With a sample of $225.3\times {10}^6$ $J/\psi$ events taken with the BESIII detector, the decay $J/\psi \to \gamma 3({\pi }^{+}{\pi }^{-})$ is analyzed. A structure at $1.84\mathrm{GeV}/c^2$ is observed in the $3({\pi }^{+}{\pi }^{-})$ invariant mass spectrum with a statistical significance of $7.6\sigma$. The mass and width are measured to be $M=1842.2\pm {4.2}_{-2.6}^{+7.1}\mathrm{MeV}/c^2$ and $\Gamma =83\pm 14\pm 11\mathrm{MeV}$. The product branching fraction is determined to be $B(J/\psi \to \gamma X(1840))\times B(X(1840)\to 3({\pi }^{+}{\pi }^{-}))=(2.44\pm {0.36}_{-0.74}^{+0.60})\times {10}^{-5}$. No ${\eta }^{\prime }$ signals are observed in the $3({\pi }^{+}{\pi }^{-})$ invariant mass spectrum, and the upper limit of the branching fraction for the decay ${\eta }^{\prime }\to 3({\pi }^{+}{\pi }^{-})$ is set to be $3.1\times {10}^{-5}$ at a 90% confidence level.

We report a study of the suppressed decay $B^{-}\to D{K}^{-}$, $D\to K^{+}{\pi }^{-}{\pi }^0$, where $D$ denotes either a $D^0$ or a ${\overline{D}}^0$ meson. The decay is sensitive to the $CP$ -violating parameter ${\varphi }_3$. Using a data sample of $772\times {10}^6$ $B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the Belle detector, we measure the ratio of branching fractions of the above suppressed decay to the favored decay $B^{-}\to D{K}^{-}$, $D\to K^{-}{\pi }^{+}{\pi }^0$. Our result is $R_{DK}=[1.98\pm 0.62(\mathrm{stat})\pm 0.24(\mathrm{syst})]\times {10}^{-2}$, which indicates the first evidence of the signal for this suppressed decay with a significance of 3.2 standard deviations. We measure the direct $CP$ asymmetry between the suppressed $B^{-}$ and $B^{+}$ decays to be $A_{DK}=0.41\pm 0.30(\mathrm{stat})\pm 0.05(\mathrm{syst})$. We also report measurements for the analogous quantities $R_{D\pi }$ and $A_{D\pi }$ for the decay $B^{-}\to D{\pi }^{-}$, $D\to K^{+}{\pi }^{-}{\pi }^0$.

Magnetic catalysis of the chiral symmetry breaking and other magnetic properties of the ($2+1$)-dimensional Gross-Neveu model are studied, taking into account the Zeeman interaction of spin-$1/2$ quasiparticles (electrons) with a tilted (with respect to a system plane) external magnetic field $\overrightarrow{B}={\overrightarrow{B}}_{\perp }+{\overrightarrow{B}}_{\parallel }$. The Zeeman interaction is proportional to the magnetic moment ${\mu }_B$ of electrons. For simplicity, temperature and chemical potential are equal to zero throughout the paper. We compare, in the framework of the model, the above-mentioned phenomena both at ${\mu }_B=0$ and ${\mu }_B\ne 0$. It is shown that at ${\mu }_B\ne 0$ the magnetic catalysis effect is drastically changed in comparison with the ${\mu }_B=0$ case. Namely, at ${\mu }_B\ne 0$ the chiral symmetry, being spontaneously broken by $\overrightarrow{B}$ at subcritical coupling constants, is always restored at $|\overrightarrow{B}|\to \infty$ (even at ${\overrightarrow{B}}_{\parallel }=0$). Moreover, it is proved in this case that chiral symmetry can be restored simply by tilting $\overrightarrow{B}$ to a system plane, and in the region $B_{\perp }\to 0$ the de Haas–van Alphen oscillations of the magnetization are observed. At supercritical values of the coupling constant we have found two chirally noninvariant phases which respond differently on the action of $\overrightarrow{B}$. The first (at rather small values of $|\overrightarrow{B}|$) is a diamagnetic phase, in which there is an enhancement of the chiral condensate, whereas the second is a paramagnetic chirally broken phase. Numerical estimates show that phase transitions described in the paper can be achieved at low enough laboratory magnetic fields.

