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Recent Results from BRAHMS

Mostly Strangeness. Recent Results from BRAHMS. J.H. Lee Physics Department Brookhaven National Laboratory For the Collaboration March 27 2006. Short Introduction BRAHMS in “1 page” What have we learned so far? Selected Published + Preliminary Results Outlook/Summary.

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Recent Results from BRAHMS

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  1. Mostly Strangeness Recent Results from BRAHMS J.H. Lee Physics Department Brookhaven National Laboratory For the Collaboration March 27 2006 J.H. Lee (BNL)

  2. Short Introduction • BRAHMS in “1 page” • What have we learned so far? Selected Published + Preliminary Results • Outlook/Summary J.H. Lee (BNL)

  3. Forward Physics in R.H.I. Collisions: Mapping Space-time Evolution • Formation of Hot Matter, QGP? • -Identifying and Characterizing the Hot Matter • - How does the system extend/develop? Transverse and longitudinal dynamics • - Strong constraints for theoretical modeling/interpretation • Initial Conditions/Partonic Dynamics: High-pT vs y • Collective Hydro-dynamics: Flow (radial and elliptic) vs y: “Viscometer” • Thermodynamic and freeze-out properties: Temperatures, Ratios, HBT vs y • Baryon Transport: Net-baryon vs y • Bulk Properties: multiplicity, dN/dy J.H. Lee (BNL)

  4. FS PID using RICH Multiple settings Braod RAnge Hadron Magnetic Spectrometers • Designed to study nuclear reactions in broad kinematic range (y-pT) • 2 movable spectrometers with small solid angle measuring charged identified hardrons precisely • Centrality detectors (Si+Scintillator Tiles) to characterize events • 53 people from 12 institutions from 5 countries J.H. Lee (BNL)

  5. Baryon Transport: How much energy available from the collision? Net-proton in p+p PRL 93 102301 (2004) Au+Au 200 GeV 0-5% Central H. Yang, Symposium • AGS->RHIC : Stopping -> Transparency • Rapidity Loss <dy>: 2±0.4: not linearly increase with ybeam • Energy loss <dE> per nucleon: 73±6 GeV • Available energy for excitation: ~3/4 of total energy J.H. Lee (BNL)

  6. Rapidity Dependent Kaon Balence: “Net”-kaon (K+-K-) • longitudinal net-kaon evolution similar as net-proton • in |y|< 3 at RHIC (AuAu @ 200 GeV) • strong “association”: net-kaon / net-lambda /net-proton? J.H. Lee (BNL)

  7. Baryon/meson (p/p+,pbar/p-) at √s = 200 GeV • proton dominates at y~3: R(p/p+)y~3 ~ 2* R(p/p+) y~0 • for central AuAu, CuCu and pp: baryon transport • pbar at y~3: R(pbar/p-)y~3 ~ 0.5* R(p/p-) y~0 • Scale with <Npart>, independent of system at h=0 and 3.2 • Decrease with rapidity and increase with <Npart> and pT • (flow , medium effect) • Ratio independent of centrality J.H. Lee (BNL)

  8. Limiting Fragmentation: Longitudinal Scaling PRL 94 (2005) PRL 88 (2002) d+Au sNN=200GeV sNN=19.4GeV Au+Au sNN=200GeV • Particle production independent of beam energy • near beam rapidity: Limiting fragmentation behavior • “Crucial Observation” (L.M.) for universal QCD J.H. Lee (BNL)

  9. Limiting Fragmentation of pion and Kaon BRAHMS/RHIC + SPS + AGS p- J.H. Lee (BNL)

  10. “Extended” Longitudinal Scaling for <mT> for K- BRAHMS Preliminary BRAHMS Preliminary PHOBOS PRL 94 (2005) • K- <mT> decreases with rapidity • Longitudinal Scaling in all available rapidity ranges • <pt> driving Hydro J.H. Lee (BNL)

  11. Energy dependent K/p for central AuAu 200GeV 63 GeV • K/p: No surprises at 63 GeV • 200 and 63 GeV: Similar rapidity dependence J.H. Lee (BNL)

  12. K/p vs pT at h~3.2 at √s = 200 GeV • K/p increase with system size • K/p increase with pT (~ < 2GeV/c) at forward J.H. Lee (BNL)

  13. Flowing at Forward v2 for pion • Understanding missing low-pt fraction is important for integrated v2 from FS • Kaon and proton v2 will come: Statistically Challenging • v2(y~0) ~ v2(y~3) for 0.5<pT<2 GeV/c J.H. Lee (BNL)

