1 / 34

HBT Study in PHOBOS

HBT Study in PHOBOS. Willis T. Lin Dept. of Physics National Central University Chung-Li, TAIWAN. The PHOBOS Group. Argonne National Laboratory, USA Brookhaven National Laboratory, USA Institute of Nuclear Physics, Krakow, Poland Massachusetts Institute of Technology, USA

yahto
Download Presentation

HBT Study in PHOBOS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. HBT Study in PHOBOS Willis T. Lin Dept. of Physics National Central University Chung-Li, TAIWAN

  2. The PHOBOS Group Argonne National Laboratory, USA Brookhaven National Laboratory, USA Institute of Nuclear Physics, Krakow, Poland Massachusetts Institute of Technology, USA National Central University, Taiwan University of Rochester, USA University of Illinois at Chicago, USA University of Maryland, USA

  3. PHOBOS PUBLICATION • • Physics Results • Charged particle multiplicity near mid-rapidity in central Au+Au collisions at 56 and 130 GeV Phys. Rev. Lett. 85, 3100 (2000) • Ratios of charged antiparticles-to-particles near mid-rapidity in Au+Au collisions at 130 GeV Phys. Rev. Lett. 87, 102301 (2001) • Charged-particle pseudorapidity density distributions from Au+Au collisions at 130 GeV Phys. Rev. Lett. 87, 102303 (2001) • Energy dependence of particle multiplicities near mid-rapidity in central Au+Au collisions Phys. Rev. Lett 88, 22302 (2002) • Centrality Dependence of Charged Particle Multiplicity at |η|<1 in Au+Au Collisions at 130 GeV Phys. Rev. C 65, 031901R (2002) • Centrality Dependence of Charged Particle Multiplicity at |η|<1 in Au+Au Collisions at 130 and 200 GeV Phys. Rev. C 65, 061901R (2002) • Pseudorapidity and centrality dependence of the collective flow of charged particles in Au+Au collisions at 130 GeV Submitted to Phys. Rev. Lett. (2002)  • Ratios of charged antiparticles to particles near mid-rapidity in Au+Au collisions at 200 GeVSubmitted to Phys. Rev. C (2002) • The significance of the fragmentation region in ultrarelativistic heavy ion collisions •   Submitted to Phys. Rev. Lett. (2002)  • • Technical • Silicon Pad Detectors for the PHOBOS Experiment at RHICNucl. Instr. Meth. A461, 143-149 (2001) • Array of Scintillator Counters for PHOBOS at RHICNucl. Instr. Meth. A474, 38-45 (2001)

  4. RHIC Highest energy density ever produced in laboratory Species : pp, AuAu 12 June: 1st Collisions @ sNN = 56 GeV 24 June: 1st Collisions @ sNN = 130 GeV 5 Sep : end of first Au-Au Physics run 13 Sep : 1st polarized protons in RHIC 2001 : Looking for 1st Collisions @ sNN = 200 GeV Relativistic Heavy Ion Collider

  5. RHIC • 3.83 km circumference • Two independent rings • Capable of colliding any nuclear species on any other species • Collision Energy :500 GeV for p-p200 GeV for Au-Au (per N-N collision) • Luminosity :Au-Au 2 x 1026 cm-2 s-1 • p-p : 2 x 1032 cm-2 s-1 (polarized) To understand fundamental features of the strong interaction :  How does nuclear matter “melt” ? Where does the proton get its spin ?

  6. PHOBOS Detector 96000 Silicon Pad channels Paddle Trigger Counter TOF Cerenkov Octagon+Vertex Ring Counters • 4p Multiplicity Array • - Octagon, Vertex & Ring Counters • Mid-rapidity Spectrometer • TOF wall for high-momentum PID • Triggering • Scintillator Paddles • Zero Degree Calorimeter Spectrometer

  7. Silicon Everywhere Octagon Detector Ring Vertex Detector Silicon Pad Sensors Spectrometer Arm

  8. no. of days Silicon Sensors Performance • S/N ratios better than 10:1 design specification • Larger pads & longer readouts  lower S/N ratio • Ave. noise in entire detector setup stable over time

  9. Positive Paddles Negative Paddles ZDC N ZDC P Au Au PN PP x Events z Dt (ns) Event Selection Paddle Counters Coincidence (38 ns) between paddle counters

