hadron correlations and parton recombination

Download Hadron Correlations and Parton Recombination

Post on 30-Jan-2016

36 views

Category:

Documents

0 download

Embed Size (px)

DESCRIPTION

Hadron Correlations and Parton Recombination. Rainer Fries University of Minnesota. Hard Probes 2006 Asilomar June 11, 2006. q. q. Hard Probes. Hard processes as well controlled probes to measure properties of the QGP. - PowerPoint PPT Presentation

TRANSCRIPT

  • Hadron Correlations and Parton RecombinationRainer FriesUniversity of Minnesota

    Hard Probes 2006 Asilomar June 11, 2006

    Recombination and Hadron Correlations

  • Hard ProbesHard processes as well controlled probes to measure properties of the QGP.

    Hard probes high momentum transfer, high quark mass, high temperature

    Careful: which value of our scale is sufficiently high depends strongly on the question we ask.

    Recombination and Hadron Correlations

  • Hard ProbesCareful: which value of our scale is sufficiently high depends strongly on which question we ask.

    Single inclusive pion spectrum in p+p: pQCD works from PT 1 GeV

    But: single inclusive spectra in A+A: dont work up to 5 GeV, Maybe not even at 10 GeV ??

    Recombination and Hadron Correlations

  • Why Recombination: B/MEnhanced baryon yieldp/ ~ 1 in Au+Au (for PT ~ 2 4 GeV/c)p/ ~ 0.3 in p+p, p/ ~ 0.1.0.2 in e++e-

    PHENIX

    Recombination and Hadron Correlations

  • Why Recombination: RAANo jet quenching for baryons? (RAA ~ RCP ~ 1)In the range PT ~ 1.5 5 GeV/c.Jet quenching not on the parton level?

    PHENIX

    Recombination and Hadron Correlations

  • Why Recombination: v2 scalingDifferent v2 saturation for mesons and baryons

    Recombination and Hadron Correlations

  • Baryon/Meson AnomalyGeneral baryon/meson pattern: p, , , versus K, , , K* In the region PT 1.5 6 GeV/c

    Recombination and Hadron Correlations

  • Baryon/Meson AnomalyGeneral baryon/meson pattern: p, , , versus K, , , K* In the region PT 1.5 6 GeV/cNo mass effect: behaves like a pion (m mp , m >> m)STAR Preliminary

    Recombination and Hadron Correlations

  • Baryon/Meson AnomalyGeneral baryon/meson pattern: p, , , versus K, , , K* No mass effect: behaves like a pion (m mp , m >> m) v2 of < v2 of proton; behaves like meson

    Recombination and Hadron Correlations

  • Baryon/Meson AnomalyGeneral baryon/meson pattern: p, , , versus K, , , K*No mass effect: behaves like a pion (m mp , m >> m)

    Hadron properties do not matter in this kinematic region.

    Only the number of valence quarks!

    We catch a glimpse of hadronization

    Recombination and Hadron Correlations

  • Hadron CorrelationsAway-side jets vanishesRidge on the near sideAway side gone/diffuseSTARA+Ap+pBroadening+pedestal on near sideWiedemann et al.

    Recombination and Hadron Correlations

  • Signatures in CorrelationsDeviations from jet shapes below PT = 5 GeV/cE.g. broadening of the near-side jet cone

    Width of the peak in STAR preliminary

    Recombination and Hadron Correlations

  • Fragmentation?Hard processes + vacuum fragmentation are ruled out below 4 6 GeV/c because of RHIC results onhadron chemistry elliptic flow v2Recombination idea: hadrons at intermediate PT from recombination of soft partons

    Recombination and Hadron Correlations

  • Recombination!Fragmentation = limit of hadronization for very dilute systems (parton density 0)Recombination = hadronization in the opposite limit: thermalized phase of partons just above Tc

    Recombination and Hadron Correlations

  • Recombination revisitedBasic assumptionsRecombine valence quarks

    Instantaneous projection of quark states on hadron states

    For simplicity: factorize 2-parton distribution in 1-parton distributions

    No correlations assumed!

    Recombination and Hadron Correlations

  • Recombination revisitedConspiracy of thermal distributions and large Pi. e. P >> M, kT (collinear situation); Boltzmann w

    No dependence on shape of !Baryon ~ meson

    Reco Frag competition fragmenting parton:ph = z p, z

  • Recombination & FragmentationDual model of hadron production: Recombination + pQCD/fragmentation to describe hadron production at RHIC for PT > 12 GeV/c

    With B. Muller, C. Nonaka, S. A. Bass

    For RHIC:

    T = 175 MeVRadial flow = 0.55Constituent quark massesFit to pion data predictive power for all other hadron species

    Recombination and Hadron Correlations

  • Spectra & RatiosGood description of spectra, ratios, RAA for all measured hadron speciesRJF, Muller, Nonaka, Bass

    Recombination and Hadron Correlations

  • Elliptic Flow ScalingAssume universal elliptic flow v2p of the partons before the phase transitionRecombination prediction:

    Scaling works for all hadrons

    Deviations for pions arise mostly from resonance decays (Greco et al.)

