There's no definitive answer to the question of the longest research paper title. There's no central registry tracking this metric, and what constitutes a "research paper" can be subjective (e.g., does it include theses, dissertations, or only journal articles?).
Furthermore, titles are often artificially lengthened by adding numerous authors or affiliations. Therefore, any claim to have found the longest title would be difficult to verify and likely depend on the specific criteria used.