Papers

We review the connection between constituent-quark Hamiltonians and QCD and investigate the long-standing difficulty of describing meson and baryon spectra with one common two-body interaction. A Hamiltonian calibrated to ground-state mesons leaves systematic baryon mass residuals, largest in the light-quark sector and decreasing toward heavier flavors. We show that a short-range, color-spin-dependent connected three-quark interaction substantially reduces this incompatibility. Mass-scaled finite-range profiles yield high-accuracy baryon spectra, whereas flavor-independent common-range profiles do not remove the residual flavor pattern. The result is tested on additional ground-state baryons outside the calibration set and through meson–baryon compatibility analyses across several alternative quark-model Hamiltonians. We also benchmark radial and orbital excitations to identify the regime in which a static compact valence Hamiltonian remains reliable, and provide explicit color-spin matrix elements for two- and three-body operators in baryons and multiquark configurations. Within the tested valence-space representations, the results indicate that a mass-dependent short-range connected three-quark interaction provides the missing contribution required for a consistent simultaneous description of meson and baryon ground-state spectra.

Heavy quarkonium production inside jets offers a sensitive probe of QCD dynamics and bound-state formation mechanisms. While recent studies demonstrate that charmonium-in-jet observables effectively discriminate among competing nonrelativistic QCD (NRQCD) long-distance matrix element (LDME) sets, whether this discriminating power persists in the bottomonium sector remains an open question. Here, we present the first phenomenological study of $\Upsilon(1S)$, $\Upsilon(2S)$, and $\Upsilon(3S)$ production inside jets using the fragmenting jet function (FJF) framework at next-to-leading order (NLO), incorporating DGLAP evolution, threshold resummation, and feeddown contributions from higher bottomonium states. In sharp contrast to charmonium, we find that bottomonium-in-jet momentum-fraction ($z_H$) distributions exhibit a universal shape that is remarkably insensitive to the choice of LDME sets. We show that this universality stems from the strong dominance of the S-wave spin-triplet color-octet ($^3S_1^{[8]}$) production mechanism reinforced by $\chi_b$ feeddown transitions. Our predictions capture both the characteristic large-$z_H$ peak and the spectral broadening with increasing jet transverse momentum observed in recent CMS measurements. These results establish a clear physical distinction between charmonium and bottomonium fragmentation inside jets, providing a theoretical benchmark for future high-precision measurements at the LHC.

We investigate the $P$-wave flavor-sextet charmed and bottom baryons within heavy quark effective theory. A key motivation is provided by the recent evidence for the $\Xi_c(2882)^0$, which completes a sequence of four narrow $\Xi_c$ structures together with the $\Xi_c(2923)^0$, $\Xi_c(2939)^0$, and $\Xi_c(2965)^0$. Their characteristic mass-splitting pattern closely parallels that of the $\Omega_c(3000)^0$, $\Omega_c(3050)^0$, $\Omega_c(3066)^0$, and $\Omega_c(3090)^0$ states, providing strong constraints on their spectroscopic assignments. We classify the seven $P$-wave states in each of the $\Sigma_Q$, $\Xi_Q^\prime$, and $\Omega_Q$ sectors ($Q=c,b$), calculate their masses and intra-doublet mass splittings using QCD sum rules, and study their strong decays using light-cone sum rules. Configuration mixing between states with the same quantum numbers is also investigated. The combined analysis favors a common interpretation of the four narrow $\Xi_c$ and the four lowest narrow $\Omega_c$ structures in terms of the corresponding $\lambda$-mode excitations. Extending the same framework to the bottom sector, we obtain a coherent picture of the observed $\Sigma_b$, $\Xi_b$, and $\Omega_b$ structures. In particular, the $\Sigma_b(6097)$, $\Xi_b(6227)$, and $\Omega_b(6350)$ structures may each contain an unresolved pair of nearby $P$-wave states. We also predict two additional $\Sigma_b$ states, two additional $\Xi_b^\prime$ states, and one additional $\Omega_b$ state, all of which are expected to be relatively narrow and remain to be identified experimentally.

