A common description of jet-quenching and elliptic flow within a pQCD transport model Oliver Fochler H-QM Graduate Day arXiv:

Oliver Fochler present (near) future

Oliver Fochler

A perfect liquid? PRL 92, (2004) Universal bound from AdS/CFT? viscous hydro ideal hydro

Oliver Fochler nuclear modification factor relative to pp (binary collision scaling) experiments show approx. factor 5 of suppression in hadron yields Strong jet-quenching high energy particles as probes of the medium created in AA-collisions HP 2008, C. Vale

Oliver Fochler Some jet-quenching schemes BDMPS (Baier, Dokshitzer, Mueller, Peigne, Schiff) GLV (Gyulassy, Levai, Vitev) - opacity expansion  Djordjevic, Wicks, Horowitz, Adil.. ASW (Armesto, Salgado, Wiedemann) - path integral in opacity  Dainese, Loizides, Paic, Eskola, Honkanen, Renk, Ruppert AMY (Arnold, Moore, Yaffe) - finite temp. field theory  Qin, Turbide, Jeon, Gale, Ruppert HT, Higher-Twist (Wang, Guo) - twist power expansion in DIS  Zhang, Zhang, Majumder, Fries, Mueller

Oliver Fochler Partonic transport model – BAMPS microscopic transport simulations with full dynamics  attack various problems within one model (thermalization, R AA, jet tomography, v 2, initial conditions,...) BAMPS = Boltzmann Approach to Multiple Particle Scattering, (Z. Xu, C. Greiner, Phys. Rev. C71)

Oliver Fochler Partonic transport model - BAMPS LO pQCD cross sections calculate transition probabilities for (test)particles within spatial cells  no geometric interpretation of cross sections simulate gluon plasma including the processes gg  gggg  ggg VV transition probabilities matrix element integrated over momentum space gg  gg cross section (in small-t (small angle) approximation)

Oliver Fochler LPM-effect obtain total cross section for gg  ggg via integration of the matrix element possible interference effects cannot be treated in quasi particle picture  incoherent treatment of gg  ggg processes  parent gluon must not scatter during formation time of emitted gluon discard all possible interference effects (Bethe-Heitler regime) Gunion-Bertsch matrix element

Oliver Fochler Reference frames for the LPM cut-off ktkt CM frame p1p1 p2p2 lab frame ktkt  = 1 / k t total boost integral cuts  ‘ << 1 (e.g. thermal particles):

Oliver Fochler Au+Au – Setup central (b=0 fm) Au-Au collision at 200 AGeV sampling of initial gluon plasma:  initial momentum distribution (mini-jets) according to  Glück-Reya-Vogt parameterization for structure functions; K = 2  lower cut-off: p 0 = 1.4 GeV (reproduces dE T /dy)  particle production via standard nuclear geometry (Wood-Saxon density profile, Glauber-Model)  each parton is given a formation time  35 testparticles  simulate evolution of fireball up to ~5 fm/c  when energy density in a cell drops below  = 1 GeV  free streaming (in the respective cell)

Oliver Fochler Thermalization in Au+Au time evolution of p T spectra (central region, x T < 1.5 fm, |  | < 0.5)

Oliver Fochler Collective flow inelastic gluon interactions lead to sizeable v 2 the shear viscosity can be computed v 2 with fixded cs: cf. Molnar or AMPT

Oliver Fochler Energy loss in a static medium gluon jet in a static, thermal medium of gluons T = 400 MeV LPM cut-off increases due to boost

Oliver Fochler Au-Au – Nuclear modification factor central (b=0 fm) Au-Au collision at 200 AGeV  initial distribution: mini-jets STAR: PRL 91, (2003) PHENIX: arxiv: (2008)

Oliver Fochler Au-Au – Nuclear modification factor central (b=0 fm) Au-Au collision at 200 AGeV  initial distribution: mini-jets

Oliver Fochler Au-Au – Nuclear modification factor central (b=0 fm) Au-Au collision at 200 AGeV  initial distribution: mini-jets

Oliver Fochler Fixed binary cross sections? Only binary collisions with fixed cross section 10 mb clearly overestimate jet-quenching!

Oliver Fochler Are we there yet? Well, not quite. Some things to look at.. HP 2008, C. Vale

Oliver Fochler More things to look at..

Oliver Fochler And more.. In-Plane Out-of- Plane

Oliver Fochler And even more.. 3 < p t,trig < 4 GeV/c4 < p t,trig < 6 GeV/c

Oliver Fochler Summary and to-do list fully dynamic simulation of jet quenching in central Au+Au collision thermalization, collective flow etc. are investigated in the same framework quantitative description of v 2 and R AA within a common description not possible with binary collisions and fixed cross sections include (light) quarks implement fragmentation scheme crank up computational performance (parallel computing?, testparticle scheme) look at the observables from the previous slides..

Oliver Fochler Thank you!

Oliver Fochler Mean transverse momentum acquired mean transverse momentum squared per collision divided by mean free path T = 400 MeV

Oliver Fochler Energy loss in a static medium gluon jet in a static, thermal medium of gluons T = 400 MeV

Oliver Fochler Gluon-Quark-Ratio

Oliver Fochler Au-Au – Reconstruction partons with high-pt too rare  simulate large number of initial conditions  select events according to highest pt-(test)particle  simulate only selected events and weight results full: events; reconstruction: 40 events per pt-bin, ~1000 total