Up to 10 GeV injector

1. Up to 10 GeV injector 5-10 GeV static e-ring PHOBOS BRAHMS & PP2PP RHIC STAR PHENIX Pol. Proton Source LINAC BOOSTER AGS Exploring the Spin structure and dynamics of the Proton in high energy polarized pp collisionsat RHIC Bernd Surrow

2. STAR RHIC SPIN members Proton Spin Faculty: R. Milner and B. Surrow Postdocs: J. Kiryluk and M. Miller Graduate student: W. Jang Gluon Spin Orbital Motion Quark Spin • Polarized proton collider RHIC Outline • The STAR detector • First results in polarized pp collisions • Future MIT research interests • Summary and Outlook • Introduction Bernd Surrow

3. Introduction Orbital Motion Quark Spin Proton Spin Gluon Spin • RHIC Spin program (e.g. ΔG) • Fundamental question: How is the proton spin made up? • At present: G is only poorly constrained from scaling violations in fixed target DIS experiments B. Adeva et al., SMC Collaboration, Phys. Rev. D58 (1998) 112002. • Need: New generation of experiments to explore the spin structure of the proton: polarized proton collisions at RHIC which allows to access directly G in polarized pp collisions!  SMC result: Fraction of proton spin carried by quarks is small: RHIC spin program:  Where is the spin of the proton then?  SMC QCD-fit: • Unique multi-year program which has just started…! • Explore various aspects of the spin structure and dynamics of the proton in a new domain: • Spin structure of the proton (gluon polarization, flavor decomposition, transversity) • Spin dependence of fundamental interactions • Spin dependence of fragmentation • Spin dependence in elastic polarized pp collisions Bernd Surrow

4. Introduction • Asymmetries  Measurement of asymmetries (A): Principle approach to study spin effects  Ultimately at RHIC, any combination of beam polarization (longitudinal (+/-) /transverse (/)) is possible, which allows to access different parts of the proton spin structure • Double longitudinal-spin asymmetry: • Double transverse-spin asymmetry:  Study helicity dependent structure functions!  Study transverse dependent structure functions! • Single longitudinal-spin asymmetry: • Single transverse-spin asymmetry:  Study parity violation effects!  Study left/right asymmetries! • Statistical significance (FOM=figure-of-merit):  Single spin asymmetry:  Double spin asymmetry: Bernd Surrow

5. Introduction • Description of ALL in terms of polarized parton distributions: f f1 f2 Spin asymmetry of sub-process: Bernd Surrow

6. Introduction Forward 0 (π0 γγ) production xF ( E0/Ebeam)  0.2 – 0.6 and pT 1 – 3 GeV • Determination of AN requires three measurements: • AN : DIFFERENCE over SUM – In general quite small  Require therefore: • Statistical precision • Control of systematic effects • Spin dependent event yield: N() • Relative luminosity: R=L/L • Beam polarization: P • Experimental aspects on asymmetry measurement at RHIC: AN • Measurement of AN for forward π0 production at STAR: π0 p() p • Asymmetry: Bernd Surrow

7. Polarized proton collider RHIC Absolute Polarimeter (H jet) • Overview of RHIC polarized pp collider complex RHIC pC Polarimeter Siberian Snakes BRAHMS & PP2PP PHOBOS Lmax = 2 x 1032 cm-2s-1 70% Beam Polarization PHENIX 50 < √s < 500 GeV Siberian Snakes STAR Spin Rotators Partial Siberian Snake 2  1011 Pol. Protons / Bunch  = 20  mm mrad FY02 devices LINAC Pol. Proton Source 500 mA, 300 ms BOOSTER FY03 devices AGS Internal Polarimeter AGS 200 MeV Polarimeter FY03 and beyond AGS pC Polarimeter Rf Dipoles Bernd Surrow

8. Polarized proton collider RHIC • Performance overview • Installation and commissioning of AGS partial snake magnet • Commissioning of polarized gas jet target ( Absolute polarization measurement) • Commissioning of 250GeV ramp • Adequate time for commissioning and luminosity development • Commissioning status: • Siberian snake and spin rotator magnets successfully commissioned • Fast polarimeters in AGS/RHIC demonstrated to work • Spin transfer AGS to RHIC demonstrated to work Rate • RHIC performance in FY02: BBC MinBias Polarization RHIC SPIN effort is in the very beginning of its multi-year program! Background: Blue beam Background: Yellow beam • Beam energy: 100 GeV • Inst. luminosity:  5 • 1029 s-1 cm-2 • Integrated luminosity:  0.3pb-1 • Polarization:  0.2 (transverse) • First trans. spin result! 300k 0.5 RHIC FY03 store: #3714 (05/15/03) Polarization 0.4 200k 0.3 • RHIC performance in FY03: 0.2 100k • Beam energy: 100 GeV • Inst. luminosity:  2 • 1030 s-1 cm-2 • Integrated luminosity:  0.5 pb-1(trans.) 0.4 pb-1 (long.) • Polarization:  0.3 (transverse and longitudinal) • First ALL measurement! L = 2 x 1030 cm-2 s-1 0.1 0.0 06:00 08:00 10:00 12:00 Time of Day Bernd Surrow