In Quantum Field Theory, triangle Feynman diagram $F(p_1^2,p_2^2,p_3^2|m_1,m_2,m_3)$ is an analytic function of its variables, whose analytic structure is fully determined by the location of singularities of the propagators of particles in the loop. The form factor $F(p_1^2,p_2^2,p_3^2|m_1,m_2,m_3)$ is easily calculable in the Euclidean region of all variables, $p_i^2<0$, $i=1,2,3$. A rigorous way to obtain the form factor in the timelike region is to perform the analytic continuation from the Euclidean region using single or double dispersion representations. On the other hand, there is a simple representation of the triangle as integral over Feynman parameters. The goal of this paper is to demonstrate that all known rigorous results of dispersion representations in the regions where some of the variables $p_i^2$ are in the physical Minkowski region, are reproduced by the Feynman-parameter representation for $F(p_1^2,p_2^2,p_3^2|m_1,m_2,m_3)$ by a mere replacement $p_i^2\to p_i^2+i0$ and $m_i^2\to m_i^2-i0$, where $m_i$ are masses of particles propagating in the loop. This simple replacement takes properly into account all subtle contributions given in the context of dispersion representations by the anomalous cuts and thresholds.

At phase coexistence, a degenerate quartic scalar potential admits an exact planar kink whose normal fluctuation operator is the modified Pöschl–Teller operator, with translational and positive shape states below a continuum beginning at $\Lambda=4$. We continue the two connected spectral bands through finite supercooling in a smooth one-component quartic benchmark and resolve $\ell=0,1,2$. The $O(3)$ bounce is obtained by singular collocation, while the radial Euclidean Hessian is analyzed by finite-difference diagonalization and independent threshold shooting. The positive $\ell=2$ and $\ell=1$ branches reach the common false-vacuum continuum threshold at $\delta_{{\rm merge},2}=0.0900472$ and $\delta_{{\rm merge},1}=0.1410162$, respectively. At each endpoint, $u_\ell\propto\rho^{-\ell}$ is square integrable and defines a threshold eigenstate; beyond the endpoint, however, no normalizable eigenstate continuation exists for the corresponding branch. The $\ell=0$ shape state remains bound up to the geometric wall crossover. Its planar-mode overlap, radial centroid, and distinct interior and exterior decay lengths reveal asymmetric wave-function deformation. Thus, angular spectral dissolution and the later geometric loss of a true-vacuum-like core are separate phenomena, revealing two distinct finite-supercooling fates of the planar shape mode.

We compute quark and meson spectral functions in low-energy QCD, including all-order scatterings and decays of pions and the scalar $\sigma$-mode. For low energies the gluons decouple and the dynamics of two-flavour QCD is well-described by a Quark-Meson model. The computations are performed directly in Minkowski space, using the spectral functional renormalisation group. The full mesonic realtime dynamics is captured with the emergent composite approach which is extended here to realtime processes. The inclusion of all-order scatterings and decays is achieved through the self-consistent treatment of the scattering tails and the momentum-dependent resummation of the four-meson vertex via its Bethe-Salpeter equation. We illustrate the importance of higher-order scatterings using the example of the $\pi \to 3\pi$ scattering threshold - the lowest kinematically accessible channel for the pion.

