Strangeness and heavy flavor at RHIC Recent Results

Strangeness (and heavy flavor) at RHIC Recent Results from PHENIX Masashi Kaneta RIKEN-BNL Research Center for the PHENIX collaboration Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 1

Outlook of this talk • PHENIX experiment • Recent results from PHENIX – Event anisotropy • 62. 4 Ge. V Au+Au : , K , p, and p (comparing with 200 Ge. V) • 200 Ge. V Au+Au : Heavy flavor electron – Single particle spectra of • 200 Ge. V d+Au and 200 Ge. V Au+Au – Anti-Pentaquark search and capability of the other strangeness • 200 Ge. V p+p, d+Au, and Au+Au – Heavy Flavor Results from PHENIX • See talk of H. Pereira (Saclay) on Sep. 17 (Fri) • Future strangeness and heavy flavor measurement at PHENIX – Charged hadron identification at high p. T: Aerogel Cherenkov Counter – Upgrade around vertex : Silicon Vertex, Hadron Blind Detector, TPC Nosecone Calorimeter • Summary Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 2

Brazil China University of São Paulo, São Paulo Academia Sinica, Taipei, Taiwan China Institute of Atomic Energy, Beijing Peking University, Beijing France LPC, University de Clermont-Ferrand, Clermont-Ferrand Dapnia, CEA Saclay, Gif-sur-Yvette IPN-Orsay, Universite Paris Sud, CNRS-IN 2 P 3, Orsay LLR, Ecòle Polytechnique, CNRS-IN 2 P 3, Palaiseau SUBATECH, Ecòle des Mines at Nantes, Nantes Germany University of Münster, Münster Hungary Central Research Institute for Physics (KFKI), Budapest Debrecen University, Debrecen Eötvös Loránd University (ELTE), Budapest India Banaras Hindu University, Banaras Bhabha Atomic Research Centre, Bombay Israel Weizmann Institute, Rehovot Japan Center for Nuclear Study, University of Tokyo, Tokyo Hiroshima University, Higashi-Hiroshima KEK, Institute for High Energy Physics, Tsukuba Kyoto University, Kyoto Nagasaki Institute of Applied Science, Nagasaki RIKEN, Institute for Physical and Chemical Research, Wako RIKEN-BNL Research Center, Upton, NY Rikkyo University, Tokyo Institute of Technology, Tokyo University of Tsukuba, Tsukuba Waseda University, Tokyo S. Korea Cyclotron Application Laboratory, KAERI, Seoul Kangnung National University, Kangnung Korea University, Seoul Myong Ji University, Yongin City System Electronics Laboratory, Seoul Nat. University, Seoul Yonsei University, Seoul Russia Institute of High Energy Physics, Protovino Joint Institute for Nuclear Research, Dubna Kurchatov Institute, Moscow PNPI, St. Petersburg Nuclear Physics Institute, St. Petersburg State Technical University, St. Petersburg Sweden Lund University, Lund 12 Countries; 58 Institutions; 480 Participants* Masashi Kaneta, USA Abilene Christian University, Abilene, TX Brookhaven National Laboratory, Upton, NY University of California - Riverside, CA University of Colorado, Boulder, CO Columbia University, Nevis Laboratories, Irvington, NY Florida State University, Tallahassee, FL Florida Technical University, Melbourne, FL Georgia State University, Atlanta, GA University of Illinois Urbana Champaign, Urbana-Champaign, IL Iowa State University and Ames Laboratory, Ames, IA Los Alamos National Laboratory, Los Alamos, NM Lawrence Livermore National Laboratory, Livermore, Ca University of New Mexico, Albuquerque, NM New Mexico State University, Las Cruces, NM Dept. of Chemistry, Stony Brook Univ. , Stony Brook, NY Dept. Phys. and Astronomy, Stony Brook Univ. , Stony Brook, NY Oak Ridge National Laboratory, Oak Ridge, TN University of Tennessee, Knoxville, TN Vanderbilt University, Nashville, TN RIKEN-BNL Research Center, *as of January 2004 “Strangeness at RHIC : Recent Results from PHENIX” 3

