The inclusive production of pseudoscalar heavy quarkonia (${\eta }_c$, ${\eta }_b$, and $B_c$) via photon-photon fusion in heavy ion ultraperipheral collision (UPC) are calculated to QCD next-to-leading order in the framework of nonrelativistic QCD (NRQCD). The total cross section of ${\eta }_c$ produced in Pb-Pb UPC is $194\mathrm{nb}$ and $1275\mathrm{nb}$ at nucleon-nucleon c.m. energies $\sqrt{S_{\mathrm{NN}}}=5.52\mathrm{TeV}$ and 39.4 TeV, respectively. The cross sections for ${\eta }_b$ and $B_c$ mesons are more than two to three orders of magnitude smaller. We make a detailed phenomenological analysis on the ${\eta }_c$ production; the uncertainties caused by the renormalization scale and the charm quark mass, the cross sections in other ultraperipheral nucleon-nucleon colliding systems, and the transverse momentum distribution are discussed. At the coming HL-LHC and future FCC, the heavy ion UPC opens another door of the study on the production of heavy quarkonium.

We study the production of hyperon resonances in the ${\pi }^{+}p\to p{a}_0^{+}\varphi$ reaction within an effective Lagrangian approach. The model includes the production of $\mathrm{\Delta }(1940)$ and $\mathrm{\Delta }(1920)$ in the intermediate state excited by the $\rho$ and $p$ exchanges between the initial proton and $\pi$ meson. Because of the large contribution of $\rho$ exchange in $\mathrm{\Delta }(1940)$ production, $\mathrm{\Delta }(1940)$ is found to be a significant contribution near the threshold in this reaction. We provide total and differential cross section predictions for the reaction and discuss the possible influence of model parameters, off-shell effects, and branching ratios for $\mathrm{\Delta }(1940)\to p{a}_0$ and $\mathrm{\Delta }(1920)\to p{a}_0$ decays, which will be useful in future experimental studies. This reaction can provide a platform for studying the features of $\mathrm{\Delta }(1940)$ resonance, especially the coupling to the $p{a}_0$ channel.

We obtain the value of the magnetic dipole moment of the $\rho$ meson, using data from the BABAR collaboration for the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}2{\pi }^0$ process. The considered center of mass energy range is from 0.9 to 1.8 GeV. We describe the ${\gamma }^{*}\to 4\pi$ vertex using a vector meson dominance model, including the intermediate resonant contributions relevant at these energies. We find ${\mu }_{\rho }=2.7\pm 0.3$ in $e/2m_{\rho }$ units. We improve on the previous extracted value, where preliminary data from the same collaboration was used, by considering definite data, better grounded values of the parameters involved, and an explicit gauge invariant description of the process.

Since its discovery in 1977, the spin parity of $\mathrm{\Xi }(2030)$ has not been fully determined experimentally. The latest Particle Data Group listing suggests it may be a baryon with $J=5/2$. Therefore, studying the mass spectrum and decay properties of $\mathrm{\Xi }(2030)$ has become a current hot topic to definitively establish its spin parity. As the three-quark model fails to explain $\mathrm{\Xi }(2030)$, we previously proposed it may be a molecule primarily composed of ${\overline{K}}^{*}\mathrm{\Sigma }$ with $J^P=5/2^{+}$, based on its mass spectrum study. To verify its molecular state interpretation, this work proposes studying the strong decays of $\mathrm{\Xi }(2030)$ assuming it is a $P$-wave $J^P=5/2^{+}$ meson-baryon molecule predominantly composed of ${\overline{K}}^{*}\mathrm{\Sigma }$. We calculated all experimentally measured two-body and three-body final state decay widths of $\mathrm{\Xi }(2030)$, including $\mathrm{\Xi }(2030)\to \overline{K}\mathrm{\Lambda },\overline{K}\mathrm{\Sigma },\pi \mathrm{\Xi },\pi {\mathrm{\Xi }}^{*}$, and $\mathrm{\Xi }(2030)\to \pi \pi \mathrm{\Xi },\pi \overline{K}\mathrm{\Sigma },\pi \overline{K}\mathrm{\Lambda }$. The results indicate that both the total decay width and partial decay widths agree well with experimental values within the error margins. This supports that $\mathrm{\Xi }(2030)$ is a molecule with spin-parity $J^P=5/2^{+}$, predominantly composed of ${\overline{K}}^{*}\mathrm{\Sigma }$. Compared to the experimental central values, our results are slightly smaller, which suggests that $\mathrm{\Xi }(2030)$ may contain additional components besides meson-baryon molecular components, such as three-quark structures.

