Searching for long-lived axionlike particles (ALPs) is a promising direction in collider experiments. In this paper, we explore the potential of the HL-LHC to probe a light long-lived ALP via its production associated with two jets within the photophobic ALP scenario. Specifically, we consider the process $pp\to jja$, where the ALP $a$ decays into a pair of displaced tau leptons, both of which decay hadronically via the 1-prong mode. We find that the prospective sensitivities of the HL-LHC with the center-of-mass energy $\sqrt{s}=14\mathrm{TeV}$ and integrated luminosity $\mathcal{L}=3{\mathrm{ab}}^{-1}$ can reach $g_{aWW}\in [8.92\times {10}^{-3},1.40\times {10}^{-1}]{\mathrm{TeV}}^{-1}$ for the ALP mass $m_a\in [4,10]\mathrm{GeV}$. Our results show that the HL-LHC has significant potential to probe long-lived ALPs via their displaced vertex signatures, complementing previous searches and opening access to some regions of parameter space that remain unexplored by the LHC and LEP.

We investigate the possibility of saturating the relic density bound with light Higgsinos. When the minimal supersymmetric Standard Model is extended with right-handed neutrino superfields and the seesaw scale is very low, right-handed sneutrinos can be produced via the freeze-in mechanism. In such a case, we can have essentially two independent sources for dark matter, the traditional freeze-out of Higgsinos and the freeze-in of right-handed sneutrinos. The heavier of these two will decay to the lighter species with a delay. We rule out such a scenario for all seesaw models as the lifetime of sterile neutrinos produced overabundantly via the Dodelson-Widrow mechanism exceeds the age of the Universe and will contribute to the relic density.

We present a comprehensive investigation into the anomalous magnetic dipole moment ($a_{\tau }$) and electric dipole moment ($d_{\tau }$) of the $\tau$ lepton using the $\gamma \gamma \to {\tau }^{+}{\tau }^{-}$ process at future lepton colliders, with the Super Tau-Charm Facility serving as a benchmark. By employing transverse-momentum-dependent factorization, we introduce novel observables derived from $\cos 2\varphi$, $\sin 2\varphi$, and $\cos 4\varphi$ azimuthal asymmetries to precisely probe the $\tau$ lepton’s electromagnetic structure. Our analysis significantly enhances the precision of $a_{\tau }$ constraints within the photon-photon fusion process, yielding $\mathrm{Re}(a_{\tau })\in [-4.6,7.0]\times {10}^{-3}$ at the $2\sigma$ confidence level, which approaches the precision of the Standard Model prediction. These findings highlight the considerable potential of azimuthal asymmetry measurements for high-precision determinations of fundamental particle properties at future lepton colliders.

We examine electron and muon anomalous magnetic dipole moments within a radiative neutrino mass model featuring TeV-scale scalar leptoquarks $S(3,1,-1/3)$ and $R(3,2,1/6)$. We utilize textures with decoupling electron and muon sectors, so that both electron and muon anomalous magnetic dipole moments could receive internal chiral enhancements from different heavy up-type quarks while in the same time evading the stringent $\mu \to e\gamma$ constraint. A successful fit to neutrino oscillation data requires the simultaneous presence of one- and two-loop neutrino mass contributions. This severely constrains the parameter space of the model, which results in a negligible new physics correction to the muon $g-2$. The electron $g-2$ discrepancy implied by the rubidium experiment, on the other hand, can be resolved within $2\sigma$ uncertainty provided that neutrino mass ordering is inverted. Lepton-flavor-violating tau decay rates, such as $\tau \to e\gamma$ and $\tau \to 3e$, are predicted to be within the sensitivities of next-generation experiments.

