Fri·Dec 19, 2025Friday·December 19, 2025

1. 01*

   A pathway towards decentralized studies of radioactive post-lead elements and their applications in beyond standard model physics

   Moritz Pascal Reiter🇬🇧 · Kriti Mahajan · Meetika Narang🇮🇳 · Carsten Zuelch · Timo Dickel🇩🇪 · Daler Amanbayev · Robert Berger🇩🇪 · Julian Bergmann🇩🇪 · Agnieszka Bukowicka · Mariam Fadel · Tayemar Fowler-Davies · Zhuang Ge and 12 other authors

   Molecules have proven to be sensitive tools for studying physics beyond the standard model, with heavy and deformed nuclei offering decisive sensitivity to parity- and time-reversal-violating effects. However, almost all elements beyond lead, occupying the 6p~to~5f atomic orbitals, lack stable isotopes, hence molecules containing them are referred to as radioactive molecules. Among those, radium monofluoride has seen particular interest, but to date, research on radioactive molecules has mainly been limited to large-scale nuclear facilities. Here, we present a scheme that allows efficient and fast harvest of radioactive ions (including short-lived Ra), and show ion gas-phase reaction studies of singly and doubly charged Ra, Po, and Pb ions with SF${}_6$ gas inside an ion trap. Our results show that the chemical reaction rate of Ra${}^{+}$ is in line with trends of other alkaline earth elements, further support by quantum chemical computations. The reaction Ra${}^{2+}$ + SF${}_6$ $\to$ RaF${}^{+}$ + SF${}_5^{+}$ achieves an almost unity conversion efficiency, making it particularly suitable for the application for studies in physics beyond the standard model. The scheme enables future decentralized research avenues with short-lived radioactive molecules for fundamental physics research at laboratories without the need for local nuclear reactors or accelerators.

   nucl-ex1 citation
2. 02*

   Comparing invariant-mass spectroscopy of 8B with ab initio predictions

   R.J. Charity🇺🇸 · G.H. Sargsyan🇺🇸 · K.D. Launey🇺🇸 · T.B. Webb · K.W. Brown🇺🇸 · L.G. Sobotka🇺🇸

   Levels in 8B have been investigated experimentally using the invariant-mass technique and compared to ab initio calculations. Data sets obtained using E/A=69-MeV 9C and 13O beams on a Be target have been further analyzed to extend the level scheme of 8B for Ex<10 MeV. New levels were observed in the 2p+6Li, p+3He+alpha, and the p+7Be+gamma exit channels. Momentum correlations between the decay fragments were also investigated in order to deduce the decay pathways and whether the decays are prompt or sequential. This nucleus and its mirror were also investigated in the ab initio symmetry-adapted no-core shell model. Correspondence between the newly observed and predicted levels were made based on the level energy and the decay modes. For positive parity levels with J<=3, all predicted levels can be connected to an experimental counter part (as least tentatively) for Ex<8.4 MeV.

   nucl-exnucl-thPRC(2026)·2 citations
3. 03*

   Measurement of Light Yield Response of Gd-compatible Water-based Liquid Scintillator with the Brookhaven 1-ton testbed

   S. Gwon🇰🇷 · M. Askins🇺🇸 · D.M. Asner🇺🇸 · A. Baldoni🇺🇸 · D.F. Cowen🇺🇸 · R. Diaz Prerez🇺🇸 · M.V. Diwan🇺🇸 · S. Gokhale🇺🇸 · S. Hans🇺🇸 · P. Kumar🇺🇸 · G. Lawley🇺🇸 · S. Linden🇺🇸 and 10 other authors

   The Water-based Liquid Scintillator (WbLS) enables hybrid detection by combining scintillation and Cherenkov signals, providing superior event reconstruction capabilities compared to conventional neutrino detectors. We measured the light yield of Gd-compatible WbLS at varying concentrations from 0.35\% to 1\% by mass, using cosmic-ray muons in a 1-ton scale detector at BNL. The light yield is measured as (69.16 $\pm$ 6.92) ph / MeV at 0.35\% concentration, which increased to (87.32 $\pm$ 8.73) ph / MeV at 1\%. These results establish a quantitative basis for optimizing future WbLS-based detectors in neutrino physics.

