Among the particles being searched for at the LHC beyond the Standard Model are bileptons, which are doubly charged gauge bosons. Bileptons are predicted by several Standard Model extensions, including the so-called 331 models with $\beta =\sqrt{3}$. The minimal formulation of these models is generally plagued by a low-energy Landau pole, which can undermine current predictions for TeV-scale bileptons. We analyze this issue and investigate the possibility to shift the Landau pole at higher energy scales by extending the troublesome minimal 331 models.

Vector-boson fusion productions of new Higgs bosons decaying into pairs of electroweak gauge bosons ($W^{\pm }{W}^{\pm }$, $WZ$, and $ZZ$) are smoking-gun signature of new Higgs bosons in general, and of the Georgi-Machacek (GM) model in particular. Notably, ATLAS has observed a $3.3\sigma$ excess in $W^{\pm }{W}^{\pm }$ at $\approx 450\mathrm{GeV}$ and a $2.8\sigma$ excess in the $WZ$ channel at $\approx 375\mathrm{GeV}$, while compact muon solenoid reported weaker-than-expected limits at these masses. In this article, we consider a generalized version of the GM model without the custodial $SU(2{)}_C$ symmetry in the scalar potential as a minimal model to explain these excesses. In the limit of small mixing among the Higgs bosons, the $W^{\pm }{W}^{\pm }$ and $WZ$ signals can be explained by the doubly and singly charged Higgs bosons originating primarily from the $Y=1$ triplet, while respecting the bounds from $ZZ$ searches. Furthermore, the neutral Higgs boson mostly contained in the $Y=0$ triplet can account for the ($\approx 4\sigma$) excess at $\approx 152\mathrm{GeV}$ in associated diphoton production. Furthermore, the model is consistent with the constraints from vacuum stability and the Standard Model Higgs signal strength measurements, such that it can provide a valid combined explanation for some of the most significant LHC excesses.

We present a momentum-dependent reweighting strategy to extend current LHC di-Higgs analyses within the $\kappa$ framework and Standard Model effective field theory into the bosonic sector of the Higgs effective field theory (HEFT). Unlike Standard Model effective field theory, where symmetry constraints tightly correlated multi-Higgs processes, HEFT allows for a broader range of momentum-dependent deviations that can substantially impact di-Higgs kinematics and offer a powerful probe of nonlinear Higgs dynamics. We generalize the interpretation of existing experimental analyses by integrating HEFT operators up to chiral dimension 4 into differential Monte Carlo reweighting. We quantify the sensitivity to representative HEFT operators using multidimensional likelihoods for Run 3 and project the reach at the high-luminosity LHC. Particular emphasis is placed on how different exclusive final states, such as $b\overline{b}b\overline{b}$ and $b\overline{b}\gamma \gamma$, respond to momentum enhancements and how their complementary event selections drive exclusion limits. We further explore how rare final states, especially four-top production, can provide orthogonal constraints on HEFT-induced modifications, thereby enhancing global sensitivity to new physics effects in the Higgs sector.

Neutrino tensor interactions have gained prominence in the study of coherent elastic neutrino-nucleus scattering ($\mathrm{CE}\nu \mathrm{NS}$) recently. We perform a systematical examination of the nuclear effect, which plays a crucial role in evaluating the cross section of $\mathrm{CE}\nu \mathrm{NS}$ in the presence of tensor interactions. Our analysis reveals that the $\mathrm{CE}\nu \mathrm{NS}$ cross section induced by tensor interactions is not entirely nuclear spin suppressed and can be enhanced by a few orders of magnitude compared to the conventional studies. The neutrino magnetic moment induced by the loop effect of tensor interactions is also taken into account due to its sizable contribution to the $\mathrm{CE}\nu \mathrm{NS}$ cross section. We also employ data from the COHERENT experiment and recent observations of solar ${}^8\mathrm{B}$ neutrinos from dark matter direct detection experiments to scrutinize the parameter space of neutrino tensor interactions.

