In the present work, we construct a color gauge invariant theory of diquark interactions. With the transformation rule of the diquark fields and the definition of the covariant derivatives under color SU(3) symmetry, we construct the gauge invariant Lagrangians describing the vertices of $S-S-G$, $A-A-G$, $S_Q-S_Q-G$, $A_Q-A_Q-G$, and $S_Q-A_Q-G$, where $S_{(Q)}$ is the light (heavy) scalar diquark field, $A_{(Q)}$ is the light (heavy) axial vector diquark field, and $G$ is the gluon field. And then we derive the one-gluon-exchange effective potentials for diquark-antidiquark interactions using the obtained Lagrangians. By comparing these potentials with those in the Godfrey-Isgur quark model, the coupling constants of the Lagrangians are determined. We find that the potentials are mainly made of Coulomb, contact, and tensor terms. The potential for the process $S\overline{A}\to A\overline{S}$ is 0, since ${\mathcal{L}}_{SAG}=0$. And the tensor terms proportional to $g^2$ are negligible.

We propose new solutions to MiniBooNE electronlike excess and based on interactions involving light dark matter and/or neutrinos, that is also consistent with the photonlike excess at MicroBooNE. The novelty of our proposal lies in the utilization of a photon arising from 2-to-3 scattering processes between a nucleus/nucleon and a neutrino and/or dark matter via exchanges of light mediators. We find that viable regions exist in the coupling and mass parameter space of the mediators and light dark matter that can simultaneously explain the observed excesses and remain consistent with current experimental constraints. We further highlight that these scenarios can be tested with upcoming data from various ongoing experiments.

An intriguing and elementary possibility is that familiar massless particles like the photon could be “continuous spin” particles (CSPs) with a small but nonzero spin Casimir $\rho$. In this case, the familiar two polarization states of the photon are accompanied by an infinite tower of integer spaced helicity modes, with couplings dictated entirely by Lorentz symmetry and the parameter $\rho$. We present a formalism for computing bound state atomic transitions for scalar QED when $\rho \ne 0$, employing path integral methods not often used for bound state computations, but that readily generalize to the CSP case. We compute several illustrative amplitudes and show that $\rho \ne 0$ opens new decay channels for atomic transitions with rates controlled by $\rho \alpha /\omega$ for transition frequency $\omega$. These new channels can appreciably modify the rates of “forbidden” transitions. For example, the lifetime of the hydrogen $2s$ state would be affected at $O(1)$ for $\rho \sim 0.1\mathrm{eV}$, suggesting new directions for fundamental tests of QED in laboratory experiments.

Instead of the energy recoil signal at direct detection experiments, dark fermion appears as missing energy at hadron colliders. For a fermionc dark sector particle that coupled with quarks and neutrino via absorption operators, its production at collider is accompanied by an invisible neutrino. We study in details the mono-$X$ (photon, jet, and $Z$) productions at the Large Hadron Collider (LHC). We start from the quark-level absorption operators to make easy comparison between the collider and direct detection experiments. In other words, we study the model-independent constraints on a dark fermion with absorption operator. In addition, the interplay and comparison with the possible detection at the neutrino experiments, especially Borexino, is also briefly discussed. We find that light nuclear target can provide the stronger constraints on both spin-dependent and spin-independent absorption operators.

We study the viability of light thermal dark matter (DM) in the sub-GeV mass range in view of the stringent new DAMIC-M limits on DM-electron scattering. Considering a Dirac fermion singlet DM charged under a new Abelian gauge symmetry $U(1)$, we outline two possibilities: (i) family nonuniversal $U(1)$ gauge coupling with resonantly enhanced DM annihilation into Standard Model (SM) fermions, and (ii) family universal dark $U(1)$ gauge symmetry where relic density is set by DM annihilation into light gauge bosons. As an illustrative example of the first class of models, we consider a gauged $L_{\mu }-L_{\tau }$ extension of the SM having interesting detection prospects at several experiments. While both of these classes of models lead to the observed DM relic and consistency with DAMIC-M together with other experimental limits, the second class of models also lead to strong DM self-interactions, potentially solving the small-scale structure issues of cold dark matter. While a vast part of the parameter space in both the models is already ruled out, the current allowed region of parameter space can be further probed at ongoing or future experiments, keeping the models testable.

