Motivated by the large cross section of the $e^{+}{e}^{-}\to \eta J/\psi$ process measured by the BESIII and Belle Collaborations recently, we evaluate this process at $\mathcal{O}({\alpha }_s^4)$ accuracy in the framework of nonrelativistic QCD. We find that the cross section at the center-of-mass energy $\sqrt{s}=4.009\mathrm{GeV}$ is 34.6 pb, which is consistent with the BESIII data. The comparison with the Belle data in the region from 4.0 to 5.3 GeV is also presented. Concerning the $\eta$ and ${\eta }^{\prime }$ mixing and the potential gluonium component of ${\eta }^{\prime }$, we also estimate the rate of the $e^{+}{e}^{-}\to {\eta }^{\prime }J/\psi$ process, which can be checked within the updated Belle data.

The leptonic unitarity triangle (LUT) provides a geometric description of $CP$ violations in the lepton-neutrino sector and is directly measurable in principle. In this paper, we reveal that the angles in the LUT have definite physical meaning, and demonstrate the exact connection of the LUT to neutrino oscillations. For the first time, we prove that these leptonic angles act as phase shifts in neutrino oscillations, by shifting $\mathrm{\Delta }{m}^{2}L/2E$ to $\mathrm{\Delta }{m}^{2}L/2E+\alpha$, where $(L,E,\alpha )$ denote the baseline length, neutrino energy and corresponding angle of the LUT. Each LUT has three independent parameters and contains only partial information of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix. We demonstrate that the partial information in each LUT can describe the corresponding neutrino oscillation. Hence, for the first time, we uncover that any given kind of neutrino oscillations contains at most three (rather than four) independent degrees of freedom from the PMNS matrix, and this may provide a cleaner way for fitting the corresponding oscillation data.

We combine six measurements of the inclusive top-quark pair ($t\overline{t}$) production cross section (${\sigma }_{t\overline{t}}$) from data collected with the CDF and D0 detectors at the Fermilab Tevatron with proton-antiproton collisions at $\sqrt{s}=1.96\mathrm{TeV}$. The data correspond to integrated luminosities of up to $8.8{\mathrm{fb}}^{-1}$. We obtain a value of ${\sigma }_{t\overline{t}}=7.60\pm 0.41\mathrm{pb}$ for a top-quark mass of $m_t=172.5\mathrm{GeV}$. The contributions to the uncertainty are 0.20 pb from statistical sources, 0.29 pb from systematic sources, and 0.21 pb from the uncertainty on the integrated luminosity. The result is in good agreement with the standard model expectation of $7.35_{-0.33}^{+0.28}\mathrm{pb}$ at next-to-next-to-leading order and next-to-next-to leading logarithms in perturbative QCD.

It is shown that, under the separability assumption for the metric, the slow-rotation approximation for the Bocharova-Bronnikov-Melnikov-Bekenstein black hole in general relativity with a conformally coupled scalar field does not work outside the event horizon. Suggestions indicated by our present analysis towards a fully rotating black hole solution are discussed.

We explore Schwinger pair production in rotating time-dependent electric fields using the real-time Dirac-Heisenberg-Wigner formalism. We determine the time evolution of the Wigner function as well as asymptotic particle distributions neglecting backreactions on the electric field. Whereas qualitative features can be understood in terms of effective Keldysh parameters, the field rotation leaves characteristic imprints in the momentum distribution that can be interpreted in terms of interference and multiphoton effects. These phenomena may seed characteristic features of QED cascades created in the antinodes of a high-intensity standing wave laser field.

At linear order in cosmological perturbations, departures from the growth in the cosmological standard model can be quantified in terms of two functions of redshift $z$ and Fourier number $k$. Previous studies have performed principal component forecasts for several choices of these two functions based on expected capabilities of upcoming large structure surveys. It is typically found that there will be many well-constrained degrees of freedom. However, not all and probably most of these degrees of freedom were physical if the parametrization had allowed for an arbitrary $k$ dependence. In this paper, we restrict the $k$ dependence to that allowed in local theories of gravity under the quasistatic approximation, i.e. ratios of polynomials in $k$, and identify the best constrained features in the ($z,k$) dependence of the commonly considered functions $\mu$ and $\gamma$ as measured by a Large Synoptic Survey Telescope (LSST)-like weak lensing survey. We estimate the uncertainty in the measurements of the eigenmodes of modified growth. We find that imposing the theoretical prior on $k$ dependence reduces the number of degrees of freedom and the covariance between parameters. On the other hand, imaging surveys like LSST are not as sensitive to the $z$ dependence as they are to the $k$ dependence of the modified growth functions. This trade-off provides us with, more or less, the same number of well-constrained eigenmodes (with respect to our prior) as found before, but now these modes are physical.

