We report the findings of our extensive study of the spectra of flavored mesons in lattice gauge theories with symplectic gauge group and fermion matter content treated in the quenched approximation. For the $Sp(4)$, $Sp(6)$, and $Sp(8)$ gauge groups, the (Dirac) fermions transform in either the fundamental, or the 2-index, antisymmetric or symmetric, representations. This study sets the stage for future precision calculations with dynamical fermions in the low-mass region of lattice parameter space. Our results have potential phenomenological applications ranging from composite Higgs models, to top (partial) compositeness, to dark matter models with composite, strong-coupling dynamical origin. Having adopted the Wilson flow as a scale-setting procedure, we apply Wilson chiral perturbation theory to extract the continuum and massless limits for the observables of interest. The resulting measurements are used to perform a simplified extrapolation to the large-$N$ limit, hence drawing a preliminary connection with gauge theories with unitary groups. We conclude with a brief discussion of the Weinberg sum rules.

We compute the complete set of Standard Model (SM) and tensor $B\to D^{*}\ell \overline{\nu }$ and $B_s\to D_s^{*}\ell \overline{\nu }$ semileptonic form factors across the full kinematic range of the decays using second generation MILC $n_f=2+1+1$ highly improved staggered quark (HISQ) gluon field configurations and HISQ valence quarks, with the heavy-HISQ method. Lattice spacings range from 0.09 to 0.044 fm with pion masses from $\approx 300\mathrm{MeV}$ down to the physical value and heavy quark masses ranging between $\approx 1.5m_c$ and $4.1m_c\approx 0.9m_b$; currents are normalized nonperturbatively. Using the recent untagged $B\to D^{*}\ell {\overline{\nu }}_{\ell }$ data from Belle and $B_s\to D_s^{*}\mu {\overline{\nu }}_{\mu }$ from LHCb together with our form factors, we determine a model independent value of $V_{cb}=39.03(56{)}_{\exp }(67{)}_{\mathrm{latt}}\times {10}^{-3}$, in agreement with previous exclusive determinations and in tension with the most recent inclusive result at the level of $3.6\sigma$. We also observe a $\approx 1\sigma$ tension between the shape of the differential decay rates computed using our form factors and those measured by Belle. We compute a purely theoretical Standard Model value for the ratio of semitauonic and semimuonic decay rates, $R(D^{*})=0.273(15)$, which we find to be closer to the recent Belle measurement and heavy flavor averaging group average than theory predictions using fits to experimental differential rate data for $B\to D^{*}\ell {\overline{\nu }}_{\ell }$. Determining $V_{cb}$ from our form factors and the experimental total rate for $B\to D^{*}\ell \nu$ also gives a value in agreement with inclusive results. We also compute the longitudinal polarization fraction for the semitauonic mode, $F_L^{D^{*}}=0.395(24)$, which is in tension at the level of $2.2\sigma$ with the recent Belle measurement. Our calculation combines $B\to D^{*}$ and $B_s\to D_s^{*}$ lattice results in a simultaneous chiral continuum extrapolation, maintaining correlations between both modes. We then give results for both $B\to D^{*}$ and $B_s\to D_s^{*}$, with the $B_s\to D_s^{*}$ results superseding our previous lattice computation. We also give the chiral perturbation theory needed to analyze the tensor form factors.

We present a novel construction of the QCD equation of state (EoS) at finite baryon density. Our work combines a recently proposed resummation scheme for lattice QCD results with the universal critical behavior at the QCD critical point. This allows us to obtain a family of equations of state in the range $0\le {\mu }_B\le 700\mathrm{MeV}$ and $25\mathrm{MeV}\le T\le 800\mathrm{MeV}$, which match lattice QCD results near ${\mu }_B=0$ while featuring a critical point in the 3D Ising model universality class. The position of the critical point can be chosen within the range accessible to beam-energy scan heavy-ion collision experiments. The strength of the singularity and the shape of the critical region are parametrized using a standard parameter set. We impose stability and causality constraints and discuss the available ranges of critical point parameter choices, finding that they extend beyond earlier parametric QCD EoS proposals. We present thermodynamic observables, including baryon density, pressure, entropy density, energy density, baryon susceptibility and speed of sound, that cover a wide range in the QCD phase diagram relevant for experimental exploration.

