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Levente Molnar Purdue University for the Collaboration

Jet-like correlations between forward - and mid - rapidity in p+p, d+Au, and Au+Au collisions from STAR. Levente Molnar Purdue University for the Collaboration. Forward and mid- rapidity correlations. g. g. q. q. FTPC associated particles: Forward TPCs (2.7 < |η| < 3.9)

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Levente Molnar Purdue University for the Collaboration

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  1. Jet-like correlations between forward- and mid-rapidityin p+p, d+Au, and Au+Au collisionsfrom STAR Levente Molnar Purdue University for the Collaboration

  2. Forward and mid-rapidity correlations g g q q • FTPC associated particles: Forward TPCs (2.7 < |η| < 3.9) gluon (xg ~ 0.05)–quark (large xq) scattering ∆φ • Forward TPCs, utilize: • 2.4 < |η| < 4 • (~ 2 – 8o in ) • 2 azimuth • Main TPC, utilize: |η| < 1 • and 2 azimuth FTPC E. FTPC W. • Trigger particle: • Main TPC (|η| < 1) • Measurements so far: • Main TPC associated particle (|η| < 1) • gluon – gluon scattering, xg ~ 0.05 Levente Molnar for STAR Collaboration

  3. Physics motivation I. What we have seen so far at RHIC: • Significant modification of gluon jets at midrapidity wrt. p+p. (J. Adams et. al (STAR) Phys. Rev. Lett. 95 (2005) 152301) • Near side long-range ∆η correlation in central Au+Au collisions. (J. Adams et al, Phys. Rev. C73: 064907) See STAR talks by: Jörn Putschke: 15 Nov. Parallel 1.3 Jana Bielcikova: 19 Nov. Parallel 3.1 STAR Preliminary STAR Preliminary Levente Molnar for STAR Collaboration

  4. Physics motivation II. Open questions: • Jet correlation at high η or only recombination? (R.Hwa, C.B. Yang, nucl-th/0605037) • If correlation exist: • Similar or different relative to midrapidity? • pQCD energy loss: gluon ~ 9/4 × quark • CGC at forward rapidities? STAR, Phys. Rev. Lett. 97 (2006) 152302 Possible hint for CGC? Levente Molnar for STAR Collaboration

  5. p+p and d+Au collisions at 200 GeV |ηtrig|<1, 2.7<|ηassoc|<3.9 3<pTtrig<10 GeV/c, 0.2<pTassoc< 2 GeV/c • Jet correlation at forward • rapidities in p+p and d+Au: • No near side correlation • Away side shapes are • similar • Hierarchy in the away • side yields: • Au > p(p) > d 1/Ntrig dN/d(Δ) STAR Preliminary D Background normalized to near-side |∆φ|<1. Levente Molnar for STAR Collaboration

  6. Physics of the away side < xg~0.05 large xq large xq xg~0.05 • Similar away side shapes, but yield Au/d≈ 2 • Reduction of small-x gluons in Au: • Gluons are in the anti-shadowing • region (EKS98): • (Eskola, Kolhinen, Vogt, • Nucl.Phys.A696:729-746,2001) • cannot explain data • EMC (0.3 <x< 0.8) effect: • (EMC: PLB 123,275, BCDMS: • PLB 189,483, E139 PRD 49,4348) • cannot explain data Levente Molnar for STAR Collaboration

  7. Physics of the away side Guo-Liang Ma, et al. HP 2006 • Similar away side shapes, • but yield Au/d≈ 2 • CGC: gluon suppression in heavy • nuclei: • consistent with observation • quantitative calculations are needed • (Kharzeev, Levin, McLerran, Nucl.Phys.A748:627-640,2005) STAR Preliminary • Energy degrading from deuteron? • Qualitative description in (default) AMPT G.L. Ma, et al. HP 2006 • Hadronic rescattering (Au side – stronger)? • Correlation magnitude • Further study is needed! Levente Molnar for STAR Collaboration

  8. Summary of p+p and d+Au results • Away side jet correlations are observed at forward rapidities (2.7 <| η | < 3.9) in p+p, d+Au at 200 GeV. • No near side correlation observed • Away side shapes are similar in p+p and d+Au • Away side yield is different for outgoing d and Au side: • Au > p > d • Au/d≈ 2 → gluon suppression in Au • Further studies are needed: CGC, HIJING, AMPT, … Levente Molnar for STAR Collaboration

