If (and only if) you hold a CERN-TH contract (Staff, Fellow, Scientific Associate) or are a CERN-TH emeritus you should display the affiliation:
Theoretical Physics Department, CERN, Geneva, Switzerland
Any article authored by Staff, Fellows, Emeriti or Scientific Associates in TH should have a CERN-TH preprint number. It can be obtained using the following application form (in case of problems contact the TH secretariat ). You should ask for a preprint number only when your article is close to completion. Do not forget to include your generated CERN-TH preprint number on the first page of your paper.
Any registered visitor to CERN-TH who is here for 2 months or more, may also (and is encouraged to) issue CERN-TH preprints for articles describing research carried out entirely, or to a large extent, at CERN. The Department Head may occasionally relax the restriction on the duration of stay. Visitors (other than Scientific Associates) should not use a CERN-TH affiliation.
Preprint numbers are not normally issued after departure of the author(s) from CERN. However, if you do not manage to complete a paper before leaving, you can ask for a preprint number for another two weeks after departure at most.
TH Staff members will always be happy to discuss the content or presentation of a paper, but their formal approval is not required. TH preprints are required to be written in good English (British spelling).
The Theoretical Physics Department has no budget to cover publication or reprint charges, however CERN does have an agreement with most journals that CERN articles are published as open access.