Particles, Volume 9, Issue 3 (September 2026) – 14 articles

We review the current understanding of transversely polarized quarks inside longitudinally polarized nucleons from the perspective of the longi-transversity distribution function and transverse-momentum-dependent (TMD) factorization. Employing the recently developed TMD evolution formalism for the unpolarized and longi-transversity distribution functions, we present the theoretical formalism for the relevant physical observables, namely the $A_{LL}^{\cos 2\varphi }$ asymmetry in the Drell–Yan process and the $A_{UL}^{\sin 2{\varphi }_h}$ asymmetry in the semi-inclusive deep inelastic scattering process. The phenomenological results are presented numerically. Full article

The ICARUS Collaboration is now entering its sixth year of continuing operations of the 760-ton liquid argon T600 detector. The T600 was overhauled at CERN after operations at the LNGS underground laboratory in Italy and moved to its present location at FNAL—as part of the Short-Baseline Neutrino (SBN) program—where it completed its commissioning phase in June 2022. At FNAL, ICARUS collects neutrino interactions from both the Booster Neutrino Beam (BNB) and off-axis from the Neutrinos at Main Injector beam (NuMI). ICARUS has accumulated approximately $10.6\times {10}^{20}$ protons on target (POT) with the BNB and about $6.2\times {10}^{20}$ POT with NuMI. Within the SBN program, ICARUS will search for evidence of short-baseline oscillations, potentially explained by eV-scale sterile neutrinos, jointly with the Short-Baseline Near Detector (SBND). In addition, ICARUS is performing stand-alone oscillation searches in disappearance mode and measuring neutrino cross sections on argon with both the BNB and NuMI beams. It is also performing searches for additional Beyond the Standard Model signatures. This paper describes the analysis status as shown at ICNFP 2025. Full article

We present a stability analysis of a dark-fluid model described as a non-relativistic, rotating, non-viscous, self-gravitating fluid. We assume there is spherical symmetry and model the matter using a polytropic equation of state. The resulting coupled nonlinear partial differential equation system is solved using a self-similar ansatz known from the Guderley–Landau–Stanyukovich problem. We find that three of the four Lyapunov exponents are negative, while only one is positive. This indicates the existence of one unstable direction and three contracting directions in phase space. The single positive exponent is relatively small, suggesting that the self-similar solution is only weakly unstable and remains dynamically robust over the investigated interval. Full article

Based on nine years of flight data from the DArk Matter Particle Explorer (DAMPE) and a novel gamma-ray selection algorithm developed in previous work, we recalculate the instrument response functions (IRFs) in the 1–10⁴ GeV energy range. We present PSF-weighted phase-folded light curves of the bright gamma-ray pulsars Vela and Geminga, obtained with an extended version of the PINT Is Not TEMPO2 (PINT) software adapted to our analysis needs. This work lays the groundwork for further refinement of the IRFs through pulsar analyses, improving DAMPE’s performance for gamma-ray astronomy and searches for potential dark-matter signatures. Full article

We review the role of primordial black holes (PBHs) for illuminating the dark ages of the cosmological evolution and as dark matter (DM) candidates. We elucidate the role of phase transitions for primordial black hole formation in the early Universe and focus our attention on the cosmological QCD phase transition within a recent microscopic model. We explore the impact of physics beyond the Standard Model (SM) on the cosmic equation of state and the probability distribution for the formation of PBHs, which serve as candidates for DM and contribute to present-day binary black hole merger events. Full article

This set of notes complements the lectures and recitation sessions discussed in the following graduate schools: Hampton University Graduate Summer Program (HUGS) at Jefferson Lab (years 2018, 2019, 2021), the International School and Workshop on Probing Hadron Structure at the Electron-Ion Collider at International Centre for Theoretical Sciences (ICTS) (2024), Frontiers in Nuclear and Hadronic Physics at The Galileo Galilei Institute for Theoretical Physics (GGI) (2025), and the International Workshop and School on Hadron Structure and Strong Interactions at Nanjing University (2025). Full article

In this manuscript, we present the results of our studies on the exclusive photoproduction of quarkonium-photon pairs with large invariant mass. In our analysis, we focus on the production of the ${\eta }_c\gamma$ and ${\chi }_{cJ}\gamma$ pairs in high energy kinematics. We use the Color Glass Condensate (CGC) framework for analysis and demonstrate that at leading order in ${\alpha }_s$ the cross-sections of these processes are determined by the forward dipole scattering amplitude. The kinematic distributions of the produced particles allow us to study the dipole amplitude in detail, making this process a very clean probe for studies of saturation physics. Using phenomenological parametrizations of the dipole amplitudes, we estimate numerically the differential production cross-sections for ${\eta }_c\gamma$ and ${\chi }_c\gamma$ in the kinematics of ultraperipheral collisions at the LHC and the future Electron-Ion Collider (EIC). Furthermore, we assess the role of this process as a possible background to the exclusive photoproduction of C-even quarkonia, which is frequently considered as a tool for odderon searches. Full article

We investigate the effects of Lorentz invariance violation (LIV) on the resonance structure of the Z boson in high-energy collider experiments. Building on previous work where resonance line-shape distortions were established, we extend the analysis to include spacelike and lightlike orientations of the LIV vector. The modified dispersion relation induces rapidity-dependent distortions of the resonance profile, with effects growing strongly at large rapidities. In anisotropic scenarios, the signal exhibits characteristic sidereal-time modulation due to the rotation of the Earth relative to the preferred LIV direction. We show that, while global analyses dilute the effect, dedicated studies focusing on high-rapidity bins and sidereal-time dependence can significantly enhance sensitivity. The resulting shifts in reconstructed resonance parameters can reach or exceed current experimental precision for LIV scales as low as ${\delta }_{LIV}\sim {10}^{-8}$. These results demonstrate that collider measurements of unstable gauge bosons provide a complementary and competitive probe of Lorentz violation. Full article

