Abstract In this work, new measurements of absolute x-ray yields for several transitions in kaonic copper and, for the first time, in kaonic fluorine are reported. The data were collected by the SIDDHARTA-2 collaboration at the DA Φ NE collider using a novel room-temperature cadmium zinc telluride (CZT) detection system. Detection efficiencies were evaluated through a dedicated Geant4 Monte Carlo simulation of the full experimental setup, enabling the extraction of absolute yields per stopped kaon. The measured yields exhibit a systematic dependence on the principal quantum number, reflecting the interplay between radiative transitions, Auger de-excitation, and strong-interaction-induced nuclear capture. In kaonic fluorine, a suppression of the 4 → 3 transition yield relative to higher- n transitions is observed, providing evidence for the onset of strong-interaction effects already at the n = 4 level. From this behaviour, a conservative lower limit on the corresponding strong-interaction width is derived. These results provide new quantitative constraints for cascade models of exotic atoms and extend experimental access to intermediate atomic levels where strong-interaction effects are not directly observable via level shifts and widths. They also establish CZT-based detection as a powerful and versatile approach for high-resolution x-ray spectroscopy of kaonic atoms in collider environments.
In this mini-review, we provide a brief status report on investigating spin transport phenomena in intermediate-energy heavy-ion collisions by simulating solutions of the spin- and isospin-dependent Boltzmann-Uehling-Uhlenbeck (SIBUU) transport equation using the test-particle method. We outline the physics foundation and technical approach, summarize our main results and identify key challenges in further studying spin transport within the SIBUU framework. As examples, we show how the global and local spin polarizations of nucleons, the spin splitting of nucleon collective flows as well as flows of light clusters at different spin states can be used to explore interesting new physics associated with the nuclear spin-orbit potential in dense neutron-rich medium. The spin-orbit potential and the rigorous angular momentum conservation are also shown to affect spin-averaged observables. Hopefully the new findings and challenges identified here will stimulate further studies both theoretically and experimentally on spin transport in intermediate-energy heavy-ion collisions.
Abstract Two-particle correlations in pseudorapidity and azimuthal angle are studied for all charged, likesign positive, like-sign negative, and unlike-sign charged-particle pairs in inelastic proton-proton collisions at CERN SPS beam momenta p beam = 20, 31, 40, 80, and 158 GeV/c ( √ s ≃ 6.3-17.3 GeV). The calculations are performed with SMASH 3.3 and compared with NA61/SHINE correlation data. The default SMASH string treatment is contrasted with an updated SMASH-Pythia implementation in which the primary string-producing pp interaction is generated with embedded Pythia 8.316, including SoftQCD production, multiparton interactions, beam-remnant construction, primordial transverse momentum, and retuned Lund fragmentation parameters. A post-decay BE32-inspired low-Q identical-pion pair correction is also applied at the correlation analysis level to test the sensitivity to Bose-Einstein enhancement.The default SMASH calculation captures some qualitative features of the data, but underestimates the short-range near-side correlations and overestimates the large-∆η or long-range components, especially at lower SPS beam momenta. The updated SMASH-Pythia framework substantially improves the all-charged C(∆η) and C(∆ϕ) projections over the full energy range, showing that the primary production stage and fragmentation topology strongly affect the accepted pair structure. The remaining discrepancy is localized mainly at small ∆η and small ∆ϕ. For like-sign pairs, the BE32-inspired correction largely removes the near-side deficit in the ++ channel and significantly improves the --channel, although a smaller deficit remains at lower SPS energies. The unlike-sign channel is almost insensitive to the BE correction and is generally well described, confirming that the correction is charge selective rather than a global rescaling.These results provide a data-constrained pp baseline within SMASH for correlation studies at SPS energies and show that both an improved microscopic production stage and a controlled low-Q identical-pion correction are needed to describe the short-and long-range structure of chargedparticle correlations.
Two-proton radioactivity provides a direct probe of nucleonic correlations in proton-unbound nuclei. To elucidate how these correlations differ among dripline systems, we investigate the asymptotic proton-proton correlations of the known medium-mass two-proton emitters 45Fe, 48Ni, 54Zn, and 67Kr within the three-body Gamow coupled-channel framework. By extracting the final-state information from the transition matrix, we obtain asymptotic observables for long-lived emitters without explicit propagation to very large times and distances. The calculated correlations display clear nucleus-dependent differences linked to the underlying valence-proton configurations and deformation effects. In particular, the comparison between internal densities and asymptotic observables demonstrates that the long-range correlation pattern is governed not only by the inner structure, but also by channel selection during tunneling and by the long-range Coulomb interaction.