The geometry of center vortices is studied in the novel lattice-artefact phase that appears with staggered fermions to elucidate any insight provided by the center-vortex degrees of freedom. For various numbers of fermion flavors, the single-site shift symmetry of the staggered-fermion action is broken in a finite region of the $(\beta ,m)$ phase space. Simulations are performed with six degenerate fermion flavors and a range of $\beta$ values that span the phase boundary. Center vortices are demonstrated to capture the broken shift symmetry that manifests in the unphysical phase. This persists at the level of each individual plaquette orientation, where it is revealed that only the plaquettes that span the broken dimension are affected. Several bulk center-vortex quantities, including the vortex and branching point densities, are considered to highlight other aspects of vortex geometry sensitive to the unphysical phase. A slight preference for the plaquettes affected by the broken shift symmetry to be pierced by a vortex is observed. This translates also to a greater branching point density in three-dimensional slices that span the broken dimension. Combined, these findings provide a novel characterization of the unphysical phase in terms of the fundamental center degrees of freedom.

This study investigates finite-volume effects in physical processes that involve the combination of long-range hadronic matrix elements with electroweak loop integrals. We adopt the approach of implementing the electroweak part as the infinite-volume version, which is denoted as the ${\mathrm{EW}}_{\infty }$ method in this work. A general approach is established for correcting finite-volume effects in cases where the hadronic intermediate states are dominated by either a single particle or two particles. For the single-particle case, this work derives the infinite volume reconstruction method from a new perspective. For the two-particle case, we provide the correction formulas for power-law finite-volume effects and unphysical terms with exponentially divergent time dependence. The finite-volume formalism developed in this study has broad applications, including the QED corrections in various processes and the two-photon exchange contribution in $K_L\to {\mu }^{+}{\mu }^{-}$ or $\eta \to {\mu }^{+}{\mu }^{-}$ decays.

We study the generalized charm susceptibilities in $2+1$ flavor QCD on the lattice at several lattice spacings. We show that, below the chiral crossover, these susceptibilities are well described by the hadron resonance gas (HRG) model if charmed hadrons not listed in tables of the Particle Data Group are included. However, the HRG description abruptly breaks down just above the chiral crossover. To understand this, we use a model for the charm pressure in which it is expressed as the sum of partial pressures from charmed baryons, charmed mesons, and charm quarks. We present continuum estimates of these partial pressures and find that, while the partial pressures of charmed mesons and baryons drop below their respective HRG predictions, the charm quark pressure becomes nonzero above the chiral crossover.

In a constituent quark model, a hidden charmed tetraquark is assumed consisting of a $cq$ diquark and an $\overline{c}\overline{q}$ antidiquark or vice versa. The Semay-Silvestre-Brac potentials are employed to calculate the masses of $cq$ ($\mathrm{q}=\mathrm{u}$, d) diquarks. The mass of the $cq$ diquark or $\overline{c}\overline{q}$ antidiquark with spin-0 is predicted with $\sim 2175\mathrm{MeV}$, and the spin-1 one is predicted with $\sim 2220\mathrm{MeV}$. The masses of hidden charmed tetraquarks from $1S$ to $2P$ excitations are systematically calculated in terms of the same potentials. It is found that the mass of hidden charmed tetraquarks without radial excitation grows higher in $1^{+-},1^{++},1^{--},0^{-+},0^{--},1^{-+},\dots$ sequence, and the tetraquarks with exotic $J^{PC}=0^{--},1^{-+}$ have higher masses. The hidden charmed tetraquarks with radial excitations have masses greater than 4300 MeV. The $1S-1P$ and $1S-2S$ mass splittings of the hidden charmed tetraquarks are about 390–400 and 550–570 MeV, respectively, which are about 50 and 40 MeV smaller than those of normal charmoniums. The $1P-2P$ and $2S-2P$ mass splittings are similar to those for conventional $c\overline{c}$ charmonium mesons. Based on our predicted masses for hidden charmed tetraquarks, some XYZ exotics are analyzed and tentatively assigned. $X^{*}(3860)$ is possibly the $0^{++}$ tetraquark. $Z_c(3900)$ and $X(3940)$ are possibly the $1^{+-}$ tetraquarks, and $X(3872)$ is possibly a $1^{++}$ tetraquark. $X(4250)$ may be a $0^{-+}$, $0^{++}$, or $1^{-+}$ tetraquark, $X(4240)$ may be a $0^{--}$ tetraquark. With radial excitations, $X(4350)$ may be a $0^{++}$ tetraquark, $Z_c(4430)$ may be a $1^{+-}$ tetraquark, $X(4630)$ may be a $0^{-+}$ or $1^{-+}$ tetraquark, and $X(Y)(4660)$ may be the $1^{--}$ tetraquark. $Y(4008)$ or $Y(4390)$ seems impossible to be the $1^{--}$ tetraquark. In experiments, for the identification of a normal charmonium or a charmonium-like exotic, it is also important to take into account the mixing of normal charmoniums with hidden-flavor charmonium-like exotics.

