May, LANLS. Manly - Univ. of Rochester1 The Information of Flow Steven Manly Univ. of Rochester Los Alamos National Laboratory May 5, Not a systematic review of historical/RHIC/PHOBOS results. More a personal tour of what I find interesting.
May, LANLS. Manly - Univ. of Rochester2 Inquiring minds want to know... Yo! What holds it together?
May, LANLS. Manly - Univ. of Rochester3 What flies out Pattern of debris
May, LANLS. Manly - Univ. of Rochester4 Quantum Chromodynamics - QCD Similar to QED … But... Gauge field carries the charge q q distance energy density, temperature relative strength asymptotic freedom qq qq confinement q q
May, LANLS. Manly - Univ. of Rochester5 Why do we believe QCD is a good description of the strong interaction? Deep inelastic scattering: There are quarks. From D.H. Perkins, Intro. to High Energy Physics
May, LANLS. Manly - Univ. of Rochester6 Why do we believe QCD is a good description of the strong interaction? No direct observation of quarks: confinement
May, LANLS. Manly - Univ. of Rochester7 Why do we believe QCD is a good description of the strong interaction? P. Burrows, SLAC-PUB7434, 1997 R. Marshall, Z. Phys. C43 (1989) 595 Need the “color” degree of freedom
May, LANLS. Manly - Univ. of Rochester8 Why do we believe QCD is a good description of the strong interaction? Event shapes e + e - Z o qqe + e - Z o qqg
May, LANLS. Manly - Univ. of Rochester9 Why do we believe QCD is a good description of the strong interaction? Measure the coupling P. Burrows, SLAC-PUB7434, 1997
May, LANLS. Manly - Univ. of Rochester10 Strong interaction is part of our heritage
May, LANLS. Manly - Univ. of Rochester11 Chiral symmetry breaking: the “other” source of mass qq q QCD vacuum Quark condensate A naïve view … Strongly interacting particles interact with the vacuum condensate … which makes them much heavier than the constituent quark masses.
May, LANLS. Manly - Univ. of Rochester12
May, LANLS. Manly - Univ. of Rochester13 Signatures/observables Energy density or number of participants Measured value Strange particle enhancement and particle yields Temperature J/ and ’ production/suppression Vector meson masses and widths identical particle quantum correlations DCC - isospin fluctuations Flow of particles/energy (azimuthal asymmetries) jet quenching Each variable has different experimental systematics and model dependences on extraction and interpretation MUST CORRELATE VARIABLES
May, LANLS. Manly - Univ. of Rochester14 “Flow” = patterns in the energy, momentum, or particle density distributions that we use to ferret out clues as to the nature of the collision/matter Reaction plane x z y M. Kaneta To what extent is the initial geometric asymmetry mapped into the final state?
May, LANLS. Manly - Univ. of Rochester15 Collision region is an extruded football/rugby ball shape Central Peripheral
May, LANLS. Manly - Univ. of Rochester16 (reaction plane) Flow quantified dN/d( R ) = N 0 (1 + 2V 1 cos ( R ) + 2V 2 cos (2( R ) +... )
May, LANLS. Manly - Univ. of Rochester17 (reaction plane) dN/d( R ) = N 0 (1 + 2V 1 cos ( R ) + 2V 2 cos (2( R ) +... ) Directed flow Flow quantified
May, LANLS. Manly - Univ. of Rochester18 (reaction plane) dN/d( R ) = N 0 (1 + 2V 1 cos ( R ) + 2V 2 cos (2( R ) +... ) Elliptic flow Flow quantified
May, LANLS. Manly - Univ. of Rochester19 (reaction plane) dN/d( R ) = N 0 (1 + 2V 1 cos ( R ) + 2V 2 cos (2( R ) +... ) Higher terms Flow quantified
May, LANLS. Manly - Univ. of Rochester20 b (reaction plane)
May, LANLS. Manly - Univ. of Rochester21 Flow as an experimental probe Sensitive to interaction length/cross section/degree of thermalization Sensitive to very early times and particle velocities since asymmetry is self-quenching Probes longitudinal uniformity
