1. RHIC Spin Experiments L.C. Bland, for the RHIC spin collaboration Brookhaven National Laboratory Workshop on Hadron Structure and Spectroscopy Paris, March 1-3, 2004 Long-term goals Polarized protons in RHIC STAR and PHENIX Results from first polarized proton collisions Plans for the future Summary

2. RHIC Spin Collaboration Organization RHIC Spin Collaboration (Spokesman: G. Bunce) Develops overall spin plan; forum to coordinate spin issues for RHIC accelerator and experiments. Spin physics is an integral part of the goals of the STAR, PHENIX and pp2pp experiments. RHIC Accelerator Spin Group (Spokesman: T. Roser, Project Manager: W. Mackay) Accelerator physics for spin (Siberian Snakes, Spin Rotators,`Spin Flipper’); polarized ion source; polarimeters. RIKEN and RIKEN/BNL Research Center (Group Leaders: H. En’yo, G. Bunce) Funds spin physics equipment; develops polarimetry; organizes spin workshops; supports young physicists. STAR Spin Physics Working Group (Conveners: L. Bland, H. Spinka) PHENIX Spin Physics Working Group (Conveners: Y. Goto, K. Barish) pp2pp Experiment (Spokesman: W. Guryn) BNL Groups: RHIC Spin Group (Group Leader: G. Bunce); RBRC/Nuclear Theory Develop / exploit spin capability of RHIC; coordinates accelerator / experiment activities; complete measurements; members in STAR, PHENIX and pp2pp experiments. Laboratory / University participation BRAHMS collaboration, PHENIX collaboration, pp2pp collaboration, STAR collaboration New groups: Cal Tech, Colorado, Illinois, MIT

3. The Relativistic Heavy Ion Collider at Brookhaven National Laboratory R-HI New state of matter QGP De-confinement … polarized proton Nucleon Spin Structure Spin Fragmentation pQCD … RHIC is a QCD lab PHENIX STAR Brhams pp2pp

4. Equipment to be installed after FY03 Polarized Proton Operation at RHIC Equipment/developments for runs 2 (1/02) and 3 (3/03  5/03)… Helical dipole snake magnets CNI polarimeters in RHIC,AGS  fast feedback  *=1m operataion spin rotators  longitudinal polarization

5. Gluon Contribution to the proton’s spin qg Compton scattering with polarized protons provides a direct measure of gluon polarization. Coincident detection of  and away-side jet  event determination of initial-state partonic kinematics.

6. Flavor Decomposition of the proton’s spin  W ± production probes flavor structure analogous to deep inelastic scattering.  Polarized proton beams allows the measurement of (the expected large) parity violation in W ± production.  Forward ,e detection (dominated by production of W ’s with large longitudinal momentum) gives direct probe of quark (antiquark) polarization: projections

7. STAR EndCap EMC (1/3) BBC West EMC (Half) Barrel BBC East Forward Pion Detectors (E & W) STAR Au+Au,  s = 200 GeV NN See NIM A499 (2003) STAR features large acceptance Run 2003 configuration Complete endcap EMC towers in place for run 2004 Complete barrel EMC towers in place for run 2005 STAR

8. STAR Electromagnetic Calorimeters Invariant Mass (GeV/c ) 2  0 (p T > 3 GeV/c) Recon- struction with Barrel EMC Barrel EMC: 2400/4800 towers installed for 2003, with SMD but not yet preshower readout Endcap EMC: 240/720 towers installed; no SMD, preshower or postshower readout yet STAR

9. PHENIX Detector Philosophy: High rate capability & granularity Good mass resolution and particle ID  Sacrifice acceptance  0 reconstruction and high p T photon trigger: EMCal: |  |<0.38,  =  Granularity  = 0.01  0.01 Minimum Bias trigger and Relative Luminosity: Beam-Beam Counter (BBC): 3.0<|  |<3.9,  =2 

