Wed·Mar 19, 2025Wednesday·March 19, 2025

1. 01*

   Collinear laser spectroscopy on neutron-rich actinium isotopes

   Ruohong Li🇺🇸 · Andrea Teigelhöfer🇨🇦 · Jiguang Li · Jacek Bieroń🇵🇱 · András Gácsbaranyi · Jake Johnson · Per Jönsson · Victoria Karner · Mingxuan Ma · Martin Radulov · Mathias Roman · Monika Stachura · Jens Lassen🇨🇦

   High-resolution collinear laser spectroscopy of neutron-rich actinium has been performed at TRIUMF's isotope separator and accelerator facility ISAC. By probing the $7s^2{}^1{S}_0$ $\to$ $6d7p{}^1{P}_1$ ionic transition, the hyperfine structures and optical isotope shifts in ${}^{225,226,228,229}$Ac${}^{+}$ have been measured. This allows precise determinations of the changes in mean-square charge radii, magnetic dipole moments, and electric quadrupole moments of these actinium isotopes. The improved precision of charge radii and magnetic moments clears the ambiguity in the odd-even staggering from previous studies. The electric quadrupole moments of ${}^{225,226,228,229}$Ac are determined for the first time.

   nucl-exphysics.atom-phPRC(2025)·1 citation
2. 02*

   Superallowed $0^{+}\to 0^{+}$ $\beta$ decay studies at GANIL and upcoming opportunities with DESIR and S${}^3$-LEB

   B. M. Rebeiro🇫🇷 · J.-C. Thomas🇫🇷 · B. Blank🇫🇷

   Corrected transition rates ($\mathcal{F}{t}^{0^{+}\to 0^{+}}$) of $0^{+}\to 0^{+}$ superallowed $\beta$ decays currently give the most precise value of $V_{ud}$, the dominant term of the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix. By setting stringent constrains on the CKM unitarity, these decays allow probing physics beyond the Standard Model in the electroweak sector. A recent global reevaluation of the $\mathcal{F}{t}^{0^{+}\to 0^{+}}$ values has indicated a violation of CKM unitarity prompting reassessment of the theoretical radiative and isospin symmetry breaking corrections applied on the experimental transition rates $ft$. In this article we briefly discuss this current situation and the experimental program at GANIL geared towards constraining isospin symmetry breaking corrections. We conclude by presenting the opportunities that will be available at DESIR and S${}^3$-LEB, the upcoming low-energy radioactive ion beam facilities at GANIL.

   nucl-exhep-phPhys.Scripta(2025)·1 citation
3. 03*

   Characterizing the Experiment for Calibration with Uranium (Excalibur) Neutron Source for Use in Warhead Verification

   Jihye Jeon · Erik P. Gilson · Michael Hepler · Alexander Glaser · Robert J. Goldston

   Neutron sources can play a variety of roles in warhead verification. For transmission radiography, a source of directed high energy neutrons is required, while for applications to detect fissile isotopes, sub-MeV neutrons are preferred. The Excalibur (Experiment for Calibration with Uranium) neutron source has been built and used in a variety of verification-related experiments. Excalibur is based on a commercial deuterium-tritium neutron generator specified and measured to be capable of producing 14 MeV neutrons at rates of up to 8.2$\times$10${}^8$ neutrons/s. The generator is enclosed in a carbon-steel 32${}^{\prime \prime }$ diameter, 23.62${}^{\prime \prime }$ high carbon-steel cylinder that moderates the mean neutron energy to under 500 keV. This, in turn, is encased in 5\%-borated polyethylene such that the entire assembly is a 48${}^{\prime \prime }$$\times$48${}^{\prime \prime }$ box that is 30${}^{\prime \prime }$ tall. For radiographic applications, a narrow, tapered channel in the steel and polyethylene allows 14 MeV neutrons to stream directly from the generator to a test object. Its collimating capability is demonstrated by measuring the neutron flux profile. In the moderated mode of operation, the generator is fully enclosed in the steel, but a large section of the polyethylene is removed, providing a flux of sub-MeV neutrons from a wide range of angles. Neutron angular and spectral measurements using both a nested neutron spectrometer and a commercial liquid scintillator coupled with a ${}^3$He detector show the expected softer neutron spectrum in moderated mode in good agreement with MCNP6 calculations. The gamma-ray spectrum from Excalibur is also in good agreement with MCNP modeling. Based on these findings, the future application of Excalibur in its two configurations is discussed.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2026)·0 citations
4. 04*

   Double parton interactions initiated by direct photons in $\gamma p$ and $\gamma A$ collisions revisited

   B. Blok (Technion)🇮🇱 · R. Segev (Technion)🇮🇱

   We consider the double parton scattering (DPS) initiated by direct photons in $\gamma p$ and $\gamma A$ collisions. We extend the previously known results for photoproduction to the case of electroproduction with nonzero photon virtuality $Q^2$, and then consider the DPS for both photo and electroproduction for HERA and IEC ( electron ion collider) kinematics. The number of DPS events at IEC is shown to be of the same order as in HERA and is even larger, with increase in luminocity compensating the decrease of the center of mass energy.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2026)·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.