We studied the radiative transitions between the $\mathrm{\Upsilon }(10753)$, the $S\text{−}D$ mixed state of the $\mathrm{\Upsilon }(4S)$ and ${\mathrm{\Upsilon }}_1(3{}^3{D}_1)$, and the $X_b$, the heavy quark flavor symmetry counterpart of the $X(3782)$ in the bottomonium sector. The radiative transition was assumed to occur through the intermediate bottom mesons, including $P$-wave $B_1^{(\prime )}$ mesons as well as the $S$-wave $B^{(*)}$ ones. The consideration of the $B_1^{(\prime )}$ mesons leads to the couplings to be in $S$-wave, and hence enhances the contributions of the intermediate meson loops. The radiative decay width for the $\mathrm{\Upsilon }(10753)\to \gamma X_b$ is predicted to be order of 10 keV, corresponding to a branching fraction of ${10}^{-4}$. Based on the theoretical results, we strongly suggest to search for the $X_b$ in the $e^{+}{e}^{-}\to \gamma X_b$ with $X_b\to \pi \pi {\chi }_{b1}$ near $\sqrt{s}=10.754\mathrm{GeV}$, and it is hoped that the calculations here could be tested by the future Belle II experiments.

The Schwinger-Keldysh functional renormalization group developed by Y.-y. Tan et al. [Real-time dynamics of the $O(4)$ scalar theory within the fRG approach, SciPost Phys. 12, 026 (2022)] is employed to investigate critical dynamics related to a second-order phase transition. The effective action of model A is expanded to the order of $O({\partial }^2)$ in the derivative expansion for the $O(N)$ symmetry. By solving the fixed-point equations of effective potential and wave function, we obtain static and dynamic critical exponents for different values of the spatial dimension $d$ and the field component number $N$. It is found that one has $z\ge 2$ in the whole range of $2\le d\le 4$ for the case of $N=1$, while in the case of $N=4$, the dynamic critical exponent turns to $z<2$ when the dimension approach towards $d=2$.

We study the generalized gluon distribution that governs the dynamics of quarkonium inside a non-Abelian thermal plasma characterizing its dissociation and recombination rates. This gluon distribution can be written in terms of a correlation function of two chromoelectric fields connected by an adjoint Wilson line. We formulate and calculate this object in $\mathcal{N}=4$ supersymmetric Yang-Mills theory at strong coupling using the AdS/CFT correspondence, allowing for a nonzero center-of-mass velocity $v$ of the heavy quark pair relative to the medium. The effect of a moving medium on the dynamics of the heavy quark pair is described by the simple substitution $T\to \sqrt{\gamma }T$ in agreement with previous calculations of other observables at strong coupling, where $T$ is the temperature of the plasma in its rest frame, and $\gamma =(1-v^2{)}^{-1/2}$ is the Lorentz boost factor. Such a velocity dependence can be important when the quarkonium momentum is larger than its mass. Contrary to general expectations for open quantum systems weakly coupled with large thermal environments, the contributions to the transition rates that are usually thought of as the leading ones in Markovian descriptions vanish in this strongly coupled plasma. This calls for new theoretical developments to assess the effects of strongly coupled non-Abelian plasmas on in-medium quarkonium dynamics. Finally, we compare our results with those from weakly coupled QCD, and find that the QCD result moves toward the $\mathcal{N}=4$ strongly coupled result as the coupling constant is increased within the regime of applicability of perturbation theory. This behavior makes it even more pressing to develop a non-Markovian description of quarkonium in-medium dynamics.

