We calculate the $\mathcal{O}({\alpha }_s)$ radiative corrections to the spin-dependent differential decay rates of the process $t\to b+W^{+}$. These are needed to study the angular distribution of the energy of hadrons produced in polarized top quark decays at next-to-leading order. In our previous work, we studied the angular distribution of the scaled energy of bottom-flavored hadrons ($B$) from polarized top quark decays, using a specific helicity coordinate system where the top quark spin was measured relative to the bottom momentum (system 1). Here, we study the angular distribution of the energy spectrum of $B$ hadrons in a different helicity system, where the top spin is specified relative to the $W$ momentum (system 2). These energy distributions are governed by the polarized and unpolarized rate functions which are related to the density matrix elements of the decay $t\to W^{+}+b$. Through this paper, we present our predictions of the $B$-hadron spectrum in the polarized and unpolarized top decay and shall compare the polarized results in two different helicity systems. These predictions can be used to determine the polarization states of top quarks and also provide direct access to the $B$-hadron fragmentation functions, and allow us to deepen our knowledge of the hadronization process.

The process $e^{+}{e}^{-}\to n\overline{n}$ has been studied at the VEPP-2000 $e^{+}{e}^{-}$ collider with the SND detector in the energy range from threshold up to 2 GeV. As a result of the experiment, the $e^{+}{e}^{-}\to n\overline{n}$ cross section and effective neutron form factor have been measured.

In this paper we refine a conjecture relating the time-dependent size of an Einstein-Rosen bridge (ERB) to the computational complexity of the dual quantum state. Our refinement states that the complexity is proportional to the spatial volume of the ERB. More precisely, up to an ambiguous numerical coefficient, we propose that the complexity is the regularized volume of the largest codimension one surface crossing the bridge, divided by $G_N{l}_{\mathrm{AdS}}$. We test this conjecture against a wide variety of spherically symmetric shock wave geometries in different dimensions. We find detailed agreement.

In the probe limit, we numerically construct a holographic $p$-wave superfluid model in the four-dimensional (4D) and five-dimensional (5D) anti-de Sitter black holes coupled to a Maxwell-complex vector field. We find that, for the condensate with the fixed superfluid velocity, the results are similar to the $s$-wave cases in both 4D and 5D spacetimes. In particular, the Cave of Winds and the phase transition, always being of second order, take place in the 5D case. Moreover, we find that the translating superfluid velocity from second order to first order $\frac{S_y}{\mu }$ increases with the mass squared. Furthermore, for the supercurrent with fixed temperature, the results agree with the Ginzburg-Landau prediction near the critical temperature. In addition, this complex vector superfluid model is still a generalization of the SU(2) superfluid model, and it also provides a holographic realization of the $H{e}_3$ superfluid system.

We construct boson star solutions in the presence of a phantom field, allowing for a nontrivial topology of the solutions. The wormholes residing at the core of the configurations lead to a number of qualitative changes of the boson star solutions. In particular, the typical spiraling dependence of the mass and the particle number on the frequency of the boson stars is lost. Instead, the boson stars with nontrivial topology approach a singular configuration in the limit of vanishing frequency. Depending on the value of the coupling constant, the wormhole geometry changes from a single throat configuration to a double throat configuration, featuring a belly in between the two throats. Depending on the mass of the boson field and its self-interaction, the mass and the size of these objects cover many orders of magnitude, making them amenable to various astrophysical observations. A stability analysis reveals that the unstable mode of the Ellis wormhole is retained in the presence of the bosonic matter. However, the negative eigenvalue can get very close to zero, by tuning the parameters of the self-interaction potential appropriately.

We argue using simple models that all successful practical uses of probabilities originate in quantum fluctuations in the microscopic physical world around us, often propagated to macroscopic scales. Thus we claim there is no physically verified fully classical theory of probability. We comment on the general implications of this view, and specifically question the application of purely classical probabilities to cosmology in cases where key questions are known to have no quantum answer. We argue that the ideas developed here may offer a way out of the notorious measure problems of eternal inflation.

