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p 0 Double Longitudinal Spin Asymmetry in Polarized pp Collisions at .. = 200 GeV

p 0 Double Longitudinal Spin Asymmetry in Polarized pp Collisions at .. = 200 GeV. Kieran Boyle (Stony Brook U.) for the PHENIX Collaboration. D g 2. D g D q. D q 2. Motivation. with DS ~20%, D g, D L unknown. How to measure D g:. p 0. Hard Scattering Process.

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p 0 Double Longitudinal Spin Asymmetry in Polarized pp Collisions at .. = 200 GeV

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  1. p0 Double Longitudinal Spin Asymmetry in Polarized pp Collisions at .. = 200 GeV Kieran Boyle (Stony Brook U.) for the PHENIX Collaboration Kieran Boyle PANIC—October 24,2005

  2. Dg2 DgDq Dq2 Motivation with DS ~20%, Dg, DL unknown How to measure Dg: p0 Hard Scattering Process ~ agg * Dg2 + bgq * Dg + cqq Kieran Boyle PANIC—October 24,2005

  3. ALL Requirements • PHENIX • p0 Cross section • Relative Luminosity (R=L++/L+-) • dR=1.0e-4 • (Local) Polarimetry • ALL • Method • Result ++ same helicity + opposite helicity Kieran Boyle PANIC—October 24,2005

  4. BBC ZDC ZDC PHENIX Detector PbSc p° detection • Electromagnetic Calorimeter: • High pT photon trigger to collect p0's • Acceptance: h<|0.35|, f = 2x p/2 • High granularity (~10*10mrad2) Relative Luminosity • Beam Beam Counter (BBC) • Acceptance: 3.0< h<3.9 • Zero Degree Calorimeter (ZDC) • Acceptance: ±2 mrad Local Polarimetry • ZDC PbGl Kieran Boyle PANIC—October 24,2005

  5. g-g Mass Spectrum Kieran Boyle PANIC—October 24,2005

  6. Run5 p0 Cross Section • Consistent with previous results. • Extends previous results to pT of 20 GeV/c. • Theory is consistent with data over nine orders of magnitude. Kieran Boyle PANIC—October 24,2005

  7. Relative Luminosity • Number of BBC triggered events used to calculate Relative Luminosity. • For estimate of Uncertainty, fit where • dR=1.0e-4 • dALL=2.3e-4 • ALL of BBC to ZDC consistent with zero Kieran Boyle PANIC—October 24,2005

  8. Use ZDC to measure a L-R and U-D asymmetry in forward neutrons. When transversely polarized, we see clear asymmetry. When longitudinally polarized, there should be no asymmetry. Local Polarimetry at PHENIX Raw asymmetry Raw asymmetry BLUE YELLOW Idea: Use neutron asymmetry to study transversely polarized component. f f Kieran Boyle PANIC—October 24,2005

  9. LR c2/NDF = 82.5/97 p0 = -0.00423±0.00057 c2/NDF = 88.1/97 p0 = -0.00323±0.00059 UD XF>0 XF>0 UD c2/NDF = 119.3/97 p0 = -0.00056±0.00063 c2/NDF = 81.7/97 p0 = -0.00026±0.00056 LR XF<0 XF<0 Measured Asymmetry During Longitudinal Running <PT/P>= 10.25±2.05(%) <PL/P> = 99.48±0.12±0.02(%) <PT/P>= 14.47±2.20(%) <PL/P> = 98.94±0.21±0.04(%) Kieran Boyle PANIC—October 24,2005 Fill Number Fill Number

  10. Calculating ALL • Calculate ALL(p°+BG) and ALL(BG) separately. • Get background ratio (wBG) from fit of all data. • Subtract ALL(BG) from ALL(p°+BG): ALL(p°+BG) = wp° · ALL(p°) + wBG · ALL(BG) p°+BG region : ±25 MeV around p° peak BG region : two 50 MeV regions around peak Kieran Boyle PANIC—October 24,2005

  11. Fill by Fill ALL Kieran Boyle PANIC—October 24,2005

  12. Bunch shuffle 1<pT<2 GeV/c 2<pT<3 GeV/c 3<pT<4 GeV/c 4<pT<5 GeV/c • Randomly reassign helicity for each fill and recalculate asymmetry. • Do 1000 times and look at c2 distribution. • Agree with expected distribution • Bunch to bunch systematics smaller than current statistics. 5<pT<6 GeV/c 6<pT<7 GeV/c 7<pT<8 GeV/c 8<pT<9 GeV/c Kieran Boyle PANIC—October 24,2005

  13. AL consistent with zero Kieran Boyle PANIC—October 24,2005

  14. p0 ALL • Comparison with previous Runs • Confidence levels: • Run3 : 17.6 % • Run4 : 18.7 % • They are consistent. (Scale error is not considered.) Kieran Boyle PANIC—October 24,2005

  15. Comparison with theory ¨ GRSV: M. Gluck, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 53 (1996) 4775. * At input scale: Q2 = .4 GeV Kieran Boyle PANIC—October 24,2005

  16. Values for ALL and AL * At input scale: Q2 = .4 GeV Kieran Boyle PANIC—October 24,2005

  17. Conclusions • We measured cross section and double helicity asymmetry ALL in p0 production from Run5 pp collision. • The results of ALL are consistent with Run3/4. • The data are compared with theoretical models. • Run5 conclusively excludes GRSV maximal scenarios. • Data consistent with GRSV standard and GRSV DG = 0. Kieran Boyle PANIC—October 24,2005

  18. Backups Kieran Boyle PANIC—October 24,2005

  19. Photon Trigger Efficiency Kieran Boyle PANIC—October 24,2005

  20. Distinct and Merged Photons Kieran Boyle PANIC—October 24,2005

  21. Minimum Bias (BBC |z|<30) • Minimum Bias in coincidence with High Energy Photon trigger (Cluster Energy>1.4GeV) Kieran Boyle PANIC—October 24,2005

  22. Cross Section consistant with Run3 result. Kieran Boyle PANIC—October 24,2005

  23. Yellow Beam LR c2/NDF = 119.3/97 p0 = 0.00727±0.00060 c2/NDF = 68.1/97 p0 = -0.00226±0.00069 UD XF>0 <PT/P>= 14.47±2.20(%) <PL/P> = 98.94±0.21±0.04(%) XF>0 UD c2/NDF = 82.3/97 p0 = -0.00067±0.00064 c2/NDF = 83.0/97 p0 = -0.00089±0.00061 LR XF<0 XF<0 Kieran Boyle PANIC—October 24,2005

  24. BRAHMS & PP2PP (p) PHENIX (p) STAR (p) RHIC RHIC CNI (pC) Polarimeters Absolute Polarimeter (H jet) Siberian Snakes Spin Rotators 2  1011 Pol. Protons / Bunch e = 20 p mm mrad Partial Siberian Snake LINAC BOOSTER Pol. Proton Source 500 mA, 300 ms AGS AGS Internal Polarimeter 200 MeV Polarimeter Rf Dipoles RHIC accelerates polarized protons to (presently) 100 GeV Kieran Boyle PANIC—October 24,2005

  25. p0 Production Kieran Boyle PANIC—October 24,2005

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