2,031 research outputs found
Precision determination of the top-quark mass
Precision determinations of the top-quark mass require theory predictions
with a well-defined mass parameter in a given renormalization scheme. The
top-quark's running mass in the MSbar scheme can be extracted with good
precision from the total cross section at next-to-next-to-leading order in QCD.
The Monte Carlo top-quark mass parameter measured from comparison to events
with top-quark decay products is not identical with the pole mass. Its
translation to the pole mass scheme introduces an additional uncertainty of the
order of 1 GeV.Comment: Presented at Loops and Legs in Quantum Field Theory 2014, Weimar,
Germany and Large Hadron Collider Physics 2014, New York, US
NNLO Time-like Splitting Functions in QCD
We review the status of the calculation of the time-like splitting functions
for the evolution of fragmentation functions to the next-to-next-to-leading
order in perturbative QCD. By employing relations between space-like and
time-like deep-inelastic processes, all quark-quark and the gluon-gluon
time-like splitting functions have been obtained to three loops. The
corresponding quantities for the quark-gluon and gluon-quark splitting at this
order are presently still unknown except for their second Mellin moments.Comment: 4 pages LaTeX, proceedings of the DIS 2008 Workshop, 7-11 April 2008,
Londo
Fuchsia and Master Integrals for Energy-Energy Correlations at NLO in QCD
In this talk we discuss some aspects of the analytical calculation of energy
correlations in electron-positron annihilation at a next-to-leading order in
QCD. Our primary focus is on the most difficult task: the calculation of master
integrals for real-emission contributions, which are functions of two
dimensionless variables and the dimensional regulator. We use a method of
differential equations and their so-called epsilon-form which is constructed
with the help of the Fuchsia program based on Lee's algorithm.Comment: 11 pages, 1 figure. Presented at Matter to the Deepest Conference in
Podlesice (Poland) 3-8 Sep 2017 and at RADCOR Conference in St. Gilgen
(Austria) 24-29 Sep 201
On threshold resummation beyond leading 1-x order
We check against exact finite order three-loop results for the non-singlet
F_2 and F_3 structure functions the validity of a class of momentum space
ansaetze for threshold resummation at the next-to-leading order in 1-x, which
generalize results previously obtained in the large-\beta_0 limit. We find that
the ansaetze do not work exactly, pointing towards an obstruction to threshold
resummation at this order, but still yield correct results at the leading
logarithmic level for each color structures, as well as at the
next-to-next-to-leading logarithmic level for the specific C_F^3 color factor.
A universality of the leading logarithm contributions to the physical evolution
kernels of F_2 and F_3 at the next-to-leading order in 1-x is observed.Comment: v1:18 pages; v2: 26 pages, expanded version with new results for the
F_3 structure function and added references; v3: more concise sections 3 and
4, improved discussion in section 5, added references, to be published in
JHE
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