In this work, we study a dark matter scenario where a dark $Z$ boson possessing mass mixing with the Standard Model (SM) $Z$ boson couples to the dark matter (DM) candidate and serves as the portal to the SM. The UV origin of the mass mixing in the form of an extra dark Higgs doublet and a scalar dark singlet provides new exotic scalars which can constitute the final state of DM annihilation during freeze-out. We find that existing constraints on the observed Higgs coupling strength, exotic Higgs searches, and dark matter observables complement each other, while future searches for exotic Higgs decays and resonant heavy scalars at HL-LHC will be sensitive to part of the allowed parameter space.

Light scalar or vector particles are among the most studied dark matter candidates. Yet, those are always described as scalar or vector fields. In this paper, we explore instead the embedding of the scalar particle in an antisymmetric rank-three tensor field, and the dark photon into an antisymmetric rank-two tensor field (a so-called Kalb-Ramond field), and construct minimal bases of effective interactions with Standard Model fields. Then, keeping phenomenological applications as our main objective, a number of theoretical aspects are clarified, in particular related to the impact of existing dualities among the corresponding free theories, and concerning their Stueckelberg representations. Besides, for the rank-two field, we present for the first time its full propagator, accounting for the possible presence of a pseudoscalar mass term. Thanks to these results, and with their different kinematics, gauge-invariant limits, and Lorentz properties, we show that these higher-form fields provide genuine alternative frameworks, with different couplings and expected signatures at low-energy or at colliders.

Recent work has demonstrated that discrete quantum walks, when extended to quantum cellular automata (QCAs), can, in the continuum limit, reproduce relativistic wave equations and quantum field theories (QFTs), including free quantum electrodynamics (QED). This QCA/QFT correspondence bridges quantum information processing and high-energy physics, raising fundamental questions about the nature of spacetime: whether it is the continuum QFT or the discrete QCA that is fundamental. For while Lorentz invariance appears robust experimentally, it may only approximate a deeper discrete structure, particularly at Planck-scale energies. This high-energy Lorentz violation is potentially observable either through cumulative effects over cosmic distances or via small deviations at accessible energies. In this paper, we analyze the QCA corresponding to QED and show that it implies both a deviation from the speed of light and spatial anisotropies. Using current experimental and astrophysical constraints, we place upper bounds on the QCA lattice spacing, providing insight into the plausibility of a fundamentally discrete spacetime.

We simulate the real-time evolution of the SU(3)-glasma generated in the early stages of high-energy proton-nucleus collisions, employing classical lattice gauge theory techniques. Our setup incorporates a realistic modeling of the proton’s internal structure and includes longitudinal fluctuations in the initial state, enabling the study of genuinely nonboost-invariant collision dynamics. Focusing on the momentum and angular momentum anisotropies of heavy quarks in the infinite mass limit, we find that the system retains significant anisotropy well beyond the characteristic timescale $\tau =1/Q_s$, with $Q_s$ being the saturation energy of the glasma, the only scale in our model. This persistence of anisotropy is further confirmed in the more realistic, nonboost-invariant scenario, across a range of fluctuation amplitudes. These findings pave the way for future investigations involving dynamical heavy quarks and more quantitative initializations of the glasma.

We demonstrate the feasibility of determining the strong coupling constant, ${\alpha }_s$, from the inclusive semileptonic decay width of $B$ mesons. We express the semileptonic $B$ decay width as a function of ${\alpha }_s(5\mathrm{GeV})$, the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$, and $b$- and $c$-quark masses in the $\overline{\mathrm{MS}}$ scheme. We fit ${\alpha }_s(5\mathrm{GeV})$ to current world averages of the $B^{\pm }$ and $B^0$ semileptonic decay widths. This yields ${\alpha }_s(5\mathrm{GeV})=0.245\pm 0.009$, corresponding to a five-flavor extrapolation of ${\alpha }_s(m_Z)=0.1266\pm 0.0023$. The primary uncertainty contributions arise from the uncertainty on the perturbative expansion and the value of $|V_{cb}|$. Future advancements, including higher-order perturbative calculations and precise measurements of $|V_{cb}|$ and $B$ decay widths from upcoming $B$ and $Z$ factories, could enable this method to determine ${\alpha }_s(m_Z)$ with a competitive precision of $\mathrm{\Delta }{\alpha }_s(m_Z)\sim 0.0018$. This precision is comparable to the current accuracy of ${\alpha }_s(m_Z)$ measurements from $\tau$-lepton decays, which is regarded as the most precise experimental approach.