The absence of definitive results for WIMP dark matter has sparked growing interest in alternative dark matter candidates, such as axions and axionlike particles (ALPs), which also provide insight into the strong CP problem. The Mitchell Institute Neutrino Experiment at Reactor (MINER), conducted at the Nuclear Science Center of Texas A&M University, investigated ALPs near a 1 MW h TRIGA nuclear reactor core, positioned approximately 4 m away. This experiment employed cryogenic sapphire detectors with a low detection threshold ($\approx 100\mathrm{eV}$), equipped with a transition edge sensor capable of detecting athermal phonons. Due to the low-background environment, we were able to exclude ALPs with axion-photon coupling and axion-electron coupling as small as $g_{a\gamma \gamma }={10}^{-5}$ and $g_{aee}={10}^{-7}$, respectively. Energy depositions below 3 keV were not considered and remain blinded for our coherent elastic neutrino-nucleus scattering analysis. This is the first result demonstrating the MINER experiment’s potential to probe low-mass ALPs, enabled by its low-threshold detector and proximity to a reactor.

${\mathrm{JSNS}}^2$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment searching for sterile neutrinos through the observation of ${\overline{\nu }}_{\mu }\to {\overline{\nu }}_e$ appearance oscillations, using neutrinos produced by muon decay-at-rest. A key aspect of the experiment involves accurately understanding the neutrino flux and the quantities of pions and muons, which are progenitors of (anti)neutrinos, given that their production rates have yet to be measured. We present the first electron-neutrino flux measurement using ${}^{12}\mathrm{C}({\nu }_e,e^{-}{)}^{12}{\mathrm{N}}_{\mathrm{g}.\mathrm{s}.}$ reaction in ${\mathrm{JSNS}}^2$, yielding a flux of $(6.7\pm 1.6(\mathrm{stat})\pm 1.7(\mathrm{syst}))\times {10}^{-9}{\mathrm{cm}}^{-2}{\mathrm{proton}}^{-1}$ at the ${\mathrm{JSNS}}^2$ detector location, located at 24 meters distance from the mercury target. This flux measurement is consistent with predictions from simulations based on hadron models.

We propose a novel approach to measure the spin polarization of protons produced in electron-positron collisions. Using existing tracking devices and supporting structure material, general-purpose spectrometers can be utilized as a large-acceptance polarimeter without a hardware upgrade. With the proposed approach, the spin polarization of protons can be revealed, providing a complementary and accurate description of the final-state particles. This could have far-reaching implications, such as enabling the complete determination of the nucleon timelike electromagnetic form factors.

Emergent modified gravity provides a covariant, effective framework for obtaining spherically symmetric black hole solutions in models of loop quantum gravity with scale-dependent holonomy modifications. Exact solutions for vacuum black holes in the presence of a cosmological constant are derived here and analyzed in four different gauges, explicitly related to one another by standard coordinate transformations. The global structure is obtained by gluing space-time regions corresponding to the gauge choices, reconstructing a nonsingular wormhole space-time for an arbitrary scale-dependent holonomy parameter. This outcome demonstrates the robustness of black-hole models with covariant holonomy modifications under quantization ambiguities. Compared with previous constructions, full covariance of the resulting space-time models as derived here implies subtle new effects and leads to a novel understanding of the parameters in holonomy modifications, distinguishing a constant holonomy length from a possibly scale-dependent function that may change coefficients of holonomy terms. New physical results are obtained for instance in the context of a nontrivial zero-mass limit of holonomy-modified space-times. The existence of a consistent effective space-time structure implies various novel aspects of a net gravitational stress-energy and related thermodynamical properties.

