bulk signatures & properties (soft particle production)
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DESCRIPTIONBulk signatures & properties (soft particle production). Does the thermal model always work ?. Data – Fit ( s ) Ratio. Particle ratios well described by T ch = 160 10 MeV, m B = 24 5 MeV Resonance ratios change from pp to Au+Au Hadronic Re-scatterings!. - PowerPoint PPT Presentation
Bulk signatures & properties(soft particle production)
Does the thermal model always work ? Particle ratios well described by Tch = 16010 MeV, mB = 24 5 MeV Resonance ratios change from pp to Au+Au Hadronic Re-scatterings!Data Fit (s) Ratio
Strange resonances in mediumShort life time [fm/c] K* < *< (1520) < 4 < 6 < 13 < 40 Red: before chemical freeze outBlue: after chemical freeze outMedium effects on resonance and their decay products before (inelastic) and after chemical freeze out (elastic).Rescattering vs. Regeneration ?
Resonance Production in p+p and Au+Au Thermal model :T = 177 MeVmB = 29 MeV P. Braun-Munzinger et.al., PLB 518(2001) 41 D.Magestro, private communication Marcus Bleicher and Jrg Aichelin Phys. Lett. B530 (2002) 81-87. M. Bleicher, private communication Rescattering and regeneration is needed !UrQMD Life time [fm/c] : (1020) = 40 L(1520) = 13 K(892) = 4 ++ = 1.7
Resonance yields consistent with a hadronic re-scattering stageGeneration/suppression according to x-sectionsppL*DpK*pprpKKpppprDMore DLess K*fChemical freeze-outKKf Okr/pD/pf/KK*/KL*/L0.10.20.3Less L*Preliminary
Central STAR AuAu 200 GeV
J. Stachel SQM2003
W. Broniowski et al., nucl-th/0306034
AuAuAuAu Errpppp ErrPBMKrakowUrqmd
Lifetime and centrality dependence from (1520) / and K(892)/KModel includes: Temperature at chemical freeze-out Lifetime between chemical and thermal freeze-out By comparing two particle ratios (no regeneration)
results between : T= 160 MeV => > 4 fm/c (lower limit !!!) = 0 fm/c => T= 110-130 MeV (1520)/ = 0.034 0.011 0.013 K*/K- = 0.20 0.03 at 0-10% most central Au+AuG. Torrieri and J. Rafelski, Phys. Lett. B509 (2001) 239Life time:K(892) = 4 fm/c L(1520) = 13 fm/c
Time scales according to STAR data
Identified Particle Spectra for Au-Au @ 200 GeVThe spectral shape gives us:Kinetic freeze-out temperaturesTransverse flowThe stronger the flow the less appropriate are simple exponential fits:Hydrodynamic models (e.g. Heinz et al., Shuryak et al.) Hydro-like parameters (Blastwave)
Blastwave parameterization e.g.:Ref. : E.Schnedermann et al, PRC48 (1993) 2462
Explains: spectra, flow & HBT
Blastwave: a hydrodynamic inspired description of spectraRbsRef. : Schnedermann, Sollfrank & Heinz,PRC48 (1993) 2462Spectrum of longitudinal and transverse boosted thermal source:Static Freeze-out picture,No dynamical evolution to freezeout
Heavy (strange ?) particles show deviations in basic thermal parametrizations
Blastwave fitsSource is assumed to be: In local thermal equilibrium Strongly boosted , K, p: Common thermal freeze-out at T~90 MeV and ~0.60 c : Shows different thermal freeze-out behavior: Higher temperature Lower transverse flow Probe earlier stage of the collision, one at which transverse flow has already developed If created at an early partonic stage it must show significant elliptic flow (v2)Au+Au sNN=200 GeVSTAR Preliminary 68.3% CL 95.5% CL 99.7% CL
Collective Radial Expansion
increases continuouslyTthsaturates around AGS energy
Strong collective radial expansion at RHIC high pressure high rescattering rate Thermalization likelySlightly model dependenthere: Blastwave model From fits to p, K, p spectra:
Dynamics indicate common freezeout for most particlesChemical FO temperatureAbout 70 MeV difference between Tch and Tth: hadronic phase
Collective anisotropic flow
Elliptic Flow (in the transverse plane)for a mid-peripheral collisionDashed lines: hard sphere radii of nucleiReactionplaneIn-planeOut-of-planeYXRe-interactions FLOW Re-interactions among what? Hadrons, partons or both?In other words, what equation of state?FlowFlow
Anisotropic FlowA.Poskanzer & S.Voloshin (98)zxxyTransverse planeReaction plane0th: azimuthally averaged dist. radial flow1st harmonics: directed flow2nd harmonics: elliptic flowfFlow is not a good terminologyespecially in high pT regionsdue to jet quenching.
