We present the first study of the cusp effect (the movement of resonant poles due to the proximity of multiparticle thresholds) caused by the creation of diquark-antidiquark pairs. The cusp profile for such states is obtained from constituent counting rules. We compare the effectiveness of diquark cusps in moving resonant poles with that from a phenomenological form commonly used for meson-pair creation and find that mesons tend to be more effective at lower energies (e.g., the $K\overline{K}$ threshold), while diquarks tend to be more effective at the charm [$X(3872)$] scales and above.

We explore predictive flavor models based on subgroups of the standard-model $SU(3{)}^5$ flavor symmetry. Restricting ourselves to products of $SU(3)$, we find that a global $SU(3{)}^3$ flavor symmetry, broken only by two Yukawa spurions, leads to a relation among down-type quark, up-type quark, and charged-lepton Yukawa matrices: $Y_d\propto Y_u{Y}_e^{†}$. As a result, the charged-lepton mass ratios are expressed in terms of quark mass ratios and mixing angles. Large leptonic mixing angles appear to be natural and lead to contributions to flavor-changing neutral currents in the charged-lepton sector, which can be tested in future precision experiments.

In this work we study the potential of the processes $e^{+}{e}^{-}\to e^{+}{\gamma }^{*}{e}^{-}\to e^{+}\tau {\overline{\nu }}_{\tau }{\nu }_e$ and $e^{+}{e}^{-}\to e^{+}{\gamma }^{*}{\gamma }^{*}{e}^{-}\to e^{+}{\nu }_{\tau }{\overline{\nu }}_{\tau }{e}^{-}$ at a future high-energy and high-luminosity linear electron positron collider, such as the International Linear Collider and Compact Linear Collider, to study the sensibility on the anomalous magnetic and electric dipole moments of the tau neutrino. For an integrated luminosity of $590{\mathrm{fb}}^{-1}$ and center-of-mass energy of 3 TeV, we derive 95% C.L. limits on the dipole moments: ${\mu }_{{\nu }_{\tau }}\le 1.44\times 10^{-6}{\mu }_B$ and $d_{{\nu }_{\tau }}\le 2.78\times 10^{-17}ecm$ in the ${\gamma }^{*}{e}^{-}$ collision mode and of ${\mu }_{{\nu }_{\tau }}\le 3.4\times 10^{-7}{\mu }_B$ and $d_{{\nu }_{\tau }}\le 6.56\times 10^{-18}ecm$ with the ${\gamma }^{*}{\gamma }^{*}$ collision mode, improving the existing limits.

Using a sample of $1.06\times 10^8\psi (3686)$ events produced in $e^{+}{e}^{-}$ collisions at $\sqrt{s}=3.686\mathrm{GeV}$ and collected with the BESIII detector at the BEPCII collider, we present studies of the decays $\psi (3686)\to K^{-}\mathrm{\Lambda }{\overline{\mathrm{\Xi }}}^{+}+\mathrm{c}.\mathrm{c}.$ and $\psi (3686)\to \gamma K^{-}\mathrm{\Lambda }{\overline{\mathrm{\Xi }}}^{+}+\mathrm{c}.\mathrm{c}.$. We observe two hyperons, $\mathrm{\Xi }(1690{)}^{-}$ and $\mathrm{\Xi }(1820{)}^{-}$, in the $K^{-}\mathrm{\Lambda }$ invariant mass distribution in the decay $\psi (3686)\to K^{-}\mathrm{\Lambda }{\overline{\mathrm{\Xi }}}^{+}+\mathrm{c}.\mathrm{c}.$ with significances of $4.9\sigma$ and $6.2\sigma$, respectively. The branching fractions of $\psi (3686)\to K^{-}\mathrm{\Lambda }{\overline{\mathrm{\Xi }}}^{+}+\mathrm{c}.\mathrm{c}.$, $\psi (3686)\to K^{-}{\mathrm{\Sigma }}^0{\overline{\mathrm{\Xi }}}^{+}+\mathrm{c}.\mathrm{c}.$, $\psi (3686)\to \gamma {\chi }_{cJ}\to \gamma K^{-}\mathrm{\Lambda }{\overline{\mathrm{\Xi }}}^{+}+\mathrm{c}.\mathrm{c}.$ ($J=0$, 1, 2), and $\psi (3686)\to \mathrm{\Xi }(1690/1820{)}^{-}{\overline{\mathrm{\Xi }}}^{+}+\mathrm{c}.\mathrm{c}.$ with subsequent decay $\mathrm{\Xi }(1690/1820{)}^{-}\to K^{-}\mathrm{\Lambda }$ are measured for the first time.