A quantum master equation describing the stochastic dynamics of a quantum massive system interacting with a quantum gravitational field is useful for the investigation of quantum gravitational and quantum informational issues such as the quantum nature of gravity, gravity-induced entanglement, and gravitational decoherence. Studies of the decoherence of quantum systems by an electromagnetic field shows that a lower temperature environment is more conducive to successful quantum information processing experiments. Likewise, the quantum nature of (perturbative) gravity is far better revealed at lower temperatures than high, minimizing the corruptive effects of thermal noise. In this work, generalizing earlier results of the Markovian ABH master equation [Classical Quantum Gravity 30, 165007 (2013); Phys. Rev. Lett. 111, 021302 (2013)], which is valid only for high temperatures, we derive a non-Markovian quantum master equation for the reduced density matrix, and the associated Fokker-Planck equation for the Wigner distribution function, for the stochastic dynamics of two masses following quantum trajectories, interacting with a graviton field, including the effects of graviton noise, valid for all temperatures. We follow the influence functional approach exemplified in the derivation of the non-Markovian Hu-Paz-Zhang master equation [Phys. Rev. D45, 2843 (1992); Phys. Rev. D 49, 6612 (1994)] for quantum Brownian motion. We find that in the low temperature limit, the off-diagonal elements of the reduced density matrix decrease in time logarithmically for the zero temperature part and quadratically in time for the temperature-dependent part, which is distinctly different from the Markovian case. We end with a summary of our findings and a discussion on how this problem studied here is related to the quantum stochastic equation derived in [Phys. Rev. D 74, 024017 (2006)] for gravitational self force studies, and to quantum optomechanics where experimental observation of gravitational decoherence and entanglement may be implemented.

The behaviors of the spherically symmetric modes for a massless minimally coupled scalar field are investigated for the Unruh state for Schwarzschild spacetime and the in vacuum state for a spacetime in which a null shell collapses to form a Schwarzschild black hole. In both cases, there are two different sets of solutions to the mode equation that make up the state. For both spacetimes, one set of modes oscillates forever with no damping of the oscillations and the other set approaches zero at late times. The difference between a mode that oscillates forever in the null-shell spacetime and the corresponding mode for the Unruh state at late times vanishes as a power law in time. The modes that approach zero at late times also vanish as a power law in time. In all cases, the power-law damping is preceded by a period of oscillations that appear to be due to quasinormal modes.

The original Kerr theorem provides the foundation for Kerr-Schild transformations by classifying all shear-free and geodesic null congruences in flat spacetime; the key ingredient of the Kerr-Schild ansatz. However, due to the high level of degeneracy of the outcome, it is often less practical than its symmetric refinements, which may single out congruences leading to physically significant spacetimes by imposing relevant symmetries. An illustrative example is the stationary axisymmetric version of Kerr theorem, which has been shown to lead directly and uniquely to the Kerr black hole in vacuum. In this work, we propose a new symmetric refinement of the Kerr theorem by boosting the stationary symmetry into its ultrarelativistic limit to achieve invariance under null translations, while keeping axisymmetry. Under these assumptions, the classification yields only two distinct congruences. The first congruence is covariantly constant and, through the Kerr-Schild ansatz, evidently yields an axisymmetric $\mathit{pp}$-wave. The vacuum axisymmetric profile of this $\mathit{pp}$-wave displays a logarithmic dependence on the polar radius, characteristic of the exterior gravitational field of the Bonnor light beam, and includes as a special case the Aichelburg-Sexl ultrarelativistic limit of the Schwarzschild black hole. The Kerr-Schild transformation of the second congruence gives rise to a nontrivial vacuum solution recently reported in [Phys. Rev. D 112, 024020 (2025)]. Using circularity and appropriately fixing the reparametrization invariance of the orthogonal manifold to the Killing fields, we show that the latter solution corresponds to the well-known Taub-NUT spacetime with planar topology. These results emphasize how symmetry-based refinements of the Kerr theorem constitute a powerful tool to constructing physically essential spacetimes.