We study the reduced phase space quantization of a closed Friedmann universe, where matter content is constituted by two (noninteracting) fluids, namely dust (or cold dark matter) and radiation. It is shown that, for this particular model, specific boundary conditions can be related to the algebra of Dirac observables.

We consider an alternative approach for the computation of the stochastic gravitational wave background generated by small loops produced throughout the cosmological evolution of cosmic string networks and use it to derive an analytical approximation to the corresponding power spectrum. We show that this approximation produces an excellent fit to more elaborate results obtained using the velocity-dependent one-scale model to describe cosmic string network dynamics, over a wide frequency range, in the small-loop regime.

We investigate the rich nonlinear dynamics during the end of hilltop inflation by numerically solving the coupled Klein-Gordon-Friedmann equations in an expanding universe. In particular, we search for coherent, nonperturbative configurations that may emerge due to the combination of nontrivial couplings between the fields and resonant effects from the cosmological expansion. We couple a massless field to the inflaton to investigate its effect on the existence and stability of coherent configurations and the effective equation of state at reheating. For parameters consistent with data from the Planck and WMAP satellites, and for a wide range of couplings between the inflaton and the massless field, we identify a transition from disorder to order characterized by emergent oscillonlike configurations. We verify that these configurations can contribute a maximum of roughly 30% of the energy density in the universe. At late times their contribution to the energy density drops to about 3%, but they remain long lived on cosmological time scales, being stable throughout our simulations. Cosmological oscillon emergence is described using a new measure of order in field theory known as relative configurational entropy.

In the framework of the two-flavor extended linear sigma model with mixing between scalar quarkonium and tetraquark, we investigate the role of the tetraquark in the chiral phase transition. We explore various scenarios depending on the value of various parameters in our model. The physical mass spectrum of mesons put a tight constraint on the parameter set of our model. We find that a sufficiently strong cubic self interaction of the tetraquark field can drive the chiral phase transition to the first order even at zero quark chemical potential. Weak or absence of the cubic self-interaction term of the tetraquark field make the chiral phase transition crossover at the vanishing density.

We study the pion condensation at the finite isospin chemical potential using a holographic QCD model. By solving the equations of motion for the pion fields together with those for the isosinglet scalar and iso-triplet vector meson fields, we show that the phase transition from the normal phase to the pion condensation phase is second order with the mean-field exponent, and that the critical value of the isospin chemical potential ${\mu }_I$ is equal to the pion mass, consistently with the result obtained by the chiral effective Lagrangian at $\mathrm{O}(p^2)$. For a higher chemical potential, we find a deviation, which can be understood as a higher order effect in the chiral effective Lagrangian. We investigate the ${\mu }_I$ dependence of the chiral condensate defined by $\tilde{\sigma }\equiv \sqrt{⟨\sigma {⟩}^2+⟨{\pi }^a{⟩}^2}$. We find that $\tilde{\sigma }$ is almost constant in the small ${\mu }_I$ region, while it grows with ${\mu }_I$ in the large ${\mu }_I$ region. This implies that the strength of the chiral symmetry breaking is not changed for small ${\mu }_I$: The isospin chemical potential plays a role to rotate the “vacuum angle” of the chiral circle ${\tan }^{-1}\sqrt{⟨{\pi }^a{⟩}^2/⟨\sigma {⟩}^2}$ with keeping the “radius” $\tilde{\sigma }$ unchanged for small ${\mu }_I$. For the large ${\mu }_I$ region, on the other hand, the chiral symmetry breaking is enhanced by the existence of ${\mu }_I$.

In confining lattice gauge theories in which part of the flavor group is coupled weakly to additional gauge fields, both the dynamics of the weak gauge fields as well as lattice artifacts may have nontrivial effects on the orientation of the vacuum in flavor space. Here we discuss this issue for lattice gauge theories employing staggered fermions. Staggered fermions break flavor symmetries to a much smaller group on the lattice, and orientations in flavor space that are equivalent in the continuum may be distinct on the lattice. Assuming universality, we show that in the continuum limit the weakly gauged flavor symmetries are always vectorlike, disproving a recent claim in the literature.

We apply the eigenvectors from a variational analysis to successfully extract the three-quark color-singlet wave functions of even-parity excited states of the nucleon. We explore the first four states in the spectrum excited by the standard nucleon interpolating field. We find that the states exhibit a structure qualitatively consistent with a constituent quark model, where the ground, first, second, and third excited states have 0, 1, 2, and 3 nodes in the radial wave function of the $d$ quark about two $u$ quarks at the origin. Moreover, the radial amplitude of the probability distribution is similar to that predicted by constituent quark models. We present a detailed examination of the quark-mass dependence of the probability distributions for these states, searching for a nontrivial role for the multiparticle components mixed in the finite-volume QCD eigenstates. Finally we examine the dependence of the $d$-quark probability distribution on the positions of the two $u$ quarks. The results are fascinating, with the underlying $S$-wave orbitals governing the distributions even at rather large $u$-quark separations.