  14. BRAHMS NA49 AGS Rapidity Dependent High-pT Measurement y~0 • At the RHIC energies, hardscattering processes at high-pT become important • Partonsare expected to looseenergyin the dense matter • Different rapidities provide different densities of the medium: Sensitive to the dynamics • “Dialing” initial condition channel • Largest medium effect at mid-rapidity (“Scale” to multiplicity)? • Rapidity dependent high-pTsuppression factors: provide information on dynamical medium effect at fixed time high-y J.H. Lee (BNL)

  15. pp at forward : more then reference spectra BRAHMS Preliminary pT (GeV/c) • NLO pQCD describes data at forward rapidity at 200 GeV • K- are described best by KKP (Kniehl-Kramer-Potter) than Kretzer • (NLO pQCD Calculations done by W. Vogelsang) J.H. Lee (BNL)

  16. Energy and System Dependent Nuclear Modification Factors at h~0 and 1 • R AuAu (200 GeV) < RAuAu(63 GeV) < RCuCu(63 GeV) for charged hadrons • Pp at 63 GeV is ISR Data (NPB100), RHIC-Run6 will provide better reference J.H. Lee (BNL)

  17. Nuclear Modification Factors (Rcp, RAuAu) for p,K,p at y~3.1 • Suppression for pions and Kaons: RAuAu: p<K<p • RAuAu ≠ Rcp (<Ncoll>,<Npart> for 40-60% ~ 70,56) J.H. Lee (BNL)

  18. RAuAu(Y=0) ~ RAuAu(y~3) for 0-10% Central at √s = 200 GeV • R AuAu (Y=0) ~ RAuAu(y~3) for pions and protons: Accidental? • Rapidity dependent interplay of Medium effect + Hydro + baryon transport J.H. Lee (BNL)

  19. RdAu Update: Identified Particle RdAu at y~3 + blue - red BRAHMS Preliminary • RdAu of identified particle consistent with published h- results • dAu(p-)/dAu(p+): Valance quark isospin dominates in pp? J.H. Lee (BNL)

  20. System, Energy dependent - Strangeness production - Freeze-out chemistry Turning off the medium effect in Rapidity, Energy, Species? - Rcp, RAA at higher-rapidity h~3.5 for Kaon Universal (QCD) property at forward? Saturation – Fragmentation - “Complete” rapidity and pT-dependent kaon measurement for pp, dA, AA Longitudinal (partonic) dynamics of strangeness: - rapidity, pt, centrality, reaction-plane dependent kaon yield,ratios - v2 vs y for kaons pQCD vs forward kaons in pp Strangeness spin physics also: - Transverse single spin Asymmetries for K at “high”-xF Strangeness Physics from 5 years of BRAHMS running J.H. Lee (BNL)

  21. Summary Strong transverse/elliptic flow in y<3 High energy density >> nuclear density Limiting fragmentation - y  2 - 25 TeV left for particle production (local) Chemical equilibration Non-hadronic energy loss through the medium in |y|<3: Onset of gluon saturation? J.H. Lee (BNL)

  22. BRAHMS White Paper J.H. Lee (BNL)

  23. The BRAHMS Collaboration I.Arsene7, I.G. Bearden6, D. Beavis1, S. Bekele6 , C. Besliu9, B. Budick5, H. Bøggild6 , C. Chasman1, C. H. Christensen6, P. Christiansen6, R. Clarke9, R.Debbe1, J. J. Gaardhøje6, K. Hagel7, H. Ito10, A. Jipa9, J. I. Jordre9, F. Jundt2, E.B. Johnson10, C.E.Jørgensen6, R. Karabowicz3, E. J. Kim4, T.M.Larsen11, J. H. Lee1, Y. K. Lee4, S.Lindal11, G. Løvhøjden2, Z. Majka3, M. Murray10, J. Natowitz7, B.S.Nielsen6, D. Ouerdane6, R.Planeta3, F. Rami2, C. Ristea6, O. Ristea9, D. Röhrich8, B. H. Samset11, D. Sandberg6, S. J. Sanders10, R.A.Sheetz1, P. Staszel3, T.S. Tveter11, F.Videbæk1, R. Wada7, H. Yang6, Z. Yin8,and I. S. Zgura9 1Brookhaven National Laboratory, USA, 2IReS and Université Louis Pasteur, Strasbourg, France 3Jagiellonian University, Cracow, Poland, 4Johns Hopkins University, Baltimore, USA, 5New York University, USA 6Niels Bohr Institute, University of Copenhagen, Denmark 7Texas A&M University, College Station. USA, 8University of Bergen, Norway 9University of Bucharest, Romania,10University of Kansas, Lawrence,USA 11 University of Oslo Norway J.H. Lee (BNL)

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