In this paper we present a comprehensive analysis of exclusive vector-meson photoproduction in $pp$, $p\mathrm{Pb}$ and PbPb collisions at Run 2 LHC energies using the color dipole formalism. The rapidity distributions and total cross sections for the $\rho$, $\varphi$, $J/\mathrm{\Psi }$, $\mathrm{\Psi }(2S)$ and $\mathrm{\Upsilon }$ production are estimated considering the more recent phenomenological models for the dipole-proton scattering amplitude, which are based on the color glass condensate formalism and are able to describe the inclusive and exclusive $ep$ HERA data. Moreover, we also discuss the impact of the modeling of the vector-meson wave functions on the predictions. The current theoretical uncertainty in the color dipole predictions is estimated and a comparison with the experimental results is performed.

We present a detailed mapping of the dominant kinematical domains contributing to the prompt atmospheric neutrino flux at high neutrino energies by studying their sensitivity to the cuts on several kinematical variables crucial for charm production in cosmic ray scattering in the atmosphere. This includes the maximal center-of-mass energy for proton-proton scattering, the longitudinal momentum fractions of partons in the projectile (cosmic ray) and target (nucleus of the atmosphere), the Feynman $x_F$ variable, and the transverse momentum of charm quark/antiquark. We find that the production of neutrinos with energies larger than $E_{\nu }>{10}^7\mathrm{GeV}$ is particularly sensitive to the c.m. energies larger than the ones at the LHC and to the longitudinal momentum fractions in the projectile ${10}^{-8}<x<{10}^{-5}$. Clearly, these are regions where we do not control the parton, in particular, gluon, densities. We also analyze the characteristic theoretical uncertainties in the charm production cross section coming from its QCD modeling. The precision data on the prompt atmospheric neutrino flux can efficiently constrain the mechanism of heavy quark production and underlying QCD dynamics in kinematical ranges beyond the reach of the current collider measurements.

We present the first calculation of the shear viscosity for two-flavor plane wave (FF) color superconducting quark matter. This is a member of the family of crystalline color superconducting phases of dense quark matter that may be present in the cores of neutron stars. The paired quarks in the FF phase feature gapless excitations on surfaces of crescent-shaped blocking regions in momentum space and participate in transport. We calculate their contribution to the shear viscosity. We also note that the transverse $t^1$, $t^2$, $t^3$ gluons which are undamped in the 2SC lead to dynamic screening in the FF phase. The exchange of these gluons is the most important mechanism of the scattering of the paired quarks. We find that the shear viscosity of the paired quarks is roughly a factor of 100 smaller compared to the shear viscosity of unpaired quark matter even though their spectrum is ungapped. Therefore in the two-flavor FF phase, the unpaired quarks and the electrons give the shear viscosity of the two-flavor FF phase to a very good approximation. Our results may have implications for the damping of $r$-modes in rapidly rotating, cold neutron stars.

We develop a framework for deriving Dyson-Schwinger equations (DSEs) and the Bethe-Salpeter equation (BSE) in QCD at the large $N_c$ limit. The starting point is a modified form (with auxiliary fields) of the QCD generating functional. This framework provides a natural order-by-order truncation scheme for DSEs and the BSE, and the kernels of the equations up to any order are explicitly given. Chiral symmetry (at the chiral limit) is preserved in any-order truncation, so it exemplifies the symmetry preserving truncation scheme. It provides a method to study DSEs and BSE beyond the rainbow-ladder truncation and is especially useful to study contributions from non-Abelian dynamics (those arising from gluon self-interactions). We also derive the equation for the quark-ghost scattering kernel and discuss the Slavnov-Taylor identity connecting the quark-gluon vertex, the quark propagator, and the quark-ghost scattering kernel.

