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Strange Hadron Production at Low Transverse Momenta

This study explores the production of strange hadrons at low transverse momenta, focusing on the identification and measurement of unidentified and identified strange particles. The research includes an analysis of hits and tracks in the PHOBOS detector, identification of strange particles using different methods, and a comparison of invariant yields in Au+Au collisions at √sNN=200 GeV.

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Strange Hadron Production at Low Transverse Momenta

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  1. Strange Hadron Production at Low Transverse Momenta Gábor I. Veres Massachusetts Institute of Technology for the Collaboration Strangeness in Quark Matter 2003 March 12-17, 2003, Atlantic Beach

  2. Collaboration (Jan 2003) Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Abigail Bickley, Richard Bindel, Andrzej Budzanowski, Wit Busza (Spokesperson), Alan Carroll, Patrick Decowski, Edmundo Garcia, Nigel George, Kristjan Gulbrandsen, Stephen Gushue, Clive Halliwell, Joshua Hamblen, George Heintzelman, Conor Henderson, David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova,Erik Johnson,Jay Kane, Judith Katzy, Nazim Khan, Wojtek Kucewicz, Piotr Kulinich, Chia Ming Kuo,Jang Woo Lee, Willis Lin, Steven Manly, Don McLeod, Jerzy Michałowski, Alice Mignerey, Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Inkyu Park, Heinz Pernegger, Corey Reed, Louis Remsberg, Michael Reuter, Christof Roland, Gunther Roland, Leslie Rosenberg, Joe Sagerer, Pradeep Sarin, Pawel Sawicki, Wojtek Skulski, Stephen Steadman, Peter Steinberg, George Stephans, Marek Stodulski, Andrei Sukhanov, Jaw-Luen Tang, Ray Teng, Marguerite Belt Tonjes, Adam Trzupek, Carla Vale, Gábor Veres, Robin Verdier, Bernard Wadsworth, Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Alan Wuosmaa, Bolek Wysłouch ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORY INSTITUTE OF NUCLEAR PHYSICS, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGO UNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER Gábor I. Veres

  3. The PHOBOS Detector (2001) Spectrometer Vertex 1m Octagon Paddle Trigger Counter Ring Counters Cerenkov Counter 137000 Silicon Pad Channels ZDC ZDC DX magnet DX Magnet 12m Be Beampipe NIM vol. 499/2-3, 2003 Gábor I. Veres

  4. Hits and Tracks in PHOBOS Nearly 4pCoverage Spectrometer p PID K+ f + -5.4 -3 0 +3 +5.4 h Distribution of hits and energy deposition  dN/dh Gábor I. Veres

  5. near mid-rapidity (Strange) particle ID in Z dN/dpT ToF up to 5 GeV/c 0.03 0.2 1.0 pT, GeV/c Charge Mass+Charge PID Mass Mass +Charge Stopping in Si dE/dx in Si ToF+Si Si Gábor I. Veres

  6. Topics in this talk Unidentified particles but... Identified yields of strange particles PID (kaons): near future ratios of strange particles “strange” results up to 5 GeV/c 0.03 0.2 1.0 pT, GeV/c Charge Mass+Charge PID Mass Mass +Charge Stopping in Si dE/dx in Si ToF+Si Si Gábor I. Veres

  7. Hadrons in the low pT range pT = 30 – 200 MeV/c (depending on particle MASS) Low B field + mult. Scattering: charge sign cannot be measured Yields of (+ + ) , (K+ + K), (p + p) Probing long distances (truly non-perturbative QCD regime) Radial flow Gábor I. Veres

  8. F E D C B A X[cm] Beam pipe Z[cm] Finding very low pT particles Search for particles ranging out in the 5th spectrometer plane Mass measurements (‘energy-range’ method) 20 • Eloss=dE • Mp= <dE/dx>Eloss m • (1/2) ( m2) 10 0 • Cuts on dE/dxper plane • ”MASS HYPOTHESIS” 0 10 20 Z [cm] P Ek=21 MeV • Cuts on Eloss(Ek=kinetic energy) • ”MOMENTUM HYPOTHESIS” K Ek=19 MeV dE/dx  Ek= 8 MeV • Corrections acceptance efficiency background A B C D E Gábor I. Veres silicon plane