We solve the Goldstone-boson-exchange (GBE) relativistic constituent quark model of light and strange baryons by using the Faddeev approach. The model reproduces the vacuum mass spectrum of light and strange baryons below 2 GeV reasonably well. To test the sensitivity of the model to possible medium-induced effects, we vary the masses of the constituent quarks and the exchange bosons, the confinement strength, and the quark–meson coupling constant. In a parametric study, we consider a set of power-law scaling relations for these parameters, including some motivated by constituent quark-level current algebra relations. We find that the baryon spectrum is most sensitive to the quark–meson coupling constant, and generally observe a decrease in baryon mass with decreasing constituent quark mass. We qualitatively estimate the impact of these mass shifts on ideal-gas baryon yields and yield ratios. Absolute yields can already change significantly for mass shifts of a few 10 MeV, whereas yield ratios are strongly modified only when the compared baryons have different constituent quark mass dependence. Full article

We review recent interferometric schemes designed to probe physics beyond the Standard Model through the detection of geometric phases. Within the kinematic approach to non-cyclic geometric phases, we discuss how interactions with hidden-sector degrees of freedom, such as axion-like particles and mirror-matter candidates, can induce potentially observable phase shifts in ordinary fermionic systems. We further show how the same geometric framework can be extended to particle mixing systems and fundamental symmetries, providing a phase-based signature of the Charge–Parity–Time (CPT) violation. These results illustrate how geometric phases can encode information that is not always directly accessible through standard transition probabilities, making quantum interferometry a complementary tool for testing dark-sector interactions, fundamental properties of elementary particles, acceleration-induced quantum-field effects, and phase-based thermometry. We also critically assess the experimental requirements and limitations of the proposed schemes. Full article

The discrepancy between observed galaxy rotation curves and predictions based on visible baryonic matter remains a central challenge in astrophysics. Within the standard ΛCDM framework, these observations are explained through extended halos of non-baryonic dark matter, while alternative approaches such as Modified Newtonian Dynamics reproduce many galactic scaling relations through empirical modifications of low-acceleration dynamics. Recent advances in symbolic machine learning provide a complementary route for investigating whether stable empirical relations can be discovered directly from observational data without imposing strong theoretical priors. In this work, we present the Phenomenological Dark Matter Nonlinear Pipeline, an AI-assisted symbolic discovery framework designed to identify mathematical relationships linking baryonic and observed gravitational accelerations. The analysis was performed using 3175 radial measurements from 175 galaxies derived from SPARC-based rotation-curve catalogs. Symbolic regression was conducted across 173 independent leave-one-galaxy-out validation folds, followed by bootstrap analysis, residual diagnostics, and regime-specific testing. The symbolic search repeatedly converged toward a stable family of non-linear logarithmic acceleration relations exhibiting strong recurrence across independent discovery folds. The resulting empirical relation successfully reproduces the observed Radial Acceleration Relation, naturally generates Baryonic Tully–Fisher Relation like scaling without explicit enforcement during training, and consistently outperforms classical Newtonian gravity while remaining competitive with a MOND-like reference model. Global validation yielded a coefficient of determination of R² = 0.9026 compared with R² = 0.8934 for the MOND-like model and R² = −0.0485 for the Newtonian baseline. Additional analyses demonstrate stable performance across low-acceleration systems, low-surface-brightness galaxies, and other galactic environments. The recovered relation should be interpreted as an empirically discovered scaling law rather than a replacement for General Relativity, ΛCDM, or existing modified-gravity theories. Nevertheless, the repeated emergence of a common symbolic structure across independent validation folds highlights the potential of AI-assisted symbolic discovery as a tool for uncovering interpretable empirical regularities in complex astrophysical datasets. Full article

These notes comprise the material I presented during the International Workshop and School on Hadron Structure & Strong Interactions which took place in Nanjing in 2025. The aim of the lectures was to introduce and motivate the study of Generalised Parton Distributions (GPDs) for an audience of Master and Ph.D. students in hadron physics, with little to no background regarding the description of exclusive processes at high virtuality. Full article

We present state-of-the-art kinetic theory determination of the neutron abundance available for the Big-Bang nucleosynthesis (BBN). This paper is motivated by the study of the neutron lifespan measured in the laboratory and the unknown strength of weak interactions coupling constant $G_{\mathrm{F}}$ at finite temperature in the primordial Universe. We draw attention to the relevant dependence of $G_{\mathrm{F}}$ on the symmetry breaking Weinberg angle $s_{\mathrm{W}}^2$, which is a free parameter in the standard model of particle physics. We establish how the value of $s_{\mathrm{W}}^2$ by way of $G_{\mathrm{F}}$ modification influences the neutron abundance available for BBN and neutron lifetime. Full article

After the invention of radioactive nuclear beams, studies on nuclei far from the stability line brought up many new phenomena not expected in nuclei near the stability line. Among them, neutron halos and changes in magic numbers were outstanding discoveries. To understand these phenomena, nuclear structure models needed many new developments such as the treatment of loosely bound systems and proton neutron asymmetry. One important question on the importance of the tensor interactions has been raised recently. In this review, I present evidence of tensor interactions in nucleon momentum distribution and the effects of tensor interactions on the structure of nuclei. In particular, the importance of 2p–2h configurations excited by the tensor interactions will be introduced. I show that the appearance and disappearance (blocking) of the 2p–2h configuration is responsible for the change in shell structure. I also present a recent experimental result that shows the existence of such configurations in ¹⁶O nuclei. Full article