We investigate the photon emission in pion-pion and pion-proton scattering in the soft-photon limit where the photon energy $\omega \to 0$. The expansions of the ${\pi }^{-}{\pi }^0\to {\pi }^{-}{\pi }^0\gamma$ and the ${\pi }^{\pm }p\to {\pi }^{\pm }p\gamma$ amplitudes, satisfying the energy-momentum relations, to the orders ${\omega }^{-1}$ and ${\omega }^0$ are derived. We show that these terms can be expressed completely in terms of the on-shell amplitudes for ${\pi }^{-}{\pi }^0\to {\pi }^{-}{\pi }^0$ and ${\pi }^{\pm }p\to {\pi }^{\pm }p$, respectively, and their partial derivatives with respect to $s$ and $t$. The structure term which is nonsingular for $\omega \to 0$ is determined to the order ${\omega }^0$ from the gauge-invariance constraint using the generalized Ward identities for pions and the proton. For the reaction ${\pi }^{-}{\pi }^0\to {\pi }^{-}{\pi }^0\gamma$ we discuss in detail the soft-photon theorems in the versions of both Low and Weinberg. We show that these two versions are different and must not be confounded. Weinberg’s version gives the pole term of a Laurent expansion in $\omega$ of the amplitude for ${\pi }^{-}{\pi }^0\to {\pi }^{-}{\pi }^0\gamma$ around the phase-space point of zero radiation. Low’s version gives an approximate expression for the above amplitude at a fixed phase-space point, corresponding to nonzero radiation. Clearly, the leading and next-to-leading terms in theses two approaches must be, and are indeed, different. We show their relation. We also discuss the expansions of differential cross sections for ${\pi }^{-}{\pi }^0\to {\pi }^{-}{\pi }^0\gamma$ with respect to $\omega$ for $\omega \to 0$.

Using data samples with an integrated luminosity of $22.42{\mathrm{fb}}^{-1}$ collected by the BESIII detector operating at the BEPCII storage ring, we measure the cross sections of the $e^{+}{e}^{-}\to \eta J/\psi$ process at center-of-mass energies from 3.808 to 4.951 GeV. Three structures are observed in the line shape of the measured cross sections. A maximum-likelihood fit with $\psi (4040)$, two additional resonances, and a nonresonant component are performed. The mass and width of the first additional state are $(4219.7\pm 2.5\pm 4.5)\mathrm{MeV}/c^2$ and $(80.7\pm 4.4\pm 1.4)\mathrm{MeV}$, respectively, consistent with the $\psi (4230)$. For the second state, the mass and width are $(4386\pm 13\pm 17)\mathrm{MeV}/c^2$ and $(177\pm 32\pm 13)\mathrm{MeV}$, respectively, consistent with the $\psi (4360)$. The first uncertainties are statistical, and the second ones are systematic. The statistical significance of $\psi (4040)$ is $8.0\sigma$ and those for $\psi (4230)$ and $\psi (4360)$ are more than $10.0\sigma$.

The momentum distribution of particle production in heavy-ion collisions encodes information about thermalization processes in the early-stage quark-gluon plasma. We use kinetic theory to study the far-from-equilibrium evolution of an expanding plasma with an anisotropic momentum-space distribution. We identify slow and fast degrees of freedom in the far-from-equilibrium plasma from the evolution of moments of this distribution. At late times, the slow modes correspond to hydrodynamic degrees of freedom and are naturally gapped from the fast modes by the inverse of the relaxation time, ${\tau }_R^{-1}$. At early times, however, there are an infinite number of slow modes with a gap inversely proportional to time, ${\tau }^{-1}$. From the evolution of the slow modes we generalize the paradigm of the far-from-equilibrium attractor to vector and tensor components of the energy-momentum tensor, and even to higher moments of the distribution function that are not part of the hydrodynamic evolution. We predict that initial-state momentum anisotropy decays slowly in the far-from-equilibrium phase and may persist until the relaxation time.

Evidence for the singly Cabibbo suppressed decay ${\mathrm{\Lambda }}_c^{+}\to p{\pi }^0$ is reported for the first time with a statistical significance of $3.7\sigma$ based on $6.0{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected at center-of-mass energies between 4.600 and 4.843 GeV with the BESIII detector at the BEPCII collider. The absolute branching fraction of ${\mathrm{\Lambda }}_c^{+}\to p{\pi }^0$ is measured to be $(1.56_{-0.58}^{+0.72}\pm 0.20)\times {10}^{-4}$. Combining with the branching fraction of ${\mathrm{\Lambda }}_c^{+}\to n{\pi }^{+}$, $(6.6\pm 1.3)\times {10}^{-4}$, the ratio of the branching fractions of ${\mathrm{\Lambda }}_c^{+}\to n{\pi }^{+}$ and ${\mathrm{\Lambda }}_c^{+}\to p{\pi }^0$ is calculated to be ${3.2}_{-1.2}^{+2.2}$. As an important input for the theoretical models describing the decay mechanisms of charmed baryons, our result indicates that the nonfactorizable contributions play an essential role and their interference with the factorizable contributions should not be significant. In addition, the absolute branching fraction of ${\mathrm{\Lambda }}_c^{+}\to p\eta$ is measured to be $(1.63\pm 0.31_{\mathrm{stat}}\pm 0.11_{\mathrm{syst}})\times {10}^{-3}$.

