Send in the cavalry! The NYPD has moved three elite Manhattan homicide detectives and a deputy chief to the raucous Occupy Wall Street protest in response to a rash of sex attacks, thefts and vandalism -- including graffiti scrawled on the nearby 9/11 Memorial, The Post has learned. The veteran detectives, normally assigned to Manhattan South, are now working cases at Zuccotti Park on an as-needed basis, law-enforcement sources said.