We compute synchrotron radiation from a plasma in which $P$- and $CP$-violating parameters, a chiral chemical potential and a chiral gradient, couple to fermions. To do this, we compute exact wave functions for the fermions in the presence of these parameters and an external constant magnetic field. We find that these parameters increase the synchrotron radiation emitted by the fermions while also decreasing the traditionally large synchrotron radiation elliptic flow coefficient $v_2$. We apply these results to the quark-gluon plasma, where just such a contribution could provide a solution to the missing direct photons puzzle. We also use our wave functions to give a derivation of the chiral magnetic effect.

We develop a perturbative description of vacuum radiative processes in quantum electrodynamics with a prescribed external electromagnetic background capable of producing electron-positron pairs. Since the initial vacuum is then unstable and the in- and out-vacua are inequivalent, radiative observables require a real-time formulation beyond the ordinary in-out approach of vacuum-stable QED. Using the Keldysh-Schwinger-Fradkin nonequilibrium technique, we derive the mean number density of emitted photons through the second nonvanishing order in the fine-structure constant. The leading term, of order $\alpha$, reproduces the known vertex and tadpole mechanisms, while the complete order-${\alpha }^2$ correction contains interference, loop, and induced-current contributions. We also give an independent derivation based on the spectral decomposition of the identity operator in the in-Fock space, where the photon number density is represented as a sum of squared transition amplitudes and vacuum-disconnected terms are canceled by the optical theorem generalized to an unstable vacuum. In addition, we compute the mean electromagnetic field through order $e^3$, including the electromagnetic dressing of the induced vacuum current, and verify it using the corresponding Schwinger-Dyson equations. The final formulas are expressed in terms of exact solutions and propagators of the Dirac equation in the external background and apply to general spacetime-dependent field configurations.

We develop the complete theoretical framework for open quantum systems coupled to scale-invariant environments. Such environments, we show, are universally and uniquely described by unparticle baths [1] characterized by a single scaling dimension $d_{\mathcal{U}}$, which is a property of the bath operator entering the coupling, not of the probe. Different probes coupled to the same bath operator ${\mathcal{O}}_E$ must yield the same $d_{\mathcal{U}}$, providing a nontrivial cross-probe consistency test for a fixed coupling channel. This companion paper provides the full proof of the uniqueness theorem, the mathematical formalism of the resulting non-Markovian dynamics, and worked applications to three physical realizations omitted from the shorter letter [2]. Starting from the uniqueness theorem, we derive the complete set of non-Markovian memory kernels, the exact noise kernel, including vacuum and thermal contributions via Matsubara summation, and the fractional generalization of the Caldeira-Leggett master equation for arbitrary $d_{\mathcal{U}}$. The unparticle dimension acts as a control parameter governing a rich phase structure, including a thermalization transition at $d_{\mathcal{U}}=3/2$, the Ohmic boundary at $d_{\mathcal{U}}=2$, and a decoherence phase transition at $d_{\mathcal{U}}=5/2$ in the thermal regime ($d_{\mathcal{U}}=2$ in the vacuum regime), beyond which quantum coherence is protected at long times. These transitions are universal for free-field, weakly interacting, and engineered power-law baths; for strongly interacting CFT baths they describe intermediate-time scaling in the window $1/{\omega }_{\mathrm{UV}}\ll t\ll 1/T$. Three physical realizations are presented. For the quantum Ising model, $d_{\mathcal{U}}$ is derived from first principles from the known CFT operator dimension. For inflationary cosmology, $d_{\mathcal{U}}=2$ is obtained by matching to established results; for heavy-fermion materials, $d_{\mathcal{U}}=3/2$ is inferred empirically from two-channel transport data. Coupling to the energy operator in ($1+1$) spacetime dimensions yields $d_{\mathcal{U}}=3/2$, providing a field-theoretic derivation of $1/f$ noise; the ($2+1$)D case yields $d_{\mathcal{U}}\approx 1.413$ from the conformal bootstrap [3]. For high-energy astrophysical neutrinos in the regime $E\gg T$, the energy- and baseline-dependent decoherence rate ${\mathrm{\Gamma }}_{\text{decoh}}\propto \mathcal{B}(E,T_{\mathcal{U}})L^{5-2d_{\mathcal{U}}}$ provides a direct observable imprint of the scaling dimension. A systematic comparison with the Caldeira-Leggett model, phenomenological Lindblad equations, and the non-Markovian literature establishes the precise relationship between these approaches and the unparticle framework. The regime of validity is analyzed for each physical system, including the crossover between vacuum and thermal regimes of the noise kernel. Experimental predictions and consistency tests are detailed for trapped-ion quantum simulators, neutrino telescopes, and superconducting qubits.