In this work, we investigate angular observables such as the longitudinal polarization of charged leptons, $\tau$-polarization, and forward-backward asymmetry in semileptonic $B_c$ decays. Additionally, we provide predictions for lepton flavor violating observables, the $\mathcal{R}$ ratios in the decay channels $B_c\to {\eta }_c(J/\psi )l{\nu }_l$ and $B_c\to D(D^{*})l{\nu }_l$ across the entire $q^2$ region. Our analysis is conducted within the relativistic independent quark model, focusing on the potential model-dependent aspects of these observables. We compare our model predictions with existing lattice predictions, highlighting the strong applicability of our framework in describing $B_c$ decays. Considering the forthcoming experimental upgrades and the Run 3 data results on $B_c$ meson decays, rapid confirmation of these quantities could indicate significant discoveries of physics beyond the Standard Model. This may open up new avenues for understanding the complex flavor dynamics in heavy meson decays.

We study the classical nonlinear dynamics of the $SU(2)$ Yang-Mills matrix model introduced in [Mod. Phys. Lett. A 30, 1550080 (2015)] as a low-energy approximation to two-color QCD. Restricting to the spin-0 sector of the model, we unearth an unexpected tetrahedral symmetry, which endows the dynamics with an extraordinarily rich structure. Among other things, we find that the spin-0 sector contains coexisting chaotic subsectors as well as nested chaotic “basins”, and displays alternation between regular and chaotic dynamics as energy is varied. The symmetries also grant us a considerable amount of analytic control which allows us to make several quantitative observations. We see that the classical spin-0 sector has a rich phase structure, arising from ergodicity breaking. Surprisingly, we find that many of these classical phases display numerous similarities to previously discovered quantum phases of the spin-0 sector [J. Math. Phys. (N.Y.) 58, 022103 (2017)], and we explore these similarities in a heuristic fashion.

We revisit the hard QCD contributions to the pion gravitational form factors, in terms of the twist-2,3 pion distribution amplitudes (DAs), including novel semihard contributions from the instantons. The pion DAs are evaluated in the QCD instanton vacuum and then properly evolved to higher resolution. The results are compared to our recent results from the QCD instanton vacuum, as well as Bethe-Salpeter calculations and recent lattice data. The interpolated hard and soft contributions to the pion $D$ form factor are used to derive the (gravitational) pressure and shear within the pion, with a clear delineation of their range.

The pion form factors of the QCD energy-momentum tensor (EMT) are studied in the instanton liquid model (ILM) of the QCD vacuum. In this approach, the breaking of conformal symmetry is encoded in the form of stronger-than-Poisson fluctuations in the number of instantons. For the trace of the EMT, it is shown that the gluonic trace anomaly term contributes half the pion mass, with the other half coming from the quark-mass-dependent $\sigma$ term. The $Q^2$ dependence of the form factors is governed by glueball and scalar meson exchanges. For the EMT, the spin-0 (trace) and spin-2 (traceless rank-2 tensor) form factors are computed at next-to-leading order in the instanton density using effective quark operators. Relations between the gluon and quark contributions to the EMT form factors are derived. The form factors are also expressed in terms of the pion light-front wave functions in the ILM. The results at the low resolution scale of the inverse instanton size are evolved to higher scales using the renormalization group equation. The ILM results compare well with those of recent lattice QCD calculations.

Using a sample of $(10087\pm 44)\times {10}^{6}J/\psi$ events collected by the BESIII detector at the BEPCII collider, we search for the decay $X(1870)\to K^{+}{K}^{-}\eta$ via the $J/\psi \to \omega K^{+}{K}^{-}\eta$ process for the first time. No significant $X(1870)$ signal is observed. The upper limit on the branching fraction of the decay $J/\psi \to \omega X(1870)\to \omega K^{+}{K}^{-}\eta$ is determined to be $9.55\times {10}^{-7}$ at the 90% confidence level. In addition, the branching faction $B(J/\psi \to \omega K^{+}{K}^{-}\eta )$ is measured to be $(3.33\pm 0.02(\mathrm{stat})\pm 0.12(\mathrm{syst}))\times {10}^{-4}$.

