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Latest Results From PHOBOS

Latest Results From PHOBOS. David Hofman University of Illinois at Chicago. PHOBOS Collaboration. Burak Alver , Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts,

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Latest Results From PHOBOS

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  1. Latest Results From PHOBOS David Hofman University of Illinois at Chicago

  2. PHOBOS Collaboration Burak Alver, Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Richard Bindel, Wit Busza (Spokesperson), Vasundhara Chetluru, Edmundo García,Tomasz Gburek, Joshua Hamblen, Conor Henderson, David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova, Chia Ming Kuo, Wei Li, Willis Lin, Constantin Loizides, Steven Manly, Alice Mignerey, Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Corey Reed, Christof Roland, Gunther Roland,Joe Sagerer, Peter Steinberg, George Stephans, Andrei Sukhanov, Marguerite Belt Tonjes, Adam Trzupek,Sergei Vaurynovich, Robin Verdier, Gábor Veres,Peter Walters, Edward Wenger, Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Bolek Wysłouch ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORY INSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGO UNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER 9 ongoing Ph.D. theses

  3. PHOBOS Experiment PHOBOS

  4. Colliding Nuclei at RHIC

  5. Two “snapshots” of colliding nuclei at RHIC nuclei crossing times extremely fast RHIC: ~0.13 fm/c SPS: ~1.6 fm/c AGS: ~5.3 fm/c

  6. Well known: initial collision geometry matters b Elliptic Flow Visible in final measured particle azimuthal angular distributions Initial overlap eccentricity ReactionPlane y0 Impact Parameter

  7.  To first order: initial collision geometry drives magnitude of v2 (of course, the density also matters) Well known: initial collision geometry matters b e v2 Elliptic Flow Visible in final measured particle azimuthal angular distributions Initial overlap eccentricity ReactionPlane y0 Impact Parameter Initial Eccentricity Final Particle Distributions

  8. Is our first RHIC snapshot “in focus”? b Lets focus on:the spatial distribution of the interaction points of participating nucleons Au+Au

  9. Is our first RHIC snapshot “in focus”? b b Lets focus on:the spatial distribution of the interaction points of participating nucleons for the same b, these interaction points will vary from event-to-event Au+Au Au+Au

  10. Is our first RHIC snapshot “in focus”? b b Lets focus on:the spatial distribution of the interaction points of participating nucleons for the same b, these interaction points will vary from event-to-event Y0 Au+Au Au+Au Y0 and thus the relevant eccentricity for elliptic flow also varies event-by-event From PHOBOS @ Quark Matter 2005  explored much further since then

  11. Does using make a difference? <epart>“participant” nucleonsevent-by-event calculation <estd>“standard” calculation YES 200 GeV Increasingly important for smaller systems

  12. How robust is Glauber MC + calculation? sNN skin depth nuclearradius min N-N separation Studied variations in: 90% CL bands on calculation arXiv:nucl-ex/0610037 Submitted to PRL In collaboration with Ulrich Heinz More recent studies have included variations in individual nucleon density profiles and different Npart and Ncoll weighting. calculation from Glauber MC is robust

  13. How robust is Glauber MC + calculation? sNN skin depth nuclearradius min N-N separation Studied variations in: 90% CL bands on calculation arXiv:nucl-ex/0610037 Submitted to PRL In collaboration with Ulrich Heinz More recent studies have included variations in individual nucleon density profiles and different Npart and Ncoll weighting. Bhalerao, Ollitrault – PLB641 260, (2006) Ollitrault – private communications (2006) PHOBOS internal MC calculation from Glauber MC is robust

  14. Data: average v2 in Cu+Cu and Au+Au Cu+Cu arXiv:nucl-ex/0610037 submitted PRL Au+Au: PRC 72 051901(R)

  15. Average v2/ in Cu+Cu and Au+Au Standard Eccentricity 200 GeV Cu+Cu Au+Au arXiv:nucl-ex/0610037, submitted to PRL

  16. Average v2/ in Cu+Cu and Au+Au Participant Eccentricity Standard Eccentricity 200 GeV 200 GeV Cu+Cu Cu+Cu Au+Au Au+Au arXiv:nucl-ex/0610037, submitted to PRL arXiv:nucl-ex/0610037, submitted to PRL

