Near-side  correlations of high-p t hadrons from STAR Jörn Putschke for the STAR collaboration Lawrence Berkeley National Laboratory Weisshorn (4505m), Switzerland

Jörn Putschke, Quark Matter 2006, Shanghai2 “Ridge” observation Additional near-side long range corrl. in  (“ridge like” corrl.) observed. Dan Magestro, Hard Probes 2004, STAR, nucl-ex/ , Phys. Rev. C73 (2006) and P. Jacobs, nucl- ex/ Phys. Rev. C73 (2006) p t < 2 GeV d+Au, % Au+Au, 0-5% 3 < p T (trig) < 6 GeV 2 < p T (assoc) < p T (trig)

Jörn Putschke, Quark Matter 2006, Shanghai3 3<p t,trigger <4 GeV p t,assoc. >2 GeV Au+Au 0-10% STAR preliminary Outline 2-particle  correlations:  How to extract the “ridge” yield ? (additional near-side long range corrl. in  )  Quantify ridge properties in Au+Au (Cu+Cu) 200 GeV collisions  Summary & discussion

Jörn Putschke, Quark Matter 2006, Shanghai4 Scenarios i) Parton radiates energy before fragmenting and couples to the longitudinal flow — Gluon bremsstrahlung of hard-scattered parton — Parton shifted to lower p t — Radiated gluon contributes to broadening  near-side jet also looses energy (finite pathlength)! ii) Medium heating + Parton recombination (Chiu & Hwa Phys. Rev. C72:034903,2005) — Recombination of thermal partons only indirectly affected by hard scattering  not part of the jet iii) Radial flow + trigger bias (Voloshin nucl-th/ , S. A. Voloshin, Nucl. Phys. A749, 287 (2005)) Armesto et al, PRL 93 (2004), nucl-ex/

Jörn Putschke, Quark Matter 2006, Shanghai5 Components of  correlations Au+Au 20-30% a b cc b a)Near-side jet-like corrl. + ridge-like corrl. + v 2 modulated bkg. b)Ridge-like corrl. + v 2 modulated bkg. c)Away-side corrl. + v 2 modulated bkg. Strategy: Subtract  from  projection to isolate the ridge-like correlation Au+Au 0-10% STAR preliminary

Jörn Putschke, Quark Matter 2006, Shanghai6  (J+R) |  |<1.7 J = near-side jet-like corrl. R = “ridge”-like corrl. v 2 modulated bkg. subtracted  (J+R) |  |<1.7 flow (v 2 ) corrected Extracting near-side “jet-like” yields 1 Au+Au 20-30% 2 2  (J+R) -  (R) const bkg. subtracted  (J) |  |<0.7   (J) no bkg. subtraction const bkg. subtracted  (J) |  |<0.7

Jörn Putschke, Quark Matter 2006, Shanghai7 Extracting the ridge yield  Definition of “ridge yield”: i) ridge yield := Jet+Ridge(    Jet(  ) ii) relative ridge yield := ridge yield / Jet(  ) STAR preliminary Jet+Ridge (  ) Jet (  ) Jet  ) yield ,  ) N part 3 2 GeV     Jet yield independent of N part and consistent with d+Au reference measurements !

Jörn Putschke, Quark Matter 2006, Shanghai8 Ridge shape measurement in central Au+Au I STAR preliminary 3 2 GeV   STAR preliminary yield  ) yield  )  3 2 GeV STAR preliminary

Jörn Putschke, Quark Matter 2006, Shanghai9 Ridge shape measurement in central Au+Au II Ridge yield as function of  saturates at high   non-uniform ridge shape in  Au+Au 0-10% STAR preliminary p t,assoc. > 2 GeV ridge yield 

Jörn Putschke, Quark Matter 2006, Shanghai10 Ridge yield in Au+Au p t,assoc. > 2 GeV STAR preliminary Ridge yield persists to highest trigger p t  correlated to jet production

Jörn Putschke, Quark Matter 2006, Shanghai11 “Jet yield” vs. p t,assoc. in central Au+Au “Jet spectrum” much harder than inclusive h  and increasing with p t,trigger STAR preliminary Jet yield inclusive Jet yield (p t,assoc > p t,assoc,cut ) p t,assoc,cut

Jörn Putschke, Quark Matter 2006, Shanghai12 Ridge yield vs. p t,assoc. in central Au+Au STAR preliminary “Ridge spectrum” slightly harder than inclusive h  and ~ independent of p t,trigger inclusive Ridge yield (p t,assoc > p t,assoc,cut ) p t,assoc,cut

Jörn Putschke, Quark Matter 2006, Shanghai13 “Jet”/ridge yield vs. p t,assoc. in central Au+Au preliminary Au+Au 0-10% preliminary Ridge / Jet yield STAR preliminary Ridge Jet p t,assoc,cut Ridge/Jet yield (p t,assoc > p t,assoc,cut ) STAR preliminary “jet” slope ridge slope inclusive slope

