4 research outputs found
The C parameter distribution in e+e- annihilation
We study perturbative and non-perturbative aspects of the distribution of the
C parameter in e+e- annihilation using renormalon techniques. We perform an
exact calculation of the characteristic function, corresponding to the C
parameter differential cross section for a single off-shell gluon. We then
concentrate on the two-jet region, derive the Borel representation of the
Sudakov exponent in the large-beta_0 limit and compare the result to that of
the thrust T. Analysing the exponent, we distinguish two ingredients: the jet
function, depending on Q^2C, summarizing the effects of collinear radiation,
and a function describing soft emission at large angles, with momenta of order
QC. The former is the same as for the thrust upon scaling C by 1/6, whereas the
latter is different. We verify that the rescaled C distribution coincides with
that of 1-T to next-to-leading logarithmic accuracy, as predicted by Catani and
Webber, and demonstrate that this relation breaks down beyond this order owing
to soft radiation at large angles. The pattern of power corrections is also
similar to that of the thrust: corrections appear as odd powers of Lambda/(QC).
Based on the size of the renormalon ambiguity, however, the shape function is
different: subleading power corrections for the C distribution appear to be
significantly smaller than those for the thrust.Comment: 24 pages, Latex (using JHEP3.cls), 1 postscript figur
Jet Substructure at the Tevatron and LHC: New results, new tools, new benchmarks
In this report we review recent theoretical progress and the latest
experimental results in jet substructure from the Tevatron and the LHC. We
review the status of and outlook for calculation and simulation tools for
studying jet substructure. Following up on the report of the Boost 2010
workshop, we present a new set of benchmark comparisons of substructure
techniques, focusing on the set of variables and grooming methods that are
collectively known as "top taggers". To facilitate further exploration, we have
attempted to collect, harmonise, and publish software implementations of these
techniques.Comment: 53 pages, 17 figures. L. Asquith, S. Rappoccio, C. K. Vermilion,
editors; v2: minor edits from journal revision
HERA and the LHC - A workshop on the implications of HERA for LHC physics: Proceedings Part A
The HERA electron--proton collider has collected 100 pb of data since
its start-up in 1992, and recently moved into a high-luminosity operation mode,
with upgraded detectors, aiming to increase the total integrated luminosity per
experiment to more than 500 pb. HERA has been a machine of excellence
for the study of QCD and the structure of the proton. The Large Hadron Collider
(LHC), which will collide protons with a centre-of-mass energy of 14 TeV, will
be completed at CERN in 2007. The main mission of the LHC is to discover and
study the mechanisms of electroweak symmetry breaking, possibly via the
discovery of the Higgs particle, and search for new physics in the TeV energy
scale, such as supersymmetry or extra dimensions. Besides these goals, the LHC
will also make a substantial number of precision measurements and will offer a
new regime to study the strong force via perturbative QCD processes and
diffraction. For the full LHC physics programme a good understanding of QCD
phenomena and the structure function of the proton is essential. Therefore, in
March 2004, a one-year-long workshop started to study the implications of HERA
on LHC physics. This included proposing new measurements to be made at HERA,
extracting the maximum information from the available data, and
developing/improving the theoretical and experimental tools. This report
summarizes the results achieved during this workshop.Comment: Part A: plenary presentations, WG1: parton density functions, WG2:
Multi-Jet final states and energy flows. 326 pages Part B: WG3: Heavy Quarks
(Charm and Beauty), WG4: Diffraction, WG5: Monte Carlo Tools, 330 page