A search for new physics in proton-proton collisions having final states with an electron or muon and missing transverse energy is presented. The analysis uses data collected in 2012 with the CMS detector, at an LHC center-of-mass energy of 8 TeV, and corresponding to an integrated luminosity of $19.7{\mathrm{fb}}^{-1}$. No significant deviation of the transverse mass distribution of the charged lepton-neutrino system from the standard model prediction is found. Mass exclusion limits of up to 3.28 TeV at 95% confidence level for a $W^{\prime }$-boson with the same couplings as that of the standard model $W$-boson are determined. Results are also derived in the framework of split universal extra dimensions, and exclusion limits on Kaluza–Klein $W_{\mathrm{KK}}^{(2)}$ states are found. The final state with large missing transverse energy also enables a search for dark matter production with a recoiling $W$-boson, with limits set on the mass and the production cross section of potential candidates. Finally, limits are established for a model including interference between a left-handed $W^{\prime }$-boson and the standard model $W$-boson and for a compositeness model.

In an attempt to find a quasilocal measure of quantum entanglement, we introduce the concept of entanglement density in relativistic quantum theories. This density is defined in terms of infinitesimal variations of the region whose entanglement we monitor and in certain cases can be mapped to the variations of the generating points of the associated domain of dependence. We argue that strong subadditivity constrains the entanglement density to be positive semidefinite. Examining this density in the holographic context, we map its positivity to a statement of integrated null energy condition in the gravity dual. We further speculate that this may be mapped to a statement analogous to the second law of black hole thermodynamics for the extremal surface.

The dynamics of a probe D7-brane in an asymptotically anti–de Sitter–Vaidya background has been investigated in the presence of an external magnetic field. Holographically, this is dual to the dynamical meson melting in the $\mathcal{N}=2$ super Yang-Mills theory. If the final temperature of the system is large enough, the probe D7-brane will dynamically cross the horizon (the black hole embedding). By turning on the external magnetic field and raising it sufficiently, the final embedding of the corresponding D7-brane changes to a Minkowski embedding. On the field theory side, this means that the mesons which melt due to the raise in the temperature will form bound states again by applying an external magnetic field. We also show that the evolution of the system to its final equilibrium state is postponed due to the presence of the magnetic field.

Long ago Coleman, Callan, Wess and Zumino (CCWZ) constructed the general effective Lagrangian for nonlinearly realized symmetry by finding all possible nonlinear representations of the broken group $G$ which become linear when restricted to the unbroken group $H$. However, in the case of a single Nambu-Goldstone boson (NGB), which corresponds to a broken $U(1)$, the effective Lagrangian can also be obtained by imposing a constant shift symmetry. In this work we generalize the shift symmetry approach to multiple NGBs and show that, when they furnish a linear representation of $H$ that can be embedded in a symmetric coset, it is possible to derive the CCWZ Lagrangian by imposing (1) “the Adler’s zero condition,” which requires scattering amplitudes to vanish when emitting a single soft NGB and (2) closure of shift symmetry with the linearly realized symmetry. Knowledge of the broken group $G$ is not required at all. Using only generators of $H$, the NGB covariant derivative and the associated gauge field can be computed to all orders in the NGB decay constant $f$.

