We investigate the nonlinear Compton photon source for upcoming laser-particle experiments in the collision scenario of high-energy electron beams and relativistic laser pulses. The stronger laser field could not only improve the scattering probability but also induce broader photon beam divergence. To maximize the photon flux in a realistic narrow angular acceptance, we show that a balance must be met for the laser intensity to boost the scattering probability and simultaneously confine its beam divergence. For the currently experiment-concerned 10 GeV energy regime, the balanced laser intensity locates in the intermediate intensity regime of $\xi \sim O(1)$. In these regimes of laser intensity and electron energy, the accepted photons within a relatively narrow acceptance are highly polarized in the state closely relating to the polarization of the laser pulse, which actually implies a potential route to finely control the photon polarization via the laser polarization.

Hadronization models used in event generators are physics-inspired functions with many tunable parameters. Since we do not understand hadronization from first principles, there have been multiple proposals to improve the accuracy of hadronization models by utilizing more flexible parametrizations based on neural networks. These recent proposals have focused on the kinematic properties of hadrons, but a full model must also include particle flavor. In this paper, we show how to build a deep learning-based hadronization model that includes both kinematic (continuous) and flavor (discrete) degrees of freedom. Our approach is based on generative adversarial networks and we show the performance within the context of the cluster hadronization model within the herwig event generator.

Mirror matter from the dark hidden sector with the same particle content and gauge interactions as in the standard model is still an interesting candidate for dark matter. Several experiments on the search for positronium and neutron oscillations into their mirror partner have been conducted recently. In this work, we consider the transitions $K^0-K_m^0$ of a neutral kaon into a hidden mirror kaon. It is shown that their probability can be probed with the sensitivity of $P(K^0-K_m^0)\lesssim {10}^{-7}$ from the search for missing-energy events in the NA64 experiment at the CERN SPS with $\sim {10}^{11}$ $K^{+}$ on target. This would result in a limit on the $K^0-K_m^0$ mixing parameter much stronger than the similar bound estimated from the cosmological considerations.

We investigate the global structure of the gauged two-higgs-doublet model (G2HDM), a framework that extends the Standard Model by introducing a dark sector governed by the gauge symmetry $U(1{)}_X\times SU(2{)}_H$. The full gauge symmetry of the theory, including the visible sector, is given by the universal covering group $\tilde{G}=U(1{)}_Y\times SU(2{)}_L\times SU(3{)}_C\times U(1{)}_X\times SU(2{)}_H$. However, the true gauge group may instead be a quotient $G=\tilde{G}/\mathrm{\Gamma }$, where $\mathrm{\Gamma }$ is the center of $\tilde{G}$ or a subgroup thereof, leading to different global structures that cannot be distinguished by local experiments. We explore the physical implications of these global structures, analyzing their effects on Wilson, ’t Hooft, and dyonic line operators, as well as the periodicity of the $CP$-violating $\theta$ angles associated with each group factor. Furthermore, we determine the minimal electric and magnetic charges that arise after electroweak symmetry breaking, highlighting their dependence on the choice of $\mathrm{\Gamma }$. These findings provide a systematic characterization of the G2HDM’s global properties and their potential phenomenological consequences.

We study the dynamics of domain walls formed through the spontaneous breaking of an approximate ${\mathbb{Z}}_2$ symmetry in a scalar field, focusing on their collapse under the influence of quantum and thermal corrections induced by a ${\mathbb{Z}}_2$-violating Yukawa coupling to Dirac fermions in the thermal bath. The thermal effects make the potential bias between the true and false vacua dependent on the temperature and may lead to notable variations in the annihilation temperature of domain walls, in addition to the shift caused by temperature-independent quantum corrections. These modifications could substantially alter the gravitational wave spectrum produced by collapsing domain walls, potentially providing observable signatures for future gravitational wave detection experiments.

In lattice field theory, field sparsening aims to replace quantum fields, or objects constructed from them, with approximations that preserve the appropriate symmetries and maintain many aspects of the physics that the fields determine. For example, an effective sparsening of a quark propagator provides an efficient map from a quark propagator on a fine lattice geometry to a quark propagator defined on a coarser geometry in order to reduce storage and computational costs of subsequent calculational stages while maintaining long-distance correlations and corresponding low-energy physical information. Previous studies have focused on decimating lattice sites or randomly sampling lattice sites to reduce the size of the propagator and subsequent costs of Wick contractions. Here, we extend the study of sparsening to incorporate covariant averaging of spatial sites and examine the effects on two-point and three-point correlation functions involving various hadrons. We find that sparsening is most effective in reproducing the unsparsened versions of these correlation functions when weighted covariant-averaging is sequentially applied many times.

