Nuclear Experiment·nucl-ex

Wed·Aug 19, 2026Wednesday·August 19, 2026

8 papers—3 primary·5 cross-listed

01
Accurate Charge Radius Measurement of $^{14}$ C Confronts \textit{Ab Initio} Theory
Kristian König🇩🇪 · Patrick Müller🇩🇪 · Tobias Gesser · Emily Burbach🇩🇪 · Stefano Gandolfi🇺🇸 · Matthias Heinz🇺🇸 · Phillip Imgram🇩🇪 · Alessandro Lovato🇺🇸 · Pieter Maris🇺🇸 · Takayuki Miyagi🇩🇪 · Wilfried Nörtershäuser🇩🇪 · Robert Roth🇩🇪 · Julien Spahn🇩🇪 · Achim Schwenk🇩🇪
Located at the neutron shell closure $N = 8$ , the long-lived radioactive isotope $^{14}\mathrm{C} $ plays a critical role in geochronology and nuclear structure studies. Despite its widespread use, the nuclear charge radius of $^{14}$ C has remained less precisely known compared to its stable counterpart $^{12}$ C. Here, we report a high-precision determination of the $^{14}$ C charge radius using collinear laser spectroscopy at the COALA setup at TU Darmstadt, improving upon the precision of previous muonic measurements by a factor $5$ and revealing a $1.9 σ$ discrepancy of combined uncertainty, indicating a likely underestimated uncertainty in the muonic determination. This measurement challenges state-of-the-art \textit{ab initio} nuclear theory calculations, including auxiliary field diffusion Monte Carlo, the valence-space in-medium similarity renormalization group, and the no-core shell model, augmented by neural-network techniques. With $^{12}$ C and $^{14}$ C now forming one of the most precisely characterized even-even isotope pairs, these results also enable improved QED tests.
nucl-exnucl-th0 citations
02
Determination of Tritium Content in D2 Gas and Heavy Water
Sandeep Puri · Noah D'Amico · Ian Jones · Sonny Alaniz · Andrew Gillespie · Cuikun Lin🇺🇸 · R. V. Duncan
A simple experimental method for the determination of tritium concentration in natural hydrogen and deuterium gas down to the femtomole level is described. Palladium and platinum catalysts were used to react hydrogen and oxygen, creating water that could be analyzed in a Revvity Quantulus GCT 6220. This analysis produced sub-femtomole detection limits of tritium present in hydrogen gas or heavy water. A contamination level of $\sim 1 femtomole/SL$ was found in the $D_{2}$ gas sample that was analyzed. A contamination level of $\sim 0.025 femtomole/SL$ , which is below the noise level of the Quantulus, was found in the standard hydrogen gas sample that was analyzed. The choice of palladium or platinum catalyst did not significantly affect the resulting tritium measurement. By showing that common $D_{2}$ samples can be contaminated with trace amounts of tritium orders of magnitude above natural abundance, this test demonstrates that a baseline tritium measurement for deuterium samples is highly important for determining the validity of results in nuclear fusion yield experiments.
nucl-ex0 citations
03
Revised $^{45}$ V( $p, γ$ ) $^{46}$ Cr reaction rate and its impact on the production of $^{44}$ Ti in core-collapse supernovae
R.S. Sidhu🇬🇧 · Y. Luo🇨🇳 · C. Sarma🇬🇧 · M. Wiescher🇺🇸 · X. Xu🇨🇳
The thermonuclear $^{45}$ V( $p, γ$ ) $^{46}$ Cr reaction is the primary leakage pathway from the $^{44}$ Ti-- $^{45}$ V quasi-equilibrium cluster during $α$ -rich freeze-out in core-collapse supernovae (CCSN), governing the final abundance of the $γ$ -ray-emitting isotope $^{44}$ Ti. A recent high-resolution $γ$ -ray study [C. Cousins \textit{et al.}, Phys. Rev. Lett. 136, 252701 (2026)] identified ten previously unknown low-spin proton-unbound states in $^{46}$ Cr, enabling the first experimentally constrained $^{45}$ V( $p, γ$ ) $^{46}$ Cr reaction rate using the AME2020 mass excess, $ME (^{46} Cr) = - 29472 (11)$ ~keV. Here, we adopt the four-fold more precise CSRe mass excess $ME (^{46} Cr) = - 29477.2 (2.6)$ ~keV [M.~Wang \textit{et al.