We pursue the group-theoretical method to study Isgur-Wise (IW) functions. We extend the general formalism, formerly applied to the baryon case $j^P=0^{+}$ (for ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c\ell {\overline{\nu }}_{\ell }$), to mesons with $j^P={\frac{1}{2}}^{-}$, i.e. $\overline{B}\to D(D^{(*)})\ell \nu$. In this case, which is more involved from the angular momentum point of view, only the principal series of unitary representations of the Lorentz group contribute. We obtain an integral representation for the IW function $\xi (w)$ with a positive measure, recover the bounds for the slope and the curvature of $\xi (w)$ obtained from the Bjorken-Uraltsev sum-rule method, and get new bounds for higher derivatives. We demonstrate also that if the lower bound for the slope is saturated, the measure is a $\delta$ function, and $\xi (w)$ is given by an explicit elementary function. Inverting the integral formula, we obtain the measure in terms of the IW function, allowing us to formulate criteria to decide if a given Ansatz for the Isgur-Wise function is compatible or not with the sum-rule constraints. Moreover, we obtain an upper bound on the IW function valid for any value of $w$. We compare these theoretical constraints to a number of forms for $\xi (w)$ proposed in the literature. The “dipole” function $\xi (w)={(\frac{2}{w+1})}^{2c}$ satisfies all constraints for $c\ge \frac{3}{4}$, while the QCD sum rule result including condensates does not satisfy them. Special care is devoted to the Bakamjian-Thomas relativistic quark model in the heavy-quark limit and to the description of the Lorentz group representation that underlies this model. Consistently, the IW function satisfies all Lorentz group criteria for any explicit form of the meson Hamiltonian at rest.

Charmed scalar meson spectroscopy has become a hot topic on both experimental and theoretical sides. The $B_{(s)}$ decays provide an ideal place to study their properties. We employ the $B$-meson light-cone sum rules to calculate the ${\overline{B}}_s^0\to D_{s0}^{*+}(2317)$ and $B^{-}\to D_0^{*0}(2400)$ transition form factors at the large recoil region assuming $D_{s0}^{*+}(2317)$ and $D_0^{*0}(2400)$ are scalar quark-antiquark states. The results are extrapolated to the whole momentum region in heavy quark effective theory. We also estimate the $DK$ continuum state contribution to ${\overline{B}}_s^0\to D_{s0}^{*+}(2317)$ form factors with a phenomenological method. Compared with the resonance contribution, it is less than 15% for $f_{B{D}_{s0}^{*}}^{+}$ and about 60% for $f_{B{D}_{s0}^{*}}^{-}$. After including the theoretical uncertainties, our results can be consistent with the previous studies. The branching ratios of semileptonic decays ${\overline{B}}_s^0\to D_{s0}^{*+}(2317)l{\overline{\nu }}_l$ and $B^{-}\to D_0^{*0}(2400)l{\overline{\nu }}_l$ are then evaluated. For the light lepton final state, $\mathrm{Br}({\overline{B}}_s^0\to D_{s0}^{*+}(2317)l{\overline{\nu }}_l)$ is around $6.0\times {10}^{-3}$, which is decreased to about $0.8\times {10}^{-3}$ for the tau final state due to the phase space effect. The predicted branching ratio of $B^{-}\to D_0^{*0}(2400)l{\overline{\nu }}_l$ is slightly larger than that of ${\overline{B}}_s^0\to D_{s0}^{*+}(2317)l{\overline{\nu }}_l$.

