We study the phenomenology of a $Z^{\prime }$-boson field coupled to hypercharge. The $Z^{\prime }$ propagator has a nontrivial Källén-Lehmann spectral density due to the mixing with a higher-dimensional inert vector field. As a consequence detection possibilities at hadron colliders are reduced. We determine the range of parameters where this field can be studied at the Tevatron and the LHC through its production cross section via the Drell-Yan mechanism.

Cross sections of the processes of production of neutral pions and pairs of charged fermions and bosons in peripheral interaction of leptons and photons are calculated in the main logarithmic approximation. We investigate the phase volumes and differential cross sections. The differential cross sections of production of a few neutral pions and a few pairs are written down explicitly. Considering the academic problem of summation over a number of pairs for massless particles we reproduce the known results obtained in the 1970s. The possibility of constructing the generator for Monte Carlo modeling of these processes based on these results is discussed.

The deficit observed in the Gallium radioactive source experiments is interpreted as a possible indication of the disappearance of electron neutrinos. In the effective framework of two-neutrino mixing we obtain ${sin}^{2}2\vartheta \gtrsim 0.03$ and $\Delta m^2\gtrsim 0.1{\mathrm{eV}}^2$. The compatibility of this result with the data of the Bugey and Chooz reactor short-baseline antineutrino disappearance experiments is studied. It is found that the Bugey data present a hint of neutrino oscillations with $0.02\lesssim {sin}^{2}2\vartheta \lesssim 0.08$ and $\Delta m^2\approx 1.8{\mathrm{eV}}^2$, which is compatible with the Gallium allowed region of the mixing parameters. This hint persists in the combined analyses of Bugey and Chooz data, of Gallium and Bugey data, and of Gallium, Bugey, and Chooz data.

We revisit here the recent proposal for overspinning a nearly extreme black hole by means of a quantum tunneling process. We show that electrically neutral massless fermions evade possible backreaction effects related to superradiance, confirming the view that it would be indeed possible to form a naked singularity due to quantum effects.

The ${}^{3}P_0$ model, in which $q\overline{q}$ pair production is the dominant mechanism, is extensively applied to both light and heavy meson decay and stands as one of the most successful strong decay models. The pair production can be obtained from the nonrelativistic limit of a microscopic interaction Hamiltonian involving Dirac quark fields. The evaluation of the decay amplitude can be performed by a diagrammatic technique for drawing quark lines. In this paper we use an alternative approach which consists of a mapping technique, the Fock-Tani formalism, in order to obtain an effective Hamiltonian starting from the same microscopic interaction. An additional effect is manifested in this formalism associated to the extended nature of mesons: bound-state corrections. A corrected ${}^{3}P_0$ is obtained and applied, as an example, to $b_1\to \omega \pi$ and $a_1\to \rho \pi$ decays.

A good agreement between a flux tube-based quark model of light baryons (strange and nonstrange) and the $1/N_c$ expansion mass formula has been found in previous studies. In the present work a larger connection is established between the quark model and the $1/N_c$ and $1/m_Q$ expansion method by extending the previous procedure to baryons made of one heavy and two light quarks. The compatibility between both approaches is shown to hold in this sector too.

We consider the minimal supersymmetric extension of the standard model (MSSM) with varying amounts of nonuniversality in the soft supersymmetry-breaking contributions to the Higgs scalar masses. In addition to the constrained MSSM (CMSSM) in which these are universal with the soft supersymmetry-breaking contributions to the squark and slepton masses at the input GUT scale, we consider scenarios in which both the Higgs scalar masses are nonuniversal by the same amount (NUHM1), and scenarios in which they are independently nonuniversal (NUHM2). We show how the NUHM1 scenarios generalize the $(m_{1/2},m_0)$ planes of the CMSSM by allowing either $\mu$ or $m_A$ to take different (fixed) values and we also show how the NUHM1 scenarios are embedded as special cases of the more general NUHM2 scenarios. Generalizing from the CMSSM, we find regions of the NUHM1 parameter space that are excluded because the lightest supersymmetric particle (LSP) is a selectron. We also find new regions where the neutralino relic density falls within the range preferred by astrophysical and cosmological measurements, thanks to rapid annihilation through direct-channel Higgs poles, or coannihilation with selectrons, or because the LSP composition crosses over from being mainly bino to mainly Higgsino. Generalizing further to the NUHM2, we find regions of its parameter space where a sneutrino is the LSP, and others where neutralino coannihilation with sneutrinos is important for the relic density. In both the NUHM1 and the NUHM2, there are slivers of parameter space where the LHC has fewer prospects for discovering sparticles than in the CMSSM, because either $m_{1/2}$ and/or $m_0$ may be considerably larger than in the CMSSM.