By employing a framework for the quasi-two-body decays in the perturbative QCD (PQCD) factorization approach, we calculate the branching ratios of the decays $B_{(s)}\to D(\rho (1450)$, $\rho (1700))\to D\pi \pi$ with $D=(D_{(s)},{\overline{D}}_{(s)})$. The pion vector form factor $F_{\pi }$, acquired from a BABAR Collaboration analysis of $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}(\gamma )$ data, is involved in the two-pion distribution amplitudes ${\mathrm{\Phi }}_{\pi \pi }^{I=1}$. The PQCD predictions for the branching ratios of the considered quasi-two-body decays are in the range of ${10}^{-10}–{10}^{-4}$. The PQCD predictions for $\mathcal{B}(B^0\to {\overline{D}}^0({\rho }^0(1450),{\rho }^0(1700))\to {\overline{D}}^0{\pi }^{+}{\pi }^{-})$ agree well with the measured values as reported by LHCb if one takes still large theoretical errors into account. Unlike the traditional way of the PQCD approach, one can extract the decay rates for the two-body decays $B_{(s)}\to D(\rho (1450),\rho (1700))$ from the results of the corresponding quasi-two-body decays. The PQCD predictions for $\mathcal{B}(B_{(s)}\to D\rho (1450))$ and $\mathcal{B}(B_{(s)}\to D\rho (770))$ are similar in magnitude: an interesting relation to be tested by future experimental measurements.

Based on $448.1\times {10}^6\psi (3686)$ events collected with the BESIII detector, the decays $\psi (3686)\to \gamma {\chi }_{cJ},{\chi }_{cJ}\to \gamma \gamma (J=0,1,2)$ are studied. The decay branching fractions of ${\chi }_{c0,2}\to \gamma \gamma$ are measured to be $\mathcal{B}({\chi }_{c0}\to \gamma \gamma )=(1.93\pm 0.08\pm 0.05\pm 0.05)\times {10}^{-4}$ and $\mathcal{B}({\chi }_{c2}\to \gamma \gamma )=(3.10\pm 0.09\pm 0.07\pm 0.11)\times {10}^{-4}$, which correspond to two-photon decay widths of ${\mathrm{\Gamma }}_{\gamma \gamma }({\chi }_{c0})=2.03\pm 0.08\pm 0.06\pm 0.13\mathrm{keV}$ and ${\mathrm{\Gamma }}_{\gamma \gamma }({\chi }_{c2})=0.60\pm 0.02\pm 0.01\pm 0.04\mathrm{keV}$ with a ratio of $\mathcal{R}={\mathrm{\Gamma }}_{\gamma \gamma }({\chi }_{c2})/{\mathrm{\Gamma }}_{\gamma \gamma }({\chi }_{c0})=0.295\pm 0.014\pm 0.007\pm 0.027$, where the uncertainties are statistical, systematic and associated with the uncertainties of $\mathcal{B}(\psi (3686)\to \gamma {\chi }_{c0,2})$ and the total widths $\mathrm{\Gamma }({\chi }_{c0,2})$, respectively. For the forbidden decay of ${\chi }_{c1}\to \gamma \gamma$, no signal is observed, and an upper limit on the two-photon width is obtained to be ${\mathrm{\Gamma }}_{\gamma \gamma }({\chi }_{c1})<5.3\mathrm{eV}$ at the 90% confidence level. The ratio of the two-photon widths between helicity-zero and helicity-two components in the decay ${\chi }_{c2}\to \gamma \gamma$ is also measured to be $f_{0/2}={\mathrm{\Gamma }}_{\gamma \gamma }^{\lambda =0}({\chi }_{c2})/{\mathrm{\Gamma }}_{\gamma \gamma }^{\lambda =2}({\chi }_{c2})=(0.0\pm 0.6\pm 1.2)\times {10}^{-2}$, where the uncertainties are statistical and systematic, respectively.