This article presents measurements of the $t$-channel single top-quark ($t$) and top-antiquark ($\overline{t}$) total production cross sections $\sigma (tq)$ and $\sigma (\overline{t}q)$, their ratio $R_t=\sigma (tq)/\sigma (\overline{t}q)$, and a measurement of the inclusive production cross section $\sigma (tq+\overline{t}q)$ in proton-proton collisions at $\sqrt{s}=7\mathrm{TeV}$ at the LHC. Differential cross sections for the $tq$ and $\overline{t}q$ processes are measured as a function of the transverse momentum and the absolute value of the rapidity of $t$ and $\overline{t}$, respectively. The analyzed data set was recorded with the ATLAS detector and corresponds to an integrated luminosity of $4.59{\mathrm{fb}}^{-1}$. Selected events contain one charged lepton, large missing transverse momentum, and two or three jets. The cross sections are measured by performing a binned maximum-likelihood fit to the output distributions of neural networks. The resulting measurements are $\sigma (tq)=46\pm 1(\text{stat})\pm 6(\text{syst})\mathrm{pb}$, $\sigma (\overline{t}q)=23\pm 1(\text{stat})\pm 3(\text{syst})\mathrm{pb}$, $R_t=2.04\pm 0.13(\text{stat})\pm 0.12(\text{syst})$, and $\sigma (tq+\overline{t}q)=68\pm 2(\text{stat})\pm 8(\text{syst})\mathrm{pb}$, consistent with the Standard Model expectation. The uncertainty on the measured cross sections is dominated by systematic uncertainties, while the uncertainty on $R_t$ is mainly statistical. Using the ratio of $\sigma (tq+\overline{t}q)$ to its theoretical prediction, and assuming that the top-quark-related CKM matrix elements obey the relation $|V_{tb}|\gg |V_{ts}|,|V_{td}|$, we determine $|V_{tb}|=1.02\pm 0.07$.

The charmless three-body decay modes $B^{\pm }\to K^{\pm }{\pi }^{+}{\pi }^{-}$, $B^{\pm }\to K^{\pm }{K}^{+}{K}^{-}$, $B^{\pm }\to {\pi }^{\pm }{K}^{+}{K}^{-}$ and $B^{\pm }\to {\pi }^{\pm }{\pi }^{+}{\pi }^{-}$ are reconstructed using data, corresponding to an integrated luminosity of $3.0{\mathrm{fb}}^{-1}$, collected by the LHCb detector. The inclusive $CP$ asymmetries of these modes are measured to be $$\begin{gathered} A_{CP}(B^{\pm }\to K^{\pm }{\pi }^{+}{\pi }^{-})=+0.025\pm 0.004\pm 0.004\pm 0.007, \\ {A}_{CP}(B^{\pm }\to K^{\pm }{K}^{+}{K}^{-})=-0.036\pm 0.004\pm 0.002\pm 0.007, \\ {A}_{CP}(B^{\pm }\to {\pi }^{\pm }{\pi }^{+}{\pi }^{-})=+0.058\pm 0.008\pm 0.009\pm 0.007, \\ {A}_{CP}(B^{\pm }\to {\pi }^{\pm }{K}^{+}{K}^{-})=-0.123\pm 0.017\pm 0.012\pm 0.007, \end{gathered}$$where the first uncertainty is statistical, the second systematic, and the third is due to the $CP$ asymmetry of the $B^{\pm }\to J/\psi K^{\pm }$ reference mode. The distributions of these asymmetries are also studied as functions of position in the Dalitz plot and suggest contributions from rescattering and resonance interference processes.

We measure the direct $CP$-violating parameter $A_{CP}$ for the decay of the charged charm meson, $D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}$ (and charge conjugate), using the full $10.4{\mathrm{fb}}^{-1}$ sample of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ collected by the D0 detector at the Fermilab Tevatron collider. We extract the raw reconstructed charge asymmetry by fitting the invariant mass distributions for the sum and difference of charge-specific samples. This quantity is then corrected for detector-related asymmetries using data-driven methods and for possible physics asymmetries (from $B\to D$ processes) using input from Monte Carlo simulation. We measure $A_{CP}=[-0.16\pm 0.15(\text{stat})\pm 0.09(\text{syst})]\%$, which is consistent with zero, as expected from the standard model prediction of $CP$ conservation, and is the most precise measurement of this quantity to date.

