The near-threshold photo or electroproduction of heavy vector quarkonium off the proton is studied in quantum chromodynamics. Similar to the high-energy limit, the production amplitude can be factorized in terms of gluonic generalized parton distributions and the quarkonium distribution amplitude. At the threshold, the threshold kinematics has a large skewness parameter $\xi$, leading to the dominance of the spin-2 contribution over higher-spin twist-2 operators. Thus, threshold production data are useful to extract the gluonic gravitational form factors, allowing studying the gluonic contributions to the quantum anomalous energy, mass radius, spin, and mechanical pressure in the proton. We use the recent GlueX data on the $J/\psi$ photoproduction to illustrate the potential physics impact from the high-precision data from the future Jefferson Laboratory 12 GeV and Electron-Ion Collider physics program.

We consider a gauge-invariant, mass-independent prescription for renormalizing composite operators, regularized on the lattice, in the spirit of the coordinate space (X-space) renormalization scheme. The prescription involves only Green’s functions of products of gauge-invariant operators, situated at distinct spacetime points, in a way as to avoid potential contact singularities. Such Green’s functions can be computed nonperturbatively in numerical simulations, with no need to fix a gauge; thus, renormalization to this “intermediate” scheme can be carried out in a completely nonperturbative manner. Expressing renormalized operators in the $\overline{\mathrm{MS}}$ scheme requires the calculation of corresponding conversion factors. The latter can only be computed in perturbation theory, by the very nature of $\overline{\mathrm{MS}}$; however, the computations are greatly simplified by virtue of the following attributes: (i) In the absence of operator mixing, they involve only massless, two-point functions; such quantities are calculable to very high perturbative order. (ii) They are gauge invariant; thus, they may be computed in a convenient gauge (or in a general gauge, to verify that the result is gauge independent). (iii) Where operator mixing may occur, only gauge-invariant operators will appear in the mixing pattern: unlike other schemes, involving mixing with gauge-variant operators (which may contain ghost fields), the mixing matrices in the present scheme are greatly reduced; still, computation of some three-point functions may not be altogether avoidable. We exemplify the procedure by computing, to lowest order, the conversion factors for fermion bilinear operators of the form $\overline{\psi }\mathrm{\Gamma }\psi$ in QCD. We also employ the gauge-invariant scheme in the study of mixing between gluon and quark energy-momentum tensor operators: we compute to one loop the conversion factors relating the nonperturbative mixing matrix to the $\overline{\mathrm{MS}}$ scheme.

We determine the $\mathrm{\Delta }(1232)$ resonance parameters using lattice QCD and the Lüscher method. The resonance occurs in elastic pion-nucleon scattering with $J^P=3/2^{+}$ in the isospin $I=3/2$, $P$-wave channel. Our calculation is performed with $N_f=2+1$ flavors of clover fermions on a lattice with $L\approx 2.8\mathrm{fm}$. The pion and nucleon masses are $m_{\pi }=255.4(1.6)\mathrm{MeV}$ and $m_N=1073(5)\mathrm{MeV}$, respectively, and the strong decay channel $\mathrm{\Delta }\to \pi N$ is found to be above the threshold. To thoroughly map out the energy dependence of the nucleon-pion scattering amplitude, we compute the spectra in all relevant irreducible representations of the lattice symmetry groups for total momenta up to $\overrightarrow{P}=\frac{2\pi }{L}(1,1,1)$, including irreps that mix $S$ and $P$ waves. We perform global fits of the amplitude parameters to up to 21 energy levels, using a Breit-Wigner model for the $P$-wave phase shift and the effective-range expansion for the $S$-wave phase shift. From the location of the pole in the $P$-wave scattering amplitude, we obtain the resonance mass $m_{\mathrm{\Delta }}=1378(7)(9)\mathrm{MeV}$ and the coupling $g_{\mathrm{\Delta }-\pi N}=23.8(2.7)(0.9)$.

