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Jason Glyndwr Ulery Purdue University For the STAR Collaboration

Full Reconstruction of h ± Correlated with High P T h ± and Identified Baryons and Mesons from STAR. Jason Glyndwr Ulery Purdue University For the STAR Collaboration. Outline: Motivation Charged-Charged Correlations Identified Trigger Correlations 3 Particle Correlations Summary.

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Jason Glyndwr Ulery Purdue University For the STAR Collaboration

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  1. Full Reconstruction of h±Correlated with High PT h±and Identified Baryons and Mesons from STAR Jason Glyndwr Ulery Purdue University For the STAR Collaboration Outline: Motivation Charged-Charged Correlations Identified Trigger Correlations 3 Particle Correlations Summary

  2. Motivation • Want to create and study QGP • State of deconfined, thermalized quarks and gluons predicted by QCD at high energy density. • Jet • Can be calculated in pQCD and thus are well calibrated in a vacuum. • Are expected to be modified by the medium and can therefore give information on the properties of the medium.

  3. Au+Au, pp and d+Au 4.0<PTTrig<6.0 GeV/c • d+Au and pp similar • Implies jet suppression not an initial nuclear effect. • Au+Au suppressed on away side for higher associated pT. • Au+Au enhanced for inclusive associated pT. 2.0<PTAssoc<PTTrig GeV/c 0.15<PTAssoc<4.0 GeV/c

  4. STAR Preliminary STAR Preliminary Mean PT • <pt>=pt-weighted correlation / number correlation. • <pT> is more robust. • Some of the systematic errors cancel. • Dip in middle of away side in central Au+Au. • Appears more thermalized with medium.

  5. Mean PT Centrality Dependence. • Mean pT decreases with centrality in the away side. • Lower in core in central Au+Au.

  6. |Eta|<1.0 |Eta|<0.35 Conical flow? STAR data: background subtracted trigger pT =2.5-4 GeV/c, associated pT =1.0-2.5 GeV/c PHENIX data: background subtracted trigger pT =2.5-4.0 GeV/c, associated pT =1.0-2.5 GeV/c |Eta|<0.35 0-5% 5-10% STAR Preliminary 20-40% 10-20% Δφ Δφ 40-60% 60-80%

  7. PHENIX, PRL 91, 172301 (2003) Baryon/Meson • Greatly enhanced baryon over meson ratio in central Au+Au relative to pp. • Ratio nicely described by coalescence/ recombination. • But simple coalescence  no angular correlations • Identified trigger particle jets can give insight into this puzzle. M. Lamont (STAR), QM2004

  8. Particle Identification in the TPC e π K P Log dE/dx • Particle identification from TPC dE/dx distribution after the relativistic rise. • Fit with Gaussians fixing kaon yield from measured π+/k0s. • Select high dE/dx particles as pions and low dE/dx particles as protons/anti-protons. • NSigmaπ = (dE/dx-predicted π dE/dx) /resolution Log pT STAR Preliminary NSigma π

  9. Identified Trigger in d+Au and Au+Au • 50% Proton • 50% Anti-Proton • 95% π+ • 95% π- • Charged • 50% Proton/Anti-Proton • 95% π 3<PTTrig<4 GeV/c 0.15<PTAssoc<3.0 GeV/c Δφ Δφ Δφ STAR Preliminary 2.0<PTAssoc<3.0 GeV/c Au+Au 0-5% Most Central d+Au MinBias Similar correlation functions for particle and anti-particle. Hint of larger away correlation for baryon than meson.

  10. Strange Triggers 3<pTTrigger<3.5 GeV/c 1<pTAssociated<2.0 GeV/c • Λ • Anti-Λ • KS0 • Similar correlations for Λ, anti-Λ and K0s triggers. • V2 and background not subtracted. STAR Preliminary

  11. Au+Au 3<pTTrigger<4 GeV/c Spectra and Near Side Yield Near Side 0-5% • 50% p/pbar • 95% π • Charged • Spectra shapes are similar for different trigger particle species. • Hint of split between baryons and mesons in the near side yield at high pT. 1/NTriggerdN/dpT STAR Preliminary Au+Au 0-5% 1.0<pTAssociated<2.0 pTAssociated Away Side 0-5% • 50%p/pbar • Λ • Λbar • 95% п • K0s Nch/NTrigger 1/NTriggerdN/dpT STAR Preliminary STAR Preliminary pTTrigger pTAssociated

  12. near near 3-4 GeV/c 1-2 GeV/c near assoc trigger Medium soft bkgd assoc Medium Medium away away mach cone away di-jets deflected jets Is there conical flow? Df2 3-particle correlation Df1 hard-soft-corr + soft-bkgd. Df2 flow modulated background: soft-soft-corr in underlying event. Df1

