We search for evidence of resonant top quark pair production in 955 ${\mathrm{pb}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ recorded with the CDF II detector at the Fermilab Tevatron. For fully reconstructed candidate $t\overline{t}$ events triggered on leptons with large transverse momentum and containing at least one identified $b$-quark jet, we compare the invariant mass spectrum of $t\overline{t}$ pairs to the expected superposition of standard model $t\overline{t}$, non-$t\overline{t}$ backgrounds, and a simple resonance model based on a sequential $Z^{\prime }$ boson. We establish upper limits for $\sigma (p\overline{p}\to Z^{\prime })·Br(Z^{\prime }\to t\overline{t})$ in the $Z^{\prime }$ mass interval from $450\mathrm{GeV}/c^2$ to $900\mathrm{GeV}/c^2$. A topcolor leptophobic $Z^{\prime }$ is ruled out below $720\mathrm{GeV}/c^2$, and the cross section of any narrow $Z^{\prime }$-like state decaying to $t\overline{t}$ is found to be less than 0.64 pb at 95% C.L. for $M_{Z^{\prime }}$ above $700\mathrm{GeV}/c^2$.

The stability of squashed Kaluza-Klein black holes is studied. The squashed Kaluza-Klein black hole looks like a five-dimensional black hole in the vicinity of horizon and looks like a four-dimensional Minkowski spacetime with a circle at infinity. In this sense, squashed Kaluza-Klein black holes can be regarded as black holes in the Kaluza-Klein spacetimes. Using the symmetry of squashed Kaluza-Klein black holes, $SU(2)\times U(1)\simeq U(2)$, we obtain master equations for a part of the metric perturbations relevant to the stability. The analysis based on the master equations gives strong evidence for the stability of squashed Kaluza-Klein black holes. Hence, the squashed Kaluza-Klein black holes deserve to be taken seriously as realistic black holes in the Kaluza-Klein spacetime.

Very high energy gamma rays are expected to be absorbed by the extragalactic background light over cosmological distances via the process of electron-positron pair production. Recent observations of cosmologically distant gamma-ray emitters by ground based gamma-ray telescopes have, however, revealed a surprising degree of transparency of the universe to very high energy photons. One possible mechanism to explain this observation is the oscillation between photons and axionlike particles (ALPs). Here we explore this possibility further, focusing on photon-ALP conversion in the magnetic fields in and around gamma-ray sources and in the magnetic field of the Milky Way, where some fraction of the ALP flux is converted back into photons. We show that this mechanism can be efficient in allowed regions of the ALP parameter space, as well as in typical configurations of the galactic magnetic field. As case examples, we consider the spectrum observed from two HESS sources: $1\mathrm{ES}1101\mathrm{\text{−}}232$ at redshift $z=0.186$ and $\mathrm{H}2356\mathrm{\text{−}}309$ at $z=0.165$. We also discuss features of this scenario which could be used to distinguish it from standard or other exotic models.

The inverse amplitude method is a powerful unitarization technique to enlarge the energy applicability region of effective Lagrangians. It has been widely used to describe resonances in hadronic physics, combined with chiral perturbation theory, as well as in the strongly interacting symmetry breaking sector. In this work we show how it can be slightly modified to also account for the subthreshold region, incorporating correctly the Adler zeros required by chiral symmetry and eliminating spurious poles. These improvements produce negligible effects on the physical region.

We compute the energy spectrum of gluelumps defined as gluonic excitations bound to a localized, static octet source. We are able to reproduce the nontrivial ordering of the spin-parity levels and show how this is related to the non-Abelian part of the Coulomb interaction between color charges.

The decay $\varphi \to f_0(980)\gamma$ and process $e^{+}{e}^{-}\to \varphi f_0(980)$ are considered within the local Nambu-Jona-Lasinio model. In the amplitudes of these processes, contributions of $s$-quark and kaon loops are taken into account. The kaon loop gives a dominant contribution. Our estimation for the decay width of $\varphi \to f_0\gamma$ is in satisfactory agreement with recent experimental data. This allows us to make some predictions for cross sections of the process $e^{+}{e}^{-}\to {\gamma }^{*}\to \varphi f_0$ which can be tested in the C-$\tau$ factory. The total and differential cross sections of this process are calculated and presented in the figures.

As a particle moves through a fluid, it may generate a laminar wake behind it. In the gauge-string duality, we show that such a diffusion wake is created by a heavy quark moving through a thermal plasma and that it has a universal strength when compared to the total drag force exerted on the quark by the plasma. The universality extends over all asymptotically anti-de Sitter supergravity constructions with arbitrary scalar matter. We discuss how these results relate to the linearized hydrodynamic approximation and how they bear on our understanding of di-hadron correlators in heavy ion collisions.

The leading order corrections to Reissner–Nordstrom solutions of the Einstein’s equations on noncommutative spacetime have been worked out based on a noncommutative gauge theory of gravity. From the corrected metric the horizons have been derived and the curvature scalar is also computed. The introduction of noncommutativity leads to the removal of the coordinate singularities.