Holographic conformal field theories (CFTs) are usually studied in a limit where the gravity description is weakly coupled. By contrast, lattice quantum field theory can be used as a tool for doing computations in a wider class of holographic CFTs where nongravitational interactions in AdS become strong, and gravity is decoupled. We take preliminary steps for studying such theories on the lattice by constructing the discretized theory of a scalar field in ${\mathrm{AdS}}_2$ and investigating its approach to the continuum limit in the free and perturbative regimes. Our main focus is on finite sublattices of maximally symmetric tilings of hyperbolic space. Up to boundary effects, these tilings preserve the triangle group as a large discrete subgroup of ${\mathrm{AdS}}_2$, but have a minimum lattice spacing that is comparable to the radius of curvature of the underlying spacetime. We quantify the effects of the lattice spacing as well as the boundary effects, and find that they can be accurately modeled by modifications within the framework of the continuum limit description. We also show how to do refinements of the lattice that shrink the lattice spacing at the cost of breaking the triangle group symmetry of the maximally symmetric tilings.

We study the gluon parton densities [parton distribution functions (PDFs), transverse momentum distributions (TMDs), generalized parton distributions (GPDs)] and form factors in soft-wall AdS/QCD. We show that the power behavior of gluon parton distributions and form factors at large values of the light-cone variable and large values of square momentum is consistent with quark counting rules. We also show that the transverse momentum distributions derived in our approach obey the model-independent Mulders-Rodrigues inequalities without referring to specific model parameters. All gluon parton distributions are defined in terms of the unpolarized and polarized gluon PDFs and profile functions. The latter are related to gluon PDFs via differential equations.

We study symmetries and dynamics of chiral $SU(N)$ gauge theories with matter Weyl fermions in a two-index symmetric ($\psi$) or antisymmetric tensor ($\chi$) representation, together with $N\pm 4+p$ fermions in the antifundamental ($\eta$) and $p$ fermions in the fundamental ($\xi$) representations. They are known as the Bars-Yankielowicz (the former) and the generalized Georgi-Glashow models (the latter). The conventional ’t Hooft anomaly matching algorithm is known to allow a confining, chirally symmetric vacuum in all these models, with a simple set of massless baryonlike composite fermions describing the infrared physics. We analyzed recently one of these models ($\psi \eta$ model), by applying the ideas of generalized symmetries and the consequent, stronger constraints involving certain mixed anomalies, finding that the confining, chirally symmetric, vacuum is actually inconsistent. In the present paper, this result is extended to a wider class of the Bars-Yankielowicz and the generalized Georgi-Glashow models. It is shown that for all these models with $N$ and $p$ both even, at least, the generalized anomaly matching requirement forbids the persistence of the full chiral symmetries in the infrared if the system confines. The most natural and consistent possibility is that some bifermion condensates form, breaking the color gauge symmetry dynamically, together with part of the global symmetry.

We discuss the influence of a helicity imbalance on the phase diagram of dense QCD at finite temperature. The helical quark number counts the difference between the axial charges carried by quarks and antiquarks. We argue that the helical chemical potential is a thermodynamically relevant quantity in theories with the mass gap generation. Using the linear sigma model coupled to quarks, we show that the presence of the helical density substantially affects the phase diagram of dense quark matter. A moderate helical density makes the chiral phase transition softer while shifting the critical end point towards lower temperatures and higher baryon chemical potentials. As the helical density increases, the segment of the first-order transition disappears, and the chiral transition becomes a soft crossover. At even higher helical chemical potentials, the first-order transition reappears again at the zero-density finite-temperature transition and extends into the interior of the phase diagram. This evolution of the chiral transition reflects the existence of a thermodynamic duality between helical and vector (baryonic) chemical potentials. We also show that the presence of the helicity imbalance of quark matter increases the curvature of the chiral pseudocritical line in QCD.