The amplification of radiation by superradiance is a universal phenomenon observed in numerous physical systems. We demonstrate that superradiant scattering generates entanglement for different input states, including coherent states, thereby establishing the inherently quantum nature of this phenomenon. To put these concepts to the test, we propose a novel approach to create horizonless ergoregions, which are nonetheless dynamically stable thanks to the dissipative dynamics of a polaritonic fluid of light. We numerically simulate the system to demonstrate the creation of a stable ergoregion. Subsequently, we investigate rotational superradiance within this system, with a primary focus on entanglement generation and the possibilities for its enhancement using current techniques. Our methods permit the investigation of quantum emission by rotational superradiance in state-of-the-art experiments, in which the input state can be controlled at will.

We develop the first causal and stable theory of a bulk-viscous relativistic pseudoplastic (or dilatant) fluid. This new formalism brings to light the rheological properties of several relativistic physical systems. Neutron star collisions can behave as a relativistic pseudoplastic material with viscous properties dictated by the nonconservation of lepton currents due to weak decay. Two-temperature relativistic plasmas, such as those surrounding supermassive galactic black holes, are predominantly pseudoplastic. Our framework can also be employed to construct novel viscous models for the evolution of the Universe with pseudoplastic or dilatant features.

To prevent the unauthorized spread of radioactive materials, it is essential to detect and monitor spent nuclear fuel. This paper investigates the feasibility of using a detector based on transition edge superconductors to monitor spent Canada deuterium uranium fuel in two distinct scenarios. The first of these considered the monitoring of a CANSTOR container at the location of the Gentilly-2 nuclear power plant. The fuel in a CANSTOR container is contained within baskets, which are then stored in tubes in the container. An individual detector with a mass of 1 kg is not sensitive to the removal of a single basket from the container without an unfeasibly long monitoring time. When an entire tube in the container is emptied (equivalent to approximately 5% of the fuel in the container), the results are improved. The second scenario examined the feasibility of monitoring a single dry storage container (DSC) at the Pickering site. The DSCs are much smaller than a CANSTOR container and contain approximately 7.4 tonnes of spent fuel. The background due to the neutrinos from the nearby reactors at the Pickering site was also evaluated. It was found that monitoring DSC was unfeasible due to the high reactor neutrino background. Both studies utilized fuel that was 30 years old; monitoring a container loaded with spent fuel that is younger would require a shorter monitoring time due to the fuel’s higher radioactivity.

Two particles can exert forces on each other when embedded in a sea of weakly coupled particles. These “wake forces” occur whenever the source and target particles have quadratic interactions with the mediating particles; they are proportional to the ambient energy density and typically have a range of order the characteristic de Broglie wavelength of the background. The effect can be understood as source particles causing a disturbance in the background waves—a wake—which subsequently interacts with the target particles. Wake forces can be mediated by bosons or fermions, can have spin dependence, may be attractive or repulsive, and have a generally anisotropic spatial profile and range that depends on the phase-space distribution of the ambient particles. In this work, I investigate the application of wake forces to dark matter searches, recast existing limits on short-range forces into leading constraints on dark matter with quadratic couplings, and sketch out potential experimental modifications to optimize sensitivity. Wake forces occur in the Standard Model: the presence of the cosmic neutrino background induces a millimeter-range force about 22 orders of magnitude weaker than gravity. Wake forces may also be relevant in condensed-matter and atomic physics.

