B→DsπB \to D_s \pi and the tree amplitude in B→π+π−B \to \pi^+ \pi^-

The recently-observed decay $B^0 \to D_s^+ \pi^-$ is expected to proceed mainly by means of a tree amplitude in the factorization limit: $B^0 \to \pi^- {(W^+)}^*$, ${(W^+)}^* \to D_s^+$. Under this assumption, we predict the corresponding contribution of the tree amplitude to $B^0 \to \pi^+ \pi^-$. We indicate the needed improvements in data that will allow a useful estimate of this amplitude with errors comparable to those accompanying other methods. Since the factorization hypothesis for this process goes beyond that proved in most approaches, we also discuss independent tests of this hypothesis.Comment: 7 pages, LaTeX, 1 figure, to be submitted to Phys. Rev. D (Brief Reports

Heavy bottom squark mass in the light gluino and light bottom squark scenario

Restrictive upper bounds on the heavy bottom squark mass when the gluino and one bottom squark are both light are based on the predicted reduction of $R_b$ (the fraction of $Z$ hadronic decays to $b \bar b$ pairs) in such a scenario. These bounds are found to be relaxed by the process $Z \to b\bar{\tilde b}{\tilde g}/{\bar b}{\tilde b}{\tilde g}$, which may partially compensate for the reduction of $R_b$. The relaxation of bounds on the top squark and the scale-dependence of the strong coupling constant are also discussed.Comment: 9 pages, LaTeX, 2 figures, to be submitted to Phys. Lett. B, more discussions adde

The factorizable amplitude in B0→π+π−B^0 \to \pi^+ \pi^-

Using the measured spectrum shape for $B \to \pi \ell \nu$, the rate for $B^+ \to \pi^+ \pi^0$, information on the Cabibbo-Kobayashi-Maskawa (CKM) matrix element $|V_{ub}|$, and theoretical inputs from factorization and lattice gauge theory, we obtain an improved estimate of the ``tree'' contribution to $B^0 \to \pi^+ \pi^-$. We find the branching ratio \b(B^0 \to \pi^+ \pi^-)|_{\rm tree} = (5.25^{+1.67}_{-0.50}) \times 10^{-6}, to be compared with the experimental value \b(B^0 \to \pi^+ \pi^-) = (4.55 \pm 0.44) \times 10^{-6}. The fit implies $|V_{ub}| = (3.62 \pm 0.34) \times 10^{-3}$. Implications for tree-penguin interference in $B^0 \to \pi^+ \pi^-$ and for other charmless $B$ decays are discussed.Comment: 11 pages, LaTeX, 3 figures, to be submitted to Phys. Rev.

Z decays into light gluinos: a calculation based on unitarity

The Z boson can decay to a pair of light gluinos through loop-mediated processes. Based on unitarity of the S-matrix, the imaginary part of the decay amplitude is computed in the presence of a light bottom squark. This imaginary part can provide useful information on the full amplitude. Implications are discussed for a recently proposed light gluino and light bottom squark scenario.Comment: 19 pages, LaTeX, 3 figures, submitted to Phys. Rev.

Two-Body Cabibbo-Suppressed Charmed Meson Decays

Singly-Cabibbo-suppressed decays of charmed particles governed by the quark subprocesses $c \to s u \bar s$ and $c \to d u \bar d$ are analyzed using a flavor-topology approach, based on a previous analysis of the Cabibbo-favored decays governed by $c \to s u \bar d$. Decays to $PP$ and $PV$, where $P$ is a pseudoscalar meson and $V$ is a vector meson, are considered. We include processes in which $\eta$ and $\eta '$ are produced.Comment: 18 pages, latex, 2 figures, to be submitted to Phys. Rev.

Final-State Phases in B→B \to Baryon-Antibaryon Decays

The recent observation of the decay \ob \to \Lambda_c^+ \bar p suggests that related decays may soon be visible at $e^+ e^-$ colliders. It is shown how these decays can shed light on strong final-state phases and amplitudes involving the spectator quark, both of which are normally expected to be small in B decays.Comment: 14 pages, LaTeX, 2 figures, submitted to Phys. Rev. D, references and discussion of helicity amplitudes adde

Information on B→ππB \to \pi \pi Provided by the Semileptonic Process B→πlνB \to \pi l \nu

Analysis of the present data on the semileptonic process $B \to \pi \ell \nu$ indicates that they have not yet reached the precision to provide adequate information on the $B \to \pi$ form factor $F_+(q^2)$, which for $q^2 = m_\pi^2$ is known to be related to the factorized color-favored (``$T$'', or ``tree'') contribution to $B^0 \to \pi^+ \pi^-$. It is shown here that with around 500 $B \to \pi \ell \nu$ events in which rate and spectrum are measured one can improve the accuracy of $T$ by a significant amount. A recent CLEO determination of the $D^* D \pi$ coupling constant is compared with an earlier prediction, and its role in the description of the $B \to \pi$ form factors is noted. When combined with an estimate of the penguin amplitude (``$P$'') obtained using flavor SU(3) symmetry from $B \to K \pi$ decays, information on $T$ allows one to gauge the effects of the penguin amplitude on extraction of the weak phase $\alpha = \phi_2$ from the time-dependent CP-violating rate asymmetry in $B^0 \to \pi^+ \pi^-$. The constraint on $\alpha$ implied by a recent experimental result on this asymmetry is described.Comment: 17 pages, LaTeX, 7 figures, revised version resubm. to Phys. Rev. D. Further modifications in abstract, text, and reference