Charm with STAR Kai Schweda, University of Heidelberg A. Dainese, - - PowerPoint PPT Presentation

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Charm with STAR Kai Schweda, University of Heidelberg A. Dainese, - - PowerPoint PPT Presentation

May 26, 2023 307 likes •606 views

Charm with STAR Kai Schweda, University of Heidelberg A. Dainese, X. Dong, J. Faivre, Y. Lu, H.G. Ritter, L. Ruan, A. Shabetai, P. Sorensen, N. Xu, H. Zhang, Y. Zhang. 1 Physics of High Baryon Density,Trento, May 29 June 2, 2006 Nuclear

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1 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Charm with STAR

Kai Schweda, University of Heidelberg

  • A. Dainese, X. Dong, J. Faivre, Y. Lu, H.G. Ritter, L. Ruan,
  • A. Shabetai, P. Sorensen, N. Xu, H. Zhang, Y. Zhang.
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Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Nuclear phase diagram

1) RHIC heavy-flavor program / LHC:

  • Study medium properties at RHIC
  • pQCD in hot and dense environment

2) RHIC energy scan / GSI program:

  • Search for the possible phase boundary.
  • Chiral symmetry restoration

Energy scan T a k e n f r

  • m

P . S a n g e r

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3 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Outline

1) Introduction 2) Charm production in STAR 3) Heavy − quark collectivity 4) Summary

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4 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Heavy flavor in pQCD

  • R. Vogt Int. J. Mod. Phys. E 12(2003)211

D mesons , Ψ’, χ

Large Q value needed (>≈3GeV) powerful test for pQCD calculation

PDF

ccbar pQCD

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5 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Heavy-Flavor Quarks

Plot: B. Mueller, nucl-th/0404015.

Symmetry is broken: QCD dynamical mass EW Higgs mass Even in a QGP, charm and beauty quark-mass heavy ! If heavy quarks flow: frequent interactions among all quarks light quarks (u,d,s) likely to be thermalized

Plot: B. Mueller, nucl-th/0404015.

Mass (MeV/c2) 106 105 104 103 102 10 1

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6 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Charm-quark Elliptic Flow

  • V. Greco et al., PLB 595(2004)202.

Coalescence approach AMPT transport model

  • B. Zhang et al.,PRC 72(2005) 024906.

D = (cu) Heavy-quark collective flow observable in D-meson v2 Large partonic cross sections needed Frequent interactions Challenge to theory ?

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7 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

The key point is to determine

Heavy-Flavor Collectivity Heavy-Flavor Collectivity

D0, D±, D+

s, Λ+ C, J/ψ, …

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Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Au +Au @ 20, 62, 130, 200 GeV Cu + Cu @ 20, 62, 200 GeV d + Au @ 200 GeV p + p @ 200, 400 GeV

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9 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

The STAR Detector

Coils

D recon. from hadronic decay channels: TPC (+TOF) electrons: TPC, TPC+TOF, TPC+EMC Advantage: Direct D-meson reconstruction large acceptance, |φ| < 2p, |η| < 1.5

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10 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

STAR:

Mixed-event technique benefiting from large acceptance of the TPC

Direct Open Charm Reco.

%) 8 . 3 ( %), 68 (

*

π π K D D D

s

→ →

±

%) 8 . 3 (

+ −

→ π K D

STAR Preliminary

STAR, PRL, 94, 062301 (2005)

  • A. Tai, QM04

d+Au 200 GeV

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11 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Charm(Bottom) e − Spectrum

Three independent analyses using different sub-detectors σcc = 1.4 ± 0.2 ± 0.4 mb PHENIX, Au+Au: σcc= 0.62 ± 0.06 ± 0.16 mb Need direct open charm reconstruction ! (D0 K + π)

EMC -- STAR preliminary

STAR: PRL 94, 062301 (2005); PHENIX: PRL 94, 082301 (2005).

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12 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

2 3 4 5 6 7 8 9 10 pT (GeV) 0.0 0.2 0.4 0.6 0.8 1.0 Single Electron RAA(pT) PHENIX preliminary STAR preliminary Rad DGLV only Rad + elastic BT dNg/dy = 1000 Rad + elastic TG c and b: L=6fm

Heavy-flavor Energy Loss

Heavy-flavor decay electrons: Probe interaction with medium Induced gluon radiation only Plus elastic collisions Collisional Collisional Energy loss nergy loss important, important, also for l also for light ght quarks* ! quarks* ! Gluon radiation is NOT Gluon radiation is NOT dominant mechanism for dominant mechanism for energy loss ! energy loss !

Calculations: M. Djordjevic et al., nucl-th/0507019; *J. Alam et al., hep-ph/0604131.

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13 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Total Charm X−section

1) STAR > pQCD PHENIX >~ pQCD 2) Charm total cross section is a critical reference for J/ψ suppression/enhanc ement determination. 3) Scales (μF and µR ) may be energy dependent.