Quark-lepton complementarity (QLC) provides a phenomenological framework for comparing quark and lepton flavour structures. We reassess a modified QLC correlation-matrix construction using the 2026 Particle Data Group quark-mixing inputs and the NuFIT 6.1 oscillation likelihoods. The historical prediction $\sin^2\theta_{23}=0.4235$ is strongly disfavoured, with $\Delta\chi^2=17.99$ for normal ordering and 20.43 for inverted ordering, whereas later ordering-dependent estimates remain compatible with present preferred regions. Reconstructed ensembles of the complex correlation matrix show that the first row is comparatively stable, while about 99% of the squared mean-texture evolution occurs in the lower two rows; roughly 72% of the present ensemble remains closer to the tribimaximal than to the bimaximal reference texture. We further formulate the lepton sector in the symmetric Schechter-Valle parametrization. The oscillation phase appears as the invariant combination $\delta=\phi_{13}-\phi_{12}-\phi_{23}$, while independent phase directions remain relevant to lepton-number-violating (LNV) amplitudes. We prove that, for unrestricted diagonal quark-lepton mismatch phases, changing from the standard PDG convention to the symmetric parametrization leaves the full ensemble of $|V_{c,ij}|$ invariant: additional left phases are absorbed into the mismatch matrix and right phases only rephase columns. Consequently, the QLC magnitude texture does not constrain the independent Majorana/LNV phases. The historical $S_1$ and $S_2$ limits are also found to lie close to their phase-agnostic kinematic ceilings.

Despite the Standard Model's ability to describe collider data from all experiments conducted around the world, several questions about the history of the Universe, including the hierarchy problem, the baryon asymmetry, and the dark matter density, remain open. To address these unresolved issues, the particle physics community agrees on the need to construct a next-generation collider that could probe the Standard Model with higher accuracy and potentially reveal deviations from the predictions of this fundamental theory. Future lepton colliders, operating at energies from the Z pole up to the multi-TeV scale, could probe the electroweak sector in various ways. In this thesis, the influence of radiative corrections on the modelling of electroweak processes is investigated.

The 146-GeV excess in the electron-muon final state reported by the CMS Collaboration offers a tantalizing hint for new physics. There are two competing explanations for the origin of the 146-GeV resonance: production via mixing with the Standard Model Higgs boson and leptophilic production through sea electrons and muons inside the proton. In anticipation that such an excess may still persist by the end of LHC Run 3, we propose three related production channels $H\gamma$, $H j$, and $H jj$, which could be used to distinguish between these two possible scenarios. Taking the two-Higgs-doublet model (2HDM) as an explicit example, we estimate that with $3000~\text{fb}^{-1}$ of the high-luminosity LHC data, the $H\gamma$ channel can provide a striking discriminating power between the mixing and leptophilic scenarios with a significance of 7.1. Combining it with the other two channels, $H j$ and $H jj$, the significance can be pushed up to 7.6.

Recent studies have explored whether physical constants and symmetries can be selected by extremizing bipartite entanglement entropy. We extend this approach to a three-particle setting. Specifically, we consider a $2+1$-particle system in which particles $B$ and $C$ are initially entangled, and then particles $A$ and $B$ scatter without the direct participation of particle $C$ for both gluon-gluon and graviton-graviton scatterings. Using angular expansions around the forward and backward scattering limits, we analyze bipartite entanglement in the corresponding two-particle system of $A$ and $B$ and two measures of genuine tripartite entanglement (GTE), the concurrence fill and the generalized geometric measure (GGM), in the three-particle system. As is already known, the bipartite entanglement provides no universal criterion for selecting the symmetry-preserving theory: depending on the initial helicities, it may either maximize or minimize the entanglement entropy. By contrast, we find that the GTE-based analysis uniquely identifies the gauge-invariant and diffeomorphism-invariant theories as those that suppress the GTE in gluon-gluon and graviton-graviton scatterings, respectively. This result suggests a nontrivial connection between tripartite entanglement and the gauge and diffeomorphism symmetries of fundamental interactions.

It is well known that electron-positron pairs can be created in the strong-field environments formed by (i) a high-intensity laser field and a high-energy $\gamma$-photon (nonlinear Breit-Wheeler process) or (ii) a high-intensity laser field and a nuclear Coulomb field (nonlinear Bethe-Heitler process). Both of these processes are particularly interesting in the interaction regime where the laser field enters nonperturbatively. Various experimental collaborations are currently aiming at detecting for the first time the nonperturbative Breit-Wheeler process, by exploiting high-intensity laser pulses and $\gamma$-ray sources based on bremsstrahlung. In contrast, an experimental observation of the nonlinear, nonperturbative Bethe-Heitler process still lies further ahead in the future because its technical realization appears at present more challenging. Our comparative study shows, however, that the physical properties of the total rates for the processes (i) and (ii) can become remarkably similar when the parameters for the bremsstrahlung-driven nonperturbative Breit-Wheeler process are properly chosen. In this sense, the upcoming experiments on the nonlinear Breit-Wheeler process could also be used to closely “simulate” the currently hard to observe nonlinear Bethe-Heitler process.

