What is the word used to describes someone who is involved in something and not aware of what is going on around them?

Word_used_to_describes_someone_who_is_involved_in_something_and_not_aware_of_what_is_going_on_around_them">http://wiki.answers.com/Q/What_is_the_Word_used_to_describes_someone_who_is_involved_in_something_and_not_aware_of_what_is_going_on_around_them"