We investigate the exclusive semilpetonic decays of ${\mathrm{\Lambda }}_c^{+}\to (\mathrm{\Lambda }/n){\ell }^{+}{\nu }_{\ell }(\ell =e,\mu )$ within the standard model by using the light-front quark model (LFQM). The form factor behaviors are obtained from the effective treatment of nonvalence contributions in addition to the valence ones in the Drell-Yan-West frame due to the Bethe-Salpeter formalism. Based on these form factors, we find that the decay branching ratios of ${\mathrm{\Lambda }}_c^{+}\to (\mathrm{\Lambda }{e}^{+}{\nu }_e,\mathrm{\Lambda }{\mu }^{+}{\nu }_e,n{e}^{+}{\nu }_e,n{\mu }^{+}{\nu }_e)$ are about $(3.39,3.21,0.36,0.35)\%$ with the nonvalence contributions, which are consistent with the recent experimental measurements at BESIII. Furthermore, we use the experimental data to fit the $\beta$ parameters in the baryonic distribution amplitudes under the LFQM, resulting in (${\beta }_{{\mathrm{\Lambda }}_c},{\beta }_{\mathrm{\Lambda }},{\beta }_n)=(0.58\pm 0.08,0.52\pm 0.08,0.44\pm 0.04)$.

We determine the behavior of an out-of-equilibrium superfluid, composed of a $U(1)$ Goldstone mode coupled to hydrodynamic modes in a Müller-Israel-Stewart theory, in expanding backgrounds relevant to heavy ion collision experiments and cosmology. For suitable initial conditions, the evolution of the hydrodynamic variables leads to a change in the potential of the Goldstone mode, spontaneously breaking the symmetry. After some time, the condensate becomes small, leading the system evolution to be well described via hydrodynamic attractors for a timescale that we determine in Bjorken and Gubser flows. We define this new timescale as the attractor time and show its dependence on initial conditions. In the case of the Gubser flow, we provide for the first time a complete description of the nonlinear evolution of the system, including a novel nonlinear regime of constant anisotropy not found in the Bjorken evolution. Finally, we consider the superfluid in the dynamical Friedmann-Lemaitre-Roberston-Walker (FLRW) background, where we observe a similar attractor behavior, dependent on the initial conditions, that at late times approaches a regime dominated by the condensate.

We investigate a chirally imbalanced medium in the context of the two-flavor Nambu-Jona-Lasinio model using both the large-$N_c$ (LN) and beyond large-$N_c$ (BLN) approximations. To incorporate BLN effects, we consider the optimized perturbation theory (OPT) to the first nontrivial order, which includes two-loop (exchange) contributions. This procedure allows us to explicitly explore how finite $N_c$ corrections affect the thermodynamics as well as the phase diagram of chirally imbalanced quark matter. We then compare the results obtained with a sharp three-dimensional cutoff—generically referred to as the traditional regularization scheme—and with an alternative procedure called the medium separation scheme (MSS). In the first case, we observe that the pseudocritical temperature decreases as the chiral chemical potential increases, an effect dubbed inverse chiral catalysis. On the other hand, when considering the MSS regularization, which properly isolates the medium contributions from the vacuum, we find the opposite result. We show that the results obtained with MSS are consistent with well-established lattice quantum chromodynamics data in both the LN and BLN approximations. Finally, we suggest that to cope with the high-density limit, the standard OPT interpolation prescription must be modified with the inclusion of an extra variational parameter.

The $t$-channel singularity is a divergence in the scattering amplitude which occurs when a stable particle propagating in $t$-channel scattering process becomes an on-shell state. Such situations appear either in the system of collider experiments or in the context of the cosmological particle production. No scheme which is generally applicable is known. In this work, we propose a new formulation to identify and remove the source of the divergence. The scheme is fully analytical and various applications can be expected. This work provides a valuable tool in this research field.

We demonstrate the importance of relativistic corrections for the study of the stability of ($2+1$)-dimensional nontopological solitons with quartic self-interaction in the low-energy limit. This result is explained by the restoration of conformal symmetry in the nonrelativistic limit. Particularly, the corresponding cubic Gross-Pitaevskii equation supports scale-free nontopological solitons. An unbroken conformal symmetry provides the additional degeneration that allows for the exact result for the energy and angular momentum of the stationary classical solutions. We study the violation of conformal symmetry by relativistic corrections. The emergence of exponentially growing modes on the classical background is demonstrated using analytical approximations and numerical calculations.

