We study signals at the LHC for the Kaluza-Klein (KK) excitations of electroweak charged gauge bosons in the framework of the standard model (SM) fields propagating in the bulk of a warped extra dimension. Such a scenario can solve both the Planck-weak and flavor hierarchy problems of the SM. There are two such charged states in this scenario with couplings to light quarks and leptons being suppressed relative to those in the SM, whereas the couplings to top/bottom quarks are enhanced, similar to the case of electroweak neutral gauge bosons previously studied. However, unlike the case of electroweak neutral gauge bosons, there is no irreducible QCD background (including pollution from possibly degenerate KK gluons) for decays to $\mathrm{\text{top}}+\mathrm{\text{bottom}}$ final states so that this channel is useful for the discovery of the charged states. Moreover, decays of electroweak charged gauge bosons to longitudinal $W$, $Z$ and Higgs are enhanced just as for the neutral bosons. However, unlike for the neutral gauge bosons, the purely leptonic (and hence clean) decay mode of the $WZ$ is fully reconstructible so that the ratio of the signal to the SM (electroweak) background can potentially be enhanced by restricting to the resonance region more efficiently. We show that such final states can give sensitivity to 2(3) TeV masses with an integrated luminosity of $100(300){\mathrm{fb}}^{-1}$. We emphasize that improvements in discriminating a QCD jet from a highly boosted hadronically decaying $W$, and a highly boosted top jet from a bottom jet will enhance the reach for these KK particles, and that the signals we study for the warped extra dimensional model might actually be applicable also to a wider class of nonsupersymmetric models of electroweak symmetry breaking.

Supersymmetric contributions to time independent asymmetry in $B_s^0\to J/\psi \varphi$ process are analyzed in view of recent Tevatron experimental measurements. We show that the experimental limits of the mass difference $\Delta M_{B_s}$ and the mercury electric dipole moment significantly constrain the supersymmetric (SUSY) contribution to $B_s^0\mathrm{\text{−}}{\overline{B}}_s^0$ mixing, so that $\sin 2{\beta }_s\lesssim 0.1$. We also point out that the one loop SUSY contribution to $B_s^0\to J/\psi \varphi$ decay can be important and can lead to large indirect $CP$ asymmetries which are different for different polarization states. These new physics effects in the decay amplitude can be consistent with $CP$ measurements in the $B_d$ system.

In this paper we investigate supersymmetric effects to the threshold production cross section of top-quark pairs in electron positron annihilation. In particular, we consider the complete one-loop corrections from the strong and weak sector of the minimal supersymmetric standard model.

The properties of the momentum-space quark propagator in the Landau gauge are studied for the overlap quark action in quenched lattice QCD. Numerical calculations are performed over four ensembles of gauge configurations, where three are smeared using either 1, 3, or 6 sweeps of stout-link smearing. We calculate the nonperturbative wave-function renormalization function $Z(p)$ and the nonperturbative mass function $M(p)$ for a variety of bare quark masses. We find that the wave-function renormalization function is slightly sensitive to the number of stout-link smearing sweeps. For the mass function we find the effect of the stout-link smearing algorithm to be small for moderate to light bare quark masses. For a heavy bare quark mass we find a strong dependence on the number of smearing sweeps.

We calculate the gluon structure function of a color dipole in near-light-cone $SU(2)$ lattice QCD as a function of $x_B$. The quark and antiquark are external nondynamical degrees of freedom which act as sources of the gluon string configuration defining the dipole. We compute the color dipole matrix element of transversal chromo-electric and chromo-magnetic field operators separated along a direction close to the light cone, the Fourier transform of which is the gluon structure function. As vacuum state in the pure glue sector, we use a variational ground state of the near-light-cone Hamiltonian. We derive a recursion relation for the gluon structure function on the lattice similar to the perturbative Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equation. It depends on the number of transversal links assembling the Schwinger string of the dipole. Fixing the mean momentum fraction of the gluons to the “experimental value” in a proton, we compare our gluon structure function for a dipole state with four links with the next-to-leading-order MRST 2002 and the CTEQ AB-0 parametrizations at $Q^2=1.5{\mathrm{GeV}}^2$. Within the systematic uncertainty we find rather good agreement. We also discuss the low $x_B$ behavior of the gluon structure function in our model calculation.

