At sub-eikonal order in the high-energy limit, helicity dependences are generally contained in the transverse components of the gluon field. In the gluon saturation regime, novel helicity effects arise from the nonlinear interaction between the eikonal-order longitudinal gluon field and the sub-eikonal-order transverse gluon field. We derive this saturation induced helicity-dependent field both by solving the classical Yang-Mills equations and through direct diagrammatic calculations. Our analysis shows that the saturation induced helicity effect is intrinsically a two-particle (or multiparticle) correlation effect, rather than a single-particle distribution effect. Furthermore, we evaluate this effect in the context of double-spin asymmetry for incoherent diffractive dijet production in longitudinally polarized electron-nucleus collisions, using a simplified helicity-extended McLerran-Venugopalan model. We find that the saturation induced helicity effect further suppresses the back-to-back peak in the dijet azimuthal angle correlation, with a magnitude comparable to that of the direct helicity effect. This gluon saturation induced helicity effect may offer a novel avenue to probe gluon saturation in polarized collisions.

We describe a numerical method for simulating stochastic fluid dynamics near a critical point in the Ising universality class. This theory is known as model H, and is expected to govern the nonequilibrium dynamics of quantum chromodynamics (QCD) near a possible critical endpoint of the phase transition between a hadron liquid and the quark-gluon plasma. The numerical algorithm is based on a Metropolis scheme, and automatically ensures that the distribution function of the hydrodynamic variables in equilibrium is independent of the transport coefficients and only governed by the microscopic free energy. We verify dynamic scaling near the critical point of a two and three-dimensional fluid and extract the associated critical exponent $z$. We find $z\simeq 3$ in three dimensions, and $z\simeq 2$ for a two-dimensional fluid. In a finite system, we observe a crossover between the mean field value $z=4$ and the true critical exponent $z\simeq 3$ ($z\simeq 2$ in $d=2$). This crossover is governed by the values of the correlation length and the renormalized shear viscosity.

In this paper, a coherent study of the $e^{+}{e}^{-}$ annihilation into $K^{+}{K}^{-}{\pi }^0$, $K_S^0{K}_L^0{\pi }^0$, and $K_S^0{K}^{\pm }{\pi }^{\mp }$ is carried out within the framework of resonance chiral theory. The amplitudes are fixed by fitting to the experimental cross section and invariant mass spectrum. With these amplitudes, one can calculate the hadronic vacuum polarization form factors of these processes. The leading order contributions of $\sigma (e^{+}{e}^{-}\to K\overline{K}\pi )$ to the anomalous magnetic moment of the muon, $(g-2{)}_{\mu }$, is obtained as $a_{\mu }^{\mathrm{HVP},\mathrm{LO}}(e^{+}{e}^{-}\to K\overline{K}\pi )=(3.178\pm 0.071)\times {10}^{-10}$ up to $E_{\mathrm{cm}}=2.3\mathrm{GeV}$.

Any discovery of “new physics” in the neutrino sector will first require a precise baseline prediction of the expected Standard Model cross section. While coherent elastic neutrino-nucleus scattering (CEvNS) experiments are currently statistics limited, upcoming and future experiments at larger scales will be systematics limited. At this point it will be necessary to improve the theoretical predictions to improve the experimental sensitivity. Here we review the calculation of the CEvNS cross section in a consistent theory of hadronic currents and compute the relevant nuclear form factors using the nuclear shell model. The uncertainty on the form factors is explored by repeating the calculation for various shell model interactions and with Skyme-Hartree-Fock evaluations of the weak-charge radii. We then refine the Standard Model predictions for the recent experimental results of the COHERENT experiment. We find that our cross sections are in good agreement with previous predictions, but with significantly smaller uncertainties. Near-future CEvNS experiments will meaningfully benefit from improved predictions through an increased sensitivity to new-physics signals.

We study the transition rates of an atom rotating in a circular orbit, which is coupled with fluctuating electromagnetic fields in vacuum. We find that when the rotational angular velocity exceeds the transition frequency of the atom, the excitation rate can reach the same order of magnitude as the emission rate, even with an extremely low centripetal acceleration resulting from a very small orbital radius. For experimentally accessible centripetal accelerations, the excitation rate of centripetally accelerated atoms can be $10^{272,878}$ times greater than that of linearly accelerated atoms with the same magnitude of acceleration. Our result suggests that the circular version of the Unruh effect can be significant even at very small centripetal accelerations, contrary to the common belief that a large Unruh effect requires large acceleration. This finding sheds new light on the experimental detection of the circular Unruh effect.