Heavy right-handed neutrinos are highly motivated due to their connection with the origin of neutrino masses via the seesaw mechanism. If the right-handed neutrino Majorana mass is at or below the weak scale, direct experimental discovery of these states is possible in laboratory experiments. However, there is no a priori basis to expect right-handed neutrinos to be so light since the Majorana mass is a technically natural parameter and could comfortably reside at any scale, including at scales far above the weak scale. Here we explore the possibility that the right-handed neutrino Majorana mass originates from electroweak symmetry breaking. Working within an effective theory with two Higgs doublets, a nonzero lepton number is assigned to the bilinear operator built from the two Higgs fields, which is then coupled to the right-handed neutrino mass operator. In tandem with the neutrino Yukawa coupling, following electroweak symmetry breaking a seesaw mechanism operates, generating the light Standard Model neutrino masses along with right-handed neutrinos with masses below the electroweak scale. This scenario leads to novel phenomenology in the Higgs sector, which may be probed at the LHC and at future colliders. There are also interesting prospects for neutrinoless double beta decay and lepton flavor violation. We also explore some theoretical aspects of the scenario, including the technical naturalness of the effective field theory and ultraviolet completions of the right-handed neutrino Majorana mass.

We study a novel production and decay mechanism for a biadjoint spin zero particle in the (8, 3, 0) representation of the Standard Model gauge groups. This work is part of a series studying new production processes for exotic particles in higher representations of Standard Model color and weak charge. Here, we study a specific new dimension 5 effective operator model which couples an exotic biadjoint scalar field to the SU(3) and SU(2) field strength tensors. The W-gluon resonant decay of the charged component of this new exotic field is explored. We discuss LHC production modes of both the charged and neutral biadjoint states and find a new single production mode for the charged state. This is the dominant LHC production mode for TeV-scale masses. We introduce a new HL-LHC search in which a single biadjoint is produced in association with a hard forward quark jet from asymmetric W-gluon fusion. This search yields a 5-sigma discovery potential for biadjoint masses up to 3 TeV for 10 TeV scalar effective operator cutoffs. We also find 2-sigma sensitivity at the HL-LHC for biadjoint masses up to 4 TeV and effective cutoffs in the 15 TeV range for the full 3 inverse atto-barn dataset.

We investigate the combination of a two-level sampling algorithm with distillation techniques to compute disconnected fermionic correlation functions. The method relies on a factorization of the quark propagator into domain-local contributions that depend only on the gauge fields within overlapping temporal regions, enabling independent submeasurements of each term through a two-level sampling strategy. The statistical uncertainty follows the expected inverse scaling with the number of second-level submeasurements, up to exponential boundary effects, in contrast to the inverse square-root scaling of standard sampling. This leads to an exponential reduction of statistical errors at negligible additional computational cost compared to the gain in statistical precision. The method is tested on pure gauge ensembles, providing a controlled benchmark for its forthcoming application to dynamical QCD studies.

To understand the nature of $X(2075)$ and $X(2085)$ observed by the BESIII Collaboration in the $p\overline{\mathrm{\Lambda }}$ system, we systematically investigate the possibility that these states are compact hexaquark with triquark-antitriquark configurations for the first time. Within the framework of QCD sum rules, the mass spectrum and decay constants of such hexaquark states with quantum numbers $J^P=0^{-},0^{+},1^{-},1^{+}$ are studied. Consequently, six independent and nondegenerate hexaquark candidates are obtained, among which two $J^P=1^{-}$ states exhibit masses consistent with $X(2075)$, while the two $J^P=1^{+}$ states differ markedly from the mass of $X(2075)$ or $X(2085)$. The remaining two states with $J^P=0^{+}$ and $0^{-}$ may serve as predictions for potential compact hexaquark configurations. Furthermore, the possible decay modes of these hexaquark states are analyzed, which could be the experimental signatures for their identification.

The universality of electric charge as a quantum number allows thermoelectric properties to manifest across diverse systems, starting from a hot quantum chromodynamic matter in heavy-ion collisions at a high energy scale to semiconductors in condensed matter systems at a low energy scale. In this work, we explore the emergence of magneto-transport phenomena, specifically the magneto-Thomson and transverse Thomson effects, in a hot and dense hadronic medium produced in relativistic heavy-ion collisions at the Relativistic Heavy Ion Collider and Large Hadron Collider energies. These phenomena arise due to the combined influence of temperature gradients and non-zero baryon chemical potential, particularly in the presence of an external magnetic field. Using the relativistic Boltzmann transport equation within the relaxation time approximation, we analyze the behavior of the hadronic medium considering different frameworks of hadron resonance gas models. The presence of external magnetic fields breaks the isotropy of the thermoelectric transport coefficient matrix, giving rise to new components of the Thomson coefficient, namely, magneto-Thomson and transverse Thomson coefficients. For the first time, we estimate the magneto-Thomson and transverse Thomson coefficients, which originate from the temperature dependence of the magneto-Seebeck coefficient and Nernst coefficient, respectively, in hadron gas under the influence of a static and time-varying magnetic field. Our findings provide a novel perspective on the higher-order thermoelectric properties of the hot and dense hadronic medium in the context of heavy-ion collisions.