10. A N measured in E704 at Fermilab at  s=20 GeV, p T =0.5-2.0 GeV/c: BRAHMS proposal: measure A N for p  p    + X at  s=200 GeV,   ~3.9   measurements   measurements x F p T (GeV/c) Cts/hour 0.21 1.0 6454 0.21 1.0 5296 0.25 1.4 1068 0.25 1.4 807 0.30 1.9 163 0.30 1.9 91 0.35 2.5 24 0.35 2.5 12 Rate estimates Assume L ~ 1.5  b -1 s -1

11. What is required for a spin experiment at RHIC? (a summary of the multiple concurrent experiments) Production of high-energy/intensity/polarization proton bunches that collide  A successful accelerator physics experiment employing ‘snakes’,rotators,etc. Rarest probes require P beam =70% and  L dt = 320(800) pb -1 at  s = 200(500) GeV Large experimental facilities capable of detecting hadrons/jets, , e ,   …  Experimental sophistication comparable to other colliders (Tevatron, HERA,…) Polarimeters to monitor polarization and establish its absolute magnitude  Coulomb-nuclear interference / polarized gas jet target / local polarimeters Require  P beam / P beam ~ 5% Interaction-region monitors of spin-dependent relative luminosity  Precision experiments to minimize systematic errors in final answer

12. CNI Polarimeters Ultra-thin Carbon target 5  g/cm 2 600  m width beam direction AGS (new for run 3) RHIC 50cm 1 3 4 5 6 2 30cm  2 rings Si strip detectors (Time, Energy) Measure recoil carbons from elastic scattering Exploit analyzing power, A N  0.01, originating from anomalous magnetic moment of proton. Calibration of A N required. Measure left/right (more generally, azimuthal variation) spin-dependent asymmetry Polarimetry Procedure

13. Spin-03 Alessandro Bravar A N : p  C  pC at RHIC energy (100 GeV) recoil Carbon energy (keV) A N (%) preliminary “ CNI ” blue beam yellow beam AGS for normalization assume A N (24.3 GeV) = A N (100 GeV) i.e. no energy dependence [0.009 < |t| < 0.022 (GeV/c) 2 ] very similar shape of the t dependence at 24 and 100 GeV  suggestive of very small energy dependence for A N between 24 and 100 GeV systematic error for RHIC data < 30 %

14. Luminosity Monitoring and Relative Luminosity Measurement -To determine the relative luminosity of bunch crossings with different polarization directions - abort gaps  beam-gas background Polarization pattern at STAR: Spin Up Spin Down Unpolarized Luminosity BBC EW counts Bunch Crossing Abort gaps J. Kiryluk (UCLA) SPIN 2002

15. Relative Luminosity Measurement - Beam-Beam Counters – high rates - BBC scaler information available for each STAR run; typical STAR run duration from a few minutes to several hours ) - total number of counts from the BBC scaler and used in the analysis: N=8 x 10 9 - statistical accuracy of relative luminosity  R stat ~ 10 -4 – 10 -3 Example of R 01/11/02 01/23/02 J. Kiryluk (UCLA) SPIN 2002

16.  RHIC is first polarized collider: an enormous technical achievement!  Significant technical challenges remain to reach pp design goals.  To reach design goals on which spin program was based – P beam =0.70, L = 6  10 31 at  s = 200 GeV  factor of ~1000 improvement in P 4 L – requires additional equipment and beam development time! Polarization (P beam ) A typical store at RHIC, 5/15/03 STAR BBC MinBias Background Blue beam Background Yellow beam 0.5 0.4 0.3 0.2 0.1 0.0 (P beam ) L = 2 x 10 30 cm -2 s -1 06:00 08:00 10:00 12:00 Time of Day 300 200 100 0 Machine Progress Toward RHIC Spin ¯    Rate (kHz)

17. Run 2 Progress / Results  L dt ~350 nb -1 and ~ 18% (Yellow) / 15% (Blue) delivered to experiments. Polarization limited by performance of AGS. STAR / PHENIX / pp2pp experiments commissioned for pp collisions at  s = 200 GeV. Critical pp reference measurements for heavy-ion program completed providing important physics results. Transverse single-spin measurements completed providing physics results + local polarimeters for spin-rotator tuning in Run 3. Siberian Snakes work to preserve polarization through acceleration and store.