Cosmological billiards arise as a map of the solution to the Einstein equations, when the most general symmetry of the metric tensor is implemented, under the Belinskii, Khalatnikov and Lifshitz (BKL) paradigm, for which points are spatially decoupled in the asymptotical limit close to the cosmological singularity. Cosmological billiards in $4=3+1$ dimensions for the case of pure gravity are analyzed for those features, for which the content of Weyl reflections in the BKL maps requires the definition of a three-dimensional restricted phase space. The role of Poincaré sections in these processes is outlined. The quantum regime is investigated within this framework: as a result, one-epoch BKL eras are found to be the most probable configuration at which the wave functions have to be evaluated; furthermore, BKL eras containing $n\gg 1$ epochs are shown to be a less probable configuration for the wave functions. This description of the dynamics allows one to gain information about the connections between the statistical characterization of the maps which imply the different symmetry-quotienting mechanisms and the characterization of the semiclassical limit of the wave functions, for which evidence is produced for the phenomenon of “scars,” here for the first time outlined for the wave function of the universe in cosmological billiards, analyzed for the lowest silver ratios, and compared with the implications of a Farey map. The connections between the classical BKL probabilties and the quanum BKL probabilities for the “scarred” wave functions of the universe are provided and compared within different expansions according to different limits of the BKL statistics

Some basic features of black-hole statistical mechanics are investigated, assuming that black holes respect the principles of quantum mechanics. Care is needed in defining an entropy $S_{\mathrm{bh}}$ corresponding to the number of microstates of a black hole, given that the black hole interacts with its surroundings. An open question is then the relationship between this entropy and the Bekenstein-Hawking entropy $S_{\mathrm{BH}}$. For a wide class of models with interactions needed to ensure unitary quantum evolution, these interactions produce extra energy flux beyond that predicted by Hawking. Arguments are then presented that this results in an entropy $S_{\mathrm{bh}}$ that is smaller than $S_{\mathrm{BH}}$. Correspondingly, in such scenarios equilibrium properties of black holes are modified. We examine questions of consistency of such an inequality; if it is not consistent, that provides significant constraints on models for quantum-mechanical black hole evolution.

We show that a large contribution to tensor modes during inflation can be generated by a spectator scalar field with a speed of sound lower than unity.

It is known that power-law k-inflation can be realized for the Lagrangian $P=Xg(Y)$, where $X=-(\partial \varphi {)}^2/2$ is the kinetic energy of a scalar field $\varphi$ and $g$ is an arbitrary function in terms of $Y=X{e}^{\lambda \varphi /M_{\mathrm{pl}}}$ ($\lambda$ is a constant and $M_{\mathrm{pl}}$ is the reduced Planck mass). In the presence of a vector field coupled to the inflaton with an exponential coupling $f(\varphi )\propto e^{\mu \varphi /M_{\mathrm{pl}}}$, we show that the models with the Lagrangian $P=Xg(Y)$ generally give rise to anisotropic inflationary solutions with $\Sigma /H=\mathrm{\text{constant}}$, where $\Sigma$ is an anisotropic shear and $H$ is an isotropic expansion rate. Provided these anisotropic solutions exist in the regime where the ratio $\Sigma /H$ is much smaller than 1, they are stable attractors irrespective of the forms of $g(Y)$. We apply our results to concrete models of k-inflation such as the generalized dilatonic ghost condensate and the Dirac-Born-Infeld model and we numerically show that the solutions with different initial conditions converge to the anisotropic power-law inflationary attractors. Even in the de Sitter limit ($\lambda \to 0$) such solutions can exist, but in this case the null energy condition is generally violated. The latter property is consistent with the Wald’s cosmic conjecture stating that the anisotropic hair does not survive on the de Sitter background in the presence of matter respecting the dominant/strong energy conditions.

The Large Hadron Collider can do precision physics at a level that is competitive with electroweak precision constraints when probing physics beyond the Standard Model. We present a simple yet general parametrization of the effect of an arbitrary number of lepton-quark contact interactions on any dilepton observable at hadron colliders. This parametrization can be easily adopted by the experimental collaborations to put bounds on arbitrary combinations of lepton-quark contact interactions. We compute the corresponding bounds from current dilepton resonance searches at the LHC and find that they are competitive with and often complementary to indirect constraints from electroweak precision data. We combine all current constraints in a global analysis to obtain the most stringent bounds on lepton-quark contact interactions. We also show that the high-energy phase of the LHC has a unique potential in terms of discovery and discrimination power among different types of lepton-quark contact interactions.

We show that the usual linear analysis of quark-gluon plasma Weibel instabilities based on the Maxwell–Boltzmann equation may be reproduced in a purely hydrodynamic model. The latter is derived by the entropy production variational method from a transport equation including collisions and can describe highly nonequilibrium flow. We find that, as expected, collisions slow down the growth of Weibel instabilities. Finally, we discuss the strong momentum anisotropy limit.

