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STAR André Mischke for the STAR Collaboration ICPAQGP, Kolkata, India, February 8-12, 2005 Recent “high-p T ” measurements in STAR.

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Presentation on theme: "STAR André Mischke for the STAR Collaboration ICPAQGP, Kolkata, India, February 8-12, 2005 Recent “high-p T ” measurements in STAR."— Presentation transcript:

1 STAR André Mischke for the STAR Collaboration ICPAQGP, Kolkata, India, February 8-12, 2005 Recent “high-p T ” measurements in STAR

2 STAR Andre Mischke, Utrecht UniversityCINPP 20052 modified High incident energy opens up hard scattering regime where pQCD High incident energy opens up hard scattering regime where pQCD is applicable in theory is applicable in theory Hard scattered partons to probe the properties of the produced dense Hard scattered partons to probe the properties of the produced dense colored medium colored medium High-p T (> 2 GeV/c) particle production High-p T (> 2 GeV/c) particle production  p-p: - parton distribution function (PDF) - hard scattering cross section - hard scattering cross section - fragmentation function (FF) - fragmentation function (FF)  A-A: - modified PDF (e.g. shadowing) - Cronin effect - Cronin effect - hard scattering cross section - hard scattering cross section - partonic energy loss (gluon radiation) - partonic energy loss (gluon radiation) - FF softened - FF softened Measurable effects: medium-induced modification of jet FF Measurable effects: medium-induced modification of jet FF - suppression of high-p T hadron production - suppression of high-p T hadron production - jet broadening - jet broadening High-p T probes at RHIC q q q q hadronic partonic q ?

3 STAR Andre Mischke, Utrecht UniversityCINPP 20053 Central Trigger Barrel (CTB) ZDC Time Projection Chamber (TPC) Barrel EMCal (BEMC) Silicon Vertex Tracker (SVT) Forward-TPC Endcap EMCal (EEMC) Time-of-Flight (TOF) The STAR detector NIM 499, 624 (2003) Solenoidal Tracker at RHIC  0

4 STAR Andre Mischke, Utrecht UniversityCINPP 20054 STAR results so far v 2 {2-particle} v 2 {AuAu – pp} v 2 {4-particle} Au-Au collisions at  s=200 GeV: Au-Au collisions at  s=200 GeV: - strong high-p T particle suppression - disappearance of the away-side jet - large and saturated elliptic flow  Consistent with the picture of parton  Consistent with the picture of parton energy loss in the dense medium energy loss in the dense medium (jet-quenching) (jet-quenching) d-Au measurements d-Au measurements  Jet-quenching is an effect happens in  Jet-quenching is an effect happens in the final state of the collision the final state of the collision Andre Mischke, Utrecht UniversityCINPP 20054 STAR PRL 91, 172302 (2003) PRL 91, 072304 (2003) PRL 90, 082302 (2003) PRL 93, 252301 (2004)

5 STAR Andre Mischke, Utrecht UniversityCINPP 20055 0~2~6 p T (GeV/c) low-p T intermediate p T high-p T Outline soft particle soft particle production: production: bulk matter bulk matter nuclear effects nuclear effects probe-medium probe-medium interplay interplay “clean” jet fragmentation “clean” jet fragmentation regime (pQCD) regime (pQCD)Variables Incl. particle spectra (R CP ) Incl. particle spectra (R CP )  asymmetry in d-Au identified particle Two-particle azimuthal Two-particle azimuthal away-side hadrons correlation correlation identified particle triggered  near-side  Incident energy (62 GeV) Incident energy (62 GeV) charged hadron spectra

6 STAR Andre Mischke, Utrecht UniversityCINPP 20056 d-Au (p-p): pQCD works at high-p T at RHIC d-Au (p-p): pQCD works at high-p T at RHIC Study nuclear effects like Cronin and shadowing  baseline for Au-Au Study nuclear effects like Cronin and shadowing  baseline for Au-Au Significant  dependence at highest centrality bin Significant  dependence at highest centrality bin Yields are well described by AMPT and saturation model Yields are well described by AMPT and saturation model Pseudo-rapidity asymmetry and centrality dependence in d-Au Pt spectra Au d PRC 70, 064907 (2004) PRC 70, 064907 (2004) h±h±

7 STAR Andre Mischke, Utrecht UniversityCINPP 20057 Charged hadron yield asymmetry in d-Au Back(Au)-forward(d) asymmetry ratio for two  ranges Back(Au)-forward(d) asymmetry ratio for two  ranges Cronin effect more pronounced in Au-direction Cronin effect more pronounced in Au-direction In qualitatively agreement with predictions from In qualitatively agreement with predictions from saturation and coalescence saturation and coalescence Different trend for initial parton scattering model (Hijing) Different trend for initial parton scattering model (Hijing) PRC 70, 064907 (2004) PRC 70, 064907 (2004) pT pT pT pT -0.50.51 0 open symbols solid symbols off mid-rapidity at mid-rapidity

