English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We consider pair production and decay of fundamental unstable particles inthe framework of a modified perturbation theory (MPT), which treats resonantcontributions of unstable particles in the sense of distributions. Thecross-section of the process is calculated within the NNLO of the MPT in amodel that admits exact solution. Universal massless-particles contributionsare taken into consideration. The calculations are carried out by means ofFORTRAN code with double precision, which ensures per mille accuracy ofcomputations. A comparison of the outcomes with the exact solution reveals anexcellent convergence of the MPT series at the energies close to and above themaximum of the cross-section. Near the maximum of the cross-section thediscrepancy of the NNLO approximation makes up a few per mille.

Unstable-particles pair production in modified perturbation theory in NNLO