Tue·Sep 29, 2020Tuesday·September 29, 2020

1. 01*

   Mass measurements for $T_z=-2$ $fp$-shell nuclei ${}^{40}$Ti, ${}^{44}$Cr, ${}^{46}$Mn, ${}^{48}$Fe, ${}^{50}$Co and ${}^{52}$Ni

   C. Y. Fu🇨🇳 · Y. H. Zhang🇨🇳 · M. Wang🇨🇳 · X. H. Zhou🇨🇳 · Yu. A. Litvinov🇩🇪 · K. Blaum🇩🇪 · H. S. Xu🇨🇳 · X. Xu🇨🇳 · P. Shuai🇨🇳 · Y. H. Lam🇨🇳 · R. J. Chen🇨🇳 · X. L. Yan🇨🇳 and 17 other authors

   By using isochronous mass spectrometry (IMS) at the experimental cooler storage ring CSRe, masses of short-lived ${}^{44}$Cr, ${}^{46}$Mn, ${}^{48}$Fe, ${}^{50}$Co and ${}^{52}$Ni were measured for the first time and the precision of the mass of ${}^{40}$Ti was improved by a factor of about 2. Relative precisions of $\delta m/m=(1-2)\times$10${}^{-6}$ have been achieved. Details of the measurements and data analysis are described. The obtained masses are compared with the Atomic-Mass Evaluation 2016 (AME${}^{\prime }$16) and with theoretical model predictions. The new mass data enable us to extract the higher order coefficients, $d$ and $e$, of the quartic form of the isobaric multiplet mass equation (IMME) for the $fp$-shell isospin quintets. Unexpectedly large $d$- and $e$-values for $A=44$ quintet are found. By re-visiting the previous experimental data on $\beta$-delayed protons from ${}^{44}$Cr decay, it is suggested that the observed anomaly could be due to the misidentification of the $T=2$, $J^{\pi }=0^{+}$ isobaric analog state (IAS) in ${}^{44}$V.

   nucl-exPRC(2020)·14 citations
2. 02*

   Multi-neutron transfer in ${}^8$He induced reactions near the Coulomb barrier

   I. Martel🇬🇧 · N. Keeley · K.W. Kemper🇺🇸 · K. Rusek

   The measured inclusive ${}^6$He and ${}^4$He production cross sections of G. Marquínez-Durán {\em et al.}, Phys.\ Rev.\ C {\bf 98}, 034615 (2018) are reexamined and the conclusions concerning the relative importance of 1n and 2n transfer to the production of ${}^6$He arising from the interaction of a 22 MeV ${}^8$He beam with a ${}^{208}$Pb target revised. A consideration of the kinematics of the 2n-stripping reaction when compared with the measured ${}^6$He total energy versus angle spectrum places strict limits on the allowed excitation energy of the ${}^{210}$Pb residual, so constraining distorted wave Born approximation calculations that the contribution of the 2n stripping process to the inclusive ${}^6$He production can only be relatively small. It is therefore concluded that the dominant ${}^6$He production mechanism must be 1n stripping followed by decay of the ${}^7$He ejectile. Based on this result we present strong arguments in favor of direct, one step four-neutron (4n) stripping as the main mechanism for ${}^4$He production.

   nucl-exnucl-thPRC(2020)·5 citations
3. 03*

   Low Energy measurement of the ${}^{96}\mathrm{Zr}(\alpha ,n{)}^{99}\mathrm{Mo}$ reaction cross section and its impact on weak r-process nucleosynthesis

