STAR Strangeness Summary 2003 STAR Strangeness Summary 2003

STAR Strangeness Summary 2003 STAR Strangeness Summary - 2003

130 Ge. V Data All strange particles seem to increase linearly with h. Helen and Rene No step. STAR functions, no. Summarybig surprises Strangeness 2003 2

Statistical models What about the resonances? !? As we know beautiful agreement between models and data Helen and Rene STAR Strangeness Summary- 2003 3

Centrality Systematics of Chemistry Appears to be saturation of strangeness Helen and Rene STAR Strangeness Summary- 2003 4

Thermal freeze-out at 130 Ge. V Assume r= s(r/R) Tfo - ( ), 1 and 2 contours • , ( ? ): Show different thermal freeze-out behaviour: , K, P, STAR Preliminary Helen and Rene • , K, P, : Common thermal freeze-out at T~100 Me. V and < >~0. 52 c Early freeze-out due to smaller cross-section ? Radial flow developing at early times? , K, P, STAR Strangeness Summary- 2003 5

<pt> vs Centrality , K, p - <pt> increase with centrality - Heavy mass increase faster All consistent with radial flow differently – Early freeze-out too? Helen and Rene seems to flow. STAR Strangeness Summary- 2003 6

STAR Strange Spectra @ 200 Ge. V STAR Preliminary K* K 0 s preliminary Preliminary STAR Prelimin ary K preliminary Helen and Rene STAR Strangeness Summary- 2003 7

B/B Ratios All data: • ratios from raw yields densities in all 3 collision data Helen and Rene Similar net baryon STAR Strangeness Summary- 2003 8

/ ratio – Flat in pt • STAR is azimuthally symmetric so we can extract the anti-baryon to baryon ratio without an efficiency or acceptance correction 0 -10% Central @200 Ge. V • ▪ + X- and X+ uncorrected Yields in Pt bins • On a 0. 7<pt<4. 0 Ge. V/c range, no observed dependence of the ratio with pt and centrality Helen and Rene 0 -10% Central @200 Ge. V 0. 83+/-0. 02(stat)+/-0. 07(syst) X+ / X- ratio for Central data in Pt bins STAR Strangeness Summary- 2003 9

Improvements with 200 Ge. V Data STAR Preliminary 18% extrapolation Better stats. and measurements + STAR Preliminary + K+ Much higher reach on pt STAR Preliminary Finer centrality binning Helen and Rene STAR Strangeness Summary- 2003 10

Invariant mass spectra 200 Ge. V 60 -80% Xi - Axi S/N=1. 8 S/N=2. 15 20 -40% Xi – Axi S/N=2. 6 S/N=2. 89 0. 7 < pt < 6. 0 | Rp | < 0. 75 Helen and Rene 40 -60% Xi – Axi S/N=1. 74 S/N=1. 92 10 -20% Xi – Axi S/N=1. 15 S/N=1. 2 0 -10% Xi – Axi S/N=1. 4 S/N=1. 55 Centrality 0 -5% 28113. 4 +/-282. 0 22877. 9 +/-246. 9 5 -10% 20541. 8 +/-213. 9 17255. 8 +/-189. 0 10 -20% 6491. 7 +/-131. 6 5217. 7 +/-116. 3 20 -40% 8395. 8 +/-120. 8 7001. 7 +/-108. 5 40 -60% 4121. 2 +/-93. 1 3523. 5 +/-84. 0 60 -80% 1192. 8+/49. 4 1051. 5+/44. 7 Reconstructed X- and X+ as functions of centrality range STAR Strangeness Summary- 2003 11

Mt corrected spectra for , , , and + Mt spectra for , , -, +, -+ + as a function of centrality, from the most central at the top to the most peripheral at the bottom. Scale factors have been applied for a best spectra visualisation. The black lines are boltzmann fits. • Boltzmann fit to , , -, +, and -+ +. Stat errors only • Feed-down correction applied for • For ~2% Helen and Rene STAR Strangeness Summary- 2003 12

Inverse slope and <pt> 200 Ge. V • Same <pt> for - and + • Constant with centrality • Slight decrease for most peripheral <Nch> Deviates from a transverse flow picture. Earlier freeze-out? Reflect of partonic flow ? Helen and Rene STAR Strangeness Summary- 2003 13

Thermal freeze-out conditions 200 Ge. V The mt spectra can also fit to a hydrodynamically function : Schnedermann, Sollfrank &Heinz Nucl-th/9307020 Expansion of particles from a thermal expanding source with a transverse flow velocity < t> at Tfo Different thermal behavior than , K and p Helen and Rene STAR Strangeness Summary- 2003 14

