As i read in documentation I'm allowed to use EL in queries.
So supported with this article :
http://www.hibernate.org/hib_docs/entitymanager/reference/en/html/queryhql.html
i produced the following piece of code
User existing = (User) em.createQuery("SELECT OBJECT(u) FROM User u WHERE u.login=#{newUser.login} AND u.passwdHash=#{newUser.passwdHash}").getSingleResult();
Read the contract of getSingleResult() (No).