18.  0 Cross Section The data covers over 8 orders of magnitude –by combining minimum bias trigger and EMCal trigger data NLO pQCD calculation is consistent with data –CTEQ5M PDF + KKP FF S.S. Adler et al. (PHENIX), PRL 91, 241803 (2003).

19. Di-jet Reference for Heavy-Ion Physics (jet physics is central to spin program) STAR p+p,  s = 200 GeV Hadronic high-p T azimuthal correlations in pp collisions di-jet events clearly observed in pp collisions at  s = 200 GeV. di-hadrons serve as di-jet surrogates for heavy-ion collisions. clear near-side and away-side di-hadron correlations in pp collisions serve as contrast for central AuAu collisions where away-side correlations are strongly suppressed. Phys. Rev. Lett. 90 (2003) 082302 STAR

20. Measurement of small-angle p  p  elastic scattering at 50   s  500 GeV; 4 x 10 -4   t   1.3 (GeV/c) 2 using Si strip detectors in Roman Pots above and below the beam. pp2pp Run-2 Results acceptance Slope parameter (b) S. Bueltmann, et al. Phys. Lett. B579 (2004) 245.

21. Forward Cross Sections vs. NLO pQCD Final results for  =3.8 were submitted to PRL and are available at hep-ex/0310058 Results for forward   production cross sections measured at STAR (details, and final results, follow) are in fair agreement with NLO pQCD calculations that use factorization and renormalization scales equal to p T of the  . Data compares much more favorably to NLO pQCD for forward   production at RHIC than for fixed target (  s ~ 20 GeV) or ISR energies (  s ~ 60 GeV).

22. STAR-Spin Results from Run 2 Measured cross sections consistent with pQCD calculations Large transverse single-spin effects observed for  s = 200 GeV pp collisions STAR collaboration Submitted to PRL for publication hep-ex/0310058 The analyzing power result for forward   production is proportional to the (presently unmeasured) analyzing power of the CNI polarimeter. A hydrogen gas jet target is ready for installation in RHIC run 4 for calibration of the CNI polarimeter effective analyzing power via pp elastic scattering.

23. g+g q+g Soft processes q+g  q+g+g PYTHIA: a guide to the physics… PYTHIA prediction agrees well with the inclusive  0 cross section at  3-4 Dominant sources of large x F   production from: q + g    + X (2  2) q + g  q + g + g    + X (2  3) Forward Inclusive   Cross-Section: Subprocesses involved: qg  q  g g

24. Hadron Cal Base Pb Scintillator W+Fiber Cal Post-shower Y. Fukao (Kyoto) SPIN 2002 Analyzing Power for Forward Neutron Production at  s = 200 GeV (Run 2 Result) Charge Veto EM Cal Base PbWO 4 Neutron Veto Results from run 2 are basis for PHENIX local polarimeter used in run 3

25. RHIC performance at FY03 run 0 10 20 30 40 50 70 60 50 40 30 20 10 0 Time in days (1=04/01/03) Polarization at Store Blue RingYellow Ring Max at injection ~50%, Max at 100GeV P~40% Average P beam ~25% Improved by factor of ~2 over FY02 Yellow ring affected by problem with snake magnet 0 10 20 30 40 50 Transverse 0.5/pb Longitudinal 0.4/pb Integrated Luminosity New problem ‘beam-beam tune shifts’ surfaced, limiting luminosity Adequate to accomplish physics goals from Run 3.

26. Spin Rotators and Local Polarimetry Calculations establish a working point and the dependence of transverse polarization components on spin rotator currents. Local polarimeters are needed to measure vertical,radial polarization components at interaction region.

