Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Modified perturbation theory approach for tt-bar production and decay   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 $e^+e^- \to (\gamma,Z) \to t\bar t \to
W^{+}b:W^{-}\bar b$. 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.

15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
24
The categories of this paper are: dg-ga
23
The categories of this paper are: solv-int