}, Phys. Rev. C \textbf{106}, L051301 (2022)] to recalculate the reaction rate. Including proton capture on the ground and first two excited states of $^{45}$ V alongside new shell-model proton spectroscopic factors, we reduce mass-related rate uncertainties to a subdominant level. The revised rate is up to 69% higher than that of Cousins \textit{et al.} at $α$ -rich freeze-out temperatures ( $T ≃ 1.5$ -- $2$ ~GK). CCSN nucleosynthesis calculations show this revised rate increases the ejected $^{44}$ Ti yield by $\sim$ 26% in a $20 M_{⊙}$ model compared to The \textit{et al.} [ApJ \textbf{504}, 500 (1998)], while causing negligible changes for the SN~1987A trajectory. We demonstrate that $^{44}$ Ti production sensitivity is dictated by the ejecta electron fraction ( $Y_{e}$ ): the reaction significantly affects proton-rich ejecta ( $Y_{e} \approx 0.50$ ) but has little impact on neutron-rich ejecta ( $Y_{e} \approx 0.496$ ), where lower free-proton abundances suppress reaction flow. This reconciles conflicting results from past sensitivity studies.
nucl-exastro-ph.HEastro-ph.SRnucl-th0 citations
04
The high-energy behavior of tree-level scattering in finite-temperature QCD: estimates of theoretical systematic uncertainty in jet-medium Monte Carlo simulations
Lukas Opitz🇨🇦 · Hemanth Regi🇨🇦 · Gojko Vujanovic🇨🇦
We examine the behavior of tree-level scattering in thermal QCD at high energies and find significant deviations away from the commonly used approximations [Phys. Rev. D 44, 1298 (1991), Phys. Rev. D 44, R2625 (1991), Phys. Rev. D.77, 014015 (2008), Phys. Rev. D. 77.114017 (2008)]. These deviations in the scattering rate also affect jet-medium transport coefficients at the partonic level, leading to a different kinematic dependence of the transverse momentum broadening per unit length $q^$ . As scattering rates and $q^$ are used by large-scale Monte Carlo simulations of jets in the quark-gluon plasma (QGP), such as [Phys. Rev. C 111,054913 (2025)], current constraints on $q^$ are biased owing to the approximations used therein. Besides theoretically improving $q^$ , the differences between the $q^$ herein and the approximate $q^$ used in jet Monte Carlo simulations are used to construct a theoretical systematic uncertainty, which in turn can be employed to devise a covariance matrix for $q^$ and enables updating the uncertainty bands on $q^$ obtained by Bayesian analysis.
↳ hep-phnucl-exnucl-th0 citations
05
Closed-form expressions for tree-level gluon-gluon scattering: a framework for obtaining theoretical systematic uncertainties for jet-medium Monte Carlo simulations
Lukas Opitz🇨🇦 · Hemanth Regi🇨🇦 · Gojko Vujanovic🇨🇦
Modern Bayesian theory-to-data comparisons for jet-medium interactions, such as [Phys. Rev. C 111,054913 (2025)], are lacking the careful accounting of theoretical systematic uncertainties included within their uncertainty budget. Tree-level gluon-gluon scattering is revisited to establish a framework capable of quantifying theoretical systematic uncertainties to be used in Bayesian jet-medium constraints. The behavior of tree-level scattering in thermal QCD is examined in detail, finding deviations away from the commonly used approximations. Deviations in the scattering rate affect jet-medium transport coefficients at the partonic level, leading to a more intricate kinematic dependence for $q^$ and $e^$ than, say, the well-known logarithmic behavior. These deviations away from well-known behavior are used to estimate theoretical systematic uncertainties in Bayesian analysis.
↳ hep-phnucl-exnucl-th0 citations
06
Generative artificial intelligence for reconstructing neutron-star matter
Julia Yu. Panteleeva🇩🇪 · Herzallah Alharazin🇩🇪 · Evgeny Epelbaum🇩🇪
