Nuclear Theory·nucl-th

Monday·March 17, 2025

10 papers—4 primary·6 cross-listed

05
[Submitted on 13 Mar 2025] (cross-list from hep-ph)
Exclusive photon-fusion production of even-spin resonances and exotic QED atoms in high-energy hadron collisions
David d'Enterria🇨🇭 · Karen Kang🇺🇸
The cross sections for the single exclusive production of (pseudo)scalar and (pseudo)tensor hadrons, as well as of even-spin QED bound states formed by pairs of opposite-charge leptons or hadrons, are estimated for photon-fusion processes in ultraperipheral collisions (UPCs) of proton-proton, proton-nucleus, and nucleus-nucleus at the RHIC, LHC and FCC colliders, as well as in proton-air interactions at the highest energies reached by cosmic-rays impinging on Earth. The UPC cross sections are computed in the equivalent photon approximation with realistic photon fluxes from the charged form factors of proton, lead, gold, and nitrogen ions. The production of four types of even-spin systems are considered: quarkonium (spin-0,2,4 meson bound states, from the lightest $π^{0}$ meson up to toponium), exotic hadrons (including candidate multiquark states), leptonium (positronium, dimuonium, and ditauonium), as well as mesonium (pionium, kaonium, D-onium, and B-onium) and baryonium (notably, protonium) QED atoms. The expected yields at the different colliders are presented for about 50 such even-spin composite resonances, for which the ALICE and LHCb experiments have potential reconstruction capabilities at the LHC. The impact of the diphoton decays of such even-spin states is also discussed as resonant backgrounds in the measurement of light-by-light scattering ( $γ γ \to γ γ$ ) over $m_{γ γ} = 0.1$ --15 GeV in PbPb UPCs at the LHC.
Comments:
39 pages, 13 figures. Minor mods. Matches published PRD version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2503.10952 [pdf]
PRD(2025)·16 citations
06
[Submitted on 14 Mar 2025] (cross-list from nucl-th)
Further exploration of binding energy residuals using machine learning and the development of a composite ensemble model
I. Bentley · J. Tedder · M. Gebran · A. Paul
This paper describes the development of the Four Model Tree Ensemble (FMTE). The FMTE is a composite of machine learning models trained on experimental binding energies from the Atomic Mass Evaluation (AME) 2012. The FMTE predicts binding energy values for all nuclei with N > 7 and Z > 7 from AME 2020 with a standard deviation of 76 keV and a mean average deviation of 34 keV. The FMTE model was developed by combining three new models with one prior model. The new models presented here have been trained on binding energy residuals from mass models using four machine learning approaches. The models presented in this work leverage shape parameters along with other physical features. We have determined the preferred machine learning approach for binding energy residuals is the least-squares boosted ensemble of trees. This approach appears to have a superior ability to both interpolate and extrapolate binding energy residuals. A comparison with the masses of isotopes that were not measured previously and a discussion of extrapolations approaching the neutron drip line have been included.
Comments:
Phys. Rev. C - Accepted 17 June, 2025
Subjects:
Nuclear Theory (nucl-th); Machine Learning (cs.LG)
arXiv:
2503.11066 [pdf]
PRC(2025)·5 citations
07
[Submitted on 14 Mar 2025] (cross-list from hep-ph)
Gravitational form factors in the perturbative limit
Qin-Tao Song🇨🇳 · O. V. Teryaev🇷🇺 · Shinsuke Yoshida🇨🇳
Generalized distribution amplitudes (GDAs) have attracted significant attention in recent years due to their connection with the energy-momentum tensor (EMT) form factors (FFs). The GDAs can be experimentally accessed through the study of amplitudes in $γ^{*} γ \to M_{1} M_{2}$ and $γ^{*} \to M_{1} M_{2} γ$ , where $M_{1} M_{2}$ is a pseudoscalar meson pair such as $π η$ and $η η^{'}$ . In this work, we calculate these amplitudes in the perturbative limit and express the extracted $M_{1} M_{2}$ GDAs in terms of meson distribution amplitudes that have been constrained by the previous experiments. Our explicit calculation verifies the existence of a new EMT FF that violates the conservation law of EMT when the hadronic matrix element of the EMT operator is considered separately for each quark flavor. In addition, our result shows that the $M_{1} M_{2}$ GDAs are identical in $γ^{*} γ \to M_{1} M_{2}$ and $γ^{*} \to M_{1} M_{2} γ$ , which confirms the universality of GDAs in the perturbative limit. In the future, the GDAs and the EMT FFs studied in this paper can be probed at Belle II. Our study enhances the accessibility to the $P$ -wave GDAs in $γ^{*} γ \to M_{1} M_{2}$ and $γ^{*} \to M_{1} M_{2} γ$ , and provides a promising approach for searching for exotic hybrid mesons in future experiments.
Comments:
12 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2503.11316 [pdf]
PLB(2025)·9 citations
08
[Submitted on 14 Mar 2025] (cross-list from cond-mat.mtrl-sci)
A spinless crystal for a high-performance solid-state $^{229}$ Th nuclear clock