We study the features of low energy strong interactions for a system at zero temperature and finite baryon and isospin chemical potentials, in the framework of a Nambu–Jona-Lasinio-like model that includes nonlocal four-point interactions. We analyze the phase transitions corresponding to chiral symmetry restoration and pion condensation, comparing our results with those obtained from local NJL-like models and lattice QCD calculations.

We examine properties of accelerated protons potentially responsible for the neutrino excess observed in the direction of NGC 1068, using constraints from kinetic particle-in-cell simulations. We find that (i) coronal x rays and optical/ultraviolet light in the inner disk lead to efficient absorption of hadronic $\gamma$ rays within 100 Schwarzschild radii from the black hole; (ii) protons accelerated from the coronal thermal pool cannot account for the observed neutrinos; and (iii) explaining the observed signal requires an injection of protons with a hard spectrum, peaking at ${\gamma }_p\sim {10}^3–{10}^4$, into the turbulent magnetically dominated corona, where they are confined and reaccelerated. The resulting neutrino signal can be consistent with IceCube observations. In our most favorable scenario, the injected protons are preaccelerated in intermittent current sheets in the vicinity of the black hole, occurring either at the boundary between the disk and the outflow or during magnetic flux eruption events.

We present a lattice QCD calculation of the transverse-momentum-dependent wave function (TMDWF) of the pion using large-momentum effective theory. Numerical simulations are based on one ensemble with $2+1+1$ flavors of highly improved staggered quarks with lattice spacing $a=0.121\mathrm{fm}$ from the MILC collaboration, and one with $2+1$ flavor clover fermions and tree-level Symanzik gauge action generated by the CLS collaboration with $a=0.098\mathrm{fm}$. As a key ingredient, the soft function is first obtained by incorporating the one-loop perturbative contributions and a proper normalization. Based on this and the equal-time quasi-TMDWF simulated on the lattice, we extract the TMDWF. The results for both lattice ensembles are compatible and a comparison with a phenomenological parametrization is made. Our studies provide a first attempt of ab initio calculation of TMDWFs which will eventually lead to crucial theory inputs for making predictions for exclusive processes under QCD factorization.

A novel classically integrable model is proposed. It is a deformation of the two-dimensional principal chiral model, embedded into a heterotic $\sigma$ model by a particular heterotic gauge field. This is inspired by the bosonic part of the heterotic $\sigma$ model and its recent Hamiltonian formulation in terms of $\mathrm{O}(d,d+n)$-generalized geometry in Hatsuda et al. [Gauged double field theory, current algebras and heterotic sigma models, J. High Energy Phys. 05 (2023) 220]. Classical integrability is shown by the construction of a Lax pair and a classical $\mathcal{R}$ matrix. The latter is almost of the canonical form with a twist function and solves the classical Yang-Baxter equation.

We consider vacuum transitions by bubble nucleation among 4D vacua with different values and signs of the cosmological constant $\mathrm{\Lambda }$, including both up and down tunnelings. Following the Hamiltonian formalism, we explicitly compute the transition probabilities for all possible combinations of initial and final values of $\mathrm{\Lambda }$ and find that up tunneling is allowed starting not only from dS spacetime but also from AdS and Minkowski spacetimes. We trace the difference with the Euclidean approach, where these transitions are found to be forbidden, to the difference of treating the latter spacetimes as pure (vacuum) states rather than mixed states with correspondingly vanishing or infinite entropy. We point out that these transitions are best understood as limits of the corresponding transitions with black holes in the zero mass limit $M\to 0$. We find that detailed balance is satisfied provided we use the Hartle-Hawking sign of the wave function for nucleating spacetimes. In the formal limit $\mathrm{\Lambda }\to -\infty$, the transition rates for anti–de Sitter (AdS) to dS agree with both the Hartle-Hawking and Vilenkin amplitudes for the creation of dS from nothing. This is consistent with a proposal of Brown and Dahlen to define “nothing” as AdS in this limit. For $M\ne 0$, the detailed balance is satisfied only in a range of mass values. We compute the bubble trajectory after nucleation and find that, contrary to the $M=0$ case, the trajectory does not correspond to the open universe slicing of dS. We briefly discuss the relevance of our results to the string landscape.