Fri·Sep 3, 2021Friday·September 3, 2021

1. 01*

   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 $E_{\mathrm{lab}}$=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
2. 02*

   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 ${\beta }_2$ and triaxiality $\gamma$. 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 ${\epsilon }_2$ and the density gradient $d_{\perp }$ in the initial state. Using analytical estimate and a Glauber model, I show that the variances, $⟨{\epsilon }_2^2⟩$ or $⟨(\delta d_{\perp }/d_{\perp }{)}^2⟩$, and skewnesses, $⟨{\epsilon }_2^2\delta d_{\perp }/d_{\perp }⟩$ or $⟨(\delta d_{\perp }/d_{\perp }{)}^3⟩$, have a simple analytical form of $a^{\prime }+b^{\prime }{\beta }_2^2$ and $a^{\prime }+(b^{\prime }+c^{\prime }\cos (3\gamma )){\beta }_2^3$, respectively. From these, I constructed several normalized skewnesses to isolate the $\gamma$ dependence from that of ${\beta }_2$, and show that the correlations between any normalized skewness and any variance can constrain simultaneously the ${\beta }_2$ and $\gamma$. Assuming a linear relation with elliptic flow $v_2$ and mean-transverse momentum $[p_{\mathrm{T}}]$ of final state particles, similar conclusions are also expected for the variances and skewnesses of $v_2$ and $[p_{\mathrm{T}}]$. 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, $\cos (3\gamma )=1$, and oblate nuclei, $\cos (3\gamma )=-1$, with well known ${\beta }_2$ values to calibrate the coefficients $b^{\prime }$ and $c^{\prime }$, followed by collisions of species of interest especially those with known ${\beta }_2$ but unknown $\gamma$. 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
3. 03*

   uRANIA-V: an innovative solution for neutron detection in homeland security

   R. Farinelli🇮🇹 · I. Balossino🇮🇹 · G. Bencivenni🇮🇹 · G. Cibinetto🇮🇹 · G. Felici🇮🇹 · S. Fiore🇮🇹 · I. Garzia🇮🇹 · M. Gatta🇮🇹 · M. Giovannetti🇮🇹 · R. Hall-Wilton🇸🇪 · C. C. Lai🇸🇪 · L. Lavezzi🇮🇹 and 10 other authors

   Detection of neutrons is becoming of the utmost importance, especially in the studies of radioactive waste and in homeland security applications. The crisis of 3He availability has required the development of innovative techniques. One solution is to develop light gas detectors for neutron counting to be used as portals for ports and airports. The neutron is converted on the Boron-coated cathode, releasing a charged particle, whose passage can be identified by the gas detector. While several technologies have been deployed in the past, the project {\mu}RANIA-V ( {\mu}Rwell Advanced Neutron Identification Apparatus) aims to detect thermal neutrons by means of the {\mu}Rwell technology, an innovative gas detector. The goal is to produce tiles to operate as portals in homeland security or for radioactive waste management. The technological transfer towards the industry has started, thus the production can be cost-effective also owing to a construction process relatively easier compared to similar apparatus. By reading directly the signals from the amplification stage, the neutrons can be counted with simplified electronics further reducing the total cost. In this paper, the project will be described, with details on the {\mu}Rwell technology and on the neutron counting, on the test beam performed, and on the future plans.

   ↳ physics.ins-dethep-exnucl-ex2 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.