We propose a new class of flavor models in which the spurion that breaks Standard Model flavor symmetries transforms in a nonminimal representation. Hierarchies in fermion masses, which arise from multiple insertions of this spurion, may be generated in a technically natural, accidental manner, from a handful of untuned $\mathcal{O}(1)$ elements in the UV. This relies explicitly on the non-Abelian nature of the symmetry, distinguishing it from standard Froggatt-Nielsen-like scenarios. The pattern of flavor violating operators at dimension-6 can radically differ from previously considered scenarios, and emphasises the need for a broad flavor program across all generations.

In this work, we explore how the 2-Higgs doublet model (2HDM) type-I, extended by an inert doublet, can provide an explanation for the recently observed excesses at the Large Hadron Collider (LHC) in the $\gamma \gamma$ and ${\tau }^{+}{\tau }^{-}$ final states. Hence, by imposing theoretical constraints and experimental bounds on the model parameter space, our findings show that a light $CP$-even Higgs boson, $h$, with a mass around 95 GeV, can account for these anomalies. This result aligns with the excess in $b\overline{b}$ signatures reported in earlier data from the Large Electron-Positron (LEP) collider.

We explore an interacting dark matter (DM)-dark energy (DE) framework that naturally yields an effective dynamical DE equation of state crossing the phantom barrier at early times, as indicated by recent DESI data, while also accounting for the observed isotropic rotation of the cosmic microwave background (CMB) linear polarization. Within this unified framework, we also explain the DM relic abundance without introducing additional fields or couplings. Depending on the DE potential, we identify two viable scenarios: a superheavy freeze-in DM requiring a high reheating temperature, or a strongly interacting dark sector with a GeV–TeV scale thermal DM candidate.

The nature of the Higgs boson, whether it is elementary or composite, will be investigated through precision measurements at the collider experiments. In composite Higgs scenarios, the Higgs may manifest as a pseudo-Nambu-Goldstone boson (pNGB) arising from a strongly interacting sector. The $SU(5)/SO(5)$ composite Higgs model features a rich scalar sector, with the decay patterns of the scalars being heavily influenced by the way fermions are embedded in various representations of $SU(5)$. We discuss how masses of the pNGB scalars and their couplings depend functionally on the compositeness scale and the parameters of the strong sector. Unique decay modes of the scalars emerge from the model when the mixing among the various pNGB scalars is non-negligible. We present a comprehensive and thorough analysis of the fermiophilic and fermiophobic decay modes of the pNGB scalars. Significant differences are observed in the decay patterns of the two singly charged scalars. Further, the decay of one pNGB to another on shell pNGB when masses exceed about 1 TeV presents a rich phenomenology, leading to distinctive signatures at the colliders. In this context, the future muon collider offers a promising avenue for detecting pNGB scalars with masses larger than 1 TeV, especially in final states involving $W/Z$ fatjets.

We search for the existence of ultralight axions coupling to electrons and photons using data from the NuSTAR telescope directed toward the galaxies M82, M87, and M31. We focus on electron bremsstrahlung and Compton scattering for axion production in stars, summing over the stellar populations found in the target galaxies when computing the axion luminosity. We then compute the hard x-ray signal that arises from the conversion of these axions to photons in each galaxy’s magnetic fields, inferred from analog galaxies in cosmological magnetohydrodynamic simulations. Analyzing NuSTAR data toward these galaxies between roughly 20 to 70 keV, we find no evidence for axions and set leading constraints on the combined axion-electron and axion-photon coupling at the level of $|g_{aee}\times g_{a\gamma \gamma }|\lesssim 8.3\times {10}^{-27}{\mathrm{GeV}}^{-1}$ for $m_a\lesssim {10}^{-10}\mathrm{eV}$ at 95% confidence, with M82 providing the most stringent constraints.

The small-$x$ regime remains a key testing ground for perturbative QCD and future lepton-hadron collider physics. We demonstrate that the long-standing $\sim 30\%$ spread among global next-to-next-to-leading-order parton distribution functions (PDFs) for heavy-flavor parton densities at small $x$ has now converged below $\approx 17\%$. Using the latest nnpdf4.0, ct18, and msht20 sets, we quantify a maximal relative deviation of ${\mathrm{\Delta }}_{\max }\simeq 16.8\%$ at $x={10}^{-6}$ and $Q=100\mathrm{GeV}$. This convergence, further stabilized by consistent ${\alpha }_s$ and scale variations, marks a new precision frontier for the heavy-flavor sector. We evaluate the phenomenological impact for heavy-quark electroproduction at future $ep$ colliders (LHeC and FCC–eh), showing that PDF-driven cross section uncertainties for $e^{-}p\to e^{-}c\overline{c}X$ and $e^{-}p\to e^{-}b\overline{b}X$ have been reduced by nearly a factor of 2 compared to 2013 estimates.

