JPA 2.0 section 3.8.6 Query Execution:

"
Query and TypedQuery methods other than the executeUpdate method are not required to be invoked within a transaction context, unless a lock mode other than LockModeType.NONE has been specified for the query. In particular, the getResultList and getSingleResult methods are not required to be invoked within a transaction context unless such a lock mode has been specified for the query.[47] If an entity manager with transaction-scoped persistence context is in use, the resulting entities will be detached; if an entity manager with an extended persistence context is used, they will be managed. See Chapter 7 for further discussion of entity manager use outside a transaction and persistence context types.
"

AS7-2781 has a test case that demonstrates that this doesn't happen (the Query is currently commented out).