Establishing the near-threshold spin-isospin multiplet spectrum of $D^{(\ast)}\bar D^{(\ast)}$ systems is central to testing molecular interpretations of the $X(3872)$, $Z_c(3900)$, and $Z_c(4020)$. The isovector channels are particularly important in this context, as the associated structures would have a clear exotic character. In this work, we analyze the BaBar and Belle data on $B\to\chi_{c1}\pi K$ to search for possible isovector $D^\ast\bar D^\ast$ molecules with $J^{PC}=0^{++}$ and $2^{++}$. The three-body decay amplitude includes an effective nonresonant term, intermediate kaon resonances, and $\chi_{c1}\pi$–$D^\ast\bar D^\ast$ coupled-channel rescattering. For each data set, the $\chi_{c1}\pi$ and $K\pi$ invariant-mass distributions are fitted simultaneously under three scenarios: without rescattering and with either $J=0$ or $J=2$ rescattering. We then analytically continue the fitted coupled-channel $T$ matrices to search for poles. For the case of $J^{PC}=0^{++}$, the BaBar and Belle fits yield virtual poles at $-2.15^{+2.10}_{-6.41}$ MeV and $-18.40^{+8.58}_{-13.70}$ MeV, respectively, relative to the $D^\ast\bar D^\ast$ threshold. For $J^{PC}=2^{++}$, the corresponding virtual poles are located at $-3.42^{+2.37}_{-4.29}$ MeV and $-4.26^{+1.34}_{-1.69}$ MeV, respectively. The tensor virtual-state pole is consistent with a prediction from chiral effective field theory, which also predicts the existence of $W_{c1}$, an isospin partner of $X(3872)$. Since the invariant-mass distributions alone cannot distinguish total spin $J$, we also predict angular distributions. The $\cos\theta_{\chi_{c1}\pi}$ distribution provides a direct spin discriminator, while the $\cos\theta_{K\pi}$ distribution further tests the rescattering contribution. The measurements of these predictions would help establish the $D^{(\ast)}\bar D^{(\ast)}$ molecular multiplet spectrum in the future.

We discuss the sensitivity of the JUNO neutrino detector to the Migdal ionization signal triggered by nuclear scattering events produced by sub-GeV weakly interacting massive particles (WIMPs). Exploiting JUNO's large target mass and the annual modulation effect we find that the aggregate rate from many independent and indistinguishable WIMP events in JUNO's liquid scintillator can be isolated from the total dark rate of the photomultipliers, potentially providing for spin-dependent interactions a world-leading sensitivity across the sub-GeV mass range.

Calculating cross sections in the Color Glass Condensate effective theory requires Fourier transforms of multi-Wilson-line correlators from transverse coordinate space to transverse momentum space. Under the common assumption of impact-parameter independence, each transform reduces to a set of Hankel transforms whose Bessel-function kernels oscillate rapidly at phenomenologically relevant momenta, making direct quadrature prohibitively expensive. We present a Filon-type quadrature, applicable to any integrand, that integrates these oscillatory factors in closed form on the stored coordinate grid, reducing each Hankel transform to a precomputed weight vector and the full nested transform chain to a sequence of matrix products. We develop and validate the method on the deep inelastic scattering dijet cross section beyond the correlation-limit approximation, where an exprel-based reformulation of the quadrupole Wilson-line correlator removes a numerical $0/0$ instability inherent to its standard parametrization. Porting the calculation to the Graphics Processing Unit (GPU), with custom CUDA kernels that fuse the momentum-space contraction directly into the correlator evaluation, brings the runtime for one dipole input down to about two minutes on a single NVIDIA A800, from several hours on a multi-core Central Processing Unit (CPU). We further generalize the algorithm to three sequential Hankel transforms and validate the resulting six-dimensional transform against an analytic Gaussian integrand family with closed-form results at every stage. This general, process-independent algorithm is directly applicable to next-to-leading-order proton-nucleus and electron-ion scattering cross-section calculations performed without the correlation-limit approximation. The code is publicly available at https://github.com/CCNU-CGC-py/FFT_filon.

