From Particle Data Book From Particle Data Book

From Particle Data Book

From Particle Data Book and white paper

2 Ge. V

Ways to Reveal the QGP properties---RAA • nuclear modification factor (RAA): RAA ( or Rd. A) No medium effect

Cold Nuclear Effect • Mostly referring to initial state effect, i. e. the effect before the hard collision happens. – Color Glass Condensate: "Color" in the name "color glass condensate" refers to a type of charge that quarks and gluons carry as a result of the strong nuclear force. The word "glass" is borrowed from the term for silica and other materials that are disordered and act like solids on short time scales but liquids on long time scales. In the "gluon walls, " the gluons themselves are disordered and do not change their positions rapidly because of time dilation. "Condensate" means that the gluons have a very high density (from Wikipedia) – EMC: single nucleons and nucleons inside an nucleus have a different distribution of momentum among their component quarks. • Shadowing – Initial state energy loss: e. g. gluon fragment into hardons before the hard collision. – Cronin effect: multiple scatter of projectile partons with the partons in the target nuclear • There’re also final state effect, e. g. – co-mover effect, i. e. After QGP freezout into hardonic phase, the signal particle, e. g. J/psi still can be reduced via collision with those hadrons.

Au + Au Experiment (200 Ge. V) Final Data Energy loss: parton loss lots of energy (d. E/dx = ? ? ? Ge. V/fm) through bremsstrahlung when pass through the new state of matter (final state effect) d + Au Control Experiment (200 Ge. V) Preliminary Data Cronin enhancement: parton p. T smearing from random kick before collisions (i. e. initial state effect)

Direction photon • Strength of EM interaction is ~10^4 -10^6 smaller than the strong interaction. • Photon is invisible to the QGP. • They are affected by the cold nuclear effect, i. e. initial state effect.