Abstract The medically relevant gallium radionuclides 66 Ga, 67 Ga, and 68 Ga are increasingly demanded for PET imaging and radiopharmaceutical development, yet their alpha-induced production routes often suffer from model-to-data discrepancies and practical trade-offs between yield and radionuclidic impurities. In this work, I present a reaction-specific TALYS-2.0 calibration and decision framework for alpha-irradiation of Cu, Zn, and Ga targets, where key nuclear inputs (level-density, alpha-optical model, and pre-equilibrium options) are screened in a full-factorial scheme and ranked against EXFOR measurements using combined statistical and shape-agreement criteria. The selected best-fit models are then used to generate validated excitation functions, estimate thick-target yields, and determine practical optimum energy windows that balance productivity with impurity suppression. To further enhance radionuclidic purity under realistic operation, post-irradiation cooling time is optimized through TALYS/ISOTOPIA activity-decay calculations, enabling time-dependent purification strategies. The analysis indicates that several routes can approach ∼100% purity for 66 Ga and 67 Ga at suitably selected cooling times while maintaining AOCT/AEOB typically above 50%, whereas most 68 Ga routes attain maximum purity at or near end-of-bombardment due to its short half-life. Overall, the study delivers a validated, data-benchmarked set of TALYS model selections and actionable guidance on target choice, energy window, and cooling time to support medium-energy medical cyclotron production of gallium radionuclides.
Abstract Double-electron capture in 152 Gd was searched for over 1336 h with a 286 g GAGG:Ce crystal scintillator at the Gran Sasso underground laboratory of the INFN (Italy). New, improved by four orders of magnitude, limit on the near-resonant 0 ν 2EC capture in 152 Gd was set as lim T 1 / 2 = 8.1 × 1 0 16 year at 90% C.L. Moreover, for the first time, a laboratory experiment has established a lower limit on the half-life of the allowed 2 ν KL process in the nuclide, with lim T 1 / 2 = 9.2 × 1 0 16 year at 90% C.L.
Nuclear potentials governing the interactions between protons and various target nuclei are computed through the application of the single folding model within the R3Y (relativistic) and M3Y (non-relativistic) effective potentials. Fusion barrier heights and positions for proton projectiles interacting with 25 different target nuclei, spanning mass numbers from 51 to 233, are systematically investigated. The relativistic approach employs NL3* (non-linear) and DD-ME2 (density-dependent) parameterizations, while the non-relativistic uses BSk14, SLy4, SLy5, SLy6, and SLy7 Skyrme sets. The impact of non-linearity and density dependence on potentials and barrier parameters is analyzed. These results are compared to those obtained through the proximity model and the Aky & uuml;z-Winther model, along with empirical results. The R3Y with NL3* yields the closest barrier positions to experiment (mean squared error (MSE) = 0.061), while DD-ME2 excels for heights (MSE = 0.031) but shows larger position deviations due to greater diffuseness. M3Y-Paris outperforms M3Y-Reid, with BSk14 densities providing the best non-relativistic accuracy. The barrier parameters were further examined through calculation of the fusion cross-sections for various nuclei, comparing them to experimental data.
Abstract The level scheme of the doubly-odd nucleus 218 Ac is extended up to 3.3 MeV with the addition of 27 new transitions. The previously reported level scheme is revisited. Several transitions, whose placements were either tentative or ambiguous in the earlier study, have now been confirmed and firmly placed in the level scheme. In addition, an indication of a new alternating-parity structure is observed. The alternating-parity structures in 218 Ac are noted to terminate at intermediate excitation energies, and the higher-lying levels appear to have single-particle character, similar to those in the neighboring isotone 217 Ra. Theoretical calculations using the reflection-asymmetric triaxial particle-rotor model are performed in an attempt to understand the observed level structure in 218 Ac. However, the calculations fail to account for the observed properties of the alternating-parity structures. On the other hand, a systematic comparison with neighboring nuclei yields a better understanding of the observed properties. This suggests that 218 Ac exhibits transitional behavior between spherical and octupole-deformed nuclei, with octupole correlations dominating at low and intermediate excitation energies, whereas single-particle excitations dominate at higher excitation energies. Finally, the present experimental results are expected to contribute to the further development of theoretical approaches for describing transitional odd–odd nuclei, where structure evolves dynamically with excitation energy.
Abstract A unified framework sheltering the type-I Dirac seesaw, based on the Δ ( 27 ) group supplemented by other cyclic symmetries is proposed, preserving the naturalness of Yukawa couplings. It helps to visualize mass matrices within the lepton and quark sectors in terms of three universal parameters : Σ 1 , Σ 2 , and Σ 3 , highlighting that the down-type quark and light neutrino mass matrices exhibit a Hermitian texture. Several phenomenological aspects, such as lepton flavour violation and nonunitarity of the lepton mixing matrix are explored. The stability of the proposed texture under renormalization group evolution is also investigated.