   G. G. Kiss🇭🇺 · T. N. Szegedi🇭🇺 · P. Mohr🇭🇺 · M. Jacobi🇩🇪 · Gy. Gyürky🇭🇺 · R. Huszánk🇭🇺 · A. Arcones🇩🇪

   Lighter heavy elements beyond iron and up to around silver can form in neutrino-driven ejecta in core-collapse supernovae and neutron star mergers. Slightly neutron-rich conditions favour a weak r-process that follows a path close to stability. Therefore, the beta decays are slow compared to the expansion time scales, and ($\alpha$,n) reactions become critical to move matter towards heavier nuclei. The rates of these reactions are calculated with the statistical model and their main uncertainty, at energies relevant for the weak r-process, is the $\alpha$+nucleus optical potential. There are several sets of parameters to calculate the $\alpha$+nucleus optical potential leading to large deviations for the reaction rates, exceeding even one order of magnitude. Recently the ${}^{96}$Zr($\alpha$,n)${}^{99}$Mo reaction has been identified as a key reaction that impacts the production of elements from Ru to Cd. Here, we present the first cross section measurement of this reaction at energies (6.22 MeV $\le$ E${}_{c.m.}$ $\le$ 12.47 MeV) relevant for the weak r-process. The new data provide a stringent test of various model predictions which is necessary to improve the precision of the weak r-process network calculations. The strongly reduced reaction rate uncertainty leads to very well-constrained nucleosynthesis yields for $Z=44-48$ isotopes under different neutrino-driven wind conditions.

   nucl-exApJ(2021)·23 citations
4. 04*

   Associated production in pp and heavy ion collisions

   Hua-Sheng Shao🇫🇷

   Associated particle production processes in pp and heavy ion collisions at the LHC are in particular interesting in the sense that they provide unique tools to study double parton scattering (DPS) mechanism. In this talk, I will first review the recent theoretical, phenomenological and experimental developments of DPS in pp collisions. Then, I will focus on the DPS studies in heavy ion collisions, and stress their roles in understanding the cold nuclear matter effects, such as the (poorly known) impact-parameter dependent nuclear parton densities.

   ↳ hep-phhep-exnucl-exnucl-thPoS(2021)·1 citation
5. 05*

   Study of Cluster Structures in Nuclei through the Ratio Method. A Tribute to Mahir Hussein

   Pierre Capel🇧🇪 · Ronald C. Johnson · Filomena M. Nunes🇺🇸

   For one-neutron halo nuclei, the cross section for elastic scattering and breakup at intermediate energy exhibit similar angular dependences. The Recoil Excitation and Breakup (REB) model of reactions elegantly explains this feature. It also leads to the idea of a new reaction observable to study the structure of loosely-bound nuclear systems: the Ratio. This observable consists of the ratio of angular distributions for different reaction channels, viz. elastic scattering and breakup, which cancels most of the dependence on the reaction mechanism; in particular it is insensitive to the choice of optical potentials that simulate the projectile-target interaction. This new observable is very sensitive to the structure of the projectile. In this article, we review the Ratio Method and its extension to low beam energies and proton-halo nuclei.

   ↳ nucl-thnucl-exEPJA(2020)·5 citations
6. 06*

   Generalized Lomb-Scargle analysis of ${}^{123}\mathrm{I}$ and ${}^{99m}\mathrm{Tc}$ decay rate measurements

   Gautham Gururajan · Shantanu Desai🇮🇳

   We apply the generalized Lomb-Scargle periodogram to the ${}^{123}\mathrm{I}$ and ${}^{99m}\mathrm{Tc}$ decay rate measurements based on data taken at the Bronson Methodist Hospital. The aim of this exercise was to carry out an independent search for sinusoidal modulation for these radionuclei (to complement the analysis in Borrello et al) at frequencies for which other radionuclei have shown periodicities. We do not find evidence for such a modulation at any frequencies, including annual modulation or at frequencies associated with solar rotation. Our analysis codes and datasets have been made publicly available.

   ↳ astro-ph.SRastro-ph.IMnucl-exEPJC(2020)·1 citation
7. 07*

   Ultracold Neutron Properties of the Eljen-299-02D deuterated scintillator

   Z. Tang🇺🇸 · E. B. Watkins · S. M. Clayton🇺🇸 · S. A. Currie🇺🇸 · D. E. Fellers🇺🇸 · Md. T. Hassan🇺🇸 · D. E. Hooks · T. M. Ito🇺🇸 · S. K. Lawrence · S. W. T. MacDonald🇺🇸 · M. Makela · C. L. Morris🇺🇸 and 15 other authors

   In this paper we report studies of the Fermi potential and loss per bounce of ultracold neutron (UCN) on a deuterated scintillator (Eljen-299-02D). These UCN properties of the scintillator enables a wide variety of applications in fundamental neutron research.

   ↳ physics.ins-detnucl-exRev.Sci.Instrum.(2021)·4 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.