140 research outputs found
NNNLO correction to the toponium and bottomonium wave-functions at the origin
We report new results of the NNNLO correction to the S-wave quarkonium
wave-functions at the origin, which also provide an estimate of the resonance
cross section in t-tbar threshold production at the ILC.Comment: 5 pages, 2 figures, Proceedings of 2007 International Linear Collider
Workshop: LCWS07 and ILC07, Hamburg, Germany, 30 May - 3 Jun 200
Top quark precision physics at the International Linear Collider
Top quark production in the process at a future
linear electron positron collider with polarized beams is a powerful tool to
determine the scale of new physics. Studies at the \ttbar threshold will
allow for precise determination of the top quark mass in a well defined
theoretical framework. At higher energies vector, axial vector and tensorial CP
conserving couplings can be separately determined for the photon and the
component in the electro-weak production process. The sensitivity to new
physics would be dramatically improved w.r.t. to what expected from LHC for
electroweak couplings.Comment: White paper for Snowmass CSS 201
Intercepts of the non-singlet structure functions
Infrared evolution equations for small- behaviour of the non-singlet
structure functions and are obtained and solved in the
next-to-leading approximation, to all orders in , and including
running effects. The intercepts of these structure functions, i.e.
the exponents of the power-like small- behaviour, are calculated. A detailed
comparison with the leading logarithmic approximation (LLA) and DGLAP is made.
We explain why the LLA predictions for the small- dependence of the
structure functions may be more reliable than the prediction for the
dependence in the range of explored at HERA.Comment: 26 pages, LaTeX, 5 Postscript figure
Supersymmetric Corrections to the Threshold Production of Top Quark Pairs
In this paper we investigate supersymmetric effects to the threshold
production cross section of top quark pairs in electron positron annihilation.
In particular, we consider the complete one-loop corrections from the strong
and weak sector of the Minimal Supersymmetric Standard Model.Comment: 18 pages, 7 figure
The nature of power corrections in large approximation
We investigate the nature of power corrections and infrared renormalon
singularities in large approximation. We argue that the power
correction associated with a renormalon pole singularity should appear at O(1),
in contrast to the renormalon ambiguity appearing at , and give
an explanation why the leading order renormalon singularities are generically
poles.Comment: 6 page
NNNLO results on top-quark pair production near threshold
We present new results on the NNNLO top-antitop production cross section near
threshold from potential and ultrasoft gluon corrections. The new
non-logarithmic third-order terms are in the 10% range and lead to a
significant reduction in the theoretical error.Comment: 6 pages, to appear in the proceedings of 8th International Symposium
on Radiative Corrections (RADCOR 2007), Florence, Italy, October 1-
Third-order Coulomb corrections to the S-wave Green function, energy levels and wave functions at the origin
We obtain analytic expressions for the third-order corrections due to the
strong interaction Coulomb potential to the S-wave Green function, energy
levels and wave functions at the origin for arbitrary principal quantum number
n. Together with the known non-Coulomb correction this results in the complete
spectrum of S-states up to order alpha_s^5. The numerical impact of these
corrections on the Upsilon spectrum and the top quark pair production cross
section near threshold is estimated.Comment: 24 pages, LaTeX, v2: eq.(30) corrected (-13/8->-15/8
Ultrasoft contribution to heavy-quark pair production near threshold
We compute the third-order correction to the heavy-quark current correlation
function due to the emission and absorption of an ultrasoft gluon. Our result
supplies a missing contribution to top-quark pair production near threshold and
the determination of the bottom quark mass from QCD sum rules.Comment: 10 pages, LaTe
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