[en] Relative branching fractions of B_d,s⁰ → h⁺h'^- decays (where h,h' = K or π) and the direct Cp asymmetry A_CP in the B_d⁰ → K⁺π^- mode are measured with 179 ± 11 pb ^-1 of data collected using the CDF II detector at the Fermilab Tevatron p(bar p) collider. The first branching-fraction measurement of a B_s⁰ meson to two pseudoscalars, Β(B_s⁰ → K⁺ K^-), and a search for the baryon mode Λ_b⁰ → p⁺ h^- are also presented, in addition to branching-fraction limits on the rare channels B_s⁰ → K⁺ π^-, B_d⁰ → K⁺K^-, and B_s⁰ → π⁺π^-

[en] Fragmentation is the process by which bare quarks dress themselves up as hadrons. Since we cannot get reliable calculations of this process using perturbative quantum chromodynamics, the fragmentation properties of quarks must be obtained empirically. We report on the signal extraction and relative transverse momentum p_T spectrum determination that will lead to a high precision measurement of relative fragmentation fractions of b quarks into B hadrons, in 1.96 TeV p(bar p) collisions. Using 1.9 fb^-1 of data taken with the CDF-II detector, we fully reconstruct 473 ± 42 B_s⁰ → D_s^- π⁺, 15206 ± 203 B⁰ → D^- π⁺, 1483 ± 45 B⁰ → D*^-π⁺ and 4444 ± 297 Λ_b⁰ → Λ_c⁺π^- candidate decays. In order to reduce systematic uncertainties, ratios of p_T spectra are reported. We find that B_s and B⁰ mesons are produced with similar p_T and Λ_b baryons are produced with lower p_T than B⁰ mesons. Our results are consistent with previous CDF measurements suggesting a difference between fragmentation processes observed at lepton and hadron colliders

[en] The International Linear Collider (ILC) is a proposed electron-positron collider, expected to provide insight into important questions in particle physics. A part of the global R and D effort for the ILC is the design of its electron gun and electron bunching system. The present design of the bunching system has two sub-harmonic bunchers, one operating at 108 MHz and one at 433MHz, and two 5-cell 1.3 GHz (L-band) bunchers. This bunching system has previously been simulated using the Phase and Radial Motion in Electron Linear Accelerators (PARMELA) software, and those simulations indicated that the design provides sufficient bunching and acceleration. Due to the complicated dynamics governing the electrons in the bunching system we decided to verify and expand the PARMELA results using the more recent and independent simulation software General Particle Tracer (GPT). GPT tracks the motion and interactions of a set of macro particles, each of which represent a number of electrons, and provides a variety of analysis capabilities. To provide initial conditions for the macro particles, a method was developed for deriving the initial conditions from detailed simulations of particle trajectories in the electron gun. These simulations were performed using the Egun software. For realistic simulation of the L-band bunching cavities, their electric and magnetic fields were calculated using the Superfish software and imported into GPT. The GPT simulations arrived at similar results to the PARMELA simulations for sub-harmonic bunching. However, using GPT it was impossible to achieve an efficient bunching performance of the first L-band bunching cavity. To correct this, the first L-band buncher cell was decoupled from the remaining 4 cells and driven as an independent cavity. Using this modification we attained results similar to the PARMELA simulations. Although the modified bunching system design performed as required, the modifications are technically challenging to implement. Further work is needed to optimize the L-Band buncher design

[en] Results from the BABAR experiment are presented for searches for several rare FCNC B and D meson decays, including the modes B⁰ → (ell)⁺(ell)^- and D⁰ → (ell)⁺(ell)^-, B → (ρ,ω)γ and B⁺ → (K,π)⁺ν(bar ν). Limits on lepton flavor violation in neutrino-less τ decays are also discussed. Finally, results of BABAR searches for the strange pentaquark states Θ⁺(1540), Ξ^--(1860) and Ξ⁰(1860) are summarized

[en] To improve the understanding of accelerator-induced backgrounds at the SLAC B-Factory, we simulate lost particle backgrounds in the BABAR detector originating from beam-gas interactions and radiative Bhabha scatters. We have extended the GEANT4-based BABAR detector simulation to include beam-line components and magnetic fields up to 8.5 m away from the interaction point. We describe the simulation model and then compare preliminary predicted background levels with measurements from dedicated single- and colliding-beam experiments

[en] We report on a search for the pair production of second generation scalar leptoquarks (LQ) in p(bar p) collisions at the center of mass energy √s = 1.96TeV using a data set corresponding to an integrated luminosity of 1.0 fb^-1 collected with the D0 experiment at the Fermilab Tevatron Collider. Topologies arising from the LQ(ovr LQ) → μqνq and LQ(ovr LQ) → μqμq decay modes are investigated. No excess of data over the standard model prediction is observed and upper limits on the leptoquark pair production cross section are derived at the 95% C.L. as a function of the leptoquark mass and the branching fraction β for the decay LQ → μq. These are interpreted as lower limits on the leptoquark mass as a function of β. For β = 1 (0.5), scalar second generation leptoquarks with masses up to 316GeV (270GeV) are excluded

[en] Data collected by the D0 detector at a p(bar p) center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider have been used to search for pair production of the lightest supersymmetric partner of the top quark decaying into b(ell)(bar ν). The search is performed in the (ell)(ell)(prime) = eμ and μμ final states. No evidence for this process has been found in data samples of approximately 400 pb^-1. The domain in the [M((bar t)₁),M((bar ν))] plane excluded at the 95% C.L. is substantially extended by this search

[en] No abstract provided

[en] We search for the semi-inclusive process B_s⁰ → D_s^(*)D_s^(*) using 2.8 fb^-1 of p(bar p) collisions at √s = 1.96 TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We observe 26.6 ± 8.4 signal events with a significance above background of 3.2 standard deviations yielding a branching ratio of Β(B_s⁰ → D_s^(*)D_s^(*)) = 0.035 ± 0.010(stat) ± 0.011(syst). Under certain theoretical assumptions, these double-charm final states saturate CP-even eigenstates in the B_s⁰ decays resulting in a width difference of ΔΛ_s^CP/Λ_s = 0.072 ± 0.021(stat) ± 0.022(syst). This corresponds to the first evidence for a width difference in the B_s⁰ system

[en] The D0 experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid-argon calorimeters and central muon detector, remaining from Run I, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to D0