Enhanced subleading structure functions in semileptonic B decay

The charged lepton spectrum in semileptonic $B\to X_u \ell\bar\nu$ decay near maximal lepton energy receives important corrections from subleading structure functions that are formally suppressed by powers of $\Lambda_{QCD}/m_b$ but are enhanced by numerical factors. We investigate the series of higher order terms which smear over a region of width $\Delta E_\ell \sim \Lambda_{QCD}$ near the endpoint the contributions proportional to $\delta(E_\ell - m_b/2)$ times (i) the matrix element of the chromomagnetic operator, and (ii) four-quark operators. These contribute to the total rate at the few percent level, but affect the endpoint region much more significantly. Implications for the determination of $|V_{ub}|$ are discussed.Comment: 12 page

What can we learn from b->s gamma?

We review some recent theoretical progress in the understanding of weak radiative B meson decay, and discuss the implications of present and improved measurements of b -> s gamma for supersymmetric models.Comment: Talk presented at Beauty '97, UCLA, October 13-17, 1997. 9 pages, LaTeX, 3 figures, references adde

Relativistic quantum theories and neutrino oscillations

Neutrino oscillations are examined under the broad requirements of Poincar\'e-invariant scattering theory in an S-matrix formulation. This approach can be consistently applied to theories with either field or particle degrees of freedom. The goal of this paper is to use this general framework to identify all of the unique physical properties of this problem that lead to a simple oscillation formula. We discuss what is in principle observable, and how many factors that are important in principle end up being negligible in practice.Comment: 21 pages, no figure

Constraint of B_{d,s}-bar{B}_{d,s} mixing on warped extra-dimension model

Recent CDF measurement of the Bs-Bs oscillation frequency, at the Tevatron imposes significant constraint on various models for new physics. A warped extra-dimension model with custodial isospin symmetry accommodates the Bd-Bd mixing at tree level mainly through the Kaluza-Klein gluons. This is due to the misalignment between the bulk gauge eigenstates and the localized Yukawa eigenstates of the bulk fermions. We adopt the universal 5D Yukawa coupling model where all Yukawa couplings are of order one. The SM fermion mass spectra and mixings are controlled by the bulk Dirac mass parameters. With two versions of the hadronic parameter values, we investigate the implication of the observed BB mixings on this model. The CP-violating effects on the Bd system is shown to provide very strong constraint: The first Kaluza-Klein mass of a gluon has its lower bound about 3.7 TeV with 1 sigma uncertainty.Comment: published version in JHEP, CP-violating effects include

Measuring γ\gamma in B±→K±(KK∗)DB^\pm \to K^\pm (K K^*)_D decays

We develop a method to measure the CKM angle $\gamma$ without hadronic uncertainties from the analysis of $B^\pm \to K^\pm D^0$ and K^\pm \D0bar followed by singly Cabibbo-suppressed $D$ decays to non CP-eigenstates, such as $K^\pm K^{*\mp}$. This method utilizes the interference between $b\to c\bar u s$ and $b\to u\bar c s$ decays, and we point out several attractive features of it. All the modes that need to be measured for this method are accessible in the present data.Comment: 8 page

Helicity conservation in inclusive nonleptonic decay B to VX: Test of long-distance final state interaction

The polarization measurement in the inclusive B decay provides us with a simple test of how much the long-distance final-state interaction takes place as the energy of the observed meson varies in the final state. We give the expectation of the perturbative QCD for the energy dependence of the helicity fractions in a semiquantitative form. Experiment will tell us for which decay processes the perturbative calculation should be applicable.Comment: 15 pages in Revtex with 3 figures embedde