The Hessian method is widely applied in the global analysis of parton distribution functions (PDFs), which use a set of orthogonal eigenvectors to give predictions of a physical observable. Its uncertainty is estimated based on the assumption that all physical observables can be approximately expressed as linear functions of the nonperturbative parameters in PDF. In this article, we report an improved Hessian method which takes the nonlinear effects into account in the uncertainty estimation. A pseudoglobal analysis is designed to numerically test the new method. The nonlinear uncertainties can significantly enlarge the original linear ones. Such uncertainties can be reduced with high precision data introduced into the global analysis. However, the nonlinear effect could still be sizable corresponding to the current precision of the experimental measurements.

We study exclusive diffractive production of vector mesons and photons using the color-dipole model with leading Fock-state light-front wave functions derived from Dyson-Schwinger and Bethe-Salpeter equations. New results for the $\varphi$ meson and real photon are presented. Without data fitting, our calculation well matches HERA data in certain kinematical domains. The key finding of this paper is that in a color-dipole model study for $\rho /\gamma$ and $\varphi$, where light quarks are involved, the leading $q\overline{q}$ approximation is valid only when $Q^2$ exceeds 20 and $10{\mathrm{GeV}}^2$ respectively, unlike $J/\psi$ which can be well described for $Q^2\approx 0{\mathrm{GeV}}^2$. This underscores the special role of $\varphi$ electroproduction in the color-dipole picture: it strikes a balance between the large dipole size typical of light mesons and the smaller size associated with high-$Q^2$ photons, making it potentially well suited for probing gluon saturation effects.

We study exotic baryon systems composed of anticharmed mesons and strange baryons using the extended local hidden gauge approach. By solving the coupled-channel Bethe-Salpeter equation with interaction kernels from vector meson exchange, we explore the formation of hadronic molecular states in sectors with strangeness $S=-1$, $-2$, $-3$, and $-4$. We systematically consider all possible isospin configurations and include both octet and decuplet baryons in the coupled-channel systems. Our results indicate that attractive interactions in $S=-1,-2$ can dynamically generate bound states, while systems with $S=-3,-4$ have repulsive interactions and do not support molecular formation. We also investigate vector-baryon systems with ${\overline{D}}^{*}$ and ${\overline{D}}_s^{*}$ mesons, finding similar bindings. The results show that bound exotic states are more likely when one or two strange quarks are present. To assess the robustness of our predictions, we perform an uncertainty analysis by varying the cutoff parameter $q_{\max }$, which affects the loop function regularization. The variations lead to moderate shifts in the pole positions, confirming the qualitative stability of the molecular states. These results highlight the strangeness dependence of the molecular formation mechanism and provide theoretical predictions that can guide future experimental searches for exotic multistrange-anticharm baryon systems.

In this work, we revisit the $3S\text{−}2D$ mixing scheme for the charmonia $\psi (4040)$ and $\psi (4160)$. We introduce a coupled-channel mechanism—distinct from the tensor-force contribution in potential models, which alone is insufficient to induce significant mixing—to describe the mixing between these states. Our analysis yields mixing angles of ${\theta }_1=7°$ and ${\theta }_2=10°$, inconsistent with the larger angle inferred from experimental data, such as the dielectronic widths of the $\psi (4040)$ and $\psi (4160)$. We discuss possible origins of this discrepancy and emphasize the need for future experiments to resolve it. Precise measurements of the resonance parameters and dielectronic decay widths, via both inclusive and exclusive processes, will be crucial in clarifying this issue.

The transition amplitude of a kaon to a pion and two off-shell photons is studied. First, it is computed at leading order (one-loop level) of the chiral perturbation theory expansion. Explicit analytical results for the leading-order amplitude are presented, constituting the first complete calculation for the doubly off-shell case. Subsequently, it is reevaluated by employing a refined diagrammatic notation and a generic ansatz incorporating effects beyond leading order. The dependence on the underlying $K\pi PP$ vertex parameters is analyzed. This offers valuable insights into amplitude properties and allows inclusion of unitarity corrections from $K\to 3\pi$, yielding the complete $K\to \pi {\gamma }^{*}{\gamma }^{*}$ amplitude structure. Both the charged and neutral channels are treated in parallel. The presented results provide crucial input for phenomenological studies of related rare decays like $K\to \pi {\ell }^{+}{\ell }^{-}[\gamma ]$ or $K\to \pi {\ell }_1^{+}{\ell }_1^{-}{\ell }_2^{+}{\ell }_2^{-}$ and support ongoing precision measurements at experiments like NA62 at CERN. These results may also find application in other related processes, including ${\eta }^{(\prime )}$ decays.

