Just now noticed an article (physics paper) with 5,154 authors.

Surprisingly, Only the first nine pages in the 33-page article, published on 14 May 2015 in Physical Review Letters, describe the research itself — including references. The other 24 pages list the authors and their institutions.

Seems like you want to broke the record for the largest number of contributors to a single research article.

BTW, this paper is available for free under the Creative Commons License, you may read it for yourself.

Article Combined Measurement of the Higgs Boson Mass in $pp$ Collisi...