I found the answer, it is into the following great article
http://searchhub.org/2011/12/28/why-not-and-or-and-not/
What I did to solve my problem is:
Search by Lucene_KsuDmsDesc = A
Search by Lucene_EmployeeNO = B
Search by Lucene_CreatedBy = C
Search by Lucene_CreatedDateTime = D
Search by Lucene_CategoryID = E
The formula is (A and B and C and D) and (E1 or E2 or .... En), where and = MUST and or = SHOULD