JetMedium Interactions from RHICSTAR to LHCALICE Fuqiang Wang

Jet-Medium Interactions from RHIC/STAR to LHC/ALICE Fuqiang Wang Purdue University What have been learnt at RHIC? What can be done at LHC?

Jet-like angular correlations have provided valuable information at RHIC. 4 < p. Ttrig < 6 Ge. V/c p. Tassoc > 2 Ge. V/c At high pt away-side is suppressed. 4 < p. Ttrig < 6 Ge. V/c 0. 15 < p. Tassoc < 4 Ge. V/c 8 < p. Ttrig < 15 Ge. V/c p. Tassoc > 2 Ge. V/c At low pt away-side is enhanced and broadened. At higher trigger pt away-side is reappearing. 2

Associated p. T spectra: experimental way to study thermalization processes. PRL 95, 152301 (2005). 4 < p. Ttrig < 6 Ge. V/c syst. error hard-soft parton interactions drive jet products and medium to equilibrate. 3

Full reconstruction of “jet” energy One may construct fragmentation functions for different centralities. pp 4

p. Ttrig=4 -6 Ge. V/c p. Tassoc=0. 15 -4 Ge. V/c Away side <p. T> (Ge. V/c) p. T-weighted correlation number correlation <pt> can be studied in greater detail. path-length effect? conical flow? deflected jets? 5

centrality dependence of <p. T> near Away side <p. T> (Ge. V/c) Leading hadrons <p T> fro ma away wa Medium y je ts ecay md <p. T> from mediu 6

baryon/meson anomaly Coalescence/recombination models are very attractive. But baryon and meson trigger correlations are not much different. 7

With the emerged away-side jet, we can do trior quad-hadron correlations! Away-side fragmentation patterns appear unchanged with centrality. Are they the fraction of partons that escaped without interactions? Reconstruct the away-side jets including low p. T. Dan Magestro 8

All these studies can be carried out at LHC/ALICE, and better. • ALICE best suited for “semi-hard” region: probably where most of the jet-quenching actions take place. • Large p. T coverage: full reconstruction of jets. Jetfragmentation studies. • background increase (x 2) from RHIC to LHC. But huge increase in highp. T statistics. • unique PID capabilities. • larger statistics: multidimensional studies. 9

And even better… with triggering! • g (PHOS/EMC) + jet (TPC) g (EMC) + p 0 (PHOS) g (PHOS) + jet (EMC) – both surface and volume emission. – full reconstruction of away-side jets. energy balance? medium-energy pick-up? – modified jet-fragmentation functions. • g (PHOS/EMC) + e± (TPC) g (PHOS) + e± (EMC) – heavy-flavor energy loss 10

Conical flow? trigger pt =2. 5 -4. 0 Ge. V/c, associated pt =1. 0 -2. 5 Ge. V/c Jason Ulery PHENIX: |h|<0. 35 STAR: |h|<0. 35 Mark Horner 0 -5% 5 -10% 10 -20% 20 -40% 40 -60% 60 -80% STAR Preliminary 11

Three-particle correlations? near Df 2 J B Medium away mach cone near Df 2 Df 1 T(J+B)1(J+B)2 = (TJ 1 J 2) + (TJ 1)B 2 + (TJ 2)B 1 + T(B 1 B 2) = B 1 B 2 = flow modulated background Medium away deflected jets + SS (soft-soft correlation in Background) Df 1 12

3 -particle correlation analysis 3 < p. Ttrig < 4 Ge. V/c, 1 < p. Tassoc < 2 Ge. V/c, Au+Au 0 -10% Raw signal: T(J+B)1(J+B)2 flow modulated background STAR Preliminary soft-soft correlation Hard-Soft-bkgd: (TJ 1)B 2 + (TJ 2)B 1 bkgd-bkgd: B 1 B 2 13

effect of v 2 on 3 -particle correlation 1/Ntrig d 2 N/d(Δφ1)d(Δφ2) 3 < p. Ttrig < 4 Ge. V/c, 1 < p. Tassoc < 2 Ge. V/c, Au+Au 0 -10% average of 4 particle cumulant v 2 and reaction plane v 2 STAR Preliminary 4 particle cumulant v 2 reaction plane v 2 correlation result is robust with v 2. 14

pp and d+Au results 1/Ntrig d 2 N/d(Δφ1)d(Δφ2) 2 < p. Ttrig < 4 Ge. V/c, 1 < p. Tassoc < 2 Ge. V/c ppΔφ STAR Preliminary d+Au 3 < p. Ttrig < 4 Ge. V/c, 1 < p. Tassoc < 2 Ge. V/c Δφ Appears elongated along the diagonal axis in d+Au, possibly due to k. T broadening away near s. S/2 = 0. 89 ± 0. 11 s. D = 0. 69 ± 0. 05 s. D = 0. 66 ± 0. 07 d+Au Δφ 15

conical flow? 3 -particle correlation p. Ttrig=3 -4, p. Tassoc=1 -2 Ge. V/c 2 -particle corr, bg, v 2 subtracted d+Au and Au+Au elongated along diagonal: d+Au min-bias Dφ2=φ2 -φtrig k. T effect, and deflected jets? Three regions on away side: center = (p, p) ± 0. 4 corner = (p+1, p+1) ± 0. 4 x 2 cone = (p+1, p-1) ± 0. 4 x 2 d. N 2/dΔφ1 dΔφ2/Ntrig Dφ2=φ2 -φtrig Au+Au 10% difference in Au+Au average signal per radian 2: center – corner = 0. 3 ± 0. 3 (stat) ± 0. 4 (syst) center – cone = 2. 6 ± 0. 3 (stat) ± 0. 8 (syst) Distinctive features of conical flow are not seen in present data with these p. T windows. Dφ1=φ1 -φtrig 16

Three-particle correlations can be done at LHC, also much better. may have to be limited at low-modest p. T (need 2 associated particles). 17