17 research outputs found
Quenching of hadron spectra in DIS on nuclear targets
The multiple scatterings incurred by a hard quark produced in a nuclear
medium induce the emission of soft gluons which carry a fraction of the quark
energy and eventually affect the hadronization process. Here, the depletion of
semi-inclusive hadron spectra in DIS on various nuclei (N, Ne, Cu, Kr) is
computed as a function of nu and z to leading order in alpha_s through
medium-modified fragmentation functions. Using the transport coefficient q
previously determined from Drell-Yan production, the predictions are found to
be in good agreement with EMC and HERMES preliminary data. Calculations on Xe
targets are also presented and discussed.Comment: 20 pages, 8 figure
Soft Photoproduction Physics
Several topics of interest in soft photoproduction physics are discussed.
These include jet universality issues (particle flavour composition), the
subdivision into event classes, the buildup of the total photoproduction cross
section and the effects of multiple interactions.Comment: 10 pages, LaTeX2e, no figures, to appear in the proceedings of the
Durham Workshop on HERA Physics, ``Proton, Photon and Pomeron Structure'',
17--23 September 1995, Durham, U.
The dependence of the hard diffractive photoproduction of vector meson or photon and the range of pQCD validity
We consider two coupled problems.
We study the dependence on photon virtuality for the semihard
quasi--elastic photoproduction of neutral vector mesons on a quark, gluon or
real photon (at
GeV)). To this end we calculate the corresponding amplitudes (in an
analytical form) in the lowest nontrivial approximation of perturbative QCD. It
is shown that the amplitude for the production of light meson varies very
rapidly with the photon virtuality near .
We estimate the bound of the pQCD validity region for such processes. For the
real incident photon the obtained bound for the meson production is very
high. This bound decreases fast with the increase of , and we expect that
the virtual photoproduction at HERA gives opportunity to test the pQCD results.
The signature of this region is discussed. For the hard Compton effect the pQCD
should work good at not too high , and this effect seems measurable
at HERA.Comment: ReVTeX, 36 pages, 5 Postscript figures, uses epsf.st
Deep Inelastic Scattering at HERA
Results from the H1 and ZEUS experiments at HERA on deep inelastic scattering
are reviewed. The data lead to a consistent picture of a steep rise in the F_2
structure function and in the gluon density within the proton. Important new
information on the partonic structure of diffraction is emerging from H1 and
ZEUS. The space-like region in which the weak and electromagnetic interactions
become of equal strength is being explored for the first time. A possible
excess of events at high x and Q^2 compared to the expectations of the Standard
Model has been observed in both experiments.Comment: 80 pages, 42 figure
The Structure Function Ratios F2(Li)/F2(D) and F2(C)/F2(D) at small x
We present the structure function ratios F2(Li)/F2(D) and F2(C)/F2(D)
measured in deep inelastic muon-nucleus scattering at a nominal incident muon
energy of 200 GeV. The kinematic range 0.0001 < x < 0.7 and 0.01< Q^2 < 70
GeV^2 is covered. For values of less than both ratios indicate
saturation of shadowing at values compatible with photoabsorption results
Exclusive [Rho] 0 and [Phi] muoproduction at large Q 2
Arneodo M, Arvidson A, Badelek B, et al. Exclusive [Rho] 0 and [Phi] muoproduction at large Q 2. Nucl.Phys. B. 1994;429(3):503-529