In the present work, we calculate $M1$ transitions, $0^{-+}\to 1^{--}\gamma$, and $E1$ transitions involving axial vector mesons such as $1^{+-}\to 0^{-+}\gamma$ and $0^{-+}\to 1^{+-}\gamma$ for which very little data is available as of now. We make use of the general structure of the transition amplitude $M_{\mathrm{fi}}$ expressed as a linear superposition of terms involving all possible combinations of $++$ and $--$ components of Salpeter wave functions of final and initial hadrons. In the present work, we make use of two leading Dirac structures in the hadronic Bethe-Salpeter wave functions of the involved hadrons, which makes the formulation more rigorous. We evaluate the decay widths for both the above mentioned $M1$ and $E1$ transitions. We have used algebraic forms of Salpeter wave functions obtained through analytic solutions of mass spectral equations for ground and excited states of $1^{--}$, $0^{-+}$, and $1^{+-}$ heavy-light quarkonia in an approximate harmonic oscillator basis to do analytic calculations of their decay widths. We have compared our results with experimental data, where ever available, and other models.

We calculate the leading corrections to jet momentum broadening and medium-induced branching that arise from the velocity of a moving medium at first order in opacity. These results advance our knowledge of jet quenching and demonstrate how it couples to the collective flow of the quark-gluon plasma in heavy-ion collisions. We also compute the leading corrections to jet momentum broadening due to transverse gradients of temperature and density. We find that the velocity effects lead to both anisotropic transverse momentum diffusion proportional to the medium velocity and anisotropic medium-induced radiation emitted preferentially in the direction of the flow. We isolate the relevant subeikonal corrections by working with jets composed of scalar particles with arbitrary color factors interacting with the medium by scalar QCD. Appropriate substitution of the color factors and light-front wave functions allow us to immediately apply the results to a range of processes including $q\to qg$ branching in real QCD. The resulting general expressions can be directly coupled to hydrodynamic simulations on an event-by-event basis to study the correlations between jet quenching and the dynamics of various forms of nuclear matter.

Transverse momentum dependent parton distribution functions, also abbreviated as TMDs, offer a three-dimensional picture of hadrons by taking the intrinsic transverse momentum of the parton into consideration. Hence, they are very important for us to understand the structure of hadrons. In this article, we calculate and summarize all TMDs of quark through the spectator model, from twist-2 to twist-4. Especially, we give complete results of TMDs at twist-4. We adopt a general analytical framework to calculate TMDs, with both scalar and axial-vector spectators being considered. All TMDs are calculated analytically in the light-cone coordinate, and single gluon rescattering is considered to generate T-odd TMDs. T-even TMDs are also calculated to this level, maybe for the first time. Different from the traditional point of view, the twist-4 TMDs can contribute to some physical observables like azimuthal asymmetries. An approximate formula of the Sivers asymmetry, including twist-4 TMDs, is given.

The production of single top-quarks in the $t$-channel at hadron colliders imposes strong analytic constraints on parton distribution functions (PDFs) through its double deeply inelastic scattering (DDIS) form. We exploit this to provide novel consistency checks between LO, NLO and NNLO PDF fits and propose to include it as a constraint in future PDF fits. Furthermore, while it is well-known that the $b$-quark PDF is highly sensitive to the $b$-quark mass, we show that the treatment of this systematic uncertainty is still incomplete, fragmented or outright missing at the moment. Consequently, we conclude that the $b$-quark mass uncertainty is the dominant but so far broadly neglected theory uncertainty for this process.

By solving the Dyson-Schwinger equations and analyzing the obtained mass function, we compute the quark condensate beyond the chiral limit with a cutoff independent definition. The definition explicitly separates the quadratic and logarithmic divergence from the condensate, even for very large quark mass. With this well-defined condensate, we then analyze the evolution of the condensate and its susceptibility with the current quark mass. The susceptibility shows a critical mass at about ${\mathrm{\Lambda }}_{\mathrm{QCD}}$, which defines a transition boundary for internal hadron dynamics.

We calculate the pole masses of pseudoscalar mesons in a strongly magnetized medium within the framework of the SU(3) Nambu–Jona-Lasinio model, using a magnetic field-independent regularization scheme. We employ both a constant and a magnetic field-dependent coupling $G(B)$, the latter being fitted to reproduce lattice QCD results for the pseudocritical chiral transition temperature. Numerical results for the pole masses are obtained for definite parametrizations of the model. For neutral mesons, the use of $G(B)$ provides closer agreement with lattice QCD results, which reveal a decrease of the mass with the external field. On the contrary, charged mesons masses are enhanced by $B$, showing no sign of the nonmonotonous behavior found in recent lattice QCD simulations.