We investigate a scale-invariant general two-Higgs-doublet model with explicit $CP$ violation. Using the Gildener-Weinberg method, we analyze the Higgs mass spectrum and couplings at the one-loop level, focusing on $CP$ violation originating from both the Higgs potential and the Yukawa sector. We show that, due to the flatness condition, both $CP$-even and $CP$-odd mixings between the 125 GeV Higgs boson and the heavier Higgs states arise only radiatively. As a result, the Higgs couplings to gauge bosons and fermions remain Standard Model-like, in agreement with current LHC constraints. We also find that the magnitude of $CP$ violation from the Higgs potential depends on the new complex Yukawa couplings and heavy Higgs masses, due to the flatness condition. In the case where only an additional top Yukawa coupling (${\rho }_{tt}$) is present, the electron electric dipole moment is directly proportional to $\mathrm{Im}{\rho }_{tt}^2$. Furthermore, a nontrivial cancellation region can occur for a specific Higgs mass spectrum. We extend our analysis to scenarios with an additional complex electron Yukawa coupling, identifying the conditions under which the electron electric dipole moment is suppressed or vanishes.

Optically levitated nanospheres are highly sensitive to the motion of their center of mass even under small momentum transfer. We propose detecting exotic particles via nucleon scattering in such spheres in the context of an ongoing experiment. We suggest that the 200 nm-diameter spheres, featuring a $4\times 4$ array configuration and its upgrade, can achieve sensitivity to nuclear couplings of solar axionlike particles (ALPs), exclusively targeting previously unconstrained regions of parameter space. This setup can offer the first probe of a 14.4 keV solar ALP, which is difficult to find in axion experiments and conventional direct searches. Additionally, we also demonstrate the reach of the same experiment for other light beyond the standard model (BSM) scenarios. The same setup will be sensitive to pseudoscalar dark matter in the $\sim 10\mathrm{keV}$ mass range. In contrast, a smaller sphere with a diameter of 15 nm benefits from overall coherence enhancement, enabling the detection of pseudoscalar and vector dark matter down to $\mathcal{O}(100)\mathrm{eV}$ even with a single sphere. This smaller setup also offers the potential for the direct detection of Earth-bound dark matter strongly coupled with visible matter, even with its minimal velocity and tiny fractional abundance.

In this work, we investigate the sensitivity of Hyper-Kamiokande (hyper-K) to light sterile neutrinos within the ($3+1$) framework, consisting of three active and one sterile neutrino state. We focus on the regime where the new mass-squared splitting satisfies $\mathrm{\Delta }{m}_{41}^2\lesssim 1{\mathrm{eV}}^2$, a parameter space complementary to short-baseline sterile-neutrino searches. Using both accelerator and atmospheric neutrino samples, we evaluate the expected capability of hyper-K to constrain active–sterile mixing. Our results show that hyper-K can significantly improve current bounds on sterile-neutrino parameters and achieve sensitivity that is competitive with that of future dedicated experiments.

We present lattice QCD calculations of the odd Mellin moments of pion valence-quark generalized parton distribution up to fifth order $⟨x^4⟩$ and for the skewness range $[-0.33,0]$ using operator product expansion of bilocal quark-bilinear operators. The calculations are performed on an ensemble with lattice spacing $a=0.04\mathrm{fm}$ and valence pion mass 300 MeV, employing boosted pion states with momenta up to 2.428 GeV and momentum transfers reaching $2.748{\mathrm{GeV}}^2$. We employ ratio-scheme renormalization and next-to-leading logarithmic resummed perturbative matching. At zero skewness, our results are consistent with previous lattice studies. By combining matrix elements at multiple values of skewness and momentum transfer, skewness-dependent moments are obtained through simultaneous polynomiality-constrained fits.

We review the shift (translation) and time reversal symmetries of Hamiltonian staggered fermions and their connection to continuum symmetries concentrating in particular on the case of massless fermions and ($3+1$) dimensions. We construct operators using the staggered fields that implement these symmetries on finite lattices. We show that shifts composed of an odd multiple of the elementary shift anticommute with time reversal and are related to continuum axial transformations. We argue that the presence of these nontrivial commutation relations implies the existence of lattice ’t Hooft anomalies. From the shifts we also construct a set of conserved, quantized charges that generate continuous symmetries of the lattice theory. In general these do not commute with the vector charge signaling further ’t Hooft anomalies.