Previous studies have shown that an Unruh-DeWitt (UDW) detector, when coupled linearly to a massless scalar field and permitted to fall radially into certain black holes, will exhibit nonmonotonicity in its transition properties near the horizon. Specifically, the transition probability of a detector freely falling into a ($3+1$)-dimensional Schawrzschild black hole, when considering the Unruh and Hartle-Hawking vacuum states, was shown to possess a local extremum at horizon crossing [K. K. Ng et al., New J. Phys. 24, 103018 (2022)]. The transition rate of a detector falling into a static ($2+1$)-dimensional Bañados-Teitelboim-Zanelli (BTZ) black hole, for the Hartle-Hawking state, was also found to have multiple local extrema near the horizon under certain parameter settings [M. R. Preciado-Rivas et al., arXiv:2402.14908v1]. These discoveries are of interest, as they suggest that the event horizon of a black hole may be discerned by a local probe when quantum field theory effects are included. In this paper, we explore the problem of a UDW detector falling freely into a rotating BTZ black hole. We numerically compute the detector’s transition rate for different values of black hole mass, black hole angular momentum, detector energy gap, and field boundary conditions at infinity. Our results lead to a more generalized description of the behavior of particle detectors in BTZ black hole spacetime, from which the previous nonrotating BTZ case can be retrieved in the limit as angular momentum vanishes.

In the existing body of literature, numerous waveforms of core collapse supernovae (CCSN) have emerged from extensive simulations conducted in high-performance computing facilities globally. These waveforms exhibit distinct characteristics related to their explosion mechanisms, influenced by parameters such as progenitor mass, angular momentum, gravitational wave energy, peak frequency, duration, and equation of state. Core collapse supernovae stand out as highly anticipated sources in LIGO’s fourth observation (O4) run, prompting dedicated efforts to detect them. The integration of machine learning, specifically convolutional neural networks (CNN), has become a pivotal avenue for analysis. This study addresses a fundamental query: how can a CNN be comprehensively trained to capture all potential CCSN signatures, optimizing accuracy? The investigation presents a multivariate classification of the entire supernova waveform landscape to strategically select training waveforms that maximize the feature space. Rigorously tested on both known and unknown waveforms, the method achieves a classification accuracy of $\ge 90\%$. This approach has been seamlessly incorporated into the multilayer signal enhancement with coherent wave burst and CNN (MuLaSEcC) analysis pipeline, showcasing promising outcomes using LIGO O3b data. Noteworthy improvements include a reduction in background by $\ge 99\%$, along with the calculation of detection efficiencies for ten contemporary explosion models. The paper evaluates the search pipeline’s performance by illustrating detection probability as a function of false alarm rate and false alarm probability. The results highlight a $\ge 50\%$ detection efficiency within an SNR range of 20–35 for the ten analyzed models, whether trained or untrained. Time-frequency images of CCSN signals detected by the pipeline show broadband features of the CCSN waveforms that are predicted in the simulations.

Conformal electrodynamics is a particularly interesting example of power Maxwell nonlinear electrodynamics, designed to possess conformal symmetry in all dimensions. In this paper, we propose a regularized version of conformal electrodynamics, minimally regularizing the field of a point charge at the origin by breaking the conformal invariance of the theory with a dimensionful “Born-Infeld-like” parameter. In four dimensions the new theory reduces to the recently studied regularized Maxwell electrodynamics, distinguished by its “Maxwell-like” solutions for accelerated and slowly rotating black hole spacetimes. Focusing on three dimensions, we show that the new theory shares many of the properties of its four-dimensional cousin, including the existence of the charged $C$-metric solution (currently unknown in the Maxwell theory).

