2,311 research outputs found
Description of self-synchronization effects in distributed Josephson junction arrays using harmonic analysis and power balance
Power generation and synchronisation in Josephson junction arrays have
attracted attention for a long time. This stems from fundamental interest in
nonlinear coupled systems as well as from potential in practical applications.
In this paper we study the case of an array of junctions coupled to a
distributed transmission line either driven by an external microwave or in a
self-oscillating mode. We simplify the theoretical treatment in terms of
harmonic analysis and power balance. We apply the model to explain the large
operation margins of SNS- and SINIS-junction arrays. We show the validity of
the approach by comparing with experiments and simulations with
self-oscillating es-SIS junction arrays.Comment: 5 pages, 3 figure
mixing and the next-to-leading-order power correction
The next-to-leading-order power correction for and
form factors are evaluated and employed to explore the
mixing. The parameters of the two mixing angle scheme are
extracted from the data for form factors, two photon decay widths and radiative
decays. The analysis gives the result:
, where
and are the decay constants and the mixing
angles for the singlet (octet) state. In addition, we arrive at a stringent
range for MeV MeV.Comment: 23 pages, 9 figures, To be publshied in Phys. Rev.
Beam-Dynamics Studies and Advanced Accelerator Research at CTF-3: Compact Final Focus, Laser Compton Scattering, Plasmas, etc.
Preliminary investigations are summarized on the possible use of the CTF3 facility for extended beam-dynamics studies and advanced accelerator R&D, which would exploit its unique properties and beam availability. The key element of these considerations is the possible addition of a test beam-delivery system comprising a compact final focus and advanced collimation concepts, scaled from 3 TeV down to low energy and having a short total length. Operational experience, verification of critical questions (octupole tail folding, beam halo transport, etc.), diagnostics (e.g., rf BPMs) and stabilization could all be explored in such a facility, which would benefit not only the CLIC study, but all linear collider projects. Another interesting application would be the study of plasma-beam interaction, which may include plasma focusing, plasma acceleration, ion-channel radiation, and plasma wigglers
Two photon decay of the pseudoscalars, the chiral symmetry breaking corrections
The extrapolation of the decay amplitudes of the pseudoscalar mesons into two
photons from the soft meson limit where it is obtained from the axial-anomaly
to the mass shell involves the contribution of the 0^ - continuum. These chiral
symmetry breaking corrections turn out to be large. The effects of these
corrections on the calculated pi ^0 decay rate, on the values of the
singlet-octet mixing angle and on the ratios f_8 / f_pi and f_0 / f_pi are
discussed. The implications for the transition form factors gamma gamma* -->
pseudoscalars are also evaluated and confronted with the available experimental
data.Comment: Computational errors straightened and study of the implications on
the form factors of the transitions gamma gamma* --> pseudoscalars adde
Determination of the and Mixing Angle from the Pseudoscalar Transition Form Factors
The possible range of mixing angle is determined from the
transition form factors and with
the help of the present experimental data. For such purpose, the quark-flavor
mixing scheme is adopted and the pseudoscalar transition form factors are
calculated under the light-cone pQCD framework, where the transverse momentum
corrections and the contributions beyond the leading Fock state have been
carefully taken into consideration. We construct a phenomenological expression
to estimate the contributions to the form factors beyond the leading Fock state
based on their asymptotic behavior at and . By taking
the quark-flavor mixing scheme, our results lead to , where the first error coming from experimental
uncertainty and the second error coming from the uncertainties of the
wavefunction parameters. The possible intrinsic charm component in and
is discussed and our present analysis also disfavors a large portion of
intrinsic charm component in and , e.g. .Comment: 18 Pages, 3 figures. Several references added. To be published in
EPJ
Instanton Contribution to the Pion Electro-Magnetic Formfactor at Q^2 > 1 GeV^2
We study the effects of instantons on the charged pion electro-magnetic
formfactor at intermediate momenta. In the Single Instanton Approximation
(SIA), we predict the pion formfactor in the kinematic region Q^2=2-15 GeV^2.
By developing the calculation in a mixed time-momentum representation, it is
possible to maximally reduce the model dependence and to calculate the
formfactor directly. We find the intriguing result that the SIA calculation
coincides with the vector dominance monopole form, up to surprisingly high
momentum transfer Q^2~10 GeV^2. This suggests that vector dominance for the
pion holds beyond low energy nuclear physics.Comment: 8 pages, 5 figures, minor revision
Higgs Physics with a gamma gamma Collider Based on CLIC 1
We present the machine parameters and physics capabilities of the CLIC Higgs
Experiment (CLICHE), a low-energy collider based on CLIC 1, the
demonstration project for the higher-energy two-beam accelerator CLIC. CLICHE
is conceived as a factory capable of producing around 20,000 light Higgs bosons
per year. We discuss the requirements for the CLIC 1 beams and a laser
backscattering system capable of producing a total (peak)
luminosity of cms with GeV. We show how CLICHE could be used to measure accurately
the mass, , and decays of a light Higgs boson.
We illustrate how these measurements may distinguish between the Standard Model
Higgs boson and those in supersymmetric and more general two-Higgs-doublet
models, complementing the measurements to be made with other accelerators. We
also comment on other prospects in and physics with
CLICHE.Comment: 34 pages, 20 figures, Latex. submitted to Eur. Phys. Jou
Primakoff effect in eta-photoproduction off protons
We analyse data on forward eta-meson photoproduction off a proton target and
extract the eta to gamma gamma decay width utilizing the Primakoff effect. The
hadronic amplitude that enters into our analysis is strongly constrained
because it is fixed from a global fit to available gamma p to p eta data for
differential cross sections and polarizations. We compare our results with
present information on the two-photon eta-decay from the literature. We provide
predictions for future PrimEx experiments at Jefferson Laboratory in order to
motivate further studies.Comment: 5 pages, 6 figures, gamma-gamma*-eta form factor included, version to
appear in Eur. Phys. J. A
Incidence trends of prostate cancer in East Anglia, before and during the era of PSA diagnostic testing
We investigated prostate cancer incidence in East Anglia from 1971 to 2000. Using age-period-cohort modelling, the number of cases expected in 1991–2000, based on pre-PSA trends, 1971–1990, was compared with that observed. Based on pre-1991 trends, 9203 new cases were expected in 1991–2000, but 9788 cases were observed, an excess of 6%
Power corrections to the transition form factor and pion distribution amplitudes
Employing the standard hard-scattering approach and the running coupling
method we calculate a class of power-suppressed corrections to the electromagnetic transition form
factor (FF) arising from the end-point
integration regions. In the investigations we use a hard-scattering amplitude
of the subprocess , symmetrized under
exchange important for exclusive
processes containing two external photons. In the computations the pion model
distribution amplitudes (DA's) with one and two non-asymptotic terms are
employed. The obtained predictions are compared with the CLEO data and
constraints on the DA parameters and at the
normalization point are extracted. Further restrictions on
the pion DA's are deduced from the experimental data on the electromagnetic FF
.Comment: 23 pages, 6 figures; the version published in Phys. Rev. D69, 094010
(2004
- …