PHENIX • Collision vertex and centrality – Beam-Beam Counters (BBC) – Zero Degree Calorimeters (ZDC) • Tracking of Charged particle – Drift Chambers (DC) – Pad Chambers (PC 1, PC 2, PC 3) • , K, p, d, . . . ID by Time-Of-Flight – Start timing from BBC – Stop timing from High resolution TOF detectors (TOF) TOF from Lead Scintillator EMCal (Pb. Sc) • Electron ID – Ring Image Cherenkov (RICH) detectors – EMCal (Pb. Sc, Pb. Gl) • Photon ( 0, h, . . . ) – EMCal (Pb. Sc, Pb. Gl) • Muon – Muon Tracker (Mu. Tr) Cathode-strip readout chamber – Muon Identifier (Mu. ID) Streamer (Iarocci) tube and steel Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 4

Publication about Strangeness and Heavy Flavor • Single Identified Hadron Spectra from s. NN = 130 Ge. V Au+Au Collisions – K. Adcox et al. , Phys. Rev. C 69, 024904 (2004) • Centrality dependence of , K , p and p production from s. NN =130 Ge. V Au+Au collisions at RHIC – K. Adcox et al. , Phys. Rev. Lett. 88, 242301 (2002) • Measurement of the L and L particles in Au+Au Collisions at s. NN =130 Ge. V – K. Adcox et al. , Phys. Rev. Lett. 89, 092302 (2002) • Identified Charged Particle Spectra and Yields in Au+Au Collisions at s. NN = 200 Ge. V – S. S. Adler et al. , Phys. Rev. C 69, 034909 (2004) • Elliptic Flow of Identified Hadrons in Au+Au Collisions at s. NN = 200 Ge. V – S. S. Adler et al, Phys. Rev. Lett. 91 182301 (2003) • Measurement of Single Electrons and Implications for Charm Production in Au+Au Collisions at s. NN =130 Ge. V – K. Adcox et al. , Phys. Rev. Lett. 88, 192303 (2002) • J/y production from proton-proton collisions at s = 200 Ge. V – S. S. Adler et al. , Phys. Rev. Lett. 92, 051802 (2004) • J/y Production in Au-Au Collisions at s. NN =200 Ge. V at the Relativistic Heavy Ion Collider – S. S. Adler et al. , Phys. Rev. C 69, 014901 (2004) Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 5

Bulk Properties at RHIC • What we learnt from RHIC? – Low p. T (<~2 Ge. V/c) phenomena • Thermalization – Elliptic Flow » Agreement with Hydrodynamical calculations – Chemical freeze-out » The model well describes the data and strangeness equilibration at RHIC – Radial Flow » Single spectra of , K, p are described by common temperature and flow velocity – Intermediate and high p. T (>~2 Ge. V/c) phenomena • Dense matter effect in Au+Au collisions – High p. T suppression in single particle spectra – Back-to-Back jet suppression • Different effect in Baryon/meson Topics related to this talk – Mass scaling? – Due to number of consistent quarks? – Any difference in flavor (between light quark (u, d) and s)? Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 6

Elliptic Flow Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 7

Elliptic Flow at 62. 4 Ge. V Au+Au s. NN = 200 Ge. V Au+Au centrality : 0 -92% v 2 s. NN = 62. 4 Ge. V Au+Au centrality : 0 -84% stat. error only sys. error <15% stat. error only sys. error <20% PHENIX preliminary Charged p, K, p : PRL 91, 182301 (2003) p 0 : work in progress p. T [Ge. V/c] • Identified particle v 2 from 62. 4 Ge. V Au+Au – Looks similar , K, p dependence with 200 Ge. V Au+Au – With more statistics, we will be able to do detail analyses • Centrality dependence • More particle species (How about L, , etc. ? ) Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 8

