We compare fully differential exact results for the virtual photon correction to single hard photon bremsstrahlung obtained using independent calculations, both for $e^{+}{e}^{-}$ annihilation at high-energy colliders and for radiative return applications. The results are compared using Monte Carlo evaluations of the matrix elements as well as by direct analytical evaluation of certain critical limits. Special attention is given to the issues of numerical stability and the treatment of finite-mass corrections. It is found that agreement on the order of ${10}^{-5}$ or better is obtained over most of the range of hard photon energies, at CMS energies relevant to both high-energy collisions and radiative return experiments.

A partial wave analysis (PWA) of the ${\pi }^{-}{\pi }^{-}{\pi }^{+}$ and ${\pi }^{-}{\pi }^0{\pi }^0$ systems produced in the reaction ${\pi }^{-}p\to (3\pi {)}^{-}p$ at $18\mathrm{GeV}/c$ was carried out using an isobar model assumption. This analysis is based on 3.0 M ${\pi }^{-}{\pi }^0{\pi }^0$ events and 2.6 M ${\pi }^{-}{\pi }^{-}{\pi }^{+}$ events and shows production of the $a_1(1260)$, $a_2(1320)$, ${\pi }_2(1670)$, and $a_4(2040)$ resonances. Results of detailed studies of the stability of partial wave fits are presented. An earlier analysis of 250 K ${\pi }^{-}{\pi }^{-}{\pi }^{+}$ events from the same experiment showed possible evidence for a $J^{PC}=1^{-+}$ exotic meson with a mass of $\sim 1.6\mathrm{GeV}/c^2$ decaying into $\rho \pi$. In this analysis of a higher statistics sample of the $(3\pi {)}^{-}$ system in two charged modes we find no evidence of an exotic meson.

In this paper, an open fermionic string propagating freely and one moving in a constant antisymmetric background field are discussed. In contrast to several discussions in which boundary conditions are taken as primary Dirac constraints, we get the anti-Poisson brackets among the Fourier modes first. Then the anti-Poisson brackets among the string’s coordinates can be obtained. It is shown that due to nontrivial boundary conditions, the string’s end points are antinoncommutative. Contrary to the previous approaches in which the antinoncommutativity is obtained as the algebraic result, we find that antinoncommutativity originates dynamically.

We study the impacts of the nonuniversal $Z^{\prime }$ model, providing flavor-changing neutral current at tree level, on the branching ratios (BRs), CP asymmetries (CPAs), and polarization fractions of $B$ decays. We find that, for satisfying the current data, the new left- and right-handed couplings have to be included at the same time. The new introduced effective interactions not only could effectively explain the puzzle of small longitudinal polarization in $B\to K^{*}\varphi$ decays, but also provide a solution to the small CPA of $B^{\pm }\to {\pi }^0{K}^{\pm }$. We also find that the favorable CPA of $B^{\pm }\to {\pi }^0{K}^{\pm }$ is opposite in sign to the standard model; meanwhile, the CPA of $B_d\to {\pi }^{0}K$ has to be smaller than $-10\%$. In addition, by using the values of parameters which are constrained by $B\to \pi K$, we find that the favorable ranges of BRs, CPAs, longitudinal polarizations, and perpendicular transverse polarizations for $(B^{\pm }\to {\rho }^{\pm }{K}^{*},B_d\to {\rho }^{\mp }{K}^{*\pm })$ are $(17.1\pm 3.9,10.0\pm 2.0)\times {10}^{-6}$, $(3\pm 5,21\pm 7)\%$, $(0.66\pm 0.10,0.44\pm 0.08)$, and $(0.14\pm 0.10,0.25\pm 0.09)$, respectively.

In this paper, we calculate the branching ratios and $CP$-violating asymmetries for $B^0\to {\rho }^0{\eta }^{(\prime )}$ and $B^{+}\to {\rho }^{+}{\eta }^{(\prime )}$ decays in the perturbative QCD factorization approach. In this approach, we not only calculate the usual factorizable contributions, but also evaluate the nonfactorizable and annihilation type contributions. Besides the current-current operators, the contributions from the QCD and electroweak penguin operators are also taken into account. The theoretical predictions for the branching ratios are $Br(B^{+}\to {\rho }^{+}{\eta }^{(\prime )})\approx 9\times {10}^{-6}$ and $Br(B^0\to {\rho }^0{\eta }^{(\prime )})\approx 5\times {10}^{-8}$, which agree well with the measured values and currently available experimental upper limits. We also predict large $CP$-violating asymmetries in these decays: $A_{CP}^{\mathrm{dir}}({\rho }^{\pm }\eta )\approx -13\%$, $A_{CP}^{\mathrm{dir}}({\rho }^{\pm }{\eta }^{\prime })\approx -18\%$, $A_{CP}^{\mathrm{dir}}({\rho }^0\eta )\approx -41\%$, $A_{CP}^{\mathrm{dir}}({\rho }^0{\eta }^{\prime })\approx -27\%$, $A_{CP}^{\mathrm{mix}}({\rho }^0\eta )\approx +25\%$, and $A_{CP}^{\mathrm{mix}}({\rho }^0{\eta }^{\prime })\approx +11\%$, which can be tested by the current or future $B$ factory experiments.