Primordial black holes (PBHs) are theorized objects that may make up some—or all—of the dark matter in the Universe. At the lowest allowed masses, Hawking radiation (in the form of photons or electrons and positrons) is the primary tool to search for PBHs. This paper is part of an ongoing series in which we aim to calculate the $\mathcal{O}(\alpha )$ corrections to Hawking radiation from asteroid-mass primordial black holes, based on a perturbative quantum electrodymanics (QED) calculation on Schwarzschild background. Silva et. al. [Phys. Rev. D, 107, 045004 (2023)] divided the corrections into dissipative and conservative parts; this work focuses on the numerical computation of the dissipative $\mathcal{O}(\alpha )$ corrections to the photon spectrum. We generate spectra for primordial black holes of mass $M=1–8\times {10}^{21}{m}_{\text{planck}}$. This calculation confirms the expectation that at low energies, the inner bremsstrahlung radiation is the dominant contribution to the Hawking radiation spectrum. At high energies, the main $\mathcal{O}(\alpha )$ effect is a suppression of the photon spectrum due to pair production (emitted $\gamma \to e^{+}{e}^{-}$), but this is small compared to the overall spectrum. We compare the low-energy tail in our curved spacetime QED calculation to several approximation schemes in the literature, and find deviations that could have important implications for constraints from Hawking radiation on primordial black holes as dark matter.

In this paper, we define absorptive Compton amplitudes, which capture the absorption factor for waves of spin-weight-$s$ scattering in black hole perturbation theory. At the leading order, in the $GM\omega$ expansion, such amplitudes are purely imaginary and expressible as contact terms. Equipped with these amplitudes we compute the mass change in black hole scattering events via the Kosower-Maybee-O’Connell formalism, where the rest mass of a Schwarzschild/Kerr black hole is modified due to absorption of gravitational, electromagnetic, or scalar fields sourced by other compact object. We reproduced the power loss previously computed in the post-Newtonian expansion. The results presented here hold for similar mass ratios and generic spin orientation, while keeping the Kerr spin parameter to lie in the physical region $\chi \le 1$.

We search for solutions describing slowly moving nonrotating black holes in the khronometric model, a modified gravity theory with preferred time (khronon) which arises at low energies from the nonprojectable Hořava gravity. We work in the decoupling limit when the backreaction of the khronon on the metric is small and can be treated perturbatively. For a given black hole velocity, we find a family of solutions parametrized by the khronon propagation speed and regular everywhere outside the universal horizon. On the universal horizon they have a weak singularity manifesting itself in a nonanalyticity of the khronon field. Using the behavior of khronon at infinity we extract the leading black hole sensitivity for which we obtain a simple analytic expression valid throughout the phenomenologically allowed parameter space.

Parity violation in the gravitational sector is a prediction of many theories beyond general relativity. In the propagation of gravitational waves, parity violation manifests by inducing amplitude and/or velocity birefringence between right- and left-circularly polarized modes. We study how the stochastic gravitational-wave background can be used to place constraints on these birefringent effects. We consider two model scenarios, one in which we allow birefringent corrections to become arbitrarily large and a second in which we impose stringent theory priors. In the former, we place constraints on a generic birefringent gravitational-wave signal due to the current nondetection of a stochastic background from compact binary events. We find a joint constraint on birefringent parameters ${\kappa }_D$ and ${\kappa }_z$ of $\mathcal{O}({10}^{-1})$. In the latter scenario, we forecast constraints on parity-violating theories resulting from observations of the future upgraded LIGO-Virgo-KAGRA network as well as proposed third-generation detectors. We find that third-generation detectors will be able to improve the constraints by at least 2 orders of magnitude, yielding new stringent bounds on parity-violating theories. This work introduces a novel and powerful probe of gravitational parity violation with gravitational-wave data.

In the current era of precision cosmology, the persistence of cosmological tensions—most notably the Hubble tension and the $S_8$ tension—challenges the standard lambda-cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) model. To reconcile these tensions via late-time modifications to expansion history, various features, such as phantom crossing in the dark energy equation of state, a negative energy density at high redshifts, etc., are favored. However, these scenarios cannot be realized within the framework of general relativity (GR) without introducing ghost or gradient instabilities. In this work, we investigate a dynamical dark energy scenario within the framework of Horndeski gravity, incorporating nonminimal coupling to gravity and self-interactions. We highlight that the model can exhibit novel features like phantom crossing and negative dark energy densities at high redshifts without introducing any instabilities. For this specific Horndeski model, we perform a comprehensive analysis of the background evolution along with the effects on perturbations, examining observables like growth rate, matter and cosmic microwave background (CMB) power spectrum. To check the consistency of the model with the observational data, we employ Markov chain Monte Carlo analysis using $\mathrm{BAO}/f{\sigma }_8$, supernovae, and CMB data. While the model does not outperform the standard $\mathrm{\Lambda }\mathrm{CDM}$ framework in a combined likelihood analysis, there remains a preference for nonzero values of the model parameters within the data. This suggests that dynamical dark energy scenarios, particularly those with nonminimal couplings, merit further exploration as promising alternatives to GR, offering rich phenomenology that can be tested against a broader range of current and upcoming observational datasets.

