Narrow Results

Using data collected by FOCUS, we present a preliminary measurement for the vector meson semileptonic branching ratio . Using a sample of 397 ± 42 and 11, 811 ± 151 D⁺ → ρ⁰μ⁺ν and events, respectively, we find .

Based on an 87-fb^-1 dataset collected by the Babar detector at the PEP-II asymmetric-energy B-Factory, a search for mixing has been made using the semileptonic decay modes D*⁺ → π⁺D⁰, D⁰ → Kev (+c.c.). The use of these modes allows unambiguous flavor tagging and a combined fit of the D⁰ decay time and D*⁺-D⁰ mass difference (ΔM) distributions. The high-statistics sample of unmixed semileptonic D⁰ decays is used to model the ΔM distribution and time-dependence of mixed events directly from the data. Neural networks are used to select events and reconstruct the D⁰. A result consistent with no charm mixing has been obtained, R_mix = 0.0023 ± 0.0012 ± 0.0004. This corresponds to an upper limit of R_mix < 0.0042 (90% CL).

We present a study of D⁰ decaying to K^-ℓ⁺ν and π^-ℓ⁺ν final states using a 282 fb^-1 data sample collected by the Belle experiment at the KEKB e⁺e^- collider. The D⁰ flavor and momentum are tagged through a full reconstruction of the recoiling charm meson and additional mesons from fragmentation. The reconstruction method provides very good resolution in neutrino momentum and in q² = (p_ℓ + p_ν)². Normalizing to the total number of D⁰ tags, we measure the absolute branching fractions to be and and the semi-leptonic form factors (within the modified pole model) and .

The semileptonic decays of the lowest-lying double-heavy baryons are treated in a quark model. For the Ξ_bb, hyperfine mixing in the spin wave function leaves the total rate for decay into the lowest lying daughter baryons essentially unchanged, but changes the relative rates into the Ξ_bc and . The same pattern is obtained in the decays of the Ω_bb. For the Ξ_bc, this mixing leads to factor of about 17 suppression in the decay rate to the when wave functions truncated to the largest components are used, but the total semileptonic decay rate of the parent baryon remains essentially unchanged. For the Ω_bc, the decay to the is suppressed by a factor of more than 25 from the unmixed case. When the full wave functions are used, the large suppression of the decays to the and persists.

We study rare decays , and in NSIs. We calculate the NSIs branching ratios of these decays. There is a strong dependence of these on new physics parameter. We include second and third generation of quarks in the loop for these decays. We show that these provide stringent constraints on , where Q = u, c, t, and , where q = d, s, b. It is also pointed out that for α, β = e, μ.

The complete spectrum of $c\bar{b}$ states is obtained in a phenomenological nonrelativistic quark model (NRQM), which consists of a confinement potential and one gluon exchange potential (OGEP) as effective quark–antiquark potential. We make predictions for the radiative decay (E1 and M1) widths and weak decay widths of $c\bar{b}$ states in the framework of NRQM formalism.

The complete spectrum of $c\bar{b}$ states is obtained in a phenomenological nonrelativistic quark model (NRQM), which consists of a confinement potential and one gluon exchange potential (OGEP) as effective quark–antiquark potential with coupled channel effects. We make predictions for the radiative decay (E1 and M1) widths and weak decay widths of $c\bar{b}$ states in the framework of NRQM formalism.