Gauge invariant topological interactions, such as the $D=5$ Chern-Simons (CS) term, are required in models in extra dimensions that split anomaly free representations. The Chern-Simons term is necessary to maintain the overall anomaly cancellations of the theory, but it can have significant, observable, physical effects. The CS term locks the Kaluza-Klein (KK)-mode parity to the parity of space-time, leaving a single parity symmetry. It leads to new processes among KK modes e.g., the decay of a KK mode to a 2-body final state of KK modes. A formalism for the effective interaction among KK modes is constructed, and the decay of a KK mode to KK mode plus zero mode is analyzed as an example. We elaborate the general KK-mode current and anomaly structure of these theories. This includes a detailed study of the triangle diagrams and the associated “consistent anomalies” for Weyl spinors on the boundary branes. We also develop the non-Abelian formalism. We illustrate this by showing in a simple way how a $D=5$ Yang-Mills “quark flavor” symmetry leads to the $D=4$ chiral Lagrangian of mesons and the quantized Wess-Zumino-Witten term.

The Isolated Horizons (IH) formalism, together with a simple phenomenological model for colored black holes has been used to predict nontrivial formulas that relate the ADM mass of the solitons and hairy Black Holes of Gravity-Matter system on the one hand, and several horizon properties of the black holes in the other. In this article, the IH formalism is tested numerically for spherically symmetric solutions to an Einstein-Higgs system where hairy black holes were recently found to exist. It is shown that the mass formulas still hold and that, by appropriately extending the current model, one can account for the behavior of the horizon properties of these new solutions. An empirical formula that approximates the ADM mass of hairy solutions is put forward, and some of its properties are analyzed.

The $r$-modes of accreting neutron stars could be a detectable source of persistent gravitational waves if the bulk viscosity of the stellar matter can prevent a thermal runaway. This is possible if exotic particles such as hyperons are present in the core of the star. We compute bulk viscous damping rates and critical frequencies for $r$-modes of neutron stars containing hyperons in the framework of relativistic mean field theory. We combine the results of several previous calculations of the microphysics, include for the first time the effect of rotation, and explore the effects of various parameters on the viability of persistent gravitational wave emission. We find that persistent emission is quite robust, although it is disfavored in stars below 1.3–1.5 $M_{\odot }$ depending on the equation of state. In some cases persistent emission is compatible with temperatures as low as ${10}^7\mathrm{K}$, observed in some accreting neutron stars in quiescence.

We find exact exponentially expanding and contracting de Sitter solutions of the spatially homogeneous TeVeS cosmological equations of motion in the vacuum TeVeS model and a power law accelerated expanding solution in the presence of an additional ideal fluid with equation of state parameter $-5/3<\omega <-1$. A preliminary stability analysis shows that the expanding vacuum solution is stable, while in the ideal fluid case stability depends on model parameter values. These solutions might provide a basis for incorporating early-time inflation or late-time accelerated expansion in TeVeS cosmology.

We investigate the consequences of an imperfect dark energy fluid on the large scale structure. A phenomenological three parameter fluid description is used to study the effect of dark energy on the cosmic microwave background radiation (CMBR) and matter power spectrum. In addition to the equation of state and the sound speed, we allow a nonzero viscosity parameter for the fluid. Then anisotropic stress perturbations are generated in dark energy. In general, we find that this possibility is not excluded by the present day cosmological observations. In the simplest case when all of the three parameters are constant, we find that the observable effects of the anisotropic stress can be closely mimicked by varying the sound speed of perfect dark energy. However, now also negative values for the sound speed, as expected for adiabatic fluid model, are tolerable and in fact could explain the observed low quadrupole in the CMBR spectrum. We investigate also structure formation of imperfect fluid dark energy characterized by an evolving equation of state. In particular, we study models unifying dark energy with dark matter, such as the Chaplygin gas or the Cardassian expansion, with a shear perturbation included. This can stabilize the growth of inhomogeneities in these models, thus somewhat improving their compatibility with large scale structure observations.

We reanalyze the allowed parameters for inhomogeneous big bang nucleosynthesis in light of the WMAP constraints on the baryon-to-photon ratio $\eta$ and a recent measurement which has set the neutron lifetime to be $878.5\pm 0.7\pm 0.3\sec$. For a set baryon-to-photon ratio $\eta$ the new lifetime reduces the mass fraction of ${}^4\mathrm{He}$ by 0.0015 but does not significantly change the abundances of other isotopes. This enlarges the region of concordance between ${}^4\mathrm{He}$ and deuterium in the parameter space of $\eta$ and the IBBN distance scale $r_i$. The ${}^7\mathrm{Li}$ abundance can be brought into concordance with observed ${}^4\mathrm{He}$ and deuterium abundances by using depletion factors as high as 9.3. The WMAP constraints, however, severely limit the allowed comoving ($T=100\mathrm{GK}$) inhomogeneity distance scale to $r_i\approx (1.3–2.6)\times {10}^5\mathrm{cm}$.

