Lepton Polarization and Forward-Backward Asymmetries in b -> s tau+ tau-

We study the spin polarizations of both tau leptons in the decay b -> s tau+ tau-. In addition to the polarization asymmetries involving a single tau, we construct asymmetries for the case where both polarizations are simultaneously measured. We also study forward-backward asymmetries with polarized tau's. We find that a large number of asymmetries are predicted to be large, >~ 10%. This permits the measurement of all Wilson coefficients and the b-quark mass, thus allowing the standard model (SM) to be exhaustively tested. Furthermore, there are many unique signals for the presence of new physics. For example, asymmetries involving triple-product correlations are predicted to be tiny within the SM, O(10^{-2}). Their observation would be a clear signal of new physics.Comment: 21 pages, LaTeX, 4 figures (included). Paper somewhat reorganized, references greatly expanded, conclusions unchange

CP-violating Majorana phases, lepton-conserving processes and final state interactions

The CP-violating phases associated with Majorana neutrinos can give rise to CP-violating effects even in processes that conserve total Lepton number, such as \mu -> eee+, \mu + e -> e + e and others. After explaining the reasons that make this happen, we consider the calculation of the rates for the process of the form \ell_a + \ell_b -> \ell_a + \ell_c, and its conjugate \bar\ell_a + \bar\ell_b -> \bar\ell_a + \bar\ell_c, where \ell_a, \ell_b and \ell_c denote charged leptons of different flavors. In the context of the Standard Model with Majorana neutrinos, we show that the difference in the rates depends on such phases. Our calculations illustrate in detail the mechanics that operate behind the scene, and set the stage for carrying out the analogous, more complicated (as we explain), calculations for other processes such as \mu -> eee+ and its conjugate.Comment: Latex, axodraw, 24 page

Possible Supersymmetric Effects on Angular Distributions in B→K∗(→Kπ)ℓ+ℓ−B \to K^* (\to K \pi) \ell^+ \ell^- Decays

We investigate the angular distributions of the rare B decay, $B \to K^* (\to K \pi) \ell^+ \ell^-$, in general supersymmetric extensions of the standard model. We consider the new physics contributions from the operators $O_{7,8,9,10}$ in small invariant mass region of lepton pair. We show that the azimuthal angle distribution of the decay can tell us the new physics effects clearly from the behavior of the distribution, even if new physics does not change the decay rate substantially from the standard model prediction

A Systematic Analysis of the Lepton Polarization Asymmetries in the Rare B Decay, B -> X_s\tau^+\tau^-

The most general model-independent analysis of the lepton polarization asymmetries in the rare B decay, \Bstt, is presented. We present the longitudinal, normal and transverse polarization asymmetries for the $\tau^+$ and $\tau^-$, and combinations of them, as functions of the Wilson coefficients of twelve independent four-Fermi interactions, ten of them local and two nonlocal. These procedures will tell us which type of operators contributes to the process. And it will be very useful to pin down new physics systematically, once we have the experimental data with high statistics and a deviation from the Standard Model is found.Comment: 24 pages, 8 figures, LaTe

First lattice QCD estimate of the g_{D^* D pi} coupling

We present the results of the first lattice QCD study of the strong coupling g_{D^* D pi}. From our simulations in the quenched approximation, we obtain g_{D^* D pi} = 18.8 +/- 2.3^{+1.1}_{-2.0} and hat(g)_c = 0.67 +/- 0.08^{+0.04}_{-0.06}. Whereas previous theoretical studies gave different predictions, our result favours a large value for hat(g)_c. It agrees very well with the recent experimental value by CLEO. hat(g) varies very little with the heavy mass and we find in the infinite mass limit hat(g)_infinity = 0.69(18).Comment: 24 pages, 7 figures; references added, corrected typos, Comments added about the continuum limi

The semileptonic B->pi decay in a Constituent Quark-Meson model

We evaluate the form factors describing the exclusive decay B-> pi l nu by using a Constituent Quark-Meson model based on an effective quark-meson Lagrangian (CQM). The model allows for an expansion in the pion momenta and we consider terms up to the first order in the pion field derivatives. We compute the leading terms in the soft pion limit and consider corrections to this limit.Comment: 6 pages, 3 figures, LaTeX (uses aps, epsf, revtex), formula 26 corrected, discussion enlarged, references updated and other minor change

Leptogenesis through direct inflaton decay to light particles

We present a scenario of nonthermal leptogenesis following supersymmetric hybrid inflation, in the case where inflaton decay to both heavy right handed neutrino and SU(2)_L triplet superfields is kinematically disallowed. Lepton asymmetry is generated through the decay of the inflaton into light particles by the interference of one-loop diagrams with right handed neutrino and SU(2)_L triplet exchange respectively. We require superpotential couplings explicitly violating a U(1) R-symmetry and R-parity. However, the broken R-parity need not have currently observable low-energy signatures. Also, the lightest sparticle can be stable. Some R-parity violating slepton decays may, though, be detectable in the future colliders. We take into account the constraints from neutrino masses and mixing and the preservation of the primordial lepton asymmetry.Comment: 11 pages including 3 figures, uses Revtex, minor corrections, references adde

Transition Form Factors between Pseudoscalar and Vector Mesons in Light-Front Dynamics

We study the transition form factors between pseudoscalar and vector mesons using a covariant fermion field theory model in $(3+1)$ dimensions. Performing the light-front calculation in the $q^+ =0$ frame in parallel with the manifestly covariant calculation, we note that the suspected nonvanishing zero-mode contribution to the light-front current $J^+$ does not exist in our analysis of transition form factors. We also perform the light-front calculation in a purely longitudinal $q^+ > 0$ frame and confirm that the form factors obtained directly from the timelike region are identical to the ones obtained by the analytic continuation from the spacelike region. Our results for the $B \to D^* l \nu_l$ decay process satisfy the constraints on the heavy-to-heavy semileptonic decays imposed by the flavor independence in the heavy quark limit.Comment: 20 pages, 14 figure