If axion-like particles (ALPs) exist, they may have renormalizable couplings only to the Higgs boson ($h^0$) or to fields beyond the Standard Model. An ALP $A_h$ lighter than about 60 GeV would allow the $h^0 \to A_h A_h$ decay, with a branching fraction determined by the explicit global symmetry breaking responsible for the main contributions to the $A_h$ mass ($M_A$). New heavy fields that carry color and electric charge, such as squarks, can mediate $A_h$ decays at one loop mostly into gluons, but also into photons. Exploring LHC sensitivity to $A_h$, we show that the $h^0 \to A_h A_h \to (gg)(\gamma\gamma)$ channel leads to a diphoton resonance at $M_A$ whose production rate is consistent with a $3.5\sigma$ excess reported by a CMS search at $M_A \approx 13.6$ GeV. For $M_A$ of order 10 GeV, the $h^0 \to A_h A_h \to 4g$ cascade decay leads to two wide jets (each with 2-prong substructure) that form a resonance at 125 GeV.

This article proposes a dynamical framework to address the charged-lepton mass hierarchy and derive the empirical Koide formula. We postulate a $U(3)_F$ flavor symmetry at the high-energy scale, where a heavy dynamical flavon field couples to the electroweak Higgs sector via an effective operator. As the universe cools, spontaneous symmetry breaking of the flavor group occurs following the pattern $U(3)_F \to U(1)^3_F$. Subsequently, the electroweak symmetry breaking at the Fermi scale generates the charged-lepton mass matrix. The phenomenological values of these masses are determined in the infrared regime, where the effective potential governing the flavon VEV undergoes a dynamical vacuum alignment.The stable minimum of this potential enforces an algebraic equipartition between the flavor-singlet and flavor-octet invariants ($I_{(0)} = I_{(8)}$). This geometric equilibrium yields the Koide mass ratio ($Q=2/3$), successfully identifying the dynamically generated eigenvalues with the physical pole masses of the electron, muon, and tau.

In four-flavor massless QED with a magnetic monopole, a single incident fermion is scattered into a state carrying a half-integral current vector in each flavor channel, called the semiton. Recently, the semiton has been interpreted as a twisted-sector fermion, but its microscopic Hilbert-space representation has not been fully developed. In this Letter, using a bosonized fermion–rotor model, we construct the semiton state explicitly. This is achieved by first identifying the correct vacuum of the system, and then constructing a unitary operator that shifts the rotor and creates a particle-hole cloud in each flavor channel. The semiton state is obtained by applying this operator to an ordinary fermion state. The resulting state has a localized fermion flavor density in the core region and a half-integral semiton front at the wavepacket. We also show that the state carries the correct $U(1)_M$ charge expectation values and energy-density profile. Our result provides a concrete Hilbert-space realization of the varying-Fock-space interpretation of monopole–fermion scattering, advocated in previous works by the author and collaborators.

We investigate the discovery potential of a heavy $Z'$ boson as a portal to charged sleptons and right-handed sneutrinos within the $B-L$ Supersymmetric Standard Model (BLSSM) at the High-Luminosity LHC. Using a detector-level simulation and Boosted Decision Trees to suppress Standard Model backgrounds, we find that the direct slepton decay $pp \to Z' \to \tilde{\ell}^+\tilde{\ell}^- \to 2\ell + E_{\rm T}^{\rm miss}$ yields a significance exceeding $5\sigma$ at 3000 fb$^{-1}$, while the cascade $(\mbox{multileptons} + E_{\rm T}^{\rm miss})$ mode is unobservable due to rate suppression. For right-handed sneutrinos, the hadronic channel $pp \to Z' \to \tilde{\nu}_R\tilde{\nu}_I \to 2\ell + 4j + E{\rm T}^{\rm miss}$ emerges as the most promising signature. These results establish the $2\ell + E_{\rm T}^{\rm miss}$ and $2\ell + 4j + E_{\rm T}^{\rm miss}$ final states as the principal discovery channels for the scalar leptonic sector of the BLSSM at the HL-LHC.

