bulk signatures & properties (soft particle production)

Download Bulk signatures & properties (soft particle production)

Post on 24-Jan-2016




0 download

Embed Size (px)


Bulk 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 [1]:T = 177 MeVmB = 29 MeV[1] P. Braun-Munzinger et.al., PLB 518(2001) 41 D.Magestro, private communication[2] Marcus Bleicher and Jrg Aichelin Phys. Lett. B530 (2002) 81-87. M. Bleicher, private communication Rescattering and regeneration is needed !UrQMD [2]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

  • Bose-Einstein correlations

  • 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


View more >