Using Monte Carlo techniques, we calculate the bremsstrahlung spectrum that protons and electrons in the solar wind would produce when encountering dark matter (DM) particles within the solar system. We consider two types of interactions for the DM: one where a spin-$1/2$ neutral DM particle interacts with matter through the exchange of a lighter neutral scalar DM particle and one where a scalar neutral DM particle interacts directly with the matter particle. We consider three wavelengths: 21 cm, 3 mm, and $12\mathrm{\mu }$. To estimate the significance of the signal, we compare our results to experimental results from ARCADE2 and PLANCK and consider the sensitivities of three telescopes: VLA, ALMA, and KECK. We find that in order to produce an observable signal in the first scenario the neutral fermion must have a mass comparable to the solar wind particle while the exchanged particle must have a mass typically $\mathrm{few}\times {10}^5$ smaller. The scalar direct interaction, however, appears beyond reach for any reasonable coupling.

The color-triplet partner of the Higgs doublet, called a $T$-particle, is a universal feature of grand unification. It was shown some time ago that this particle can be accessible for direct production in collider experiments. In this paper, we point out that the $T$-particle represents a simultaneous low-energy probe of baryon number violation as well as of the origin of the neutrino mass, linking the mediation of proton decay with oscillations of the neutron into a sterile neutrino. We point out a triple correlation between its collider signatures, proton decay measurements, and the searches for the magnetic resonance disappearance of free neutrons in cold neutron experiments. In this way, the $T$-particle can provide a diversity of correlated experimental windows into grand unification.

The phenomenology of the flipped two-Higgs-doublet model (2HDM) is relatively less explored so far, as compared to the other, commonly discussed, types. It is found that this scenario, like several others, admits of a light neutral pseudoscalar $A$ in the mass range 20–60 GeV, consistently with all current experimental data and theoretical constraints. However, the fact that such a pseudoscalar decays overwhelmingly into a $b\overline{b}$ pair makes its identification at the Large Hadron Collider (LHC) a challenging task. After identifying the region of the flipped 2HDM parameter space yielding a light pseudoscalar, we identify a useful search channel in the process $pp\to AZ(Z^{*})\to b\overline{b}{\ell }^{+}{\ell }^{-}$. A cut-based analysis, followed by one based on boosted decision trees, shows that the light-$A$ scenario in flipped 2HDM should be detectable with rather high statistical significance at the high-luminosity LHC run, even after including systematic uncertainties. Furthermore, part of the parameter space, especially around $m_A=30–40\mathrm{GeV}$, is amenable to detection at the discovery level within Run-2 itself.

We systematically apply the Born-Oppenheimer approximation to show that the Migdal effect in a solid crystal is entirely due to nonadiabatic effects, namely the deviation of the wave function from exact factorization of the electronic and nuclear contributions. The matrix element obtained this way matches exactly the result found by means of a previously derived low energy effective theory.

We show using the Hamiltonian formalism that if parity is a good symmetry of QCD, then the strong $CP$ phase $\overline{\theta }$ must be 0 or $\pi$. We find that for $P$ to be a physical symmetry, it must leave the Hilbert space ${\mathcal{H}}_{\theta }$ associated with the $\theta$-vacuum invariant ($P:{\mathcal{H}}_{\theta }\to {\mathcal{H}}_{\theta }$), which is possible only for $\theta =0$ or $\pi$. We also show that forming linear combinations of states from different $\theta$ sectors produces only classical statistical mixtures, consistent with superselection rules, confirming that ${\mathcal{H}}_{\theta }$ is the most general Hilbert space for the quantum theory. Furthermore, we demonstrate that requiring $[P,\mathrm{\Omega }]=0$—where $\mathrm{\Omega }$ is the generator of large gauge transformations—independently enforces $\overline{\theta }=0$ (mod $\pi$), and that for complex quark mass matrix $M$, if a generalized parity operator $\mathcal{P}$ is a symmetry, then the value of $\theta$ gets determined so that it exactly cancels $ArgDetM$, again giving $\overline{\theta }=0(\mathrm{mod}\pi )$. These results establish the equivalence of the Hamiltonian and Lagrangian approaches to the strong $CP$ problem.

We investigate the potential of precision Higgs boson coupling measurements to discover heavy Higgs bosons by performing scans of the parameter space in two-Higgs-doublet models. Our study encompasses conventional type I and type II models, as well as models in which Higgs couplings differ between the third-generation and lighter fermion generations. The scans reveal that precision measurements at the sensitivity levels projected for Higgs factories, such as the Linear Collider Facility (LCF) and the Future Circular Collider (FCC-ee) at CERN and the Circular Electron-Positron Collider (CEPC) in China, are capable of probing heavy Higgs boson masses in the multi-TeV range, with sensitivity extending beyond 5 TeV in certain scenarios. In particular, the precise determination of the charm quark Yukawa coupling at Higgs factories provides a powerful test of the hypothesis that the fermion mass hierarchy arises from an extended Higgs sector with different Higgs fields coupling to the different generations of fermions.