  10. PHOBOS Works

  11. HBT Briefing – Two-Particle Correlation r1 x Source y r2 Probability amp. (plane wave) The probability to detect particles at r1 and r2

  12. More Briefing Correlation function C2(k1,k2) can be defined: What can be measured are 1. 2. is the Fourier transformation particle density of source. : the distribution fn. of chaotic source

  13. Pairs from same event HBT, TPA, Coulomb, FSI No Any Correlated Interactions Pairs from “mixed” event Extract HBT Correlation - Using Event Mixing Method Naively, assume density of the source is a Gaussian distribution

  14. Qside Y-Axis Qlong Qout q P 1 K P 2 X-Axis Beam Axis Z-Axis Conventional Q Variables in LCMS LCMS or Pratt coor.

  15. Relationship btw Rout and Rside Only if x-t correlations are small and we get

  16. HBT Physics Motivation Au Source Size QGP Phase Hadron Phase Mixed Phase Au By definition HBT sensitive to distribution at hadron’s last scattering point a signature of QGP signalA tool to understand the space-time evolution in heavy-ion collisionTheories predicted a large and long-livedsource if QGP is created STAR PHENIX

  17. Two Particle Acceptance @ High mt |Qlong| < 10 MeV , 0.8 <mt < 1 GeV 60 mr 20 mr PHOBOS TPA Cut ~ 25 mr

  18. Two Particle Acceptance for “ideal case” • TPAC is parameterized by (Δθ,ΔYA) YA = 0 YA = 1 YA = 2 YA = 3 SpecP Only

  19. Two Particle Acceptance for “ideal case” YA = 0 YA = 1 YA = 2 YA = 3 SpecN Only

  20. Used Two Particle Acceptance Official Cut If the pair’s relative quantities (YA,θ) are located in the shadowed area, it won’t be employed in our analysis.

  21. “E866” Approximate Coulomb Correction Full-Wave Coulomb Correction “Partial” Coulomb Correction Coulomb Correction Coulomb Correction Gamowλ = 1 Rinv = 5 fm λ = 1 Rinv = 10 fm Gamowλ = 1 Rinv = 5 fm λ = 0.5 Rinv = 5 fmλ = 0.1 Rinv = 5 fm Qinv (GeV/c) Qinv (GeV/c) Coulomb Correction We apply “partial” Coulomb correction officially Coulomb correction is only applied to mixed pairs

  22. .05 cm vz .025 cm .025 cm Event Mixing “Fixed classes “ : Chop up vertex space #Real / #Mixed pairs must be larger than 3 !For each qualified domain, # of mixed pairs chosen randomlyis exact three times of real pairs

  23. Introduce HBT into MC (Ⅰ) Ideal comes from PYTHIA j NEW i NEW i OLD j OLD We can calculate the corresponding momentum shift Final momentum of particle i

  24. Introduce HBT into MC (Ⅱ) MC Recon

  25. Introduce HBT into MC (Ⅲ)

  26. Rout Rside Rlong R2out-long - - 0.540.02 5.80.2 5.10.4 6.80.3 4.91.7 ++ 0.570.03 5.80.2 4.90.4 7.30.3 4.51.9 Systematic error on radii of 1 fm, on  of 0.06 PHOBOS HBT Results @ 200 GeV

  27. HBT Excitation Function -- data

  28. Summary of HBT from RHIC PRELIMINARY STAR error bars are not shown Rout / Rside KT (GeV/c)

  29. 3 Kt bins analysis (Rout) π-π- (Without error bar) PRELIMINARY

  30. 3 Kt bins analysis (Rside) π-π- (Without error bar) PRELIMINARY

  31. 3 Kt bins analysis (Rlong) π-π- (Without error bar) PRELIMINARY

  32. 3 Kt bins analysis (Rout/Rside) π-π- (Without error bar) PRELIMINARY

  33. Conclusion  HBT results are consistent between 130 and 200 GeV • RHIC Puzzle ! Most reasonable models still don’t agree well with RHIC HBT data • Don’t forget the x-t correlation term ! • It’s possible a super-cooling source !

  34. Predicted Rout/Rside Assume a first order phase transition from a thermalized QGP to a gas of hadrons S. Soff et al. nucl-th/0012085 v2 (2001)

More Related