Gravitational-wave (GW) observations of stellar-mass compact binary coalescences directly measure the source luminosity distance. Combined with the source redshift, these measurements constrain the current expansion rate of the Universe, the Hubble constant, $H_0$, or $h=H_0 / [100 \,{\rm km \,s^{-1} \, Mpc^{-1}}]$. For most GW signals no electromagnetic redshift measurement is expected, but the GW signal itself depends on the redshifted (detector-frame) masses. Assuming a source-frame mass distribution therefore enables a redshift estimate for each source. Combining the redshift estimates with the distance measurements provides a weak constraint on $H_0$ for each individual source that tightens with the number of sources in the catalog. However, the shape of the source-frame mass distribution is not known a priori, and previous work has relied on parametric models (piecewise power-laws with Gaussian components), and one-dimensional Gaussian processes. Here, we introduce CosmoPyro, a fully differentiable hierarchical Bayesian inference code that models the mass distribution using either one- or two-dimensional Gaussian processes. With the latest GW transient catalog (GWTC-5) we find $h = 0.66^{+0.17}_{-0.20}$ and $h = 0.57^{+0.20}_{-0.15}$ (median with $1\sigma$ uncertainty), for the one- and two-dimensional case, respectively. Despite the noticeably different inferred mass distributions, both models yield $H_0$ values consistent with the latest LVK measurements within $1 \sigma$. While our main results marginalize over the Gaussian-process power-spectrum hyperparameters, the measurement is also robust against fixing these hyperparameters over a range comparable to their measured uncertainty.

Detailed Geant4 simulation of calorimeter showers dominates the computing budget of high-energy physics experiments. Deep generative surrogates reduce this cost, but they have remained tied to the detector they were trained on, so each new geometry needs a large in-domain dataset. We study whether a single point cloud shower generator can be pre-trained on multiple detectors and transferred to unseen calorimeters. The pre-training geometries come from synthetic geometric variation rather than real-detector data. We introduce SimpleBox, a family of $10^4$ box calorimeters spanning the plane of sampling fraction and longitudinal segmentation, and benchmark it against pre-training on realistic detectors. On a calorimeter unseen in pre-training, with $10^3$ target showers for fine-tuning, the two priors reduce the aggregated sliced Wasserstein distance to Geant4 by factors of 5.2 (synthetic) and 8.0 (realistic) relative to training from scratch. At larger target sizes the synthetic prior performs better than the realistic one. Geometric diversity alone is therefore a practical way to pre-train a transferable shower generator.

We construct a generating functional for infrared-finite scattering amplitudes in massive quantum electrodynamics (QED) by including Faddeev-Kulish dressings in a holomorphic coherent-state representation, in the spirit of the construction of Aref'eva-Faddeev-Slavnov (AFS) for the undressed Dyson S-matrix. At tree level, the dressed generating functional reduces to an AFS path integral with dressed boundary conditions.

Quantum dots are tunable semiconductor nanocrystals that can be produced at industrial scales. We present the first ab initio calculation of the scattering of dark matter on electrons bound in quantum dots. The momentum-dependence of a quantum dot's electronic response depends on its morphology and on the dark matter mass, interaction operator, mediator coupling, and mediator mass. Therefore, the relative rates across an array of distinct quantum dot targets form a “barcode” that carries information about the nature of the dark matter interaction. We project the sensitivity of a detector concept in which a collection of independent target subunits, each loaded with silicon quantum dots of a particular morphology, are read out by Skipper CCDs. Given a future signal, this barcode could discriminate between interaction operators and mediator types. We quantify the discrimination power for a benchmark pair of models as a function of readout noise and exposure.