We study the impact of inelastic gluon-radiation and absorption processes on the transport coefficients of the quark-gluon plasma within the dynamical quasiparticle model (DQPM) in the temperature–baryon-chemical-potential plane $(T,{\mu }_B)$. Extending the $2\to 2$ baseline established in previous DQPM calculations, we include gluon-radiation $2\to 3$ and the inverse gluon-absorption $3\to 2$ scattering channels with massive partons and effective DQPM propagators and vertices. The corresponding momentum-dependent interaction rates and relaxation times are used to calculate the shear viscosity, bulk viscosity, electric conductivity, and baryon diffusion coefficient as functions of temperature $T$ and baryon chemical potential ${\mu }_B$. Within the relaxation time approximation, we find that $2\leftrightarrow 3$ contributions systematically reduce all considered transport coefficients relative to the $2\to 2$ only results, in accordance with the decrease of the relaxation times. In the thermal regime explored here, however, this reduction remains moderate, since the investigated inelastic rates stay below the $2\to 2$ ones over the considered $(T,{\mu }_B)$ range. The inelastic channels become more relevant mainly for partonic scatterings at large momenta, which are thermally suppressed in the strongly interacting QGP. At ${\mu }_B=0$, the resulting $\eta /s$, $\zeta /s$, and ${\sigma }_Q/T$ are compatible with available lattice-QCD estimates within uncertainties. At finite ${\mu }_B$, our results provide predictions for the transport properties of QCD matter relevant for beam-energy-scan programs.

Self-energy and vacuum polarization effects in quantum electrodynamics (QED) are calculated for the supercritical Coulomb field, where Dirac energy levels become embedded in the negative-energy continuum. In this regime, the quantum vacuum becomes unstable, resulting in spontaneous electron-positron pair creation. By calculating the imaginary part of the QED correction, we gain access to an unexplored channel of vacuum instability: radiative spontaneous pair creation. Our results show that this radiative channel is greatly enhanced in the vicinity of the threshold of the supercritical regime, providing evidence for nonperturbative effects with respect to the fine-structure constant $\alpha$. We therefore conjecture that the total probability of spontaneous pair creation could differ significantly from the predictions of Dirac theory, especially near the supercritical threshold.

Inspired by the invariant mass distributions for the decays $D^0\to K_S^0{\pi }^0\eta$ and $D^0\to K_S^0{\pi }^0{\pi }^0$ reported by the BESIII Collaboration, we investigate these processes with an unified final state interaction formalism by incorporating both the $S$-wave pseudoscalar meson-pseudoscalar meson interactions within a chiral unitary approach and the $P$-wave contributions from the intermediate resonance ${\overline{K}}^{*}(892)$ and some higher states. By performing a combined fit to the invariant mass spectra and taking into account the coherence between the $S$ and $P$ waves, our results are in agreement with the experimental data. For the decay $D^0\to K_S^0{\pi }^0\eta$, the structure near 1.0 GeV in the ${\pi }^0\eta$ invariant mass distribution corresponds to the signal of the $a_0(980)$, which is dynamically generated from the $S$-wave interactions. In the case of $D^0\to K_S^0{\pi }^0{\pi }^0$, the near-threshold enhancement in the ${\pi }^0{\pi }^0$ mass distribution arises from the combined contributions of the $f_0(500)$ and the intermediate ${\overline{K}}^{*}(892)$, while the cusplike structure around $1{\mathrm{GeV}}^2$ is associated with the $f_0(980)$.

