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arXiv · hep-ph/0207215

Modified perturbation theory approach for tt-bar production and decay

M. L. Nekrasov
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Abstract

The modified perturbation theory (MPT), based on direct expansion of probabilities instead of amplitudes, allows one to avoid divergences in the phase-space integrals resulting from production and decay of unstable particles. In the present paper the range of applicability of MPT is determined numerically in the case of the process $e^+e^- \to (γ,Z) \to t\bar t \to W^{+}b:W^{-}\bar b$. It is shown that with the complete expansion in powers of the coupling constant (without Dyson resummation) MPT operates best at the energies located near the maximum of the cross-section and slightly above the maximum. In this region the MPT expansion within the next-to-leading order considerably exceeds in accuracy well-known DPA approach.

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M. L. Nekrasov. 2002-07-18. Modified perturbation theory approach for tt-bar production and decay. https://doi.org/10.1016/s0370-2693(02)02549-2

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