A key search mode for axionlike particles (ALPs) that couple to charm quarks is $J/\psi \to \gamma a$. Here we calculate the form factor that allows the rate of this process to be determined using lattice QCD for the first time. Our calculations use the relativistic highly improved staggered quark (HISQ) action for the valence charm quarks on gluon field configurations generated by the MILC collaboration that include $u$, $d$, $s$ and $c$ HISQ quarks in the sea at four values of the lattice spacing and both unphysical and physical sea quark masses. We determine the form factor as a function of ALP mass with an uncertainty of less than 2% across our full range of ALP masses from zero up to 95% of the $J/\psi$ mass. This represents a substantial improvement in accuracy of the theoretical picture of this decay compared to the previously used tree-level and $\mathcal{O}({\alpha }_s)$ perturbation theory. We use our form factor to determine constraints on ALP masses and couplings to charm quarks and photons in several different scenarios using recent experimental data from BESIII. Our calculation paves the way for further lattice QCD input on new physics constraints from radiative decays.

In the absence of impurities and boundary effects, first order phase transitions are initiated by the nucleation of critical bubbles. In thermally driven transitions many systems can remain metastable for an extended time, possibly tens of orders of magnitude longer than typical microscopic timescales. In standard Markov chain Monte Carlo simulations of these systems the probability of critical bubbles can be too suppressed for the transition to happen in any practical simulation time. The computation can be accelerated by using modified sampling methods, for example multicanonical or Wang-Landau sampling. However, even using these methods, there remains a condensation barrier which dramatically reduces the efficiency at large volumes. We present a novel sampling method, the method of expanded ensembles, which very effectively circumvents the condensation barrier and enables efficient simulations at large volumes.

Distillation is a quark-smearing method for the construction of a broad class of hadron operators useful in lattice QCD computations and defined via a projection operator into a vector space of smooth gauge-covariant fields. A new orthonormal basis for this space is constructed which builds in locality. This basis is useful for the construction of stochastic methods to estimate the correlation functions computed in Monte Carlo calculations relevant for hadronic physics.

The Born-Oppenheimer approximation is one of the very successful tools for solving the hydrogen atom problem. The experimental discovery of hidden heavy flavor tetraquarks $Q\overline{Q}q\overline{q}$ ($Q=c$, $b$ and $q=u$, $d$, $s$) provides great possibilities for the hydrogen-bond-like structure of the quantum chromodynamics version. In this work, considering that the colors of $Q\overline{Q}$ and $q\overline{q}$ are both 8, the tetraquark $Q\overline{Q}q\overline{q}$ system is formed by color coupling $8\otimes 8\to 1$. In order to study the mass splitting caused by the color-spin hyperfine interaction, the color-spin basis vectors of the $S$-wave tetraquark states are appropriately constructed. Then, we use the Born-Oppenheimer approximation to calculate the mass spectra of the $S$-wave hidden heavy flavor tetraquark states. The results show that some of the hidden heavy flavor exotic hadrons discovered experimentally can be well explained as this type of hydrogen-bond-like tetraquark structure. In addition, some candidates for tetraquark bound states are predicted and may be compact tetraquark states.

Initiated by the recent observation of a flattened line shape of $I{J}^{PC}=00^{-+}$ around 1.4–1.5 GeV in the $K_S{K}_S{\pi }^0$ invariant mass spectrum by BESIII, we make a systematic partial wave analysis of $J/\psi \to \gamma {\eta }_X\to \gamma K\overline{K}\pi$ based on an isobaric approach. We demonstrate that in the scenario of the first radial excitations of the isoscalar pseudoscalar from the $K\overline{K}\pi$ threshold to about 1.6 GeV the non-trivial $K_S{K}_S{\pi }^0$ invariant mass spectrum can be explained by the coupled-channel effects with the presence of the triangle singularity mechanism. It shows that a combined fit of the Dalitz plots, three-body and two-body spectra can be achieved, which suggests that the one-state solution around 1.4–1.5 GeV proposed before still holds well. In particular, we show that the coupled-channel effects between the three important quasi-two-body decay channels, $K^{*}\overline{K}+\mathrm{c}.\mathrm{c}.$, $\kappa \overline{K}+\mathrm{c}.\mathrm{c}.$ and $a_0(980)\pi$, can be well described by taking into account the one-loop corrections in the isobaric approach. This is because the isoscalar pseudoscalar states are coupled to the $K^{*}\overline{K}+\mathrm{c}.\mathrm{c}.$ and $a_0(980)\pi$ ($\kappa \overline{K}+\mathrm{c}.\mathrm{c}.$) channels via the $P$ and $S$ waves, respectively. As a consequence, the coupled-channel effects can be largely absorbed into the redefinition of the tree-level effective couplings with the transition amplitudes computed to the order of one-loop corrections. Then, the coupled-channel effects can be estimated by the contributions from the one-loop rescattering amplitudes in comparison with the tree-level ones, where we find that the rescattering contributions from the $P$ wave into the $S$ wave, or vice versa, are apparently suppressed in the kinematic region near threshold.