The effects of the ${\mathrm{\Sigma }}_c{\overline{D}}^{*}-{\mathrm{\Lambda }}_c(2595)\overline{D}$ coupled-channel dynamics and various one-boson-exchange (OBE) forces for the LHCb pentaquark states, $P_c(4440)$ and $P_c(4457)$, are reinvestigated. Both the pion and $\rho$-meson exchanges are considered for the ${\mathrm{\Sigma }}_c{\overline{D}}^{*}\text{−}{\mathrm{\Lambda }}_c(2595)\overline{D}$ coupled-channel dynamics. It is found that the role of the ${\mathrm{\Lambda }}_c(2595)\overline{D}$ channel in the descriptions of the $P_c(4440)$ and $P_c(4457)$ states is not significant with the OBE parameters constrained by other experimental sources. The naive OBE models with the short-distance $\delta (\overrightarrow{r})$ term of the one-pion exchange (OPE) keep failing to reproduce the $P_c(4440)$ and $P_c(4457)$ states simultaneously. The OPE potential with the full $\delta (\overrightarrow{r})$ term results in a too large mass splitting for the $J^P=1/2^{-}$ and $3/2^{-}{\mathrm{\Sigma }}_c{\overline{D}}^{*}$ bound states with total isospin $I=1/2$. The OBE model with only the OPE $\delta (\overrightarrow{r})$ term dropped may fit the splitting much better but somewhat underestimates the splitting. Since the $\delta (\overrightarrow{r})$ potential is from short-distance physics, which also contains contributions from the exchange of mesons heavier than those considered explicitly, we vary the strength of the $\delta (\overrightarrow{r})$ potential and find that the masses of the $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$ can be reproduced simultaneously with the $\delta (\overrightarrow{r})$ term in the OBE model reduced by about 80%. While two different spin assignments are possible to produce their masses, in the preferred description, the spin parities of the $P_c(4440)$ and $P_c(4457)$ are $3/2^{-}$ and $1/2^{-}$, respectively.

Within the framework of $k_t$ factorization, we compute the differential cross section for the production of $B$ and $D$ mesons, using a general-mass variable-flavor-number scheme. Our calculations include all relevant $2\to 2$ processes. We explain how to include the $2\to 1$ process in our calculations but argue this is not (numerically) relevant at moderate transverse momentum due to its cancellation with the subtraction term. We apply this formalism to $pp$ collisions and compare our results with ALICE and LHCb data at central and forward rapidity.

The response of the hot QCD medium in the presence of external time dependent electromagnetic fields has been studied within the relativistic Boltzmann transport theory. The impact of the time dependence of the electromagnetic fields and collisional aspects of the medium to the induced electric and Hall current densities has been explored. The nonequilibrium momentum distribution of degrees of freedom has been obtained in the presence of space-time varying electromagnetic fields. Further, the analysis has been extended to an anisotropic QCD medium while incorporating the in-medium interaction effects. It is observed that the electric charge transport is sensitive to the inhomogeneity of the fields and the momentum anisotropy of the QCD medium.

The cross sections of the process $e^{+}{e}^{-}\to K_S^0{K}_L^0$ are measured at fifteen center-of-mass energies $\sqrt{s}$ from 2.00 to 3.08 GeV with a total integrated luminosity of $582{\mathrm{pb}}^{-1}$ and using the BESIII detector at the Beijing Electron Positron Collider. The results are found to be consistent with those obtained by BABAR. A resonant structure around 2.2 GeV is observed, with a mass and width of $2273.7\pm 5.7\pm 19.3\mathrm{MeV}/c^2$ and $86\pm 44\pm 51\mathrm{MeV}$, respectively, where the first uncertainties are statistical and the second ones are systematic. The product of its radiative width (${\mathrm{\Gamma }}_{e^{+}{e}^{-}}$) with its branching fraction to $K_S^0{K}_L^0$ ($B{r}_{K_S^0{K}_L^0}$) is $0.9\pm 0.6\pm 0.7\mathrm{eV}$.