We introduce a Rydberg-based single photon detector (SPD) for probing dark matter in the 0.1–10 meV mass range (20 GHz–2 THz). The Rydberg SPD absorbs photons produced and focused by the BREAD dish antenna and trades them for free, detectable electrons. At the lower end of the mass range, photons drive Rydberg-Rydberg transitions, which are read out via state-selective ionization. At higher masses, they directly ionize the Rydberg atoms.

We provide a study of the parameter space of the complex 2-Higgs doublet model (C2HDM), focusing on signs of large $CP$-violating couplings of the 125 GeV Higgs boson with the fermions. The study is performed utilizing machine learning (ML) techniques developed recently for parameter space exploration, including an evolutionary strategy algorithm and novelty reward. We give particular attention to the electron electric dipole moment (eEDM). We confirm that the recently found kite diagrams are crucial for the outcome of the analysis. Moreover, their use also mitigates the dependence of the results on the scale and scheme choice of the masses in the loop diagrams. We furthermore point out that, already at the current level of experimental precision, the Barr-Zee diagrams with charm quark loops must be taken into account. The combined use of kite diagrams and ML techniques allows for the resurrection of large fermion $CP$-odd couplings for type II and flipped C2HDM when the 125 GeV Higgs coincides with the second lightest neutral scalar. This arises due to cancellations, typically of the per-mil order, which, moreover, will still be possible for a foreseeable eEDM precision down to ${10}^{-33}$ e. cm. For these cases, the constraints on the $CP$-odd couplings arises from the precision LHC measurements.

$CP4$ $3\mathrm{HDM}$ is a curious version of the three-Higgs-doublet model built upon a $CP$ symmetry of order 4 (dubbed $CP4$). When extended to fermions, $CP4$ leads to unusually tight correlations between the scalar and Yukawa sectors and induces tree-level flavor changing neutral couplings. Still, viable scenarios exist, in which quark flavor changing signals remain within experimental limits. In this work, we extend $CP4$ to the lepton sector and investigate whether the lepton-Higgs couplings and lepton flavor violating (LFV) signals can also be kept under control. We consider two classes of LFV processes: tree-level leptonic decays of the 125 GeV Higgs boson and the muon decays $\mu \to e\gamma$ and $\mu \to 3e$. For each $CP4$-invariant lepton Yukawa scenario, we perform a focused Yukawa sector scan that uses physical lepton properties as input and suppresses LFV effects. We identify a promising $CP4$ $3\mathrm{HDM}$ scenario compatible with the present-day experimental constraints, show that it can accommodate the recent CMS hint of a 146 GeV scalar decaying to $e\mu$, and argue that this interpretation can be tested at future colliders through the search of comparably strong $ee$ and $\mu \mu$ signals.

We study the theoretical constraints on the scalar sector of the alternative left-right model (ALRM), an $E_6$-motivated extension of the Standard Model based on the gauge group $SU(3{)}_c\otimes SU(2{)}_L\otimes SU(2{)}_{R^{\prime }}\otimes U(1{)}_{B-L}$, supplemented by a global $U(1{)}_S$ symmetry. We derive the complete set of tree-level perturbative unitarity constraints on the model, resulting in 14 independent conditions on the quartic scalar couplings. When combined with the boundedness-from-below conditions and the requirement of positive-definite scalar mass-squared eigenvalues, this yields significantly more stringent restrictions on the parameter space than either set alone. We then perform a one-loop renormalization group analysis, evolving the model parameters up to a high-energy cutoff scale, and requiring that the vacuum stability, the unitarity, and the perturbativity conditions are preserved throughout. The renormalization group evolution is found to restrict the allowed parameter space considerably beyond the tree-level bounds, with the constraints on the quartic couplings becoming more stringent as the cutoff scale is raised. Consequently, the physical scalar masses in the model acquire upper bounds. For the right-hand symmetry breaking scale, $v_R=10\mathrm{TeV}$ and requiring theoretical consistency up to ${10}^{16}\mathrm{GeV}$, we obtain $m_{H_1^{\pm }}\lesssim 6.5\mathrm{TeV}$, $m_{H_2^{\pm }}\lesssim 1.5\mathrm{TeV}$, and $m_{H_1^0}\simeq m_{A_1}\lesssim 1.5\mathrm{TeV}$, with all bounds scaling with $v_R$. These findings offer a predictive and falsifiable framework for searches of the extended Higgs sector of the ALRM at the current and future collider experiments.