We report branching fraction measurements of the decays $B^{+}\to \eta {\ell }^{+}{\nu }_{\ell }$ and $B^{+}\to {\eta }^{\prime }{\ell }^{+}{\nu }_{\ell }$ based on $711{\mathrm{fb}}^{-1}$ of data collected near the $\mathrm{\Upsilon }(4S)$ resonance with the Belle experiment at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. This data sample contains 772 million $B\overline{B}$ events. One of the two $B$ mesons is fully reconstructed in a hadronic decay mode. Among the remaining (“signal-$B$”) daughters, we search for the $\eta$ meson in two decay channels, $\eta \to \gamma \gamma$ and $\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0$, and reconstruct the ${\eta }^{\prime }$ meson in ${\eta }^{\prime }\to \eta {\pi }^{+}{\pi }^{-}$ with subsequent decay of the $\eta$ into $\gamma \gamma$. Combining the two $\eta$ modes and using an extended maximum likelihood, the $B^{+}\to \eta {\ell }^{+}{\nu }_{\ell }$ branching fraction is measured to be $(4.2\pm 1.1(\mathrm{stat}.)\pm 0.3(\mathrm{syst}.))\times {10}^{-5}$. For $B^{+}\to {\eta }^{\prime }{\ell }^{+}{\nu }_{\ell }$, we observe no significant signal and set an upper limit of $0.72\times {10}^{-4}$ at 90% confidence level.

In a holographic probe-brane model exhibiting a spontaneously spatially modulated ground state, we introduce explicit sources of symmetry breaking in the form of ionic and antiferromagnetic lattices. For the first time in a holographic model, we demonstrate pinning, in which the translational Goldstone mode is lifted by the introduction of explicit sources of translational symmetry breaking. The numerically computed optical conductivity fits very well to a Drude-Lorentz model with a small residual metallicity, precisely matching analytic formulas for the DC conductivity. We also find an instability of the striped phase in the presence of a large-amplitude ionic lattice.

We study the scattering of scalar waves propagating on the global monopole background. Since the scalar wave operator in this topological defect is not essentially self-adjoint, its solutions are not uniquely determined until a boundary condition at the origin is specified. As we show, this boundary condition manifests itself in the differential cross section and can be inferred by measuring the amplitude of the backscattered wave. We further demonstrate that whether or not the spacetime is stable under scalar perturbations also depends on the chosen boundary condition. In particular, we identify a class of such boundary conditions that significantly affects the differential cross section without introducing an instability.

We present a mode-sum regularization prescription for computing the vacuum polarization of a scalar field in static spherically symmetric black hole spacetimes in even dimensions. This is the first general and systematic approach to regularized vacuum polarization in higher even dimensions, building upon a previous scheme we developed for odd dimensions. Things are more complicated here since the even-dimensional propagator possesses logarithmic singularities which must be regularized. However, in spite of this complication, the regularization parameters can be computed in closed form in arbitrary even dimensions and for arbitrary metric function $f(r)$. As an explicit example of our method, we show plots for vacuum polarization of a massless scalar field in the Schwarzschild-Tangherlini spacetime for even $d=4,\dots ,10$. However, the method presented applies straightforwardly to massive fields or to nonvacuum spacetimes.

We consider an asymptotically free, vectorial, $\mathcal{N}=1$ supersymmetric gauge theory with gauge group $G$ and $N_f$ pairs of chiral superfields in the respective representations $\mathcal{R}$ and $\overline{\mathcal{R}}$ of $G$, having an infrared fixed point (IRFP) of the renormalization group at ${\alpha }_{\mathrm{IR}}$. We present exact results for the anomalous dimensions of various (gauge-invariant) composite chiral superfields ${\gamma }_{{\mathrm{\Phi }}_{\mathrm{prod}}}$ at the IRFP and prove that these increase monotonically with decreasing $N_f$ in the non-Abelian Coulomb phase of the theory and that scheme-independent expansions for these anomalous dimensions as powers of an $N_f$-dependent variable, ${\mathrm{\Delta }}_f$, exhibit monotonic and rapid convergence to the exact ${\gamma }_{{\mathrm{\Phi }}_{\mathrm{prod}}}$ throughout this phase. We also present a scheme-independent calculation of the derivative of the beta function, $d\beta /d\alpha {|}_{\alpha ={\alpha }_{\mathrm{IR}}}$, denoted ${\beta }_{\mathrm{IR}}^{\prime }$, up to $O({\mathrm{\Delta }}_f^3)$ for general $G$ and $\mathcal{R}$, and, for the case $G=\mathrm{SU}(N_c)$, $\mathcal{R}=F$, we give an analysis of the properties of ${\beta }_{\mathrm{IR}}^{\prime }$ calculated to $O({\mathrm{\Delta }}_f^4)$.

