PPG067 Physics Statements

Michael P. McCumberand

Barbara JacakAugust + September, 2006

25 September 2006 Michael P. McCumber& Barbara Jacak 2

Figure 3

rms increases with npartkurtosis decreases rapidly from near- gaussian values

away side peak dispacement is consistent with 0 in dAu & peripheral AuAu.rapidly increases to about 1 rad.

25 September 2006 Michael P. McCumber& Barbara Jacak 3

Mechanisms for away-side modification

Mach Cone Cherenkov Gluon-Radiation Wake Waves Medium-induced gluon radiation

at large emission angles Damping of jet by strongly coupled

medium (via AdS/CFT)

25 September 2006 Michael P. McCumber& Barbara Jacak 4

Mach Cones – Renk & Rupperthep-ph/0605330

Mach cone survives expansion!

Longitudinal flow → better Δφ signal from a Mach Cone

Data → large fractional of energy deposited in collective, propagating mode

Away Near→

25 September 2006 Michael P. McCumber& Barbara Jacak 5

Mach Cones – Chaudhuri & Heinz

hydro simulations: assumelost energy instantaneously thermalized

No Mach cone produced

Large energy loss scenarios give “splash-back” signal

rejected by data

PRL97, 062301 (2006)

25 September 2006 Michael P. McCumber& Barbara Jacak 6

Mach Cones – Jorge & Edward

Modified away side peak shape is due to propagation of a sound wave

Speed of sound intermediate between QGP (cs= 0.33) and hadron gas (cs= 0.2)

First order phase transition causes existence of region with cs=0. This would give a reflected wave, and 2nd peak at =1.4 rad

NP A774, 577 (2006) & hep-ph/0511263

25 September 2006 Michael P. McCumber& Barbara Jacak 7

Mach Cones – Jorge & Edwardhep-ph/0511263

No clear (or even unclear) evidence for second peakin ppg032 result

25 September 2006 Michael P. McCumber& Barbara Jacak 8

Run 4 AuAu

not here either…

(maybe in0-5% bin?)

25 September 2006 Michael P. McCumber& Barbara Jacak 9

Cherenkov – Koch, Majumder, Wang

Cherenkov production has “a strong dependence on the gluon momentum” & will “disappear for high-energy gluons”

D values will “gradually” shrink as associated momentum is increased.

Not consistent with our data

PRL 96,172302 (2006)

Paul C’s AN

25 September 2006 Michael P. McCumber& Barbara Jacak 10

Wake Waves – Ruppert, MullerExcite either a density wave or a plasma collective mode (plasmon)

Sub-sonic partons drag along a screening cloud as a wake (the response of plasma to color charge)

Super-sonic partons create Mach cone signal

If plasma is strongly coupled, high pparton excites plasma oscillations analogous to Cherenkov radiation(but it looks like Mach cone…)

PL B618, 123 (2005)

25 September 2006 Michael P. McCumber& Barbara Jacak 11

Large angle gluon emission -- VitevPL B630, 178 (2005)

Predicted angles are typically smaller than observed.

pT dependence in central collisions (like the data)

Average scattering angle decreases with path length

This contrasts our centrality dependence!

25 September 2006 Michael P. McCumber& Barbara Jacak 12

large angle gluon emission #2 Polosa & Salgado hep-ph/0607295

Look at symmetric & asymmetric gluon splittings (asym ~ like Vitev)pT trigger ~ pT associated restrict signal to a small number of splittingsSmaller qhat & larger radiated – gluons more collinear. So effects should disappear at smaller pTassoc at 62 than 200 GeV. can we say anything about this?

Vitev does opacity expansion, they use BDMPS

25 September 2006 Michael P. McCumber& Barbara Jacak 13

AdS/CFTcorrespondence of gravity in 5D string theory & field theory similar (but not identical) to QCD → field properties in limit of super strong coupling.Friess, et al. (hep-th/0607022) stress tensor →wake of directional emission at p = several times the temperature

see alsoCasalderry &Teaney (nucl-th/0605199)

Liu, Rajagopal, Wiedemann (hep-ph/0607062) on qhat

25 September 2006 Michael P. McCumber& Barbara Jacak 14

Figure 3

universal curve withNpart!

data imply:away side jetsplitting is aproperty of themedium, ratherthan the specificcollision system

successful modelsinclude strong mediumresponse to jet