9. The STAR detector • Overview Upgrade program of the STAR experiment for the first polarized proton collisions (FY02/FY03): • Beam-Beam Counter (BBC): (2 <  < 5) • Relative luminosity measurement • Rejection of beam-gas event in pp collisions • Minimum bias trigger • Beam tuning to make collisions at STAR • Luminosity monitor • Forward-Pion Detector (FPD) (3 <  < 4) • Electromagnetic calorimeter system: Prototype setup of 3 Pb-glass arrays and 1 Pb-scintillator calorimeter east side for FY02 • Upgrade in FY03: Pb-glass array on EAST/WEST • Energy and shower profile measurement (0  ) • Event yield for Forward 0 production • Commissioning of EM-calorimeter modules and trigger (Barrel: -1 <  < 1 & Endcap: 1.09 <  < 2) • Commissioning of spin scaler system FPD East FPD West BBC East BBC West ~7.5m ~7.5m Bernd Surrow

10. Barrel Calorimeter: -1 <  < 1 • Endcap calorimeter: -1.09 <  < 2 • Lead-scintillator EM calorimeter (~20 X0 ) • 120 modules with: ΔΦ X Δη= 0.1 X 1.0 • 40 towers per module:ΔΦ X Δη = 0.05 X 0.05 • Shower max. detector (SMD): wire proportional counter (γ/π0 discrimination) • Pre-shower layers • Installed (FY04): 90/120 • Instrumented towers: 75/120 • Instrumented SMD: 75/120 • Lead-scintillator calorimeter (~24 X0) • 780 towers with: ΔΦ = 0.1, Δη = 0.057 at η = 1.09 to 0.099 at η = 2 • Shower max. detector (SMD): scintillator strip layers (γ/π0 discrimination) • Pre-shower and post-shower layers • Complete EEMC installed (FY04 run) • Instrumented: 720 towers and 1/3 (4 sectors) SMD and pre/post shower The STAR detector • STAR calorimeter system: Endcap and Barrel Completion and full exploitation of STAR barrel and endcap calorimeter system crucial for STAR SPIN program! Bernd Surrow

11. Relative Luminosity 05/16/03 - 05/30/03 • Determine relative luminosity of bunch-crossings with different polarization • Accuracy: δRstat ~ 10-4 – 10-3 and δRsys ~ 3·10-3 First results in polarized pp collisions • STAR BBC luminosity monitoring Luminosity BBC E•W counts Bunch Crossing • Abort gaps  beam-gas background! Polarization pattern at STAR: Spin Up Spin Down Unpolarized Bernd Surrow

12. First results in polarized pp collisions • First measurement of AN for forward π0 production at RHIC • AN is found to increase with energy similar to E704 result (s = 20 GeV (10 X smaller than at RHIC), 0.5 < pT < 2.0 GeV) • This behavior is also seen by several models which predict non-zero AN values • Several approaches beyond the basic “naive QCD calculations” yield non-zero AN values at RHIC energies: • Sivers: include intrinsic transverse component, k, in initial state (orbital momentum) (before scattering takes place) • Collins: include intrinsic transverse component, k, in final state (transversity) (after scattering took place) • Qiu and Sterman (Initial-state twist-3)/Koike (final-state twist-3): more “complicated QCD calculations” (higher-twist, multi-parton correlations) Bernd Surrow

13.  AN/AL:  ALL/ATT: Future MIT research interests • Access ΔG in polarized pp collisions • ΔG sensitivity in polarized pp collisions • High-pT (prompt) photon production • Jet production • Heavy-flavor production • Access ΔG: Double longitudinal-spin asymmetry ALL • Theoretical advantage of RHIC: W. Vogelsang, M. Strattmann  Study helicity dependent structure functions! • Measurement of ALL requires: • N+(-) : Spin dependent event yield • R: Relative luminosity • P: Beam polarization • FOM ( = Figure-Of-Merit):  Smaller scale dependence at RHIC compared to HERMES/COMPASS! Bernd Surrow

14. Future MIT research interests • Background: • π0(η0)  γγ: π0(η0)/γ discrimination needed • Isolation cone requirement • The golden channel at RHIC: Quark-Gluon Compton scattering • ALL for QGC scattering interpreted in LO QCD: • Polarized cross-section is strongly peaked when photon is emitted in direction of incident quark • Best determination of ΔG for: final-state photon || to initial-state quark Gluon polarization pQCD result for QGC scattering Measured asymmetry from polarized DIS • Note: QGC scattering dominates over competing background process: • Reconstruction of initial-state partonic kinematics: • Event-by-event determination of pT,γ (photon energy), ηγ(photon direction) and ηjet (jet direction) allows to reconstruct: • Large x quark (large quark polarization) analyzes small-x gluons (gluon-rich) • Asymmetric QGC scattering (forward boost in direction of incident quark) Bernd Surrow

