Paarproduktion schwerer Quarks in e+ e- -Kollisionen: QCD-Strahlungskorrekturen für die Quark-Antiquark-Beiträge zur Ordnung alpha s 2

In this thesis the QCD corrections to second order in the strong coupling constant, i.e. to order alpha_s^2, for the process e^+ e^- -> Q Qbar are calculated. These are important contributions to the differential cross section of the reaction e^+ e- -> Q Qbar + X. The decay amplitude of a virtual Z-boson into a heavy quark anti-quark pair is decomposed into four dimensionless form factors which are extracted from the decay amplitude with appropriate projectors. The resulting 1- and 2-loop integrals are reduced to linear combinations of known master integrals with integration-by-parts and Lorentz-invariance identities. The ultraviolett divergences are renormalized using a hybrid scheme in which the gluon wavefunction and the strong coupling constant are renormalized using the modified minimal subtraction scheme (MSbar) while the onshell-scheme (OS) is used for the quark wavefunction and the quark mass. The renormalized form factors are then analytically continued above the production threshold of the heavy quark pair and decomposed into real and imaginary parts. These results are expanded near the production threshold and for asymptotic high center-of-mass energies. Then the contributions to the form factors involving the so-called Adler-Bell-Jackiw triangle anomaly are inspected. These contributions are calculated for four combinations for the internal and external mass using the methods descripted above and an appropriate finite renormalization. The consistancy of these results is checked by calculating the limit of vanishing quark mass. Again the results are analytically continued obeying the different production thresholds and the Landau-Yang theorem. The resulting real and imaginary parts are then expanded near threshold and for asymptotic high energies. The validity of the used scheme for the treatment of the parity violating neutral current couplings in dimensional regularization is proofed by the relevant Ward identities. Using the calculated 1- and 2-loop contributions to the form factors predictions for the static anomalous magnetic moment and the weak axial vector charge of a heavy quark are made, which can be checked at a high energetic e^+ e^- collider.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2005

Author dc:creator

• Leineweber, Thilo

Contributors dc:contributor

• Bernreuther, Werner

• info:eu-repo/classification/ddc/530
• Elektron-Positron-Vernichtung
• t-Quark
• Paarerzeugung
• Quantenchromodynamik
• Strahlungskorrektur
• Physik

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123706%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:62113