No Visa Needed to enter the USA - Residents of 38 contries do not require a visa. See details of the Visa Waiver Program at
https://en.wikipedia.org/wiki/Visa_Waiver_Program
Visa Needed to enter the USA - For other attendees not not eligible via the Visa Waiver Program, the Visa Waiver-Business (WB) or B-1 visa will be appropriate for attending or speaking at the collaboration meeting. You can apply for a visa waiver online through the ESTA website. It is valid for two years from the date of application.
https://esta.cbp.dhs.gov/esta/
For more information about the B-1 (or B-1/B-2 combined visa), please refer to the U.S. State Department.
https://travel.state.gov/content/visas/en/visit/visitor.html
