Quark and Lepton Masses in 5D SO(10)

We construct a five dimensional supersymmetric SO(10)$\times$D$_3$ grand unified model with an $S^1/(Z_2 \times Z^\prime_2)$ orbifold as the extra dimension. The orbifold breaks half of the supersymmetry and breaks the SO(10) gauge symmetry down to ${\rm SU(4)}_C \times {\rm SU(2)}_L \times {\rm SU(2)}_R$. The Higgs mechanism is used to break the remaining gauge symmetry the rest of the way to the Standard Model. We place matter fields variously in the bulk and on the orbifold fixed points and the resulting massless fields are mixtures between these brane and bulk fields. A chiral adjoint field in the bulk gets a U(1)$_X$ vacuum expectation value, resulting in an $X$-dependent localization of the bulk matter fields and the Standard Model Higgs field. This Higgs field localization allows us to simultaneously explain the hierarchies $m_u < m_d$ and $m_t \gg m_b$. The model uses 11 parameters to fit the 13 independent low energy observables of the quark and charged lepton Yukawa matrices. The model predicts the values of two quark mass combinations, \f{m_u}{m_c} and $m_d m_s m_b$, each of which are predicted to be approximately $1 \sigma$ above their experimental values. The remaining observables are successfully fit at the 5% level.Comment: 52 pages, published version, includes more discussion of 6D version of mode

Experimental Status of Exotic Mesons and the GlueX Experiment

One of the unanswered and most fundamental questions in physics regards the nature of the confinement mechanism of quarks and gluons in QCD. Exotic hybrid mesons manifest gluonic degrees of freedom and their spectroscopy will provide the data necessary to test assumptions in lattice QCD and the specific phenomenology leading to confinement. Within the past two decades a number of experiments have put forth tantalizing evidence for the existence of exotic hybrid mesons in the mass range below 2 GeV. This talk represents an overview of the available data and what has been learned. In looking toward the future, the GlueX experiment at Jefferson Laboratory represents a new initiative that will perform detailed spectroscopy of the light-quark meson spectrum. This experiment and its capabilities will be reviewed.Comment: 10 pages, 8 figures, 2nd Meeting of the APS Topical Group on Hadron Physics GHP06, Nashville, TN (10/22-10/24/06

Inclusive Semi-leptonic B Decays to order 1/m_b^4

We give a systematic way to compute higher orders in the 1/m_b expansion in inclusive semi-leptonic decays at tree level. We reproduce the known 1/m_b^3 terms and compute the 1/m_b^4 terms at tree level. The appearing non-perturbative parameters and the impact on the determination of V_{cb} are discussed.Comment: 23 pages, 3 figures, uses phystex.st

On the gluon content of the eta and eta' mesons

A phenomenological analysis of radiative $V\to P\gamma$ and $P\to V\gamma$ decays is performed with the purpose of determining the gluonic content of the $\eta$ and $\eta^\prime$ wave functions. Our results show that within our model there is no evidence for a gluonium contribution in the $\eta$, $Z_\eta^2=0.00\pm 0.12$, or the $\eta^\prime$, $Z_{\eta^\prime}^2=0.04\pm 0.09$. In terms of a mixing angle description this corresponds to $\phi_P=(41.4\pm 1.3)^\circ$ and $|\phi_{\eta^\prime G}|=(12\pm 13)^\circ$. In addition, the $\eta$-$\eta^\prime$ mixing angle is found to be $\phi_P=(41.5\pm 1.2)^\circ$ if we don't allow for a gluonium component.Comment: 16 pages, 3 figures, JHEP style. First part of data fitting changed, conclusions not modifie

