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F, Ks,  , and X production at 200 GeV d+Au collisions from STAR

F, Ks,  , and X production at 200 GeV d+Au collisions from STAR. Xiangzhou Cai, Yugang Ma, Hai Jiang, Jingguo Ma for the STAR Collaboration Shanghai INstitute of Applied Physics University of California, Los Angeles Lawrence Berkeley National Laboratory. Outline

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F, Ks,  , and X production at 200 GeV d+Au collisions from STAR

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  1. F,Ks, , and Xproduction at 200 GeVd+Au collisions from STAR Xiangzhou Cai, Yugang Ma, Hai Jiang, Jingguo Ma for the STAR Collaboration Shanghai INstitute of Applied Physics University of California, Los Angeles Lawrence Berkeley National Laboratory Outline • Motivations for measuring Ks, , f andX • Analysis details of dAu analysis (Ks, f, L, X, K*, Kink-K) • Spectra, fit function and comparison • Rcp, RdAu, particle dependence of Cronin effect • Summary PAs: Lee Barnby, Xiangzhou Cai, Magali Estienne, Hai Jiang, Camelia Mironov, Lijuan Ruan, Frank Simon, Nu Xu, Haibin Zhang

  2. Motivation & Introduction 1) Particle dependence of RAA/Rcp and v2 from Au+Au collisions is observed. How about RAA/Rcp in dAu? particle type or mass dependence? (Rcp for Ks, , and ). 2) The Cronin effect has been considered as due to initial parton scattering. Should the Cronin effect be influenced by the final state particle formation dynamics? 3) Transverse momentum production: <pT> versus multiplicity • mf~1019 MeV/c2 ; mL~1116 MeV/c2; mKs~498 MeV/c2

  3. Data Sets and Event Cuts dAu 200GeV STAR MuDst P03a: MinBias and Combined Event Trigger ID: 2001 or 2003 Primary Vertex Position: -50cm<z<50cm Track nFitPts: > 15 |eta|: < 1.0 Pt range: 0.1GeV < Pttrack < 4.0GeV

  4. Centrality definition of dAu Multiplicity FTPC East in d+Au collisions 40-100% STAR Preliminary 20-40% 0-20% Three Multiplicity Bins are defined by the Nch per event in FTPC East After cut: ~ 10 Million events 1)dE/dx identify stable charged particles in a certain momentum range. 2)Unstable particles identified by decay topology or event mixing method.

  5. - - X-  p+ Primary Vertex Decay point Decay point Event Selection: |VertexZ| < 50cm, with Primary vertex found, good run After cuts, # of Events ~ 10M Decay mode: Ks =>p + +p - (68.6%) X-  L +p - (99.9%) p+ + p -(63.9%) • =>K + +K - (49.1%) K* =>K +p (100%) Ks, L, X are reconstructed using topology cuts, like decay length, dca-v0-primV Daughter tracks are NOT identified when pt>1.1 GeV/c, but v0 can be identified at much higher pT. f ,K*: event mixing

  6. Ks and  reconstruction & Topology cuts - - p+ + Track 1 Decay point Decay point Track 2 Ks  Primary Vertex Primary Vertex DcaV0 • Ks and  are V0 particles: decay length: Ks = 2.69 cm  = 7.89 cm • In TPC, neutral Ks and  are reconstructed from charged particles: p, K and p (See above sketch). Topology Cuts (See the right sketch) • |vertexZ|<50cm • DcaV0: between two daughter tracks < 0.7cm • DcaImpact (distance between V0 and Primary vertex) < 0.75 cm () , and < 0.6cm (Ks) • Decay length (distance between primary vertex and V0 decay point) > 2 cm (Ks and ) Decay len DcaImpact

  7. Event Mixing Method   K+ K- Branching Ratio = 0.49 Both K+ and K- come from the same event Signal K+ and K- come from different event Background Mixed event is supposed to contain everything of significance to the correlation analysis except the correlation itself. Calculate the invariant mass of every possible K+K- pairs and accumulate the signal to reconstruct f in each (y, pt) bin.

  8. |y|<1 0.4 <pt< 6.0 |y|<0.5 0.4 <pt< 1.3 f |y|<1 0.4 <pt< 6.0 Invariant mass plots Without background subtraction Ks, L, X : topology cuts; f: event mixing The quality of signals are pretty good. STAR Preliminary |y|<1 0.6 <pt< 5.0

  9. Acceptance and Efficiency Embedding method: • Generate tracks with certain pT and rapidity distribution. (SimTrack) • Generate Monte-Carlo tracks in STAR geometry (MCTrack) Acceptance = • TPC response simulator generates hits • Monte-Carlo hits are embedded in the real data • Reconstruct the “embedded events” using the same chain as real data production (RecTrack) • Tracking efficiency extraction Efficiency = • Total correction factor Correction = Acceptance * Efficiency*Branching Ratio 4

  10. EfficiencyCorrection of f, Ks and  STAR Preliminary • The efficiency increases with Pt and becomes flat • Weak multiplicity dependence.The difference of efficiency correction between different centrality bins is small than the error bars.

