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On the threshold behaviour of heavy top production

Sjöstrand, Torbjörn LU orcid (2026) 2025 QCD at the Extremes, QCDEX 2025 508.
Abstract

The observation of an excess of tt production in the threshold region, by CMS and ATLAS, has been interpreted as a toponium contribution, i.e. from below-threshold tt virtual states. The news here is the nontrivial experimental extraction of such a signal, not its existence as such. Indeed, already 35+ years ago an NRQCD Green’s function approach was used to model the above- and below-threshold production of tt pairs in pp/pp collisions. The relevant cross section equations from that study are now (re-)implemented in the Pythia 8 event generator. While the above-threshold part is straightforward, the physical interpretation and modelling of below-threshold events is nontrivial, and a final prescription is cross-checked against two... (More)

The observation of an excess of tt production in the threshold region, by CMS and ATLAS, has been interpreted as a toponium contribution, i.e. from below-threshold tt virtual states. The news here is the nontrivial experimental extraction of such a signal, not its existence as such. Indeed, already 35+ years ago an NRQCD Green’s function approach was used to model the above- and below-threshold production of tt pairs in pp/pp collisions. The relevant cross section equations from that study are now (re-)implemented in the Pythia 8 event generator. While the above-threshold part is straightforward, the physical interpretation and modelling of below-threshold events is nontrivial, and a final prescription is cross-checked against two simpler ones. Cross sections and some event properties are presented.

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Please use this url to cite or link to this publication:
author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
host publication
Proceedings of Science
volume
508
conference name
2025 QCD at the Extremes, QCDEX 2025
conference location
Virtual, Online
conference dates
2025-09-01 - 2025-09-05
external identifiers
  • scopus:105038439124
DOI
10.22323/1.508.0002
language
English
LU publication?
yes
id
1a031593-9824-4ba9-92f5-6129c0d17b59
date added to LUP
2026-08-17 13:21:59
date last changed
2026-08-17 13:22:27
@inproceedings{1a031593-9824-4ba9-92f5-6129c0d17b59,
  abstract     = {{<p>The observation of an excess of tt production in the threshold region, by CMS and ATLAS, has been interpreted as a toponium contribution, i.e. from below-threshold tt virtual states. The news here is the nontrivial experimental extraction of such a signal, not its existence as such. Indeed, already 35+ years ago an NRQCD Green’s function approach was used to model the above- and below-threshold production of tt pairs in pp/pp collisions. The relevant cross section equations from that study are now (re-)implemented in the Pythia 8 event generator. While the above-threshold part is straightforward, the physical interpretation and modelling of below-threshold events is nontrivial, and a final prescription is cross-checked against two simpler ones. Cross sections and some event properties are presented.</p>}},
  author       = {{Sjöstrand, Torbjörn}},
  booktitle    = {{Proceedings of Science}},
  language     = {{eng}},
  title        = {{On the threshold behaviour of heavy top production}},
  url          = {{http://dx.doi.org/10.22323/1.508.0002}},
  doi          = {{10.22323/1.508.0002}},
  volume       = {{508}},
  year         = {{2026}},
}