In the framework of a macroscopic α -cluster model, the structural properties and the spectroscopy of the 24 Mg nucleus are investigated. Special attention is devoted to the electromagnetic selection rules imposed by the point-symmetry group D 4 h that leaves invariant the adopted 6 α equilibrium configuration, a square bipyramid. The analysis entails the application of group-theoretical identities and character tables, in a way familiar to quantum chemists. The results show that the occurrence of interband E0, E2, and M1, M2, M3 transitions is strictly regulated by the transformation properties of the excited vibrational modes to which the states in the process belong. Unlike the 12 C nucleus in the D 3 h -symmetric 3 α arrangement, M1 transition channels are active between states corresponding to a single quantum of vibrational excitation. Conversely, the measured E1 strengths in the 24 Mg spectrum are attributable to the excitation of single-nucleon degrees of freedom, as E1 transitions are forbidden by the model. The implications can be relevant for the spectroscopic analysis of 24 Mg, namely for the γ -transitions between collective states ascribed to different rotational bands.
We examine the relationship between the asymptotic normalization coefficient (ANC) of 6 Li and other low-energy observables in the α –deuteron system. Our analysis uses a set of calculations carried out within the ab initio no core shell model with continuum (NCSMC) using a variety of inter-nucleon interactions and basis sizes, and yielding 6 Li deuteron separation energies between 1.3 and 1.8 MeV (Hebborn et al 2022 Phys. Rev. Lett. 129 042503). These NCSMC calculations show that the square of the ANC is strongly correlated with the separation energy over this range. In this work, we investigate the origin of this correlation using the phenomenological R -matrix, a single-channel potential and a perturbative approach. We show that this correlation occurs because the depth of the α –deuteron central potential changes by only a small relative amount as the separation energy varies. We then investigate if the ANC can be accurately extracted from α –deuteron phase shifts in an ideal case in which low-energy data are available and there are no experimental errors. We find that both R -matrix and Coulomb-modified effective-range theory (CM-ERE) yield extracted ANCs close to, although not exactly equal to, the NCSMC value, provided the extrapolation is constrained by the known position of the bound-state pole and at least three terms are included in the fit function. The R -matrix approach converges faster than the CM-ERE as the number of parameters increases and is also more robust against the inclusion of low-energy and high-energy phase shift data. Finally, our study also shows that a naive quantification of uncertainties by comparing different truncations used in both theories is not accurate, and suggests the accuracy of ANCs extracted from phase shift data needs further investigation.
Through the application of a molecular model to band-head states in 9 B, a prediction of the Coulomb energy difference relative to the 1/2 + analogue state in 9 Be is calculated. Under such treatment, a positive shift in energy of 0.605 MeV is found to emerge from molecular structures defined by replication of experimental rotational-band parameters. Given the relationship between the spatial arrangement of clusters within the nucleus and the obtained Coulomb energy, it is also possible to examine nuclear structures using known Thomas–Ehrman shifts. Molecular structures built using the α – α separation, 2 β , required to give Thomas–Ehrman shifts for both a 1.84 and 0.8 MeV candidate of the 9 B(1/2 + ) analogue state ( β = 1.89 fm and β = 3.18 fm respectively) are used to calculate state inertial parameters ( A ). From these structures, it is found that a 1.84 MeV state ( A = 0.407 MeV) agrees with the experimental K = 1/2 + rotational band inertial parameter ( A = 0.41 ± 0.01 MeV) and a 0.8 MeV state does not ( A = 0.191 MeV). Thus, due to the large α – α spacing required to lower the Coulomb energy relative to 9 Be, the existence of a 0.8 MeV 9 B(1/2 + ) analogue state is highly unlikely. Indeed, excitation energies less than ≈1.25 MeV for a 1/2 + state, corresponding to a normal Thomas–Ehrman shift, can also be ruled out.