We describe how one may employ a very simple event selection, using only the kinematic variable $m_{T2}$, to search for new particles at the LHC. The method is useful when searching for evidence of models (such as $R$-parity conserving supersymmetry), which have a $Z_2$ parity and a weakly interacting lightest parity-odd particle. We discuss the kinematic properties which make this variable an excellent discriminant against the great majority of standard model backgrounds. Monte Carlo simulations suggest that this approach could be used to discover supersymmetry with somewhat smaller integrated luminosities (or perhaps lower center-of-mass energies) than would be required for other comparable analyses.

Here we prove unitarity of the recently found fourth-order (in derivatives) self-dual model of spin-2 by investigating the analytic structure of its propagator. The model describes massive particles of helicity $+2$ (or $-2$) in $D=2+1$ dimensions and corresponds to the quadratic truncation of a higher derivative topologically massive gravity about a flat background. It is an intriguing example of a theory where a term in the propagator of the form $1/[{\square }^2(\square -m^2)]$ does not lead to ghosts. The crucial role of the linearized Weyl symmetry in getting rid of the ghosts is pointed out. We use a peculiar pair of gauge conditions which fix the linearized reparametrizations and linearized Weyl symmetries separately.

Linearized fluctuations of quantized matter fields and the spacetime geometry around de Sitter space are considered in the case that the matter fields are conformally invariant. Taking the unperturbed state of the matter to be the de Sitter invariant Bunch-Davies state, the linear variation of the stress tensor about its self-consistent mean value serves as a source for fluctuations in the geometry through the semiclassical Einstein equations. This linear response framework is used to investigate both the importance of quantum backreaction and the validity of the semiclassical approximation in cosmology. The full variation of the stress tensor $\delta ⟨T^a{}_b⟩$ contains two kinds of terms: (1) those that depend explicitly upon the linearized metric variation $\delta g_{cd}$ through the $⟨[T^a{}_b,T^{cd}]⟩$ causal response function; and (2) state dependent variations, independent of $\delta g_{cd}$. For perturbations of the first kind, the criterion for the validity of the semiclassical approximation in de Sitter space is satisfied for fluctuations on all scales well below the Planck scale. The perturbations of the second kind contain additional massless scalar degrees of freedom associated with changes of state of the fields on the cosmological horizon scale. These scalar degrees of freedom arise necessarily from the local auxiliary field form of the effective action associated with the trace anomaly, are potentially large on the horizon scale, and therefore can lead to substantial nonlinear quantum backreaction effects in cosmology.

Mach’s principle is the proposition that inertial frames are determined by matter. We put forth and implement a precise correspondence between matter and geometry that realizes Mach’s principle. Einstein’s equations are not modified and no selection principle is applied to their solutions; Mach’s principle is realized wholly within Einstein’s general theory of relativity. The key insight is the observation that, in addition to bulk matter, one can also add boundary matter. Given a space-time, and thus the inertial frames, we can read off both boundary and bulk stress tensors, thereby relating matter and geometry. We consider some global conditions that are necessary for the space-time to be reconstructible, in principle, from bulk and boundary matter. Our framework is similar to that of the black hole membrane paradigm and, in asymptotically anti-de Sitter space-times, is consistent with holographic duality.

Modified gravitational forces in models that seek to explain cosmic acceleration without dark energy typically predict deviations in the abundance of massive dark matter halos. We conduct the first, simulation calibrated, cluster abundance constraints on a modified gravity model, specifically the modified action $f(R)$ model. The local cluster abundance, when combined with geometric and high redshift data from the cosmic microwave background, supernovae, $H_0$, and baryon acoustic oscillations, improves previous constraints by nearly 4 orders of magnitude in the field amplitude. These limits correspond to a 2 order of magnitude improvement in the bounds on the range of the force modification from the several Gpc scale to the tens of Mpc scale.

