Possible anomalous single productions of the fourth standard model generation up and down type quarks at CERN Large Hadron Collider are studied. Namely, $pp\to u_4(d_4)X$ with subsequent $u_4\to b{W}^{+}$ process followed by the leptonic decay of the $W$ boson and $d_4\to b\gamma$ (and its H.c.) decay channel are considered. Signatures of these processes and corresponding standard model backgrounds are discussed in detail. Discovery limits for the quark mass and achievable values of the anomalous coupling strength are determined.

The vacuum of Yang-Mills theory contains singular stringlike objects identified with center (magnetic) vortices. Percolation of magnetic vortices is known to be responsible for the color confinement in the low-temperature phase of the theory. In our work, we study properties of the vortices at finite temperature using lattice simulations of $SU(2)$ gauge theory. We show that magnetic vortices provide a numerically large contribution to thermodynamic quantities of the gluon plasma in Yang-Mills theory. In particular, we observe that in the deconfinement phase at temperatures $T_c<T\lesssim 3T_c$ the magnetic component of the gluon plasma produces a negative (ghostlike) contribution to the anomaly of the energy-momentum tensor. In the confinement phase, the vortex contribution is positive. The thermodynamical significance of the magnetic objects allows us to suggest that the quark-gluon plasma may contain a developed network of magnetic flux tubes. The existence of the vortex network may lead to observable effects in the quark-gluon plasma because the chromomagnetic field of the vortices should scatter and drag quarks.

We present the Curci-Ferrari model on the lattice. In the massless case the topological interpretation of this model with its double Becchi-Rouet-Stora-Tyutin (BRST) symmetry relates to the Neuberger $0/0$ problem which we extend to include the ghost/antighost symmetric formulation of the nonlinear-covariant Curci-Ferrari gauges on the lattice. The introduction of a Curci-Ferrari mass term, however, serves to regulate the $0/0$ indeterminate form of physical observables observed by Neuberger. While such a mass $m$ decontracts the double BRST/anti-BRST algebra, which is well known to result in a loss of unitarity, observables can be meaningfully defined in the limit $m\to 0$ via l’Hospital’s rule. At finite $m$, the topological nature of the partition function used as the gauge-fixing device seems lost. We discuss the gauge parameter $\xi$ and mass $m$ dependence of the model and show how both cancel when $m\equiv m(\xi )$ is appropriately adjusted with $\xi$.

I derive the space-time distribution of energy and momentum deposited by a fast parton traversing a perturbative quark-gluon plasma by considering the fast parton as the source of an external color field interacting with the medium. I include the medium’s response to screen the fast parton’s color field by incorporating dielectric functions and compare to the unscreened result.

Spherically symmetric expansion-free distributions are systematically studied. The entire set of field equations and junction conditions are presented for a general distribution of dissipative anisotropic fluid (principal stresses unequal), and the expansion-free condition is integrated. In order to understand the physical meaning of expansion-free motion, two different definitions for the radial velocity of a fluid element are discussed. It is shown that the appearance of a cavity is inevitable in the expansion-free evolution. The nondissipative case is considered in detail, and the Skripkin model is recovered.

Although cosmic microwave background anisotropy data alone cannot constrain simultaneously the spatial curvature and the equation of state of dark energy, CMB data provide a valuable addition to other experimental results. However computing a full CMB power spectrum with a Boltzmann code is quite slow; for instance if we want to work with many dark energy and/or modified gravity models, or would like to optimize experiments where many different configurations need to be tested, it is possible to adopt a quicker and more efficient approach. In this paper we consider the compression of the projected Planck cosmic microwave background data into four parameters, $R$ (scaled distance to last scattering surface), $l_a$ (angular scale of sound horizon at last scattering), ${\Omega }_b{h}^2$ (baryon density fraction) and $n_s$ (powerlaw index of primordial matter power spectrum), all of which can be computed quickly. We show that, although this compression loses information compared to the full likelihood, such information loss becomes negligible when more data is added. We also demonstrate that the method can be used for canonical scalar-field dark energy independently of the parametrization of the equation of state, and discuss how this method should be used for other kinds of dark energy models.