Summary vs Centrality Helen and Rene STAR Strangeness Summary- 2003 15

Ratio centrality dependence and dep. on |s| Ratios / and / in Au+Au collisions at 200 Ge. V as a function of centrality. For the most central data, a comparison is made to the same ratios at SPS (blue stars) and to thermal models. The horizontal bars give the bin space. -/ at RHIC – 200 Ge. V -/ at SPS W/ - at SPS -/ PBM - thermal model -/ at PBM - thermal model Helen and Rene - with centrality almost flat production increasing with centrality (agreement with fig. 4) / and / increase with centrality, suggesting an increase of gs from peripheral to central AA collisions. STAR N Strangeness Summary- 2003 ch 16

Ratio centrality dependence and dep. on |s| • : Nonlinear function of Nch, 2 degrees polynomial ? /Nch flat with centrality Strangeness enhancement and saturation from peripheral to central collisions. (similar when compared to SPS results) Helen and Rene The drop of d. Ndy/Nbin is smaller for than and pbar due to the enhancement effects. STAR Strangeness Summary- 2003 17

d. N/dy - Exponential fit 0 -5% 10 -20% 20 -40% 40 -60% 60 -80% d. N/dy 2. 64+/-0. 08 1. 56+/-0. 08 0. 81+/-0. 03 0. 26+/-0. 01 0. 059+/-0. 005 d. N/dy 2. 12+/-0. 07 1. 23+/-0. 06 0. 65+/-0. 02 0. 22+/-0. 01 0. 059+/-0. 006 Reminder : RHIC @130 Ge. V: most central (0 -10%) 2. 16+/-0. 09 Xi/evt SPS @17. 4 Ge. V WA 97 : 1. 5+/-0. 1 Xi/evt ; 0. 37+/-0. 06 Axi/evt Boltzmann fit 0 -5% 10 -20% 20 -40% 40 -60% 60 -80% d. N/dy 2. 52+/-0. 08 1. 48+/-0. 07 0. 78+/-0. 03 0. 25+/-0. 01 0. 057+/-0. 005 d. N/dy 2. 03+/-0. 06 1. 16+/-0. 06 0. 62+/-0. 02 0. 21+/-0. 01 0. 058+/-0. 05 Helen and Rene STAR Strangeness Summary- 2003 18

Corrected - and + yields / centrality At mid-rapidity… 2=3. 66 2=0. 83 <Nch> Linear fit Helen and Rene <Nch> 2 degrees polynom fit STAR Strangeness Summary- 2003 19

Resonances and Survival Probability K* • Decays in fireball mean daughter tracks K measured can rescatter destroying part of signal K* K lost K* K K Chemical freezeout time • Initial yield established at chemical freeze-out Kinetic freezeout • Rescattering also causes regeneration which partially compensates • Ratio to “stable” particle reveals information on behaviour and timescale K measuredbetween chemical and kinetic freeze-out Two effects compete – Dominance depends on decay products and lifetime Helen and Rene STAR Strangeness Summary- 2003 20

Resonance Ratios STAR Preliminary Au-Au and p-p √s=200 Ge. V -> (1. 3 fm/c) K* -> K ( 4 fm/c) (1520) ->p. K (13 fm/c) Ur. QMD: signal loss SPS Helen and Rene K*(892) (1520) (17 Ge. V) [1] 66% 50% RHIC (200 Ge. V) [2] 55% 30% STAR Strangeness Summary- 2003 21

<pt> and p-p collisions K 0 s STAR Preliminary p-p 200 Ge. V Power Law fits STAR Preliminary p+p @ s = 200 Ge. V Helen and Rene STAR Strangeness Summary- 2003 22

<pt> and p-p collisions K 0 s Helen and Rene Evidence for mini-jets? STAR Strangeness Summary- 2003 23

Strangeness Enhancement Helen and Rene STAR Strangeness Summary- 2003 24

Strangeness Suppression Same plot as previous slide just normalized to top Au-Au emphasizes more common wisdom that yields are suppressed in p-p not enhanced in Au-Au Helen and Rene STAR Strangeness Summary- 2003 25

Min-bias identified particle v 2 at 200 Ge. V • v 2 appears to saturate at ~0. 13 for KS and ~0. 20 for with the saturation setting in at different p. T. • Conversion of coordinate to momentum anisotropy: at or near the hydrodynamic limit (zero path length/totally opaque). Helen and Rene STAR Strangeness Summary- 2003 26

Identified particle v 2 at low p. T PHENIX: nucl-ex/0305013 STAR: nucl-ex/0306007 : STAR Preliminary • Hydro models assuming local thermal equilibrium describe the species dependence of v 2 well. • Increase of integrated v 2 with mass is suggestive of significant collective motion. Helen and Rene STAR Strangeness Summary- 2003 27