Variations in the gauge couplings of the Standard Model have been searched for experimentally and proposed as solutions to open questions in fundamental physics. Varying gauge couplings can arise from a dynamical scalar field coupled to the gauge kinetic term. This mechanism has been invoked extensively, assuming a minimal linear coupling of the scalar to the gauge bosons. In this work, we investigate how this operator is generated from the ultraviolet perspective. We argue that in weakly coupled, renormalizable completions in four spacetime dimensions, gauge invariance forces the leading dependence of the effective gauge coupling on the scalar to be logarithmic rather than linear. The gauge coupling evolution in these scenarios can be entirely described by the renormalization-group running with dynamical mass thresholds. Beyond leading order or four dimensions, we provide examples showing that more general behavior is possible. Finally, we discuss the phenomenological implications of dynamically evolving gauge couplings, particularly in early-universe settings.

We define detector operators in the nonrelativistic conformal field theory describing fermions at unitarity. We reduce the problem of computing the momentum distribution and correlation between final particles produced by a local source ("point-produced") to the computation of correlation functions involving the detector operators. The general formalism is applied to the point production of three unitary fermions, where we find the momentum and angular distribution of final particles. We discuss a nonrelativistic version of celestial holography, which maps the asymptotic out-state to a quantum wave function in the so-called "oscillator frame."

A superradiant cloud of ultralight axions around a black hole, that is part of an X-ray binary system, can heat up its accretion disk and be detected by the thermal X-ray spectrum emitted by the disk. We consider a derivative coupling of the axions to the plasma fermions and calculate the emissivity of the inverse bremsstrahlung process that results in a temperature fluctuation of the disk. Based on the thin-disk model and the multicolor disk model, we derive the thermal spectrum with axion heating, which shows an enhanced thermal photon flux and a red-/blue- shifted peak spectral frequency. A single bump hunting search of the axion heating signature in the thermal spectrum of a $10M_\odot$ black hole X-ray binary with a spectral measurement sensitivity of 10% (1%) can derive the constraint on axion-electron coupling $|g_{ae}|\gtrsim7.5\times 10^{-12} ~(2.4 \times 10^{-12})$ for axion mass $m_a=5.2\times 10^{-12}\,$eV in a saturated $|211\rangle$ state, and $|g_{ae}|\gtrsim4.5\times 10^{-12} ~(1.4 \times 10^{-12})$ for axion mass $m_a=1.0\times10^{-11}\,$eV in a saturated $|322\rangle$ state. The projected sensitivities are competitive with those from XENONnT. A detailed continuum fitting can further improve the detectability and provide a complementary bound to the black hole spin-down measurement.

We present a density functional-based equation of state for warm, dense nuclear matter with a transition to deconfined quark matter for applications to simulations of supernova explosions and neutron star mergers, but also for the cosmological evolution of Q-balls. For the quark matter equation of state, we employ a recently developed confining density functional approach while nuclear matter is described within a relativistic density functional model of the DD2 class. The phase transition is obtained by a Maxwell construction at constant entropy per baryon. We discuss the solutions of TOV equations for isentropic hybrid stars for two hybrid equation of state models: DDf-SFM without and DD2-$\chi$CDF with color superconductivity. We find that at finite temperatures above a critical value of entropy per baryon sequences of disconnected third family branches ("thermal twin stars") may appear for the DDf-SFM model, while they are absent for the color superconducting model and at $T=0$. We discuss the relation of this critical entropy per baryon to the Seidov criterion of gravitational instability for $T=0$ and find that it is a good guide. We suggest that the presence of thermal twin stars may be regarded as an indicator for the core-collapse supernova explodability of massive blue supergiant stars with solar metallicity and thus serve as a new criterion for the reliability of hybrid equation of state models. By this argument, strong color superconductivity shall be excluded and it remains to be shown whether models with moderate diquark pairing could fulfill the thermal twin constraint. For the case of symmetric matter, we compare the resulting hybrid EOS with the flow constraint by Danielewicz et al. and find a a sensitivity of the onset density for deconfinement to the presence or absence of color superconductivity.