We present a lattice QCD study of dilepton production in charmonium transitions, specifically focusing on the $1^{+-}\to 0^{-+}$ and $1^{++}\to 1^{--}$ processes: $h_c\to {\eta }_c{\ell }^{+}{\ell }^{-}$ and ${\chi }_{c1}\to J/\psi {\ell }^{+}{\ell }^{-}$, where $\ell =e$, $\mu$. The relevant hadronic matrix elements are computed using gauge field configurations generated by the Extended Twisted Mass Collaboration with $N_f=2+1+1$ dynamical Wilson-Clover twisted-mass fermions at four lattice spacings. Simulations are performed at physical dynamical $u$, $d$, $s$, and $c$ quark masses, except for the coarsest lattice, where the lightest sea quark mass corresponds to a slightly heavier pion mass. A controlled continuum extrapolation is carried out. In the continuum limit for the $h_c$ decays, we obtain $\mathrm{\Gamma }(h_c\to {\eta }_c{e}^{+}{e}^{-})=5.45(19)\mathrm{keV}$, and $\mathrm{\Gamma }(h_c\to {\eta }_c{\mu }^{+}{\mu }^{-})=0.635(22)\mathrm{keV}$. For the ${\chi }_{c1}$ decays, we find $\mathrm{\Gamma }({\chi }_{c1}\to J/\psi e^{+}{e}^{-})=2.869(90)\mathrm{keV}$ and $\mathrm{\Gamma }({\chi }_{c1}\to J/\psi {\mu }^{+}{\mu }^{-})=0.1993(72)\mathrm{keV}$. Our results for the ${\chi }_{c1}$ decays show good compatibility with experimental data. However, our prediction for the $h_c\to {\eta }_c{e}^{+}{e}^{-}$ decay rate is approximately $3\sigma$ larger than the BESIII result. We also present predictions for the differential decay widths as functions of the dilepton invariant mass, $q^2$, and for angular observables sensitive to longitudinal transition form factors, which are inaccessible in radiative decays with real photon emission. These results constitute the first fully dynamical lattice QCD predictions for dilepton decay rates in $h_c$ and ${\chi }_{c1}$ charmonium transitions, including their differential distributions and angular observables. They provide benchmark predictions for future experimental studies.

We study the thermodynamics of the symmetry-improved Cornwall-Jackiw-Tomboulis formalism and apply it to a low-energy effective theory of QCD. In the symmetry-improved formulation, Ward-Takahashi identities are restored by auxiliary sources whose values are fixed self-consistently by the equilibrium state. While this construction improves the symmetry properties of the loopwise truncated two-particle-irreducible (2PI) theory, it also makes the thermodynamic interpretation of the pressure nontrivial. We formulate several pressure prescriptions, including the conventional vacuum-subtracted pressure, a source-matched subtraction, and a pulled-back pressure in which the explicit source-induced energy shift is removed. Using the three-flavor linear sigma model with quarks, we analyze the equation of state, isentropic trajectories, adiabatic sound velocity, and trace anomaly across the chiral transition. We find that the global thermodynamic structure is stable under the different prescriptions, while quantitative differences are concentrated near the crossover and first-order transition region. These results establish a practical framework for constructing thermodynamically consistent observables in symmetry-improved 2PI approaches.

