3,603 research outputs found
The status of NLL BFKL
This talk summarises the current status of the NLL corrections to BFKL
physics and discusses the question of small-x factorisation.Comment: 4 pages, 2 figures. Uses moriond.sty (included). Talk presented at
the XXXVth Rencontres de Moriond, QCD and High Energy Hadronic Interactions,
Les Arcs, France, March 18-25, 200
A resummation of large sub-leading corrections at small x
The NLL corrections to the BFKL kernel are known to be very large, to the
extent that even for small values of alpha_s, they lead to physical cross
sections which are not positive definite. It is shown in the context of a toy
model, that such pathological behaviour is an artifact of the truncation at NLL
order, and is associated in particular with double transverse logarithms. These
are resummed in a manner consistent with the full NLL kernel, and are shown to
change its properties quite considerably.Comment: 19 pages LaTeX, 5 figures, includes JHEP.cls and cite.sty. Version 2
additionally includes an appendix, numerous clarifications, correction of
typos and extra reference
Soft emissions and the equivalence of BFKL and CCFM final states
This article demonstrates that the BFKL and CCFM equations, despite their
different physical content, lead to equivalent results for any final-state
observable at leading single-logarithmic order. A novel and fundamental element
is the treatment also of the soft (z->1 divergent) part of the splitting
function in the CCFM equation.Comment: 18 pages, 7 figures. Version 2 contains a few extra sentences to
emphasise that the equivalence applies to the predictions from the equation
Fall and rise of the gluon splitting function
This talk reviews some recent results on the NLL resummed small-x gluon
splitting function, as determined including renormalisation-group improvements.
It also discusses the observation that the LO, NLO, NNLO, etc. hierarchy for
the gluon splitting function breaks down not when (alpha_s log 1/x) is of order
one but rather for (alpha_s log^2 1/x) of order one.Comment: 7 pages, 3 figures; Talk presented at DIS 2004, Strbske Pleso,
Slovakia, April 2004, and at the Eighth Workshop on Non-Perturbative Quantum
Chromodynamics, Paris, France, June 200
Resummation of the jet broadening in DIS
We calculate the leading and next-to-leading logarithmic resummed
distribution for the jet broadening in deep inelastic scattering, as well as
the power correction for both the distribution and mean value. A truncation of
the answer at NLL accuracy, as is standard, leads to unphysical divergences. We
discuss their origin and show how the problem can be resolved. We then examine
DIS-specific procedures for matching to fixed-order calculations and compare
our results to data. One of the tools developed for the comparison is an NLO
parton distribution evolution code. When compared to PDF sets from MRST and
CTEQ it reveals limited discrepancies in both.Comment: 48 pages, 7 figure
- …