We present a new Monte Carlo event generator for the production of a top-quark pair in association with a $W^{\pm }$ boson at hadron colliders in the POWHEG-BOX framework. We consider the next-to-leading-order QCD corrections to the $pp\to t\overline{t}{W}^{\pm }$ cross section, corresponding to the $\mathcal{O}({\alpha }_s^3\alpha )$ and $\mathcal{O}({\alpha }_s{\alpha }^3)$ terms in the perturbative expansion of the parton-level cross section, and model the decays of $W$ and top quarks at leading order retaining spin correlations. The fixed-order QCD calculation is further interfaced with the pythia8 parton-shower event generator via the POWHEG method as implemented in the POWHEG-BOX. The corresponding code is now part of the public repository of the POWHEG-BOX. We perform a comparison of different event generators for both the case of inclusive production and the case of the two same-sign leptons signature at the Large Hadron Collider operating at a center-of-mass energy of 13 TeV. We investigate theoretical uncertainties in the modeling of the fiducial volume stemming from missing higher-order corrections, the different parton-shower-matching schemes, and the modeling of decays. We find that the subleading contribution at $\mathcal{O}({\alpha }_s{\alpha }^3)$ is particularly sensitive to differences in the matching scheme and higher-order parton-shower effects. We observe that in particular jet observables can differ quite visibly although these differences play only a subordinate role in the description of physical observables once all contributions are combined.

We present a comprehensive study of the quark sector of $2+1$ flavor QCD, based on a self-consistent treatment of the coupled system of Schwinger-Dyson equations for the quark propagator and the full quark-gluon vertex in the one-loop dressed approximation. The individual form factors of the quark-gluon vertex are expressed in a special tensor basis obtained from a set of gauge-invariant operators. The sole external ingredient used as input to our equations is the Landau gauge gluon propagator with $2+1$ dynamical quark flavors, obtained from studies with Schwinger-Dyson equations, the functional renormalization group approach, and large volume lattice simulations. The appropriate renormalization procedure required in order to self-consistently accommodate external inputs stemming from other functional approaches or the lattice is discussed in detail, and the value of the gauge coupling is accurately determined at two vastly separated renormalization group scales. Our analysis establishes a clear hierarchy among the vertex form factors. We identify only three dominant ones, in agreement with previous results. The components of the quark propagator obtained from our approach are in excellent agreement with the results from Schwinger-Dyson equations, the functional renormalization group, and lattice QCD simulation, a simple benchmark observable being the chiral condensate in the chiral limit, which is computed as $(245\mathrm{MeV}{)}^3$. The present approach has a wide range of applications, including the self-consistent computation of bound-state properties and finite temperature and density physics, which are briefly discussed.

We present the multiple particle identification (MPID) network, a convolutional neural network for multiple object classification, developed by MicroBooNE. MPID provides the probabilities that an interaction includes an $e^{-}$, $\gamma$, ${\mu }^{-}$, ${\pi }^{\pm }$, and protons in a liquid argon time projection chamber single readout plane. The network extends the single particle identification network previously developed by MicroBooNE [Convolutional neural networks applied to neutrino events in a liquid argon time projection chamber, R. Acciarri et al. J. Instrum. 12, P03011 (2017)]. MPID takes as input an image either cropped around a reconstructed interaction vertex or containing only activity connected to a reconstructed vertex, therefore relieving the tool from inefficiencies in vertex finding and particle clustering. The network serves as an important component in MicroBooNE’s deep-learning-based ${\nu }_e$ search analysis. In this paper, we present the network’s design, training, and performance on simulation and data from the MicroBooNE detector.

Building upon recent work, we present an improved effective-one-body (EOB) model for spin-aligned, coalescing, black hole binaries with generic orbital configurations, i.e., quasicircular, eccentric, or hyperbolic orbits. The model, called TEOBResumSGeneral, relies on the idea of incorporating general Newtonian prefactors, instead of the usual quasicircular ones, in both radiation reaction and waveform. The major advance with respect to previous work is that the quasicircular limit of the model is now correctly informed by numerical relativity (NR) quasicircular simulation. This provides EOB/NR unfaithfulness for the dominant quadrupolar waveform, calculated with Advanced LIGO noise, at most of the order of 1% over a meaningful portion of the quasicircular NR simulations computed by the Simulating eXtreme Spacetime (SXS) collaboration. In the presence of eccentricity, the model is similarly NR-faithful, $\lesssim 1\%$, all over the 28 public SXS NR datasets, with initial eccentricity up to $\simeq 0.2$, mass ratio up to $q=3$ and dimensionless spin magnitudes as large as $+0.7$. Higher multipoles, up to $\ell =5$ are also reliably modeled through the eccentric inspiral, plunge, merger and ringdown. For hyperbolic-like configurations, we also show that the EOB computed scattering angle is in excellent agreement with all currently available NR results.

