2,897 research outputs found
Observation of B_s Production at the Y(5S) Resonance
Using the CLEO detector at the Cornell Electron Storage Ring, we have observed the B_s meson in e^+e^- annihilation at the Υ(5S) resonance. We find 14 candidates consistent with B_s decays into final states with a J/ψ or a D_s^((*)-). The probability that we have observed a background fluctuation is less than 8×10^(-10). We have established that at the energy of the Υ(5S) resonance B_s production proceeds predominantly through the creation of B_s^*B̅ _s^* pairs. We find σ(e^+e^-→B^s^*B̅ ^*)=[0.11_(-0.03)^(+0.04)(stat)±0.02(syst)] nb, and set the following limits: σ(e^+e^-→B_sB̅ _s)/σ(e^+e^-→B_s^*B̅ _s^*)<0.16 and [σ(e^+e^-→B_sB̅ _s^*)+σ(e^+e^-→B_s*B̅ _s)]/σ(e^+e^-→B_s*B̅ _s^*)<0.16 (90% C.L.). The mass of the B_s^* meson is measured to be M_(B_s^*=[5.414±0.001(stat)±0.003(syst)] GeV/c^2
First Measurement of the Electromagnetic Form Factor of the Neutral Kaon at a Large Momentum Transfer and the Effect of Breaking
At large momentum transfers the photon interacts with the charges and spins
of the constituent partons in a hadron. It is expected that the neutral kaon
can acquire finite electromagnetic form factors because its wave function is
affected by the order of magnitude difference between the mass of the strange
quark and that of the down quark, or flavor breaking. We report on the
first measurement of the form factor of neutral kaons at the large timelike
momentum transfer of GeV by measuring the cross section for
at GeV using CLEO-c data with an integrated
luminosity of 586 pb. We obtain
, with a 90% C.L. interval of
. This is nearly an order of magnitude smaller than
, and indicates that the
effect of breaking is small. In turn, this makes it unlikely that the
recently observed strong violation of the pQCD prediction,
, which is based on the
assumption of similar wave functions for the pions and kaons, can be attributed
to breaking alone.Comment: 4 pages, 2 figures, accepted to PL
Primitive one-factorizations and the geometry of mixed translations
AbstractWe construct an infinite family of one-factorizations of Kv admitting an automorphism group acting primitively on the set of vertices but no such group acting doubly transitively. We also give examples of one-factorizations which are live, in the sense that every one-factor induces an automorphism, but do not coincide with the affine line parallelism of AG(n,2). To this purpose we develop the notion of a “mixed translation” in AG(n,2)
Microfluidic cartridge with integrated array of amorphous silicon photosensors for chemiluminescence detection of viral DNA
Portable and simple analytical devices based on microfluidics with chemiluminescence detection are particularly attractive for point-of-care applications, offering high detectability and specificity in a simple and miniaturized analytical format. Particularly relevant for infectious disease diagnosis is the ability to sensitively and specifically detect target nucleic acid sequences in biological fluids. To reach the goal of real-life applications for such devices, however, several technological challenges related to full device integration are still to be solved, one key aspect regarding on-chip integration of the chemiluminescence signal detection device. Nowadays, the most promising approach is on-chip integration of thin-film photosensors. We recently proposed a portable cartridge with microwells aligned with an array of hydrogenated amorphous silicon (a-Si:H) photosensors, reaching attomole level limits of detection for different chemiluminescence model reactions. Herein, we explore its applicability and performance for multiplex and quantitative detection of viral DNA. In particular, the cartridge was modified to accommodate microfluidic channels and, upon immobilization of three oligonucleotide probes in different positions along each channel, each specific for a genotype of Parvovirus B19, viral nucleic acid sequences were captured and detected. With this system, taking advantage of oligoprobes specificity, chemiluminescence detectability, and photosensor sensitivity, accurate quantification of target analytes down to 70 pmol L-1 was obtained for each B19 DNA genotype, with high specificity and multiplexing ability. Results confirm the good detection capabilities and assay applicability of the proposed system, prompting the development of innovative portable analytical devices with enhanced sensitivity and multiplexed capabilities
Negative Ion Drift and Diffusion in a TPC near 1 Bar
Drift velocity and longitudinal diffusion measurements are reported for a
Negative Ion TPC (NITPC) operating with Helium + carbon disulfide gas mixtures
at total pressures from 160 to 700 torr. Longitudinal diffusion at the
thermal-limit was observed for drift fields up to at least 700 V/cm in all gas
mixtures tested. The results are of particular interest in connection with
mechanical simplification of Dark Matter searches such as DRIFT, and for high
energy physics experiments in which a low-Z, low density, gaseous tracking
detector with no appreciable Lorentz drift is needed for operation in very high
magnetic fields.Comment: 7 pages, 3 figure
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