Recent results from high-energy longitudinal polarized proton-proton collisions at 200GeV at RHIC

1. Recent results from high-energy longitudinal polarized proton-proton collisions at 200GeV at RHIC Tai Sakuma MIT

2. The gluon contribution to the proton spin, G, is poorly constrained. -  q p p p g Polarized DIS found that quarks carry only a small fraction of the proton spin G is only loosely constrained from polarized DIS data. ≈0.2 quarks gluons orbital motions proton spin polarized pp

3. One of the goals of RHIC-Spin is to determine G with polarized pp collisions. p p g In proton-proton collisions, gluons are in the initial states at lowest order. polarized pp

4. p p g In polarized pp collisions, ALL is the most important quantity to measure to determine G. ALL • the double spin asymmetry in polarized pp collisions - sensitive to G As an example of ALL, this is one of the early results from STAR. PRL 97 (2006) 252001 polarized pp

5. ALL is sensitive to G The result is compared with theory predictions from GRSV working group. As an example of ALL, this is one of the early results from STAR. PRL 97 (2006) 252001

6. ALL is sensitive to G GRSV xG(x) The result is compared with theory predictions from GRSV working group. PRL 97 (2006) 252001 • GRSV polarized pdf • PRD 63 (2001) 094005 • GRSV - std • GRSV - max • GRSV - min • GRSV - zero Best fit to pDIS Large uncertainty 3 extreme scenarios

7. ALL is predicted for various final states with different G models GRSV xG(x)   jet 

8. ALL is measured for various final states  jet J/      

9. STAR inclusive jet ALL • 2006 RHIC Run • 4.7 [pb-1] • Polarization ~60% • Jet Patch Trigger Energy in a patch of calorimeter towers (x  = 1 x 1) > 8.3 GeV • Midpoint Cone Algorithm Cone Radius = 0.7 • PARTICLE jet pT Corrected measured jet pT to true jet pT with Pythia MC sample systematics

10. STAR inclusive jet ALL The results are compared with the GRSV ALL predictions.

11. STAR inclusive jet ALL The series of G spanning G-min and G-max To quantify the impact on G

12. STAR inclusive jet ALL ALL predictions based on the series of G The series of G spanning G-min and G-max To quantify the impact on G

13. STAR inclusive jet ALL Comparison of the results with the series of the ALL predictions allowed region GRSV STD ALL predictions based on the series of G Confidence Levels from the comparison For example, the C.L. for G = 0.3 is about 0.1%. This means that if G = 0.3 is true, the probability that we observe ALL that is in worse agreement than the ALL we actually observed is 0.1 percent.

14. STAR inclusive jet ALL allowed region Impact on G GRSV STD • The 2006 results excluded G < -0.7 and G > 0.2 with C.L. 90% within the GRSV framework. • The results are consistent with pDIS data. Confidence Levels from the comparison For example, the C.L. for G = 0.3 is about 0.1%. This means that if G = 0.3 is true, the probability that we observe ALL that is in worse agreement than the ALL we actually observed is 0.1 percent.

15. PHENIX Inclusive π0 ALL •   • highly segmented EMCal x  = 0.01 x 0.01 • Run 5 3.5 [pb-1] Polarization ~ 50% • Run 6 7.5 [pb-1] Polarization~ 60% Final scaling error will be ~10% • Soft physics contribution ~ 10% at 2 GeV • Corrected for the background ALL

16. PHENIX Inclusive π0 ALL ALL predictions based on the series of G

17. PHENIX Inclusive π0 ALL Comparison of the results with the series of the ALL predictions ALL predictions based on the series of G • Within the GRSV framework, 2min = 7/~7 NDF 2min + 3 -0.8 < G < 0.2

18. The constraints on G from the STAR and PHENIX results inclusive 0 inclusive jets The combined results constrain G STAR and PHENIX results are consistent and complementary The analysis was done within the GRSV framework

19. Beyond GRSV framework The analysis was done within the GRSV framework

20. Beyond GRSV framework The analysis was done within the GRSV framework

21. Beyond GRSV framework The range of x probed is 0.02 < x < 0.3 The analysis was done within the GRSV framework

22. Beyond GRSV framework Gehrmann-Stirling Set C (GS-C) has highly polarized gluon in low x and G = 1 The range of x probed is 0.02 < x < 0.3 The analysis was done within the GRSV framework

23. Beyond GRSV framework Gehrmann-Stirling Set C (GS-C) has highly polarized gluon in low x and G = 1 The range of x probed is 0.02 < x < 0.3 ALL for GS-C is consistent with the results from RHIC Spin

24. Beyond GRSV framework Gehrmann-Stirling Set C (GS-C) has highly polarized gluon in low x and G = 1 The range of x probed is 0.02 < x < 0.3 G = 1 is ruled out within the GRSV framework but is still possible for much different shape of xG(x)

25. The low-x region needs to be measured. 500 GeV Forward , +jet The range of x probed is 0.02 < x < 0.3 Forward Meson Spectrometer (FMS)

26. -  q p p p g New global analysis is starting at BNL. G(x) models ALL predictions pDIS data ALL measurements constrains on G

27. -  q p p p g New global analysis is starting at BNL. New global analysis at BNL • include both pDIS and RHIC Spin data for global fits of the polarized pdf. • started at BNL in the Fall 2007. • collaborative effort of theorists from GRSV, DNS and experimentalists from STAR and PHENIX. pDIS data ALL measurements

28. Summary • ALL for various final states in polarized pp collisions is measured at 200 GeV at RHIC. • ALL from RHIC is constraining G to -0.8 < G < 0.2 with 90% C.L. within the GRSV framework and the probed x range of 0.02 < x < 0.3. • Significant measured sensitivity is expected at RHIC with , +jet channels and 500 GeV run with access to lower x. • A global analysis of the polarized parton distributions with pDIS and RHIC data is starting at BNL.