27. PHENIX Local Polarimeter SMD Forward neutron transverse asymmetry (A N ) measurements SMD (position) + ZDC (energy) ZDC Vertical   ~ ±  /2 Radial   ~ 0 Longitudinal  no asymmetry  distribution

28. PHENIX Local Polarimeter: Spin direction confirmation BlueYellow BlueYellow BlueYellow Spin Rotators OFF Vertical polarization Spin Rotators ON Correct Current ! Longitudinal polarization! Spin Rotators ON Current Reversed Radial polarization

29. OFF  P vert ON  P long STAR spin rotator: Mistuned rotators STAR Spin Rotator Magnet Tuning (Run 3 Result)  Longitudinal Polarization at STAR LR T B * BBC West BBC East Interaction Vertex 3.3<|  |< 5.0 use segmentation of inner tiles of BBC as a Local Polarimeter monitoring pp collisions. Rotators OFF  BBC L/R spin asymmetries comparable to RHIC polarimeter (CNI). Rotators ON  adjust rotator currents to minimize BBC L/R and T/B spin asymmetries. RHIC polarimeter (CNI) establishes polarization magnitude. Local polarimeter (BBC) establishes polarization direction at STAR. (  10 3 )

30. Transverse Single Spin Asymmetries – Preliminary Results Left-Right BBC asymmetry ( Vertical P beam component ) Top-Bottom BBC asymmetry ( Radial P beam component ) Blue Beam Yellow Beam Blue Beam  (CNI) Ratio:  (BBC East)/  (CNI) consistent with  (BBC West)/  (CNI) We get: A N (BBC)=0.0066(8) Stat. error only! using: A N (CNI) = 0.0118 (10) from CNI online analysis Yellow Beam BBC East BBC West 5  effect - may be a result of a broken snake? Consistent with zero - as expected for vertical polarization

31. PHENIX and STAR Jet/Hadron A LL Measurements in 2003 PHENIX Preliminary Both collaborations are ready to make high-impact A LL measurements as soon as machine performance and available beam time permit! STAR projected 2003 statistical uncert. from ongoing jet analysis

32. How can one infer the dynamics of particle production? Two particle (h ± ) correlations: Inclusive   cross section as a function of p T Multi-particle correlations:  Midrapidity particle production at large momentum transfer in p + p collisions is dominated by 2  2 (or 3, …) parton scattering Mid-rapidity particle production from p + p collisions at  s = 200 GeV

33. Back-to-Back Correlations p + p    + h ± + X,  s = 200 GeV Midrapidity h  tracks… Vector sum of all tracks with: -1 <  < +1 p T > 200 MeV/c Require |  p| T > 1 GeV/c Define:     p  E  > 25 GeV     3.8 pp   h±h± pp

34. PYTHIA expectations for back-to-back correlations: 40-50 20-30 30-40 E  (GeV)  s:b increases with increasing x F  width decreases with increasing x F p + p    + charged hadrons + X (  s = 200 GeV, no detector effects)   -   p -  |  p| T (GeV/c) Forward    =3.8… Midrapidity h  … Vector sum of all h  momenta with: -1 <  < +1 p T > 200 MeV/c Require |  p| T > 1 GeV/c Represent  distribution with Gaussian (s) + constant (b)  hadrons 

35. p + p    + h ± + X (    =3.8) E  (GeV) 25-35 35-45 45-55 Statistical uncertainties only… Significant back-to-back correlations for all x F, in agreement with PYTHIA Quantitative comparison to models  determinations of k T and j T smearing in p + p… STAR PRELIMINARY DATA Forward    =3.8… Midrapidity tracks… Vector sum of all tracks with: -1 <  < +1 p T > 200 MeV/c Require |  p| T > 1 GeV/c STAR

36. Conclusions Forward   from p + p collisions NLO pQCD (and PYTHIA  LO + parton showers) agrees with inclusive cross section measurement, unlike lower  s data PYTHIA says large-x F, large-    come from 2  2 and 2  3 parton scattering with small contributions from soft processes Back-to-back particle correlations with midrapidity charged particles qualitatively agree with PYTHIA  Forward   meson production at RHIC energies comes from hard partonic scattering Spin effects Comparison with d + Au Flavor tagging Important result for:  STAR