We show that when the supersymmetric SU(5) model is extended to explain small neutrino masses by the type III seesaw mechanism, the new $\mathbf{24}$-dimensional fields needed for the purpose can act as messengers for transmitting SUSY breaking from a hidden sector to the visible sector. For the three $\mathbf{24}$s case, the constraints of grand unification and suppressed lepton flavor violation restrict the seesaw scale in this case to be in the narrow range of ${10}^{12}–{10}^{13}\mathrm{GeV}$. The model predicts (i) a stable lightest superpartner gravitino with mass in the range of 1–10 MeV which can be a cold dark matter of the universe; (ii) a stau next to lightest superpartner, which is detectable at the LHC; (iii) a lower bound on the branching ratio $\mathrm{BR}(\mu \to e\gamma )$ larger than ${10}^{-14}$ testable by the ongoing Muegamma (MEG) experiment as well as a characteristic particle spectrum different from other SUSY breaking scenarios. We also discuss the case with two $\mathbf{24}$ fields, which is the minimal case that can explain neutrino oscillation data.

We estimate the potential energy for a system of three static gluons in lattice QCD. This is relevant for the different models of three-body glueballs that have been proposed in the literature, either for gluons with a constituent mass, or for massless ones. A Wilson loop adequate to the static hybrid three-body system is developed. We study different spacial geometries, to compare the starfish model with the triangle model, for the three-gluon potential. We also study two different color structures, symmetric and antisymmetric, and compare the respective static potentials. A first simulation is performed in a ${24}^3\times 48$ periodic Lattice, with $\beta =6.2$ and $a\sim 0.072\mathrm{fm}$.

We calculate the next-to-leading order (NLO) QCD corrections to $Zb\overline{b}$ production in hadronic collisions including full bottom-quark mass effects. We present results for the total cross section and the invariant mass distribution of the bottom-quark jet pair at the Fermilab Tevatron $p\overline{p}$ collider. We perform a detailed comparison with a calculation that considers massless bottom quarks, as implemented in the Monte Carlo program MCFM. We find that neglecting bottom-quark mass effects overestimates the total NLO QCD cross section for $Zb\overline{b}$ production at the Tevatron by about 7%, independent of the choice of the renormalization and factorization scales. Moreover, bottom-quark mass effects can impact the shape of the bottom-quark pair invariant mass distribution, in particular, in the low invariant mass region.

For a model with a fourth family of quarks, new sources of flavor changing neutral currents are identified by confronting the unitary $4\times 4$ quark mixing matrix with the experimental measured values of the familiar $3\times 3$ quark mixing matrix. By imposing as experimental constraints the known bounds for the flavor changing neutral currents, the largest mixing of the known quarks with the fourth family ones is established. The predictions are: a value for $|V_{tb}|$ significantly different from unity, large rates for rare top decays as $t\to c\gamma$ and $t\to cZ$, the last one reachable at the Large Hadron Collider, and large rates for rare strange decays $s\to d\gamma$ and $s\to dg$, where $g$ stands for the gluon field, both processes reachable at the existing B factories.

It is shown that LHC data can allow one to decode the mechanism by which dark matter is generated in the early universe in supersymmetric theories. We focus on two of the major mechanisms for such generation of dark matter, which are known to be the stau coannihilation (stau co), where the neutralino is typically bino like and annihilation on the hyperbolic branch (HB), where the neutralino has a significant Higgsino component. An investigation of how one may discriminate between the stau-co region and the HB region using LHC data is given for the mSUGRA model. The analysis utilizes several signatures including multi leptons, hadronic jets, $b$ tagging, and missing transverse momentum. A study of the supersymmetry signatures reveals several correlated smoking gun signals allowing a clear discrimination between the stau-co and the HB regions where dark matter in the early universe can originate.

We calculate the bulk viscosity due to nonequilibrium weak processes in superfluid nucleon-hyperon matter of neutron stars. For that, the dissipative relativistic hydrodynamics, formulated eariler [M. E. Gusakov, Phys. Rev. D 76, 083001 (2007).] for superfluid mixtures, is extended to the case when both nucleons and hyperons are superfluid. It is demonstrated that in the most general case (when neutrons, protons, $\Lambda$, and ${\Sigma }^{-}$ hyperons are superfluid), nonequilibrium weak processes generate 16 bulk viscosity coefficients, with only three of them being independent. In addition, we correct an inaccuracy in a widely used formula for the bulk viscosity of nonsuperfluid nucleon-hyperon matter.