Israel-Stewart theory is a causal, stable formulation of relativistic dissipative fluid dynamics. This theory has been shown to give a decent description of the dynamical behavior of a relativistic fluid in cases where shear stress becomes important. In principle, it should also be applicable to situations where heat flow becomes important. However, it has been shown that there are cases where Israel-Stewart theory cannot reproduce phenomena associated with heat flow. In this paper, we derive a relativistic dissipative fluid-dynamical theory from kinetic theory which provides a good description of all dissipative phenomena, including heat flow. We explicitly demonstrate this by comparing this theory with numerical solutions of the relativistic Boltzmann equation.

The next-to-leading order QCD corrections for ${\chi }_{bJ}$, the $p$-wave bottomonium, to $J/\psi$ pair decay processes are evaluated utilizing NRQCD factorization formalism. The scale dependence of the ${\chi }_{b2}\to J/\psi J/\psi$ process is depressed with NLO corrections, and hence the uncertainties in the leading-order results are greatly reduced. The total branch ratios are found to be the order of ${10}^{-5}$ for all three ${\chi }_{bJ}\to J/\psi J/\psi$ processes, indicating that they are observable in the LHC and SuperB experiments.

We describe a method of analytic evolution of distribution amplitudes (DAs) that have singularities, such as nonzero values at the end points of the support region, jumps at some points inside the support region and cusps. We illustrate the method by applying it to the evolution of a flat (constant) DA and antisymmetric flat DA, and then use the method for evolution of the two-photon generalized distribution amplitude. Our approach has advantages over the standard method of expansion in Gegenbauer polynomials, which requires an infinite number of terms in order to accurately reproduce functions in the vicinity of singular points, and over a straightforward iteration of an initial distribution with evolution kernel. The latter produces logarithmically divergent terms at each iteration, while in our method the logarithmic singularities are summed from the start, which immediately produces a continuous curve, with only one or two iterations needed afterwards in order to get rather precise results.

We solve the BFKL equation in the leading logarithmic approximation numerically in the Yang-Mills theory with the Higgs mechanism for the vector boson mass generation. It can be considered as a model for the amplitude with the correct behavior of the $s$-channel partial waves at large impact parameters. The Pomeron spectrum of the massive BFKL kernel in the $\omega$ space for $t=0$ coincides with the continuous spectrum for the massless case although the density of its eigenvalues is 2 times smaller for $\omega >{\omega }_0$, where ${\omega }_0$ is a negative number. We find a simple parametrization for the corresponding eigenfunctions. Because the leading singularity in the $\omega$ plane in this Higgs model for $t=0$ is a fixed cut, the Regge pole contributions could be only for nonphysical positive $t$. Hence we can state that the correct behavior at large $b$ does not influence the main properties of the BFKL equation.

We present total and differential cross sections for the production of a hard photon with up to two $b$ jets at both the Tevatron with center-of-mass energy 1.96 TeV and the Large Hadron Collider with center-of-mass energy 8 TeV, including next-to-leading order (NLO) QCD corrections and full $b$-quark mass effects. We study the theoretical uncertainty due to the residual renormalization- and factorization-scale dependence and explain its origin on the basis of the different subprocesses contributing to the NLO cross section. We specifically address the case of the production of a hard photon with at least one $b$ jet and compare the NLO QCD predictions in both the four- and five-flavor-number schemes to the experimental measurements obtained by CDF and D0.

The measurement of the Higgs pair production via vector boson fusion can be used to test the trilinear Higgs self-coupling and the $VVHH$ $(V=Z,W)$ quartic gauge interactions. In this paper we present the calculations of the next-to-next-to-leading-order QCD corrections to the SM Higgs boson pair production via vector boson fusion at hadron colliders with the center-of-mass energy of 14, 33, and 100 TeV by using the structure function approach and study the residual uncertainties from the factorization/renormalization scale, parton distribution functions, and ${\alpha }_s$ on the total cross section. We also provide the distributions of transverse momenta, rapidities, invariant mass, and azimuthal angle separations of final Higgs bosons. We observe a considerable quantitative reduction in the scale uncertainty due to the next-to-next-to-leading-order QCD corrections and find that the total cross section is sensitive to the trilinear Higgs self-coupling.

Recent LHCb results on the decay $B\to K^{*}{\mu }^{+}{\mu }^{-}$ show significant deviations from the standard model estimates in some of the angular correlations. In this paper we study the possibility of explaining these deviations using new scalar interactions. We show that new dimension-6 four-quark operators of scalar and pseudoscalar type can successfully account for the discrepancy even after being consistent with other experimental measurements. We also briefly discuss possible extensions of the standard model where these operators can be generated.