Elliptic flow : nquark Scaling • A scaling of number of constituent quark – Quark coalescence picture • 62. 4 Ge. V Au+Au – The scaling looks working like 200 Ge. V Au+Au – Seems to be slightly lower than 200 Ge. V in p. T/nquark<1 Ge. V/c v 2 /nquark 62. 4 Ge. V Au+Au: PHENIX preliminary 200 Ge. V Au+Au, charged p, K, p : from PRL p 0 : work in progress stat. error only sys. error <20% (62 Ge. V) 15% (200 Ge. V) p. T /nquark [Ge. V/c] Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 9

v 2 of Heavy Flavor Electrons Estimation of v 2 100% of “photonic electron” “r (p. T)” “ ” 0. 3 0. 25 Inclusive (statistical error only) 0. 2 e± v 2 systematic errors of estimation Heavy Flavor e± v 2 bin width V. Greco, C. M. Ko, R. Rapp nucl-th/0312100 ± flavor charm v 2 w/ e flow w/o charm flow 0. 15 Glossary Photonic electron : e± from • Dalitz decay of 0, h, w, • di-electron decays r, w, • photon conversions • kaon decays ( en) r : photonic electron / inclusive electron v 2 heavy-flavor-e = s. NN = 200 Ge. V Au+Au centrality : 0 -92% v 2 inclusive-e - r v 2 photo-electron 1–r 0. 1 0. 05 0 work in progres s -0. 05 -0. 1 0 1 2 3 40 1 Hor. bar : stat. err. Box : total sys. err. 2 3 4 p. T [Ge. V/c] • v 2 of Heavy flavor electron – Looks consistent with/without charm flow – We hope that run 4 data will give an answer Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 10

meson Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 11

measurement at PHENIX • Both K+K- and e+e- channel are available – K : mass square from Time-of-Flight from TOF detector and EMCal – e : RICH and EMCal K +K - Run 3 s. NN = 200 Ge. V d+Au Kaon ID : TOF of Pb. Sc EMCal e +e - work ess Counts / bin in pr ogr Invariant mass [Ge. V/c 2] Masashi Kaneta, in pr ogre ss S ~ 120 S/B = 1/4 Invariant mass [Ge. V/c 2] RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 12

Single Particle Spectra of 1 d 2 N [(Ge. V/c 2 ) -2 ] 2 p m. T dy s. NN = 200 Ge. V Au+Au PHENIX final data to be submitted to PRC 10 1 s. NN = 200 Ge. V d+Au, Min. Bias PHENIX preliminary 10 -1 10 -2 10 -3 e+ e K +K - 10 -3 10 -4 K+K- 10 -5 0 0. 5 1 1. 5 2 2. 5 3 m. T – mass [Ge. V/c 2] Masashi Kaneta, 10 -5 0 0. 5 1 1. 5 2 2. 5 3 m. T – mass [Ge. V/c 2] RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 13

Inverse Slope Parameter and Yield of • Extracting inverse slope parameter and yield – Using a fit function 1 d 2 N [(Ge. V/c 2 ) -2 ] 2 p m. T dy s. NN = 200 Ge. V Au+Au PHENIX final data to be submitted to PRC 10 yield 1 Inverse slope parameter s. NN = 200 Ge. V d+Au, Min. Bias PHENIX preliminary stat. err. only 10 -1 10 -2 10 -3 stat. err. only e+ e K+ K- 10 -3 10 -4 K+K- 10 -5 0 0. 5 1 1. 5 2 m. T – mass Masashi Kaneta, 2. 5 3 [Ge. V/c 2] 10 -5 0 0. 5 1 1. 5 2 2. 5 3 m. T – mass [Ge. V/c 2] RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 14

