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STAR d+Au and final-state suppression in Au+Au1 Evidence from d+Au measurements for final-state suppression of high p T hadrons in Au+Au collisions at.

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Presentation on theme: "STAR d+Au and final-state suppression in Au+Au1 Evidence from d+Au measurements for final-state suppression of high p T hadrons in Au+Au collisions at."— Presentation transcript:

1 STAR d+Au and final-state suppression in Au+Au1 Evidence from d+Au measurements for final-state suppression of high p T hadrons in Au+Au collisions at RHIC The STAR Collaboration Peter Jacobs Lawrence Berkeley National Laboratory nucl-ex/0306024

2 STAR d+Au and final-state suppression in Au+Au2 E-M Calorimeter Time of Flight Projection Chamber The STAR detector

3 STAR d+Au and final-state suppression in Au+Au3 Partonic energy loss in dense matter Multiple soft interactions: Strong dependence of energy loss on gluon density  glue  measure   color charge density at early hot, dense phase Gluon bremsstrahlung Opacity expansion: Bjorken, Baier, Dokshitzer, Mueller, Pegne, Schiff, Gyulassy, Levai, Vitev, Zhakarov, Wang, Wang, Salgado, Wiedemann,…

4 STAR d+Au and final-state suppression in Au+Au4 Jets at RHIC p+p  jet+jet (STAR@RHIC) Au+Au  ??? (STAR@RHIC) nucleon parton jet Find this……….in this

5 STAR d+Au and final-state suppression in Au+Au5 Partonic energy loss via leading hadrons - Energy loss  softening of fragmentation  suppression of leading hadron yield Binary collision scalingp+p reference

6 STAR d+Au and final-state suppression in Au+Au6 Au+Au and p+p: inclusive charged hadrons PhysRevLett 89, 202301 nucl-ex/0305015 p+p reference spectrum measured at RHIC

7 STAR d+Au and final-state suppression in Au+Au7 Suppresion of inclusive hadron yield central Au+Au collisions: factor ~4-5 suppression p T >5 GeV/c: suppression ~ independent of p T nucl-ex/0305015 Au+Au relative to p+p Au+Au central/peripheral R AA R CP

8 STAR d+Au and final-state suppression in Au+Au8 Jets and two-particle azimuthal distributions p+p  dijet trigger: highest p T track, p T >4 GeV/c  distribution: 2 GeV/c<p T <p T trigger normalize to number of triggers trigger N.B. shifted horizontally by  /2 relative to previous STAR plots! Phys Rev Lett 90, 082302

9 STAR d+Au and final-state suppression in Au+Au9 Azimuthal distributions in Au+Au Au+Au peripheral Au+Au central Near-side: peripheral and central Au+Au similar to p+p Strong suppression of back-to-back correlations in central Au+Au pedestal and flow subtracted Phys Rev Lett 90, 082302 ?

10 STAR d+Au and final-state suppression in Au+Au10 Is suppression an initial or final state effect? Initial state?Final state? partonic energy loss in dense medium generated in collision strong modification of Au wavefunction (gluon saturation)

11 STAR d+Au and final-state suppression in Au+Au11 nucl-ex/0305015 R CP Inclusive suppression: theory vs. data pQCD-I: Wang, nucl-th/0305010 pQCD-II: Vitev and Gyulassy, PRL 89, 252301 Saturation: KLM, Phys Lett B561, 93 p T >5 GeV/c: well described by KLM saturation model (up to 60% central) and pQCD+jet quenching Final state Initial state

12 STAR d+Au and final-state suppression in Au+Au12 Is suppression an initial or final state effect? Initial state? gluon saturation Final state? partonic energy loss How to discriminate? Turn off final state  d+Au collisions

13 STAR d+Au and final-state suppression in Au+Au13 d+Au vs. p+p: Theoretical expectations If Au+Au suppression is initial state (KLM saturation: 0.75) 1.1-1.5 pTpT R AB 1 Inclusive spectra If Au+Au suppression is final state ~2-4 GeV/c All effects strongest in central d+Au collisions pQCD: no suppression, small broadening due to Cronin effect 0  /2   (radians) 0 High p T hadron pairs saturation models: suppression due to mono-jet contribution? suppression? broadening?

