A table not mapped in hibernate

I put the question before but as i'm new with the site i found problems writing my question. Well. I'm working on two projects: Create an EJB project and a webapp. In both i have to store information from the webapp into a database. The first one has worked. In the seconde, i am getting this error

org.hibernate.hql.internal.ast.QuerySyntaxException: Enseignants is not mapped

Here is a part of my classes

@Stateless(name = "ENIT")
public class EnitImpl implements EnitLocal {
@PersistenceContext(unitName = "tp3")
private EntityManager em  ;
public EnitImpl() {
    // TODO Auto-generated constructor stub
}
public void addCours(Cours cour) {
    // TODO Auto-generated method stub
    em.merge(cour);
}
public List<Cours> consulterCours() {
    // TODO Auto-generated method stub
    Query req = em.createQuery("Select c from cours c ");
    return req.getResultList();
}
@TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
public Cours consulter(int id) {
    // TODO Auto-generated method stub
    Cours cours = em.find(Cours.class, id);
    if (cours == null)
        throw new RuntimeException("Cours inexistant");
    return cours;
}
public void addProf(Enseignant E) {
    // TODO Auto-generated method stub
    em.merge(E);
}
public List<Enseignant> consulterProf() {
    Query req = em.createQuery("Select p from enseignants p ");
    return req.getResultList();
}
@TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
public Enseignant consulterP(int id) {
    Enseignant E = em.find(Enseignant.class, id);
    if (E == null)
        throw new RuntimeException("Enseignant non trouvé");
    return E;
}
}

And the interface:

@Local
public interface EnitLocal {
public void addProf(Enseignant E);
public List<Enseignant> consulterProf();
public Enseignant consulterP(int id);
public void addCours(Cours C);
public List<Cours> consulterCours();
public Cours consulter(int id);
}

When I debug the program, em is null. I was using em.persist() but it didn't work. So i've used em.merge(). The diffrence between this project and the old one is that here I've this join 'ManyToOne'. Can someone see the problem?