We present a novel dark-energy candidate, based upon the existence and dynamics of ghost $D$-branes in a warped compactification of type IIB string theory. $Gp$-branes cancel the combined BPS sectors of the $Dp$-branes, while they preserve the same supersymmetries. We show that this scenario can naturally lead to either quintessence or phantomlike behaviors, depending on the form of the involved potentials and brane tension. As a specific example we investigate the static, dark-energy dominated solution subclass.

We report the observation of the bottom, doubly-strange baryon ${\Omega }_b^{-}$ through the decay chain ${\Omega }_b^{-}\to J/\psi {\Omega }^{-}$, where $J/\psi \to {\mu }^{+}{\mu }^{-}$, ${\Omega }^{-}\to \Lambda K^{-}$, and $\Lambda \to p{\pi }^{-}$, using $4.2{\mathrm{fb}}^{-1}$ of data from $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$, and recorded with the Collider Detector at Fermilab. A signal is observed whose probability of arising from a background fluctuation is $4.0\times {10}^{-8}$, or 5.5 Gaussian standard deviations. The ${\Omega }_b^{-}$ mass is measured to be $6054.4\pm 6.8(\mathrm{stat})\pm 0.9(\mathrm{syst})\mathrm{MeV}/c^2$. The lifetime of the ${\Omega }_b^{-}$ baryon is measured to be ${1.13}_{-0.40}^{+0.53}(\mathrm{stat})\pm 0.02(\mathrm{syst})\mathrm{ps}$. In addition, for the ${\Xi }_b^{-}$ baryon we measure a mass of $5790.9\pm 2.6(\mathrm{stat})\pm 0.8(\mathrm{syst})\mathrm{MeV}/c^2$ and a lifetime of ${1.56}_{-0.25}^{+0.27}(\mathrm{stat})\pm 0.02(\mathrm{syst})\mathrm{ps}$. Under the assumption that the ${\Xi }_b^{-}$ and ${\Omega }_b^{-}$ are produced with similar kinematic distributions to the ${\Lambda }_b^0$ baryon, we find $\frac{\sigma ({\Xi }_b^{-})\mathcal{B}({\Xi }_b^{-}\to J/\psi {\Xi }^{-})}{\sigma ({\Lambda }_b^0)\mathcal{B}({\Lambda }_b^0\to J/\psi \Lambda )}={0.167}_{-0.025}^{+0.037}(\mathrm{stat})\pm 0.012(\mathrm{syst})$ and $\frac{\sigma ({\Omega }_b^{-})\mathcal{B}({\Omega }_b^{-}\to J/\psi {\Omega }^{-})}{\sigma ({\Lambda }_b^0)\mathcal{B}({\Lambda }_b^0\to J/\psi \Lambda )}={0.045}_{-0.012}^{+0.017}(\mathrm{stat})\pm 0.004(\mathrm{syst})$ for baryons produced with transverse momentum in the range of $6–20\mathrm{GeV}/c$.

We study the phases and fixed-point structure of two-dimensional supersymmetric Wess-Zumino models with one supercharge. Our work is based on the functional renormalization group (RG) formulated in terms of a manifestly off-shell supersymmetric flow equation for the effective action. Within the derivative expansion, we solve the flow of the superpotential also including the anomalous dimension of the superfield. The models exhibit a surprisingly rich fixed-point structure with a discrete number of fixed-point superpotentials. Each fixed-point superpotential is characterized by its number of nodes and by the number of RG-relevant directions. In limiting cases, we find periodic superpotentials and potentials which confine the fields to a compact target space. The maximally IR-attractive fixed point has one relevant direction, the tuning of which distinguishes between supersymmetric and broken phases. For the Wess-Zumino model defined near the Gaussian fixed point, we determine the phase diagram and compute the corresponding ground-state masses.