Anomaly detection—identifying deviations from Standard Model predictions—is a key challenge at the Large Hadron Collider due to the size and complexity of its datasets. This is typically addressed by transforming high-dimensional detector data into lower-dimensional, physically meaningful features. We tackle feature extraction for anomaly detection by learning powerful low-dimensional representations via contrastive neural embeddings. This approach preserves potential anomalies indicative of new physics and enables rare signal extraction using novel machine-learning-based statistical methods for signal-independent hypothesis testing. We compare supervised and self-supervised contrastive learning methods, for both Multilayer perceptron-and transformer-based neural embeddings, trained on the kinematic observables of physics objects in LHC collision events. The learned embeddings serve as input representations for signal-agnostic statistical detection methods in inclusive final states. We achieve significant improvement in discovery power for both rare new physics signals and rare Standard Model processes across diverse final states, demonstrating its applicability for efficiently searching for diverse signals simultaneously. We study the impact of architectural choices, contrastive loss formulations, supervision levels, and embedding dimensionality on anomaly detection performance. We show that the optimal representation for background classification does not always maximize sensitivity to new physics signals, revealing an inherent trade-off between background structure preservation and anomaly enhancement. We demonstrate that combining compression with domain knowledge for label encoding produces the most effective data representation for statistical discovery of anomalies.

The coherent CAPTAIN-Mills (CCM) experiment is a liquid argon (LAr) light collection detector searching for MeV-scale neutrino and beyond Standard Model physics signatures. Two hundred eight-inch photomultiplier tubes instrument the seven-ton fiducial volume with 50% photocathode coverage to detect light produced by charged particles. CCM’s light-based approach reduces requirements of LAr purity, compared to other detection technologies, such that sub-MeV particles can be reliably detected without additional LAr filtration and with $\mathcal{O}(1)$ parts per million of common contaminants. We present a measurement of LAr light production and propagation parameters, with uncertainties, obtained from a sample of MeV-scale electromagnetic events. The optimization of this high-dimensional parameter space was facilitated by a differentiable optical photon Monte Carlo simulation and detailed photomultiplier tube response characterization. This result accurately predicts the timing and spatial distribution of light due to scintillation and Cherenkov emission in the detector. This is the first description of photon propagation in LAr to include several effects, including anomalous dispersion of the index of refraction near the ultraviolet resonance, Mie scattering from impurities, and Cherenkov light production.

This article presents a study of single ${\pi }^{+}$ production in neutrino neutral-current interactions ($\mathrm{NC}1{\pi }^{+}$) using the FGD1 hydrocarbon target of the ND280 detector of the T2K experiment. We report the largest sample of such events selected by any experiment, providing the first new data for this channel in over four decades and the first using a sub-GeV neutrino flux. The signal selection strategy and its performance are detailed together with validations of a robust cross section extraction methodology. The measured flux-averaged integrated cross-section is $\sigma =(6.07\pm 1.22)\times {10}^{-41}{\mathrm{cm}}^2/\mathrm{nucleon}$, $1.3\sigma$ above the NEUT v5.4.0 expectation.

No experimental test to date has provided conclusive evidence on the quantum nature of gravity. Recent proposals, such as the Bose-Marletto-Vedral experiment, suggest that generating entanglement could serve as a direct test. Motivated by these proposals, we study a system of three-harmonic oscillator system, with the mediator oscillator operating in two distinct parameter regimes: a heavy mediator regime and a light mediator regime. These regimes induce qualitatively different entanglement dynamics between the terminal oscillators. Crucially, distinguishing these regimes experimentally remains challenging when relying solely on entanglement measures. We demonstrate that the dynamical fidelity susceptibility offers a viable and sensitive probe to contrast the regimes in practice. Our results provide testable signatures for optomechanical and trapped-ion platforms simulating gravitational interactions, and provide new avenues to characterize quantum-gravity-inspired systems beyond entanglement-based protocols.

