248 research outputs found
Factorial correlators: angular scaling within QCD jets
Factorial correlators measure the amount of dynamical correlation in
multiplicity between two separated phase-space windows. We present the
analytical derivation of factorial correlators for a QCD jet described at the
double logarithmic (DL) accuracy. We obtain a new angular scaling property for
properly normalized correlators between two solid-angle cells or two rings
around the jet axis. Normalized QCD factorial correlators scale with the
angular distance and are independent of the window size. Scaling violations are
expected beyond DL approximation, in particular from the subjet structure.
Experimental tests are feasible, and thus welcome.Comment: preprint SACLAY-T00-182, TSL/ISV-00-0239; 18 pages, latex, 4 figures;
submitted to Eur. Phys. J.
The photon structure and exclusive production of vector mesons in gamma-gamma collisions
The process of exclusive vector meson production (gamma gamma to J/psi rho^0)
is studied for almost real photons. This process may be reduced to
photoproduction of J/psi off the rho^0 meson. We discuss the possibility of
extracting the gluon distribution of rho^0 and of the photon from such
measurement. Predictions are also given for the reaction (e+e- to e+ e- J/psi
rho^0) for various e+e- cms energies typical for LEP and for the future linear
colliders.Comment: 10 pages with 3 Postscript figure
Inclusive single particle density in configuration space from the QCD-cascade in DLA approximation
The structure of the QCD gluonic cascade in configuration space is investigated. The explicit form of the inclusive single particle density in configuration space transverse coordinates is derived in the double logarithmic approximation (DLA) of QCD. The possible simplification of the multiparton density matrix formalism for DLA approach is found and discussed
Electronic and atomic kinetics in solids irradiated with free-electron lasers or swift-heavy ions
In this brief review we discuss the transient processes in solids under
irradiation with femtosecond X-ray free-electron-laser (FEL) pulses and
swift-heavy ions (SHI). Both kinds of irradiation produce highly excited
electrons in a target on extremely short timescales. Transfer of the excess
electronic energy into the lattice may lead to observable target modifications
such as phase transitions and damage formation. Transient kinetics of material
excitation and relaxation under FEL or SHI irradiation are comparatively
discussed. The same origin for the electronic and atomic relaxation in both
cases is demonstrated. Differences in these kinetics introduced by the
geometrical effects ({\mu}m-size of a laser spot vs nm-size of an ion track)
and initial irradiation (photoabsorption vs an ion impact) are analyzed. The
basic mechanisms of electron transport and electron-lattice coupling are
addressed. Appropriate models and their limitations are presented.
Possibilities of thermal and nonthermal melting of materials under FEL and SHI
irradiation are discussed
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