We perform next-to-leading order calculations of the single-diffractive and nondiffractive cross sections for dijet production in proton-antiproton collisions at the Tevatron. By comparing their ratio to the data published by the CDF collaboration for two different center-of-mass energies, we deduce the rapidity-gap survival probability as a function of the momentum fraction of the parton in the antiproton. Assuming Regge factorization, this probability can be interpreted as a suppression factor for the diffractive structure function measured in deep-inelastic scattering at HERA. In contrast to the observations for photoproduction, the suppression factor in proton-antiproton collisions depends on the momentum fraction of the parton in the Pomeron even at next-to-leading order.

We study the semileptonic transitions $B_c\to {\eta }_c,J/\Psi ,D,D^{*},B,B^{*},B_s,B_s^{*}$ in the leading order in the framework of a relativistic independent quark model based on a confining potential in the equally mixed scalar-vector harmonic form. We compute relevant weak form factors as overlap integrals of the meson-wave functions obtained in the relativistic independent quark model in the whole accessible kinematical range. We predict that the semileptonic transitions of the $B_c$ meson are mostly dominated by two Cabibbo-Kobayashi-Maskawa (CKM)-favored modes, $B_c\to B_s(B_s^{\star })e\nu$, contributing about 77% of the total decay width, and its decays to vector meson final states take place in the predominantly transverse mode. Our predicted values for the total decay rates, branching ratios, polarization ratios, the forward-backward asymmetry factor, etc., are broadly in agreement with other model predictions.

Using $e^{+}{e}^{-}$ collision data taken with the CLEO-c detector at the Cornell Electron Storage Ring, we have investigated the direct photon spectrum in the decay $\psi (2\mathrm{S})\to \gamma gg$. We determine the ratio of the inclusive direct photon decay rate to that of the dominant three-gluon decay rate $\psi (2\mathrm{S})\to ggg$ ($R_{\gamma }\equiv \Gamma (\gamma gg)/\Gamma (ggg)$) to be $R_{\gamma }(z_{\gamma }>0.4)=0.070\pm 0.002\pm 0.019\pm 0.011$, with $z_{\gamma }$ defined as the scaled photon energy relative to the beam energy. The errors shown are statistical, systematic, and that due to the uncertainty in the input branching fractions used to extract the ratio, respectively.

We consider the small deformation of the pointlike Wilson loop in the 3-dimensional $\mathcal{N}=6$ superconformal Chern-Simons theory. By Taylor expansion of the pointlike Wilson loop in powers of the loop variables, we obtain the BPS operators that correspond to the excited string states of the dual IIA string theory on the $pp$ wave background. The BPS conditions of the Wilson loop constrain both the loop variables and the forms of the operators obtained in the Taylor expansion.

We use the Hamiltonian formalism of quantum field theory and the variational basis-state method to derive relativistic three-body wave equations for scalar particles interacting via a massive or massless mediating scalar field (the scalar Yukawa model). A variational trial state comprised of three and five Fock-space states is used to derive coupled wave equations for a relativistic three- (and five-) body system. Approximate variational three-body ground-state solutions of the relativistic equations are obtained for various strengths of coupling, for both massive and massless mediating fields. The results show that the inclusion of virtual pairs has a large effect on the three-body binding energy at strong coupling.

We give a procedure for deriving certain bulk $S$-matrix elements from corresponding boundary correlators. These are computed in the plane-wave limit, via an explicit construction of certain boundary sources that give bulk wave packets. A critical role is played by a specific singular behavior of the Lorentzian boundary correlators. It is shown in examples how correlators derived from the bulk supergravity exhibit the appropriate singular structure, and reproduce the corresponding $S$-matrix elements. This construction thus provides a nontrivial test for whether a given boundary conformal field theory can reproduce bulk physics, and where it does, supplies a prescription to extract bulk $S$-matrix elements in the plane-wave limit.

We calculate the Casimir energy for scalar fields in interaction with finite-width mirrors, described by nonlocal interaction terms. These terms, which include quantum effects due to the matter fields inside the mirrors, are approximated by means of a local expansion procedure. As a result of this expansion, an effective theory for the vacuum field emerges, which can be written in terms of generalized $\delta$ potentials. We compute explicitly the Casimir energy for these potentials and show that, for some particular cases, it is possible to reinterpret them as imposing imperfect Dirichlet boundary conditions.