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Study of the Number of Constituent Quark Scaling of v 2 at High p T Na Li

Study of the Number of Constituent Quark Scaling of v 2 at High p T Na Li ( for the STAR Collaboration ) Institute of Particle Physics, Wuhan, China Brookhaven National Laboratory, Upton, USA. Outline: Introduction STAR Detector and Dataset

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Study of the Number of Constituent Quark Scaling of v 2 at High p T Na Li

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  1. Study of the Number of Constituent Quark Scaling of v2 at High pT Na Li (for the STAR Collaboration) Institute of Particle Physics, Wuhan, China Brookhaven National Laboratory, Upton, USA • Outline: • Introduction • STAR Detector and Dataset • v2 and Number of Constituent Quark (NCQ) scaling • Summary

  2. hadronic partonic Elliptic Flow (v2) Coordinate-Space Anisotropy Momentum-Space Anisotropy interactions • Elliptic flow: • Good probe of the early stage of the collision.

  3. Motivation Ideal hydro: P. Huovinen and P. V. Ruuskanen, Annu. Rev. Nucl. Part. Sci. 56, 163 (2006) and private communication • NCQ Scaling -- v2h = nqv2q • Why ? • – strong evidence of partonic collectivity • Where ? • – locate the range • How ? • – breaking pattern STAR preliminary Hydro ? Recombination /Coalescence ? Jet ? • Further our understanding of NCQ scaling

  4. STAR Detector Dataset and Cuts • System: Au+Au collision • Energy : sNN = 200 GeV • Event sample : ~60 M events • Year: 2007 Full azimuthal acceptance! TPC : -1.0 < η < 1.0 FTPC : -4.0 < η < -2.5 (east) 2.5 < η < 4.0 (west) • Systematic uncertainty (non-flow effect): • FTPC event plane method – large ηgap • Lee-Yang Zero method – multi-particle correlation

  5. Elliptic Flow v2 W. Liu and R. J. Fries, arXiv: 0805.3721, (2008). STAR preliminary • Jet conversion prediction: • (>5 GeV) • v2(kaon) < v2(pion) • v2(proton)-v2(lambda) • is much smaller than • v2(pion)-v2(kaon) • Need more statistic to conclude. • FTPC event plane is used. • Mass ordering at low pT.

  6. Number of Constituent Quark Scaling STAR preliminary • Pion v2/nq starts to deviate from NCQ scaling at 1 GeV for (mT - m)/nq. • A larger pion v2/nq than other v2/nq at large pT /nq.

  7. Breaking Pattern STAR preliminary Curves : V.Greco and C.M.Ko, PRL 70 024901 (2004); B. Muller, R.J.Fries and S.A.Bass, PLB 618 77 (2005); C.B.Chiu, R.C. Hwa and C. B. Yang, PRC 78 044903 (2008); R.J. Fries, B.Muller, C. Nonaka and S.A. Bass, PRC 68 044902 (2003). • In the range of 0.5 < pT/nq < 1.5 (GeV/c), the deviation between pions and baryons is ~20%, while models with realistic effects can tolerate up to only 5%.

  8. Summary • At pT /nq > 1 GeV, datashow clear discrepancies with naive NCQ scaling: • Pions deviate from NCQ scaling by 20% (while models can tolerate only 5%). • Fragmentationmay kick in and be more dominant. • Outlook • STAR Run 10: full TOF coverage • Measure v2 for charged pion / kaon / (anti)proton at intermediate pT • --- Test jet conversion prediction. • --- Improve the signal/background ratio of reconstructed particles.

  9. BACK UP

  10. Breaking Pattern (I) STAR preliminary Curves : V.Greco and C.M.Ko, PRL 70 024901 (2004); B. Muller, R.J.Fries and S.A.Bass, PLB 618 77 (2005) • The large deviation at low pT in plot made with pT/nq is due to mass splitting, which can be reduced by plotting with (mT-m)/nq • Models with realistic effects can well describe the difference between kaons and baryons

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