376 research outputs found
Scientific Goals and Instrument Performance of the Gamma-Ray Imaging Detector AGILE
AGILE is a project of the Italian Space Agency (ASI) Scientific Program dedicated to γ-ray astrophysics. It will simultaneously detect and image photons in the 30 MeV – 50 GeV and in the 10–40 keV energy ranges. It is planned to be operational during the second half of 2005 and it will be the only Mission entirely dedicated to γ-ray astrophysics above 30 MeV during the period 2005–2007. We discuss the expected performance of the AGILE space detector, which scientific program emphasizes a quick response to γ-ray transients and multiwavelength studies of γ-ray sources
Study of microwave/gamma-ray properties for Fermi-LAT bright AGNs
Blazars are a small fraction of all extragalactic sources but, unlike other
objects, they are strong emitters across the entire electromagnetic spectrum.
Recent data in the microwave region of the electromagnetic spectrum have become
available to allow for systematic studies of blazars over large cosmological
volumes. This frequency band is indeed particularly suited for the selection of
blazars since at these frequencies the contamination from radio extended
components with steep spectra is no longer present and the emission from the
accretion process is negligible. During the first 3 months of scientific
operations Fermi-LAT detected 106 bright, high-galactic latitude (| b |> 10
deg) AGNs with high significance. In this study we investigate the possible
relations between the microwave and the gamma-ray emissions for Fermi-LAT
detected AGNs belonging to WMAP 5th year bright source catalog.Comment: 3 pages, 3 ps figures, "2009 Fermi Symposium", "eConf Proceedings
C091122
Search for Lambda^2/p^2 corrections to the QCD running coupling
We investigate the occurrence of power terms in the running
QCD coupling by analysing non-perturbative measurements of at
quite low momenta obtained from the lattice three-gluon vertex. Our study
provides some evidence for such a contribution. The phenomenological
implications of such a presence are reviewed.Comment: 3 pages, 1 figure, LaTeX, LATTICE98(Confinement
Results from a Non-Perturbative Renormalization of Lattice Operators
We propose a general renormalization method, which avoids completely the use
of lattice perturbation theory. We present the results from its numerical
applications to two-fermion operators on a lattice, at
.Comment: 3 pages postscript file. Contribution to Lattice '9
Lattice calculation of corrections to and of in the scheme
We report on very strong evidence of the occurrence of power terms in
\as(p), the QCD running coupling constant in the scheme, by
analyzing non-perturbative measurements from the lattice three-gluon vertex
between 2.0 and 10.0 GeV at zero flavor. While putting forward the caveat that
this definition of the coupling is a gauge dependent one, the general relevance
of such an occurrence is discussed. We fit MeV in perfect agreement with the result obtained by
the ALPHA group with a totally different method.
The power correction to \as(p) is fitted to .Comment: 21 pages, 3 figure
Large pion pole in Z_{S}^{MOM}/Z_{P}^{MOM} from Wilson action data
We show that, contrarily to recent claims, data from the Wilson (unimproved)
fermionic action at three different beta values demonstrate the presence of a
large Goldstone boson contribution in the quark pseudoscalar vertex,
quantitatively close to our previous estimate based on the SW action with
c_{SW}=1.769. We show that discretisation errors on Z_{S}^{MOM}/Z_{P}^{MOM}
seem to be much smaller than the Goldstone pole contribution over a very large
range of momenta. The subtraction of this non perturbative contribution leads
to numbers close to one-loop BPT.Comment: 12 pages, 5 figures, laTeX, minor corrections of typos, beta
dependence made more explicit, added one table giving the contribution of the
Goldstone vs. the discretisation errors at ap=
Non-Perturbative Renormalisation of Composite Operators
It is shown that the renormalisation constants of two quark operators can be
accurately determined (to a precision of a few per-cent using 18 gluon
configurations) using Chiral Ward identities. A method for computing
renormalisation constants of generic composite operators without the use of
lattice perturbation theory is proposed.Comment: 3 pages, uuencoded compressed postscript file, to appear in the
Proceedings of the International Symposium on Lattice Field Theory, Dallas,
Texas, 12-17 October 1993, Southampton Preprint 93/94-0
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