Inverse Slope Parameter and Yield of Inverse Slope Parameter [Me. V] 200 Ge. V d+Au (preliminary) 200 Ge. V Au+Au w/ centrality cut 200 Ge. V Au+Au Min. Bias • Yield of – Increasing with – Not simple linear of Hor. bar : stat. err. Box : total sys. err. • Inverse slope of – Flat as a function of 200 Ge. V d+Au (preliminary) (d. N/dy) / (2 ) Box : total sys. err. d. N/dy Hor. bar : stat. err. 200 Ge. V Au+Au w/ centrality cut 200 Ge. V Au+Au Min. Bias • Over d+Au and Au+Au • Within statistics + systematic error 0 Masashi Kaneta, 100 200 300 0 RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 100 200 300 15

Radial flow • Single particle spectra of , K , p, p – Well described by Blast wave mode (E. Schnedermann et al, PRC 48, 2462 (1993)) fit – Common thermal freeze-out temperature and flow velocity for , K , p, p – How about for phi meson? Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” Computed by Akio Kiyomichi (2003 DNP / 2004 JPS meeting) Fit range : m. T – mass < 1 Ge. V/c 2 16

Does has same Tfo and with , K, p ? • Simultaneous fit Fit range m. T -mass < 1 Ge. V/c 2 – The c 2 contour plot for each particle 200 Ge. V Au+Au, top 10% 200 Ge. V Au+Au, 10 -40% 200 Ge. V Au+Au, 40 -92% 3 s 2 s 1 s • Within 3 s , K , p, p – Overlap of with , K, p – Large area of c 2 contour for • Because of larger statistical error (i. e. smaller c 2) of than , K, p • Need more statistics to conclude Masashi Kaneta, , K , p, p, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 17

Does has same Tfo and with , K, p ? 200 Ge. V Au+Au p, K, p : PHENIX, PRC 69, 034909 (2004) f : PHENIX final (to be submitted to PRC) Fit range m. T -mass < 1 Ge. V/c 2 Masashi Kaneta, • Simultaneous fit by , K , p, p and f – Seems to be common Tfo and – But don’t hurry up to conclude – Again, need more statistics RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 18

Intermediate p. T phenomena • Energy loss effect in proton at intermediate p. T is different from pion s. NN = 200 Ge. V Au+Au Shown in PHENIX white paper • Rcp of is close to pion rather than proton Yield (40 – 92%) / Ncoll(40 – 92%) Yield (0 – 10%) / Ncoll(0 – 10%) (=Rcp) – Note : Those are expected to be merged at very high p. T – Address a scaling of number of constituent quarks – Statistical error is still large • Need more statistic p. T [Ge. V/c 2] Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 19

Exotic Particle Search in RHIC Energy at PHENIX Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 20

Anti-Pentaquark Search • Pentaquark state is still not established yet – Many positive results – Many negative results • How about at PHENIX? – So far, negative with current statistics – We report a summary of the search in s(NN) =200 Ge. V p+p, d+Au, Au+Au Summary table from hep-ex/0406077 • Motivation: Why anti-pentaquark? – If a particle exists, anti-particle does – Anti-Baryon to Baryon ratio is high (>~0. 7) at RHIC energy • Channel – K+ + n – PHENIX n measurement is unique at RHIC (so far) • • Masashi Kaneta, Large energy deposit in EMCal Not photon-like shower shape No charged track association on the candidate Momentum reconstruction from Time-Of-Flight RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 21

No p. T cut • Comparison of momentum from TOF and tracking – Resolution<4%, 10%, 15% in p. T<1. 0, 1. 5, 2. 0 Ge. V/c, respectively + 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 – Invariant mass peak of : R. R. 99. 85%, c -= 2. 396 cm +(1197. 4) n + + : B. R. 48. 31%, c += 4. 434 cm • Mass shift due to no TOF calibration for n in EMCal is <~5% • Quick check by Monte-Carlo shows agreement with data Masashi Kaneta, No p. T cut - – Momentum shift <~5% -(1189. 4) n + - n + + Same event high p. T photon trigger Mixed event Min. Bias trigger 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 Invariant mass [Ge. V/c 2] Marker : Data Dash line : MC RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” + p. T [Ge. V/c] mass from PDG – Applying the reconstruction method to anti-proton 200 Ge. V p+p n + - mass peak [Ge. V/c] • Anti-n momentum resolution checked Counts / bin Reliability of Anti-n Candidate 22