Using $(448.1\pm 2.9)\times {10}^6$ $\psi (3686)$ events collected with the BESIII detector and a single-baryon tagging technique, we present the first observation of the decays $\psi (3686)\to \mathrm{\Xi }(1530{)}^0\overline{\mathrm{\Xi }}(1530{)}^0$ and $\mathrm{\Xi }(1530{)}^0{\overline{\mathrm{\Xi }}}^0$. The branching fractions are measured to be $\mathcal{B}(\psi (3686)\to \mathrm{\Xi }(1530{)}^0\overline{\mathrm{\Xi }}(1530{)}^0)=(6.77\pm 0.14\pm 0.39)\times {10}^{-5}$ and $\mathcal{B}(\psi (3686)\to \mathrm{\Xi }(1530{)}^0{\overline{\mathrm{\Xi }}}^0)=(0.53\pm 0.04\pm 0.03)\times {10}^{-5}$. Here, the first and second uncertainties are statistical and systematic, respectively. In addition, the parameter associated with the angular distribution for the decay $\psi (3686)\to \mathrm{\Xi }(1530{)}^0\overline{\mathrm{\Xi }}(1530{)}^0$ is determined to be $\alpha =0.32\pm 0.19\pm 0.07$, in agreement with theoretical predictions within one standard deviation.

A dedicated Mott polarimeter was designed to study the final spin state in Møller scattering of transversely polarized electron beams in the relativistic energy range. The polarization transfer was measured for two incident-beam polarization orientations with respect to the Møller scattering plane, at 3 MeV incident-beam energy. The results are found to be in agreement with the predictions of relativistic quantum mechanics. Estimates for the measurement of quantum spin correlations in Møller scattering, based on a simultaneous determination of the spin projections for both electrons in the final state, are also presented.

The first observation of the ${\mathrm{\Omega }}_b^{-}\to {\mathrm{\Xi }}_c^{+}{K}^{-}{\pi }^{-}$ decay is reported using $p$ $p$ collision data at center of mass energies of 7, 8, and 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$. Four excited ${\mathrm{\Omega }}_c^0$ baryons are observed in the ${\mathrm{\Xi }}_c^{+}$ $K^{-}$ mass projection of the ${\mathrm{\Omega }}_b^{-}\to {\mathrm{\Xi }}_c^{+}{K}^{-}{\pi }^{-}$ decays with the significance of each exceeding five standard deviations. They coincide with the states previously observed in prompt $pp$ and $e^{+}{e}^{-}$ production. Relative production rates, masses, and natural widths of the states are measured, and a test of spin hypotheses is performed. Moreover, the branching ratio of ${\mathrm{\Omega }}_b^{-}\to {\mathrm{\Xi }}_c^{+}{K}^{-}{\pi }^{-}$ is measured relative to the ${\mathrm{\Omega }}_b^{-}\to {\mathrm{\Omega }}_c^0{\pi }^{-}$ decay mode and a precise measurement of the ${\mathrm{\Omega }}_b^{-}$ mass of $6044.3\pm 1.2\pm 1.1_{-0.22}^{+0.19}\mathrm{MeV}$ is obtained.

$\mathrm{FASER}\nu$ at the CERN Large Hadron Collider (LHC) is designed to directly detect collider neutrinos for the first time and study their cross sections at TeV energies, where no such measurements currently exist. In 2018, a pilot detector employing emulsion films was installed in the far-forward region of ATLAS, 480 m from the interaction point, and collected $12.2{\mathrm{fb}}^{-1}$ of proton-proton collision data at a center-of-mass energy of 13 TeV. We describe the analysis of this pilot run data and the observation of the first neutrino interaction candidates at the LHC. This milestone paves the way for high-energy neutrino measurements at current and future colliders.

The tidal Love numbers of a black hole vanish, and this is often taken to imply that the hole’s tidally induced multipole moments vanish also. An obstacle to establishing a link between these statements is that the multipole moments of individual bodies are not defined in general relativity, when the bodies are subjected to a mutual gravitational interaction. In a previous publication [Phys. Rev. D 103, 064023 (2021)] I promoted the view that individual multipole moments can be defined when the mutual interaction is sufficiently weak to be described by a post-Newtonian expansion. In this view, a compact body is perceived far away as a skeletonized post-Newtonian object with a multipole structure, and the multipole moments can then be related to the body’s Love numbers. I expand on this view, and demonstrate that all static, tidally induced, mass multipole moments of a nonrotating black hole vanish to all post-Newtonian orders. The proof rests on a perturbative solution to the Einstein-Maxwell equations that describes an electrically charged particle placed in the presence of a charged black hole. The gravitational attraction between particle and black hole is balanced by electrostatic repulsion, and the system is in an equilibrium state. The particle provides a tidal environment to the black hole, and the multipole moments vanish for this environment. I argue that the vanishing is robust, and applies to all slowly varying tidal environments. The black hole’s charge can be as small as desired (though not identically zero); by continuity, the multipole moments of an electrically neutral black hole will continue to vanish.

