5,273 research outputs found
Improving Extractions of |Vcb| and the b Quark Mass from Semileptonic Inclusive B Decay
Recent advances in improving extractions of |Vcb| and m_b from spectra of
semileptonic inclusive B decay are reported. Results of a general moment
analysis of the lepton energy spectrum and the hadronic invariant mass spectrum
are summarized. The calculation of the general O(\alpha_s) structure functions
for semileptonic B decay is reported, which has allowed the calculation of the
O(\alpha_s Lambda_{QCD} /m_b) terms for the hadronic invariant mass moments to
be carried out. Recent theoretical advances and improvements in experimental
data has allowed extractions of the CKM element |Vcb| to improve to the 2%
level.Comment: 8 pages, 2 figures. Talk given at MRST2004, May 12-14, Concordia,
Montrea
Quantum relative positioning in Hilbert space
A new class of state transformations that are quantum mechanically prohibited
is introduced. These can be seen as the generalization of the universal-NOT
transformation which, for all pure inputs state of a given Hilbert space
produces pure outputs whose projection on the original state is fixed to a
value smaller than one. The case of not pure output states is also addressed.
We give an application of these transformations in the context of separability
criteria.Comment: 5 pages, 1 figure; new material added: in particular we present an
application of quantum movers in the context of separability criteria. Typos
corrected. Phys. Rev. A, accepted for publicatio
Radiative transitions of and
We study radiative decays of and using
light-cone QCD sum rules. In particular, we consider the decay modes
and and evaluate the hadronic parameters in the transition
amplitudes analyzing correlation functions of scalar, pseudoscalar, vector and
axial-vector quark currents. In the case of
we also consider determinations based on two different correlation functions in
HQET. The decay widths turn out to be different than previous estimates
obtained by other methods; the results favour the interpretation of
and as ordinary mesons.Comment: RevTex, 23 pages, 9 eps figure
Three-meter balloon-borne telescope
The Three-Meter Balloon-Borne Telescope is planned as a general purpose facility for making far-infrared and submillimeter astronomical observations from the stratosphere. It will operate throughout the spectral range 30 microns to 1 millimeter which is largely obscurred from the ground. The design is an f/13.5 Cassegrain telescope with an f/1.33 3-meter primary mirror supported with a 3-axis gimbal and stabilization system. The overall structure is 8.0 m high by 5.5 m in width by 4.0 m in depth and weighs 2000 kg. This low weight is achieved through the use of an ultra lightweight primary mirror of composite construction. Pointing and stabilization are achieved with television monitoring of the star field, flex-pivot bearing supports, gyroscopes, and magnetically levitated reaction wheels. Two instruments will be carried on each flight; generally a photometric camera and a spectrometer. A 64-element bolometer array photometric camera operating from 30 to 300 microns is planned as part of the facility. Additional instruments will be derived from KAO and other development programs
Ultra-efficient Cooling in Ferromagnet-Superconductor Microrefrigerators
A promising scheme for electron microrefrigeration based on
ferromagnet-superconductor contacts is presented. In this setup, cooling power
densities up to 600 nW/m can be achieved leading to electronic
temperature reductions largely exceeding those obtained with existing
superconductor-normal metal tunnel contacts. Half-metallic CrO/Al bilayers
are indicated as ideal candidates for the implementation of the device.Comment: 9 pages, 3 figures, submitted to Applied Physics Letter
Balloon-borne three-meter telescope for far-infrared and submillimeter astronomy
The scientific objectives, engineering analysis and design, results of technology development, and focal-plane instrumentation for a two-meter balloon-borne telescope for far-infrared and submillimeter astronomy are presented. The unique capabilities of balloon-borne observations are discussed. A program summary emphasizes the development of the two-meter design. The relationship of the Large Deployable Reflector (LDR) is also discussed. Detailed treatment is given to scientific objectives, gondola design, the mirror development program, experiment accommodations, ground support equipment requirements, NSBF design drivers and payload support requirements, the implementation phase summary development plan, and a comparison of three-meter and two-meter gondola concepts
Microstructure and chemical composition of Roman orichalcum coins emitted after the monetary reform of Augustus (23 B.C.)
A collection of ancient Roman orichalcum coins, i.e., a copper-zinc alloy, minted under the reigns from Caesar to Domitianus, have been characterised using scanning electron microscopy (SEM-EDS) and electron microprobe analysis (EMPA). We studied, for the first time, coins emitted by Romans after the reforms of Augustus (23 B.C.) and Nero (63-64 A.D). These coins, consisting of asses, sestertii, dupondii and semisses, were analysed using non- and invasive analyses, aiming to explore microstructure, corrosive process and to acquire quantitative chemical analysis. The results revealed that the coins are characterized by porous external layers, which are affected by dezincification and decuprification processes. As pictured by the X-ray maps, the elemental distribution of Cu and Zn shows patterns of depletion that in some cases penetrate in deep up to 1 mm. The composition of the un-corroded nucleus is a Cu-Zn alloy containing up to 30% of Zn, typical of coins produced via cementation process
- …