  9. Measuring particle mass Results Au+Au sNN=200 GeV 15% central Test of the method: Reconstruction of low momentum MC particles (p,p) (p,p) Eloss <dE/dx>[10-3GeV2/cm] Eloss <dE/dx>[10-3GeV2/cm] (K+,K–) (K+,K–) (+,) (+,) MC DATA Eloss [MeV] Eloss [MeV] Gábor I. Veres

  10. Invariant yields (Au+Au) Au+Au sNN=200 GeV 15% central -0.1< y <0.4 Analysis: • Particle momenta: from comparison to GEANT • Corrections: •  acceptance & efficiency •  background: 20-40% • Systematic errors: 20%() ~40%(K) ~50%(p) (++) (K++K–) 1/(2pT)d2N/dydpT (p+p) PHOBOS preliminary nucl-ex/0210037 pT [GeV/c] Gábor I. Veres

  11. sNN = 200 GeV: Comparison to models HIJING RQMD HYDRO+THERMAL W.Broniowski,W.Florkowski (PRL87,2001,272302;PRC65,2002,064905) (Au+Au yields)/<Npart/2> (++) (K++K–) (p+p) 10 10 10 PHOBOS preliminary PHOBOS preliminary 1 1 1 1/(2mT) d2N/dydmT /<Npart/2> 10-1 10-1 10-1 PHOBOS preliminary 10-2 10-1 1 10-2 10-1 1 10-2 10-1 1 mT – m0 PHENIX 130 GeV PRL88,2002,242301 (p+p) corrected for feed-down nucl-ex/0210037 • very low pT range • (p+p):models differ by a factor 2 to 6 Gábor I. Veres

  12. Medium pT range pT = 0.07 – 1.0 GeV/c (depending on particle MASS) Antiparticle/particle ratios as a function of Npart and pT Properties of the system at freeze-out Baryon transport Gábor I. Veres

  13. 70 cm 10 cm z -x y Antiparticle toparticle ratios PID acceptance of the spectrometer y pT (GeV/c) B=2T  0.35 – 1.3 0.10 – 0.6 0.25 – 0.8 0.10 – 0.5 0.20 – 0.7 0.15 – 0.9 K p,p Momentum resolution 1 – 2 % Reversible 2T magnetic field Two symmetric spectrometer arms • Independent measurements • Acceptance & efficiency • corrections cancel Gábor I. Veres

  14. Particle identification: dE/dx Energy loss measurements in Si sensors: 7% resolution p Positive charges Negative charges K+ p K— + — Gábor I. Veres

  15. Corrections to the measured ratios : +3.7% absorption +0.7% secondary negligible -1.2% feed-down K-/K+ -/+ p/p Result: ratios at sNN = 200 GeV Au+Au High precision measurements Au+Au sNN = 200 GeV,12% most central PRC 67, 021901R, 2003 <–>/<+> = 1.025 ± 0.006(stat.) ± 0.018(syst.) <K–>/<K+> = 0.95 ± 0.03(stat.) ± 0.03(syst.) <p>/<p> = 0.73 ± 0.02(stat.) ± 0.03(syst.) Gábor I. Veres

  16. p/p Energy dependence of particle ratios A+A central collisions PHOBOS 200 GeV PRC 67, 021901R, 2003 K–/K+ PHOBOS 130 GeV PRL 87,102301, 2001 • Rapidly decreasing net baryon density near midrapidity Gábor I. Veres

  17. Centrality and pT dependence Au+Au sNN = 200 GeV 10% most central  p/p K–/K+ /+  p/p K–/K+ /+ PHOBOS preliminary PHOBOS preliminary nucl-ex/0210037 • Ratios, within the errors, are independent of pT and Npart Gábor I. Veres

  18. High-pT spectra. Tracking 1) find straight tracks in the field-free region 2) curved tracks found in B field by clustering in (1/p, ) space 3) Pieces matched 4) Momentum fit using the full track, and detailed field map z By Beam 2 1 x 10 cm Gábor I. Veres

  19. High-pT spectra: acceptance Acceptance Momentum resolution Data Sample: Au+Au run 2001 (200 GeV)  7.8 M minimum bias Au+Au events  32 M reconstructed particles Gábor I. Veres