K 0 s Correlations X 10 K 0 s Enough K 0 s/event to perform HBT measurement C 2 ry a n i lim e r M (Ge. V/C 2) P Fit to a gaussian R A ST l = 0. 5 0. 1 Rinv = 5. 8 0. 7 Helen and Rene STAR Strangeness Summary- 2003 28

HBT vs mt Wiedemann and Heinz expect: to drop with 1/mat (a ~ 0. 5) due to collective flow. Rinv for K 0 s does not seem to obey same mt scaling Need more detailed studies before conclusive statement made Helen and Rene STAR Strangeness Summary- 2003 29

Observing Hadronization Timescale The Premise: STAR pairs Preliminaryare created • Charge/anti-charge in Au-Au space-time Kaonsclose 200 Ge. V • Early creation (hadron gas) • Longitudinal expansion and rescattering pulls pairs apart – Loose correlation in rapidity • Late creation (after deconfined phase? ) • Pairs only form at hadronization, late in collision • Less rescattering – Less loss of correlation in rapidity Balance function tries to measure this correlation Width of balance function then related to time between hadronization and freeze-out Helen and Rene STAR Strangeness Summary- 2003 30

Balance Function at 200 Ge. V STAR Preliminary Smooth transition from p-p to Au-Au K narrower than Narrower widths for more central data: Delayed hadronziation? Helen and Rene STAR Strangeness Summary- 2003 31

d-Au Results STAR nucl-ex/0309012 Rd. Au vs. p. T for p, K and p 1) Nuclear modification factor: particle type or mass (Rcp for Ks, , and ). Note: within p. T ~ (0. 7 -2 Ge. V/c), proton Rd. Au is larger than that of Kaon and Pion! 2)Suppression observed in Au+Au: how about in d+Au? 3) Transverse momentum production: <p. T> versus multiplicity Helen and Rene STAR Strangeness Summary- 2003 32

Ks and invariant mass in d. Au Ks + bar Minbias data. Without background subtraction. Blue arrows point to the real mass values. Helen and Rene STAR Strangeness Summary- 2003 33

Charged kaon ratio – 3 centralities. Examples shows that statistics in data sufficient for smooth spectra in all centrality bins… C. M. Helen and Rene STAR Strangeness Summary- 2003 34

Transverse mass spectra STAR Preliminary Ø|rapidity|<1. 0; Measured Pt range: 0. 4 Ge. V~6. 0 Ge. V Øpower law function fits well in d. Au collisions ØStatistical errors only. Error bars(10%) are smaller than the size of data points. Helen and Rene STAR Strangeness Summary- 2003 35

Rcp for Ks, and f in d. Au STAR Preliminary Helen and Rene ØStatistical error only; ØBoth reconstruction efficiency and vertex finding correction included; Ø Rcp is flat at 1. 4 when pt > 2 Ge. V/c; ØKs Rcp is flat at 1. 2 when pt > 2 Ge. V/c; Ø Rcp is closer to Ks than . STAR Strangeness Summary- 2003 36

K- corrected spectrum (minbias). Helen and Rene STAR Strangeness Summary- 2003 37

Comparison of all kaon spectra. 4 methods! K 0 s slightly low? Being checked with 2 nd analysis. Helen and Rene STAR Strangeness Summary- 2003 38

Central to minbias ratio. Small enhancement, related to Cronin effect. Consistent for two particle (different analyses). Will form Rd. Au once proper normalization finalized (also in p+p). Helen and Rene STAR Strangeness Summary- 2003 39

Corrected anti- p. T spectrum. Exponential fit Helen and Rene STAR Strangeness Summary- 2003 40

Summary of Low pt Observations – Particle production is large • Small change from 130 to 200 Ge. V – Vanishing anti-baryon/baryon ratio (0. 7 -0. 8) • close to net baryon-free but not quite, ~same for 130, 200 and pp – Particles ratios suggest chemical equilibrium • Tch 170 Me. V, mb<50 Me. V near lattice phase boundary – Resonances appear strongly affected by rescattering in medium • Need Rescattering and regeneration more Au-Au data to get compete clearer picture – System exhibits collective behavior (radial + elliptic flow) • strong internal pressure that builds up very early • Some particles appear to freeze-out at earlier times – The system appears to freezes-out very fast • Balance function results – Large system at freeze-out • K 0 s appear to break mt scaling Overall picture: system appears to be in equilibrium, but it explodes and. Rene hadronizes rapidly STAR Strangeness Summary- 2003 Helen and 42

Strange Particles at High pt preliminary Mass dependence of the transverse expansion, change in shape at higher pt. Helen and Rene STAR Strangeness Summary- 2003 43

