformations where bifurcations of the equatorial orbits play a substantial role. Since the adiabatic approximation, , with the distance between major nuclear shells, is easily obeyed even for large angular momenta typical for high-spin physics at large particle numbers, our model approach seems to represent a tool that could be useful for the description of such nuclear systems.

    nucl-thIJMPE(2021)·3 citations
  6. 06

    Elliptic flow fluctuations in central collisions of spherical and deformed nuclei

    Giuliano Giacalone🇫🇷

    Elliptic flow () fluctuations in central heavy-ion collisions are direct probes of the fluctuating geometry of the quark-gluon plasma, and, as such, are strongly sensitive to any deviation from spherical symmetry in the shape of the colliding nuclei. We investigate the consequences of nuclear deformation for fluctuations, and we assess whether current models of medium geometry are able to predict and capture such effects. Assuming linear hydrodynamic response between and the eccentricity of the medium, , we perform accurate comparisons between model calculations of fluctuations and STAR data on cumulants of elliptic flow, in central Au+Au and U+U collisions. From these comparisons, we evince that the most distinct signatures of nuclear deformation appear in the non-Gaussianities of fluctuation, and we show, in particular, that the non-Gaussian fluctuations currently observed in central Au+Au collisions are incompatible with model calculations that implement a quadrupole coefficient of order 12\% in the Au nuclei. Finally, we make robust predictions for the behavior of higher-order cumulants of in collisions of non-spherical nuclei.

    nucl-thhep-phnucl-exPRC(2019)·36 citations
  7. 07

    From the liquid drop model to lattice QCD

    V. Somà🇫🇷

    The present article aims to give a concise account of the main developments in nuclear structure theory, from its origin in the 1930s to date, taking the modelling of inter-nucleon interactions as guideline.

    nucl-thnucl-exEur.Phys.J.Plus(2018)·13 citations

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first authorsco-authorsvia INSPIRE