Counts / bin K + + n in p +p, d+Au, Au+Au – Minimum bias trigger – 35 M events – 5 Me. V/c 2 per bin work -i n pro gress • Run 2 s. NN = 200 Ge. V Au+Au – Minimum bias trigger • Run 3 s. NN = 200 Ge. V d+Au Counts / bin • Run 3 s = 200 Ge. V p+p – Minimum bias trigger – 91 M events – 5 Me. V/c 2 per bin work Same event in pro gress Same event Mixed event No significant signa l seen – 36 M events – 4 Me. V/c 2 per bin Same event Mixed event Counts / bin Top 30% central work in pr ogr Masashi Kaneta, 30 -50% ess work 50 -92% in pr ogr ess work in pr ogre ss RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 23

More Strangeness at PHENIX • From combinations of ±, K±, p, p, and n K 0 s p. T =1 -2 Ge. V/c L(1520) ? • Demonstration from r 0 Not enough statistics. . – Run 3 s. NN =200 Ge. V p+p – ~24 M events of Min Bias trigger Invariant mass [Ge. V/c 2] • Blue histograms – Pair from save event • Red histograms – Combinatorial back ground from event mixing from Min. Bias trigger – Normalization range » solid filled area + p. T =1 -2 Ge. V/c Invariant mass [Ge. V/c 2] Masashi Kaneta, p. T =1 -2 Ge. V/c L p. T =1 -2 Ge. V/c Invariant mass [Ge. V/c 2] - p. T =1 -2 Ge. V/c Invariant mass [Ge. V/c 2] p. T =1 -2 Ge. V/c K*0 p. T =1 -2 Ge. V/c Invariant mass [Ge. V/c 2] RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 24

Future Measurement of Strangeness and Heavy Flavor at PHENIX Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 25

Aerogel Cherenkov Counter • Modules for half sector are installed in 2003 – Left half modules are already installed in July 2004 • Enhancement of PID capability at PHENIX – Proton separation from /K up to p = 7 Ge. V/c PMT (3 inch) Reflector (Goretex) Integration Cube (Air) PMT (3 inch) 3 m） Aerogel (index~1. 011) x 2 （11 0 16 ts en 3 gm 200 se e f th m in Azimuthal angle lf o Ha m) z Masashi Kaneta, 0 c 2 x 2 a (be d c ire n tio ch tra arge ck d RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 26

PID Plot with Aerogel Cherenkov Counter • With(without) requiring Cherenkov light associated to the track – We can see pion enhancement (rejection) – It will be functional to study intermediate p. T range Aerogel Required (Np. e. >3 in each PMT) Aerogel Veto (Np. e. <1 in each PMT) Peak position Experimental resolution (2 -sigma) line Masashi Kaneta, (calibration is not perfect yet) Statistics used for this analysis is less than 4% of total data from run 4 RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 27

Upgrade Plan around Vertex • Silicon Vertex detector and TPC – Enhancement of momentum resolution – Measurement of in-flight-decay particle • Will reduce background at high p. T • Nosecone Calorimeter h = 0. 35 – Jet measurement in forward region h = 0. 70 • Hadron Blind Detector h = 0. 88 (not shown in the plot) – Surrounds TPC – Electron ID by Cherenkov radiation detected by a photocathode layer h = 1. 17 h = 2. 6 Provides tracking coverage over -2. 6 < h < 2. 6 Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 28