  17. Average v2/ in Cu+Cu and Au+Au Participant Eccentricity Standard Eccentricity 200 GeV 200 GeV Cu+Cu Cu+Cu Au+Au Au+Au arXiv:nucl-ex/0610037, submitted to PRL arXiv:nucl-ex/0610037, submitted to PRL unifies average v2 in Cu+Cu and Au+Au Related work: Miller, Snellings, Zhu, Bleicher, Stöcker Voloshin, Poskanzer, PLB 474 27 (2000); Heiselberg, Levy, PRC 59 2716, (1999)

  18. Average v2/ in Cu+Cu and Au+Au Participant Eccentricity Standard Eccentricity 200 GeV 200 GeV Cu+Cu Cu+Cu Au+Au Au+Au arXiv:nucl-ex/0610037, submitted to PRL arXiv:nucl-ex/0610037, submitted to PRL unifies average v2 in Cu+Cu and Au+Au Related work: Miller, Snellings, Zhu, Bleicher, Stöcker Voloshin, Poskanzer, PLB 474 27 (2000); Heiselberg, Levy, PRC 59 2716, (1999)

  19. New Data: pT dependence of v2/ Au+Au and Cu+Cu at matched Npart unifies midrapidity v2(pT) in Cu+Cu and Au+Au

  20. scaling as a function of h Cu+Cu and Au+Au at matched Npart The collision geometry controls the dynamical evolution of heavy ion collisions. Talk by Rachid Nouicer

  21. scaling as a function of h Cu+Cu and Au+Au at matched Npart The collision geometry controls the dynamical evolution of heavy ion collisions. Talk by Rachid Nouicer Consequence: this implies that the initial event-by-eventparticipant collision geometry appears relevant.

  22. Fluctuations in participant eccentricity What magnitude of fluctuations are expected? Quantify with s(epart)/<epart> Expect large dynamical fluctuation in the participant eccentricity

  23. New Analysis: event-by-event v2 measurement 200 GeV Au+Au • Utilize Full Phase space coverage of PHOBOS (|h|<5.4, Df~2p). • Detailed modeling of detector response, statistical fluctuations and multiplicity dependence. • Method is described in arXiv:nucl-ex/0608025 • Measure v2 on an event-by-event basis. • Take e-by-e result and average to compare to our other results. <v2> measured event-by-event is in agreement with both hit and track based PHOBOS results.

  24. New Result: v2 and epart Fluctuations s(v2)/<v2> in 200 GeV Au+Au Collisions Response of the measurement for MC events with no dynamical fluctuations Reminder: this analysis corrects for detector and multiplicity effects as well as statistical fluctuations

  25. New Result: v2 and epart Fluctuations s(v2)/<v2> in 200 GeV Au+Au Collisions band: 90% CL PHOBOS v2result MC with nofluctuations Observe significant dynamical v2 fluctuations

  26. New Result: v2 and epart Fluctuations s(v2)/<v2> and s(epart)/<epart> in 200 GeV Au+Au Collisions band: 90% CL PHOBOS v2result PHOBOS epartprediction MC with nofluctuations Magnitude of v2 fluctuations is in agreement with epart fluctuations Poster by Burak Alver and talk by Constantin Loizides

  27. Expanding Differentially in Phase Space

  28. New Data: global charged particle emission Midrapidity charged particles Midrapidity charged particle spectra Phys.Rev. C74 (2006) 021901 Phys.Rev.Lett. 94 (2005) 082304 Nucl.Phys. A774 (2006) 113-128 Extended longitudinal scaling Highlights from QM05 Energy/Centrality factorization and “scaling laws” in global charged particle production

  29. New Analysis: two particle correlations PHOBOS Preliminary PHOBOS Preliminary p+p @ 200 GeV Cu+Cu @ 200 GeV 0-10% central h± h± 6 6 -6 -6

  30. New Analysis: two particle correlations PHOBOS Preliminary PHOBOS Preliminary p+p @ 200 GeV Cu+Cu @ 200 GeV 0-10% central h± h± 6 6 -6 -6

  31. New Analysis: two particle correlations PHOBOS Preliminary PHOBOS Preliminary p+p @ 200 GeV Cu+Cu @ 200 GeV 0-10% central h± h± 6 6 -6 -6 Study the short-range rapidity correlations

  32. New Result: effective cluster size Keff = effective cluster size p+p scale error 2 On average, particles tend to be produced in clusters with a size of 2-3. Interesting centrality dependence – can compare to other systems Talk by Wei Li

  33. New Data: antiparticle/particle ratios 200, 62.4 GeV Cu+Cu 200 GeV Cu+Cu and Au+Au Detailed measurement of antiparticle/particle ratios as function of centrality

