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Nuclear Theory·nucl-th

Wednesday·July 10, 2024

15 papers—6 primary·9 cross-listed

All15Primary6Cross-lists9
  1. 01

    Viscous damping of r-modes and emission of gravitational waves

    Debasis Atta🇮🇳 · D. N. Basu🇮🇳

    The Rossby mode (r-mode) perturbation in pulsars as a steady gravitational wave (GW) source has been explored. The effect of a rigid crust on viscous damping and dissipation rate in the boundary layer between fluid core and crust has been studied. The intensity of the emitted GWs in terms of the strain tensor amplitude has been estimated with the approximation of slow rotation using equation of state derived from the APR and Skyrme effective interactions with Brussels-Montreal parameter sets. The core of the neutron star has been considered to be -equilibrated nuclear matter containing neutrons, protons, electrons and muons, surrounded by a solid crust. Calculations have been made for critical frequencies, the time evolution and the rate of change of the spin frequencies across a broad spectrum of pulsar masses.

    nucl-thPramana(2025)·2 citations
  2. 02

    Angular anisotropy in prefission neutron spectra and PFNS of Pu

    V.M. Maslov

    Angular anisotropy of secondary neutrons was evidenced in neutron emission spectra (NES) of Pu+n in 1972, and prompt fission neutron spectra (PFNS) of Pu in 2019, it might be predicted for Pu(n,F) PFNS now. In case of NES angular anisotropy is due to direct excitation of collective levels and pre-equilibrium/semi-direct (states in the continuum are excited) mechanism of neutron emission of first neutron in (n,nX) reaction, while in case of PFNS it is due to exclusive spectra of pre-fission neutrons of (n, xnf) reactions. In Pu and Pu(n,xnf) reactions observed PFNS envision different response to the emission of first pre-fission neutron in forward or backward semi-spheres with respect to the momentum of incident neutrons. Since energies of (n,nf) neutrons and their average values depend on angle of emission theta with respect to the incident neutron momentum, the observed PFNS, average prompt fission neutron multiplicity, fission cross section, average total kinetic energy TKE, etc. also would be quite dependent on angle theta. Exclusive spectra of (n, xnf) neutrons at theta of 90 degrees are consistent with Pu(n, F)(Pu, Pu) observed cross sections and neutron emission spectra of Pu+n interaction at En up to 20 MeV. The correlations of the angular anisotropy of PFNS with the relative contribution of the fission chance to the observed fission cross section and angular anisotropy of pre-fission neutron emission are ascertained.

    nucl-thnucl-ex0 citations
  3. 03

    Electron scattering cross section for light nuclei within the unified electroweak theory

    Vo Minh Truong · Nguyen Quang Hung

    We employ the multipole expansion within the unified electroweak theory to develop a complete calculation method of the electron scattering cross section for light nuclei. The specific calculations for 6,7Li and 7Be nuclei indicate that the conventional impulse approximation can be applied to the electron-nucleus scattering only when the incident electron energy does not exceed twice the nucleon mass. In addition, the quasi-elastic scattering cross section of 7Li in the excitation from its ground state to the nearest excited state and that of elastic scattering in the ground state are independently treated, whereas they have not been separately measured in experiments. The obtained scattering cross sections corresponding to an appropriate adjustment of the harmonic oscillator parameter along with the V-A structure interpret reasonably well the available experimental data at MeV energies and provide predictive information at GeV energies. This gives new perspectives in studying the structure of nuclei and the weak interactions via electron or lepton scattering at high (GeV) energies, considering nuclei rather than quarks.

    nucl-thhep-phPRC(2024)·0 citations
  4. 04

    A Method to Constrain Preferential Emission and Spectator Dynamics in Heavy-Ion Collisions

    Vipul Bairathi🇨🇱 · Somadutta Bhatta🇺🇸

    Longitudinal particle production in heavy-ion collisions is influenced both by preferential emission from participating nucleons and by the breakup of spectator matter, yet quantifying these effects experimentally remains challenging. We introduce a Pearson correlation between spectator and charged-particle forward-backward asymmetries as an experimental probe of these phenomena. Using Au+Au collisions at GeV simulated with A Multi-Phase Transport (AMPT) model, we validate that this correlator provides a robust, pseudorapidity-differential measure of the influence of preferential emission on the longitudinal structure of particle production. We further demonstrate that the correlation strength is sensitive to fluctuations in spectator number, which in experiments arise from evaporation and fragmentation of the spectator remnants. The proposed observable therefore offers a data-driven handle for constraining models of preferential emission and spectator breakup, thereby improving our understanding of the mechanisms that shape the final-state longitudinal distributions in heavy-ion collisions.

    nucl-thhep-exhep-phnucl-exPRC(2026)·0 citations
  5. 05

    Quantum Monte Carlo calculations of electron scattering from in the Short-Time Approximation

    Lorenzo Andreoli · Garrett B. King · Saori Pastore · Maria Piarulli · Joseph Carlson · Stefano Gandolfi · Robert B. Wiringa

    The Short-Time approximation is a method introduced to evaluate electroweak nuclear response for systems with , extending the reach of first-principle many-body Quantum Monte Carlo calculations. Using realistic two- and three-body nuclear interactions and consistent one- and two-body electromagnetic currents, we calculate longitudinal and transverse response densities and response functions of . We compare the resulting cross sections with experimental data for electron-nucleus scattering, finding good agreement.

    nucl-thPRC(2024)·16 citations
  6. 06

    Enhanced yield and yield ratio as a possible signature of QGP formation in high multiplicity collisions

    Partha Bagchi🇮🇳 · Arpan Das🇮🇳 · Ananta P. Mishra🇮🇳 · Ankit Kumar Panda🇮🇳

    Suppression in the yield of quarkonia (heavy quark-antiquark bound states) has been considered one of the important signatures of the formation of the thermalized deconfined partonic matter, also known as the Quark Gluon Plasma (QGP), in Relativistic Heavy Ion Collision Experiments (RHICE). Traditionally, the in-medium dissociation of quarkonium states has been presented by implicitly assuming an adiabatic approximation, which considers that the heavy quark Hamiltonian changes slowly over time owing to change in the medium. However, in high multiplicity smaller systems, such as in collisions, the early development of transverse flow resulting from the finite transverse size of the locally thermalized medium may cause the quarkonium states to undergo a non-adiabatic evolution. It has been argued that in the presence of such a non-adiabatic evolution, the suppression of heavy quark-antiquark bound state yields may not reliably indicate QGP formation~\cite{Bagchi:2023vfv}. We propose that, rather than concentrating on the suppression of yields, the enhancement in the yield ratio of to (i.e., ), along with an increase in yield, should be considered as a probe of QGP formation for small systems. Our findings, based on realistic modeling of the time evolution of small systems, suggest that the yield ratio and the yield of increase as a function of hydrodynamization temperature incorporating the non-adiabatic transitions in high multiplicity collisions.

    nucl-thhep-ph1 citation

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first authorsco-authorsvia INSPIRE