Dynamic dark-energy (DDE) models are often designed to solve the cosmic coincidence (why, just now, is the dark-energy density ${\rho }_{\mathrm{de}}$ the same order of magnitude as the matter density ${\rho }_m$?) by guaranteeing ${\rho }_{\mathrm{de}}\sim {\rho }_m$ for significant fractions of the age of the Universe. However, such behavior is neither sufficient nor necessary to solve the coincidence problem. Cosmological processes constrain the epochs during which observers can exist. Therefore, what must be shown is that a significant fraction of observers see ${\rho }_{\mathrm{de}}\sim {\rho }_m$. Precisely when, and for how long, must a DDE model have ${\rho }_{\mathrm{de}}\sim {\rho }_m$ in order to solve the coincidence? We explore the coincidence problem in dynamic dark-energy models using the temporal distribution of terrestrial-planet-bound observers. We find that any realistic DDE model which can be parametrized as $w=w_0+w_a(1-a)$ over a few e-folds has ${\rho }_{\mathrm{de}}\sim {\rho }_m$ for a significant fraction of observers in the Universe. This demotivates DDE models specifically designed to solve the coincidence using long or repeated periods of ${\rho }_{\mathrm{de}}\sim {\rho }_m$.

We study the time variation of fundamental constants in the early Universe. Using data from primordial light nuclei abundances, cosmic microwave background, and the 2dFGRS power spectrum, we put constraints on the time variation of the fine structure constant $\alpha$ and the Higgs vacuum expectation value $⟨v⟩$ without assuming any theoretical framework. A variation in $⟨v⟩$ leads to a variation in the electron mass, among other effects. Along the same line, we study the variation of $\alpha$ and the electron mass $m_e$. In a purely phenomenological fashion, we derive a relationship between both variations.

Based on recent results obtained by the Pierre Auger Observatory (PAO), it has been hypothesized that Centaurus A (Cen A) is a source of ultrahigh-energy cosmic rays (UHECRs) and associated neutrinos. We point out that the diffuse neutrino flux may be used to constrain the source model if one assumes that the ratio between the UHECR and neutrino fluxes outputted by Cen A is representative for other sources. Under this assumption we investigate the relation between the neutrino flux from Cen A and the diffuse neutrino flux. Assuming furthermore that Cen A is the source of two UHECR events observed by PAO, we estimate the all-sky diffuse neutrino flux to be $\sim 200–5000$ times larger than the neutrino flux from Cen A. As a result, the diffuse neutrino fluxes associated with some of the recently proposed models of UHECR-related neutrino production in Cen A are above existing limits. Regardless of the underlying source model, our results indicate that the detection of neutrinos from Cen A without the accompanying diffuse flux would mean that Cen A is an exceptionally efficient neutrino source.

We develop the formalism for determining the quasinormal modes of general relativistic multifluid compact stars in such a way that the impact of superfluid gap data can be assessed. Our results represent the first attempt to study true multilayer dynamics, an important step towards considering realistic superfluid/superconducting compact stars. We combine a relativistic model for entrainment with model equations of state that explicitly incorporate the symmetry energy. Our analysis emphasizes the many different parameters that are required for this kind of modeling, and the fact that standard tabulated equations of state are grossly incomplete in this respect. To make progress, future equations of state need to provide the energy density as a function of the various nucleon number densities, the temperature (i.e. entropy), and the entrainment among the various components.

Motivated by models of holographic technicolor, we discuss a four-site deconstructed Higgsless model with nontrivial wave function mixing. We compute the spectrum of the model, the electroweak triple gauge-boson vertices, and, for brane-localized fermions, the electroweak parameters to $\mathcal{O}(M_W^2/M_{\rho }^2)$. We discuss the conditions under which $\alpha S$ vanishes (even for brane-localized fermions) and the (distinct but overlapping) conditions under which the phenomenologically interesting decay $a_1\to W\gamma$ is nonzero and suppressed by only one power of ($M_W/M_{\rho }$).