We construct walls of mass-deformed Kähler nonlinear sigma models on $SO(2N)/U(N)$, by using the moduli matrix formalism and the simple roots of $SO(2N)$. Penetrable walls are observed in the nonlinear sigma models on $SO(2N)/U(N)$ with $N>3$.

Gravitational-wave astronomy can give us access to the structure of black holes, potentially probing microscopic or even Planckian corrections at the horizon scale, as those predicted by some quantum-gravity models of exotic compact objects. A generic feature of these models is the replacement of the horizon by a reflective surface. Objects with these properties are prone to the so-called ergoregion instability when they spin sufficiently fast. We investigate in detail a simple model consisting of scalar perturbations of a Kerr geometry with a reflective surface near the horizon. The instability depends on the spin, on the compactness, and on the reflectivity at the surface. The instability time scale increases only logarithmically in the black-hole limit and, for a perfectly reflecting object, this is not enough to prevent the instability from occurring on dynamical time scales. However, we find that an absorption rate at the surface as small as 0.4% (reflectivity coefficient as large as $|\mathcal{R}{|}^2=0.996$) is sufficient to quench the instability completely. Our results suggest that exotic compact objects are not necessarily ruled out by the ergoregion instability.

We do a start-to-finish calculation of the stochastic gravitational wave background to be expected from cosmic strings. We start from a population of string loops taken from simulations, smooth these by Lorentzian convolution as a model of gravitational backreaction, calculate the average spectrum of gravitational waves emitted by the string population at any given time, and propagate it through a standard model cosmology to find the stochastic background today. Except for modeling back reaction as smoothing, we take into account all known effects, including changes in the number of cosmological relativistic degrees of freedom at early times and the possibility that some energy is in rare bursts that we might never have observed.

The Fokker action of point-particle binaries at the fourth post-Newtonian (4PN) approximation of general relativity has been determined previously. However two ambiguity parameters associated with infrared (IR) divergencies of spatial integrals had to be introduced. These two parameters were fixed by comparison with gravitational self-force (GSF) calculations of the conserved energy and periastron advance for circular orbits in the test-mass limit. In the present paper together with a companion paper, we determine both these ambiguities from first principle, by means of dimensional regularization. Our computation is thus entirely defined within the dimensional regularization scheme, for treating at once the IR and ultra-violet (UV) divergencies. In particular, we obtain crucial contributions coming from the Einstein-Hilbert part of the action and from the nonlocal tail term in arbitrary dimensions, which resolve the ambiguities.

The window function for protohalos in Lagrangian space is often assumed to be a top hat in real space. We measure this profile directly and find that it is more extended than a top hat but less extended than a Gaussian; its shape is well described by rounding the edges of the top hat by convolution with a Gaussian that has a scale length about 5 times smaller. This effective window $W_{\mathrm{eff}}$ is particularly simple in Fourier space, and has an analytic form in real space. Together with the excursion set bias parameters, $W_{\mathrm{eff}}$ describes the scale-dependence of the Lagrangian halo-matter cross correlation up to $k{R}_{\text{Lag}}\sim 10$, where $R_{\text{Lag}}$ is the Lagrangian size of the protohalo. Moreover, with this $W_{\mathrm{eff}}$, all the spectral moments of the power spectrum are finite, allowing a straightforward estimate of the excursion set peak mass function. This estimate requires a prescription of the critical overdensity enclosed within a protohalo if it is to collapse, which we calibrate from simulations. We find that the resulting estimate of halo abundances is only accurate to about 20%, and we discuss why: a top hat in “infall time” towards the protohalo center need not correspond to a top hat in the initial spatial distribution, so models in which infall rather than smoothed overdensity is the relevant variable may be more accurate.