The familiar Bethe-Heitler process on the proton target $e+p\to e+p+\gamma$ is transformed into a laboratory for studying multiparticle entanglement. We discuss how bipartite and genuine tripartite entanglement between the final state electron, proton and photon are built up by successive $1\to 2$ and $2\to 2$ elementary interactions. We validate our argument by simulating events. Below 5 GeV center-of-mass energy, we identify more than 900 Greenberger-Horne-Zeilinger (GHZ) states and 1200 W states, each with a fidelty exceeding 99%.

High-energy $\gamma\gamma$ collisions, realizable as an operational mode of future lepton linear colliders such as the ILC and CLIC, provide a promising environment to probe extended Higgs sectors. We investigate the sensitivity of such colliders to doubly charged Higgs bosons within the 2-Higgs Doublet Model with type-II seesaw (2HDMcT). Focusing on the three-body production channels $\gamma\gamma \to H^{\pm\pm}H_1^{\mp}H_1^{\mp}$ and $\gamma\gamma \to H^{\pm\pm}H_1^{\mp}W^{\mp}$, we perform a parameter space scan consistent with theoretical constraints as well as current collider, flavor, and electroweak precision observables (EWPOs). We show that $\gamma\gamma$ collisions can rival the discovery potential of the conventional $e^+e^-$ mode for probing doubly charged Higgs bosons through a $4\ell+E_T^{miss}$ signature ($\ell=e,\mu$). Despite the reduced effective luminosity resulting from the photon spectrum, the significantly enhanced production cross sections, exceeding those in electron-positron collisions by more than one order of magnitude, compensate for this limitation. By performing a detailed signal-to-background analysis at center-of-mass energies of $\sqrt{s}=830$ and $1245$ GeV, we demonstrate that a discovery significance at the $5\sigma$ level can be achieved for viable benchmark points (BPs).

Hadrons are particles composed of elementary quarks and gluons, which have strong interactions described by Quantum Chromodynamics (QCD); examples are protons and neutrons, which bind to form atomic nuclei. In contrast, photons are usually thought of as the elementary force carriers of quantum electrodynamics (QED). However, at the quantum level a photon can fluctuate into a quark antiquark pair. At sufficiently high energies these virtual quarks can become real, physical particles by interacting with other particles, in particular with other hadrons. In this way photons with energies exceeding a few GeV acquire properties of a hadron. Resolved photon processes are reactions that probe these hadronic properties. These processes often dominate the production of hadronic final states, including jets (sprays of collimated hadrons), at electron–proton and electron–positron colliders. Implications of this for backgrounds at future high–energy lepton colliders remain poorly understood.

In this work, we investigate possible $\chi_{cJ}$–nuclear bound states with $J=0,1,2$ using in-medium mass shifts generated by virtual $D^{(*)}\bar{D}^{(*)}$ loops within an unquenched framework. The resulting $\chi_{cJ}$–nucleus potentials are constructed in the local density approximation, and the bound state spectra are calculated for $^{12}{\rm C}$, $^{16}{\rm O}$, $^{40}{\rm Ca}$, $^{90}{\rm Zr}$, $^{197}{\rm Au}$, and $^{208}{\rm Pb}$. Bound states are obtained for all systems considered. The $\chi_{c0}(1P)$ and $\chi_{c1}(1P)$ spectra are nearly degenerate, whereas the larger in-medium mass shift of $\chi_{c2}(1P)$ leads to deeper binding. Although the absolute bound state energies depend appreciably on the cutoff parameter, the energy differences relative to the $1s$ level are considerably less sensitive to it and exhibit a regular pattern that decreases approximately as $A^{-2/3}$ with increasing nuclear mass number. A cosh-type potential with a common nuclear geometry provides a compact description of these spectra. The predicted bound-state structures and level-spacing systematics could be investigated in future high-statistics near-threshold photoproduction experiments at the upgraded JLab facility.