Lepton Asymmetries in FCNC Decays of {\Lambda}b

Lepton polarization asymmetries for the flavor-changing neutral current (FCNC) dileptonic decays of {\Lambda}b baryons are calculated using single-component analytic (SCA) and multicomponent numerical (MCN) form factors. We show that these polarization asymmetries are insensitive to the transition form factors and, thus, the effects of QCD in the nonperturbative regime. Therefore, these observables can provide somewhat model independent ways of extracting the Wilson coefficients.Comment: 3 pages, 2 tables, 1 figure, To appear in the proceedings for the Eleventh Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2012

Soft Pion Emission in Semileptonic BB-Meson Decays

An analysis of semileptonic decays of $B$ mesons with the emission of a single soft pion is presented in the framework of the heavy-quark limit using an effective Lagrangian which implements chiral and heavy-quark symmetries. The analysis is performed at leading order of the chiral and inverse heavy mass expansions. In addition to the ground state heavy mesons some of their resonances are included. The estimates of the various effective coupling constants and form factors needed in the analysis are obtained using a chiral quark model. As the main result, a clear indication is found that the $0^{+}$ and $1^{+}$ resonances substantially affect the decay mode with a $D^{\ast}$ in the final state, and a less dramatic effect is also noticed in the $D$ mode. An analysis of the decay spectrum in the $D^{(\ast)}-\pi$ squared invariant mass is carried out, showing the main effects of including the resonances. The obtained rates show promising prospects for studies of soft pion emission in semileptonic $B$-meson decays in a $B$-meson factory where, modulo experimental cuts, about $10^5$ such decays in the $D$ meson mode and $10^4$ in the $D^{\ast}$ mode could be observed per year.Comment: 41 pages, uses revtex, epsf. 16 uuencoded postscript figures appended after `\end{document

A positive taper traveling-wave tube

Synchronism can be maintained between the RF beam current and the circuit electromagnetic waves over substantially the entire length of a traveling-wave tube by increasing the pitch of the last portion of the helical wave structure. There is no loss of linearity or beam conversion efficiency

Water velocity meter

Simple, inexpensive drag sphere velocity meter with a zero to 6 ft/sec range measures steady-state flow. When combined with appropriate data acquisition system, it is suited to applications where large numbers of simultaneous measurements are needed for current mapping or velocity profile determination

Recent progress in VSTOL technology

Progress in vertical and short takeoff and landing (V/STOL) aircraft technology, in particular, during the 1970 to 1980 period at Ames Research Center is discussed. Although only two kinds of V/STOL aircraft (the helicopter and the British direct lift Harrier) have achieved operational maturity, understanding of the technology has vastly improved during this 10 year period. To pursue an aggressive R and D program at a reasonable cost, it was decided to conduct extensive large scale testing in wind tunnel and flight simulation facilities, to develop low cost research aircraft using modified airframes or engines, and to involve other agencies and industry contractors in joint technical and funding arrangements. The STOL investigations include exploring STOL performance using the rotating cylinder flap concept, the augmentor wing, upon initiation of the Quiet Short Haul Research Aircraft program, the upper surface blown flap concept. The VTOL investigations were conducted using a tilt rotor aircraft, resulting in the XV-15 tilt rotor research aircraft. Direct jet lift is now being considered for application to future supersonic fighter aircraft

Mission Requirements for Exobiological Measurements on Venus

Mission planning for exobiological measurements on Venu

Modular Space Station Phase B Extension Preliminary Systems Design Report. Volume VI: Trades and Analyses

This document contains trades and analyses conducted during the Modular Space Station Phase B System Definition. Requirements and concepts considered and the tradeoff analysis leading to the preferred concept are presented. Integrated analyses are presented for subsystems and thermal control. Specific trades and analyses are presented for water management, atmosphere control, energy storage, radiators, navigation, control moment gyros, and system maintenance. The analyses of manipulator concepts and requirements, and supplemental analyses of information management issues are summarized. Subsystem reliability analyses include a detailed discussion of the critical failure analysis

Finite-difference fluid dynamics computer mathematical models for the design and interpretation of experiments for space flight

Numerical methods are used to design a spherical baroclinic flow model experiment of the large scale atmosphere flow for Spacelab. The dielectric simulation of radial gravity is only dominant in a low gravity environment. Computer codes are developed to study the processes at work in crystal growing systems which are also candidates for space flight. Crystalline materials rarely achieve their potential properties because of imperfections and component concentration variations. Thermosolutal convection in the liquid melt can be the cause of these imperfections. Such convection is suppressed in a low gravity environment. Two and three dimensional finite difference codes are being used for this work. Nonuniform meshes and implicit iterative methods are used. The iterative method for steady solutions is based on time stepping but has the options of different time steps for velocity and temperature and of a time step varying smoothly with position according to specified powers of the mesh spacings. This allows for more rapid convergence. The code being developed for the crystal growth studies allows for growth of the crystal as the solid-liquid interface. The moving interface is followed using finite differences; shape variations are permitted. For convenience in applying finite differences in the solid and liquid, a time dependent coordinate transformation is used to make this interface a coordinate surface

Hydrogen film cooling of a small hydrogen-oxygen thrust chamber and its effect on erosion rates of various ablative materials

An experimental investigation was conducted to determine what arrangement of film-coolant-injection orifices should be used to decrease the erosion rates of small, high temperature, high pressure ablative thrust chambers without incurring a large penalty in combustion performance. All of the film cooling was supplied through holes in a ring between the outer row of injector elements and the chamber wall. The best arrangement, which had twice the number of holes as there were outer row injection elements, was also the simplest. The performance penalties, presented as a reduction in characteristic exhaust velocity efficiency, were 0.8 and 2.8 percentage points for the 10 and 20 percent cooling flows, respectively, The best film-coolant injector was then used to obtain erosion rates for 19 ablative materials. The throat erosion rate was reduced by a factor of 2.5 with a 10 percent coolant flow. Only the more expensive silica phenolic materials had low enough erosion rates to be considered for use in the nozzle throat. However, some of the cheaper materials might qualify for use in other areas of small nozzles with large throat diameters where the higher erosion rates are more acceptable