15. Future MIT research interests • Quark-Gluon Compton scattering: Prospects at STAR • Simulated ALL at two different RHIC center-of-mass energies:: • Multi year program at RHIC which requires: • High luminosity • High polarization • s = 200 / 500GeV • Combined data sample at 200 GeV and 500 GeV is essential to minimize extrapolation errors in determining ΔG: Accuracy: 0.5 • Ultimately: Global analysis of various ΔG! Bernd Surrow

16. Future MIT research interests • Prospects on constraining ΔG from inclusive jet production in RUN4 (FY04) • Simulation based on Pythia including trigger and and jet reconstruction efficiencies • Assume: Coverage of EMC (barrel)  0 < Φ < 2π and 0 < η < 1 • Jet Trigger: ET > 5 GeV over at least one “patch” (Δη = 1) X (ΔΦ = 1) • Jet reconstruction: Cone algorithm (seed = 1GeV, R = 0.7) • Polarization: 40% - Luminosity: 3pb-1 Bernd Surrow

17.       E E M C E E M C     Future MIT research interests • W production: Flavor dependence • W± production in pp collisions probes flavor structure of QCD sea analogous to deep-inelastic scattering • Polarized proton beams allow the measurement of (the expected large) parity violation in W± production • Forward e detection (Asymmetric partonic collisions!) gives direct access to probe the underlying quark (anti-quark) polarization which is dominated at RHIC by u/d quarks Bernd Surrow

18. Future MIT research interests • Inner and forward tracking upgrade at STAR • Experimental issues for W case: • e+e- charge sign determination (Select W+/W-) • e/h discrimination (Full EEMC capabilities crucial!) • Trigger: High pT single EM-cluster in BEMC/EEMC tower • Formulated as long-term goal in STAR Decadal Upgrade Plans to BNL Management • Main physics motivation: W physics (Polarized pp program) and Heavy Quark production (Au-Au and polarized pp program) • MIT kick-off meeting on inner/forward tracking upgrade: November 7-8, 2003 • Overview of physics case, possible tracking layout and technology choices (Pixel/GEM/Silicon) • Discussion on upgrade strategy, staging of various projects and overall organization • Profit from MIT LNS silicon laboratory and MIT-BATES (Proposal of a GEM facility!) to strongly participate in the STAR tracking upgrade • New STAR Working Group (MIT, LBL, IUCF, Yale, BNL, CalTech,…) on STAR tracking upgrade: Simulation and design work  Aim for a proposal by summer 2005! Bernd Surrow

19. Future MIT research interests • Timeline (Machine and detector upgrade) RHIC RUN NEW EQUIPMENT TO STAR/RHIC SPIN New AGS warm snake; H gas jet; RF spin flipper; BEMC preshower; EEMC SMD + preshower; completed FPD New strong AGS cold snake; Completed BEMC, EEMC (incl. postshower); Evtl. forward hadron calorimeter Work to achieve full design L and Pbeam ; s = 500 GeV commissioning; STAR TOF barrel Improved STAR inner/forward tracker Test L improvement schemes; calibrate Pbeam to 10%; continue ALL(jets) Calibrate Pbeam to 5%; improve L; Collins frag. with forward 0’s; more ALL(jets); first look at +jet ALL( + jet), transversity measurements at mid-rapidity, at s = 200 GeV FY04 FY05 FY06+07 FY08+09 ALL( + jet), AL(W±) at s = 500 GeV Bernd Surrow

20. Up to 10 GeV injector 5-10 GeV static e-ring BRAHMS & PP2PP PHOBOS RHIC STAR PHENIX Pol. Proton Source LINAC BOOSTER AGS Summary and Outlook • RHIC Spin program at BNL • First successful polarized proton collisions ever at RHIC (transverse and longitudinal) • Successful upgrade and commissioning of various new STAR components for the first polarized proton run at RHIC • Unique opportunity to explore the spin structure of the proton in a new unexplored regime at RHIC over the next years. Focus on: • Gluon polarization • Flavor decomposition • This requires various accelerator, polarimeter and detector components to be completed (High polarization and luminosity  Continuous pp running and development crucial)! • Profit from infra-structure at MIT-LNS and MIT-BATES towards STAR tracking upgrade A very exciting time is ahead of us to explore the spin structure of the proton at RHIC and to establish a new ep/eA facility at BNL! • Future eRHIC program at BNL • Explore new QCD regime in eA (high parton density – saturation phenomena) and polarized ep scattering (complement ongoing RHIC physics activities) • Unique opportunity to establish such a QCD facility at BNL! Bernd Surrow