We introduce a population model to analyze the mixing between hypothesised power-law and $\sim 35M_{\odot }$ Gaussian-bump black hole populations in the latest gravitational wave catalog, GWTC-3, estimating their colocation and separation. We find a relatively low level of mixing, ${3.1}_{-3.1}^{+5.0}\%$, between the power-law and Gaussian populations, compared to the percentage of mergers containing two Gaussian-bump black holes, ${5.0}_{-1.7}^{+3.2}\%$. Our analysis indicates that black holes within the Gaussian bump are generally separate from the power-law population, with only a minor fraction engaging in mixing and contributing to the $\mathcal{M}\sim 14M_{\odot }$ peak in the chirp mass. This leads us to identify a distinct population of binary Gaussian black holes (BGBHs) that arise from mergers within the Gaussian bump. We suggest that current theories for the formation of the massive $35M_{\odot }$ Gaussian-bump population may need to reevaluate the underlying mechanisms that drive the preference for BGBHs.

In this work, we study the charmonium spectrum within an unquenched quark model including coupled-channel effects. In couple-channel calculations, we include all of the opened charmed meson channels with the once-subtracted method, meanwhile we adopt a suppressed factor to soften the hard vertices given by the ${}^3{P}_0$ model in the high momentum region. We obtain a good description of both the masses and widths for the well-established states in the charmonium spectrum. Furthermore, we give predictions for the higher $S$-, $P$-, and $D$-wave charmonium states up to mass region of $\sim 5.0\mathrm{GeV}$. The magnitude of mass shifts due to the coupled-channel effects is estimated to be about $10s$ MeV. Although many decay channels are opened for the higher charmonium states, they are relatively narrow states. Their widths scatter in the range of $\sim 10s–100\mathrm{MeV}$. Many charmoniumlike states, such as ${\chi }_{c1}(4274)$, ${\chi }_{c0}(3915)$, ${\chi }_{c0}(4500)$, ${\chi }_{c0}(4700)$, $X(4160)$, $X(4350)$, $Y(4500)$, and $\psi (4660)/Y(4710)$, can be accommodated by the charmonium spectrum when the unquenched coupled-channel effects are carefully considered.

Light scalar and pseudoscalar particles are compelling dark matter candidates, with a vast running experimental program to discover them. Previous studies have shown that these light fields can generate sizable isocurvature perturbations in high scale inflationary models. Thereby, dark matter existence and cosmic microwave background measurements impose an upper bound on the inflationary scale. In this work, focusing on the axion case, we point out that light fields present during inflation can generate important isocurvature perturbations also in scenarios of low-scale inflation. In our mechanism, the axion field starts with some nonzero field value during inflation and rolls along its potential. Since inflation has a different duration in different patches of the Universe, different regions will then have different values of the axion field, generating cold dark matter isocurvature modes. These modes are fully correlated with the adiabatic ones and share the same spectral index. In this scenario, the axion mass determines a lower bound on the Hubble parameter during inflation.

In this paper, we explore the interactions between light axionlike particles (ALPs) and top quarks, gluons, and $W$-bosons. Utilizing high-energy probes at the LHC, we probe these couplings in the context of single top quark production associated with a $W$-boson and an ALP. We analyze the latest LHC Run II data on $t\overline{t}$ spin correlation measurements to establish constraints on these couplings. Additionally, we compare these constraints with those derived from loop-induced couplings and indirect searches involving $B$-meson decays. Furthermore, we derive two-dimensional limits on the ALP couplings with top quarks and gluons.

We study the $\overline{b}\overline{b}ud$ tetraquark with quantum numbers $I(J^P)=0(1^{+})$ as well as the $\overline{b}\overline{b}us$ tetraquark with quantum numbers $J^P=1^{+}$ using lattice QCD. We improve on existing work by including both local and scattering interpolating operators on both sides of the correlation functions and use symmetric correlation matrices. This allows not only a reliable determination of the energies of QCD-stable tetraquark ground states, but also of low-lying excited states, which are meson-meson scattering states. The latter is particularly important for future finite-volume scattering analyses. Here, we perform chiral and continuum extrapolations of just the ground-state energies, for which finite-volume effects are expected to be small. Our resulting tetraquark binding energies, $-100\pm {10}_{-51}^{+36}\mathrm{MeV}$ for $\overline{b}\overline{b}ud$ and $-30\pm 3_{-31}^{+11}\mathrm{MeV}$ for $\overline{b}\overline{b}us$, are consistent with other recent lattice-QCD predictions.