37. 01/22/04 1 PP FY04 Run Goal 55 bunches with 1x10 11 per bunch, emittance: 15  mm-mrad Average current/ring: 70mA Peak luminosity: 11x10 30 cm -2 s -1 Average luminosity: 6.0x10 30 cm -2 s -1  * = 1m at STAR and PHENIX Polarization at store >=0.40 Ultimate goal for PP FY2004: – 55 bunches w. 2x10 11 per bunch – 112 bunches w. 1x10 11 per bunch Achieved in PP FY03 55 bunches w. 0.7x10 11 per bunch, emittnace: 15  mm-mrad Average current/ring: 48mA Peak luminosity: 6.0x10 30 cm -2 s -1 Average luminosity: 3.0x10 30 cm -2 s -1  * = 1m at STAR and PHENIX Polarization at store: 0.30

38. 01/22/04 1 Strategies to achieve the goal Ameliorate beam-beam effect – New working point – Reducing beam-beam driven resonances by adjusting phase advance between IRs IR non-linearity correction Pushing and learning the limit of the achievable proton intensity – NEG coating – beam scrubbing Beta squeeze along the ramp – Avoid hysteresis effect when beta squeeze at flattop, so the machine is more reproducible Better model engine – Ironing the tune & chromaticity along the ramp(Johannes) PLL: feedforward Smaller emittance to gain luminosity Multi-bunch injection – Gain the average luminosity

39. Wolfram Fischer RHIC Run-4 Au+Au Luminosity evolution As of 02/22/04 22:00 Star  0.9 Phobos  0.3 Brahms  0.4 Delivered 762 (  b) -1 to Phenix 128 (  b) -1 last week [best week: 153] minimum projection physics target maximum projection [projection and target for 14 weeks of physics run]

40. Atomic Hydrogen Beam Source separation magnets (sextupoles) H 2 dissociator Breit-Rabi polarimeter RHIC beam focusing magnets (sextupoles) RF transitions holding field magnet p recoil arms recoil detectors

41. January 21, 2004Alessandro Bravar Recoil spectrometer 2004 RUN WILL INSTALL 6 DETECTORS ON BLUE BEAM ONLY will have “design” azimuthal coverage one Si layer only  smaller energy range  reduced bkg rejection power B

42. January 21, 2004Alessandro Bravar The road to P beam Requires several independent measurements 0 target polarization P target (Breit-Rabi polarimeter) 1 A N for elastic pp in CNI region: A N = 1 / P target  N ’ 2 P beam = 1 / A N  N ” 1 & 2 can be combined in a single measurement: P beam / P target = -  N ’ /  N ” 3 CALIBRATION: A N pC for pC CNI polarimeter in detector kinematical range: A N pC = 1 / P beam  N ”’ (1 +) 2 + 3 measured almost simultaneously alternating p and C CNI polarimeters 4 BEAM POLARIZATION: P beam = 1 / A N pC  N ”” to experiments at each step pick-up some measurement errors: transfer calibration measurement requires < 10 7 pp CNI events

43. Where we are in the program… Siberian Snakes – demonstrated to work P beam at RHIC injection energy – now 0.4 / goal is 0.7 Fast polarimeters in AGS and RHIC – demonstrated to work P beam transfer AGS  RHIC – demonstrated to work P beam preserved in RHIC ramp to 100 GeV– demonstrated to work P beam preserved in RHIC ramp to 250 GeV – to do P beam maintained during RHIC store – 14 hours observed longitudal P beam at PHENIX,STAR / local polarimetry – demonstrated to work  P beam / P beam to  5% – commission gas jet in 2004;  10% in 2004;  5% in 2005 L avg week to 20(50) pb -1 at  s=200(500) GeV – now ~0.3 pb -1 at  s=200 GeV Polarization reversal of stored beam – to do      

44. Summary of RHIC Spin Program as of 3/04 Measured cross sections and particle correlations from p + p collisions at  s = 200 GeV are consistent with expectations of pQCD. Analyzing powers observed for mulitple processes from p + p collisions at  s = 200 GeV. Spin rotator magnets were successfully tuned to produce longitudinal polarization at PHENIX and STAR interaction regions. First measurements of A LL for midrapidity   and jet production are underway and will continue for RHIC runs 4,5  sensitivity to gluon polarization. Polarized gas jet target is ready for commissioning and is planned for the calibration of the RHIC beam polarization via pp elastic scattering.