Quantum backflow, discovered quite a few years back, is a generic purely quantum phenomenon, in which the probability of finding a particle in a direction is nonzero (and increasing for a certain period of time) even when the particle has with certainty a velocity in the opposite direction. In this paper, we study quantum backflow of a quantum particle across the event horizon of a Schwarzschild black hole. In a toy model approach, we consider a superposition of two ingoing solutions and observe the probability density and probability current. We explicitly demonstrate a nonvanishing quantum back flow in a small region around the event horizon. This is in contrast to the classical black hole picture, that once an excitation crosses the horizon, it is lost forever from the outside world. Deeper implications of this phenomenon are speculated. We also study quantum backflow for another spacetime with horizon, the Rindler spacetime, where the phenomenon can be studied only within the Rindler wedge.

In this paper we discuss models satisfying the limiting curvature condition. For this purpose, we modify the Einstein-Hilbert action by adding a term which restricts the growth of curvature. We analyze cosmological solutions in such models. Namely, we consider a closed contracting homogeneous isotropic universe filled with thermal radiation. We demonstrate that for properly chosen curvature constraints such a universe has a bounce. As a result, its evolution is nonsingular and contains a “de Sitter–type” supercritical stage connecting contracting and expanding phases. Possible generalizations of these results are briefly discussed.

We obtain two types of Yang-Mills-dilaton black hole solutions in both Lifshitz and hyperscaling violation spacetimes. We must consider at least three Yang-Mills gauge fields that interact with a scalar field and either $SO(n)$ or $SO$ ($n-1$, 1) gauge symmetry groups, where $n+1$ denotes the dimension of the spacetime. They lead to the spherical and hyperbolic solutions. The obtained solutions in the hyperscaling violation spacetime fall into two categories for $z\ne n-3-\frac{n-5}{n-1}\theta$ and $z=n-3-\frac{n-5}{n-1}\theta$, where $\theta =0$ represents the Lifshitz spacetime. In order to have a real asymptotic behavior for the hyperscaling violated black hole solutions, we should consider a negative value for the hyperscaling violation parameter as $\theta <0$. We also evaluate the thermodynamic quantities of the mentioned black holes and probe their thermal stability in the grand canonical ensemble. For $z\ge 2$, the hyperscaling violated solutions are not thermally stable for $z\le n-3-\frac{n-5}{n-1}\theta$, while they are stable for large $r_{+}$ with $z>n-3-\frac{n-5}{n-1}\theta$. We also check out the critical behavior of the obtained black holes and obtain a Smarr relation for the solutions. The results also announce of a first-order small-large phase transition for both black holes in the case $T>T_C$.

Sign and magnitude of Ruppeiner’s curvature $R_N$ is an empirical indicator of the respective nature and strength of microstructures of a thermodynamic system. We investigate the properties of $R_N$ for black holes in massive gravity and show that the behavior of microstructures at the HP transition point is significantly altered by the graviton mass and horizon topology. In general, depending on the massive gravity parameters, $R_N$ at HP transition point can be positive (negative) or even zero indicating respectively the dominance of repulsive (attractive) or non-interacting behaviors. In particular, presence of a weak repulsive type interaction is inferred in the large black hole branch at small pressures, which is new and in contrast to the known behavior of only attractive interactions for this branch in massless gravity. Further, when the graviton mass takes a critical value, the HP transition happens at zero temperature, where $R_N$ turns out to be a universal constant, taking exactly the same value known for Schwarzchild black hole in AdS. Analysis of the geometry of general black holes in AdS close to the HP transition point via novel near horizon scaling limits, reveals the presence of fully decoupled Rindler spacetimes.

In light of the most recent cosmological observations, we provide new updated constraints on the slow roll inflation in different extended scenarios beyond the $\mathrm{\Lambda }\mathrm{CDM}$ cosmological model. Along with the usual six parameters, we simultaneously vary different combinations of additional parameters, including the running of the scalar spectral index ${\alpha }_s$, its running of running ${\beta }_s$, the tensor amplitude $r$ and the spatial curvature ${\mathrm{\Omega }}_k$. From the Planck 2018 data, we find no evidence for a scalar running or a running of running, while analyzing the Atacama Cosmology Telescope data combined with WMAP 9-years observations data we find a preference for nonzero ${\alpha }_s$ and ${\beta }_s$ at the level of $2.9\sigma$ and $2.7\sigma$, respectively. Anyway, this preference is reduced when the tensor amplitude can vary in the model or ${\beta }_s$ is fixed to zero. The upper bound on $r$ is only slightly affected by the additional parameters while the differences in the datasets can remarkably change the compatibility among the different inflationary models, sometimes leading to discordant conclusions.