From what I have read it seems the different branches seem to treat the subject quite different. While Mahayana texts seem to avoid directly touching the subject and only describe the effects, the Theravāda tradition seems almost obsessed with Jhāna.
Are there really such big differences?
The word jhāna is Pali, so it stands to reason you wouldn't hear about it directly in other traditions. What you should be looking for are the following:
Sanskrit: dhyāna
Chinese: Chán (simplified Chinese: 禅; traditional Chinese: 禪)
Japanese: Zen (禅)
As far as differences go, I'm not sure which you are referring to, but I once skimmed through a collection of modern Buddhist writings on samadhi and found that none of the authors seemed able to agree on what meditation or jhāna meant. It differs from monastery to monastery, let alone tradition to tradition.