  9. Au+Au minimum bias at 200 GeV • Normalization and systematics: • Normalization fixed at |∆φ±1|<0.2 • Background normalization • uncertainty in dashed lines. • Major systematic uncertainties • from v2: • MTPC v2: between v2{RP} and v2{4} • FTPC v2{2} is used • uncertainty assumed to be • the as same as MTPC • conservative estimate. |ηtrig|<1, 2.7<|ηassoc|<3.9 3<pTtrig<10 GeV/c, 0.2<pTassoc< 2 GeV/c Minimum Bias 1/Ntrig dN/d(Df) raw signal STAR Preliminary Near-side consistent with zero within systematics. Broad away-side correlation. bkgd subtracted Df Levente Molnar for STAR Collaboration

  10. Au+Au 200 GeV centrality variation |ηtrig|<1, 2.7<|ηassoc|<3.9 3<pTtrig<10 GeV/c, 0.2<pTassoc< 2 GeV/c • Nearside consistent • with zero within • systematic errors • Away side broadens • from p+p / d+Au to • Au+Au collisions STAR Preliminary Normalization fixed at | ∆Φ±1|<0.2. Levente Molnar for STAR Collaboration

  11. Near side in 0-10% Au+Au at 200 GeV STAR Preliminary • Near side: • Hint of finite near side correlation? • Long range ∆η correlation? 0.2<pTassoc< 2 GeV/c 3<pTtrig<10 GeV/c STAR Preliminary STAR Preliminary 0.2<pTassoc< 1.0 GeV/c 1.0 GeV/c <pTassoc Levente Molnar for STAR Collaboration

  12. Away side peak in Au+Au at 200 GeV D D Df Centrality 1/Ntrig dN/d(Df) STAR Preliminary • Away side: • Broadens from peripheral to central collisions (as at mid- rapidity)  Systematic errors from v2. Levente Molnar for STAR Collaboration

  13. Compare FTPC correlation to MTPC dAu MB • Away side in dAu: • similar between forward • and mid-rapidity Trigger: 3<pTtrig<4 GeV/c, Associated: FTPC: 0.2<pTassoc< 2 GeV/c, TPC: 0.2<pTassoc< 3 GeV/c pp MB • Away side in pp:broader at • forward than mid-rapidity • Similar observation by DØ • (DØ Collab., Phys.Rev.Lett.77:595-600,1996 ) Levente Molnar for STAR Collaboration

  14. Compare FTPC correlation to MTPC AuAu 0-10% AuAu 0-5% AuAu 60-80% • Away-side correlations are very similar! • Energy loss picture is the same for mid- and forward rapidities? Trigger: 3<pTtrig<4 GeV/c, Associated: FTPC: 0.2<pTassoc< 2 GeV/c, TPC: 0.2<pTassoc< 3 GeV/c Levente Molnar for STAR Collaboration

  15. Summary Jet correlations are observed at forward rapidities (2.7 <| η | < 3.9) in p+p, d+Au and Au+Au collisions. Near side: • No correlation in pp and dAu • Top 10% Au+Au at pTassoc > 1 GeV/c: Hint for near side ∆η long range correlation? (syst. uncertainties large) Away side: • dAu: Au-side /d-side≈ 2 → gluon suppression in Au? • Au+Au: broadens with centrality • Correlation shapes similar between forward and mid-rapidity Energy loss picture is similar at forward and mid-rapidity? Quantitative model calculations are needed! Levente Molnar for STAR Collaboration

  16. Extra slides Levente Molnar for STAR Collaboration

  17. FTPC v2 correction Centrality: 70-20% FTPC v2: STAR, Phys. Rev. C 72, 014904 (2005). • Different methods give similar v2 results for the FTPC data. • Parameterize v2 in pT and h. • Centrality dependence measured by STAR (preliminary). Levente Molnar for STAR Collaboration

  18. PDF from CTEQ5 H. L. Lai et al., (CTEQ Collab.) Eur.Phys.J.C12:375-392,2000 Valence quark dominance at large x Levente Molnar for STAR Collaboration

  19. The Azimuthal decorrelation of jets widely separated in rapidity. (D0 Collab., Phys.Rev.Lett.77:595-600,1996 ) Levente Molnar for STAR Collaboration

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