21 research outputs found
Loopedia, a Database for Loop Integrals
Loopedia is a new database at loopedia.org for information on Feynman
integrals, intended to provide both bibliographic information as well as
results made available by the community. Its bibliometry is complementary to
that of SPIRES or arXiv in the sense that it admits searching for integrals by
graph-theoretical objects, e.g. its topology.Comment: 16 pages, lots of screenshot
Master Integrals for the two-loop, non-planar QCD corrections to top-quark pair production in the quark-annihilation channel
We present the analytic calculation of the Master Integrals for the two-loop,
non-planar topologies that enter the calculation of the amplitude for top-quark
pair hadroproduction in the quark-annihilation channel. Using the method of
differential equations, we expand the integrals in powers of the dimensional
regulator and determine the expansion coefficients in terms of
generalized harmonic polylogarithms of two dimensionless variables through to
weight four.Comment: 28 pages, 2 figures, ancillary files include
Standard Model Theory for the FCC-ee Tera-Z stage
The future 100-km circular collider FCC at CERN is planned to operate in one
of its modes as an electron-positron FCC-ee machine. We give an overview
comparing the theoretical status to the experimental demands of one of four
foreseen FCC-ee operating stages, Z-boson resonance energy physics, called the
FCC-ee Tera-Z stage for short. The FCC-ee Tera-Z will deliver the highest
integrated luminosities as well as very small systematic errors for a study of
the Standard Model (SM) with unprecedented precision. In fact, the FCC-ee
Tera-Z will allow the study of at least one more perturbative order in quantum
field theory compared to the LEP/SLC precision. The real problem is that the
present precision of theoretical calculations of the various SM observables
does not match that of the anticipated experimental measurements. The
bottle-necks to overcoming this situation are identified. In particular, the
issues of precise QED unfolding and the correct calculation of SM
pseudo-observables are critically reviewed. In an Executive Summary, we specify
which basic theoretical calculations are needed to meet the strong experimental
expectations at the FCC-ee Tera-Z. Several methods, techniques and tools needed
for higher-order multi-loop calculations are presented. By inspection of the
Z-boson partial and total decay width analyses, it is argued that at the
beginning of operation of the FCC-ee Tera-Z, the theory predictions may be
tuned to be precise enough not to limit the physics interpretation of the
measurements. This statement is based on anticipated progress in analytical and
numerical calculations of multi-loop and multi-scale Feynman integrals and on
the completion of two-loop electroweak radiative corrections to the SM
pseudo-observables this year. However, the above statement is conditional as
the theoretical issues demand a very dedicated and focused investment by the
community.Comment: Published versio
Mixed EW-QCD two-loop amplitudes for and scheme independence of multi-loop corrections
We perform a dedicated study of the -initiated two-loop
electroweak-QCD Drell-Yan scattering amplitude in dimensional regularization
schemes for vanishing light quark and lepton masses. For the relative order
and one-loop Standard Model corrections, details of our
comparison to the original literature are given. The infrared pole terms of the
mixed two-loop amplitude are governed by a known generalization of the dipole
formula and we show explicitly that exactly the same two-loop polarized hard
scattering functions are obtained in both the standard 't
Hooft-Veltman-Breitenlohner-Maison scheme and Kreimer's
anticommuting scheme.Comment: 65 pages, 6 figures; ancillary files with result