[en] We present calculations of the charming-penguin long-distance contributions to B->Kπ decays due to intermediate charmed meson states. Our calculation is based on the chiral effective Lagrangian for light and heavy mesons, corrected for the hard pion and kaon momenta. We find that the charming-penguin contributions increase significantly the B->Kπ decay rates in comparison with the short-distance contributions, giving results in better agreement with experimental data

[en] Boron Neutron Capture Therapy, a promising modality for the treatment of malignant tumors, relies on the use of neutron beams of suitable energy and intensity. For deep-seated tumors, simulations indicate that the optimal neutron energy is in the epithermal region, and in particular between 1 and 10 keV. Therapeutic neutron beams of high spectral purity could be produced with low-energy accelerators, through a suitable neutron producing reaction. In this talk we present an overview of some recently investigated reactions for the production of intense epithermal neutron beams for BNCT, and their potential use towards the setup of an hospital-based BNCT facility

[en] From the experimental branching ratios for B^-→ρ⁰l^- anti ν_l and D⁺→ anti K*⁰ ( anti K⁰) e⁺ν_e one finds, in the heavy quark limit of HQET, vertical stroke V_buvertical stroke =(8.1±1.7)x10^-3, larger but consistent with the actual quoted range (2-7)x10^-3. In the same framework one predicts for R(B→K*γ)=(2±2)10^-2. (orig.)

[en] The use of boron neutron capture therapy (BNCT) for the treatment of deep-seated tumors requires neutron beams of suitable energy and intensity. Simulations indicate the optimal energy to reside in the epithermal region, in particular between 1 and 10 keV. Therapeutic neutron beams with high spectral purity in this energy range could be produced with accelerator-based neutron sources through a suitable neutron-producing reaction. Herein, we report on different solutions that have been investigated as possible sources of epithermal neutron beams for BNCT. The potential use of such sources for a hospital-based therapeutic facility is discussed

[en] We propose a constituent quark model to evaluate heavy decay constants and form factors relevant for B→D^(*) semileptonic transitions. We show that the model reproduces the scaling laws dictated by the spin-flavor symmetry in the heavy quark limit and describes quite well the experimental data. (orig.)

[en] Walking technicolor (WTC) models predict the existence of heavy neutral pseudo-Goldstone bosons (PGBs), whose masses are typically expected to be larger than 100 GeV. In this paper, we investigate the production and decay of these particles at the high energy e⁺e^- experiments, LEP II and NLC. We find that, in WTC models, the production of neutral PGBs can be significantly enhanced, by one or two orders of magnitude, with respect to the predictions of traditional (QCD-like) TC models. The origin of such an enhancement is the existence of several low energy TC scales, that are likely to appear in WTC theories. This could allow the PGBs to be observed even at the energy and luminosity of the LEP II experiment. At LEP II, the PGBs are expected to be produced in the e⁺e^- →P γ channel, and, possibly, in the e⁺e^-→P e⁺e^- channel, with a total rate that can be of the order of several tenths per year. Due to the typical large values of PGB masses, the relative branching ratios of PGB decays, in WTC theories, are different from those predicted in traditional TC models. In particular, a large fraction of these decays can occur in the P →γγ channel. In considering the PGB production, at LEP II, we find that, in most of the final states, the distinctive signatures of WTC events should allow the Standard Model background to be reduced to a negligible level. We also find that, at a 500 GeV NLC experiment, the production of neutral PGBs can occur in several channels, and can be of the order of 10³ events per year. Instead, when we consider traditional TC models, we find that no PGB are typically predicted to be observed, both at LEP II and the NLC experiment. (orig.)

[en] By using a constituent quark model we compute the form factors relevant to semileptonic transitions of the B mesons into low-lying p-wave charmed mesons. We evaluate the q² dependence of these form factors and compare them with other model calculations. The Isgur-Wise functions τ_1/2 and τ_3/2 are also obtained in the heavy quark limit of our results. (orig.)

[en] The flat-space limit of the one-loop effective potential for SO(10) GUT close-quote s in spatially flat Friedmann-Robertson-Walker cosmologies is applied to study the dynamics of the early universe. The numerical integration of the corresponding field equations shows that, for such grand unified theories, a sufficiently long inflationary stage is achieved for suitable choices of the initial conditions. However, a severe fine-tuning of these initial conditions is necessary to obtain a large e-fold number. In the direction with residual symmetry SU(4)_PS circle-times SU(2)_L circle-times SU(2)_R, one eventually finds parametric resonance for suitable choices of the free parameters of the classical potential. This phenomenon leads in turn to the end of inflation. copyright 1996 The American Physical Society

[en] The results of a fit of two body Cabibbo allowed D meson decays in the factorized approximation, are presented, using the two-loop effective Hamiltonian and a resonance dominated model for final state interactions. Using the same values for all parameters, the branching ratios and the CP violating asymmetries are predicted for Cabibbo suppressed charged D meson decays. The predictions for the asymmetries are larger than expected and not too far from the experimental possibilities. (author). 25 refs., 6 tabs

[en] We find in a rather general class of SO(10) unified models the upper limit for the proton lifetime: τ_p≤1.6x10^+33±3 yr, where the large error is due to the uncertainties on sin²θ_W(M_W) and α₃(M_W). (orig.)