We derive a recursion relation for the analytic leading logarithmic coefficients of a final state gluon cascade. We demonstrate the potential of our method by analytically computing the rate coefficients for the emission of up to 80 gluons in both the exclusive-$k_t$ (Durham) and generalized inclusive-$k_t$ class of jet algorithms. There is a particularly simple form for the ratios of resolved coefficients. We suggest potential applications for our method including the efficient generation of shower histories.

By assuming that $Y(4260)$ is a $D_1\overline{D}$ molecular state, we investigate some hidden-charm and charmed pair decay channels of $Y(4260)$ via intermediate $D_1\overline{D}$ meson loops with an effective Lagrangian approach. Through investigating the $\alpha$ dependence of branching ratios and ratios between different decay channels, we show that the intermediate $D_1\overline{D}$ meson loops are crucial for driving these transitions of $Y(4260)$ studied here. The coupled channel effects turn out to be more important in $Y(4260)\to D^{*}{\overline{D}}^{*}$, which can be tested in future experiments.

The ongoing and future searches for diffuse supernova neutrinos and sterile neutrinos carried out with large water-Cherenkov detectors require a precise determination of the backgrounds, especially those involving $\gamma$ rays. Of great importance, in this context, is the process of neutron knockout through neutral-current scattering of atmospheric neutrinos on oxygen. Nuclear reinteractions of the produced neutron may in fact lead to the production of $\gamma$ rays of energies high enough to mimic the processes of interest. In this article, we focus on the kinematical range suitable for simulations of atmospheric-neutrino interactions and provide the neutron-knockout cross sections computed using the formalism based on the realistic nuclear spectral function. The role of the strange-quark contribution to the neutral-current axial form factor is also analyzed. Based on the available experimental information, we give an estimate of the associated uncertainty.

We present a measurement of the production cross section for $ZW$ and $ZZ$ boson pairs in final states with a pair of charged leptons, from the decay of a $Z$ boson, and at least two jets, from the decay of a $W$ or $Z$ boson, using the full sample of proton-antiproton collisions recorded with the CDF II detector at the Tevatron, corresponding to $8.9{\mathrm{fb}}^{-1}$ of integrated luminosity. We increase the sensitivity to vector-boson decays into pairs of quarks using a neural-network discriminant that exploits the differences between the spatial spread of energy depositions and charged-particle momenta contained within the jet of particles originating from quarks and gluons. Additionally, we employ new jet energy corrections to Monte Carlo simulations that account for differences in the observed energy scales for quark and gluon jets. The number of signal events is extracted through a simultaneous fit to the dijet mass spectrum in three classes of events: events likely to contain jets with a heavy-quark decay, events likely to contain jets originating from light quarks, and events that fail these identification criteria. We determine the production cross section to be ${\sigma }_{ZW+ZZ}={2.5}_{-1.0}^{+2.0}\mathrm{pb}$ ($<6.1\mathrm{pb}$ at the 95% confidence level), consistent with the standard model prediction of 5.1 pb.

We consider a lattice formulation of the four-dimensional $N=1$ Wess-Zumino model in terms of the Ginsparg-Wilson relation. This formulation has an exact supersymmetry on the lattice. The lattice action is invariant under a deformed supersymmetric transformation, which is nonlinear in the scalar fields, and it is determined by an iterative procedure in the coupling constant to all orders in perturbation theory. We also show that the corresponding Ward-Takahashi identity is satisfied at fixed lattice spacing. The calculation is performed in lattice perturbation theory up to order $g^3$ (two loops), and the Ward-Takahashi identity (containing 110 connected nontadpole Feynman diagrams) is satisfied at fixed lattice spacing thanks to this exact lattice supersymmetry.

In this paper, by presenting the potentials of Kaluza-Klein (KK) modes in the corresponding Schrödinger equations, we investigate the localization and resonances of gravity and fermion on the symmetric and asymmetric Bloch branes. We find that the localization properties of zero modes for gravity and fermion in the symmetric brane case are the same, whereas, for the asymmetric brane case, the fermion zero mode is localized on one of the sub-branes, while the gravity zero mode is localized on another sub-brane. The spectra of the gravity and the left- or right-handed fermion are composed of a bound zero mode and a series of gapless continuous massive KK modes. Among the continuous massive KK modes, we obtain some discrete gravity and fermion resonant (quasilocalized) KK states on the brane, which have a finite probability of escaping into the bulk. The KK states with lower resonant masses have a longer lifetime on the brane. And the number of the resonant KK states increases linearly with the width of the brane and the scalar-fermion coupling constant, but it decreases with the asymmetric factor $\beta$. The structure of the resonance spectrum is investigated in detail.

