References to Study the New Matter

1. References to Study the New Matter

2. Study QGP in different Centrality Most Central events (highest multiplicity), e.g. top 5% central, i.e. 5% of the events with largest multiplicity Mid Central events Most Peripheral events From most central to most peripheral event, the collision is more like a p+p collisions. One can also collision smaller size of nuclear, e.g. Cu+Cu, Si+Si, instead of Au+Au to gain more luminosity. Centrality can be quantified by the number of collisions (N_coll) and number of participants (N_part) through the glauber model calculation with N_coll: 8 N_part: 6

3. 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.

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

5. Add fragmentation to hadrons D(z) – fractional momentum dist. of particles created by outgoing quark or gluon (i.e. in a jet) pQCD – Single Hadron Production Phys. Rev. Lett. 91, 241803 (2003) data vs pQCD KKP Kretzer Slides from B. Cole Talk

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

8. q q PHENIX: Au-Au Final Results from 2002 RAA • Unequivocal observation of strong suppression at high p in central Au-Au collisions. p (GeV/c) Slides from B. Cole Talk

10. RAA(, pT) • Rather than separating v2, RAA(pT) plot RAA(, pT)

11. Pair Production from Gluon Field • Suppose we pull quark & anti-quark apart ? • Store energy in gluon field • Eventually enough energy to produce pair. • Get two shorter flux tubes. • Continue until energy of outgoing quarks is exhausted • “Fragmentation” • Jet:

12. Number of pairs q q 0º 180º Angle between high energy particles STAR Experiment: “Jet” Observations proton-proton jet event Analyze by measuring (azimuthal) angle between pairs of particles • In Au-Au collisions we see only one “jet” at a time ! • How can this happen ? • Jet quenching! Slides from B. Cole Talk

13. 1 < pT (assoc) < 2.5 GeV/c trigger Adler et al., PRL90:082302 (2003), STAR away-side near-side What’s a shock wave? SHOCK WAVE is a thin transitive area propagating with supersonic speed in which there is a sharp increase of density, pressure and speeds of substance. http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=21