It works for me... but I guess you wanted to research Heavy Plasma even without having one at the base?
If so, you need to remove the dependency on the object itself (see attached screenshots how the dependencies look like with your ruleset).
If you didn't know, when modding an existing thing, you don't redefine it completely, you only change attributes you specify in a mod and the rest stays.
Adding:
needItem: false
to your STR_HEAVY_PLASMA research rules should help... but somehow it gets ignored?? Don't know why...
When I commented out the "needItem: true" in the original research.rul file, it worked... maybe some more experienced modders can help, I never did any more complicated ruleset modding.