The "Shoulder" and the "Ridge" in PHENIX

Understand

The observation of jet quenching in ultra-relativistic heavy ion collisions demonstrates significant energy loss of fast partons when passing through the created medium.

• Correlations between final-state particles at intermediate transverse momentum (1.0 $\lesssim$ $p_{T}$ $\lesssim$ 4.0 GeV/$c$) allow for study of the medium and its response to deposited energy.
• Comparison of these measurements in heavy ion collisions with measurements in proton collisions show strong modification of the correlation shape and particle yields.
• Two new structures are created, both extended in $\Delta\eta$, one centered at $\Delta\phi=0$ (``ridge'') and the other occurring at $\Delta\phi\approx\pi\pm1.1$ (``shoulder'').