Heavy quark expansion theory provides the standard theoretical framework for understanding the lifetimes of weakly decaying heavy-flavor hadrons. Within this framework, the matrix elements of four-quark operators play a crucial role in explaining the lifetime differences among hadrons containing the same heavy quark. In this work, we calculate these matrix elements at leading order using full QCD sum rules, with particular emphasis on deriving the corresponding HQET sum rules by taking the heavy-quark limit. While this limit is straightforward for most contributions, it turns out to be rather nontrivial for certain ones. Numerical analyses show that the results obtained from the two approaches are consistent with each other. We further clarify the origin of the large discrepancies reported in the literature between full QCD sum rule and HQET sum rule results. This work contributes to a deeper understanding of the relationship between the two sum-rule approaches and is expected to facilitate future applications of QCD and HQET sum rules in the study of heavy-flavor hadrons. The findings presented here may be of interest to both practitioners of QCD sum rules and researchers working on effective field theories.

We present HAPS-hFF1.0, a new global QCD analysis of unidentified charged-hadron fragmentation functions (FFs) using single-inclusive electron-positron annihilation (SIA) data together with the modern COMPASS semi-inclusive deep-inelastic scattering (SIDIS) multiplicities. The COMPASS input consists of the 2025 proton-target measurement and the revised ${}^6\mathrm{LiD}$-target multiplicities provided in the 2026 COMPASS addendum. The extraction is performed at both next-to-leading order (NLO) and next-to-next-to-leading order (NNLO), allowing us to study the perturbative stability of the QCD fit and the impact of the updated SIDIS information on the flavor structure of the FFs. The FFs are parametrized using neural networks, while experimental uncertainties are propagated through a Monte Carlo replica methodology. We find that the modern COMPASS multiplicities can be consistently described together with the SIA data and provide important charge-separated constraints on the light-quark and antiquark FFs. The comparison between the NLO and NNLO extractions indicates a stable quark-sector determination, while the gluon FF remains less directly constrained in the present $\mathrm{SIA}+\mathrm{SIDIS}$ analysis. Our results highlight the importance of the modern COMPASS SIDIS multiplicities for precision studies of unidentified charged-hadron fragmentation and for future global FF determinations. The resulting HAPS-hFF1.0 replicas are publicly available in standard LHAPDF format.

We study the one-loop Polyakov-loop effective potential in pure gluonic matter under constant acceleration. We perform the computation in both the Euclidean Rindler spacetime and the optical spacetime, which are related via a conformal transformation. The results from the two formulations correspond to physically different observables, and we clarify their connection to specific components of the energy-momentum tensor. This identification resolves a discrepancy previously noted for fields on conical backgrounds. For the Polyakov-loop expectation value, we should minimize the effective potential computed in the optical metric formulation, which concludes that real acceleration strengthens deconfining properties. We also discuss analytic continuation from real to imaginary acceleration and find a perturbatively confined phase. We point out some suggestive similarities and differences between systems under imaginary acceleration and imaginary rotation.

The twist-3 transverse spin-dependent nucleon structure function $g_2$ arises in high-energy processes involving a transversely polarized nucleon. Its connection to quark-gluon correlations allows for an interpretation in terms of the average transverse color Lorentz force acting on unpolarized quarks inside a transversely polarized nucleon. In this work, we investigate this force using light-front wave functions obtained by diagonalizing the light-front Hamiltonian with quantum chromodynamics inputs within the basis light-front quantization approach. We evolve our results to a common scale of $5{\mathrm{GeV}}^2$ and present the corresponding form factors in momentum space as well as the transverse force components in impact-parameter space. These distributions provide a complementary perspective on the Sivers asymmetry in transversely polarized deep-inelastic scattering. In the forward limit, we extract the twist-3 reduced matrix element $d_2$, and our results are found to be comparable with those from other theoretical calculations and experimental determinations.

