Addressing the physics of the ridge by 2- and 3-particle correlations at STAR

We present new results on 2-particle azimuthal (∆φ) correlation relative to event plane and 3particle pseudorapidity (∆η) correlation at mid-rapidity in Au+Au collisions at √ sNN = 200 GeV, measured by the STAR experiment. While jet-like correlation is symmetric, ridge is found to be asymmetric when trigger particle azimuth is between inand out-of-plane. The charge ordering properties between associated and trigger particles are exploited to separate jet-like and ridge contributions in 3-particle ∆η-∆η correlations. We found that like-sign triplets are dominated by ridge. The separated ridge, while narrow in ∆φ, is extremely broad in ∆η. The ridge particles are not only uncorrelated to the trigger particle in ∆η, but also uncorrelated between themselves.