Summary Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 29

Summary • Elliptic flow of charged , K, p from 62. 4 Ge. V Au+Au – Similar , K, p dependence with 200 Ge. V Au+Au – Quark coalescence picture still works in p. T /nquark<1 Ge. V/c • Heavy flavor electron from 200 Ge. V Au+Au – Consistent with/without Charm flow • Cross section of meson – 200 Ge. V d+Au and Au+Au • Less dependence of inverse slope parameter (from m. T exponential fit) • d. N/dy increases with , but liner scaling – Study of blast wave model fit • There is overlap of (Tfo, ) of with , K, p – But large range of within-3 -sigma of – need more statistics for detail analysis – Rcp is close to pion’s • support quark number scaling not mass • Anti-Pentaquark search at PHENIX – No significant signal in 200 Ge. V p+p, d+Au, Au+Au • It might be due to S/N ratio is poor at PHENIX • Because of no significant peak of L(1520) – With mixing-event technique, we will have the other strangeness • New detectors – Aerogel Cherenkov counters are installed • PHENIX PID capability (proton separation from /K) will be increased up to p. T=7 Ge. V/c – Silicon VTX, HBD, TPC will come to help electron measurements Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 30

About Sound Between Sections You hear sound between sections. That is from “Noh” which is Japanese traditional lyrical drama. “Noh” is completed as current style about 800 years ago in Muromachi shogunate era. The voice is “Yohhhh. ” Following that, the sound of musical instrument “Pon” is hit of “Tsuzumi” which is Japanese hand drum. The voice and sound of Tsuzumi are used for adjustment of timing and atmosphere of a serif, and changing a scene. Therefore, I used it for changing section and subject. By the way, the opening music is not traditional. I borrowed it from a recent Japanese drama. Click them Masashi Kaneta, { Yoh Pon Masashi Kaneta Yohhh Po Po Pon RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 31

Backup Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 32

BBC Reaction Plane Resolution Correlation 200 Ge. V Au+Au Correlation 62. 4 Ge. V Au+Au BBC Charge sum Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 33

Inclusive electron / photonic electron 1/”r” Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 34

Heavy flavor electron v 2 inclusive electron photonic electron non-photonic (=heavy flavor) electron { Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 35

Anti-Neutron PID Energy 0. 5 Ge. V photon Energy deposit/tower [Ge. V] MC all charged tracks Data 1 channel 5. 5 cm - + K- K+ pbar p 0. 5 Ge. V anti-n MC Energy deposit of absorption charge EMC TOF Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 36

PID Capability with ACC Momentum [Ge. V/c] 0. 5 1 2 2. 5 3 3. 7 4 4. 2 5 5. 5 6 7 ~10 K p TOF Aerogel (+ TOF or RICH) RICH Aerogel : (n=1. 011. ) TOF : 100 ps time resolution RICH : CO 2, (n = 1. 00041) Run 4 Au+Au 200 Ge. V Masashi Kaneta, K RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 37

STAR PHENIX STAR 200 Ge. V Au+Au from preprint s. NN = 200 Ge. V Au+Au 2 p m. T dm T dy 1 d 2 N [(Ge. V/c 2 ) - 2 ] PHENIX final data to be submitted to PRC 10 1 10 -2 10 -3 10 -4 10 -5 K+K 0 0. 5 1 1. 5 2 2. 5 3 m. T – mass [Ge. V/c 2] Masashi Kaneta, RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 38

Box : total sys. err. 200 Ge. V Au+Au w/ centrality cut 200 Ge. V Au+Au Min. Bias Hor. bar : stat. err. Box : total sys. err. Masashi Kaneta, 200 Ge. V d+Au (preliminary) Hor. bar : stat. err. (d. N/dy) / (2 ) 200 Ge. V d+Au (preliminary) 200 Ge. V Au+Au w/ centrality cut 200 Ge. V Au+Au Min. Bias d. N/dy STAR 200 Ge. V Au+Au from preprint PHENIX Inverse Slope Parameter [Me. V] STAR 0 100 200 300 0 RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 100 200 300 39

STAR p. T<~1 Ge. V/c Masashi Kaneta, PHENIX RIKEN-BNL Research Center, “Strangeness at RHIC : Recent Results from PHENIX” 40