We study the neutralino relic density in the minimal supersymmetric standard model with natural light Higgs sector in which all Higgs masses, the supersymmetry (SUSY) breaking parameters, and the Higgsino mass parameter $\mu$ are of order the weak scale. To realize this situation we adopt nonuniversal Higgs masses at the grand unified scale. We show that in some parameter space in which the SUSY breaking parameters are comparatively small, not only the constraint from the observed relic density of dark matter but also the LEP Higgs bound and the constraint from the $b\to s\gamma$ process are satisfied. In most of the parameter space, the neutralino relic density becomes smaller than the observed relic density in contrast with the results in the constrained minimal SUSY standard model (CMSSM). The reason is that the neutralino coannihilation processes to Higgs bosons open even if the gaugino mass is small and the cross sections become large due to the small dimensionful parameters. Especially the small $\mu$ parameter and the light $CP$-odd Higgs, which are difficult to be realized in the CMSSM, are essential for the result.

We investigate the signatures of Fermi liquid formation in the $\mathcal{N}=4$ super Yang-Mills theory coupled to fundamental hypermultiplet at nonvanishing chemical potential for the global $U(1)$ vector symmetry. At strong ’t Hooft coupling the system can be analyzed in terms of the D7-brane dynamics in the ${\mathrm{AdS}}_5\times S^5$ background. The phases with vanishing and finite charge density are separated at zero temperature by a quantum phase transition. In the case of vanishing hypermultiplet mass, Karch, Son, and Starinets discovered a gapless excitation whose speed equals the speed of sound. We find that this zero sound mode persists to all values of the hypermultiplet mass, and its speed vanishes at the point of phase transition. The value of critical exponent and the ratio of the velocities of zero and first sounds are consistent with the predictions of Landau Fermi liquid theory at strong coupling.

We study the gravitational corrections to the Maxwell, Dirac, and Klein-Gordon theories in the large extra dimension model in which the gravitons propagate in the $(4+n)$-dimensional bulk, while the gauge and matter fields are confined to the four-dimensional world. The corrections to the two-point Green’s functions of the gauge and matter fields from the exchanges of virtual Kaluza-Klein gravitons are calculated in the gauge independent background field method. In the framework of effective field theory, we show that the modified one-loop renormalizable Lagrangian due to quantum gravitational effects contains a TeV scale Lee-Wick partner of every gauge and matter field as extra degrees of freedom in the theory. Thus the large extra dimension model of gravity provides a natural mechanism for the emergence of these exotic particles which were recently used to construct an extension of the standard model.

We numerically evaluate the Casimir interaction energy for configurations involving two perfectly conducting eccentric cylinders and a cylinder in front of a plane. We consider in detail several special cases. For quasiconcentric cylinders, we analyze the convergence of a perturbative evaluation based on sparse matrices. For concentric cylinders, we obtain analytically the corrections to the proximity force approximation up to second order, and we present an improved numerical procedure to evaluate the interaction energy at very small distances. Finally, we consider the configuration of a cylinder in front of a plane. We first show numerically that, in the appropriate limit, the Casimir energy for this configuration can be obtained from that of two eccentric cylinders. Then we compute the interaction energy at small distances, and compare the numerical results with the analytic predictions for the first order corrections to the proximity force approximation.

We present an exact numerical computation of the one-loop correction of the string tension for the Nielsen-Olesen vortex in the Abelian Higgs model. The computation proceeds via the computation of the Euclidean Green’s function for the gauge, Higgs, and Faddeev-Popov fields using mode functions, and taking the appropriate trace. Renormalization is an essential part of this computation. It is done by removing leading order contributions from the numerical results so as to make these finite, and to add the divergent parts back, after suitable regularization and renormalization. We encounter and solve some problems which are specific to gauge theories and topological solutions. The corrections to the energy are found to be sizable, but still smaller than the classical energy as long as $g^2$ is smaller than unity.

We describe a general scenario where primordial non-Gaussian curvature perturbations are generated in models with extra scalar fields. The extra scalars communicate to the inflaton sector mainly through the tachyonic (waterfall) field condensing at the end of hybrid inflation. These models can yield significant non-Gaussianity of the local shape, and both signs of the bispectrum can be obtained. These models have cosmic strings and a nearly flat power spectrum, which together have been recently shown to be a good fit to WMAP data. We illustrate with a model of inflation inspired from intersecting brane models.