  11. Comparison of different Fits • Spectra for MinBias Phi production in dAu • exp fit covering low pt end and power-law fit covering high pt region. • Double exponential fit can reproduce the experimental data better than other two funtions. STAR Preliminary Double exponential fit: T1: ~300MeV; T2: 1.0~1.5GeV;

  12.  production in AuAu and pp • 200 GeV f meson production from both AuAu and pp collisions are analysed by Jingguo Ma. • 200 GeV f meson production from dAu is necessaryfor further understanding: • f production mechanism • particle dependence of nuclear modification factor

  13. f double exp fit Spectra and fits STAR Preliminary pT: 0.4 – 6 GeV/c. With efficiency correction (including vertex efficiency). Statistical errors only. cross point: pT~(2~4)GeV/c2. Recombination model may fit spectra well … TT(low pt)+TS(middle pt)+SS(high pt)

  14. X spectra and feed-down contribution to L STAR Preliminary X- + Xbar minbias : dN/dy = 0.0268 +- 0.0007 L + Lbar minbias (inclusive) : dN/dy = 0.339 +- 0.007 If assuming X0~ X- and  ~ 10% X- , Then feed-down from X,  ~ 0.0268*2.1= ~ 0.056 ( 17% ) Consistent with the feed-down in AuAu ~ 15% (Hui, Magali’s SQM paper)

  15. Spectra comparison Different measurements are consistent within STAR! From Camelia

  16. dAu Minbias dN/dy vs. <Nch> STAR Preliminary f, Ks, L, X increase with <Nch> in dAu and AuAu collisions.

  17. dAu Minbias <pt> vs. <Nch> STAR Preliminary <pt>: X shows no dependence of <Nch> within error bar, but f and L are different.

  18. Rcp definition We select three data samples: “Central”:centrality 0-20% “Semi-central”: centrality 20-40% “Peripheral”:centrality 40-100% Then we calculate the ratios Central/Peripheral as function of pT at different rapidities. Rcp = (d2N/dpTd) cent/ (d2N/dpTd) peri Many corrections and systematics cancel out.

  19. TT TS SS TTT TTS+TSS SSS Rcp of f, Ks, L, X dAu 200 GeV AuAu 200 GeV STAR:  and K* behave like mesons, despite of the large mass: ReComb prediction • Mesons(Ks, K, f) have the same Rcp for dAu and AuAu collisions • Baryons (L, X) have the same Rcp too, but higher than mesons. Particle production at intermediate pT region is dividing by the particle’s type, not the mass. Recombination/Coalescence model works! Theycan explain the difference of Rcp between mesons and baryons for both dAu and AuAu. (Z.M.Ko et al., R.C.Hwa et al….)

  20. Nuclear modification factor RdAu The behavior of the many-body systems we study (A-A or d-A) can be “calibrated” with a “simple system” like p-p . Borrowing from “Cronin effect” studies, we compare particle production in d-A to the scaled production in p-p: RdAu = (d2NdAu/dpTd) / (Ncoll d2Npp/dpTd ) With Ncoll being the estimated number of binary collisions as d “goes through” the Au nuclei.

  21. RdAu • RdAu of  is closer to that of p and k than that of p • Particle production at intermediate pT region is sorted by the particle’s type, not the mass

  22. Summary • Measure the productions and <pt> for various particles (Ks, f, L, X) in dAu collisions • Double exponential function can fit thef,Ks, LandX spectra better than others, dN/dy scale linearly with the number of charged particles • RdAu and Rcp in dAu are grouped into mesons and baryonsit indicates that the particle production is dividing by particle type rather than particle mass as predicted by the parton recombination/quark coalescence model. • Rcp plots show no suppression indicating that the suppression in Au+Au maybe arises from additional effects

  23. The End Thank you!

  24. From Fragmentation to Recombination • With more partons around: multiple parton fragmentation (higher twist) • If phase space is filled with partons, recombine/coalesce them into hadrons. • Use just the lowest Fock state, i.e. valence quarks: qqqB qqM

  25. Recombination model of Hwa and Yang p++p- in d+Au P in d+Au Nucl-th/0403001, Nucl-th/0404066

  26. Spectra and fits Kink from Camelia TOF_K from Lijuan K* from Lijuan, Haibin Neutral K* in mt exp fit Charge K* in power-law fit Ks yield is lower than TOF_K and kink at the low pt, but the shapes are same.

  27. v2 Scaling P. Sorensen Perfect scaling for all measured hadrons, some deviation for pions (from  decays) P. Sorensen Baryons are pushed further in PT

  28. ~1.4 ~1.5 ~2.5 s =38.8GeV s =27.4GeV Comparison with pA collision Rw/Be at pA collisions P.B Straub,PRL 68, 452(1992) W: tungsten Be: beryllium Rw/Be : Mesons (2 quarks): Kaon and p ~ 1.5; Baryons (3 quarks): proton ~ 2.5 Particle-type dependence also!

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