Composition of the Pseudoscalar Eta and Eta' Mesons

The composition of the eta and eta' mesons has long been a source of discussion and is of current interest with new experimental results appearing. We investigate what can be learnt from a number of different processes: V to P gamma and P to V gamma (V and P are light vector and pseudoscalar mesons respectively), P to gamma gamma, J/psi,psi' to P gamma, J/psi,psi' to P V, and chi_{c0,2} to PP. These constrain the eta-eta' mixing angle to a consistent value, phi approx 42 degrees; we find that the c cbar components are lesssim 5% in amplitude. We also find that, while the data hint at a small gluonic component in the eta', the conclusions depend sensitively on unknown form factors associated with exclusive dynamics. In addition, we predict BR(psi' to eta' gamma) approx 1 10^{-5} and BR(chi_{c0} to eta eta') approx 2 10^{-5} - 1 10^{-4}. We provide a method to test the mixing using chi_{c2} to eta eta, eta' eta', and eta eta' modes and make some general observations on chi_{c0,2} decays. We also survey the semileptonic and hadronic decays of bottom and charmed mesons and find some modes where the mixing angle can be extracted cleanly with the current experimental data, some where more data will allow this, and some where a more detailed knowledge of the different amplitudes is required.Comment: 34 pages, 11 figures. v2: version published in JHEP, added substantial section on B and D meson electroweak decays, added comment on psi' to eta(')/eta_c gamma, Figs 5 and 6 split and made clearer, added references, other minor revisions which don't change conclusion

The Jacobi Polynomials QCD analysis for the polarized structure function

We present the results of our QCD analysis for polarized quark distribution and structure function $xg_1 (x,Q^2)$. We use very recently experimental data to parameterize our model. New parameterizations are derived for the quark and gluon distributions for the kinematic range $x \epsilon [10^{-8},1]$, $Q^2 \epsilon [1,10^6]$ GeV^2. The analysis is based on the Jacobi polynomials expansion of the polarized structure functions. Our calculations for polarized parton distribution functions based on the Jacobi polynomials method are in good agreement with the other theoretical models. The values of $\Lambda_{QCD}$ and $\alpha_s(M_z)$ are determined.Comment: 23 pages, 8 figures and 4 table

Searching for Composite Neutrinos in the Cosmic Microwave Background

We analyze signals in the Cosmic Microwave Background (CMB) in theories where the small Dirac neutrino masses arise as a consequence of the compositeness of right-handed neutrinos. In such theories, the right-handed neutrinos are massless ``baryons'' of a new strong gauge interaction. We find that the results crucially depend on whether or not the new strong sector undergoes chiral symmetry breaking. In the case with chiral symmetry breaking, we find that there are indeed signals in the CMB, but none of them is a direct consequence of neutrino compositeness. In contrast, if the underlying theory does not undergo chiral symmetry breaking, the large scattering cross-section among the composites gives rise to a sizable CMB signal over a wide region of the parameter space, and it can potentially probe whether the neutrino mass spectrum is hierarchical, inverse hierarchical, or degenerate. We also discuss collider constraints on the compositeness in the context of the CMB signals.Comment: 26 pages. References and clarifying comments added. Version appearing to JHE

Heavy Quarkonium States with the Holographic Potential

The quarkonium states in a quark-gluon plasma is examined with the heavy quark potential implied by the holographic principle. Both the vanila AdS-Schwarzschild metric and the one with an infrared cutoff are considered. The dissociation temperature is calculated by solving the Schr\"o dinger equation of the potential model. In the case of the AdS-Schwarzschild metric with a IR cutoff, the dissociation temperatures for $J/\psi$ and $\Upsilon$ with the U-ansatz of the potential are found to agree with the lattice results within a factor of two.Comment: 9 pages with 2 figues in Revte

Phase space constraints and statistical jet studies in heavy-ion collisions

The effect of the correlation induced by global momentum conservation on the two-particle distribution in nucleus-nucleus collisions is discussed, with a focus on the generic case of collisions with a non-vanishing impact parameter.Comment: 5 pages, invited talk at the RHIC & AGS Annual Users' Meeting, Brookhaven Nat. Lab. (USA) and at the EPS HEP 2007 Conference, Manchester (UK

Constraints on Regge models from perturbation theory

We study the constraints that the operator product expansion imposes on large $N_c$ inspired QCD models for current-current correlators. We focus on the constraints obtained by going beyond the leading-order parton computation. We explicitly show that, assumed a given mass spectrum: linear Regge behavior in $n$ (the principal quantum number) plus corrections in $1/n$, we can obtain the logarithmic (and constant) behavior in $n$ of the decay constants within a systematic expansion in $1/n$. Our example shows that it is possible to have different large $n$ behavior for the vector and pseudo-vector mass spectrum and yet comply with all the constraints from the operator product expansion.Comment: 14 pages, 6 figures; two references added, numerical analysis extended, main conclusions unchange