What research is there on tea preparation?
The making of tea is a balance between three factors that affect how the flavours of the leaves are infused into the water: time, temperature, and the ratio of leaf surface area to water.

Generally, more of any one of those parameters is balanced by less of the others.
The temperature,however, has a specific minimum requirement, below which certain things simply won't occur. This is why black tea must be made with the water starting at the boiling point, and not at 70 degrees.

As for precision, the problem is mostly defining the result, not the conditions. How do you define a good cup of tea in a way that is measurable and repeatable?

Practically speaking, I find that the different traditions in each tea-drinking culture are a very good starting point to work from. After that, you can adjust and experiment all you want. Remember that traditions can vary from "one for each cup and one for the pot" to the intricacies of a full Japanese tea ceremony.