15,885 research outputs found
Two-photon width of the charmonium state X_(c2)
The two-photon width of X_(c2)^3P_2 state of charmonium has been measured using 14.4 fb^(-1) of e^+e^-data taken at âs
=9.46â11.30 GeV with the CLEO III detector. The yy-fusion reaction studied is e^+e^- â e^+e^-yy, â yy X_(c2) â yJ/Κ â ye^+e^-(”^+”^-). We measure Đ_(yy) (X_(c2))B(X_(c2)) â y
J/Κ)B(J/Κ â e^+e^- + ”^+”^-)= 13.2 ± 1.4(stat)± 1.1(syst) eV, and obtain Đ yy(Xc2)= 559 ± 57(stat) ± 48(syst) ± 36(br) eV. This result is in excellent agreement with the result of -fusion measurement by Belle and is consistent with that of the pp â X_(c2) â yy measurement, when they are both reevaluated using the recent CLEO result for the radiative decay X_(c2) â J/Κ
Demonstration of ultra-high-Q small mode volume toroid microcavities on a chip
Optical microcavities confine light spatially and temporally and find
application in a wide range of fundamental and applied studies. In many areas,
the microcavity figure of merit is not only determined by photon lifetime (or
the equivalent quality-factor, Q), but also by simultaneous achievement of
small mode volume V . Here we demonstrate ultra-high Q-factor small mode volume
toroid microcavities on-a-chip, which exhibit a Q/V factor of more than
. These values are the highest reported to date for any
chip-based microcavity. A corresponding Purcell factor in excess of 200 000 and
a cavity finesse of is achieved, demonstrating that toroid
microcavities are promising candidates for studies of the Purcell effect,
cavity QED or biochemical sensingComment: 4 pages, 3 figures, Submitted to Applied Physics Letter
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 ΄(5S) resonance. We find 14 candidates consistent with B_s decays into final states with a J/Ï or a D_s^((*)-). The probability that we have observed a background fluctuation is less than 8Ă10^(-10). We have established that at the energy of the ΄(5S) resonance B_s production proceeds predominantly through the creation of B_s^*BÌ
_s^* pairs. We find Ï(e^+e^-âB^s^*BÌ
^*)=[0.11_(-0.03)^(+0.04)(stat)±0.02(syst)]âânb, and set the following limits: Ï(e^+e^-âB_sBÌ
_s)/Ï(e^+e^-âB_s^*BÌ
_s^*)<0.16 and [Ï(e^+e^-âB_sBÌ
_s^*)+Ï(e^+e^-âB_s*BÌ
_s)]/Ï(e^+e^-âB_s*BÌ
_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)]ââGeV/c^2
Extended phase space for a spinning particle
Extended phase space of an elementary (relativistic) system is introduced in
the spirit of the Souriau's definition of the `space of motions' for such
system. Our formulation is generally applicable to any homogeneous space-time
(e.g. de Sitter) and also to Poisson actions. Calculations concerning the
Minkowski case for non-zero spin particles show an intriguing alternative: we
should either accept two-dimensional trajectories or (Poisson) noncommuting
space-time coordinates.Comment: 12 pages, late
Observing Gravitational Waves with a Single Detector
A major challenge of any search for gravitational waves is to distinguish
true astrophysical signals from those of terrestrial origin. Gravitational-wave
experiments therefore make use of multiple detectors, considering only those
signals which appear in coincidence in two or more instruments. It is unclear,
however, how to interpret loud gravitational-wave candidates observed when only
one detector is operational. In this paper, we demonstrate that the observed
rate of binary black hole mergers can be leveraged in order to make confident
detections of gravitational-wave signals with one detector alone. We quantify
detection confidences in terms of the probability that a signal
candidate is of astrophysical origin. We find that, at current levels of
instrumental sensitivity, loud signal candidates observed with a single
Advanced LIGO detector can be assigned . In the future,
Advanced LIGO may be able to observe single-detector events with confidences
exceeding .Comment: 8 pages, 4 figures; published in CQG; minor updates to match
published versio
Bayesian Value-of-Information Analysis: An Application to a Policy Model of Alzheimer's Disease
A framework is presented which distinguishes the conceptually separate decisions of which treatment strategy is optimal from the question of whether more information is required to inform this choice in the future. The authors argue that the choice of treatment strategy should be based on expected utility and the only valid reason to characterise the uncertainty surrounding outcomes of interest is to establish the value of acquiring additional information. A Bayesian decision theoretic approach is demonstrated though a probabilistic analysis of a published policy model of Alzheimerâs disease. The expected value of perfect information is estimated for the decision to adopt a new pharmaceutical for the population of US Alzheimerâs disease patients. This provides an upper bound on the value of additional research. The value of information is also estimated for each of the model inputs. This analysis can focus future research by identifying those parameters where more precise estimates would be most valuable, and indicating whether an experimental design would be required. We also discuss how this type of analysis can also be used to design experimental research efficiently (identifying optimal sample size and optimal sample allocation) based on the marginal cost and marginal benefit of sample information. Value-of-information analysis can provide a measure of the expected payoff from proposed research, which can be used to set priorities in research and development. It can also inform an efficient regulatory framework for new health care technologies: an analysis of the value of information would define when a claim for a new technology should be deemed âsubstantiatedâ and when evidence should be considered âcompetent and reliableâ when it is not cost-effective to gather anymore information.stochastic CEA; Bayesian decision theory; value of information.
Task iv- /research/ of the solar energy thermionic /set/ conversion development program third quarterly progress report, 1 dec. 1964 - 28 feb. 1965
Operational parameters for thermionic converter - cesium vapor diode formulation and computer method of analysi
The Lattice Schwinger Model: Confinement, Anomalies, Chiral Fermions and All That
In order to better understand what to expect from numerical CORE computations
for two-dimensional massless QED (the Schwinger model) we wish to obtain some
analytic control over the approach to the continuum limit for various choices
of fermion derivative. To this end we study the Hamiltonian formulation of the
lattice Schwinger model (i.e., the theory defined on the spatial lattice with
continuous time) in gauge. We begin with a discussion of the solution
of the Hamilton equations of motion in the continuum, we then parallel the
derivation of the continuum solution within the lattice framework for a range
of fermion derivatives. The equations of motion for the Fourier transform of
the lattice charge density operator show explicitly why it is a regulated
version of this operator which corresponds to the point-split operator of the
continuum theory and the sense in which the regulated lattice operator can be
treated as a Bose field. The same formulas explicitly exhibit operators whose
matrix elements measure the lack of approach to the continuum physics. We show
that both chirality violating Wilson-type and chirality preserving SLAC-type
derivatives correctly reproduce the continuum theory and show that there is a
clear connection between the strong and weak coupling limits of a theory based
upon a generalized SLAC-type derivative.Comment: 27 pages, 3 figures, revte
Measurement of the B Semileptonic Branching Fraction with Lepton Tags
We have used the CLEO II detector and 2.06fb^(-1) of Ï(4S) data to measure the B-meson semileptonic branching fraction. The BâXeÎœ momentum spectrum was obtained over nearly the full momentum range by using charge and kinematic correlations in events with a high-momentum lepton tag and an additional electron. We find B(BâXeÎœ) = (10.49±0.17±0.43)%, with overall systematic uncertainties less than those of untagged single-lepton measurements. We use this result to calculate the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element V_(cb) and to set an upper limit on the fraction of Ï(4S) decays to final states other than BBÌ
- âŠ