Conformality and Gauge Coupling Unification

It has been recently proposed to embed the standard model in a conformal gauge theory to resolve the hierarchy problem, and to avoid assuming either grand unification or low-energy supersymmetry. By model building based on string-field duality we show how to maintain the successful prediction of an electroweak mixing angle with $sin^2\theta \simeq 0.231$ in conformal gauge theories with three chiral families.Comment: 8 pages LaTe

Comment on ``Majoron emitting neutrinoless double beta decay in the electroweak chiral gauge extensions''

We point out that if the majoron-like scheme is implemented within a 331 model, there must exist at least three different mass scales for the scalar vacuum expectation values in the model.Comment: 4 pages, no figures, Revtex. To be published in Physical Review

Modification of Kawai model about the mixing of the pseudoscalar mesons

The Kawai model describing the glueball-quarkonia mixing is modified. The mixing of $\eta$, $\eta^\prime$ and $\eta(1410)$ is re-investigated based on the modified Kawai model. The glueball-quarkonia content of the three states is determined from a fit to the data of the electromagnetic decays involving $\eta$, $\eta^\prime$. Some predictions about the electromagnetic decays involving $\eta(1410)$ are presented.Comment: revtex 8 page

Evaluation of the Bond-to-Concrete Properties of GFRP Rebars in Marine Environments

Increased traffic in combination with growing environmental impacts have led to the accelerated degradation of built infrastructure. In reinforced concrete structures, the corrosion of steel reinforcement is the predominant cause of deterioration. Thus, over the last years the use of glass fiber reinforced polymer (GFRP) composites as internal reinforcement bars (rebars) for concrete structures has been evaluated, and has been proved to be a viable alternative to traditional steel reinforcement mainly due to its tensile strength and non-corrosive nature. However, thus far, the GFRP rebar market is diverse and manufacturers around the world produce GFRP rebar types with different surface enhancements to improve the bond to concrete characteristics. In this study, the bond performance of three dissimilar GFRP rebar types (sand coated, helically grooved and with surface lugs) was evaluated over time in seawater environments, with a focus on the bond strength. Accordingly, specimens were exposed to seawater in circulating chambers at three different temperatures (23 °C, 40 °C and 60 °C) for multiple time periods (60 and 120 days). To evaluate the bond performance, pullout tests were conducted according to ASTM D7913. The results showed that the bond strength varied with the surface enhancement features. However, the bond strength did not vary significantly with exposure time and temperature for all three evaluated rebar types.This research was funded by the Florida Department of Transportation under the grant BDV30TW0977-18

On the Mixing of the Scalar Mesons f0(1370)f_0(1370), f0(1500)f_0(1500) and f0(1710)f_0(1710)

Based on a $3\times3$ mass matrix describing the mixing of the scalar states $f_0(1370)$, $f_0(1500)$ and $f_0(1710)$, the hadronic decays of the three states are investigated. Taking into account the two possible assumptions concerning the mass level order of the bare states $|N>=|u\bar{u}+d\bar{d}>/\sqrt{2}$, $|S>=|s\bar{s}>$ and $|G>=|gg>$ in the scalar sector, $M_G > M_S > M_N$ and $M_G > M_N > M_S$, we obtain the glueball-quarkonia content of the three states by solving the unlinear equations. Some predictions about the decays of the three states in two cases are presented, which can provide a stringent consistency check of the two assumptions.Comment: revtex 10 pages, 1 eps figur

Implications of Isospin Conservation in Λb\Lambda_b Decays and Lifetime

We consider isospin predictions for the semi-leptonic and non-leptonic decays of the $\Lambda_b$ baryon. Isospin conservation of the strong interactions constrains the possible final states in $\Lambda_b$ decays. Since the baryon hyperfine splittings depend upon light quark dynamics and do not decrease with increasing heavy quark mass, this leads in general to to phase space enhancements in $\Lambda_b$ decays relative to $B$ meson decays for the same underlying quark transitions. Consequently the $\Lambda_b$ lifetime is smaller than the $B$ lifetime. Phase space enhancements in $\Lambda_b$ decays relative to $B$ decays can be understood in terms of hyperfine interactions in the heavy quark system.Comment: Changes in abstract and introduction. To appear in Phys.Lett. B. Latex 12 pages, no figure

Decay of pseudoscalars into lepton pairs and large-Nc QCD

The counterterm combination that describes the decay of pseudoscalar mesons into charged lepton pairs at lowest order in chiral perturbation theory is considered within the framework of QCD in the limit of a large number of colours Nc. When further restricted to the lowest meson dominance approximation to large-Nc QCD, our results agree well with the available experimental data.Comment: 5 pages, 2 figure

Remarks upon the mass oscillation formulas

The standard formula for mass oscillations is often based upon the approximation $t \approx L$ and the hypotheses that neutrinos have been produced with a definite momentum $p$ or, alternatively, with definite energy $E$. This represents an inconsistent scenario and gives an unjustified reduction by a factor of two in the mass oscillation formulas. Such an ambiguity has been a matter of speculations and mistakes in discussing flavour oscillations. We present a series of results and show how the problem of the factor two in the oscillation length is not a consequence of gedanken experiments, i.e. oscillations in time. The common velocity scenario yields the maximum simplicity.Comment: 9 pages, AMS-Te

Coherent and incoherent atomic scattering: Formalism and application to pionium interacting with matter

The experimental determination of the lifetime of pionium provides a very important test on chiral perturbation theory. This quantity is determined in the DIRAC experiment at CERN. In the analysis of this experiment, the breakup probabilities of of pionium in matter are needed to high accuracy as a theoretical input. We study in detail the influence of the target electrons. They contribute through screening and incoherent effects. We use Dirac-Hartree- Fock-Slater wavefunctions in order to determine the corresponding form factors. We find that the inner-shell electrons contribute less than the weakly bound outer electrons. Furthermore, we establish a more rigorous estimate for the magnitude of the contributions form the transverse current (magnetic terms thus far neglected in the calculations).Comment: Journal of Physics B: Atomic, Molecular and Optical Physics; (accepted; 22 pages, 6 figures, 26 references) Revised version: more detailed description of DIRAC experiment; failure of simplest models for incoherent scattering demonstrated by example

The Vector Meson Form Factor Analysis in Light-Front Dynamics

We study the form factors of vector mesons using a covariant fermion field theory model in $(3+1)$ dimensions. Performing a light-front calculation in the $q^+ =0$ frame in parallel with a manifestly covariant calculation, we note the existence of a nonvanishing zero-mode contribution to the light-front current $J^+$ and find a way of avoiding the zero-mode in the form factor calculations. Upon choosing the light-front gauge (\ep^+_{h=\pm}=0) with circular polarization and with spin projection $h=\uparrow\downarrow=\pm$, only the helicity zero to zero matrix element of the plus current receives zero-mode contributions. Therefore, one can obtain the exact light-front solution of the form factors using only the valence contribution if only the helicity components, $(h'h)=(++),(+-)$, and $(+0)$, are used. We also compare our results obtained from the light-front gauge in the light-front helicity basis (i.e. $h=\pm,0$) with those obtained from the non-LF gauge in the instant form linear polarization basis (i.e. $h=x,y,z$) where the zero-mode contributions to the form factors are unavoidable.Comment: 33 pages; typo in Eq.(15) is corrected; comment on Ref.[9] is corrected; version to appear in Phys. Rev.