The infrared regularized and the large $N_c$ standard U(3) chiral perturbation theory (ChPT) predicted scaling of the pion, kaon decay constants $f_{\pi }$, $f_K$, and $M_{\eta }^2=m_{\eta }^2+m_{{\eta }^{\prime }}^2$, has been used in the renormalized $2+1$ flavor quark-meson (RQM) model to find a consistent path to the chiral limit as the $\pi$ and $K$ meson masses approach zero. Using the inputs from the above two prescriptions of the ChPT, the Columbia plots are drawn and compared in the $m_{\pi }-m_K$ and the light strange quark mass $m_{ud}-m_s$ planes, free from any ambiguity or heuristic adjustment in the model parameter fixing away from the physical point. The on-shell renormalization of the parameters and consistent treatment of the divergent quark one-loop vacuum fluctuations in the RQM model make the axial $U_A(1)$ anomaly significantly stronger, and the light (strange) explicit chiral symmetry breaking strength becomes weaker by a small (relatively large) amount. The first-order chiral transition region in the $m_{\pi }-m_K$ and $\mu -m_K$ planes of the Columbia plots generated using the inputs from both versions of the ChPT increases due to the above novel features of the RQM model. Comparing our results (in the presence of the axial $U_A(1)$ anomaly) regarding the softening effect of the quark one-loop vacuum fluctuations on the chiral transition, it looks overestimated in a recent functional renormalization group study. The $U_A(1)$ symmetry and the $S{U}_A(3)$ chiral symmetry restoration in the chiral limit takes place at the same transition temperature.

We study the femtoscopic correlation functions of meson-baryon pairs in the strangeness $S=-1$ sector, employing unitarized s-wave scattering amplitudes derived from the chiral Lagrangian up to next-to-leading order. For the first time, we deliver predictions on the ${\pi }^{-}\mathrm{\Lambda }$ and $K^{+}{\mathrm{\Xi }}^{-}$ correlation functions which are feasible to be measured at the Large Hadron Collider. We also demonstrate that the employed model is perfectly capable of reproducing the $K^{-}p$ correlation function data measured by the same collaboration, without the need to modify the coupling strength to the ${\overline{K}}^{0}n$ channel, as has been recently suggested. In all cases, the effects of the source size on the correlation are tested. In addition, we present detailed analysis of the different coupled-channel contributions, together with the quantification of the relative relevance of the different terms in the interaction. These calculations require the knowledge of the so-called production weights, for which we present two novel methods to compute them.

We investigate the semileptonic decays of charmed mesons to light vector mesons within the framework of light-cone sum rules. Our calculation is performed at leading order in quantum chromodynamics (QCD) coupling, incorporating contributions up to twist-five accuracy from both two-particle and three-particle light-cone distribution amplitudes. Transition form factors are predicted twist by twist to assess the convergence property of the operator product expansion. It is verified that the twist-four and twist-five contributions are indeed negligible for all the decays under consideration. Twist-three dominance is observed for some of the form factors, subject to heavy quark effective field theory interpretation. Branching ratios for the decays $D^{+}\to {\rho }^0{\ell }^{+}{\nu }_{\ell }$, $D_s^{+}\to K^{*0}{\ell }^{+}{\nu }_{\ell }$, $D^0\to K^{*-}{\ell }^{+}{\nu }_{\ell }$ and $D^{+}\to {\overline{K}}^{*0}{\ell }^{+}{\nu }_{\ell }$ are obtained, and a 10%–20% discrepancy from experimental measurements is found. Our finding indicates that the resonant-width and nonresonant QCD backgrounds effects should be potentially significant, implying the necessity to further implement their contributions in future precision studies of the semileptonic charm decays.

We present the first detailed study of Standard Model neutrino tridents involving tau leptons at the near detectors of accelerator neutrino facilities. The rates of these processes were previously thought to be negligible, even at future facilities. Our full $2\to 4$ calculation, including both coherent and incoherent scatterings, reveals that the DUNE near detector could observe a considerable number of tau tridents—an important background to new physics searches. We identify promising kinematic features that may allow distinction of tau tridents from the usual neutrino charged-current background at DUNE, and thus establish the observation of tau tridents for the first time. We also comment on the detection prospects at other accelerator and collider neutrino experiments.