A black hole is superentropic if it violates the reverse isoperimetric inequality. Recently, some studies have indicated that some four-dimensional superentropic black holes have the null hypersurface caustics (NHC) outside their event horizons. In this paper, we extend to explore whether or not the NHC exists in the cases of high-dimensional superentropic black holes. We consider the singly rotating Kerr–anti–de Sitter superentropic black holes in arbitrary dimensions and the singly rotating charged superentropic black hole in five-dimensional minimal gauged supergravity and find that the NHC exists outside the event horizons for these superentropic black holes. Furthermore, the spacetime dimensions and other parameters of the black hole, such as the electric charge, have an important impact on the NHC inside the horizon. Our results indicate that, when the superentropic black hole has the Cauchy horizon, the NHC will also exist inside the Cauchy horizon.

The influence of the medium on the gravitational deflection of light rays is widely discussed in literature for the simplest nontrivial case: cold nonmagnetized plasma. In this article, we generalize these studies to the case of an arbitrary transparent dispersive medium with a given refractive index. We calculate the deflection angle of light ray moving in a general spherically symmetric metric in the presence of medium with the spherically symmetric refractive index. The equation for the radius of circular light orbits is also derived. We discuss in detail the properties of these results and various special cases. In particular, we show that multiplying the refractive index by a constant does not affect the deflection angle and radius of circular orbits. At the same time, the presence of dispersion makes the trajectories different from the case of a vacuum even in a spatially homogeneous medium. As one of the applications of our results, we calculate the correction to the angle of vacuum gravitational deflection for the case when a massive object is surrounded by homogeneous but dispersive medium. As another application, we present the calculation of the shadow of a black hole surrounded by medium with arbitrary refractive index. Our results can serve as a basis for studies of various plasma models beyond the cold plasma case.

The evolution of cosmic perturbations in a two-component ultralight axionic universe is investigated. We present the first spectral computation of perturbations in multicomponent universes. A particular case composed of light extreme axions and free massive particles offers a possibility for the formation of very high-redshift massive galaxies, which are typically required to host massive early quasars. Our computation retains the information of perturbed velocities for individual axion components, opening a new avenue for setting up initial conditions for future axion dark matter simulations.

The computational technique of $N$-fold Mellin-Barnes (MB) integrals, presented in a companion paper by the same authors, is used to derive sets of series representations of the massive one-loop conformal three-point Feynman integral in various configurations. This shows the great simplicity and efficiency of the method in nonresonant cases (generic propagator powers) as well as some of its subtleties in the resonant ones (for unit propagator powers). We confirm certain results in the physics and mathematics literature and provide many new results, some of them dealing with the more general massive one-loop conformal $n$-point case. In particular, we prove two recent conjectures that give the massive one-loop conformal $n$-point integral (for generic propagator powers) in terms of multiple hypergeometric series. We show how these conjectures, that were deduced from a Yangian bootstrap analysis, are related by a tower of new quadratic transformations in hypergeometric functions theory. Finally, we also use our MB method to identify spurious contributions that can arise in the Yangian approach.