We study the chemical equilibration of a hot and dense quark-gluon plasma (QGP) at finite baryon density produced in relativistic heavy-ion collisions within conformal Gubser flow. Chemical non-equilibrium is incorporated through fugacity parameters in the parton phase-space distribution functions, whose evolution is governed by master rate equations coupled to the hydrodynamic expansion with transverse flow. We analyze the interplay between chemical equilibration and finite-density dynamics, and investigate its impact on hard thermal photon production. We observe that both finite density and transverse expansion delay chemical equilibration, leading to a chemically undersaturated medium with quarks lagging behind gluons. While the overall thermal photon yield from the expanding system is suppressed in the non-equilibrium scenario, we find an enhanced early-time contribution to high pT photon production. By analyzing the instantaneous photon emission in the presence of chemical non-equilibrium, we demonstrate that the rates exhibit a distinct temporal structure arising from the interplay of rapid cooling and evolving fugacities. These features may provide potential observable signatures of chemical equilibration dynamics in the QGP.
The directed flow ( v1) of identified hadrons ( pi +/-,K +/-,p,p & strns;,phi,Lambda, and Lambda & strns;) is studied in symmetric nuclear collisions (O+O, Cu+Cu, Ru+Ru, Au+Au, and U+U) at sNN=200 GeV using the string-melting version of a multiphase transport model with improved quark coalescence. The mid-rapidity v1-slope ( dv1/dy) and its charge-dependent splitting ( Delta dv1/dy) between particles and anti-particles are investigated as a function of nuclear mass number ( A) and collision centrality in both low- pT (0.2 -2.0 GeV/ c) and high- pT (2.0 -5.0 GeV/ c) regions. At low- pT, the v1-slope shows weak system-size dependence, while at high- pT strong system-size dependence is found and it becomes negative with nuclear mass number, reflecting the hard-soft asymmetry in particle production. The charge-dependent splitting Delta dv1/dy reveals a striking baryon-meson dichotomy: baryon pairs ( p-p & strns; and Lambda-Lambda & strns;) exhibit significant splitting that grows with system size, whereas meson pairs ( pi+-pi- and K+-K-) show minimal splitting. The effect of final state hadronic interactions on the v1-slope is found to be negligible confirming that it is primarily generated during the partonic phase and coalescence process. A comparison of the AMPT results with measurements from the STAR experiment at RHIC in Au+Au collisions establishes the transported quark contribution as a baseline for the observed charge-dependent v1 splitting, on top of which electromagnetic field effects must be considered.
We present a hybrid framework that integrates nuclear density functional theory with machine learning to investigate spin-parity effects in nuclear binding energies. Our approach employs a Skyrme energy density functional augmented with isospin-symmetry breaking terms calibrated through analysis of mirror displacement energies (MDEs). The machine learning component utilizes a multi-layer neural network architecture that learns the mapping between mean-field quantities and their symmetry-restored counterparts after angular-momentum and isospin projection. Our analysis reveals sensitivity to nucleon spin-parity alignments, with the symmetric K02 (aligned) configuration demonstrating improved predictive performance (RMSE = 0.26 MeV) compared to the anti-aligned K01 arrangement (RMSE = 0.31 MeV) when benchmarked against AME2020 experimental data. The framework exhibits reasonable extrapolation capabilities for nuclear mass predictions across the nuclear chart, showing performance comparable to established theoretical models including DZ28, FRDM2012, HFB25, WS, WS3, and WS4. The model reproduces MDEs with typical deviations below 0.3 MeV for most cases, although some discrepancies persist, indicating that isospin-symmetry breaking effects are not yet fully captured in all regions. This work demonstrates the potential of combining nuclear theory with physics-informed machine learning for nuclear mass predictions, while also highlighting areas where further theoretical development is needed.
Isobaric interference is a major limitation of mass spectrometric measurements of trace radionuclides. For accelerator mass spectrometry (AMS), isobaric separation is only available up to the mass range of fission products. The present work explores the potential of ion-laser interaction mass spectrometry (ILIAMS) for trace analysis of anthropogenic actinides with isobaric interference. Such capabilities are crucial for characterizing a highly sought-after isotopic spike material for Np-237 measurements and for accessing additional anthropogenic actinides with AMS, which could serve as environmental tracers, emission source signatures, or for determining the age of nuclear materials. ILIAMS is a novel low-energy isobar separation technique that combines a gas-filled ion cooler with reactive gases or high-power lasers to suppress isobars selectively. In this study, we demonstrate that UF4- can be selectively suppressed by two orders of magnitude using a 637 nm laser without affecting NpF4-. Initial results indicate the potential for the selective suppression of AmF5- to measure PuF5- or, in reverse, the suppression of PuF4- to measure AmF4- using a 355 nm laser. The admixture of O-2 with the buffer gas of the ion cooler can be used to suppress UF4- by up to seven and NpF4- by up to three orders of magnitude against PuF4-. The first application of these separation schemes for the characterization of a prototype Np-236 spike demonstrated the successful chemical removal of the co-produced isobars U-236 and Pu-236, and similar measurements can now be performed for other prospective Np spike materials. The isobar separation schemes developed here can also enable the measurement of Pu-241 without chemically removing Am-241 or Am-242m in the presence of Pu-242. Even measuring Pu-238 using AMS has become feasible for suitable sample matrices, despite the presence of the primordial isobar U-238. These are important isotopic signatures for attributing environmental contamination to potential sources of emissions.