Excess of gamma rays around the Galactic center (GC) observed in the Fermi Large Area Telescope (LAT) data is one of the most intriguing features in the gamma-ray sky. The spherical morphology and the spectral energy distribution with a peak around a few GeV are consistent with emission from annihilation of dark matter particles. Other possible explanations include a distribution of millisecond pulsars (MSPs). One of the caveats of the MSP hypothesis is the relatively small number of associated MSPs near the GC. In this paper, we perform a multiclass classification of Fermi-LAT sources using machine learning and determine the contribution from unassociated MSP-like sources near the GC. The spectral energy distribution, spatial morphology, and the source count distribution are consistent with expectations for a population of MSPs that can explain the gamma-ray excess. Possible caveats of the contribution from the unassociated MSP-like sources are discussed.

Spaceborne detectors, including TianQin and the Laser Interferometry Space Antenna (LISA), are tasked with simultaneously observing the Galactic foreground and astrophysical and cosmological stochastic gravitational-wave backgrounds (SGWBs). For the first time, we employ a spaceborne detector network to identify these SGWBs. Specifically, we develop a tailored likelihood for cross-correlation detection with such networks. Combined with the likelihood, we use the simulated datasets of the $\mathrm{TianQin}+\mathrm{LISA}$ network to conduct an analysis for model selection and parameter estimation. In our analysis, we adopt an astrophysical background originating from extragalactic white-dwarf binaries, along with a flat cosmological background associated with the early Universe. Our results indicate that, after four years of operation, the network could detect a single SGWB from either astrophysical or cosmological origins, with an energy density ${\mathrm{\Omega }}_{\mathrm{ast}/\cos }$ (10 mHz) on the order of ${10}^{-12}$, despite the presence of a Galactic foreground. Furthermore, to distinguish the cosmological background from both a Galactic foreground and an extragalactic background produced by white-dwarf binaries, the energy density ${\mathrm{\Omega }}_{\cos }$ should reach around $2\times {10}^{-11}$.

This study investigates the characteristic polarization formation and evolution of vector dark matter (VDM) in the outer halo of galaxies. By employing numerical simulations, we analyze the behavior of VDM under different initial conditions—homogeneous, isotropic, and partially polarized. The simulations solve the Schrödinger-Poisson equations, examining the spin density distribution and its evolution during gravitational collapse and halo formation. Our results reveal that VDM forms halos and central Proca stars from homogeneous and isotropic conditions, with the polarization density fluctuation amplitude mirroring VDM matter density. In scenarios with no initial polarization, spin density remains stable in the halo core but fluctuates in outer regions. Partially polarized initial conditions lead to a conservation of total polarization, with increased core polarization resulting in opposite polarization in the periphery. We examine the novel consequences of the partially polarized state for direct detection of dark photons, i.e., VDM kinetically mixed with ordinary photons.

We study the sensitivity reach to probe the electroweak dipole operators associated with a top quark at a multi-TeV lepton collider. Studying the electroweak dipole operators is strongly motivated by precision physics. The operators exhibit unique chiral structure and can be enhanced with respect to others in theories beyond the Standard Model. We illustrate this point in a strongly coupled composite Higgs model. We find that a high energy ${\mu }^{+}{\mu }^{-}$ collider may offer a unique opportunity to probe the electroweak dipole operators beyond the coverage by the LHC and future hadron colliders. The significant sensitivity is achieved by the leading channel ${\mu }^{+}{\mu }^{-}\to t\overline{t}$ near the threshold, and substantially improved by the novel channel ${\mu }^{+}{\mu }^{-}\to t\overline{t}h$ at high energies. We may be able to reach a new physics scale well above the collider energy for moderate couplings of the Wilson coefficients. Our main conclusions are applicable to future $e^{+}{e}^{-}$ colliders.

Evidence for the existence of a second finite-temperature transition in quantum chromodynamics (QCD) is obtained through the study of center vortex geometry and its evolution with temperature. The dynamical anisotropic ensembles of the Fastsum Collaboration are utilized to conduct a comprehensive analysis at eight temperatures beyond the established chiral transition. Visualizations of the center vortex structure in temporal and spatial slices of the lattice reveal that vortex percolation persists through the chiral transition and ceases at a temperature that is approximately twice the chiral transition temperature $T_c$. This implies that confinement is retained through temperatures up to $T\approx 2T_c$, pointing toward a second transition corresponding to deconfinement. The loss of percolation is quantified by the vortex cluster extent, providing a clear signal for the deconfinement transition. Additional vortex statistics, including temporal correlations, vortex and branching point densities, the number of secondary clusters and vortex chain lengths between branching points, are scrutinized as a function of temperature. All ten measures investigated herein show the characteristics of two transitions in QCD, encompassing the chiral transition at $T_c$ and the deconfinement transition at $T\approx 2T_c$. Performing an inflection point analysis on the vortex and branching point densities produces an estimate of $T_c$ that agrees with the known Fastsum value. By the same procedure, a precise estimate of the deconfinement point is extracted as $T_d=321(6)\mathrm{MeV}$.