We perform a detailed study of the existence and the properties of $O(4)$-invariant instanton solutions in Einstein-scalar theory in the presence of flat potential barriers, i.e. barriers where the second derivative of the potential is small at the top of the barrier. We find a whole zoo of solutions: Hawking-Moss, Coleman–de Luccia (CdL), oscillating instantons, and asymmetric CdL as well as other nonstandard CdL-like solutions with additional negative modes in their spectrum of fluctuations. Our work shows how these different branches of solutions are connected to each other via “critical” instantons possessing an extra zero-mode fluctuation. Overall, the space of finite-action Euclidean solutions to these theories with flat barriers is surprisingly rich and intricate. We find that critical instantons provide the key to understanding both the existence and the properties of instanton solutions.

We consider the Einstein-Gauss-Bonnet gravity with a negative cosmological constant together with a source given by a scalar field nonminimally coupled in arbitrary dimension $D$. For a certain election of the cosmological and Gauss-Bonnet coupling constants, we derive two classes of AdS black hole solutions whose horizon is planar. The first family of black holes obtained for a particular value of the nonminimal coupling parameter only depends on a constant $M$, and the scalar field vanishes as $M=0$. The second class of solutions corresponds to a two-parametric (with constants $M$ and $A$) black hole stealth configuration, which is a nontrivial scalar field with a black hole metric such that both sides (gravity and matter parts) of the Einstein equations vanish. In this case, in the vanishing $M$, the solution reduces to a stealth scalar field on the pure AdS metric. We note that the existence of these two classes of solutions is indicative of the particular choice of the coupling constants, and they cannot be promoted to spherical or hyperboloid black hole solutions in a standard fashion. In the last part, we add to the original action some exact ($D-1$) forms coupled to the scalar field. The direct benefit of introducing such extra fields is to obtain black hole solutions with a planar horizon for an arbitrary value of the nonminimal coupling parameter.

It is well known that the Jordan and Einstein frames are equivalent to each other in classical Brans-Dicke theory, provided that one and the same metric is employed for the physical space-time. Nevertheless, it is shown in this paper that by cosmological models the loop quantization in the two different frames leads to inequivalent effective theories. Analytical solutions are found in both frames for the effective loop quantum Brans-Dicke cosmology without potential in (i) the vacuum case and (ii) the additional massless scalar field case. In the Einstein frame, the analytical solution for the Brans-Dicke potential $\propto {\phi }^2$ is found. In all of those solutions, the bouncing evolution of the scale factor is obtained around the Planck regime. The differences between the loop quantization of the two frames are reflected by (i) the evolution of the scale factor around the bounce and (ii) the scale of the bounce in the physical Jordan frame.

State-of-the-art computations of the gravitational self-force (GSF) on massive particles in black hole spacetimes involve numerical evolution of the metric perturbation equations in the time domain, which is computationally very costly. We present here a new strategy based on a frequency-domain treatment of the perturbation equations, which offers considerable computational saving. The essential ingredients of our method are (i) a Fourier-harmonic decomposition of the Lorenz-gauge metric perturbation equations and a numerical solution of the resulting coupled set of ordinary equations with suitable boundary conditions; (ii) a generalized version of the method of extended homogeneous solutions [L. Barack, A. Ori, and N. Sago, Phys. Rev. D 78, 084021 (2008)] used to circumvent the Gibbs phenomenon that would otherwise hamper the convergence of the Fourier mode sum at the particle’s location; (iii) standard mode-sum regularization, which finally yields the physical GSF as a sum over regularized modal contributions. We present a working code that implements this strategy to calculate the Lorenz-gauge GSF along eccentric geodesic orbits around a Schwarzschild black hole. The code is far more efficient than existing time-domain methods; the gain in computation speed (at a given precision) is about an order of magnitude at an eccentricity of 0.2, and up to 3 orders of magnitude for circular or nearly circular orbits. This increased efficiency was crucial in enabling the recently reported calculation of the long-term orbital evolution of an extreme mass ratio inspiral [N. Warburton, S. Akcay, L. Barack, J. R. Gair, and N. Sago, Phys. Rev. D 85, 061501(R) (2012)]. Here we provide full technical details of our method to complement the above report.

We consider compact binary systems in $f(R)$ gravity theories in the Palatini approach and calculate the post-Newtonian parameters to 1.5PN order using the method of direct integration of the relaxed Einstein equations (DIRE). The Palatini-type modifications of gravity can be formulated as Einstein’s gravity with a modified response to matter sources, and it is shown in detail how to treat these correctly within the DIRE formalism. Our results explicitly confirm the expectation that for binary black holes the new effects can be absorbed into redefinitions of the binary masses, rendering such systems observationally identical to general relativity.