21,519 research outputs found
Leptoproduction of charm revisited
We calculate the energy--momentum distribution of the charmed quarks produced
in neutrino reactions on protons, quantifying the importance of mass and
current non--conservation effects. We study the strange and charm distributions
probed in neutrino interactions in the presently accessible kinematical region.
Some ambiguities inherent to the extraction of the parton densities from dimuon
data are pointed out.Comment: 9 pages, DFTT 72/9
On the low x behaviour of nuclear shadowing
We calculate the x dependence of nuclear shadowing at moderate values of Q^2
by using HERA diffractive data and, for consistency, F2 parameterization of
ZEUS. We show that no decrease of shadowing occurs down to very low x (x =
10^-4).Comment: 9 pages, submitted on june for publicatio
Longitudinal and Transverse Nuclear Shadowing
Nuclear shadowing arises from multiple scattering of the hadronic
fluctuations of the virtual photon in a nucleus. We predict different
longitudinal and transverse shadowing and an A-dependence of R which can be up
to a 50% effect. The possibility of detecting nuclear effects on R at HERA is
discussed.Comment: latex, 6 page
Extracting the Strange Density from
We present a QCD analysis of the strange and charm contributions to the
neutrino deep inelastic structure function . We show that next-to-leading
order effects, which are relatively important for , play a lesser role in
the case of . The neutrino--antineutrino difference provides a new determination of the strange density, which
exhibits some advantages with respect to other traditional methods.Comment: 12 page
Evaluation of fuzzy inference systems using fuzzy least squares
Efforts to develop evaluation methods for fuzzy inference systems which are not based on crisp, quantitative data or processes (i.e., where the phenomenon the system is built to describe or control is inherently fuzzy) are just beginning. This paper suggests that the method of fuzzy least squares can be used to perform such evaluations. Regressing the desired outputs onto the inferred outputs can provide both global and local measures of success. The global measures have some value in an absolute sense, but they are particularly useful when competing solutions (e.g., different numbers of rules, different fuzzy input partitions) are being compared. The local measure described here can be used to identify specific areas of poor fit where special measures (e.g., the use of emphatic or suppressive rules) can be applied. Several examples are discussed which illustrate the applicability of the method as an evaluation tool
Unitarization of Structure Functions at Large
We discuss the effects of the -channel unitarization on the and
dependence of structure functions. The unitarization is implemented at
the level of photoabsorption cross sections by resorting to the light--cone
wave functions of virtual photons and to the diagonalization property of the
scattering matrix in a basis of Fock states of the photon with fixed transverse
size. Triple pomeron effects are also explicitly taken into account. We find
large unitarity corrections to the structure functions at . The
results are in very good agreement with the existing NMC and the preliminary
HERA data.Comment: 12 page
Factorization properties of the diffraction dissociation of longitudinal photons
We develop the pQCD description of the diffraction dissociation (DD) of
longitudinal photons. We demonstrate that the longitudinal diffractive
structure function does not factor into the flux of pomerons and the partonic
structure function of the pomeron, thus defying the usually assumed Regge
factorization. In contrast to DD of the transverse photons, DD of the
longitudinal photons is strongly peaked at . We comment on duality
properties of DD in deep inelastic scattering.Comment: 11 page
The category of local algebras and points proches
Categorial methods for generating new local algebras from old ones are
presented. A direct proof of the differential structure of the prolongations of
a manifold is proposed
Genetic variability of the coat protein gene of isolates of Citrus Variegation Virus from Campania (southern Italy)
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