Inspired by light-front holography, we compute the pion mass, charge radius, decay constant, electromagnetic form factor and electromagnetic transition form factor. To do so, we model the longitudinal quark dynamics using potentials due to ’t Hooft and to Li and Vary. We find a longitudinal wave function that is rather more peaked about $x\sim 1/2$ than in previous studies. We also explore the strong degeneracy between these two potentials and conclude by noting that one scenario that accords well with the data also maps onto an equation previously noted by Vegh that describes the dynamics of a four-segmented string in three-dimensional anti–de Sitter spacetime.

We present new parton distribution functions (PDFs) at next-to-leading order and next-to-next-to-leading order in perturbative QCD, derived from a comprehensive QCD analysis of high-precision datasets from combined HERA deep-inelastic scattering, the Tevatron, and the LHC. To improve constraints on quark flavor separation, we incorporate Drell-Yan pair production data, which provides critical sensitivity to the quark distributions. In addition, we include the latest $W$ and $Z$ boson production data from the CDF, D0, ATLAS, and CMS collaborations, further refining both quark and gluon distributions. Our nominal QCD fit integrates these datasets and examines the resulting impact on the PDFs and their associated uncertainties. Uncertainties in the PDFs are quantified using the Hessian method, ensuring robust error estimates. Furthermore, we explore the sensitivity of the strong coupling constant, ${\alpha }_s(M_Z^2)$, and proton PDFs in light of the projected measurements from the Electron-Ion Collider, where improvements in precision are expected. The analysis also investigates the effects of inclusive jet and dijet production data, which provide enhanced constraints on the gluon PDF and ${\alpha }_s(M_Z^2)$.

Using $(2712.4\pm 14.3)\times {10}^6\psi (3686)$ events collected by the BESIII detector operating at the BEPCII collider, we present the first observations of the decays ${\chi }_{cJ}(J=0,1,2)\to p\overline{p}\eta {\pi }^0$. Their decay branching fractions are determined to be $\mathcal{B}({\chi }_{c0}\to p\overline{p}\eta {\pi }^0)=(2.42\pm 0.07\pm 0.19)\times {10}^{-4}$, $\mathcal{B}({\chi }_{c1}\to p\overline{p}\eta {\pi }^0)=(1.95\pm 0.05\pm 0.12)\times {10}^{-4}$, and $\mathcal{B}({\chi }_{c2}\to p\overline{p}\eta {\pi }^0)=(1.33\pm 0.05\pm 0.08)\times {10}^{-4}$, where the first uncertainties are statistical and the second systematic.

The Liquid Argon Time Projection Chamber (LArTPC) is a powerful dual calorimeter capable of estimating particle energy from both ionization charge and scintillation light. Our study shows that, due to the recombination luminescence, the LArTPC functions as a self-compensating light calorimeter: the missing energy in the hadronic component is compensated for by the increased luminescence relative to the electromagnetic component. Using 0.5–5 GeV electron neutrino charged current interactions as a case study, we show that good compensation of the electron-to-hadron response ratio ($e/h$) from 1–1.05 can be achieved across a broad range of drift electric fields ($0.2–1.8\mathrm{kV}/\mathrm{cm}$), with better performance for neutrino energies above 2 GeV. This study highlights the potential of light calorimetry in LArTPCs for GeV neutrino energy reconstruction, complementing traditional charge calorimetry. Under ideal conditions of uniform light collection, we show that LArTPC light calorimetry can achieve an energy resolution comparable to the charge imaging calorimetry. Challenges arising from nonuniform light collection in large LArTPCs can be mitigated with a position-dependent light yield correction derived from 3D charge signal imaging.

Static black holes in general relativity modified by a linear scalar coupling to the Gauss-Bonnet invariant always carry hair. We show that the same mechanism that creates the hair makes it incompatible with a cosmological horizon. Other scalar-tensor models do not have this problem when time dependence of the scalar provides a natural matching to cosmology. Scalar-Gauss-Bonnet gravity is particularly rigid, and such a scenario does not help. An extra operator makes the theory behave like the other models, and the cosmological horizon can be accommodated. The hair, however, is drastically altered.