We investigate the production of the $\varphi (2170)$ state in the $e^{+}{e}^{-}\to \varphi {\pi }^{+}{\pi }^{-}$ reaction with the effective Lagrangian approach. In addition to the tree level contributions from the $\varphi (1680)$ meson and a possible $X(1750)$ state, we consider also the $K_1\text{−}K\text{−}\overline{K}$ intermediate state process from the perspective of triangular singularity. Based on the one-photon exchange approximation, a pair of $K_1\overline{K}$ mesons was firstly produced, and then the $K_1$ meson subsequently decays into $\varphi$ and $K$, and the $K\overline{K}$ pair produce the ${\pi }^{+}{\pi }^{-}$ through the final state interactions, in which the scalar meson $f_0(980)$ is dynamically generated. We show that the inclusion of the triangle loop diagrams leads to a good description of the new BESIII measurements, especially for the structure of $\varphi (2170)$. This provides a novel interpretation of the $\varphi (2170)$ state, offering new insights into its fundamental nature, which are still unclear. Furthermore, it is found that these measurements on the $e^{+}{e}^{-}\to \varphi {\pi }^{+}{\pi }^{-}$ reaction can be used to determine some of the properties of two $K_1$ mesons with masses around 1613 MeV and 1890 MeV, which are crucial to reproduce the experimental data.

We study heavy-hadron semileptonic decays proceeding via $b\to c$ transition, such as $B\to D^{(*)}\tau {\overline{\nu }}_{\tau }$ and ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c\tau {\overline{\nu }}_{\tau }$. In the heavy-quark limit, where the heavy-quark symmetry holds, we provide a fundamental framework for heavy-quark sum rules among these decays based on the spin decomposition picture. The relation holds directly for the squared amplitudes without requiring phase-space integration. We then apply this relation to reproduce the sum rule among $B\to D^{(*)}\tau {\overline{\nu }}_{\tau }$ and ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c\tau {\overline{\nu }}_{\tau }$. Furthermore, we derive new sum rules for ${\mathrm{\Omega }}_b\to {\mathrm{\Omega }}_c^{(*)}$ transitions and those involving excited states, such as $B\to \{D_0^{*},D_1^{*}\}$ and $B\to \{D_1,D_2^{*}\}$.

We investigate the semileptonic decays ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c{\ell }^{-}{\overline{\nu }}_{\ell }$ (with $\ell =e$, $\mu$, $\tau$) within the framework of perturbative QCD. The six independent ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c$ transition form factors are first calculated in the low-$q^2$ region using the $k_T$ factorization approach. These are then extrapolated to the full physical $q^2$ range via the model-independent $z$ expansion, incorporating recent lattice QCD results at high $q^2$. Based on the obtained form factors, we compute the branching fractions of ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c{\ell }^{-}{\overline{\nu }}_{\ell }$ decays. Our prediction for the lepton flavor universality ratio, ${\mathcal{R}}_{{\mathrm{\Lambda }}_c}=0.29_{-0.11}^{+0.12}$, is slightly larger than the latest experimental measurement. In addition, we analyze several angular observables, including forward-backward asymmetries, lepton-side convexity parameters, and polarization asymmetries. These results offer valuable theoretical input for current and future experimental investigations of semileptonic heavy-to-heavy baryon transitions.

Flavor hierarchies emerge from a single hierarchical parameter $B$ in a one-flavon Froggatt–Nielsen scheme. Fixing $B=5.357$ from charged-lepton ratios ($m_e:m_{\mu }:m_{\tau }\propto {\epsilon }^5:{\epsilon }^2:1$, $\epsilon =1/B$), we reproduce quark masses and Cabibbo-Kobayashi-Maskawa targets at $M_Z$ with $\mathcal{O}(1)$ coefficients. The same $\epsilon$ gives viable lepton textures and benchmarks for $U_{\mathrm{PMNS}}$, $\sum m_{\nu }$, and $m_{\beta \beta }$. Compact correlations ($|V_{us}|,|V_{cb}|,|V_{ub}|,{\theta }_{13}^{\mathrm{PMNS}}$) follow from powers of $\epsilon$.