We investigate the associated production of neutral Higgs boson with squark pair in the minimal supersymmetric standard model with and without explicit $CP$ violation, respectively. We show that the dominant productions in both cases are always ones of the lightest neutral Higgs boson associated with the lightest stop pair, which can reach a few pb, in the ranges of parameters allowed by constraints from the electric dipole moment experiments. In most of the parameter space, the total cross sections in the case with explicit $CP$ violation are significantly enhanced, compared with ones without explicit $CP$ violation. For some special parameters, several orders of magnitude enhancement can be obtained.

The usual universal extra dimensions scenario does not allow for single production of first level Kaluza-Klein (KK) excitations of matter due to the KK number conservation. However, if the matter fields are localized on a fat rane embedded in a higher dimensional space, matter-gravitation interactions violate KK number, and the production of single KK excitations becomes possible. In this paper we analyze the production of a single KK matter excitation together with a graviton in the final state, and study the potential for discovery at the Tevatron and Large Hadron Collider.

We present a new method to search for a light scalar top with $m_{{\tilde{t}}_1}\lesssim m_t$, decaying dominantly into a $c$-jet and the lightest neutralino, at the LHC. The principal idea is to exploit the Majorana nature of the gluino, leading to same-sign top quarks in events of gluino-pair production followed by gluino decays into top and stop. The resulting signature is 2 $b$-jets plus 2 same-sign leptons plus additional jets and missing energy. We perform a Monte Carlo simulation for a benchmark scenario, which is in agreement with the recent WMAP bound on the relic density of dark matter, and demonstrate that for $m_{\tilde{g}}\lesssim 900\mathrm{GeV}$ and $m_{\tilde{q}}>m_{\tilde{g}}$ the signal can be extracted from the background. Moreover, we discuss the determination of the stop and gluino masses from the shape of invariant-mass distributions. The derivation of the shape formulas is also given.

We analyze a minimal bottom-up seesaw scenario that (i) is supersymmetric, (ii) has a local $B-L$ symmetry as part of the gauge group $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}$ to implement the seesaw mechanism, (iii) has a $B-L$ symmetry breaking that leaves $R$-parity unbroken so that there is naturally stable dark matter, and (iv) has a discrete $Z$ symmetry that excludes bilinear Higgs terms in the superpotential. We show that (i) and (iv) allow one to predict the seesaw scale for neutrino masses to be $M_R\simeq \sqrt{M_{\mathrm{SUSY}}{M}_{P\ell }}\simeq {10}^{11}\mathrm{GeV}$. We demonstrate, given the above, that the ground state is a stable minimum and is lower than possible electric charge violating minima. Furthermore, we provide expressions for the masses of the light doubly charged Higgs bosons and Higgsinos that are known to exist in the generic versions of these models. Finally, we indicate how one can get different expectation values for the MSSM Higgs doublets and therefore obtain realistic quark masses.

In our previous work [Phys. Rev. D 70, 037503 (2004)] for the $e^{+}p\to t\overline{\nu }+X$ process, we have shown that the top quark possesses a high degree of spin polarization when its spin decomposition axis is along the incoming lepton beam. In this work, the potential of $ep$ collisions to probe an anomalous $Wtb$ vertex is investigated via the polarized single top quark production process for $\mathrm{TESLA}+\mathrm{HERAp}$ energy. The effects of the top quark polarization to $Wtb$ couplings $F_{2L}$ and $F_{2R}$ are discussed. It is possible to define a polarization axis for the top quark that is more sensitive to new physics than the unpolarized case.

We extend our previous analysis of gauge and Dirac fields in the presence of a chemical potential. We consider an alternative thermal operator which relates in a simple way the Feynman graphs in QED at finite temperature and charge density to those at zero temperature but nonzero chemical potential. Several interesting features of such a factorization are discussed in the context of the thermal photon and fermion self-energies.

We study the condensation of closed-string tachyons as a time-dependent process. In particular, we study tachyons whose wave functions are either space-filling or localized in a compact space, and whose masses are small in string units; our analysis is otherwise general and does not depend on any specific model. Using world-sheet methods, we calculate the equations of motion for the coupled tachyon-dilaton system, and show that the tachyon follows geodesic motion with respect to the Zamolodchikov metric, subject to a force proportional to its beta function and friction proportional to the time derivative of the dilaton. We study the relationship between world-sheet RG flow and the solutions to our equations, finding a close relationship in the case that the spatial theory is supercritical and the dilaton has a negative time derivative.