An Update from STAR – Using Strangeness to Probe Collisions You are never too old to set another goal or to dream a new dream C.S.Lewis 1898-1963 Helen Caines Yale University March 2003 Outline Soft - Bulk of the production - v2 flow - Charged hadrons, L, K - Chemical freeze-out – Strangeness enhancement? - Rescattering – K*,L(1520) - Thermal Freeze-out – X,W,f different behaviour? - Radii – K0s HBT Hard – Early times - Quark vs Gluon production – p/p and L/L - High pt suppression – charged hadron vs K0s vs L p-p - <pt> - Mini jets? Outlook – Look out for at QM2004 - Comparison p-p data – Relative rates - d-Au – Cold vs hot nuclear matter - FTPC - L at high y Helen Caines SQM – March 2003 2 STAR Strange Spectra @ 200 GeV X STAR Preliminary K0s f STAR Prelimin STAR Preliminary ary K* preliminary L W STAR Prelimin ary Preliminary K preliminary Helen Caines SQM – March 2003 3 The STAR Detector (Year-by-Year) Magnet Coils TPC Endcap & MWPC Time Projection Chamber Silicon Vertex Tracker * FTPCs ZCal Endcap Calorimeter Barrel EM Calorimeter ZCal Vertex Position Detectors Central Trigger Barrel + TOF patch RICH Helen Caines * yr.1 SVT ladder Year 2000, year 2001, year-by-year until 2003, SQM – March 2003 4 installation in 2003 130 GeV Data STAR Preliminary W+W Helen Caines All strange particles seem to increase linearly with h– March 2003 No stepSQM functions, no big surprises 5 Improvements with 200 GeV Data STAR Preliminary 18% extrapolation Better stats. W and W measurements L+L X+X STAR Preliminary K+ Much higher reach in pt STAR Preliminary STAR Preliminary Finer centrality binning Helen Caines SQM – March 2003 6 B/B Ratios STAR p+p √s = 200 GeV Au+Au All data: • mid-rapidity • ratios from raw yields Talk: Anja Billmeier, STAR preliminary Helen Caines Fri Similar net baryon in all 3 collision data SQMdensities – March 2003 7 Statistical models As we know beautiful agreement between models and data Helen Caines SQM – March 2003 8 Centrality Systematics of Chemistry Appears to be a saturation of strangeness Helen Caines SQM – March 2003 9 Statistical models What about the resonances?!? As we know beautiful agreement between models and data Helen Caines SQM – March 2003 10 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 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 measured between chemical and kinetic freeze-out Two effects compete – Dominance depends on decay products and lifetime Need more than one resonance Helen Caines SQM – March 2003 11 Resonance Ratios STAR Preliminary Au-Au and p-p √s=200GeV L(1520) ->pK (13 fm/c) K* -> K ( 4 fm/c) r -> (1.3 fm/c) UrQMD: signal loss Talks: Patricia Fachini, Ludovic Gaudichet & Haibin Zhang, Sun. Helen Caines SPS SQM – March 2003 K*(892) L(1520) (17 GeV) [1] 66% 50% RHIC (200GeV) [2] 55% 30% 12 Hydro-dynamically motivated fit Shape of the mT spectrum depends on particle mass STAR Preliminary R dn m cosh r pT sinh r r dr mT K1 T I0 lead mT dmT 0 T T Multiple interactions 1/mT dN/dmT (a.u.) - solid : used in fit K- to thermalization p flow -> limiting behaviour ideal hydrodynamic where r tanh 1 r E.Schnedermann et al, PRC48 (1993) 2462 s R r =s (r/R)n Two Parameters: T and Helen Caines SQM – March 2003 L mT - m0 (GeV) 13 Thermal freeze-out at 130 GeV Assume r= s(r/R) Tfo - r(), 1 and 2 contours X •X, (W?): Show different thermal freeze-out behaviour: W ,K,P,L STAR Preliminary • , K, P, L: Common thermal freeze-out at T~100MeV and <>~0.52c Early freeze-out due to smaller cross-section ? Radial flow developing at early times? ,K,P,L Talk: Javier Castillo, Mon Helen Caines SQM – March 2003 14 <pt> vs Centrality , K, p - <pt> increase with centrality - Heavy mass increase faster All consistent with radial flow Talk: Jinguo Ma, Sun Helen Caines f seems to flowSQM differently – Early freeze-out too? – March 2003 15 Elliptic Flow and the Hydro limit coordinate space • Coordinate space configuration anisotropic (almond shape) however, initial momentum distribution isotropic (spherically symmetric) • Only interactions among constituents generate a pressure gradient, which transforms the initial coordinate space anisotropy into a momentum Zhang, space anisotropy (no analogy in Gyulassy, Ko, PL B455 (1999) 45 pp) y x Momentum space d 3N 1 d 2N E 3 1 + 2vn cos n r d p 2 pt dpt dy n1 py 1 v2 cos 2( r ) , tan ( ) px Helen Caines High v2 evidence of early thermalization SQM – March 2003 16 Strange particle v2 at low pt V2 Mass dependence well described by blastwave model modified to allow for an azimuthal modulation of the second harmonic to the transverse rapidity: r= r0 +racos(2f) and a variation in the azimuthal density: s2. Combined fit to K0s and L gives Tfo ~ 100 MeV r0 ~ 0.66 ra ~ 0.04 1 s2 ~ 0.04 Pt GeV/C In good agreement with mt spectra Also seen at 130 GeV 2002, Phys. Rev. Lett. (2002) 132301-1 Do X and W agree? STAR Preliminary Au-Au 200 GeV Helen Caines SQM – March 2003 17 K0sK0s Correlations X 10 K0s Enough K0s/event to perform HBT measurement C2 Fit to a gaussian M (GeV/C2) C ( P, q) 1 + exp( R q ) 2 2 = 0.5 0.1 Rinv = 5.8 0.7 Talk: Selemon Bekele, Thurs Helen Caines SQM – March 2003 18 HBT vs mt Wiedemann and Heinz expect: RHBT V 1/ 3 to drop with 1/mat (a ~ 0.5) due to collective flow. Rinv for K0s does not seem to obey same mt scaling Need more detailed studies before conclusive statement made Helen Caines SQM – March 2003 19 Observing Hadronization Timescale The Premise: STAR pairs Preliminaryare created • Charge/anti-charge in Au-Au space-time Kaonsclose 200 GeV • 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 Caines SQM – March 2003 20 Balance Function at 200 GeV STAR Preliminary Smooth transition from p-p to Au-Au K narrower than just mass effect?) Talk: Gary Westfall, Fri Narrower widths for more central data: Delayed hadronziation? Helen Caines SQM – March 2003 21 Summary of Low pt Observations – Particle production is large • Small change from 130 to 200 GeV – 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 • Tch170 MeV, mb<50 MeV near lattice phase boundary – Resonances appear strongly affected by rescattering in medium • Need Rescattering and regeneration competepicture more Au-Au data to get clearer – 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 hadronize late • Balance function results – Large system at freeze-out • K0s appear to break mt scaling Overall picture: system appears to be in equilibrium, but it explodes and hadronizes rapidly SQM – March 2003 Helen Caines 22 Strange Particles at High pt preliminary preliminary Change in shape at higher pt. Helen Caines SQM – March 2003 23 “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 2 AA d N / dpT d Modification RAA ( pT ) 2 NN T d / dpT d Factor: AA N-N cross section <Nbin>/inelp+p If no “effects”: R < 1 in regime of soft physics R = 1 at high-pt where hard scattering dominates Helen Caines SQM – March 2003 24 Identified Particle Measurements A significant difference is seen between the pt dependence of K0S and Λ RAA. preliminary For pt from 1.8-3.2 GeV/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 Caines SQM – March 2003 Talk: Hui Long, Thurs 25 Minimum bias v2 Au-Au 200 GeV At high pt Hydro-like behaviour stops Deviation occurs earlier For K0s than for L preliminary Talk: Paul Sorensen, Thurs preliminary Helen Caines Again mass or baryon/meson dependence? SQM – March 2003 26 Interplay of soft and hard processes GLV theory Hydrodynamics plus jet quenching describes general form of v2 pt dependence Moderate pt - pion dominated by quenched pQCD, - baryon production dominated by non pQCD effects (e.g.baryon junctions or hydro) expect qualitative different v2 behaviour for different particle species Does it explain RAA? Helen Caines SQM – March 2003 27 Recombination vs Fragmentation Lower pt -Recombination dominates High pt - Fragmentation dominates Bass et al., nucl-th/0301087 Intermediate pt - Two processes compete Also S. Voloshin QM2002 Recombination dominates out to higher pt for baryons (3 q) - hadron suppression due to parton energy loss dominates later RAA different for mesons and baryons, What about v2 ? Helen Caines SQM – March 2003 28 B/B ratio at High Pt L/L Both Ratios fall at High pt Talk: Ben Norman, Thurs Seeing difference in quark vs gluon production mechanisms? Helen Caines SQM – March 2003 29 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 (Not shown here) 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 Caines SQM – March 2003 30 <pt> and p-p collisions K0s L K0s STAR Preliminary p-p 200 GeV STAR Preliminary p-p 200 GeV X Power Law fits Talk: Richard Witt, Thurs STAR Preliminary p+p @s = 200 GeV Not flow in p-p so evidence for mini-jets? Helen Caines SQM – March 2003 31 News from the front - Latest d-Au update STAR running since January √s = 200 GeV K0s already > 40M events taken! L, L X Helen Caines Varying Number of events in each plot, NO PHYSICS!!!! But will be.. SQMthere – March 2003 32 High Rapidity Ls? Not only use the FTPC’s for multiplicity at high y Results from ~ 2 M dAu minbias events FTPC west only (d side) First hint of L signal in d-Au at forward rapidity Helen Caines SQM – March 2003 33 B(arrel)EMC • dAu run (January 2003) – 60 modules instrumented – (D, Df) ~ (1.0, 2p) – 2400 towers pp run 16/22 modules 13% full EMC RICH dAu run 60 modules 50% full EMC Physics with the BEMC • Et • 0 • High-pt trigger x100 enhancement at 5 GeV •Jet and Quarkonia Trigger Under commisioning 0 d-Au + Not working Helen Caines Poster – Manual Calderon Thorsten Kollegger + SQM – March 2003 34 The STAR Collaboration Brazil: more Universidade de Sao Paulo China: IHEP – Beijing IMP - Lanzou IPP – Wuhan USTC Javier SINR – Shanghai Tsinghua University Russia: than 450 collaborators, 46 institutions, 9 countries MEPHI - Moscow Many here today: Talks: LPP/LHE JINR - Dubna IHEP - Protvino Selemon Bekele – Kaon HBT U.S. Laboratories: Anja Billmeier – Strange particle ratios in p-p Argonne Berkeley Castillo – Multi-strange baryons and thermal freeze-out Brookhaven Patricia Fachini – r and f0 production Ludovic Gaudichet – L(1520) production U.S. Universities: Great Britain: Arkansas University University of BirminghamHui Long – Suppression of high pt strange hadrons UC Berkeley UC Davis Jinguo Ma – f production France: UC Los Angeles Ben Norman – Ratios as function pt and centrality IReS Strasbourg Carnegie Mellon 0 SUBATECH - Nantes University Paul Sorensen – K s and L Azimuthal Anisotropy Creighton University Gary Westfall – Balance functions Germany: Indiana University MPI – Munich Richard Witt – Strange particle spectra in p-p Kent State University University of Frankfurt Michigan State University Haibin Zhang – K* production City College of New York India: Posters: Ohio State University IOP - Bhubaneswar Penn. State University John Adams – L reconstruction VECC - Calcutta Purdue University Panjab University Manuel Calderon de la Barca Sanchez – J/ triggering Rice University University of Rajasthan Texas A&M Magali Estienne – X reconstruction Jammu University UT Austin IIT - Bombay Julien Faivre – Improving reconstruction with LDA methods? Washington University VECC – Kolcata Wayne State University Mark Heinz – K0s reconstruction Yale University Poland: Thorsten Kollegger – Heavy flavour reconstruction Warsaw University of Tech. SQM – March 2003 35 Helen Caines Sevil Salur – S* reconstruction