  13. Hard-Soft-Soft Correlation Analysis 3<PTTrigger<4 1<PTAssociated<2 Raw Signal • Trigger particle chosen. • Distributions of pairs of associated particles Δφ1= φ1 -φtrigger and Δφ2 =φ2 -φtrigger • Mixed events modified by flow and subtracted 1 +2*v21v2triggercos[2(φ1 -φtrigger)] +2*v22v2triggercos[2(φ2-φtrigger)] +2*v21v22cos[2(φ1-φ2)] • Cross terms (hard-soft and soft-soft in background) is subtracted. 1/NTrigger (dN/d(Δφ))2 Mixed Events With Flow Hard-Soft STAR Preliminary Soft-Soft Final Signal Δφ AuAu 0-10%

  14. pp and d+Au pp 2<PTTrigger<4 1<PTAssociated<2 1/NTrigger (dN/d(Δφ))2 STAR Preliminary Δφ d+Au 2<PTTrigger<4 1<PTAssociated<2 • Appears elongated along the diagonal axis in d+Au • Possibly kT broadening Δφ Δφ Δφ d+Au 3<pTTrigger<4 1<PTAssociated<2 away sS/2 = 0.89 ± 0.11 sD = 0.69 ± 0.05 near sD = 0.66 ± 0.07 STAR Preliminary Δφ Δφ

  15. pTtrig=3-4, pTassoc=1-2 GeV/c 2-particle corr, bg, v2 subtracted d+Au min-bias Df2 p Dφ2=φ2-φtrig 0 0 p Df1 Au+Au 10% Df2 Dφ2=φ2-φtrig p dN2/dΔφ1dΔφ2/Ntrig 0 0 p Df1 Dφ1=φ1-φtrig Conical Flow? 3-Particle Correlation Three regions on away side: center = (p, p) ±0.4 corner = (p+1,p+1) ±0.4 x2 cone = (p+1,p-1) ±0.4 x2 difference in Au+Au average signal per radian2: center – corner = 0.3 ± 0.3 (stat) ± 0.4 (syst) center – cone = 2.6 ± 0.3 (stat) ± 0.8 (syst) d+Au and Au+Au elongated along diagonal: kT effect, and deflected jets? Distinctive features of conical flow are not seen in present data with these pT windows.

  16. 3 Particle V2 3<PTTrigger<4 1<PTAssociated<2 0-10% 4 Particle Cumulant V2 • Previous plots used average of 4 particle cumulant and reaction plane v2. • Correlation is robust with v2. STAR Preliminary Reaction Plane V2 Δφ Δφ Δφ STAR Preliminary Δφ

  17. Summary • Two particle angular correlation systematics • Broader correlation, softer pT and partial thermalization • Dip at π in <pT> as a function of Δφ • Identified trigger particle correlations • Little difference between different trigger particle species found. • Three particle angular correlations • Appears elongated along diagonal in d+Au and Au+Au. • Appears inconsistent with conical flow.

  18. 62.4 GeV/c Au+Au 0.15<pTAssoc<4.0 • Similar to 200 GeV/c on away side. • Reduced on the near side due to trigger bias. 4.0<pTTrigger<6.0 STAR Preliminary 2.0<pTAssoc<4.0

  19. Cu+Cu • Au+Au 200 GeV/c • Cu+Cu 200 GeV/c 0.15<pTAssoc<4 • Constant background subtracted. • V2 has not been subtracted STAR Preliminary 4<pTTrigger<6 2<pTAssoc<4 STAR Preliminary Δφ

  20. 7 dE/dx (nσπ) STAR Preliminary • Ratio consistent along nσπ nσπ • Near • Away • Middle STAR Preliminary Triggered Events/Mixed Events nσπ

  21. Au+Au Working Plot

  22. d+Au Working Plot

  23. d+Au Numbers • Peak-Corner: 0.062±0.006±0.001 • Peak-Cone: 0.071±0.006±0.002

  24. STAR Preliminary  d+Au 100-40%    Au+Au 5-0% STAR Preliminary Near Side Δη - Δφ Correlations Au+Au seems to sit on a pedestal in Δη. 3<PTTrig<6 GeV/c 2<PTAssoc<PTTrig GeV/c

  25. STAR preliminary STAR Preliminary Near Side Gaussian Widths and Yield • Significant broadening for low pT triggers for near side Δη. • Same Gaussian Δη peak yield for all collision types. • Underlying reasons not fully understood.

  26. |h| < 1 |h| < 0.35 |h| < 1 |h| < 0.35 2.5 < pTtrig < 4.0 GeV/c 1.0 < pTassoc < 2.5 GeV/c |h|<0.35 vs |h|<1

  27. |h| < 0.35 33.75 < |f| < 123.75 |h| < 0.35 33.75 < |f| < 123.75 |h| < 0.35 |h| < 0.35 2.5 < pTtrig < 4.0 GeV/c 1.0 < pTassoc < 2.5 GeV/c with |f| acceptance cut

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