May, LANLS. Manly - Univ. of Rochester22 Subevent technique: correlate reaction plane in one part of detector to asymmetry in track pattern in other part of detector Correct for imperfect reaction plane resolution -2.0 < < -0.1 SubE (a)SubE (b) nana nbnb 0.1 < < 2.0 dependence of the multiplicity Flow: basic method Poskanzer and Voloshin, Phys. Rev. C58 (1998) 1671
May, LANLS. Manly - Univ. of Rochester23 The PHOBOS Detector (2001) Ring Counters Time of Flight Spectrometer 4 Multiplicity Array - Octagon, Vertex & Ring Counters Mid-rapidity Spectrometer TOF wall for high-momentum PID Triggering - Scintillator Paddles Counters - Zero Degree Calorimeter (ZDC) Vertex Octagon ZDC z y x Paddle Trigger Counter Cerenkov 1m silicon pad readout channels
May, LANLS. Manly - Univ. of Rochester24 Au-Au event in the PHOBOS detector
May, LANLS. Manly - Univ. of Rochester25 Flow in PHOBOS
May, LANLS. Manly - Univ. of Rochester26 coverage Data at 19.6, 62.3, 130 and 200 GeV 1m 2m 5m coverage for vtx at z=0
May, LANLS. Manly - Univ. of Rochester27 Pixelized detector Hit saturation, grows with occupancy Sensitivity to flow reduced Can correct using analogue energy deposition –or- measure of occupied and unoccupied pads in local region assuming Poisson statistics Poisson occupancy correction
May, LANLS. Manly - Univ. of Rochester28 Acceptance (phase space) weighting Octagonal detector Require circular symmetry for equal phase space per pixel Pixel’s azimuthal phase space coverage depends on location Relative phase space weight in annular rings = -1
May, LANLS. Manly - Univ. of Rochester29 z Dilutes the flow signal Remove Background Estimate from MC and correct flow signal Non-flow background + Non-flow Backgrounds
May, LANLS. Manly - Univ. of Rochester30 Background suppression Works well in Octagon dE (keV) cosh Background! Technique does not work in rings because angle of incidence is ~90 Beampipe Detector Demand energy deposition be consistent with angle
May, LANLS. Manly - Univ. of Rochester31 RingsN OctagonRingsP Spec holes Vtx holes
May, LANLS. Manly - Univ. of Rochester32 Determining the collision point High Resolution extrapolate spectrometer tracks Low Resolution octagon hit density peaks at vertex z position
May, LANLS. Manly - Univ. of Rochester33 RingsN OctagonRingsP Spec holes Vtx holes Detector symmetry issues where SPEC vertex efficiency highest Most data taken with trigger in place to enhance tracking efficiency
May, LANLS. Manly - Univ. of Rochester34 RingsN Octagon RingsP Offset vtx method Limited vertex range along z Subevents for reaction plane evaluation Good azimuthal symmetry Fewer events, no 19.6 GeV data Gap between subevents relatively small Technique used for published elliptic flow signal at 130 GeV
May, LANLS. Manly - Univ. of Rochester35 RingsN OctagonRingsP Full acceptance method Vertex range -10<z<10 Subevents for reaction plane evaluation vary with analysis Good statistics, 19.6 GeV data available Gap between subevents large Requires “hole filling” Technique used for elliptic and directed flow signal at all energies (only directed flow released to date, elliptic flow coming soon)
May, LANLS. Manly - Univ. of Rochester36 Dealing with the holes RingsN Octagon RingsP Inner layer of vertex detector fills holes in top and bottom. Must map hits from Si with different pad pattern and radius onto a “virtual” octagon Si layer
May, LANLS. Manly - Univ. of Rochester37 Dealing with the holes RingsN Octagon RingsP Fill spectrometer holes by extrapolating hit density from adjoining detectors onto a virtual Si layer. (Actual spec layer 1 is much smaller than the hole in the octagon.)
