indigomadelin Its not a research paper but if you take the time to read googles terms and conditions Here that does pretty much detail things, its not like they are secret about what they do its just that most people dont take the time to read and understand the terms and conditions, focusing instead on the convienence i guess.
The guts of it is they record, monitor and analyse mostly everything they can from the services of theres that you interact with, and you licence your intellectual property to them to be analysed and shared with 3rd party contractors as they see fit.... Essentially.