Jörn Putschke, Quark Matter 2006, Shanghai14 “Jet”/Ridge energy STAR, Phys. Rev. Lett. 95 (2005) < p t,assoc < 4 GeV 4 < p t,trigger < 6 GeV 6 < p t,trigger < 10 GeV Applying this “2-component picture” to lower p t,assoc measurements (see M. Horner’s talk: z t,jet (Au+Au) ~ z t,jet (d+Au)  subtracting p+p jet energy from Au+Au)  upper estimate of the energy deposit in the ridge ~ few GeV Consistent with energy loss picture ? “Ridge energy” “Ridge energy” } }

Jörn Putschke, Quark Matter 2006, Shanghai15 Ridge yield in Au+Au and Cu+Cu Relative ridge yield comparable at same N part in Au+Au and Cu+Cu p t,assoc. > 2 GeV STAR preliminary relative ridge yield relative ridge yield := ridge yield / Jet(  ) Au+Au 200 GeV Cu+Cu 200 GeV 3<p t,trigger <4 GeV Au+Au 200 GeV (30-40 %) Cu+Cu 200 GeV (0-10 %)

Jörn Putschke, Quark Matter 2006, Shanghai16 Ridge characteristics STAR Au+Au 0-10%, RHIC, US (~0m) preliminary Weisshorn (4505m), Switzerland ridge persists up to highest trigger p t  correlated to jet production (~ independent on trigger p t ) ridge spectrum ~ “bulk-like” ridge energy roughly a few GeV ridge comparable in Au+Au and Cu+Cu at same N part non-uniformity of ridge shape in   observed; needs further investigation (only small effect expected)

Jörn Putschke, Quark Matter 2006, Shanghai17 Discussion p t,assoc. ridge/jet yield h +,- ridge jet increasing p t,trig ridge spectrum slightly harder (?) than inclusive h +,- (tens of MeV)  consistent with medium heating parton recombination (  T~15 MeV) ? agreement with radial flow + jet quenching ? ridge spectrum qualitatively in agreement with parton energy loss and coupling to longitudinal flow quantitative calculation for comparison needed

Jörn Putschke, Quark Matter 2006, Shanghai18 Outlook Study geometry effects in more detail:  Look at near-side modifications in Au+Au with respect to the reaction plane PID ridge yield study with  , protons and strange particles (see J. Bielcikova’s talk) Systematic studies of the ridge shape at higher trigger p t and  3-particle  near-side correlations   Part /  Col Au+Au 30-40%  Part /  Col Cu+Cu 0-10%  Part ~ energy density  Coll ~ parton origin x [fm] y [fm] STAR very preliminary !  12  13

Jörn Putschke, Quark Matter 2006, Shanghai19 Backup slides

Jörn Putschke, Quark Matter 2006, Shanghai20 Analysis methods cont. preliminary v 2 subtraction and systematic error estimation Au+Au: a)Used v 2 values = mean between v 2 RP and v 2 {4} measurements b)Systematic errors mainly due to uncertainties in v2; use v 2 RP and v 2 {4} as upper and lower limit v 2 subtraction and systematic error estimation Cu+Cu: a)Used v 2 values = v2{CuCu-pp} b)Systematic errors mainly due to uncertainties in v2; use v 2 RP and no flow as upper and lower limit QM05 1.Use event-mixing to account for pair acceptance & use eff. correction for ass. particles 2.Background: a)Subtract constant background for  (J) method b)Subtract v 2 modulated background for  (J+R) method 3.Assume Gaussian correlation shape: yield(  ) = gaus integral / bin counting  (  ) = gaus width

Jörn Putschke, Quark Matter 2006, Shanghai21 p t,assoc. > 2 GeV STAR preliminary Jet+Ridge yield (  ) Jet yield (  ) Jet and Jet+Ridge yields & widths Jet+Ridge yield increasing with centrality  Jet+Ridge shape asymmetric in  and  preliminary p t,assoc. > 2 GeV Jet+Ridge width (  ) central Correlate Jet (  (J)) and Jet+Ridge (  (J+R)) widths & yields via centrality Jet width (  ) STAR preliminary central periph. YieldWidth

Jörn Putschke, Quark Matter 2006, Shanghai22 Jet yields & widths:  vs.  Correlate Jet (  (J)) and Jet (  (J)) widths and yields via centrality p t,assoc. > 2 GeV  Jet yield ~ symmetric in  Jet shape ~ symmetric in  for p t,trig > 4 GeV (asymmetric in  for p t,trig < 4 GeV) STAR preliminary centralperiph. Jet yield (  ) Jet yield (  ) Jet width (  ) Jet width (  ) Yield Width

Jörn Putschke, Quark Matter 2006, Shanghai23 “Jet”/Ridge energy/multiplicity STAR, Phys. Rev. Lett. 95 (2005) “Ridge N ch ” “Ridge energy” “Ridge energy” 0.15 < p t,assoc < 4 GeV

Jörn Putschke, Quark Matter 2006, Shanghai24 Pion vs. Proton relative ridge yield STAR preliminary p t,assoc. > 2 GeV Au+Au 0-10% Proton content of ridge larger than of jet part (more from strange assoc. particles in J. Bielcikova’s talk) Assoc. Protons Assoc. Pions Assoc. h 