May, LANLS. Manly - Univ. of Rochester38 RingsN OctagonRingsP Track-based method Vertex range -8<z<10 Subevents for reaction plane Momentum analysis 200 GeV data Gap between tracks and subevents large Little/no background
May, LANLS. Manly - Univ. of Rochester39 Elliptic Flow at 130 GeV Phys. Rev. Lett (2002) (PHOBOS : Normalized Paddle Signal) Hydrodynamic limit STAR: PRL86 (2001) 402 PHOBOS preliminary Hydrodynamic limit STAR: PRL86 (2001) 402 PHOBOS preliminary Thanks to M. Kaneta
May, LANLS. Manly - Univ. of Rochester40 STAR 130 GeV 4-cumulant STAR 130 GeV 2-cumulant STAR 130 GeV Reaction Plane 5-53% central Preliminary PHOBOS 200 GeV 0-55% central p t (GeV/c) v2v2 Elliptic flow vs p T
May, LANLS. Manly - Univ. of Rochester41 Elliptic flow vs p T at low p T PRL 91 (2003) PRL 87 (2001) Asymmetry largest at early time, expect v 2 to grow with p T Expect growth to be less for heavier particles … move slower.
May, LANLS. Manly - Univ. of Rochester42 Jet-quenching: hard parton interacts with medium, which softens the momentum spectrum in A-A relative to pp
May, LANLS. Manly - Univ. of Rochester43 Slow partons down, sample smaller asymmetry and elliptic flow saturates Elliptic flow vs p T at high p T
May, LANLS. Manly - Univ. of Rochester44 Molnar and Voloshin, nucl-th/ Partonic energy loss alone leads drop at very large pT and does not account for meson/baryon differences Quark coalescence vs. fragmentation nucl-ex/ nucl-ex/
May, LANLS. Manly - Univ. of Rochester45 Xhangbu Xu, Quark Matter 2004 Quark coalescence-NCQ scaling ’s affected by resonance decays? Dong, Esumi, Sorensen, N.Xu, Z,Xu, nucl-th/
May, LANLS. Manly - Univ. of Rochester46 Elliptic flow vs width of bin PHOBOS Preliminary central 3-15% midcentral 15-25% peripheral 25-50% Hit-based method h±h± M. Belt-Tonjes, Quark Matter 2004 Ben’s MVD analysis
May, LANLS. Manly - Univ. of Rochester47 Track-based Hit-based peripheral 25-50% h ± v2v2 PHOBOS Preliminary Track-based Hit-based midcentral 15-25% h ± v2v2 PHOBOS Preliminary central 3-15% h ± Track-based Hit-based v2v2 PHOBOS Preliminary v2 vs. 200 GeV method comparison
May, LANLS. Manly - Univ. of Rochester48 T. Hirano Hydro does not model the dependence well
May, LANLS. Manly - Univ. of Rochester49 Energy Energy y-y T y Feynman/Bjorken vs. Landau?? P. Steinberg Nucl-ex/
May, LANLS. Manly - Univ. of Rochester50 Directed flow Charged hadrons 6-55% central AuAu
May, LANLS. Manly - Univ. of Rochester51 v1v1 PHOBOS Preliminary PHOBOS AuAu √s NN =19.6 GeV NA49 PbPb √s NN =17.2 GeV Phys.Rev.C68, , % Minimum Bias h±h± ±± 19.6 GeV AuAu & 17.2 GeV PbPb 19.6 GeV AuAu & 17.2 GeV PbPb
May, LANLS. Manly - Univ. of Rochester52 Xhangbu Xu, Quark Matter 2004 Directed Flow comparison at 200 GeV Ben’s MVD flow analysis!
May, LANLS. Manly - Univ. of Rochester53 Examine energy dependence by going into frame of reference of target
May, LANLS. Manly - Univ. of Rochester54 “Limiting fragmentation” of elliptic flow PHOBOS Preliminary v PHOBOS v 2 130
May, LANLS. Manly - Univ. of Rochester55 Scaled by “Kolb factor” PHOBOS Preliminary v PHOBOS v “Limiting fragmentation” of elliptic flow
May, LANLS. Manly - Univ. of Rochester56 Energy y-y T
May, LANLS. Manly - Univ. of Rochester57 Conclusions P. Steinberg ? Interaction length is short - early thermalization likely Hydro/Bjorken/Feynman works well at mid- Flow gives evidence for partonic energy loss in medium and quark coalescence Hydro/Bjorken/Feynman( ) inconsistent with multiplicity and elliptic flow data. Maybe not with directed flow? Landau( ) consistent with multiplicity and elliptic flow No indication of major change in nature of particle production as function of RHIC results/flow are exciting … and a bit puzzling!
