For your research paper I would suggest starting with places in the Bible which forbid the use of sex outside of marriage. For example St. Paul says it is wrong for a man to go with a prostitute because he becomes "one body" with her (1Cor 6:16). That depth of unity can only be truthful in marriage. Jesus teachs the permanence of marriage for the same reason (Mark 10:1-12). Paul includes adulterers and (practicing) homosexuals among those who will not inherit the kingdom of heaven (1 Cor 6:10), altho in the following verse he does indicate they can be forgiven if they repent.
In the case of pedophilia, the fourth commandment is also involved. A pedophile is inevitably deceiving the child's parents and causing him (or her) to do something behind the parent's back. St. Paul talks about the fourth commandment in Ef 6:1. The Bible, by the way, presupposes that children are under their parents authority until the day they marry (not turn 18, like in our culture).
Fr. Phil Bloom
Another letter concerning Pedophilia.
Review of Pedophiles and Priests
Answers to Frequently Asked Questions on Birth Control, Pre-Marital Sex, Dancing, Intimate Touching, Homosexuality, etc.