We employ the Born-Oppenheimer approximation to the $T_{c\overline{s}0}^a(2900{)}^0$ and $T_{c\overline{s}0}^a(2900{)}^{++}$ states observed by the LHCb Collaboration and study mass spectrum and root-mean-square radius values. For this purpose, we use the dynamical diquark model. We assume that a strange quark is heavy for the usage of the Born-Oppenheimer approximation. Our results strongly indicate that the $T_{c\overline{s}0}^a(2900)$ states are best described as composed of axial-vector (spin-1) diquark pairs. Furthermore, the calculated root-mean-square radius, $⟨r^2{⟩}^{1/2}\approx 0.70–0.80\mathrm{fm}$, which is significantly less than 1 fm, provides compelling evidence that these are compact tetraquarks rather than loosely bound hadronic molecules.

We provide a precise, model- and parametrization-independent dispersive determination of the $f_0(500)$, $\rho (770)$, $f_0(980)$, $f_2(1270)$, $f_0(1370)$, $\rho (1450)$, $f_0(1500)$, and ${\rho }_3(1690)$ resonance pole parameters. They are obtained from the analytic continuation, by means of continued fractions, of forward dispersion relations, whose input is a recent global dispersive analysis of $\pi \pi$ scattering data. From this dispersive study, we find no indications of other resonant poles below 1.7 GeV. Beyond this energy, we also provide resonance pole parameters from the direct analytic continuation of Global Fits to the three existing incompatible datasets. Depending on the dataset we find poles for the $\rho (1700)$, $f_0(1710)$, $\rho (1900)$, $f_2(1950)$, and $f_0(2020)$ resonances. We also present the Argand diagrams of these Global Fits and illustrate that each resonance does not necessarily have to trace a full circle in the diagram.

In this work, we investigate the two-body nonleptonic decays of double-charmed baryon ${\mathrm{\Omega }}_{cc}^{+}$ within a nonrelativistic quark model, in which the nonfactorizable amplitudes contributed by $W$-exchange diagrams are evaluated under the pole model assumption. To reduce the sensitivity of decay amplitudes to an arbitrary choice of baryon wave functions, we adopt charmed baryon wave functions obtained by solving the Schrödinger equation with a nonrelativistic quark potential model. Our results show that the branching fractions of Cabibbo-favored decays ${\mathrm{\Omega }}_{cc}^{+}\to {\mathrm{\Omega }}_c^0{\pi }^{+}$ and ${\mathrm{\Xi }}_c^{(\prime )+}{\pi }^{+}$, as well as the single Cabibbo-suppressed decays ${\mathrm{\Omega }}_{cc}^{+}\to {\mathrm{\Omega }}_c^0{K}^{+}$, ${\mathrm{\Sigma }}_{cc}^{++}{K}^{-}$, ${\mathrm{\Xi }}_c^{\prime +}\eta$, and ${\mathrm{\Lambda }}_c^{+}{\overline{K}}^0$ can reach up to a few percent. Particularly for the ${\mathrm{\Omega }}_{cc}^{+}\to {\mathrm{\Omega }}_c^0{K}^{+}$ mode, owing to the large factorizable amplitude and constructive pole contributions, the branching fraction is comparable to Cabibbo-favored decays. These decay modes can serve as the discovery channels for the double-charmed baryon ${\mathrm{\Omega }}_{cc}^{+}$ in future experiments, like LHCb and Belle II.