Hydrodynamics describes the data Hydrodynamics:strong coupling,small mean free path,lots of interactionsNOT plasma-likeStrong collective flow:elliptic and radial expansion withmass ordering
v2 measurementsMultistrange v2 establishes partonic collectivity ?
# III: The medium consists of constituent quarks ?baryonsmesons
Ideal liquid dynamics reached at RHIC for the 1st time
A more direct handle?elliptic flow (v2) and other measurements (not discussed) evidence towards QGP at RHICindirect connection to geometry
Are there more direct handles on the space-time geometry of collisions?yes ! Even at the 10-15 m / 10-23 s scale !What can they tell us about the QGP and system evolution?
Volumes & Lifetimes= 2nd Law ThermodynamicsIdeal GasRelativistic Fermi/Bose Gasm=0
Pions (3) vs. QGP (37)
Probing source geometry through interferometry(Hanbury-Brown & Twiss (HBT) photons from stars5 fm1 mp sourcer(x)r1r2x1x2p1p2experimentally measuring this enhanced probability: quite challenging
HBT (GGLP) BasicsIn the simplest approximation, the technique has not changed since before most of you were bornGoldhaber, Goldhaber, Lee, and Pais, PR 120:300 (1960)For identical bosons/fermionsBut this (plane wave) approximation neglects many effectsP(p1,p2;r1,r2) =Gaussian source in xi yields Gaussian correlation in conjugate variable qi=p1i-p2iWho made first use of this pedagogic picture?
HBT ComplexitiesWe have neglectedFinal state interactionsCoulomb interactionStrong interactionWeak decaysPosition-momentum correlationsThings more subtle, such as special relativityState of the art analysis incorporates most of these, but not all
Correlation functions for different colliding systemsC2(Qinv)Qinv (GeV/c)STAR preliminaryDifferent colliding systems studied at RHIC
Interferometry probes the smallest scales ever measured !
ReminderTwo-particle interferometry: p-space separation space-time separationPratt-Bertsch (out-side-long) decomposition designed to help disentangle space & timesource sp(x) = homogeneity region [Sinyukov(95)] connections with whole source always model-dependent
More detailed geometryRelative momentum between pions is a vector can extract 3D shape informationRlong along beam directionRout along line of sightRside line of sight
Measured final source shapeSTAR, PRL93 012301 (2004)Expected evolution:
More informationRelative momentum between pions is a vector can extract 3D shape informationRoutRlong along beam directionRout along line of sightRside line of sightRsidestudy as K grows
Why do the radii fallwith increasing momentum ??
Geometric substructure?random (non-)system:all observers measure thewhole source
Why do the radii fallwith increasing momentum ??Its collective flow !!Direct geometrical/dynamical evidencefor bulk behaviour!!!
Flow-generated substructureSpecific predictions of bulk global collective flow:space-momentum (x-p) correlationsfaster (high pT) particles come fromsmaller sourcecloser to the edgerandom (non-)system:all observers measure thewhole source
TimescalesEvolution of source shapesuggests system lifetime is shorter than otherwise-successful theory predicts
Is there a more direct handle on timescales?
Disintegration timescaleRelative momentum between pions is a vector can extract 3D shape informationRoutRlong along beam directionRout along line of sightRside line of sightRside increases with emission timescale
Disintegration timescale - expectation3D 1-fluid HydrodynamicsRischke & Gyulassy, NPA 608, 479 (1996)withtransitionwithtransitionLong-standing favorite signature of QGP:increase in , ROUT/RSIDE due to deconfinement confinement transitionexpected to turn on as QGP energy threshold is reached
Disintegration timescale - observationRHICno threshold effect seenRO/RS ~ 1
Disintegration timescale - observationN()no threshold effect seenRO/RS ~ 1toy model calculations suggest very short timescalesrapid, explosive evolutiontoo explosive for real models which explain all other data
Time scales according to STAR datadN/dt1 fm/c5 fm/c10 fm/c20 fm/ctimeChemical freeze outKinetic freeze outBalance function (require flow)Resonance survival Rlong (and HBT wrt reaction plane)Rout, Rside
Summary: global observables Initial energy density high enough to produce a QGP
e 10 GeV/fm3 (model dependent)
High gluon density dN/dy ~ 800-1200
Proof for high density matter but not for QGP
Summary of particle identified observables Statistical thermal models appear to work well at SPS and RHICChemical freeze-out is close to TCHadrons appear to be born into equilibrium at RHIC (SPS)Shows that what we observe is consistent with thermalizationThermal freeze-out is common for all particles if radial flow is taken into account. T and bT are correlatedFact that you