We systematically investigate the possible phenomenological impact of residual flavor groups in the charged lepton sector. We consider all possible flavor charge assignments for Abelian residual symmetries up to ${\mathbb{Z}}_8$. The allowed flavor structures of operators in Standard Model effective field theory (up to dimension six) lead to distinctive and observable patterns of charged lepton flavor violating processes. We illustrate the relevance of such selection rules displaying the current bounds on and the future sensitivities to the new physics scale. These results demonstrate, in particular, the importance and discriminating power of searches for lepton flavor violating $\tau$ lepton decays and muonium to antimuonium conversion.

We perform a precise calculation of physical quantities related to the axial structure of the nucleon using $2+1$ flavor lattice QCD gauge configuration (PACS10 configuration) generated at the physical point with lattice volume larger than $(10\mathrm{fm}{)}^4$ by the PACS Collaboration. The nucleon matrix element of the axial-vector current has two types of the nucleon form factors, the axial-vector ($F_A$) form factor and the induced pseudoscalar ($F_P$) form factor. Recently, lattice QCD simulations have succeeded in reproducing the experimental value of the axial-vector coupling, $g_A$, determined from $F_A(q^2)$ at zero momentum transfer $q^2=0$, at a percent level of statistical accuracy. However, the $F_P$ form factor so far has not reproduced the experimental values well due to strong $\pi N$ excited-state contamination. Therefore, we propose a simple subtraction method for removing the so-called leading $\pi N$-state contribution. This method succeeds in reproducing the values obtained by two experiments of muon capture on the proton and pion electroproduction for $F_P(q^2)$. The novel approach can also be applied to determine the pseudoscalar ($G_P$) form factor from the nucleon pseudoscalar matrix element with the help of the axial Ward-Takahashi identity. The resulting form factors, $F_P(q^2)$ and $G_P(q^2)$, are in good agreement with the prediction of the pion-pole dominance model. In the new analysis, the induced pseudoscalar coupling $g_P^{*}$ and the pion-nucleon coupling $g_{\pi NN}$ can be evaluated with a few percent accuracy including systematic uncertainties using existing data calculated at two lattice spacings.

We perform a lattice calculation of the correlators of two chromoelectric fields in the adjoint representation connected by adjoint Wilson lines at nonzero temperature. These correlators arise in the study of quarkonium dynamics and of adjoint heavy quark diffusion in deconfined matter. We work in SU(3) gauge theory using either gradient flow or multilevel algorithms for noise reduction, and discuss the renormalization of the correlators on the lattice. We find that a Casimir factor rescaling relates the adjoint correlators corresponding to the diffusion of an adjoint heavy quark and the octet-octet quarkonium transitions to the chromoelectric correlator in the fundamental representation describing the diffusion of a heavy quark.

We present the perturbative results of the discretization errors proportional to the quark mass [$\mathcal{O}(am)$] on the QCD running coupling within lattice perturbation theory. Our analysis involves calculating the two-loop renormalization factor $Z_g$ using improved lattice actions for the $SU(N_c)$ gauge group and $N_f$ multiplets of fermions with a finite quark mass. We employ the background field method to compute $Z_g$, by calculating quantum corrections on both the background and quantum gluon propagator, respecting the $\mathcal{O}(a)$ improvement. This allows us to evaluate the perturbative $\mathcal{O}(am)$ lattice errors which affect the determination of the running coupling. Eliminating these $\mathcal{O}(am)$ effects is crucial for the nonperturbative studies of precision determinations of the strong coupling constant using lattice field theory.

We present an efficient method for extracting energy levels from lattice QCD correlation functions by computing the eigenvalues of the transfer matrix associated with the lattice QCD Hamiltonian. While mathematically and numerically equivalent to the recently introduced Lanczos procedure [1], our approach introduces a novel prescription for removing spurious eigenvalues using a kernel density estimator and Gaussian-convoluted histogram method. This strategy yields a robust and stable estimate of the energy spectrum, outperforming the Cullum-Willoughby filtering technique in efficiency. In addition, we detail how this method can be applied to extract overlap factors from two-point correlation functions, as well as matrix elements from three-point functions with a current insertion. Furthermore, we extend the methodology to accommodate correlation matrices constructed from a variational basis of operators, with its block formulation. We demonstrate the efficacy of this framework by computing the two lowest energy levels for a broad range of hadrons, including several nuclei. Although the signal-to-noise ratio is not significantly improved, the extracted energy levels are found to be more reliable than those obtained with conventional techniques. Within a given statistical ensemble, the proposed method effectively captures both statistical uncertainties and systematic errors, including those arising from the choice of fitting window, making it a robust and practical tool for lattice QCD analysis.

