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Recent Results from STAR Markus D. Oldenburg 14 th Topical Conference on Hadron Collider Physics Munich, Germany For the STAR Collaboration.

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Presentation on theme: "Recent Results from STAR Markus D. Oldenburg 14 th Topical Conference on Hadron Collider Physics Munich, Germany For the STAR Collaboration."— Presentation transcript:

1 Recent Results from STAR Markus D. Oldenburg 14 th Topical Conference on Hadron Collider Physics Munich, Germany For the STAR Collaboration

2 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics2 Outline RHIC STAR Analyses –Anisotropic Flow –Jets at RHIC –Ultra-Peripheral Collisions Summary Outlook

3 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics3 The R elativistic H eavy I on C ollider Two independent accelerator rings 3.83 km in circumference Accelerates everything from p to Au Running conditions: Au-Au bunches per ring (tested up to 110) storage energy Storage energy: 100 GeV/A Peak luminosity: cm -2 s -1 Running conditions: p p bunches per ring p /bunch Energy/beam: 100 GeV Peak luminosity: cm -2 s -1 Beam polarization ~ 25% ( AGS) Long Island STAR

4 The STAR experiment at RHIC STAR uses the worlds largest Time Projection Chamber

5 One of the first Au on Au Events at CM Energy of 200 GeV ASTAR

6 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics6 Anisotropic Flow Look at peripheral collisions Overlap region is not symmetric in coordinate space Almond shaped overlap region –Easier for particles to emerge in the direction of x-z plane –Larger area shines to the side x y z pxpx pypy y x Spatial anisotropy Momemtum anisotropy –Interactions among constituents generate a pressure which transforms the initial spatial anisotropy into the observed momentum anisotropy Perform a Fourier decomposition of the momentum space particle distributions in the x-y plane –v n is the n-th harmonic Fourier coefficient of the distribution of particles with repsect to the reaction plane v 1 : directed flow v 2 : elliptic flow

7 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics7 PRL 86, (2001) 402 more central v 2 vs. Centrality (130 GeV) v 2 is large –6% in peripheral collisions –Smaller for central collisions Hydro calculations are in reasonable agreement with the data –In contrast to lower collision energies where hydro over- predicts anisotropic flow Anisotropic flow is developed by rescattering –Data suggests early time history –Quenched at later times Anisotropic transverse flow is large at RHIC Hydro predictions

8 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics8 v 2 vs. p t and Particle Mass (130 GeV) The mass dependence is reproduced by hydrodynamic models –Hydro assumes local thermal equilibrium –At early times –Followed by hydrodynamic expansion PRL 86, 402 (2001) & nucl-ex/ Hydro does a surprisingly good job D. Teaney et al., QM2001 Proc. P. Huovinen et al., nucl-th/

9 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics9 v 2 for High p t Particles (130 GeV) pQCD inelastic energy loss + parameterized hydro component (M. Gyulassy, I. Vitev and X.N. Wang, PRL 86 (2001) 2537) –value of v 2 at high p t sensitive to the initial gluon density –saturation and decrease of v 2 as a function of p t at higher p t data starts to deviate from hydrodynamics at p t > 2 GeV/c Adler et al., nucl-ex/ Data is in qualitative agreement with jet-quenching scenario

10 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics10 Centrality dependence of v 2 (p t ) v 2 is saturated at high p t and it does not come back down as rapidly as expected What does v 2 do at very high p t ? 200 GeV (preliminary) 130 GeV peripheral central

11 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics11 v 2 up to 12 GeV/c v 2 seems to remain saturated

12 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics12 Hard Probes in Heavy-Ion Collisions New opportunity using Heavy Ions at RHIC Hard Parton Scattering – s NN = 200 GeV at RHIC –17 GeV at CERN SPS Jets and mini-jets –30-50 % of particle production –High p t leading particles –Azimuthal correlations Extend into perturbative regime –Calculations reliable (?) Scattered partons propagate through matter & radiate energy (dE/dx ~ x) in colored medium –Interaction of parton with partonic matter –Suppression of high p t particles: jet quenching –Suppression of angular correlations hadrons q q leading particle leading particle schematic view of jet production QGP Vacuum

13 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics13 Jets in Hadronic Collisions p+p jet+jet Au+Au ???