We report an updated neutrino mixing angle of ${\theta }_{13}$ obtained from a complete data sample of the RENO experiment. The experiment has measured the amplitude and frequency of reactor electron antineutrino (${\overline{\nu }}_e$) oscillations at the Hanbit nuclear power plant, Younggwang, Korea, since August 2011. As of March 2023, the data acquisition was completed after a total of 3800 live days of detector operation. The observed candidates via inverse beta decay with the neutron capture on the gadolinium channel are 1,211,995 (144,667) in the near (far) detector. Based on an observed energy-dependent reactor neutrino disappearance, neutrino oscillation parameters of ${\theta }_{13}$ and $|\mathrm{\Delta }{m}_{ee}^2|$ are precisely determined as ${\sin }^{2}2{\theta }_{13}=0.0920_{-0.0042}^{+0.0044}(\mathrm{stat}{)}_{-0.0041}^{+0.0041}(\mathrm{syst})$ and $|\mathrm{\Delta }{m}_{ee}^2|=[2.57_{-0.11}^{+0.10}(\mathrm{stat}{)}_{-0.05}^{+0.05}(\mathrm{syst})]\times {10}^{-3}{\mathrm{eV}}^2$. Compared to the previously published RENO results, the precision is improved from 7.5% to 6.4% for ${\sin }^{2}2{\theta }_{13}$ and from 5.2% to 4.5% for $|\mathrm{\Delta }{m}_{ee}^2|$. The statistical error of the measurement has reached our goal and is hardly improved with additional data taking.

We investigate the Krylov complexity of thermofield double states in systems with mixed phase space, uncovering a direct correlation with the Brody distribution, which interpolates between Poisson and Wigner statistics. Our analysis spans two-dimensional random matrix models featuring (I) GOE-Poisson and (II) GUE-Poisson transitions and extends to higher-dimensional cases, including a stringy matrix model (GOE-Poisson) and the mass-deformed SYK model (GUE-Poisson). Krylov complexity consistently emerges as a reliable marker of quantum chaos, displaying a characteristic peak in the chaotic regime that gradually diminishes as the Brody parameter approaches zero, signaling a shift toward integrability. These results establish Krylov complexity as a powerful diagnostic of quantum chaos and highlight its interplay with eigenvalue statistics in mixed phase systems.

We investigate gluonic contributions to the pion beyond the valence sector using basis light-front quantization (BLFQ) and the Minkowski Bethe-Salpeter equation (BSE). Starting from the valence light-front wave function, we construct the quark-antiquark-gluon component and derive the corresponding quark and gluon parton distribution functions (PDFs). A proposed operator generating this higher Fock sector is validated against BLFQ and BSE results. We identify dynamical chiral symmetry breaking through enhanced spin-flip transitions, which amplify the low-$x$ quark PDF and underlie the $\pi \text{−}\rho$ mass splitting. The framework also reveals the impact of a vanishing gluon mass on the gluon PDF, highlighting sensitivity to nonperturbative gluon dynamics.

In this paper, we investigate quasinormal modes in holographic QCD models from the perspective of the WKB approximation. We derive the generalized Bohr-Sommerfeld quantization rules for quasistationary states in holographic QCD models. As a simple application of these formulas, we compute the quasinormal modes of scalar and vector fields in the soft-wall model, where an analytic expression for the real part of the frequency can be found in the low-temperature regime. Additionally, this study provides useful insights into the dissociation process in holographic QCD models.

The quantum null energy condition (QNEC) is a lower bound on the expectation value of the null-null component of the energy-momentum tensor in terms of null variations of the entanglement entropy. A stronger version of the QNEC (the primary QNEC) is expected to hold in $1+1$ dimensional conformal field theories (CFT). QNEC has been shown to impose nontrivial quantum thermodynamic restrictions on irreversible entropy production in quenches in $1+1$ dimensional holographic CFTs. It is therefore natural to study if QNEC imposes similar bounds in other quench setups. In this paper we study QNEC in the Calabrese-Cardy global and local joining quenches using standard CFT techniques. In the global quench we show that the primary QNEC must hold at sufficiently early times and find that it imposes bounds on the four point correlators of twist fields in a boundary state. This is a constraint on the set of boundary states that satisfy the primary QNEC. Furthermore, we find that a violation of the primary QNEC implies a violation of the averaged null energy condition (ANEC) in a conformally transformed frame. In the local quench we find similar bounds on four point correlators from both the primary and the usual QNEC.