It is all the more remarkable in that, unlike the earlier cases, the particle claims from the LHC have not yet been put into writing. “This is all based on the live webcast from the CERN event,” Ginsparg says. Submissions to arXiv made after 16.00 US Eastern Standard Time each day do not appear until the following day — a cut-off time set by arXiv’s operators — and the timing of the submissions shows that physicists are rushing to e-mail in their papers just before this deadline, Ginsparg adds.
It's a variation of "send in," "mail in." They're phrasal variations of the single-word verbs, "send" and "mail." To "e-mail" and "e-mail in" are the same thing.
send it = send it in
mail it = mail it in
e-mail it = e-mail it in