    Recombination and Hadron Correlations

  • How robust is v2 scaling?Scaling law uses the most primitive approximationsMomentum shared equally between constituents

    Expect correction for realistic wave function with finite width.

    Numerically: effects are small

    Momentum shared: fractions x and 1-x

    Recombination and Hadron Correlations

  • Fate of the Gluons?Are there gluons or sea quarks?

    No effect on particle yields for thermal spectra!

    Resulting elliptic flow for hadrons does not obey scalingFor equally shared momenta:

    Recombination and Hadron Correlations

  • Zooming in on v2 ScalingWe proposed a new variable: baryon/meson v2 asymmetry (B-M)/(B+M) for scaled v2.

    First results: Size and sign of the effect predicted correctly.

    Gluons could be accommodated. P. Sorensen, QM 05

    Recombination and Hadron Correlations

  • Hadron CorrelationsHow can hadrons at intermediate PT show jet-like structure?

    Recombination and Hadron Correlations

  • Hadron CorrelationsHow can hadrons at intermediate PT show jet-like structure?

    Naturally through soft-hard recombinationSoft-hard hadrons and jet hadrons correlatedRudy Hwas talk

    Naturally if the recombining partons are correlated

    Recombination and Hadron Correlations

  • 2-Particle CorrelationsRecombination of mesons A, B from partons 1,2,3,4

    New: permit 2-particle correlations

    Possible ansatz

    Recombination and Hadron Correlations

  • Hot SpotsStrong energy loss (dE/dx up to 14 GeV/fm) a lot of quenched/partially thermalized jetsLocalized deposition of energy and momentumHot Spots?

    Hot spot can be correlated with remaining jetPartons in the hot spot can be correlated with themselvesAdd collective effects: Mach cone?

    Recombination and Hadron Correlations

  • Associated YieldList of assumptionsOnly near side; integrate rapiditySmall correlations, keep only terms linear in c0 and v2Narrow wave functionsCorrelations constant over volume VcAssociated yield

    Here

    Recombination and Hadron Correlations

  • Amplification of CorrelationsQ: Amplification factorCount 2-parton pairs between the 2 hadrons; for effects linear in c0, only 1 correlation allowed.

    Uncorrelated background (for meson-meson)

    4 pairings that lead to meson correlations2 pairings without correlating the mesons

    Q=4Meson-mesonQ=6Meson-baryonQ=9Baryon-baryon

    Recombination and Hadron Correlations

  • Numerical ExampleUsing Duke parametrization consistent with spectra and ratios!

    Consistency with PHENIX data can be reached.Large correlationsfrom Frag-Frag.Lower associated yield when adding SS-SSwithout correlations(C0=0), especially for baryon triggers.F-F and SS-SS withC0=0.08x100/Npart(Vc~const.)Meson triggerBaryon triggerRJF, Muller, Bass: Phys. Rev. Lett. 94, 122301 (2005)

    Recombination and Hadron Correlations

  • Identified Particles

    Recombination and Hadron Correlations

  • Hadrochemistry in Jet ConesThe baryon/meson ratio can be an indicator for the amount of thermalization in a jetFar side produces more baryons than near side

    Recombination and Hadron Correlations

  • Where is Fragmentation?Below PT = 4 6 GeV/c: no go for (hadronic) hard probesProblems for pQCD + fragmentation even above PT = 6 GeV/c ??Baryon/meson ratio still too large above 5 GeV/c ??

    Recombination and Hadron Correlations

  • Where is Fragmentation?Below PT = 4 6 GeV/c: no go for (hadronic) hard probesProblems for pQCD + fragmentation even above PT = 6 GeV/c ??Baryon/meson ratio still too large above 5 GeV/c ??

    v2 from jet quenching ??

    Recombination and Hadron Correlations

  • Where is Fragmentation?Below PT = 4 6 GeV/c: no go for (hadronic) hard probesProblems for pQCD + fragmentation even above PT = 6 GeV/c ??Baryon/meson ratio still too large above 5 GeV/c ??

    v2 from jet quenching ??

    No difference between quark and gluon jets ??

    It may be soft-hard recombination.Pick-up of soft quarks by jets

    Recombination and Hadron Correlations

  • Soft/Hard RecombinationAttempt to treat reco + fragmentation consistentlyHwa and Yang: jets as cones of parton showers at late times; fitted to fragmentation functionsMajumdar, Wang and Wang: 2- and 3- quark constituent quark fragmentation + recombination ( Q2 evolution) Recombine all partons:Partons = soft/thermal + showers from jetsTwo parton distribution function:

    Partons from 2 jetsPartons from 1 jetssoft-showersoft-soft

Recommended

View more >