We propose a new axion dark matter detection strategy that employs optical readout of laser beam ellipticity modulations caused by axion-induced electric fields in a microwave cavity, using electro-optic (EO) crystals, enhanced by externally injected radio-frequency (rf) power. Building upon the variance-based probing method [Phys. Rev. D 107, 103005 (2023).], we extend this concept to the optical domain: A weak probe laser interacts with an EO crystal coupled to the resonant microwave cavity field at cryogenic temperatures, and the axion-induced electric field is revealed through induced ellipticity. The injected rf signal coherently interferes with that of the axion field, amplifying the optical response and significantly improving sensitivity. While our EO-based method employs a Fabry-Pérot resonator, we do not require Michelson interferometers. Our method, hence, enables compact, high-frequency axion searches, across the 0.5–50 GHz range. Operating at cryogenic temperatures not only suppresses thermal backgrounds, but, critically, allows the probing method to mitigate the quantum noise. This approach offers a scalable path forward for axion detection over the $\sim (\mathrm{few}-200)\mathrm{\mu }\mathrm{eV}$ mass range—covering the preferred parameter space for the postinflationary Peccei-Quinn axion dark matter—using compact, tunable systems.

We present the first results of the search for sub-MeV fermionic dark matter absorbed by electron targets of germanium using the $205.4\mathrm{kg}·\mathrm{day}$ data collected by the CDEX-10 experiment, with the analysis threshold of 160 eVee. No significant dark matter (DM) signals over the background are observed. Results are presented as limits on the cross section of DM–electron interaction. We present new constraints of cross section in the DM range of $0.1–10\mathrm{keV}/c^2$ for vector and axial-vector interaction. The upper limit on the cross section is set to be $6.8\times {10}^{-46}{\mathrm{cm}}^2$ for vector interaction, and $2.3\times {10}^{-46}{\mathrm{cm}}^2$ for axial-vector interaction at DM mass of $5\mathrm{keV}/c^2$.

We report a direct search for a new gauge boson, $X$, with a mass of $17\mathrm{MeV}/c^2$, which could explain the anomalous excess of $e^{+}{e}^{-}$ pairs observed in the ${}^8\mathrm{Be}$ nuclear transitions. The search is conducted in the charmonium decays ${\chi }_{cJ}\to XJ/\psi (J=0,1,2)$ via the radiative transition $\psi (3686)\to \gamma {\chi }_{cJ}$ using $(2712.4\pm 14.3)\times {10}^6\psi (3686)$ events collected with the BESIII detector at the BEPCII collider. No significant signal is observed, and the updated upper limit on the coupling strength of charm quark and the new gauge boson, ${\epsilon }_c$, is set to be $|{\epsilon }_c|<1.2\times {10}^{-2}$ at 90% confidence level. We also report new constraints on the mixing strength $\epsilon$ between the Standard Model photon and dark photon ${\gamma }^{\prime }$ in the mass range from 5 to $300\mathrm{MeV}/c^2$. The upper limits at 90% confidence level vary within $(2.5–17.5)\times {10}^{-3}$ depending on the ${\gamma }^{\prime }$ mass.

We consider a class of two-dimensional dilaton gravity models with linear dilaton vacuum including Callan-Giddings-Harvey-Strominger (CGHS) model as the special case. General thermodynamic properties of black holes in such models are evaluated. We focus on the CGHS model and its modification with regular black holes as empty-space solutions characterized by ever-present finite curvature. We find generalized entanglement entropy blows up for near-extremal regular black holes considered as remnants. That signaling a possible breakdown of the semiclassical approximation near the end point of evaporation. We conjecture that remnants are unstable and decay by quantum fluctuations into horizonless spacetimes. We give an estimate for the decay amplitude by using a semiclassical regularization method and propose a path to mitigate the unitarity loss problem.

The Euclidean path integral for gravity is enriched by the addition of boundaries, which provide useful probes of thermodynamic properties. Common boundary conditions include Dirichlet conditions on the boundary induced metric; microcanonical conditions, which refers to fixing some components of the Brown-York boundary stress tensor; and conformal conditions, in which the conformal structure of the induced metric and the trace of the extrinsic curvature are fixed. Boundaries also present interesting problems of consistency. The Dirichlet problem is known, under various (and generally different) conditions, to be inconsistent with perturbative quantization of graviton fluctuations, to exhibit thermodynamic instability, or to require infinite fine-tuning in the presence of matter fluctuations. We extend some of these results to other boundary conditions. We find that similarly to the Dirichlet problem, the graviton fluctuation operator is not elliptic with microcanonical boundaries, and the nonelliptic modes correspond to “boundary-moving diffeomorphisms.” However, we argue that microcanonical factorization of path integrals—essentially, the insertion of microcanonical constraints on two-sided surfaces in the bulk—is not affected by the same issues of ellipticity. We also show that for a variety of matter field boundary conditions, matter fluctuations renormalize the gravitational bulk and boundary terms differently, so that the classical microcanonical or conformal variational problems are not preserved unless an infinite fine-tuning is performed.