8 STAR Andre Mischke, Utrecht UniversityCINPP 20058 R CP for  and K 0 s in d-Au Yields enhanced for p T > 1 GeV/c Yields enhanced for p T > 1 GeV/c Not dominated by jet fragmentation (expectation: one curve Not dominated by jet fragmentation (expectation: one curve for all particles) for all particles) Different behavior for mesons and baryons Different behavior for mesons and baryons  Cronin effect depending on quark content; initial or final ?  Cronin effect depending on quark content; initial or final ? STAR preliminary

9 STAR Andre Mischke, Utrecht UniversityCINPP 20059 Flavor dependence of particle spectra in Au-Au Suppression at high-p T Suppression at high-p T More significant meson-baryon pattern in Au-Au More significant meson-baryon pattern in Au-Au Collective hadron production mechanism: quark Collective hadron production mechanism: quark recombination/coalescence recombination/coalescence R CP PRL 92, 052302 (2004) J.Phys. G30, S963 (2004) expectations from jet fragmentation

10 STAR Andre Mischke, Utrecht UniversityCINPP 200510 Correlate high-p T trigger particles with associated Correlate high-p T trigger particles with associated particles above a certain kinematical threshold particles above a certain kinematical threshold Define correlation function: probability to find Define correlation function: probability to find another particle in ( ,  ) another particle in ( ,  ) Advantage of the STAR detector: large acceptance Advantage of the STAR detector: large acceptance Corrections for flow (v2) and non-flow Corrections for flow (v2) and non-flow contributions contributions Correlation variables: - peak width (  ,  ) Correlation variables: - peak width (  ,  ) - N ch (asso.) - N ch (asso.) Method favored the selection of high-p T trigger Method favored the selection of high-p T trigger particle near the medium surface particle near the medium surface Jetlike correlations: study two-particle angular distribution Trigger: leading hadron pzpzpzpz  pppp pxpxpxpx  pypypypy Trigger: leading hadron

11 STAR Andre Mischke, Utrecht UniversityCINPP 200511 Parton energy loss depends Parton energy loss depends on the path length traversed on the path length traversed Consistent with jet-quenching Consistent with jet-quenching picture:  E   s ½qL 2 picture:  E   s ½qL 2 Crosscheck at higher p T Crosscheck at higher p T in-plane out-of-plane  PRL 93, 252301 (2004)  correlation distribution wrt. to the reaction plane in Au-Au 4 < p T (trig.) < 6 GeV/c 2 GeV/c< p T (asso.) < p T (trig.)

12 STAR Andre Mischke, Utrecht UniversityCINPP 200512 Identified particle  correlations:  and K 0 s in d-Au Integrated yields of correlation Integrated yields of correlation peaks peaks Comparable to PHENIX Comparable to PHENIX measurements measurements Associated charged hadron Associated charged hadron multiplicity similar for meson multiplicity similar for meson and baryon triggers and baryon triggers No significant flavor dependence No significant flavor dependence at intermediate p T at intermediate p T |η|<0.7 preliminary

13 STAR Andre Mischke, Utrecht UniversityCINPP 200513 Away-side associate charged hadrons: low-p T part Observation so far: back–to-back jets Observation so far: back–to-back jets disappear for p T (asso.) > 2 GeV/c disappear for p T (asso.) > 2 GeV/c For lower p T (asso.) threshold: For lower p T (asso.) threshold: - correlation widely dispersed - momentum balance shape - higher fragmentation multiplicity - p T distribution softened Indication for thermal equilibration Indication for thermal equilibration of the away-side fragmentation of the away-side fragmentation products with the bulk medium products with the bulk medium nucl-ex/0501016 STAR preliminary 4 < p T (trig.) < 6 GeV/c 0.15<p T (asso.)<4 GeV/c

14 STAR Andre Mischke, Utrecht UniversityCINPP 200514  near-side correlations In central Au-Au: In central Au-Au: - jet-like correlation (short range) sits on top of a wide, nearly flat sits on top of a wide, nearly flat correlation (long range) correlation (long range) - evidence for near-side jet broadening in  direction broadening in  direction     d+Au, 40-100% Au+Au, 0-5% STAR preliminary 3 < p T (trig.) < 6 GeV/c 2 < p T (asso.) < p T (trig.)