A static self-gravitating electrically charged spherical thin shell embedded in a ($3+1$)-dimensional spacetime is used to study the thermodynamic and entropic properties of the corresponding spacetime. Inside the shell, the spacetime is flat, whereas outside it is a Reissner-Nordström spacetime, and this is enough to establish the energy density, the pressure, and the electric charge in the shell. Imposing that the shell is at a given local temperature and that the first law of thermodynamics holds on the shell one can find the integrability conditions for the temperature and for the thermodynamic electric potential, the thermodynamic equilibrium states, and the thermodynamic stability conditions. Through the integrability conditions and the first law of thermodynamics an expression for the shell’s entropy can be calculated. It is found that the shell’s entropy is generically a function of the shell’s gravitational and Cauchy radii alone. A plethora of sets of temperature and electric potential equations of state can be given. One set of equations of state is related to the Hawking temperature and a precisely given electric potential. Then, as one pushes the shell to its own gravitational radius and the temperature is set precisely equal to the Hawking temperature, so that there is a finite quantum backreaction that does not destroy the shell, one finds that the entropy of the shell equals the Bekenstein-Hawking entropy for a black hole. The other set of equations of state is such that the temperature is essentially a power law in the inverse Arnowitt-Deser-Misner (ADM) mass and the electric potential is a power law in the electric charge and in the inverse ADM mass. In this case, the equations of thermodynamic stability are analyzed, resulting in certain allowed regions for the parameters entering the problem. Other sets of equations of state can be proposed. Whatever the initial equation of state for the temperature, as the shell radius approaches its own gravitational radius, the quantum backreaction imposes the Hawking temperature for the shell in this limit. Thus, when the shell’s radius is sent to the shell’s own gravitational radius the formalism developed allows one to find the precise form of the Bekenstein-Hawking entropy of the correlated black hole.

The deformation of a nonrotating body resulting from the application of a tidal field is measured by two sets of Love numbers associated with the gravitoelectric and gravitomagnetic pieces of the tidal field, respectively. The gravitomagnetic Love numbers were previously computed for fluid bodies under the assumption that the fluid is in a strict hydrostatic equilibrium that requires the complete absence of internal motions. A more realistic configuration, however, is an irrotational state that establishes, in the course of time, internal motions driven by the gravitomagnetic interaction. We recompute the gravitomagnetic Love numbers for this irrotational state and show that they are dramatically different from those associated with the strict hydrostatic equilibrium: while the Love numbers are positive in the case of strict hydrostatic equilibrium, they are negative in the irrotational state. Our computations are carried out in the context of perturbation theory in full general relativity and in a post-Newtonian approximation that reproduces the behavior of the Love numbers when the body’s compactness is small.

Acoustic perturbations in an expanding hadronic fluid at temperatures below the chiral transition point represent massless pions propagating in curved spacetime geometry. In comoving coordinates the corresponding analog metric tensor describes a hyperbolic Friedmann-Robertson-Walker spacetime. We study the analog cosmological particle creation of pions below the critical point of the chiral phase transition. We compare the cosmological creation spectrum with the spectrum of analog Hawking radiation at the analog trapping horizon.

We consider cosmological modeling in $f(R)$ theories of gravity, using both top-down and bottom-up constructions. The top-down models are based on Robertson-Walker geometries, and the bottom-up constructions are built by patching together subhorizon-sized regions of perturbed Minkowski space. Our results suggest that these theories do not provide a theoretically attractive alternative to the standard general relativistic cosmology. We find that the only $f(R)$ theories that can admit an observationally viable weak-field limit have large-scale expansions that are observationally indistinguishable from the Friedmann solutions of general relativity with $\mathrm{\Lambda }$. Such theories do not alleviate any of the difficulties associated with $\mathrm{\Lambda }$, and cannot produce any new behavior in the cosmological expansion without simultaneously destroying the Newtonian approximation to gravity on small scales.

In this paper we operate under the assumption that no tensors from inflation will be measured in the future by the dedicated experiments and argue that, while for single-field slow-roll models of inflation the running of the spectral index will be hard to detect, in multifield models the running can be large due to its strong correlation with non-Gaussianity. A detection of both the running and non-Gaussianity might therefore strengthen the conclusion that more than one scalar degree of freedom was active during inflation.

The Hamiltonian formulation of mimetic gravity is formulated. Although there are two more equations than those of general relativity, these are proved to be the constraint equation and the conservation of the energy-momentum tensor. The Poisson brackets are then computed and closure is proved. At the end, the Wheeler-DeWitt equation was solved for a homogeneous and isotropic universe. This was done first for a vanishing potential where agreement with the dust case was shown, and then for a constant potential.

Motivated by the string landscape, the inflationary potential may be high dimensional and complicated. We propose a new way to construct some high-dimensional random potentials, and simulate inflationary dynamics on top of that, for up to 50 dimensions in field space. Especially, random bifurcations of classical inflationary trajectory are studied. It is shown that the bifurcation probability increases as a function of the number of dimensions. Those random bifurcations are not consistent with observations and dramatically limit the parameter space of inflation on a complicated landscape. For example, in 10 dimensions, only $10^{-3}–10^{-6}$ of the parameter space volume leads to unique classical trajectories. The rest is ruled out by random bifurcations.

