  We derive an analytical form for flow-background to jet-like azimuthal
correlation in a cluster approach. We argue that the elliptic flow parameter to
use in jet-correlation background is that from two-particle method excluding
non-flow correlation unrelated to the reaction plane, but including cross-terms
between cluster correlation and cluster flow. We verify our result with Monte
Carlo simulations. We discuss implications of our finding in the context of
jet-like correlations from STAR and PHENIX.