The Lorentz-violating model proposed by Myers and Pospelov suffers from a higher-derivative pathology due to a dimension-five operator. In particular, its electromagnetic sector exhibits a spectrum which contains, in addition to an expected massless photon, ghost contributions that could (in principle) spoil the unitarity of the model. We find that unitarity at tree level can be assured for pure spacelike, timelike, and lightlike background four-vectors (the last two under restrictions upon the allowed momenta). We then analyze the nonrelativistic interparticle potential energy behavior for different background four-vectors and compare to the usual Coulomb potential.

Tidal interactions have a significant influence on the late dynamics of compact binary systems, which constitute the prime targets of the upcoming network of gravitational-wave detectors. We refine the theoretical description of tidal interactions (hitherto known only to the second post-Newtonian level) by extending our recently developed analytic self-force formalism, for extreme-mass-ratio binary systems, to the computation of several tidal invariants. Specifically, we compute, to linear order in the mass ratio and to the 7.5th post-Newtonian order, the following tidal invariants: the square and the cube of the gravitoelectric quadrupolar tidal tensor, the square of the gravitomagnetic quadrupolar tidal tensor, and the square of the gravitoelectric octupolar tidal tensor. Our high-accuracy analytic results are compared to recent numerical self-force tidal data by Dolan et al. [arXiv:1406.4890 [Phys. Rev. D (to be published)] ], and, notably, provide an analytic understanding of the light ring asymptotic behavior found by them. We transcribe our kinematical tidal-invariant results in the more dynamically significant effective one-body description of the tidal interaction energy. By combining, in a synergetic manner, analytical and numerical results, we provide simple, accurate analytic representations of the global, strong-field behavior of the gravitoelectric quadrupolar tidal factor. A striking finding is that the linear-in-mass-ratio piece in the latter tidal factor changes sign in the strong-field domain, to become negative (while its previously known second post-Newtonian approximant was always positive). We, however, argue that this will be more than compensated by a probable fast growth, in the strong-field domain, of the nonlinear-in-mass-ratio contributions in the tidal factor.

The quantization of a vector model presenting spontaneous breaking of Lorentz symmetry in flat Minkowski spacetime is discussed. The Stueckelberg trick of introducing an auxiliary field along with a local symmetry in the initial Lagrangian is used to convert the second-class constraints present in the initial Lagrangian to first-class ones. An additional deformation is employed in the resulting Lagrangian to handle properly the first-class constraints, and the equivalence with the initial model is demonstrated using the BRST invariance of the deformed Lagrangian. The framework for performing perturbation theory is constructed, and the structure of the Fock space is discussed. Despite the presence of ghost and tachyon modes in the spectrum of the free theory, it is shown that one can implement consistent conditions to define a unitary and stable reduced Fock space. Within the restricted Fock space, the free model turns out to be equivalent to the Maxwell electrodynamics in the temporal gauge.

Scalar forces “screened” by the Vainshtein mechanism may hold the key to understanding the cosmological expansion of our Universe, while predicting new and exciting features in the interaction between massive bodies. Here we explore the dynamics of the Vainshtein screening mechanism, focusing on the decoupling limit of the DGP braneworld scenario and dRGT massive gravity. We show that there is a vast set of initial conditions whose evolution is well defined and which are driven to the static screening solutions of these theories. Screening solutions are stable and behave coherently under small fluctuations: they oscillate and eventually settle to an equilibrium configuration, the time scale for the oscillations and damping being dictated by the Vainshtein radius of the screening solutions. At very late times, a power-law decay ensues, in agreement with known analytical results. However, we also conjecture that physically interesting processes such as the gravitational collapse of compact stars may not possess a well-posed initial value problem. Finally, we construct solutions with nontrivial multipolar structure describing the screening field of deformed, asymmetric bodies and show that higher multipoles are screened more efficiently than the monopole component.