15 STAR Andre Mischke, Utrecht UniversityCINPP 200515  near-side correlations (cont’d) Significant broadening at low p T (trig.), Significant broadening at low p T (trig.), disappears with increasing p T (trig.) disappears with increasing p T (trig.) N ch (asso.) invariant with collision system N ch (asso.) invariant with collision system Interpretation: - Recombination effects ? Interpretation: - Recombination effects ? - Interplay of medium-induced - Interplay of medium-induced gluon radiation and collective gluon radiation and collective longitudinal flow ? longitudinal flow ? correlation width Armesto et al., PRL93, 242301 (2004) S.A. Voloshin, nucl-th/0312065 STAR preliminary correlated yield 3 < p T (trig.) < 4 GeV/c 2 < p T (asso.) < p T (trig.) |  | < 1.0

16 STAR Andre Mischke, Utrecht UniversityCINPP 200516 Inclusive charged hadron spectra in 62 GeV Au-Au High-p T absolute yield one order High-p T absolute yield one order of magnitude lower of magnitude lower Spectrum shapes similar to 200GeV Spectrum shapes similar to 200GeV R AA ~1 at SPS. What happens at R AA ~1 at SPS. What happens at intermediate energies ? intermediate energies ? More quark jets expected at More quark jets expected at 62 GeV  less suppression 62 GeV  less suppression Energy dependence of the Energy dependence of the suppression factor suppression factor

17 STAR Andre Mischke, Utrecht UniversityCINPP 200517 R CP in 62 GeV Au-Au Same p T threshold for both Same p T threshold for both energies energies Splitting at intermediate p T Splitting at intermediate p T (due to Cronin effect ?) (due to Cronin effect ?) High-p T suppression at 62 GeV High-p T suppression at 62 GeV similar to 200 GeV similar to 200 GeV High-p T part (>6 GeV) suggest High-p T part (>6 GeV) suggest that suppression is driven by that suppression is driven by nuclear geometry nuclear geometry R CP

18 STAR Andre Mischke, Utrecht UniversityCINPP 200518  correlations in 62 GeV Au-Au Near-side associated yields are reduced (factor of ~3) at 62 GeV Near-side associated yields are reduced (factor of ~3) at 62 GeV Similar suppression of the away-side correlation Similar suppression of the away-side correlation preliminary

19 STAR Andre Mischke, Utrecht UniversityCINPP 200519 Particle production ranges soft particle soft particle production: production: bulk matter bulk matter nuclear effects nuclear effects probe medium probe medium interplay interplay “clean” jet fragmentation “clean” jet fragmentation regime (pQCD) regime (pQCD)Variables Incl. particle spectra (R CP ) Incl. particle spectra (R CP )  asymmetry in d-Au identified particle Two-particle azimuthal Two-particle azimuthal away-side hadrons correlation correlation identified particle triggered  near-side  Incident energy (62 GeV) Incident energy (62 GeV) charged hadron spectra 0~2~6 p T (GeV/c) low-p T intermediate p T high-p T

20 STAR Andre Mischke, Utrecht UniversityCINPP 200520 Barrel-EMCal Barrel-EMCal - |  |  1 and full azimuthal coverage - E T spectra: PRC 70, 054907 (2004) Neutral pions in d-Au nucl-ex/0410032 see poster by R. Sahoo  0    =p T /2, p T and 2p T 0<  <1 First hadron measurement with First hadron measurement with BEMC BEMC - 10% normalization uncertainty - NLO pQCD calculations, W. Vogelsang - Reasonable agreement within errors errors - Lower the systematic errors, work in progress work in progress

21 STAR Andre Mischke, Utrecht UniversityCINPP 200521 Trigger on high-E T photons measured in the Barrel-EMCal Trigger on high-E T photons measured in the Barrel-EMCal E T (trig.) up to 11 GeV (Au-Au: up to 20 GeV/c) E T (trig.) up to 11 GeV (Au-Au: up to 20 GeV/c) Photon - charged hadron azimuthal correlation in 200 GeV d-Au preliminary see poster by S. Chattopadhyay

22 STAR Andre Mischke, Utrecht UniversityCINPP 200522 “The overall picture” d-Au provides essential information for deeper understanding d-Au provides essential information for deeper understanding of the underlying mechanisms in Au-Au of the underlying mechanisms in Au-Au Baryon-meson pattern present in d-Au and Au-Au (due to quark Baryon-meson pattern present in d-Au and Au-Au (due to quark coalescence ?) coalescence ?) Near-side correlations: Near-side correlations: -  : similar for p-p, d-Au and Au-Au -  : similar for p-p, d-Au and Au-Au -  : interplay between parton energy loss and collective flow -  : interplay between parton energy loss and collective flow Away-side correlation: Away-side correlation: - jets traverse through the produced dense medium - jets traverse through the produced dense medium - associate hadrons appear at low-p T - associate hadrons appear at low-p T - first indications of thermal equilibration with the bulk matter - first indications of thermal equilibration with the bulk matter High-p T hadron suppression similar in 62 and 200 GeV High-p T hadron suppression similar in 62 and 200 GeV  Suppression seems to be driven by nuclear geometry  Suppression seems to be driven by nuclear geometry