The ringdown phase of a binary black-hole merger encodes key information about the remnant properties and provides a direct probe of the strong-field regime of general relativity. While quasinormal mode frequencies and damping times are well understood within black-hole perturbation theory, their excitation amplitudes remain challenging to model, as they depend on the merger phase. The complexity increases for precessing black-hole binaries, where multiple emission modes can contribute comparably to the ringdown. In this paper, we investigate the phenomenology of precessing binary black-hole ringdowns using the SXS numerical relativity simulations catalog. Precession significantly impacts the ringdown excitation amplitudes and the related mode hierarchy. Using Gaussian process regression, we construct the first fits for the ringdown amplitudes of the most relevant modes in precessing systems.

We present a comprehensive analysis of the preheating dynamics and associated gravitational wave signatures in the Higgs-$R^2$ inflationary model. Using lattice simulations, we investigate the postinflationary evolution of the system across the parameter space, covering both the Higgs-like and $R^2$-like scenarios. We demonstrate that the efficiency of preheating is significantly dependent on the nonminimal coupling parameter $\xi$. As the $\xi$ parameter increases, moving from the $R^2$-like regime to the Higgs-like regime, we observe more efficient preheating. Through detailed numerical computations, efficient preheating is shown to lead to stronger gravitational wave production. The amplitude of the gravitational wave spectrum varies by several orders of magnitude as we move from the $R^2$-like regime to the Higgs-like regime. The resultant gravitational wave signatures can serve as a potential observational probe to distinguish between different parameter regimes of the Higgs-$R^2$ model.

Based on the minimal $U(1{)}_X$ extended Standard Model, we explore cosmic inflation where the $U(1{)}_X$ Higgs field serves as the inflaton. We demonstrate that a stiff era with an equation of state $w>1/3$ can emerge during the inflaton’s oscillatory phase after inflation, driven by the Coleman-Weinberg potential of the inflaton, arising due to radiative corrections. This leads to significant modulation and enhancement of the irreducible stochastic gravitational wave (GW) background from inflation, deviating from the conventional scale-invariant spectrum. Such a distinct GW spectrum could be detectable by next-generation GW interferometer missions, such as U-DECIGO. In our framework, the GW spectrum depends on the $U(1{)}_X$ gauge coupling and the mass of the $U(1{)}_X$ gauge boson ($Z^{\prime }$). As a result, future GW observations and $Z^{\prime }$ boson resonance searches at high-energy collider experiments are complementary to one another.

Neutron stars (NSs) probe the high-density regime of the nuclear equation of state (EOS). However, inferring the EOS from observations of NSs is a computationally challenging task. In this work, we efficiently solve this inverse problem by leveraging differential programming in two ways. First, we enable full Bayesian inference in under one hour of wall time on a GPU by using gradient-based samplers, without requiring pretrained machine learning emulators. Moreover, we demonstrate efficient scaling to high-dimensional parameter spaces. Second, we introduce a novel gradient-based optimization scheme that recovers the EOS of a given NS mass-radius curve. We demonstrate how our framework can reveal consistencies or tensions between nuclear physics and astrophysics. First, we show how the breakdown density of a metamodel description of the EOS can be determined from NS observations. Second, we demonstrate how degeneracies in EOS modeling using nuclear empirical parameters can influence the inverse problem during gradient-based optimization. Looking ahead, our approach opens up new theoretical studies of the relation between NS properties and the EOS, while effectively tackling the data analysis challenges brought by future detectors.

The branching fractions of the axial vector meson decays $f_1\to a_0\pi ,\pi \pi \eta$, $f_1\to \rho \pi ,\pi \pi \pi$, and $f_1\to KK\pi$ are calculated in the standard $U(3)\times U(3)$ quark Nambu–Jona-Lasinio model. The intermediate channels with the states $a_0(980)\pi$ and $f_0(500)\eta$ are taken into account in the decay $f_1\to \pi \pi \eta$. In the case of the scalar mesons, the $\overline{q}q$ representation as a chiral symmetric partners of the pseudoscalar mesons is used. It is shown that the decays $f_1\to \rho \pi$ and $f_1\to 3\pi$ occur due to the mass difference of the $u$ and $d$ quarks. All the results are obtained without using any additional arbitrary parameters and are in satisfactory agreement with the known experimental data.