  20. PHOBOS-Spectra @ 200GeV Au+Au (GeV/c)-2 Spectra corrected for - Acceptance/efficiency - Ghost tracks - Momentum resolution - Variable bin width - Secondaries At 200 GeV, min. bias p+p reference data exists x 10-1 x 10-2 x 10-3 x 10-4 x 10-5 (h++h-)/2 0.2<yp<1.4 0.2<y<1.4 Submitted to Phys.Lett. Gábor I. Veres

  21. Centrality Npart 45-50% 65 ± 4 35-45% 93 ± 5 25-35% 138 ± 6 15-25% 200 ± 8 6-15% 276 ± 9 0-6% 344 ± 12 Scaled Au+Au Spectra / p+p-Fit Submitted to Phys.Lett. Centrality range - <b> from 10 to 3 fm - <> from 3 to 6 Gábor I. Veres

  22. UA1 200 GeV Centrality scaling in pT bins (Au+Au) Spectra normalized to a fit to the pT spectrum at Npart = 65 (most peripheral centrality bin) Low and high pT: scaling with Npart Submitted to Phys.Lett.

  23. sinel=42 mb (RHIC) sinel=33 mb (SPS) sinel=21 mb (AGS) Number of collisions at different Energies Au+Au Glauber Monte Carlo Gábor I. Veres

  24. Evolution with Centrality (Au+Au) • Gradual change of shape • peak develops at 1.5 GeV/c Submitted to Phys.Lett. Gábor I. Veres

  25. High pT range In Au+Au: only unidentified high pT spectra……….but: Upgrade of in 2002: • Move of Time of Flight walls 4-5 m from interaction point: • higher pT-reach and • New scintillator trigger detectors: • to enhance high-pT ToF track sample …the new setup works for the ongoing d+Au run! Gábor I. Veres

  26. The PHOBOS Detector (2002 fall) ToF moved far from IP Tunnell wall New trigger detectors Gábor I. Veres

  27. Trigger detectors (d+Au) Segmented scintillator detectors at 45 and 90 degrees from beamline Combined with the ToF walls: • selects events with particle hitting ToF wall • enhances high-pT (straight) tracks: “online” tracking • decision-making in 50 ns ToF accepted rejected Trigger Gábor I. Veres

  28. Minimum bias trigger (d+Au) All tracks TOF tracks ToF + Trigger tracks ToF+Trigger+high pT logic If we trigger on them… Illustration only pT (GeV/c) Gábor I. Veres

  29. High pT trigger for ToF (d+Au) TOF tracks All tracks ToF + Trigger tracks ToF+Trigger+high pT logic Illustration only pT (GeV/c) • x15 enhancement in high pT ToF statistics • with respect to min. bias trigger Gábor I. Veres

  30. PID at high pT (d+Au) • high statistics dataset being collected • unidentified hadron spectra in preparation • identified charged hadron spectra in preparation Gábor I. Veres

  31. Summary  Very low pT (30-200 MeV/c): charged kaon invariant yields (strong radial flow, unique measurement)  Intermediate pT (0.07-1 GeV/c): charged hadron ratios (small B, evolution with energy, pT and Npart independence)  High pT (0.2-5 GeV/c): charged hadron invariant yields (closely Npart scaling at high pT, smooth evolution with Npart)  Future: high pT identified charged hadrons (changed ToF setup, new start detectors, new trigger detectors) Gábor I. Veres

  32. Invariant yields (Au+Au) Analysis details: Au+Au sNN=200 GeV 15% central -0.1< y <0.4 • Particle momenta calibrated with reconstr. GEANT tracks • (pT resolution ~5%) • Data corrections: •  acceptance & efficiency • (embedding single tracks) •  background corrections: • feeddown, secondaries, • misID, ghosts; • (p+p) 41±8% • (K++K–) 16±11% • (++) 39±3% • based on DCA distributions & • rescaled HIJING • Current systematic errors 20%() ~40%(K) ~50%(p) (++) (K++K–) 1/(2pT)d2N/dydpT (p+p) PHOBOS preliminary pT [GeV/c] nucl-ex/0210037 Gábor I. Veres

  33. UA1 200 GeV Centrality scaling in pT bins (Au+Au) Relative Yield Npart Spectra normalized to FIT to yield at Npart = 65 Gábor I. Veres

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