14 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics14 Identifying jets on a statistical basis in Au-Au Given a trigger particle with p t > p t (trigger), associate particles with p t > p t (associated) Au+Au –flow p+p and Au+Au collisions: –dijets –momentum conservation –jets –resonances STAR Preliminary 200 GeV/c, 0-5% most central 4 < p t (trig) < 6 GeV/c, 2 < p t (assoc.) < p t (trig) Small All

15 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics15 Peripheral Au+Au data vs. pp+flow Ansatz: A high p t triggered Au+Au event is a superposition of a high p t triggered p+p event plus anisotropic transverse flow v 2 from reaction plane analysis A is fit in non- jet region (0.75 < | | < 2.24)

16 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics16 Central Au+Au data vs. pp+flow

17 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics17 Jets at RHIC The backward going jet is missing in central Au-Au collisions when compared to p-p data + flow Other features of the data –High p t charged hadrons dominated by jet fragments Relative charge Azimuthal correlation width Evolution of jet cone azimuthal correlation strength with centrality ? Surface emission? Suppression of back-to-back correlations in central Au+Au collisions Other explanations for the disappearance of back-to-back correlations in central Au-Au? –Investigate nuclear k T effects Experiment: p+Au or d+Au Theory: Add realistic nuclear k T to the models

18 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics18 Ultra-Peripheral Collisions b > 2R A; –no hadronic interactions – ~ fermi at RHIC Ions are sources of fields –Fields couple coherently to ions p t < h/R A, ~30 MeV/c for heavy ions p || < h/R A ~ 3 GeV/c at RHIC Photonuclear (Photon-Pomeron) Interactions A,,, J/,… A –Vector Meson Dominance A qqA (elastic scattering) VA – ~ 350 mb at 130 GeV/nucleon 5% of AuAu (had.) Electromagnetic particle production leptons, mesons –Strong Field (nonperturbative?) QED Au Coupling ~ nuclear form factor, P, or meson -

19 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics19 Exclusive 0 p t <0.15 GeV 0 p t Signal region: p t <0.15 GeV 200GeV Preliminary Trigger on low multiplicity events veto on cosmic rays 2 track vertex w/ charge 0 –reject (coplanar) cosmic rays peak for p t < 150 MeV/c and give background shape –scaled up by )

20 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics20 Minimum Bias Data 800,000 triggers neutron signals in ZDCs Nuclear excitation tags small b interactions –excitation and 0 are independent Analysis same as in peripheral Preliminary 200 GeV Signal region: p t <0.15 GeV d /dM mb/GeV 200 GeV Preliminary 0 p t - ) Normalized to 7.2 b hadronic cross section Systematic uncertainties: luminosity, overlapping events, vertex & tracking simulations, single neutron selection, etc.

21 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics21 Summary of Analyses shown: Anisotropic Flow Jets at RHIC Ultra-Peripheral Collisions not shown: Particle yields / ratios / spectra Interferometry (HBT) Fluctuations Gluon density saturation Spin physics program Results: Large anisotropic flow, consistent with hydrodynamical picture Saturation of v 2 at high p t Jet quenching? Suppression of back-to-back jets Surface emission? 0 cross sections measured in ultra-peripheral Au-Au collisions, good agreement to theory

22 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics22 RHIC Performance Goals for weeks of d-Au (including cooldown) 8 weeks of p p (We wont have Si-Si nor Au-Au next year.) More interesting physics to come...

23 Markus D. Oldenburg14 th Topical Conference on Hadron Collider Physics23 STAR Institutions U.S. Labs: Argonne, Brookhaven, and Lawrence Berkeley National Labs U.S. Universities: UC Berkeley, UC Davis, UCLA, Carnegie Mellon, Creighton, Indiana, Kent State, Michigan State, CCNY, Ohio State, Penn State, Purdue, Rice, UT Austin, Texas A&M, Valparaiso, Washington, Wayne State, Yale Brazil: Universidade de Sao Paolo China: IPP - Wuhan, IMP - Lanzhou USTC, SINR, Tsinghua University, IHEP - Beijing England: University of Birmingham France: IReS - Strasbourg SUBATECH - Nantes Germany: Max Planck Institute - Munich University of Frankfurt India: Institute of Physics - Bhubaneswar IIT - Mumbai, VECC - Calcutta Jammu University, Panjab University University of Rajasthan The Netherlands: NIKHEF Poland: Warsaw University of Technology Russia: MEPHI - Moscow, IHEP - Protvino LPP & LHE JINR - Dubna


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