We present the results of a lattice QCD calculation of the scalar and vector form factors for the unphysical $B_s\to {\eta }_s$ decay, over the full physical range of $q^2$. This is a useful testing ground both for lattice QCD and for our wider understanding of the behavior of form factors. Calculations were performed using the highly improved staggered quark (HISQ) action on $N_f=2+1+1$ gluon ensembles generated by the MILC Collaboration with an improved gluon action and HISQ sea quarks. We use three lattice spacings and a range of heavy quark masses from that of charm to bottom, all in the HISQ formalism. This permits an extrapolation in the heavy quark mass and lattice spacing to the physical point and nonperturbative renormalization of the vector matrix element on the lattice. We find results in good agreement with previous work using nonrelativistic QCD $b$ quarks and with reduced errors at low $q^2$, supporting the effectiveness of our heavy HISQ technique as a method for calculating form factors involving heavy quarks. A comparison with results for other decays related by SU(3) flavor symmetry shows that the impact of changing the light daughter quark is substantial but changing the spectator quark has very little effect. We also map out form factor shape parameters as a function of heavy quark mass and compare to heavy quark effective theory expectations for mass scaling at low and high recoil. This work represents an important step in the progression from previous work on heavy-to-heavy decays ($b\to c$) to the numerically more challenging heavy-to-light decays.

The interplay between the small-$x$ limit of QCD amplitudes and QCD factorization at moderate $x$ has been studied extensively in recent years. It was finally shown that semiclassical formulations of small-$x$ physics can have the form of an infinite twist framework involving transverse momentum dependent distributions in the eikonal limit. In this work, we demonstrate that small-$x$ distributions can be formulated in terms of transverse gauge links. This allows, in particular, for direct and efficient decompositions of observables into subamplitudes involving gauge-invariant suboperators which span parton distributions.

We study the mass spectra of the $N\mathrm{\Omega }$ dibaryons in the ${}^3{S}_1$ and ${}^5{S}_2$ channels with $J^P=1^{+}$ and $2^{+}$, respectively, by using the method of QCD sum rules. We construct two dibaryon interpolating currents in the molecular picture and calculate their correlation functions and spectral densities up to dimension-16 condensates. Our results indicate that there may exist an $N\mathrm{\Omega }$ dibaryon bound state in the ${}^5{S}_2$ channel with a binding energy of about 21 MeV. The masses of the ${}^3{S}_1$ $N\mathrm{\Omega }$ dibaryons with $J^P=1^{+}$ are predicted to be higher than the $N\mathrm{\Omega }$ and $\mathrm{\Lambda }\mathrm{\Xi }$ thresholds and thus, can decay into these final states directly in S wave. The $N\mathrm{\Omega }({}^5{S}_2)$ dibaryon bound state can decay into the octet-octet final states $\mathrm{\Lambda }\mathrm{\Xi }$ and $\mathrm{\Sigma }\mathrm{\Xi }$ in D wave via the quark rearrangement mechanism. The existence of these $N\mathrm{\Omega }$ dibaryons may be identified in the relativistic heavy-ion collision experiments in the future.

We briefly review and expand our recent analysis for all three invariant $A$, $B$, $D$ gravitational form factors of the nucleon in holographic QCD. They compare well to the gluonic gravitational form factors recently measured using lattice QCD simulations. The holographic $A$-term is fixed by the tensor $T=2^{++}$ (graviton) Regge trajectory, and the $D$-term by the difference between the tensor $T=2^{++}$ (graviton) and scalar $S=0^{++}$ (dilaton) Regge trajectories. The $B$-term is null in the absence of a tensor coupling to a Dirac fermion in bulk. A first measurement of the tensor form factor $A$-term is already accessible using the current GlueX data, and therefore the tensor gluonic mass radius, pressure, and shear inside the proton, thanks to holography. The holographic $A$-term and $D$-term can be expressed exactly in terms of harmonic numbers. The tensor mass radius from the holographic threshold is found to be $⟨r_{GT}^2⟩\approx (0.57–0.60\mathrm{fm}{)}^2$, in agreement with $⟨r_{GT}^2⟩\approx (0.62\mathrm{fm}{)}^2$ as extracted from the overall numerical lattice data, and empirical GlueX data. The scalar mass radius is found to be slightly larger $⟨r_{GS}^2⟩\approx (0.7\mathrm{fm}{)}^2$.