Wed·Jul 24, 2024Wednesday·July 24, 2024

1. 01*

   Towards the Discovery of New Elements: Production of Livermorium (Z=116) with 50Ti

   J.M. Gates🇺🇸 · R. Orford🇺🇸 · D. Rudolph🇸🇪 · C. Appleton🇺🇸 · B.M. Barrios🇺🇸 · J.Y. Benitez🇺🇸 · M. Bordeau🇫🇷 · W. Botha🇺🇸 · C.M. Campbell🇺🇸 · J. Chadderton🇬🇧 · A.T. Chemey🇺🇸 · R.M. Clark🇺🇸 and 42 other authors

   The ${}^{244}$Pu(${}^{50}$Ti,$xn$)${}^{294-x}$Lv reaction was investigated at Lawrence Berkeley National Laboratory's 88-Inch Cyclotron facility. The experiment was aimed at the production of a superheavy element with $Z\ge 114$ by irradiating an actinide target with a beam heavier than ${}^{48}$Ca. Produced Lv ions were separated from the unwanted beam and nuclear reaction products using the Berkeley Gas-filled Separator and implanted into a newly commissioned focal plane detector system. Two decay chains were observed and assigned to the decay of ${}^{290}$Lv. The production cross section was measured to be ${\sigma }_{\mathrm{prod}}=0.44{(}_{-28}^{+58})$~pb at a center-of-target center-of-mass energy of 220(3)~MeV. This represents the first published measurement of the production of a superheavy element near the `Island-of-Stability', with a beam of ${}^{50}$Ti and is an essential precursor in the pursuit of searching for new elements beyond $Z=118$.

   nucl-exPRL(2024)·44 citations
2. 02*

   Equation of state of nuclear matter from collective flows and stopping in intermediate energy heavy-ion collisions

   Dan Cozma (IFIN-HH, Bucharest)🇷🇴

   The equation of state of nuclear matter, momentum dependence of the effective interaction and in-medium modification of elastic nucleon-nucleon cross-sections are studied by comparing theoretical predictions for stopping, directed and elliptic flows of protons and light clusters in intermediate energy heavy-ion collisions of beam energy between 150 and 800 MeV/nucleon to experimental data gathered by the FOPI Collaboration. A multivariate analysis that takes into account systematic uncertainties induced on model predictions by the coalescence afterburner leads to the following constraint for the equation of state at 68 percent confidence level: compressibility modulus of isospin symmetric matter $K_0=230_{-11}^{+9}$ MeV and slope of the symmetry energy $L=63_{-13}^{+10}$ MeV. The momentum dependence of the isoscalar potential is found to be similar to that of the empirical optical potential, with an effective isoscalar mass $m^{\ast }=0.695_{-0.018}^{+0.014}$. The isovector potential displays a momentum dependence corresponding to a positive neutron-proton effective mass difference $\Delta m_{np}^{\ast }=(0.17_{-0.09}^{+0.10})\delta$, close to the world average for this quantity. A suppression of elastic nucleon-nucleon cross-sections in symmetric nuclear matter at saturation by about 60$\%$ relative to vacuum values is deduced, in qualitative agreement with microscopical results. A strong dependence of the suppression factor on isospin asymmetry is evidenced, experimental data for isospin symmetric systems proving crucial for this last conclusion.

   ↳ nucl-thnucl-exPRC(2024)·16 citations
3. 03*

   On the sensitivity of nuclear clocks to new physics

   Andrea Caputo🇨🇭 · Doron Gazit🇮🇱 · Hans-Werner Hammer🇩🇪 · Joachim Kopp🇨🇭 · Gil Paz🇺🇸 · Gilad Perez🇮🇱 · Konstantin Springmann🇮🇱

   The recent demonstration of laser excitation of the $\approx 8$ eV isomeric state of Thorium-229 is a significant step towards a nuclear clock. The low excitation energy likely results from a cancellation between electromagnetic and strong contributions, which new physics can disrupt. In this Letter, we quantify the enhancement of a nuclear clock's sensitivity to new physics using a geometric model and a novel $d$-wave halo model of the nucleus that reproduces measured differences between Thorium-229 states. We find likely enhancements of order $10^4$ while a worst case scenario with enhancement $\ll 1$ is unlikely.

   ↳ hep-phnucl-exnucl-thPRC(2025)·35 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.