The tidal forces experienced on an orbit contain, in principle, information about the underlying spacetime an object is moving through. Astronomical observations often probe the properties of tidal forces in the relativistic regime, and could thus in principle be leveraged to examine the properties of strong-field gravity, provided that a general procedure for computing the relativistic tidal tensor is known. Existing techniques for deriving the tidal tensor rely on cumbersome, case-by-case methods. This paper introduces a unified analytical approach to deriving the tidal accelerations experienced by a test particle in any stationary, axisymmetric spacetime. This technique uses standard relativistic frame transformations and is built around the zero angular momentum observer frame. The method’s utility is demonstrated in the four traditional black hole metrics; Schwarzschild, Reissner-Nordström, Kerr, and Kerr-Newman, as well as a particular wormhole metric. As an example of a possible astronomical application of this work, we discuss the concept of the Hills mass, the maximum mass at which a black hole can disrupt a star, and extend its definition to various naked singularity metrics.

Homogeneous and nearly isotropic cosmological models are natural extensions of standard Friedmann cosmologies. Constraining their features is crucial, as any detection of their properties would impact our understanding of inflation and the cosmological principle. Since these models evolve as a set of noninteracting scalar, vector, and tensor modes on top of homogeneous and isotropic spacetimes, their imprints on cosmological observables, particularly the cosmic microwave background (CMB), can be obtained using standard line-of-sight methods. This requires (1) that one resorts on Laplacian eigenmodes on spatially curved spaces and (2) that radial functions for these modes are analytically continued to accommodate complex (i.e., supercurvature) wave numbers. We introduce two line-of-sight integrators implementing the evolution of the CMB anisotropies in these models: anilos, a user-friendly and easy to modify python package, and aniclass, an advanced and efficient extension of the Boltzmann solver class. We discuss possible initial conditions that could generate such fluctuations and provide illustrative examples using our codes. This work offers a pathway for leveraging diverse cosmological datasets to constrain superhorizon anisotropies of the late-time Universe.

Motivated by recent claims of a possible redshift dependence in late-Universe determinations of the Hubble constant ($H_0$), we test the robustness of this behavior using multiple cosmological probes. We perform a joint redshift-binned analysis of $H_0$ across eight bins using late-Universe probes—Pantheon+ type Ia supernova, Dark Energy Spectroscopic Instrument baryon acoustic oscillation, cosmic chronometers, and water megamasers—under three cosmological frameworks: flat $\mathrm{\Lambda }$ cold dark matter, Chevallier-Polarski-Linder, and Padé cosmography. Under a common baseline scheme, all three models show a qualitatively similar, low-amplitude variation in the per-bin $H_0$ estimates. A simple Fourier-like parametrization captures this behavior, but the amplitude differs from zero only at a marginal significance of about $1.71-1.94\sigma$, with similar behavior observed across all three cosmological frameworks. We then investigate the robustness and possible origin of this feature. Alternative binning schemes preserve its qualitative form, whereas single-probe per-bin fits (supernova-only, cosmic chronometer-only, BAO-only) yield ratios $H_{0,i}/H_{0,\text{global}}$ mostly consistent with unity and do not reproduce the pronounced drift seen in the joint baseline constraints. Finally, by comparing different global versus piecewise-constant configurations for $\{H_0,{\mathrm{\Omega }}_m,M,r_d\}$, we find that a baselinelike oscillatory pattern reemerges only when multiple degenerate parameter combinations are allowed to vary across bins, while it is strongly suppressed when only $H_0$ is bin dependent. Taken together, these results indicate that the apparent oscillatory behaviour of $H_0(z)$ in late-time arises from known parameter degeneracies and does not constitute robust evidence for a genuine redshift evolution.