May, LANLS. Manly - Univ. of Rochester58
The end Backup slides follow
May, LANLS. Manly - Univ. of Rochester60 quarks leptons Gauge bosons u c t d s b e W, Z, , g, G g Hadrons Baryons qqq qq mesons p = uud n = udd K = us or us = ud or ud Strong interaction nuclei e atoms Electromagnetic interaction
May, LANLS. Manly - Univ. of Rochester61 What forces exist in nature? What is a force? How do forces change with energy or temperature? How has the universe evolved? How do they interact?
May, LANLS. Manly - Univ. of Rochester62 Cumulant Method Measure the Generating function G, event-by-event Statistical average of G,, gives Cumulants generating function % M is charged Multiplicity
May, LANLS. Manly - Univ. of Rochester63 Cumulant Method Expansion of Cumulants generation function is interesting, especially diagonal terms (See more details in J-Y. Ollitrault) because they are related to flow (global correlation) two-particle correlation, 4-particle, 6-particle correlation, etc..
May, LANLS. Manly - Univ. of Rochester64 ( ) PHOBOS Preliminary v ( ) PHOBOS v Minimum Bias h±h± v 2 vs. at 130 and 200 GeV AuAu ( ) PRL 89, (2002) Hit-based method ( ) Nucl.Phys. A715 (2003)
May, LANLS. Manly - Univ. of Rochester65 y vs. Get a suppression in the spectra which is largest at low p t and small | |. It vanishes at large | | and high p t. Gives the famous dip in multiplicity distribution. If integrating v 2 over pt, get suppression of the lower pt part (where v 2 is small) and the signal should rise.
May, LANLS. Manly - Univ. of Rochester66 Transformation of spectra from to y leads to suppression of multiplicity at low p t and low | | This leads to an enhancement of inclusive v 2 at mid- P. Kolb, Proc. of 17 th Winter Workshop on Nuclear Dynamics (2001) T. Hirano, BNL-Riken Workshop on Collective Flow and the QGP (Nov. 2003) ~10%
May, LANLS. Manly - Univ. of Rochester67 Relativistic heavy ions Two concentric superconducting magnet rings, 3.8 km circum. A-A (up to Au), p-A, p-p collisions, eventual polarized protons Funded by U.S. Dept. of Energy $616 million Construction began Jan. 1991, first collisions June 2000 Annual operating cost $100 million AGS: fixed target, 4.8 GeV/nucleon pair SPS: fixed target, 17 GeV/nucleon pair RHIC: collider, 200 GeV/nucleon pair LHC: collider, 5.4 TeV/nucleon pair
May, LANLS. Manly - Univ. of Rochester68 The view from above
May, LANLS. Manly - Univ. of Rochester69 STAR
May, LANLS. Manly - Univ. of Rochester70 Au-Au collision in the STAR detector
May, LANLS. Manly - Univ. of Rochester71 Isometric of PHENIX Detector
May, LANLS. Manly - Univ. of Rochester72 Brahms experiment From F.Videbœk
May, LANLS. Manly - Univ. of Rochester73 Central Part of the Detector (not to scale) 0.5m
May, LANLS. Manly - Univ. of Rochester74 Beamline Terminology: angles
May, LANLS. Manly - Univ. of Rochester75 Beamline Terminology: angles Pseudorapidity = = Lorentz invariant angle with repect to the beampipe
May, LANLS. Manly - Univ. of Rochester76 Terminology: angles = azimuthal angle about the beampipe Beamline
May, LANLS. Manly - Univ. of Rochester77 “Spectators” Zero-degree Calorimeter “Spectators” Paddle Counter peripheral collisions central collisions N ch N part 6% Terminology: centrality Thanks to P. Steinberg for constructing much of this slide “Participants”
May, LANLS. Manly - Univ. of Rochester78