We investigate $J/\psi$ photoproduction off the proton, $\gamma p\to J/\psi p$, to elucidate the nonexistence of hidden-charm pentaquark signals reported by the GlueX and CLAS12 experiments. Within a coupled-channel rescattering mechanism, we employ the transition amplitudes from a previous coupled-channel analysis that dynamically generates the $P_{c\overline{c}}$ states. The kernel amplitudes for the transition to the $J/\psi N$ channel include both $t$-channel heavy-meson exchange and $u$-channel heavy-baryon exchange. We find that the rescattering contributions from the ${\overline{D}}^{(*)}{\mathrm{\Sigma }}_c$ channels—indispensable for the formation of the $P_{c\overline{c}}$ resonances—are about one order of magnitude smaller than those from ${\overline{D}}^{(*)}{\mathrm{\Lambda }}_c$, since $g_{{\overline{D}}^{(*)}N{\mathrm{\Sigma }}_c}$ is roughly 5 times smaller than $g_{{\overline{D}}^{(*)}N{\mathrm{\Lambda }}_c}$. Since the $P_{c\overline{c}}$ resonances couple to the $J/\psi N$ channel predominantly through the ${\overline{D}}^{(*)}{\mathrm{\Sigma }}_c$ intermediate states, their suppression prevents the pentaquark signal from appearing in photoproduction. With only a single parameter controlling the overall normalization, the present work describes the GlueX and CLAS12 cross sections well. These results suggest that the null result from photoproduction need not be in conflict with the pentaquark signals observed by the LHCb Collaboration.

We investigate the electromagnetic form factors of the charged $K^{*+}(892)$ ($\mathrm{u}\overline{s}$) and neutral $K^{*0}(896)$ ($\mathrm{d}\overline{s}$) strange vector mesons within the covariant Nambu–Jona-Lasinio model, employing the Schwinger proper-time regularization scheme to regularize ultraviolet divergences that incorporated the QCD aspect of the quark confinement. To this end, we evaluate the charge (electric) $G_C(Q^2)$, magnetic moment $G_M(Q^2)$, and quadrupole moment $G_Q(Q^2)$ form factors and charge radii of the charged $K^{*+}(892)$ and neutral $K^{*0}(896)$ strange vector mesons. We find that the charge radii are $⟨r^2{⟩}_{K^{*+}}=0.45{\mathrm{fm}}^2$ and $⟨r^2{⟩}_{K^{*0}}=-0.04{\mathrm{fm}}^2$, respectively, while the magnetic moments are found ${\mu }_{K^{*+}}=2.67$ ${\mu }_N$ and ${\mu }_{K^{*0}}=0.032$ ${\mu }_N$, consistent with other theoretical calculations and lattice QCD simulation results.

We present the first computation of next-to-next-to-leading order (NNLO) pure QED and mixed $\mathrm{QCD}\otimes \mathrm{QED}$ corrections to unpolarized and polarized semi-inclusive deep-inelastic scattering (SIDIS). Building on our previous NNLO QCD results, these corrections are crucial for improving the theoretical precision. The coefficient functions are derived within the QCD factorization framework using dimensional regularization, with consistent renormalization and mass factorization. A detailed phenomenological analysis shows that the NNLO QED and $\mathrm{QCD}\otimes \mathrm{QED}$ terms enhance perturbative stability and reduce scale uncertainties. These results are essential for high-precision SIDIS predictions at future facilities such as the Electron-Ion Collider.

In multibody decays of heavy mesons, conventional charge-parity ($CP$) asymmetry observables obtained by integrating over the full phase space are insensitive to the higher-order wave expansion contributions in the decay amplitude squared and consequently fail to retain information on interference effects among different resonances. To overcome this limitation, one can introduce a phase-space partitioning scheme based on the zeros of Legendre polynomials, supplemented by a sign-function weighting procedure. On such a basis, two observables are defined, namely, an asymmetry observable ${\mathcal{A}}_{\pm }^{\mathrm{asy},l}$ and the corresponding $CP$ asymmetry ${\mathcal{A}}_{\mathrm{CP}}^{\mathrm{asy},l}$. We further separate the observables into interference and noninterference parts and analyze their respective roles. As an application, the decay channel $B^{\pm }\to {\pi }^{\pm }{\pi }^{+}{\pi }^{-}$ are analyzed in the region near the ${\rho }^0(1450)$ resonance. Using the LHCb data, the results show that odd-$l$ schemes are particularly effective in isolating interference contributions, while even-$l$ schemes are more sensitive to noninterference terms. This new assignment scheme has the potential to be extended to other decay processes, thus enriching the available physical observables.