In the littlest Higgs model with $T$-parity new flavor-changing interactions between mirror fermions and the standard model (SM) fermions can induce various flavor-changing neutral-current decays for $B$-mesons, the $Z$-boson, and the Higgs boson. Since all these decays induced in the littlest Higgs with $T$-parity model are correlated, in this work we perform a collective study for these decays, namely, the $Z$-boson decay $Z\to b\overline{s}$, the Higgs-boson decay $h\to b\overline{s}$, and the $B$-meson decays $B\to X_s\gamma$, $B_s\to {\mu }^{+}{\mu }^{-}$, and $B\to X_s{\mu }^{+}{\mu }^{-}$. We find that under the current experimental constraints from the $B$-decays, the branching ratios of both $Z\to b\overline{s}$ and $h\to b\overline{s}$ can still deviate from the SM predictions significantly. In the parameter space allowed by the $B$-decays, the branching ratio of $Z\to b\overline{s}$ can be enhanced up to ${10}^{-7}$ (about one order above the SM prediction) while $h\to b\overline{s}$ can be much suppressed relative to the SM prediction (about one order below the SM prediction).

Higgs boson decays in flexible brane world models with stable, massive gravi-vectors are considered. Such vectors couple bilinearly to the standard model fields through either the standard model energy-momentum tensor, the weak hypercharge field strength, or the Higgs scalar. The role of the coupling involving the extrinsic curvature is highlighted. It is found that within the presently allowed parameter space, the decay rate of the Higgs into two gravi-vectors (which would appear as an invisible Higgs decay) can be comparable to the rate for any of the standard model decay modes.

This is a follow-up to our earlier work on the energies and radial distributions of heavy-light mesons. The heavy quark is taken to be static (infinitely heavy) and the light quark has a mass about that of the strange quark. We now concentrate on the energies of the excited states with higher angular momentum and with a radial node. A new improvement is the use of hypercubic blocking in the time direction. The calculation is carried out with dynamical fermions on a ${16}^3\times 32$ lattice with a lattice spacing $a\approx 0.1\mathrm{fm}$ generated using a nonperturbatively improved clover action. In nature the closest equivalent of this heavy-light system is the $B_s$ meson, which allows us to compare our lattice calculations to experimental results (where available) or to give a prediction for where the excited states, particularly $P$-wave states, should lie. We pay special attention to the spin-orbit splitting, to see which one of the states (for a given angular momentum $L$) has the lower energy. An attempt is made to understand these results in terms of the Dirac equation.

We present an exploratory study of gaugino-pair production in polarized and unpolarized hadron collisions, focusing on the correlation of beam polarization and gaugino/Higgsino mixing in the general minimal supersymmetric standard model. Helicity-dependent cross sections induced by neutral and charged electroweak currents and squark exchanges are computed analytically in terms of generalized charges, defined similarly for chargino-pair, neutralino-chargino associated, and neutralino-pair production. Our results confirm and extend those obtained previously for negligible Yukawa couplings and nonmixing squarks. Assuming that the lightest chargino mass is known, we show numerically that measurements of the longitudinal single-spin asymmetry at the existing polarized $pp$ collider RHIC and at possible polarization upgrades of the Tevatron or the LHC would allow for a determination of the gaugino/Higgsino fractions of charginos and neutralinos. The theoretical uncertainty coming from factorization scale and squark mass variations and the expected experimental error on the lightest chargino mass is generally smaller than the one induced by the polarized parton densities, so that more information on the latter would considerably improve on the analysis.

We calculate the pion-pole term of the light-by-light contribution to the $g-2$ of the muon in the framework of an effective chiral quark model with instantonlike nonlocal quark–quark interaction. The full kinematic dependence of the pion-photon transition form factors is taken into account. The dependence of form factors on the pion virtuality decreases the result by about 15% in comparison to the calculation where this dependence is neglected. Further, it is demonstrated that the QCD constraints suggested by Melnikov and Vainshtein are satisfied within the model. The corresponding contributions originate from the box diagram as well from the pion-pole term. Our chiral nonlocal model result for the pion-pole light-by-light contribution to $(g-2)/2$ of the muon is $(6.3–6.7)\times {10}^{-10}$, which is in the ball park of other effective-model calculations.

