Nuclear Theory·nucl-th

Friday·September 3, 2021

3 papers—2 primary·1 cross-listed

01
Probing triaxial deformation of atomic nuclei in high-energy heavy ion collisions
Jiangyong Jia🇺🇸
Most atomic nuclei are deformed with a quadrupole shape described by its overall strength $β_{2}$ and triaxiality $γ$ . The deformation can be accessed in high-energy heavy-ion collisions by measuring the collective flow response of the produced quark-gluon plasma to the eccentricity $ε_{2}$ and the density gradient $d_{⊥}$ in the initial state. Using analytical estimate and a Glauber model, I show that the variances, $⟨ ε_{2}^{2} ⟩$ or $⟨(δ d_{⊥} / d_{⊥})^{2} ⟩$ , and skewnesses, $⟨ ε_{2}^{2} δ d_{⊥} / d_{⊥} ⟩$ or $⟨(δ d_{⊥} / d_{⊥})^{3} ⟩$ , have a simple analytical form of $a^{'} + b^{'} β_{2}^{2}$ and $a^{'} + (b^{'} + c^{'} cos (3 γ)) β_{2}^{3}$ , respectively. From these, I constructed several normalized skewnesses to isolate the $γ$ dependence from that of $β_{2}$ , and show that the correlations between any normalized skewness and any variance can constrain simultaneously the $β_{2}$ and $γ$ . Assuming a linear relation with elliptic flow $v_{2}$ and mean-transverse momentum $[p_{T}]$ of final state particles, similar conclusions are also expected for the variances and skewnesses of $v_{2}$ and $[p_{T}]$ . Our findings motivate a dedicated system scan of high-energy heavy ion collisions to measure triaxiality of atomic nuclei. This is better done by collisions of prolate, $cos (3 γ) = 1$ , and oblate nuclei, $cos (3 γ) = - 1$ , with well known $β_{2}$ values to calibrate the coefficients $b^{'}$ and $c^{'}$ , followed by collisions of species of interest especially those with known $β_{2}$ but unknown $γ$ . The results demonstrate the unique opportunities offered by high-energy collisions as a tool to perform interdisciplinary nuclear physics studies.
nucl-thhep-phnucl-exPRC(2022)·108 citations
02
Semiempirical formula for electroweak response functions in the two-nucleon emission channel in neutrino-nucleus scattering
V.L. Martinez-Consentino🇪🇸 · J.E. Amaro🇪🇸 · I. Ruiz Simo🇪🇸
A semi-empirical formula for the electroweak response functions in the two-nucleon emission channel is proposed. The method consists in expanding each one of the vector-vector, axial-axial and vector-axial responses as sums of six sub-responses. These corresponds to separating the meson-exchange currents as the sum of three currents of similar structure, and expanding the hadronic tensor, as the sum of the separate contributions from each current plus the interferences between them. For each sub-response we factorize the coupling constants, the electroweak form factors, the phase space and the delta propagator, for the delta forward current. The remaining spin-isospin contributions are encoded in coefficients for each value of the momentum transfer, $q$ . The coefficients are fitted to the exact results in the relativistic mean field model of nuclear matter, for each value of $q$ . The dependence on the energy transfer, $ω$ is well described by the semi-empirical formula. The $q$ -dependency of the coefficients of the sub-responses can be parameterized or can be interpolated from the provided tables. The description of the five theoretical responses is quite good. The parameters of the formula, the Fermi momentum, number of particles relativistic effective mass, vector energy the electroweak form factors and the coupling constants, can be modified easily. This semi-empirical formula can be applied to the cross-section of neutrinos, antineutrinos and electrons.
nucl-thhep-phPRD(2021)·21 citations
03
Reaction mechanism study for multinucleon transfer processes in collisions of spherical and deformed nuclei at energies near and above the Coulomb barrier: The $^{16}$ O+ $^{154}$ Sm reaction
B. J. Roy · S. Santra · A. Pal · H. Kumawat · S. K. Pandit · V. V. Parkar · K. Ramachandran · K. Mahata · K. Sekizawa
Background: Multinucleon transfer reactions at energies around the Coulomb barrier offer a vital opportunity to study rich physics of nuclear structure and dynamics. Despite the continuous development in the field, we have still limited knowledge about how deformation - one of the representative nuclear structures - affects multinucleon transfer reactions. Purpose: To shed light on the effect of deformation in multinucleon transfer processes, we study the $^{16}$ O+ $^{154}$ Sm reaction at $E_{lab}$ =85 MeV (around the Coulomb barrier) and 134 MeV (substantially above the Coulomb barrier), where the target nucleus, $^{154}$ Sm, is a well-established, deformed nucleus. Results: Angular distributions for elastic scattering and for various transfer channels were measured over a wide angular range at the BARC-TIFR pelletron-Linac accelerator facility, Mumbai. The $Q$ -value- and angle-integrated isotope production cross sections have been extracted from the measured angular distributions. The experimental data are analyzed along with time-dependent Hartree-Fock calculations. For the lower incident energy case, we find a reasonable agreement between the measurements and the TDHF calculations for a-few-nucleon transfer channels; whereas TDHF underestimates cross sections for many-nucleon transfers, consistent with earlier works. On the other side, we find that calculated cross sections for secondary reaction products for the higher incident energy case, qualitatively explains the measured trends of isotopic distributions observed for the lower energy. The latter observation indicates possible underestimation of excitation energies in the present TDHF+GEMINI analysis. Although certain orientation effects were observed in TDHF results, it is difficult to disentangle them from the $Q$ -value- and angle-integrated production cross sections. (Shortened due to the arXiv's length limit.)
↳ nucl-exnucl-thPRC(2022)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE

Probing triaxial deformation of atomic nuclei in high-energy heavy ion collisions

Semiempirical formula for electroweak response functions in the two-nucleon emission channel in neutrino-nucleus scattering

Reaction mechanism study for multinucleon transfer processes in collisions of spherical and deformed nuclei at energies near and above the Coulomb barrier: The 16O+154Sm reaction

Affiliations

Reaction mechanism study for multinucleon transfer processes in collisions of spherical and deformed nuclei at energies near and above the Coulomb barrier: The $^{16}$ O+ $^{154}$ Sm reaction