We study $S$-wave resonance contributions to the $B_{(s)}^0\to J/\psi {\pi }^{+}{\pi }^{-}$ and $B_s\to {\pi }^{+}{\pi }^{-}{\mu }^{+}{\mu }^{-}$ decays in the perturbative QCD framework by introducing two-hadron distribution amplitudes for final states. The Breit–Wigner formula for the $f_0(500)$, $f_0(1500)$, and $f_0(1790)$ resonances and the Flatté model for the $f_0(980)$ resonance are adopted to parametrize the timelike scalar form factors in the two-pion distribution amplitudes, which include both resonant and nonresonant contributions. The resultant branching fraction and differential branching fraction in the pion-pair invariant mass for each resonance channel are consistent with experimental data. The determined $S$-wave two-pion distribution amplitudes, containing the information of both resonant and nonresonant rescattering phases, can be employed to predict direct $CP$ asymmetries of other three-body hadronic $B$ meson decays in various localized regions of two-pion phase space.

Stimulated by the recent BESIII observation of a new resonance in $e^{+}{e}^{-}\to \omega {\chi }_{c0}$ which is consistent with our predicted $\psi (4S)$, we estimate the meson loop contribution to $\psi (4S)\to \omega {\chi }_{c0}$ in this work. The evaluation indicates that our theoretical estimate can overlap with the experimental data in a reasonable parameter range. This fact shows that introduction of the missing higher charmonium $\psi (4S)$ provides a possible explanation to the recent BESIII observation. The upper limit of a branching ratio of $\psi (4S)\to \eta J/\psi$ is also predicted to be $1.9\times {10}^{-3}$, which can be further tested by BESIII, Belle, and forthcoming BelleII.

In very high energy scattering events, production of multiple Higgs and electroweak gauge bosons becomes possible. Indeed the perturbative cross section for these processes grows with increasing energy, eventually violating perturbative unitarity. In addition to perturbative unitarity we also examine constraints on high multiplicity processes arising from experimentally measured quantities. These include the shape of the $Z$-peak and upper limits on scattering cross sections of cosmic rays. We find that the rate of high multiplicity electroweak processes will exceed these upper limits at energies not significantly above what can be currently tested experimentally. This leaves two options: (1) The electroweak sector becomes truly nonperturbative in this regime or (2) additional physics beyond the standard model is needed. In both cases novel physics phenomena must set in before these energies are reached. Based on the measured Higgs mass we estimate the critical energy to be in the range of $10^3\mathrm{TeV}$ but we also point out that it can potentially be significantly less than that.

We prove the Adler-Bardeen theorem in a large class of general gauge theories, including nonrenormalizable ones. We assume that the gauge symmetries are general covariance, local Lorentz symmetry, and Abelian and non-Abelian Yang-Mills symmetries, and that the local functionals of vanishing ghost numbers satisfy a variant of the Kluberg-Stern–Zuber conjecture. We show that if the gauge anomalies are trivial at one loop, for every truncation of the theory there exists a subtraction scheme where they manifestly vanish to all orders, within the truncation. Outside the truncation the cancellation of gauge anomalies can be enforced by fine-tuning local counterterms. The framework of the proof is worked out by combining a recently formulated chiral dimensional regularization with a gauge invariant higher-derivative regularization. If the higher-derivative regularizing terms are placed well beyond the truncation, and the energy scale $\mathrm{\Lambda }$ associated with them is kept fixed, the theory is superrenormalizable and has the property that, once the gauge anomalies are canceled at one loop, they manifestly vanish from two loops onwards by simple power counting. When the $\mathrm{\Lambda }$ divergences are subtracted away and $\mathrm{\Lambda }$ is sent to infinity, the anomaly cancellation survives in a manifest form within the truncation and in a nonmanifest form outside. The standard model coupled to quantum gravity satisfies all the assumptions, so it is free of gauge anomalies to all orders.

We show, without using semiclassical approximations, that, in high-temperature QCD with chiral symmetry restoration and ${\mathrm{U}(1)}_{\mathrm{A}}$ symmetry breaking, the partition function for sufficiently light quarks can be expressed as an ensemble of noninteracting objects with topological charge that obey the Poisson statistics. We argue that the topological objects are “quasi-instantons” (rather than bare instantons) taking into account quantum effects. Our result is valid even close to the (pseudo)critical temperature of the chiral phase transition.