The inflationary dynamics and preheating in a model with a nonminimally coupled inflaton field in the metric and Palatini formalisms are studied in this paper. We find that in both formalisms, irrespective of the initial conditions, our Universe will evolve into a slow-roll inflationary era and then the scalar field rolls into an oscillating phase. The value of the scalar field at the end of the inflation in the Palatini formalism is always larger than that in the metric one, which becomes more and more obvious with the increase of the absolute value of the coupling parameter $|\xi |$. During the preheating, we find that the inflaton quanta are produced explosively due to the parameter resonance and the growth of inflaton quanta will be terminated by the backreaction. With the increase of $|\xi |$, the resonance bands gradually close to the zero momentum ($k=0$), and the structure of resonance changes and becomes broader and broader in the metric formalism, while it remains to be narrow in the Palatini formalism. The energy transfer from the inflaton field to the fluctuation becomes more and more efficient with the increase of $|\xi |$, and in the metric formalism the growth of the efficiency of energy transfer is much faster than that in the Palatini formalism. Therefore, the inflation and preheating show different characteristics in different formalisms.

Recently, it has been realized that the so-called $G$-inflation model inspired by supplementing a generalized covariant Galileon-like nonlinear derivative self-interacting term to the standard kinetic term should be ruled out from inflationary models. This is due to the fact that it suffers from lack of an oscillatory phase at the end of the inflationary regime which is typically accompanied by the appearance of a negative squared propagation speed of the scalar mode leading to instabilities of small-scale perturbations. In this regard, the warm $G$-inflation scenario is proposed where for $G$ inflation to survive, the Galileon scalar field is coupled to the radiation field through a dissipation term which results in removing the reheating period due to the characteristics of warm inflationary scenario. In so doing, a linear stability analysis is first performed to obtain the appropriate slow-roll conditions in such a proposal. Cosmological perturbations of the model are then investigated by utilizing a fluctuation-dissipation theorem and analytical expressions are derived for observable quantities; the power spectrum, tilt spectral index, and tensor-to-scalar ratio in terms of $PSR$ parameters and Galileon flow functions. Finally, the model is solved for chaotic self-interacting potentials, particularly the renormalizable Higgs potential $\frac{\lambda }{4}{\varphi }^4$, and shown to be consistent with observations in the weak dissipation $Q\ll 1+3\frac{{\delta }_{GX}}{{\delta }_X}$ and $G$-dominant $3\frac{{\delta }_{GX}}{{\delta }_X}\gg 1$ regime despite its large self-coupling, since the energy scale at the horizon crossing is depressed by the synergy of Galileon and thermal effects.

The WIMPzilla hypothesis is that the dark matter is a super-weakly-interacting and superheavy particle. Conventionally, the WIMPzilla abundance is set by gravitational particle production during or at the end of inflation. In this study we allow the WIMPzilla to interact directly with Standard Model fields through the Higgs portal, and we calculate the thermal production (freeze-in) of WIMPzilla dark matter from the annihilation of Higgs boson pairs in the plasma. The two particle-physics model parameters are the WIMPzilla mass and the Higgs-WIMPzilla coupling. The two cosmological parameters are the reheating temperature and the expansion rate of the universe at the end of inflation. We delineate the regions of parameter space where either gravitational or thermal production is dominant, and within those regions we identify the parameters that predict the observed dark matter relic abundance. Allowing for thermal production opens up the parameter space, even for Planck-suppressed Higgs-WIMPzilla interactions.

In warm dark matter scenarios structure formation is suppressed on small scales with respect to the cold dark matter case, reducing the number of low-mass halos and the fraction of ionized gas at high redshifts and thus, delaying reionization. This has an impact on the ionization history of the Universe and measurements of the optical depth to reionization, of the evolution of the global fraction of ionized gas and of the thermal history of the intergalactic medium, can be used to set constraints on the mass of the dark matter particle. However, the suppression of the fraction of ionized medium in these scenarios can be partly compensated by varying other parameters, as the ionization efficiency or the minimum mass for which halos can host star-forming galaxies. Here we use different data sets regarding the ionization and thermal histories of the Universe and, taking into account the degeneracies from several astrophysical parameters, we obtain a lower bound on the mass of thermal warm dark matter candidates of $m_X>1.3\mathrm{keV}$, or $m_s>5.5\mathrm{keV}$ for the case of sterile neutrinos nonresonantly produced in the early Universe, both at 90% confidence level.