  34. New Publication: identified particle spectra 62.4 GeV Au+Au blast-wave fits arXiv:nucl-ex/0610001 submitted to PRC First published identified spectra for 62.4 GeV Au+Au at RHIC (down to very low pT, a unique PHOBOS measurement) Talk by Gabor Veres

  35. PHOBOS Physics for QM06 • New Analyses: • Elliptic flow fluctuations

  36. PHOBOS Physics for QM06 • New Analyses: • Elliptic flow fluctuations • Two particle correlations

  37. PHOBOS Physics for QM06 • New Analyses: • Elliptic flow fluctuations • Two particle correlations • Extended Analyses: • Elliptic flow in Cu+Cu

  38. PHOBOS Physics for QM06 • New Analyses: • Elliptic flow fluctuations • Two particle correlations • Extended Analyses: • Elliptic flow in Cu+Cu • Charged particle multiplicity

  39. PHOBOS Physics for QM06 • New Analyses: • Elliptic flow fluctuations • Two particle correlations • Extended Analyses: • Elliptic flow in Cu+Cu • Charged particle multiplicity • Anti-particle/particle ratios

  40. PHOBOS Physics for QM06 • New Analyses: • Elliptic flow fluctuations • Two particle correlations • Extended Analyses: • Elliptic flow in Cu+Cu • Charged particle multiplicity • Anti-particle/particle ratios • QM06 Primary Message:PHOBOS has measured large dynamical v2 fluctuations in 200 GeV Au+Au collisions. This suggests that the initial state thermalizes very rapidly, taking a detailed snapshot, which is propagated by the subsequent hydrodynamic evolution.

  41. Future of PHOBOS Physics • Rare events, multiplicity fluctuations and cluster model – poster K. Wozniak • Continue studies of dynamical flow fluctuations • Two-particle correlations with high-pT trigger in spectrometer. • Identified particles at low pT in 200 GeV Au+Au as detailed function of centrality • Spectator breakup in the fragmentation region • Charged particle yields in 200,410 p+p • Phi-meson production Total Number of Hits • TALKS: Rachid Nouicer - v1 and v2 flow (Saturday, 2:40pm, Parallel 2.4) Constantin Loizides - v2 and epart fluctuations (Saturday, 4:20pm, Parallel 2.4)Wei Li - Two-particle correlations (Sunday, 5:00pm, Parallel 3.2)Gabor Veres - Identified particle spectra and ratios (Sunday, 5:00pm, Parallel 3.4) • POSTERS:Burak Alver – Elliptic flow fluctuations (Wednesday, 5:20pm, poster 14)Krzysztof Wozniak - Multiplicity fluctuations (Wednesday, 5:20pm, poster 82)

  42. Backups

  43. From R. Nouicer’s talk (Flow) 44 Measuring flow in PHOBOS 45 Track-based method details 46 Moments of epart From C. Loizides’ talk (v2 fluct.) 47 Overview e-by-e v2 meas. 48 Methodology 49 Glauber overview 50 Glauber Robustness From W. Li’s talk (2-part. corr.) 51 Methodology 52 Cluster size parameterization From G. Veres’ talk (ident. part.) 53 PHOBOS PID capability 54 Particle ratios measurement Summary of Backup Slides

  44. Measuring Flow in PHOBOS Large coverage: |h| < 5.4 Octagon Ring counters Ring counter Vertex detector Spectrometer Hit-based method Track-based method PHOBOS: PRL 89, 222301 (2002) PHOBOS: PRC C72, 051901R (2005)

  45. Track-based method: Robustness of Measurements of v2 vs. pT Octagon Only Rings Only Statistical errors only • Reaction plane subevents • v2(pT) measured in 0 < h < 1.6 Cu+Cu at 200 GeV PHOBOS 2) 3.0 < |h|< 5.4 3) 2.0 < |h|< 5.4 1) 2.0 < |h|< 3.2 Track-based method Spectrometer Preliminary Octagon and Rings The large separation on h between the reaction plane subevents and the measured region reduces the non-flow correlations in track-based (hit-based) method.

  46. Theorists & PHOBOS since QM2005 2 ε part ε part It has been suggested that v2 may scale as instead of • -Bhalerao, Ollitrault – PLB 641, 260 (2006) • - Ollitrault – private communications (2006) • PHOBOS MC • In Collaboration with Ulrich Heinz

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