1 / 23

N.N. Ajitanand, J. Alexander, D. Best, P. Brady, T. Case, B. Caskey , D. Cebra,

The low-energy end of the HBT excitation function Mike Lisa, for Roy Lacey , for the E895 Collaboration. N.N. Ajitanand, J. Alexander, D. Best, P. Brady, T. Case, B. Caskey , D. Cebra,

medge-cruz
Télécharger la présentation

N.N. Ajitanand, J. Alexander, D. Best, P. Brady, T. Case, B. Caskey , D. Cebra,

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. The low-energy end of the HBT excitation functionMike Lisa, for Roy Lacey, for the E895 Collaboration N.N. Ajitanand, J. Alexander, D. Best, P. Brady, T. Case, B. Caskey, D. Cebra, J. Chance, P. Chung, B. Cole, K. Crowe, A. Das, J. Draper, S. Gushue, M. Gilkes, M. Heffner, H. Hiejima, A. Hirsch, E. Hjort, L. Huo, M. Justice, M. Kaplan, J. Klay, D. Keane, J. Kintner, D. Krofcheck, R. Lacey, J. Lauret, E. LeBras, M. Lisa, H. Liu, Y. Liu, B. McGrath, Z. Milosevich, D. Olson, S. Panitkin, C. Pinkenburg, N. Porile, G. Rai, H.-G. Ritter, J. Romero, R. Scharenberg, L. Schroeder, B. Srivastava, N. Stone, J. Symons, S. Wang, R. Wells, J. Whitfield, T. Wienold, R. Witt, L. Wood, X. Yang, Y. Zhang, W. Zhang Auckland - BNL - CMU - Columbia - UC Davis - Harbin - KSU - LBL - St. Mary’s College - OSU - Purdue - Stony Brook RHIC/INT Workshop on HBT - jan02

  2. Outline • Definition and importance of correlation function • Definitions of out, side, long… • Central collisions • s systematics • pT systematics (flow) • comparison to models (systematic discrepancy) • Centrality dependence (assuming standard cylindrical symmetry) • Non-central collisions • new information available • extraction of shapes at AGS • possibilities for RHIC • Summary RHIC/INT Workshop on HBT - jan02

  3. Measurement with the EOS TPC • Up to ~350 particles/event (60 p-) measured over large phase space • Good reaction plane resolution • p/p  3% (dominated by MCS) •  5% e- contamination in p- • ~105 events at 2, 4, 6, 8 AGeV RHIC/INT Workshop on HBT - jan02

  4. Bertsch-Pratt projections (11% sT ycm0.35 pT = 0.1-0.3 MeV/c) RHIC/INT Workshop on HBT - jan02

  5. Evolution of the BP and YKP fit parameters • Increased production of long-lived p--emitters  fall in l • Strong evolution of Rs (R) with beam energy • Hadronic model with or without meanfield underpredicts (apparent) geometric size at low beam energy E895 Collab, PRL 84 2798 (2000) RHIC/INT Workshop on HBT - jan02

  6. Evolution of systematics - data and model • Observed evolution of systematics not reproduced by model • Dynamics driving RS(mT) may not depend on collision energy within RQMD RHIC/INT Workshop on HBT - jan02

  7. Testing the model at the SPS • For p-... • Model underpredicts apparent size below 10 AGeV... • overpredicts size at 158 AGeV • Extrapolation to RHIC??? NA44RQMD Rout4.88  0.21 6.96  0.14 Rside4.45  0.32 6.23  0.20 Rlong6.03  0.35 7.94  0.21 I.G. Bearden et al (NA44) PRC58, 1656 (1998) D. Hardtke, Ph.D. thesis (1997) RHIC/INT Workshop on HBT - jan02

  8. Central collisions • even at low energies, unclear that HBT well understood/reproduced by models • systematic discrepancies • predicted size: too small  too large as s grows (RQMD) • predicted timescale: too large RHIC/INT Workshop on HBT - jan02

  9. Centrality Dependence of the Correlations(“standard” cylindrical assumption) •  suppressed for central collisions due to increased production of L, h... • Gentle fall of transverse radii as size of overlap region falls b=27 fm: ~ 35% reduction in RMS RHIC/INT Workshop on HBT - jan02