“Soft” vs “Hard” Physics “Soft” Physics “Hard” Physics - Npart: Number of participants number of incoming nucleons (participants) in the overlap region Nbin: Number of binary collisions number of equivalent inelastic nucleon-nucleon collisions Nuclear Modification Factor: N-N cross section <Nbinary>/ inelp+p If no “effects”: R < 1 in regime of soft physics R = 1 at high-pt where hard scattering dominates Helen and Rene STAR Strangeness Summary- 2003 44

p-p Inclusives Measurement Real p-p measurement no longer have to use UA 1 results Helen and Rene STAR Strangeness Summary- 2003 45

Charged Hadrons @ 200 Ge. V (h++ h-)/2 Real RAA Measurement! Still clear evidence for high pt suppression in central collisions Suppression factor ~constant for 6<pt<12 Ge. V/c Helen and Rene Evidence of partonic. STAR energy loss in the medium? Strangeness Summary 2003 46

Identified Particle Measurements A significant difference is seen between the pt dependence of K 0 S and Λ RAA. preliminary For pt from 1. 8 -3. 2 Ge. V/c in central collisions Λ production approximately follows Nbin scaling. At higher pt however, a suppression with respect to Nbin scaling is seen for both – “standard” fragmentation? preliminary Baryon/Meson difference or merely mass? Helen and Rene STAR Strangeness Summary- 2003 47

Rcp for h-, K, , , W, and f follows K not . Baryon meson effect. Not mass Helen and Rene STAR Strangeness Summary- 2003 48

Minimum bias v 2 Au-Au 200 Ge. V At high pt Hydro-like behaviour stops Deviation occurs earlier For K 0 s than for preliminary Helen and Rene Again mass or baryon/meson dependence? STAR Strangeness Summary- 2003 49

V 2 at High Mtm (J. Jia) (Voloshin) • A particle dependence and saturation in all three centrality intervals. • Hard-sphere, infinite-opacity limit for surface emission can’t reach the measured v 2 requires a dynamic expansion of strongly interacting matter. Helen and Rene STAR Strangeness Summary- 2003 50

Helen and Rene In this scenario we can infer the value of the parton v 2 in the relevant 51 p. T region (~7%). STAR Strangeness Summary 2003 51

Scaling Works for p, K, , What about ? Helen and Rene STAR Strangeness Summary- 2003 52

Scaling Breakdown Lower limit: p. T/n<0. 6 Ge. V/c 2 Upper limit: undetermined* *RCP suggest a breakdown for p. T/n>1. 7 Ge. V/c 2 Helen and Rene STAR Strangeness Summary- 2003 53

Particle spectra: Baryon enhancement at intermediate p. T. • Two component shape evident in kaon and pion spectra. • The pion and kaon shape change occur at similarly small p. T (near 1. 5 Ge. V/c). • For proton and the spectra don’t exhibit such a twocomponent shape. Helen and Rene STAR Strangeness Summary- 2003 54

Two component spectra fits: Hydrodynamic inspired model and p. QCD power-law. The crossover from a soft to hard shape is species dependent: p. T, cross(kaon) ≈1. 5 Ge. V/c, Helen and Rene p. T, cross( ) ≈ 3– 5 Ge. V/c ? STAR Strangeness Summary- 2003 55

The p. T Scale of RAA and v 2 for KS and The saturation of v 2 and fall of RCP are correlated. In a scenario with partonic energy loss followed by unmodified fragmentation, a larger v 2 would be associated with a smaller RCP. At intermediate p. T: species dependence contradicts a simple partonic energy loss and unmodified fragmentation picture. Helen and Rene STAR Strangeness Summary- 2003 56

Topology Analysis Spectra: Ks 0 and • Centrality bins chosen w/r to RCP • Comparison meson/baryon yields ! Helen and Rene STAR Strangeness Summary- 2003 57

B/B ratios - motivation Helen and Rene STAR Strangeness Summary- 2003 58

Non Strange Mixed Ratio p/ Consistent with PHENIX data @ 200 Ge. V. Helen and Rene No turnover from hydro Good Job for Soft+Quench STAR Strangeness Summary- 2003 59

/K 0 s for different centralities • UA 1 data from p+p collisions at s= 630 Ge. V. • Very good agreement between UA 1 and peripheral Au+Au. • Large baryon enhancement, relative to mesons, in central Au+Au. Helen and Rene STAR Strangeness Summary- 2003 60

/K 0 s compared to models Gyulassy, Vitev Helen and Rene Recombination/Coales cence STAR Strangeness Summary- 2003 61

Summary of High pt Observations • Strong hadronic suppression Onset at different times for different species • Azimuthal anisotropy at high pt Plateau occurs at different times for different species • Suppression of back-to-back hadron pairs large parton energy loss and surface emission? Need d-Au disentangle initial state effects in jet production (shadowing, Cronin enhancement) resolution of jet quenching picture J/ and open charm: direct signature of deconfinement? Helen and Rene STAR Strangeness Summary- 2003 62