14 STAR d+Au and final-state suppression in Au+Au14 ZDC-d FTPC-Au Au d ZDC-Au d+Au event selection Centrality tags: 1. FTPC-Au: charged particle multiplicity in -3.8<  <-2.8 2. ZDC-d: neutron spectator from deuteron Minimum bias trigger: ZDC-Au (95  3% of  hadronic )

15 STAR d+Au and final-state suppression in Au+Au15 Centrality tags FTPC-Au cut selects more central collisions Modeling FTPC-Au multiplicity: convolute Au-participant (Glauber) with UA5 mult. distribution (pbar+p @ 200 GeV, 2.5<  <3.5) min. bias =  central 20% =12.9  1.0 ZDC-d neutron spectator tag: measured: 19  1% of  hadronic Glauber: 18  3% of  hadronic  peripheral events

16 STAR d+Au and final-state suppression in Au+Au16 Inclusive charged particle spectra

17 STAR d+Au and final-state suppression in Au+Au17 Inclusive yield relative to binary-scaled p+p Suppression of the inclusive yield in central Au+Au is a final-state effect d+Au : enhancement Au+Au: strong suppression p T =4 GeV/c: cent/minbias = 1.11  0.03  central collisions enhanced wrt minbias

18 STAR d+Au and final-state suppression in Au+Au18 Azimuthal distributions pedestal and flow subtracted Near-side: p+p, d+Au, Au+Au similar Back-to-back: Au+Au strongly suppressed relative to p+p and d+Au Suppression of the back-to-back correlation in central Au+Au is a final-state effect

19 STAR d+Au and final-state suppression in Au+Au19 The strong suppression of the inclusive yield and back-to-back correlations at high p T previously observed in central Au+Au collisions are due to final-state interactions with the dense medium generated in such collisions.

20 STAR d+Au and final-state suppression in Au+Au20 Have we found the Quark Gluon Plasma at RHIC? We now know that Au+Au collisions generate a medium that is dense (pQCD theory: many times cold nuclear matter density) is dissipative exhibits strong collective behavior Not yet, there is still work to do We have yet to show that: dissipation and collective behavior both occur at the partonic stage the system is deconfined and thermalized a transition occurs: can we turn the effects off ? We have developed the tools necessary to complete this program This represents significant progress in our understanding of strongly interacting matter

21 STAR d+Au and final-state suppression in Au+Au21 Russia: MEPHI - Moscow LPP/LHE JINR - Dubna IHEP - Protvino U.S. Laboratories: Argonne Berkeley Brookhaven U.S. Universities: UC Berkeley UC Davis UC Los Angeles Carnegie Mellon Creighton University Indiana University Kent State University Michigan State University City College of New York Ohio State University Penn. State University Purdue University Rice University Texas A&M UT Austin U. of Washington Wayne State University Yale University Brazil: Universidade de Sao Paulo China: IHEP – Beijing IMP - Lanzou IPP – Wuhan USTC SINR – Shanghai Tsinghua University Great Britain: University of Birmingham France: IReS Strasbourg SUBATECH - Nantes Germany: MPI – Munich University of Frankfurt India: IOP - Bhubaneswar VECC - Calcutta Panjab University University of Rajasthan Jammu University IIT - Bombay VECC – Kolcata Poland: Warsaw University of Tech. The STAR Collaboration

22 STAR d+Au and final-state suppression in Au+Au22 Extra slide

23 STAR d+Au and final-state suppression in Au+Au23 Two-particle azimuthal distributions near-side and back-to-back peaks seen in minbias and central d+Au p+p  d+Au minbias  d+Au central: growth of off-jet pedestal small, if any, growth of back-to-back width


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