   ↳ physics.ins-dethep-exnucl-exPRD(2026)·3 citations
4. 04*

   Hadron Physics Opportunities at FAIR

   J. G. Messchendorp🇩🇪 · F. Nerling🇩🇪 · P. Achenbach🇺🇸 · J. Aichelin🇫🇷 · M. Albaladejo🇪🇸 · L. An🇨🇳 · K. Aoki🇯🇵 · G. Appagere🇸🇪 · V. Baru🇩🇪 · M. Bashkanov🇬🇧 · A. Bauswein🇩🇪 · A. Belias🇩🇪 and 94 other authors

   This White Paper outlines a coordinated, decade-spanning programme of hadron and QCD studies anchored at the GSI/FAIR accelerator complex. Profiting from intense deuteron, proton and pion beams coupled with high-rate capable detectors and an international theory effort, the initiative addresses fundamental questions related to the strong interaction featuring confinement and dynamical mass generation. This includes our understanding of hadron-hadron interactions and the composition of hadrons through mapping the baryon and meson spectra, including exotic states, and quantifying hadron structure. This interdisciplinary research connects topics in the fields of nuclear, heavy-ion, and (nuclear) astro (particle) physics, linking, for example, terrestrial data to constraints on neutron star structure. A phased roadmap with SIS100 accelerator start-up and envisaged detector upgrades will yield precision cross sections, transition form factors, in-medium spectral functions, and validated theory inputs. Synergies with external programmes at international accelerator facilities worldwide are anticipated. The programme is expected to deliver decisive advances in our understanding of non-perturbative (strong) QCD and astrophysics, and high-rate detector and data-science technology.

   ↳ hep-exhep-thnucl-exnucl-th20 citations
5. 05*

   Unveiling Light-Quark Yukawa Flavor Structure via Dihadron Fragmentation at Lepton Colliders

   Qing-Hong Cao🇨🇳 · Xin-Kai Wen🇨🇳 · Bin Yan🇨🇳 · Shu-Tao Zhang🇨🇳

   Directly probing light-quark Yukawa couplings and their flavor structure remains a major challenge due to their smallness and overwhelming QCD backgrounds. In this Letter, we propose a theoretical framework to access these couplings at lepton colliders through transverse spin dependent azimuthal modulations in dihadron fragmentation. These modulations arise from the interference between Higgs mediated and standard model amplitudes in $e^{-}{e}^{+}\to q\bar{q}Z$, producing angular structures that are linearly sensitive to the Yukawa couplings $y_q$, in contrast to conventional observables that scale as $y_q^2$. By combining channels with an identified accompanying single hadron, $h^{\prime }={\pi }^{\pm },K^{\pm }$, and $p/\bar{p}$, this approach cleanly disentangles the up- and down-quark Yukawa contributions, yielding typical limits at the $\mathcal{O}(10^{-4}\sim 10^{-3})$ level and establishing fragmentation dynamics as a novel and complementary probe of the Higgs flavor structure.

   ↳ hep-phhep-exnucl-exnucl-thPRL(2026)·6 citations
6. 06*

   Applying Gaussian Mixture Models to Track Reconstruction in Inelastic Scattering Experiments with Active Targets

   A. Arokiaraj🇧🇪 · M.B. Latif🇳🇬 · R. Raabe🇧🇪 · D. Thisse🇫🇷 · M. Vandebrouck🇫🇷

   Active targets such as ACTAR TPC are well suited for studying giant resonances in unstable nuclei via inelastic scattering in inverse kinematics. A key challenge in such measurements is the detection of low-energy ejectiles emitted at small angles relative to the beam direction. Accurate reconstruction of these tracks is essential for disentangling different resonance modes. Probabilistic models such as the Gaussian Mixture Model (GMM) are particularly effective in capturing the complex covariance structures characteristic of the beam-recoil interface in narrow-angle events. In this work, we present a track reconstruction approach based on the GMM, specifically designed for inelastic scattering experiments with active targets. Special emphasis is placed on the treatment of low-energy tracks. The proposed method is demonstrated on simulated data of the ${}^{58}\mathrm{Ni}(\alpha ,{\alpha }^{\prime }{)}^{58}\mathrm{Ni}$ reaction at an incident energy of $E=49$~MeV/nucleon, generated under conditions representative of the experiment carried out at GANIL for the same reaction.

   ↳ physics.data-annucl-exNucl.Instrum.Meth.A(2026)·0 citations
7. 07*

   The anomalous magnetic moment of the muon: status and perspectives

   David W. Hertzog🇺🇸 · Martin Hoferichter🇨🇭

   We review the status of the anomalous magnetic moment of the muon as a precision probe of physics beyond the Standard Model (SM) after the release of the final results from the Fermi National Accelerator Laboratory (FNAL) Muon $g-2$ experiment and the second White Paper of the Muon $g-2$ Theory Initiative. While the SM prediction requires further improvements by a factor of four to fully leverage the sensitivity achieved in experiment, the FNAL measurement will set the standard for many years to come, and we discuss a variety of features of the experimental campaign that made this achievement possible. In going forward, we discuss current efforts to improve the SM prediction, and imagine how an experiment would have to be devised to surpass 124 ppb in precision.

   ↳ hep-phhep-exhep-latnucl-ex+114 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.