Which element is not created by nuclear fusion in low mass stars?
This depends on what mass stars you mean? But I will answer you question if I can. A red dwarf star is a convective star. And the only element it can create is helium, this is because it is too cool to fuse lithium. We even see some red dwarfs with methane in there atmosphere, but they have collected it from else where it is not a result of fusion in the core. The only other low mass star that is on the main sequence is a very young brown dwarf and these can only burn heavy hydrogen, also known as deterium, but they will still only produce helium. At this stage we have never observed a living brown dwarf because they only burn there heavy helium for a few million years, but we have observed a few dead ones. So in answer to your question no element can be created by a low mass star apart from helium. Try to remember, almost all heavy elements are formed by supernova NOT by stars themselves, most stars just make helium. Yellow dwarfs like are own also produce methane,lithium,nitrogen and carbon. But to make anything else you need to have atleast 1.8 solar masses. I hope this helps. Damon.
Hydrogen cannot be created by fusion in any type of star