23 STAR Andre Mischke, Utrecht UniversityCINPP 200523 Future challenges STAR white paper, nucl-ex/0501009 Identified particle spectra at still higher p T to see where pQCD Identified particle spectra at still higher p T to see where pQCD becomes dominant becomes dominant  high statistic data set: run IV at 200 GeV, analysis underway  high statistic data set: run IV at 200 GeV, analysis underway d-Au analysis at higher p T for deeper understanding of the d-Au analysis at higher p T for deeper understanding of the underlying mechanisms (e.g. initial and final Cronin effect) underlying mechanisms (e.g. initial and final Cronin effect)  identified particle spectra, e.g. neutral pions  identified particle spectra, e.g. neutral pions Evolution of jet quenching effect Evolution of jet quenching effect  system size (geometric scaling uncertainties): Cu-Cu (run V,  system size (geometric scaling uncertainties): Cu-Cu (run V, data taking right now) vs. peripheral Au-Au data taking right now) vs. peripheral Au-Au  energy: range mapping between top SPS and 62 GeV  energy: range mapping between top SPS and 62 GeV More details on the modification of the FF are needed, e.g. More details on the modification of the FF are needed, e.g. quantification of partonic energy loss quantification of partonic energy loss  direct photon tag  direct photon tag  heavy quark tag (discrimination between quark and gluon jets)  heavy quark tag (discrimination between quark and gluon jets)

24 STAR Andre Mischke, Utrecht UniversityCINPP 200524 49 institutes from 13 countries, 522 participants The STAR Collaboration

25 STAR Andre Mischke, Utrecht UniversityCINPP 200525 Back-up slides

26 STAR Andre Mischke, Utrecht UniversityCINPP 200526 Neutral pion p T Neutral pion p T measurement up measurement up to 13-16 GeV/c to 13-16 GeV/c Agreement with Agreement with PHENIX measurement PHENIX measurement within 10% within 10% PHENIX data: PRL 91, 072303 (2003)  0 transverse mass spectrum

27 STAR Andre Mischke, Utrecht UniversityCINPP 200527 Nuclear modification factor R AA in 62 GeV Au-Au p-p reference data from ISR p-p reference data from ISR (25-30% uncertainties) (25-30% uncertainties) Same p T threshold for both Same p T threshold for both energies energies

28 STAR Andre Mischke, Utrecht UniversityCINPP 200528 Inclusive hadron spectra in Au-Au

29 STAR Andre Mischke, Utrecht UniversityCINPP 200529 Compiled references: π 0, h ± 62 GeV data: p-p reference

30 STAR Andre Mischke, Utrecht UniversityCINPP 200530 Azimuthal anisotropy at 62 GeV publication in preparation Similar p T dependence v 2 for 62 GeV to 200GeV solid colored symbols: 62 GeV open symbols: 200 GeV two- (squares) and four- particle (triangles) culumant method

31 STAR Andre Mischke, Utrecht UniversityCINPP 200531 Away syst. error Near 4 < p T (trig.) < 6 GeV/c 0.15 < p T (asso.) < 4 GeV/c

32 STAR Andre Mischke, Utrecht UniversityCINPP 200532 Identified strange particles in d-Au STAR preliminary Yields measured up to (m T -m 0 ) ~ 5 GeV/c vs. centrality

33 STAR Andre Mischke, Utrecht UniversityCINPP 200533 Systematic studies underway with , K 0 s as trig, assoc. particles p t (trig) K 0 s -h h-h STAR preliminary d+Au 200 GeV

34 STAR Andre Mischke, Utrecht UniversityCINPP 200534 1.5 < p T (trig) < 3 GeV 1.5 < p T (assoc) < 3 GeV (0-5)%(10-30)% (30-50)% (50-70)% p+p (5-10)% Au+Au 200 GeV STAR preliminary

35 STAR Andre Mischke, Utrecht UniversityICPAQGP 200535 ~ jet cone width ~ jet co-planarity Width of near- and away-side peak decreases slightly with E T (trig.) Width of near- and away-side peak decreases slightly with E T (trig.) stays constant;  saturates at high-E T stays constant;  saturates at high-E T Photon- and charged-charged azimuthal correlation in 200 GeV d-Au STAR preliminary

36 STAR Andre Mischke, Utrecht UniversityCINPP 200536 Azimuthal anisotropy in 200GeV Au-Au In central Au-Au collisions, azimuthal anisotropy at high-p T (>5 GeV/c) dominated by non-flow effects Multiplicity independent quantity PRL 93, 252301 (2004)

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