1. PPR PWG 6 Work Plan - Correlations Working document… C. Pruneau July 23, 2008

2. Introduction Physics of Interest –Impact of Jets on the Medium –Impact of the Medium on Jets (our focus) Some key questions –Parton interaction with medium Transport, energy loss, q-hat? “Flow Effects on Jets”, early transverse fields –Hadronization: A+A vs p+p Fragmentation function: one or multi-particle Jet heating (away-side) Jet flavor composition (away-side)

3. Measurements (Jet-Jet Correlations) Change of Di-jet Cross Section –A.k.a number of associate jets/per trigger jet Change of Di-jet Invariant mass spectrum Energy (pt) Loss: p t1 vs p t2, p t1 -p t2 Acoplanarity , p t,out Away-side jet modification –Fragmentation function –Jet Transverse Momentum –Particle composition (ratio). A+A vs p+p

4. Di-jet Acoplanarity Measurements:  distribution k Tx, k Ty distribution Above with selection of |pt1-pt2| From Isabel Dominguez

5. Not yet the right model ! Cuts to be tuned ! From Isabel Dominguez

7. To be tested with improved model using final state k T ! From Isabel Dominguez

8. Di-jets Di-jet angle √s=5.5 TeV √s=200 GeV Reconstructing dijets is ‘easy’! Use background level to monitor/subtract combinatorics in A+A Widening of  at LHC energies: increase of initial state radiation, 3-jet events Background effects in A+A ? Marco

9. Di-jets (p t1 vs p t2 ) √s=5.5 TeV√s=200 GeV Marco Di-jets balance in energy  Handle on initial parton energy Correlation widens at LHC: radiation + 3-jet events Difference between A+A and p+p? Background effects ? Jet Modification Sensitivity?

10. Di-jet energy balance  p T for balancing di-jets Irreducible effects: k T, mult-jet events:  ~ 5-10 GeV Still works for charged-only jets (deteriorates quickly beyond) Direct measure of energy loss fluctuations  (  E) in Heavy Ion Collisions Sensitivity  (  E) ~ few GeV, can we be more precise? To do: Assessment of Emcal resolution (common to pp & AA), bulk+flow background effects in A+A Background cancels in pt2-pt1 measurements. How bad are finite stat effects. Energy loss phenomenology (out-of cone radiation) √s = 5.5 TeV

11. Away-side Fragmentation Fct. Select “geometry”: Select high-pt jet (EMCal), Study away-side jet (TPC) –Measure Fragmentation P(z) –Measure –Requires EMCal trigger, Best Jet Energy (trigger) determination. –Simulation (To do): Precision of P(z), measurements relative to medium modification.

12. Summary Acoplanarity: k Tx, k Ty,Dj –Can be done –Multi-jet effects important –How large are medium effects? Pt vs Pt –Can be done –Background effects? Jet splitting? –How large are medium effects? Away Side Jet –Enrich sample of modified jet. Bias of reconstruction?