5,965 research outputs found
QCD analysis of D-parameter in near-to-planar three-jet events
We present the QCD analysis of D-parameter distribution in near-to-planar
3-jet e+e- annihilation events. We derive the all-order resummed perturbative
prediction and the leading power suppressed non-perturbative corrections both
to the mean value and the distribution. Here non-perturbative corrections are
larger than in 2-jet shape observables, so that higher order non-perturbative
effects could be relevant. Experimental data (not yet available) are needed in
order to cast light on this important point. The technique we develop aims at
improving the accuracy of the theoretical description of multi-jet ensembles,
in particular in hadron-hadron collisions.Comment: 26 pages, 6 figures, JHEP class include
QCD analysis of near-to-planar 3-jet events
Perturbative QCD analysis is presented of the cumulative out-of-plane
momentum distribution in the near-to-planar e+e- annihilation events, K_out <<
Q. In this kinematical region multiple gluon radiation effects become
essential. They are resummed with the single-logarithmic accuracy, which
programme includes the 2-loop treatment of the basic radiation and matching
with the exact O(alpha_s^2) result.
Dedicated experimental analyses of 3-jet event characteristics are of special
interest for the study of the non-perturbative confinement effects.Comment: 32 pages, 1 figure, JHEP class include
Non-perturbative QCD analysis of near-to-planar three-jet events
We present the analysis of the 1/Q-suppressed non-perturbative (NP)
contribution to the cumulative out-of-event-plane momentum distribution in e+e-
annihilation in the near-to-planar three-jet region. It complements our
previous study of the perturbative (PT) distributions resummed to single
logarithmic accuracy. Due to inter-jet soft gluon radiation, the NP
contributions (as well as the PT distributions) are sensitive to the geometry
(the angles between jets) and the colour structure of the underlying hard
process (topology of the three-prong parton antenna). The results and
techniques presented here could be extended to other multi-jet processes and,
in particular, to hadron-hadron collisions.Comment: 53 pages, 4 figures, JHEP class include
Non-perturbative effects in the energy-energy correlation
The fully resummed next-to-leading-order perturbative calculation of the
energy-energy correlation in annihilation is extended to include the
leading non-perturbative power-behaved contributions computed using the
``dispersive method'' applied earlier to event shape variables. The correlation
between a leading (anti)quark and a gluon produces a non-perturbative 1/Q
contribution, while non-perturbative effects in the quark-antiquark correlation
give rise to a smaller contribution . In the back-to-back region,
the power-suppressed contributions actually decrease much more slowly, as small
non-integer powers of 1/Q, as a result of the interplay with perturbative
effects. The hypothesis of a universal low-energy form for the strong coupling
relates the coefficients of these contributions to those measured for other
observables.Comment: 41 pages, LaTeX, 4 figures, uses JHEP.cl
- âŠ