Harry W. T. Morgan · James E. S. Terhune · Ricky Elwell · Hoang Bao Tran Tan · Udeshika C. Perera · Andrei Derevianko · Eric R. Hudson · Anastassia N. Alexandrova
Solid-state $^{229}$ Th nuclear clocks require a host material whose band gap is larger than the 8.4 eV nuclear transition energy. As such, excitation of the $^{229}$ Th nuclear state has so far only been demonstrated in metal fluorides, specifically CaF $_{2}$ , LiSrAlF $_{6}$ , and ThF $_{4}$ , where the large electronegativity of the halogen leads to sufficient band gaps. However, it is expected that the nuclear magnetic moment of the fluorine gives rise to a leading order broadening mechanism that limits the clock stability. Here, we use concepts of molecular design to identify a polyatomic anion, SO $_{4}^{2 -}$ , that is both nuclear spin free and of sufficient electron affinity to result in a high band gap metal sulfate system. Using state-of-the-art calculations, we find that the band gap of Th(SO $_{4}$ ) $_{2}$ is approximately 9 eV, large enough for direct laser excitation of $^{229}$ Th. Low concentrations of $^{229}$ Th in the otherwise spinless $^{232}$ Th(SO $_{4}$ ) $_{2}$ crystal mitigate $^{229}$ Th- $^{229}$ Th interactions. Furthermore, the introduction of $^{229}$ Th does not modify the material band gap nor introduce electronic states associated with nuclear quenching. By removing one of the primary sources of nuclear line broadening in the crystal, the nuclear magnetic dipole-dipole interaction, a nuclear clock with instability as low as $σ = 4.6 \times 1 0^{- 23} / τ$ , where $τ$ is the averaging time, may be realized. This is roughly six orders of magnitude lower than previously thought possible.
Comments:
7 pages of main text and references, 3 pages of supporting information. 2 figures
Subjects:
cond-mat.mtrl-sci (cond-mat.mtrl-sci); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph); physics.optics (physics.optics)
arXiv:
2503.11374 [pdf]
5 citations
09
[Submitted on 14 Mar 2025] (cross-list from hep-ph)
Identified Hadron Production at Hadron Colliders in Next-to-Next-to-Leading-Order QCD
Michał Czakon🇩🇪 · Terry Generet🇬🇧 · Alexander Mitov🇬🇧 · Rene Poncelet🇵🇱
In this work we calculate for the first time the next-to-next-to leading order (NNLO) QCD corrections to identified hadron production at hadron colliders. The inclusion of the NNLO correction has an important impact on all observables considered in this work. Higher order corrections reduce scale uncertainty and in almost all cases are moderate. Overall, good perturbative convergence is observed across kinematics and observables. The uncertainty due to missing higher orders is relatively small and, in many cases, smaller than the experimental uncertainty. The largest source of theoretical uncertainty at present is from the knowledge of the non-perturbative parton-to-hadron fragmentation functions (FF), which dwarfs the scale uncertainty in most kinematic ranges. The inclusion of NNLO corrections demonstrates the precision studies potential of this class of observables. To fully realize this potential, however, a new generation of improved fragmentation functions may be needed. The results of the present work will enable global fits of FF with NNLO precision.
Comments:
Published version, 6 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2503.11489 [pdf]
PRL(2025)·17 citations
10
[Submitted on 14 Mar 2025] (cross-list from cond-mat.stat-mech)
Exact Results for the Ericson Transition in Stochastic Quantum Scattering and Experimental Validation
Simon Köhnes · Jiongning Che · Barbara Dietz · Thomas Guhr
At lower energies, the resonances in scattering experiments are often isolated. The crucial parameter is the ratio of average resonance width and average mean level spacing. Towards larger energies, this parameter grows, because the resonances overlap. Eventually the cross-section becomes a random function and the scattering matrix elements follow a universal Gaussian distribution. For more than sixty years, this Ericson transition awaits a concise analytical treatment. We provide a complete solution within the Heidelberg approach which provides a full-fledged model of the scattering process. As a side result, we obtain explicit formulae for the moments of the distributions. We compare with microwave experiments.
Comments:
9 pages, 4 figures
Subjects:
Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
2503.11516 [pdf]
1 citation

Affiliations

first authorsco-authorsvia INSPIRE

Exclusive photon-fusion production of even-spin resonances and exotic QED atoms in high-energy hadron collisions

Further exploration of binding energy residuals using machine learning and the development of a composite ensemble model

Gravitational form factors in the perturbative limit

A spinless crystal for a high-performance solid-state 229Th nuclear clock

Identified Hadron Production at Hadron Colliders in Next-to-Next-to-Leading-Order QCD

Exact Results for the Ericson Transition in Stochastic Quantum Scattering and Experimental Validation

Affiliations

A spinless crystal for a high-performance solid-state $^{229}$ Th nuclear clock