Neutron-star cores hold the only known matter in the universe that is simultaneously cold and strongly interacting, compressed beyond nuclear density into a state of unknown composition. The equation of state links stellar masses, radii and tidal deformabilities to this regime, but recovering this key quantity from sparse observations is an ill-posed inverse problem. Existing analyses bury a prior in a fixed functional form, unevenly weighting admissible solutions and biasing the result. We reconstruct the equation of state with a denoising diffusion model that keeps prior, physics and data separate: it learns an inspectable, physically motivated prior anchored to first-principles nuclear theory, while perturbative-QCD and astrophysical constraints are imposed exactly. Future measurements therefore will update the posterior by reweighting alone, without retraining or resampling. The inferred radius of 12.6 km and tidal deformability of 469 at 1.4 solar masses reproduce Gaussian-process and heavy-ion-informed inferences despite a far broader prior. We find near-conformal but still stiff matter in the heaviest stars, consistent with a gradual hadron-quark crossover and disfavouring a strong first-order phase transition. More broadly, coupling a learned prior to exactly enforced physics establishes a template for ill-posed inverse problems where theory and data constrain different regions.
↳ nucl-thastro-ph.HEastro-ph.IMhep-ph+10 citations
07
Bound-state spectra of $χ_{c J}$ in finite nuclei and the universal pattern of mass levels
Tian-Le Gao🇨🇳 · Ze-Hua Zhang🇨🇳 · Xiang Liu🇨🇳
In this work, we investigate possible $χ_{c J}$ --nuclear bound states with $J = 0, 1, 2$ using in-medium mass shifts generated by virtual $D^{(*)} D ˉ^{(*)}$ loops within an unquenched framework. The resulting $χ_{c J}$ --nucleus potentials are constructed in the local density approximation, and the bound state spectra are calculated for $^{12} C$ , $^{16} O$ , $^{40} Ca$ , $^{90} Zr$ , $^{197} Au$ , and $^{208} Pb$ . Bound states are obtained for all systems considered. The $χ_{c 0} (1 P)$ and $χ_{c 1} (1 P)$ spectra are nearly degenerate, whereas the larger in-medium mass shift of $χ_{c 2} (1 P)$ leads to deeper binding. Although the absolute bound state energies depend appreciably on the cutoff parameter, the energy differences relative to the $1 s$ level are considerably less sensitive to it and exhibit a regular pattern that decreases approximately as $A^{- 2/3}$ with increasing nuclear mass number. A cosh-type potential with a common nuclear geometry provides a compact description of these spectra. The predicted bound-state structures and level-spacing systematics could be investigated in future high-statistics near-threshold photoproduction experiments at the upgraded JLab facility.
↳ hep-phhep-exnucl-exnucl-th0 citations
08
Symbolic Regression for Interpretable Emulation of Proton Collective Flow in Intermediate-Energy Heavy-Ion Collisions
Nicholas Cox🇺🇸 · Xavier Grundler🇺🇸 · Bao-An Li🇺🇸
Symbolic regression provides an interpretable machine-learning approach for constructing explicit analytic relations between physical inputs and observables. In this work, we develop symbolic-regression emulators for the isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model and compare their performance with deep neural network (DNN) emulators. Using the same transport-model data employed in our previous emulator studies, we show that symbolic regression can reproduce the proton mid-rapidity slope $F_{1}$ of transverse flow $v_{1}$ and elliptic flow $v_{2}$ with accuracy comparable to that of DNNs, while providing explicit analytic expressions and substantially faster prediction once trained. We further demonstrate the use of symbolic regression in the reverse direction by constructing analytic relations that predict the in-medium nucleon-nucleon cross-section modification factor $X$ from the flow observables. Although the symbolic-regression models require substantially longer training times and exhibit greater run-to-run variation than DNNs, their analytic form and rapid evaluation make them promising tools for future transport-model sensitivity and uncertainty analyses.
↳ nucl-thnucl-ex0 citations

Affiliations

first authorsco-authorsvia INSPIRE