  10. ! etc. themselves functions of f Probing freeze-out space-time structure for b0 side y K • Source in b-fixed system: (x,y,z) • Space/time entangled in pair system (xO,xS,xL) out f x b U. Wiedemann, PRC 57, 266 (1998) MAL, U. Heinz, U. Wiedemann PLB 489, 287 (2000) RHIC/INT Workshop on HBT - jan02

  11. Simplifying assumption at AGS: minimal effects of flow at very low pT side y K out f x b etc are now constants (several terms vanish @ pT = y = 0) U. Wiedemann, PRC 57, 266 (1998) MAL, U. Heinz, U. Wiedemann PLB 489, 287 (2000) RHIC/INT Workshop on HBT - jan02

  12. y 2nd-harmonic oscillations from elliptical transverse shape x b 1st-harmonic oscillations: spatial tilt angle qS y x qs z (Beam) Coordinate space! First-order information in HBT(f) RHIC/INT Workshop on HBT - jan02

  13. f () Data: p- correlation functionsAu(4 AGeV)Au, b4-8 fm 2D projections 1D projections, f=45° C(q) out side long lines: projections of 3D Gaussian fit • 6 components to radius tensor: i, j = o,s,l E895, PLB 496 1 (2000) RHIC/INT Workshop on HBT - jan02

  14. f () Cross-term radii Rol, Ros, Rslquantify “tilts” in correlation functions fit results to correlation functions Lines: Simultaneous fit to HBT radii to extract underlying geometry RHIC/INT Workshop on HBT - jan02

  15. qS=47° qS=33° qS=37° y y z z z y x x ’ x x x ’ x ’ similar to naïve overlap: b~5 fm 3 fm Images of p--emitting sources (scaled ~ x1014) 2 AGeV 4 AGeV 6 AGeV Large, positive tilt angles RHIC/INT Workshop on HBT - jan02

  16. p+ 6 AGeV • RQMD transport model: • Antiflow reflects dense region z~0 • (dilute large-|z| show positive flow) z (fm) pion momentum anisotropies due to reflection from flowing baryons (pND pN) p tilt reflects x-space structure of proton flow x (fm) Bass et al [PLB 302 381 (93)]: RQMD Au(2GeV)Au Opposing average tilts in p, x and the physics of p flow • p “antiflow” (negative tilt in p-space) • x-space tilt in positive direction •  non-hydro nature of p flow B. Caskey RHIC/INT Workshop on HBT - jan02

  17. At RHIC: transverse shapes as calculted by hydrodynamics elliptic/radial flow cannot be ignored… … but it can be included/constrained via spectra, v2 measurements can distinguish between early and late freezeout  handle on evolution timescale in addition to freezeout timescale See talk of F. Retiere P. Kolb, J. Sollfrank, and U. Heinz RHIC/INT Workshop on HBT - jan02

  18. Summary • Early hints that things might go wrong at RHIC • evolution of geometry, increasing effects of flow poorly reproduced by models at lower s • azimuthally-sensitive p- HBT - the next frontier • almond-shaped source, (~ entrance-channel geometry) • large positive spatial tilt angles • non-hydro nature of p flow • coordinate-space structure of proton flow • insight necessary and available at RHIC • which timescales are too short? • is the nature of freezeout understood? • how can hydro reproduce all else except geometry? RHIC/INT Workshop on HBT - jan02

  19. THE END RHIC/INT Workshop on HBT - jan02

  20. Bertsch-Pratt projections - data and RQMD (11% sT ycm0.35 pT = 0.1-0.3 MeV/c) RHIC/INT Workshop on HBT - jan02

  21. HBT radii at 2 AGeV RHIC/INT Workshop on HBT - jan02

  22. Evolution of (apparent) Shape: Oblate to Prolate • Transition from oblate to prolate shape at AGS connects Bevalac observations to SPS • Transition in character of flow/expansion: transverse  longitudinal? RHIC/INT Workshop on HBT - jan02

  23. K HBT @ AGS mapped by E895 (QM99) PRL 84, 2798 (2000) NPA 661, 444c (1999) Rout Rside HBT: probing freeze-out space-time structure I - Cylindrical sources RHIC/INT Workshop on HBT - jan02

More Related