By adopting a hadron-structure-oriented approach, we present and discuss the release of the novel OMG3Q1.0 set of collinear fragmentation functions for fully charmed, rare $\mathrm{\Omega }$ baryons. Our methodology combines diquarklike proxy model inputs for both charm-quark and gluon channels, calculated at the initial energy scales, with a Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution that ensures a consistent treatment of heavy-quark thresholds, following directly from the heavy-flavor nonrelativistic evolution scheme. We complement our work with a phenomenological study of next-to-leading logarithm/next-to-leading order plus resummed ${\mathrm{\Omega }}_{3c}$ plus jet distributions using (sym)jethad at the HL-LHC and the future FCC. Unraveling the production mechanisms of rare, yet-unobserved hadrons, as provided by the OMG3Q1.0 functions, stands as a key asset for deepening our understanding of QCD at future high-energy hadron colliders.

The longitudinal structure function for nucleons and nuclei is considered at fixed $\sqrt{s}$ and $Q^2$ to the minimum value of $x$ given by $Q^2/s$. This is done using the expansion method and color dipole model in the next-to-leading order approximation. The extracted longitudinal structure functions were consistent with HERA hepdata and the determination of $F_L$ at $x=Q^2/s$ [Taylor, Phys. Rev. D 111, 052001 (2025)] at moderate and large $Q^2$ values. The results, consistent with the dipole picture at low $Q^2$ values, show that the longitudinal structure function is small as expected due to the transverse polarization of the exchanged photon and the strong suppression of the dominant gluon component. Nonlinear corrections to the nuclear longitudinal structure function at low values of $x$ and $Q^2$ are also considered. These results may enhance the deep inelastic scattering neutral current data in future colliders at low $x$ and low $Q^2$. The longitudinal structure functions for deuterium at low four-momentum transfer squared, $Q^2<1{\mathrm{GeV}}^2$ at the leading order and next-to-leading order approximations are determined and compared with the JLab E00-002 data.

Recently, the BESIII Collaboration observed a $\rho$-like structure $Y(2044)$ in $e^{+}{e}^{-}\to a_2(1320)\pi$, suggesting that $Y(2044)$ may be a candidate of vector meson $\rho (2D)$ by comparing resonance parameters. However, the theoretical prediction for the combined branching ratio ${\mathrm{\Gamma }}_{e^{+}{e}^{-}}{\mathcal{B}}_{a_2(1320)\pi }$ for the pure $\rho (2D)$ state is about 2 orders of magnitude smaller than the experimental value. To resolve this discrepancy and decipher the nature of $Y(2044)$, this work proposes an $S\text{−}D$ mixing scheme to reanalyze the cross section of $e^{+}{e}^{-}\to a_2(1320)\pi$, and finds that the aforementioned branching ratio discrepancy can be resolved. Our results show that the $Y(2044)$ structure can be reproduced by introducing four theoretically predicted $S\text{−}D$ mixing $\rho$ meson states ${\rho }_{3S-2D}^{\prime }$, ${\rho }_{3S-2D}^{\prime \prime }$, ${\rho }_{4S-3D}^{\prime }$, and ${\rho }_{4S-3D}^{\prime \prime }$ as intermediate resonances, in which dominant contribution arises from ${\rho }_{3S-2D}^{\prime \prime }$ and their inference effect is also significant. Furthermore, we reanalyzed five additional isospin vector processes $e^{+}{e}^{-}\to \omega {\pi }^0$, $e^{+}{e}^{-}\to f_1(1285){\pi }^{+}{\pi }^{-}$, $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$, $e^{+}{e}^{-}\to \rho \eta$, and $e^{+}{e}^{-}\to {\eta }^{\prime }{\pi }^{+}{\pi }^{-}$ based on the same $S\text{−}D$ mixing framework, and simultaneously reproduced their experimental cross section data. This work provides a unified framework to elucidate all observed $\rho$-like structures near 2 GeV in the $e^{+}{e}^{-}$ annihilation processes, and suggests that the $S\text{−}D$ mixing effect may be crucial for understanding the mass spectrum and decay behaviors of the higher $\rho$ meson states.

This study investigates the mass spectra and decay behaviors of the experimentally unobserved $1F$-wave singly bottom baryons. Calculating their mass spectra could provide crucial guidance for determining their spectroscopic positions. Additionally, by analyzing their decay properties, we could predict the important decay channels, which are essential for experimental searches and quantum number assignments. Our calculations aim to support ongoing experimental and theoretical efforts in singly bottom baryon spectroscopy.