STAR, PRL, 94, 062301 (2005)

  • R. Vogt, private communication
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14 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Total Charm vs Centrality

Total cross section scales with binary collisions Disrepancy between experiments pQCD by factor 2−3 too low Charm is a good Charm is a good early stage probe early stage probe ! Need precise Need precise calibration ! calibration !

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15 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Anisotropy Parameter v2

y x p

y

px

coordinate-space-anisotropy ⇔ momentum-space-anisotropy

ε = 〈y 2 − x 2〉 〈y 2 + x 2〉 v2 = cos2ϕ , ϕ = tan−1( py px )

Initial/final conditions, EoS, degrees of freedom

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16 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Non-photonic electron v2

c (b) e + X Large syst. uncertainties due to large background charm collective flow at pt < 2GeV/c v2(e) favors non-zero v2(c) at pT(e)<2 GeV/c.

  • V. Greco et al.

PLB 595(2004)202

  • B. Zhang et al.

nucl-th/0502056

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17 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

J/ψ Enhancement at RHIC(LHC)

Statistical hadronization strong centrality dependence

  • f J\ψ yield at LHC

Need total charm yields ! Measure D Measure D0, D , D±, , Λc Probe deconfinement Probe deconfinement and thermalization and thermalization

Calculations:P. Braun Munzinger, K. Redlich, and J. Stachel, nucl-th/0304013.

∝ σcc

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18 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

J/ψ at RHIC

Yellow band: allowed range by open charm from STAR and PHENIX Large uncertainty from

  • pen charm cross section !

Statistical Charm- Statistical Charm- Hadronization Hadronization might not ight not dominate at dominate at RHIC RHIC Check at LHC… Check at LHC… Need precise open Need precise open charm reference ! charm reference !

  • P. Braun-Munzinger et al.
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19 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Multiply Heavy-flavored Hadrons

  • F. Becattini, Phys. Rev. Lett. 95, 022301 (2005);
  • P. Braun Munzinger, K. Redlich, and J. Stachel, nucl-th/0304013.

Statistical hadronization

  • de-confined heavy-quarks
  • equilibrated heavy-quarks

Enhancement up to x1000 ! Measure Ξcc, Ωcc, Bc, (Ωccc) Need total charm yields Probe deconfinement Probe deconfinement and and thermalization thermalization at LHC t LHC QGP ! QGP !

Quarks and gluons hadrons

Pb+Pb Ωccc / D : p+p

x1000

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20 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

D − Meson Pair Correlations

∆φ

Pythia Calcs.: H. Woehri, priv. comm. Hadronic Transport Model: E.L. Bratkovskaya et al., PRC 71 (2005) 044901.

ccbar pair production: DDbar pairs are correlated ! Here: ∆φ correlation If charm equili If charm equilibrates brates correlations vanish ! correlations vanish ! Influence of hadroni Influence of hadronic scattering (small) ? scattering (small) ?

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21 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Hadronic Re-scattering

Hadronic re-scattering can not completely wash out DD-correlations Frequent partonic re-scattering needed light quark t ght quark thermalization hermalization !

  • M. Bleicher at al., subm. to Phys. Rev. Lett.
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22 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

STAR Detector Upgrade

Heavy Flavor Tracker Full Barrel MRPC - TOF

  • D0 K + π, cτ = 123µm
  • Measure decay vertex, σ ≤ 50µm
  • enhance S/B by factor 100

precise heavy-flavor precise heavy-flavor measurements ! measurements !

Active Pixel Sensors:

  • M. Winter et al., IReS/LEPSI, Strasbourg.

At µ-RHIC: measure Ω elliptic flow!

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23 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Measure Vector Mesons*

Detectors ω φ TPC+TOF 8 M 2 M TPC+TOF+SVT+HFT 200K 100K

φ e+e- : leptons do not re-scatter probe the medium at early stage Background: γ e+e- HFT discriminates background ! Need low mass detector

γ e+e-

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24 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Summary

Charm program at RHIC well established Need precision measurements on spectra, elliptic flow and yields of D0, D±, D+s, Λ+C, J/ψ Probe (u,d,s)-quark thermalization STAR: µVertex + full ToF (2008+)

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25 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

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26 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

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27 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Spectrum coverage

σcc = 1.1 ± 0.1 ± 0.3 mb <pT> ~ 1.3 GeV/c 90% 15% The reconstructed D measurement has much smaller systematic uncertainties in determining the total cross section.

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28 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

d + Au Au + Au

STAR Highlight talk 1.13 ± 0.09 ± 0.42 mb in Au + Au

Approximately Nbin scaling from d+Au to Au+Au!

1.4 ± 0.2 ± 0.4 mb in d + Au

As expected --- charm quarks are mostly created from initial NN interactions!