We reexamine the idea that the origin of black-hole entropy may lie in the entanglement of quantum fields between the inside and outside of the horizon. Motivated by the observation that certain modes of gravitational fluctuations in a black-hole background behave as scalar fields, we compute the entanglement entropy of such a field, by tracing over its degrees of freedom inside a sphere. We show that while this entropy is proportional to the area of the sphere when the field is in its ground state, a correction term proportional to a fractional power of area results when the field is in a superposition of ground and excited states. The area law is thus recovered for large areas. Further, we identify the location of the degrees of freedom that give rise to the above entropy.

I show that several observable properties of bursting neutron stars in metric theories of gravity can be calculated using only conservation laws, Killing symmetries, and the Einstein equivalence principle, without requiring the validity of the general relativistic field equations. I calculate, in particular, the gravitational redshift of a surface atomic line, the touchdown luminosity of a radius-expansion burst, which is believed to be equal to the Eddington critical luminosity, and the apparent surface area of a neutron star as measured during the cooling tails of bursts. I show that, for a general metric theory of gravity, the apparent surface area of a neutron star depends on the coordinate radius of the stellar surface and on its gravitational redshift in the exact same way as in general relativity. On the other hand, the Eddington critical luminosity depends also on an additional parameter that measures the degree to which the general relativistic field equations are satisfied. These results can be used in conjunction with current and future high-energy observations of bursting neutron stars to test general relativity in the strong-field regime.

We investigate an effective Hamiltonian for QCD at large $s$, in which longitudinal gauge degrees of freedom are suppressed, but not eliminated. In an axial gauge the effective field theory is a set of coupled ($1+1$)-dimensional principal-chiral models, which are completely integrable. The confinement problem is solvable in this context, and we find the longitudinal and transverse string tensions with techniques already used for a similar Hamiltonian in ($2+1$) dimensions. We find some a posteriori justification for the effective Hamiltonian as an eikonal approximation. Hadrons in this approximation consist of partons, which are quarks and solitonlike excitations of the sigma models. Diffractive hadron-hadron scattering appears primarily due to exchange of longitudinal flux between partons.

A direct connection between physical parameters of general two-Higgs-doublet model (2HDM) potentials after electroweak symmetry breaking (EWSB) and the parameters that define the potentials before EWSB is established. These physical parameters, such as the mass matrix of the neutral Higgs bosons, have well-defined transformation properties under basis transformations transposed to the fields after EWSB. The relations are also explicitly written in a basis covariant form. Violation of these relations may indicate models beyond 2HDMs. In certain cases the whole potential can be defined in terms of the physical parameters. The distinction between basis transformations and reparametrizations is pointed out. Some physical implications are discussed.

We consider renormalizable $SO(10)$ Yukawa interactions and put the three fermionic 16-plets into the 3-dimensional irreducible $A_4$ representation. Scanning the possible $A_4$ representation assignments to the scalars, we find a unique case which allows one to accommodate the down-quark and charged-lepton masses. Assuming type II seesaw dominance, we obtain a viable scenario with the Zee-Wolfenstein neutrino mass matrix, i.e., the Majorana mass matrix with a vanishing diagonal. Contributions from the charged-lepton mass matrix resolve the well-known problems with lepton mixing arising from the vanishing diagonal. In our scenario, fermion masses and mixings are well reproduced for both normal and inverted neutrino mass spectra, and $b-\tau$ Yukawa unification and definite predictions for the effective mass in neutrinoless double-$\beta$ decay are obtained.

In a theory with broken supersymmetry, gaugino couplings renormalize differently from gauge couplings, as do higgsino couplings from Higgs boson couplings. As a result, we expect the gauge (Higgs boson) couplings and the corresponding gaugino (higgsino) couplings to evolve to different values under renormalization group evolution. We reexamine the renormalization group equations (RGEs) for these couplings in the minimal supersymmetric standard model (MSSM). To include threshold effects, we calculate the $\beta$ functions using a sequence of (nonsupersymmetric) effective theories with heavy particles decoupled at the scale of their mass. We find that the difference between the SM couplings and their SUSY cousins that is ignored in the literature may be larger than two-loop effects which are included, and further that renormalization group evolution induces a nontrivial flavor structure in gaugino interactions. We present here the coupled set of RGEs for these dimensionless gauge and Yukawa-type couplings. The RGEs for the dimensionful soft-supersymmetry-breaking parameters of the MSSM will be presented in a companion paper.

Electroweak Sudakov logarithms at high energy, of the form $(\alpha /{sin}^2{\theta }_W{)}^n{log}^{m}s/M_{Z,W}^2$, are summed using effective theory methods. The corrections are computed to processes involving two external particles in the standard model. The results include nonzero particle masses, such as the $t$-quark mass, electroweak mixing effects which lead to unequal $W$ and $Z$ masses, and radiative Higgs corrections proportional to the Yukawa couplings. We show that the matching at the scale $M_{W,Z}$ has a term at most linear in $\log s/{\mu }^2$ to all orders. The effective theory formalism is compared with, and extends, previous work based on infrared evolution equations.

In a perturbative QCD approach, with inclusion of spin and transverse momentum effects, experimental data on azimuthal asymmetries observed in polarized semiinclusive deeply inelastic scattering and $e^{+}{e}^{-}$ annihilations can be used to determine the Sivers, transversity, and Collins soft functions. By using these functions, within the same scheme, we predict $p^{\uparrow }p\to h+X$ single spin asymmetries in remarkable agreement with high energy experimental data.