What type of Scientist...

[FranziPantz]

I'm writing a story in which a scientist finds her way to the realm of the dead. The realm is a place that exists "behind" our world, on another plane of existence. One accesses this place by entering a different state of being rather than going through any sort of portal.

What kind of scientist would make this kind of discovery? Which scientific discipline?

[alexanderd]

would have to be a physicist I would think

[factor-fiction]

Hypnotist/Psychiatrist?

[ChuckFickens]

http://www.sleepforscience.org/

I would guess is the most likely to enter a different state (unless you mean Kansas)

[tommy-h]

anthropologhist

[Quassia]

Through a dream like state? ... http://en.wikipedia.org/wiki/Oneirology

[factor-fiction]

Welcome to AB, FranziPantz. Were you a Kenny fan? (We used to have a user called FancyPants.)

[chakka35]

There is no 'science discipline' that covers such stuff. You need the R&S site, not this one.

[bibblebub]

a string theoretician

[Old_Geezer]

Spiritual issues are not the domain of science, which deals with this material reality. Since you are writing fiction just pick a discipline. You'll get criticized whichever you choose. Or opt for a non-scientist who happens to stumble upon this. Or maybe a medium or psychic.