The quasinormal mode of a gravitating and magnetized fluid in a spatially flat, isotropic and homogeneous cosmological background is derived in the presence of the fluid sources of anisotropic stress and of the entropic fluctuations of the plasma. The obtained gauge-invariant description involves a system of two coupled differential equations of which the physical content is analyzed in all the most relevant situations. The Cauchy problem of large-scale curvature perturbations during the radiation dominated stage of expansion can be neatly formulated, and its general solution is shown to depend on five initial data assigned when the relevant physical wavelengths are larger than the particle horizon. The consequences of this approach are explored.

The $Wtb$ vertex structure and the search for new anomalous couplings is studied using top quark measurements obtained at the LHC, for a center-of-mass energy of 8 TeV. By combining the latest and most precise results on the single top quark production cross section and the measurements of the $W$-boson helicity fractions ($F_0$ and $F_L$), it is possible to set new limits, at a 95% C.L., on the real and imaginary components of the new couplings. The combination of the LHC observables clearly improves the limits obtained when using the individual results alone. The updated measurements of the $W$-boson helicity fractions and the $s+t$ channels’ electroweak single top quark production, at the Tevatron, improve the LHC limits when a world combination of all observables ($\mathrm{LHC}+\text{Tevatron}$) is performed.

A search has been performed, using the full $20.3{\mathrm{fb}}^{-1}$ data sample of 8 TeV proton-proton collisions collected in 2012 with the ATLAS detector at the LHC, for photons originating from a displaced vertex due to the decay of a neutral long-lived particle into a photon and an invisible particle. The analysis investigates the diphoton plus missing transverse momentum final state, and is therefore most sensitive to pair production of long-lived particles. The analysis technique exploits the capabilities of the ATLAS electromagnetic calorimeter to make precise measurements of the flight direction, as well as the time of flight, of photons. No excess is observed over the Standard Model predictions for background. Exclusion limits are set within the context of gauge mediated supersymmetry breaking models, with the lightest neutralino being the next-to-lightest supersymmetric particle and decaying into a photon and gravitino with a lifetime in the range from 250 ps to about 100 ns.

We study the magnetoresponse with nonconserved currents in holography. Nonconserved currents are dual to massive vector fields in anti–de Sitter (AdS). We introduce the mass in a gauge invariant way via the Stückelberg mechanism. In particular we find generalizations of the chiral magnetic effect, the chiral separation effect and the chiral magnetic wave. Since the associated charge is not conserved we need to source it explicitly by a coupling, the generalization of the chemical potential. In this setup we find that in general the anomalous transport phenomena are still realized. The values we find for nonzero mass connect continuously to the values of the anomalous conductivities of the consistent currents, i.e. the proper chiral magnetic effect vanishes for all masses (as it does for the consistent current in the zero mass case) whereas the chiral separation effect is fully present. The generalization of the chiral magnetic wave shows that for small momenta there is no propagating wave but two purely absorptive modes (one of them diffusive). At higher momenta we recover the chiral magnetic wave as a combination of the two absorptive modes. We also study the negative magneto resistivity and find that it grows quadratically with the magnetic field. The chiral magnetic wave and the negative magneto resistivity are manifestations of the chiral magnetic effect that takes place when the (nonconserved) charge is allowed to fluctuate freely in contrast to the case where the charge is fixed by an explicit source. Since the (classical) $U(1{)}_A$ symmetry of QCD is not at all a symmetry at the quantum level we also argue that using massive vectors in AdS to model the axial singlet current might result in a more realistic holographic model of QCD and should be a good starting point to investigate the dynamics of anomalous transport in the strongly coupled quark gluon plasma.

We derive new cosmological solutions of the ghost-free massive gravity with a general background metric in which the contribution of the mass sector to the metric one is modeled by an effective cosmological constant and an ideal fluid which obeys the first law of thermodynamics; thus, it satisfies the ordinary energy-momentum conservation or continuity equation.