Diffusion, as described by Fick’s laws, governs the spreading of particles, information, data, and even financial fluctuations. However, due to its parabolic structure, the diffusion equation leads to an unphysical prediction: any localized disturbance instantaneously affects the entire system. The Maxwell-Cattaneo (MC) model, originally introduced to address relativistic heat conduction, refines the standard diffusion framework by incorporating a finite relaxation time $\tau$, associated with the onset of local equilibrium. This modification yields physically relevant consequences, including the emergence of propagating shear waves in liquids and second sound in solids. Holographic methods have historically provided powerful tools for describing the hydrodynamics of strongly correlated systems. However, they have so far failed to capture the dynamics governed by the MC model, limiting their ability to model intermediate time-scale phenomena. In this work, we construct a simple holographic dual of the Maxwell-Cattaneo model and rigorously establish its equivalence through a combination of analytical and numerical techniques. As an important byproduct of our analysis, and contrary to previous ad hoc assumptions, we find that effective field theories featuring nonhydrodynamic modes exhibit a generalized form of Kubo-Martin-Schwinger symmetry, which reduces to the canonical form only in the hydrodynamic limit.

We discuss the optical appearance from thin accretion disks in parametrized black holes, namely, solutions characterized by an arbitrarily large number of parameters without any regards to the theory of the gravitational and matter fields they come from. More precisely, we consider the leading-order terms of the spherically symmetric Johanssen-Psaltis (JP) and Konoplya-Rezzolla-Zhidenko (KRZ) parametrizations after imposing constraints from asymptotic flatness and solar system observations. Furthermore, we use the inferred correlation, by the Event Horizon Telescope Collaboration, between the size of the bright ring (which is directly observable) and the size of the central brightness depression (which is not) of M87 and Sgr ${\mathrm{A}}^{*}$ central supermassive objects, to constrain the parameters of the leading-order JP and KRZ solutions. Using ten samples of the Standard Unbound distribution previously employed in the literature to reproduce certain scenarios of General Relativistic HydroDynamical simulations, we produce images of four samples of JP and KRZ geometries enhancing and diminishing the shadow’s size, respectively. Via a qualitative and quantitative analysis of the features of the corresponding photon rings and, in particular, of their relative brightness, we argue that it should be possible to distinguish between such parametrized solutions and the Schwarzschild geometry via future upgrades of very long baseline interferometry. We furthermore consider images of some naked objects within these parametrizations, and also discuss the role of inclination in comparing images of different black holes.

We conducted a theoretical analysis of the violation of the equivalence principle within a broad class of scalar-Gauss-Bonnet theories that exhibit spontaneous scalarization. Beginning with the Jordan frame, we performed a conformal mapping to identify the equivalent model in the Einstein frame. This approach revealed that the Gauss-Bonnet coupling introduces a mixed term that links the Einstein tensor to the kinetic terms, along with an additional kinetic term associated with the box operator, echoing characteristics of Horndeski-like theories. We investigate a potential violation of the weak equivalence principle using a point-like particle framework for dark matter and baryonic matter. Our findings reveal that differing couplings lead these particles to follow distinct geodesics in the Einstein frame. We also examined the violation of the strong equivalence principle through the Nordtvedt effect within the framework of an extended parametrized post-Newtonian (PPN) formalism. We provide a concrete example of scalarized theories featuring extended PPN parameters that deviate from general relativity, comparing these results against observational constraints from the Cassini mission, the MESSENGER mission, and the Lunar Laser Ranging experiment. While the Cassini bounds remain the most stringent, the constraints on the Nordtvedt parameter offer significantly better restrictions on the parameter space than those derived from the precession rate of Mercury’s perihelion.

We investigate the motion of test particles in quantum-gravitational backgrounds by introducing the concept of q–desics, quantum-corrected analogs of classical geodesics. Unlike standard approaches that rely solely on the expectation value of the spacetime metric, our formulation is based on the expectation value of quantum operators, such as the affine connection operator. This allows us to capture richer geometric information. We derive the q–desic equation using both Lagrangian and Hamiltonian methods and apply it to spherically symmetric static backgrounds obtained from canonical quantum gravity. Exemplary results include lightlike radial motion and circular motion with quantum gravitational corrections far above the Planck scale. This framework provides a refined description of motion in quantum spacetimes and opens new directions for probing the interface between quantum gravity and classical general relativity.

We construct a consistent three-dimensional Einstein-Gauss-Bonnet theory as a vector-tensor theory within the generalized Proca class by employing a regularization procedure based on the Weyl geometry, which was introduced recently by Charmousis, Fernandes, and Hassaine [Phys. Rev. D 111, 124008 (2025).]. We then obtain an asymptotically Anti-de Sitter (${\text{AdS}}_3$), static, and circularly symmetric black hole solution with primary Proca hair. Afterward, we investigate the effect of the scalar-tensor Gauss-Bonnet coupling constructed previously by different regularization schemes. We further generalize these solutions by incorporating an electric charge. As special cases, we find a regular black hole solution in addition to charged and uncharged stealth Banados-Teitelboim-Zanelli black hole solutions.