I, too, have been looking for Hassans from Derry. I am trying trace my great great grandmother's roots in Derry Ireland. According to her obituary she was related the John Cardinal McCloskey of NY. His mother was Elizabeth Hassan of Coolnamonan, Banagher Derry Ireland. I have researched records for both McCloskey and Hassan to no avail. Unfortunately, there are not many records in existence. I am now hoping to make a link with someone online that may have some family stories. If I could figure out who Elizabeth Hassan's siblings and/or parents were, I might be able to make the connection with McCloskeys. If you have any information that might be useful, please let me know.
Regarding your inquiry, I know that in the 1831 Irish Census there were 15 Hassans of 28 households in Coolnamonan. The names were Patrick, James, John, Manus, Patrick, Thomas, Thomas, Hugh, Michael, Widow, Peter, HEnry, Thomas, James, and John. Griffiths Valuation of 1858 shows 11 Hassans in Coolnamonan: James (Jonny), James (Tonry Due), John, Patrick, Thomas, Michael (Jack Roe), Nelus, Alick, John, Michael (Roe), and James (tailor).