content_image/323039.jpg
<img src='content_image/323039.jpg'>

and the angle with respect to the reaction plane φ . Older, lower statistics data is sometimes reported as R$_{AA}$ ( N$_{part}$ ), although [191] demonstrated its limited utility. 

R$_{AA}$ is a nice quantity to work with as it displays the effect of nuclear col- lisions at a glance: R$_{AA}$ = 1 means no modification from trivially scaled p + p collisions, R$_{AA}$ > 1 means enhancement, and R$_{AA}$ < 1 means suppression. For this reason, R$_{AA}$ is known as the nuclear modification factor. When the partonic production spectra are power laws of approximately constant power, which is the case at Rhic and $_{Lhc}$, R$_{AA}$ is approximately given by an espe- 

