Gauge hierarchy and decoupling

Vacuum expectation values are calculated in grand unification theories. (AIP)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87912/2/494_1.pd

A Finite Group Analysis of the Quark Mass Matrices and Flavor Dynamics

We perform a finite group analysis on the quark mass matrices. We argue that the dominant terms should be proportional to class operators of the group and that symmetry breaking to split the mass spectrum and simultaneous diagonalizability to suppress flavor changing neutral currents can be accomplished at this point. The natural setting is a multi-scalar model and the scalar doublets can have masses of the weak scale without any parameter tuning. When we specialize to $S_3$ as the group of choice, we arrive at the results that the dominant mass terms are \lhook democratic\rhook and that the ratios of light masses and the Cabbibo angle $\cong ({m_d\over m_s})^{1\over 2}$ are all given by group parameters in the breaking of $S_3$ to $S_2$. A large mass expansion is then performed and a generalized Wolfenstein parameterization is given. Further breaking by way of introducing heavy-light transitions in the down-type mass matrix is here related to the heavy-light Cabbibo-Kobayashi-Maskawa elements.Comment: 12 pages in plain Te

The Space-Cone Gauge, Lorentz Invariance and On-Shell Recursion for One-Loop Yang-Mills amplitudes

Recursion relations are succinctly obtained for $(++... +)$ and $(-++... +)$ amplitudes in the context of the space-cone gauge in QCD. We rely on the helicity symmetry of the problems to dictate our choices of reference twistors and the momentum shifts to complexify the amplitudes. Of great importance is the power of gauge Lorentz invariance, which is enough to determine the soft factors in the latter cases.Comment: 28 pages, 6 figure

QCD Corrections to b→sγγb\to s\gamma\gamma and Exclusive Bs→γγB_s\to \gamma\gamma Decay

The short distance QCD corrections to $b\to s\gamma \gamma$ are calculated in the leading logarithmic approximation. The equivalence of operator basis reduction for S-matrix elements by using the equations of motion or by proving a low energy theorem is discussed. We apply the above results to the exclusive $B_s\to \gamma\gamma$ decay. The branching ratio of this decay is found to be $5\times 10^{-7}$ in the Standard Model. We also found that QCD corrections modify considerably the ratio between CP-even and CP-odd two-photon amplitudes.Comment: revtex, 15 pages, 2 figures; revised version with corrections from electroweak penguin discussed, the conclusion remains unchange

Exact O(g^2 alpha_s) top decay width from general massive two-loop integrals

We calculate the b-dependent self-energy of the top quark at O(g^2 \alpha_s) by using a general massive two-loop algorithm proposed in a previous article. From this we derive by unitarity the O(\alpha_s) radiative corrections to the decay width of the top quark, where all effects associated with the $b$ quark mass are included without resorting to a mass expansion. Our results agree with the analytical results available for the O(\alpha_s) correction to the top quark width