The Ikeda diagram is a well-known map of the clusterization of alpha-like (N = Z = even) nuclei. Based on the binding energies, it predicts a cluster configuration to appear near the energy of the corresponding fragmentation. Here we investigate this question from a complementary viewpoint of the nuclear structure. We use a simple but microscopic method that can be applied systematically for the whole diagram. In particular, oscillator eigenstates, U(3) and U(4) selection rules, as well as Harvey's prescription are employed. The deformation of the clusters is allowed, therefore, a single fragmentation, e.g. core-plus-alpha, may result in different geometrical configurations, depending on the relative orientation. Their threshold energies are estimated. The connection of different fragmentations (and the shell structure) is investigated, and in most cases the model wave-functions turn out to be identical.
We performed a theoretical analysis of the effect of multichance fission on fission timescales. To this end, We used a one-dimensional Langevin dynamical model for fission to investigate a broad span of reactions with compound nuclear mass numbers ranging from 125 to 256. Calculations are performed in compliance with the measured prescission neutron multiplicities. The fission time distribution (FTD) for the initial compound nucleus and individual daughter nuclei formed due to particle evaporation is simulated. We found three different categories of FTD depending on the original compound nuclear mass. Also, multi-peaked FTD is observed at low excitation energies. These findings suggest that the concept of average fission time may be misleading, as the overall FTD may have distinct structures depending on the mass and excitation energy. In this respect, multichance fission is demonstrated to play a crucial role in deciding the final outcome.
The 2020 European Strategy for Particle Physics (ESPP) emphasized the critical importance of completing the high-luminosity LHC (HL-LHC) upgrade of both the accelerator and experiments in a timely manner, identifying it as a top priority for the field. The strategy also established two key recommendations for future accelerator initiatives: (i) the realization of an electron-positron Higgs factory as the highest-priority next collider, and (ii) the investigation, in collaboration with international partners, of the technical and financial feasibility of a hadron collider at CERN with a centre-of-mass energy of at least 100 TeV, potentially preceded by an electron-positron Higgs and electroweak factory. In alignment with these objectives, the Future Circular Collider (FCC) programme-comprising FCC-ee and FCC-hh-represents the preferred path forward for CERN, offering both precision and energy-frontier capabilities. However, the 2025 ESPP update calls for the identification of prioritized alternative options should the preferred FCC pathway prove infeasible or non-competitive. In this context, we propose LEP3, an electron-positron collider reusing the existing LHC tunnel, as a strategic backup to FCC-ee. LEP3 would exploit much of the research and development already carried out for FCC-ee, enabling high-precision studies of the Z, W, and Higgs bosons below the top-antitop production threshold. Combining strong physics potential with reduced cost, LEP3 provides performance comparable or superior to other fallback options-such as linear, muon, or LHeC colliders-while maintaining the technological continuity essential for a future energy-frontier collider. Conceived as a contingency, LEP3 complements, rather than competes with, the FCC-ee proposal.
In the pursuit of understanding the fundamental properties of the quark-gluon plasma (QGP) and the mechanisms governing strangeness production, extensive studies have been performed in the context of heavy-ion collisions (HICs). Investigating strange particle yields and their dynamics remains one of the central objectives in this field, and several transport models have been developed to provide theoretical interpretations. In this work the measurements of strange baryon production (Lambda, Sigma(0)), together with charged pions, kaons, protons, and antiprotons in Au+Au collisions at root sNN=3.5-14.5 GeV, are carried out using the Parton-Hadron-Quantum-Molecular-Dynamics (PHQMD) model, which incorporates deconfinement and chiral symmetry restoration and allows scenarios both with and without the QGP phase to be studied. Results for rapidity distributions and particle ratios are presented considering full acceptance coverage, midrapidity ( |y|<0.5) and in the acceptance of |y|<0.5 and the transverse momentum range of 0.4<2.0 GeV c(-1). PHQMD results are compared with the experimental data for top central and midrapidity region. The results indicate an enhancement of strangeness production, contributing to the horn-like structure observed in the excitation functions of the K+/pi(+), (Lambda + Sigma(0)) / pi and (Lambda + Sigma(0)) / p ratios within the present PHQMD model framework. The study presents and discusses PHQMD results as a function of both collision centrality and collision energy.
