[en] A modified perturbative expression is given for the hadron electromagnetic form factors in perturbative QCD, which includes Sudakov suppression of the elastic scattering of quarks that are isolated in space. This suppression, arising from power suppressed and higher-order effects, is neglected in the standard asymptotic expression. The author studies the simplest case, the pion form factor, at first to present the formalism. Beyond momentum transfers of 20-30Λ_QCD the perturbative calculation becomes relatively insensitive to soft gluon exchange, which has been shown to dominate in leading-power analysis. The new expression is then applied to the proton Dirac form factor and the results for Λ_QCD = 0.1-0.2 GeV are in good agreement with experimental data. The analysis involves no phenomenological parameters such as a gluon mass, and the conclusions are insensitive to the different models of wave functions

[en] Holomorphicity is the analytical dependence of the gauge coupling function, f = 1/g² + Θ/8π², on the chiral fields in supergravity and supersymmetric gauge theories. The holomorphic property of 1/g² in supersymmetric gauge theories is studied by calculating its dependence on the mass matrix. The general representations of the mass matrix allowed by the constraints of gauge invariance is considered, and calculate the one- and two-loop corrections to 1/g² for both super QED and super Yang-Mills theories. For the massive mass matrix it is shown that one- and two-loop corrections to the gauge coupling constant are holomorphic. The reason for two-loop holomorphicity is that the second order logarithmic terms cancel out. For the mass matrix with at least one zero mode, it is recognized that there are two distinct cases which we call pseudo massive and intrinsically massless. For the case of pseudo mass matrix, the reducible representation of the gauge group is (i) complex with equal numbers of irreducible representations and their conjugates, (ii) real, or (iii) pseudo-real. Even though there are massless modes, it is found that the dependence of the gauge coupling constant on the mass matrix is holomorphic. This holomorphicity follows because the mass matrix can be perturbed to regularize the infrared divergence. For the case of intrinsically massless mass matrix, a reducible complex representation with unequal numbers of irreducible representations and their conjugates. The author shows that loop corrections to the gauge coupling constant are non-holomorphic. The reason is an infrared momentum cutoff is used which spins holomorphicity. The results show that, for the pseudo massive case, even though there is an infrared divergence, the one- and two-loop corrections are still holomorphic. Hence, it is concluded that non-holomorphicity is caused by the unbalanced numbers of families and antifamilies in the complex representation

[en] This dissertation concerns itself with two important issues in the study of gyrotrons. In Part I, the authors study the space charge instabilities in gyrotron electron beams via both solution of the linear dispersion equation and the nonlinear particle simulation. The linear analysis addressed the stabilizing effects of energy spread in the beams and the gradient of the external magnetic field. The nonlinear multi-frequency simulation demonstrates that the energy spread induced by multiple unstable waves in the nonlinear saturation stage is more significant than the corresponding spread induced by a single unstable wave. This indicates that the deleterious effect on the quality of the beam will be greater than previously expected, and emphasizes the need to design electron guns which are stable to this wave mode. In Part II, the authors develop a generalized theory of gyro-traveling-wave tubes (gyro-TWTs) operating at arbitrary cyclotron harmonics. In the framework of small signal theory, the authors obtain and analyze the dispersion equation and discuss a problem of spurious counterpropagating waves excitation. In the large-signal study, the authors predict the possibility of achieving high efficiency of operation at the first four cyclotron harmonics and show that the orbital efficiency of the relativistic gyro-TWT operating at the second cyclotron harmonic with large frequency up-conversion may exceed 60%. The results obtained also demonstrate that the sensitivity of the harmonic gyro-TWT efficiency with respect to the electron velocity spread strongly depends on axial wavenumbers of the travelling waves

No abstract available

[en] During the waste vitrification process, troublesome minor components in low-level radioactive waste streams could adversely affect either waste vitrification rate or melter life-time. Knowing the solubility limits for these minor components is important to determine pretreatment options for waste streams and glass formulation to prevent or to minimize these problems during the waste vitrification. A joint study between Pacific Northwest Laboratory and Rensselaer Polytechnic Institute has been conducted to determine minor component impacts in low-level nuclear waste glass

[en] Using a data sample of 122 million Υ(4S) → B(bar B) decays collected with BABAR detector at the PEP-II asymmetric B factory at SLAC, we measure the time-dependent-asymmetry parameters of the longitudinally polarized component in the B⁰ → ρ⁺ρ^- decay as C_L = -0.23 ± 0.24(stat) ± 0.14(syst) and S_L = -0.19 ± 0.33(stat) ± 0.11(syst). The B⁰ → ρ⁰ρ⁰ decay mode is also searched for in a data sample of about 227 million B(bar B) pairs. No significant signal is observed, and an upper limit of 1.1 x 10^-6 (90% C.L.) on the branching fraction is set. The penguin contribution to the CKM angle α uncertainty is measured to be 11^o. All results are preliminary

[en] I review the perturbative QCD approach to exclusive B meson decays, concentrating on the proof of the factorization theorem, the construction of the light-cone B meson wave function, the evaluation of heavy-to-light transition form factors, and the Sudakov effects in the end-point region of momentum fractions. I also discuss the application of the perturbative QCD formalism to two-body nonleptonic decays

No abstract available

[en] A new approach to isochron dating is described using different sizes of quartz and K-feldspar grains. The technique can be applied to sites with time-dependent external dose rates. It is assumed that any underestimation of the equivalent dose (D_e) using K-fledspar is by a factor F, which is independent of grain size (90-350 μm) for a given sample. Calibration of the beta source for different grain sizes is discussed, and then the sample ages are calculated using the differences between quartz and K-feldspar D_e from grains of similar size. Two aeolian sediment samples from north-eastern China are used to illustrate the application of the new method. It is confirmed that the observed values of D_e derived using K-feldspar underestimate the expected doses (based on the quartz D_e) but, nevertheless, these K-feldspar D_e values correlate linearly with the calculated internal dose rate contribution, supporting the assumption that the underestimation factor F is independent of grain size. The isochron ages are also compared with the results obtained using quartz D_e and the measured external dose rates. (author)

[en] Various schemes are examined in this study on the suppression of beam break-up (BBU) in a standing wave free electron laser two-beam accelerator (SWFEL/TBA). Two schemes are found to be not only able to effectively suppress the BBU but at the same time have minimum effect on the microwave generation process inside the SWFEL cavities. One is making the cavity-iris junction sufficiently gradual and the other is stagger-tuning the cavities