We present a measurement of the shapes of $b$-jets using $300{\mathrm{pb}}^{-1}$ of data obtained with the upgraded Collider Detector at Fermilab (CDF II) in $p\overline{p}$ collisions at center-of-mass energy $\sqrt{s}=1.96\mathrm{TeV}$. This measurement covers a wide transverse momentum range, from 52 to $300\mathrm{GeV}/c$. Samples of heavy-flavor enhanced jets together with inclusive jets are used to extract the average shapes of $b$-jets. The $b$-jets are expected to be broader than inclusive jets. Moreover, $b$-jets containing a single $b$-quark are expected to be narrower than those containing a $b\overline{b}$ pair from gluon splitting. The measured $b$-jet shapes are found to be significantly broader than expected from the pythia and herwig Monte Carlo simulations. This effect may arise from an underestimation of the fraction of $b$-jets originating from gluon splitting in these simulations. The jet shape distributions provided in this paper could be compared to any full Monte Carlo simulation and could be used to further constrain the various parameters.

We study an extension of the minimal supersymmetric standard model by an anomalous Abelian vector multiplet and a Stückelberg multiplet. The anomalies are cancelled by the Green-Schwarz mechanism and the addition of Chern-Simons terms. The advantage of this choice over the standard one is that it allows for arbitrary values of the quantum numbers of the extra $U(1)$. As a first step toward the study of hadron annihilations producing four leptons in the final state (a clean signal which might be studied at LHC), we then compute the decays $Z^{\prime }\to Z_0\gamma$ and $Z^{\prime }\to Z_0{Z}_0$. We find that the largest values of the decay rate are $\sim {10}^{-4}\mathrm{GeV}$, while the expected number of events per year at LHC is at most of the order of 10.

The precise analog of the $\theta$-quantization ambiguity of Yang-Mills theory exists for the real $SU(2)$ connection formulation of general relativity. As in the former case $\theta$ labels representations of large gauge transformations, which are superselection sectors in loop quantum gravity. We show that unless $\theta =0$, the (kinematical) geometric operators such as area and volume are not well defined on spin network states. More precisely the intersection of their domain with the dense set $Cyl$ in the kinematical Hilbert space $\mathcal{H}$ of loop quantum gravity is empty. The absence of a well-defined notion of area operator acting on spin network states seems at first in conflict with the expected finite black hole entropy. However, we show that the black hole (isolated) horizon area—which in contrast to kinematical area is a (Dirac) physical observable—is indeed well defined, and quantized so that the black hole entropy is proportional to the area. The effect of $\theta$ is negligible in the semiclassical limit where proportionality to area holds.

The photon-to-pion transition form factor is investigated using the form of the renormalon-based twist-four pion distribution amplitude (DA) in the framework of the light-cone local-duality QCD sum rule, which, with suitable parameters, is insensitive to the higher-order Gegenbauer coefficients. With a careful determination for the insertion parameters so that the contribution from the higher-order Gegenbauer expansions is suppressed, the best-fit central values of the first two nontrivial Gegenbauer coefficients of the pion distribution amplitude are extracted out from the CLEO data to be $a_2(1{\mathrm{GeV}}^2)=0.145\pm 0.055$ and $a_4(1{\mathrm{GeV}}^2)=-(0.125\pm 0.085)$, respectively. The rescaled photon-to-pion transition form factor with our best-fit parameters is consistent very well with both the CELLO data and the prediction of the interpolation formula in all the experimental accessible region of the momentum transfer. The shape of the pion distribution amplitude based on the two-parameter model favors the camel-like type, where the near-end-point values are suppressed more than the asymptotic DA, and satisfies the midpoint constraint from light-cone sum rules approximately.