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Recent results from high-energy longitudinal polarized proton-proton collisions at 200GeV at RHIC Tai Sakuma MIT The gluon contribution to the proton spin, G, is poorly constrained. - q Polarized DIS found that quarks carry only a small fraction of the proton spin ≈0.2 p quarks G is only loosely constrained from polarized DIS data. gluons orbital motions proton spin p p g polarized pp One of the goals of RHIC-Spin is to determine G with polarized pp collisions. In proton-proton collisions, gluons are in the initial states at lowest order. p p g polarized pp 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 PRL 97 (2006) 252001 As an example of ALL, this is one of the early results from STAR. p p g polarized pp ALL is sensitive to G The result is compared with theory predictions from GRSV working group. PRL 97 (2006) 252001 As an example of ALL, this is one of the early results from STAR. ALL is sensitive to G GRSV xG(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 ALL is predicted for various final states with GRSV xG(x) different G models je t ALL is measured for various final states je t J/ 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 ALL systematics (x 10-3) Jet Reconstruction + Trigger Bias [-2, +5] (pT dep) Non-longitudinal Polarization ~0.03 (pT dep) Relative Luminosity 0.94 Backgrounds 0.5 (1st bin), 0.1(else) STAR inclusive jet ALL The results are compared with the GRSV ALL predictions. STAR inclusive jet ALL To quantify the impact on G The series of G spanning G-min and G-max STAR inclusive jet ALL ALL predictions based on the series of G To quantify the impact on G The series of G spanning G-min and G-max STAR inclusive jet ALL allowed region Comparison of the results with the series of the ALL predictions 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. STAR inclusive jet ALL allowed region GRSV STD Impact on 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. 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. 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 PHENIX Inclusive π0 ALL ALL predictions based on the series of G 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 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 Beyond GRSV framework The analysis was done within the GRSV framework Beyond GRSV framework The analysis was done within the GRSV framework Beyond GRSV framework The range of x probed is 0.02 < x < 0.3 The analysis was done within the GRSV framework Beyond GRSV framework GehrmannStirling Set C (GS-C) has highly polarized gluon in low x and G = 1 The analysis was done within the GRSV framework The range of x probed is 0.02 < x < 0.3 Beyond GRSV framework GehrmannStirling Set C (GS-C) has highly polarized gluon in low x and G = 1 ALL for GS-C is consistent with the results from RHIC Spin The range of x probed is 0.02 < x < 0.3 Beyond GRSV framework GehrmannStirling Set C (GS-C) has highly polarized gluon in low x and G = 1 G = 1 is ruled out within the GRSV framework but is still possible for much different shape of xG(x) The range of x probed is 0.02 < x < 0.3 500 GeV Forward , +jet The low-x region needs to be measured. Forward Meson Spectrometer (FMS) The range of x probed is 0.02 < x < 0.3 New global analysis is starting at BNL. G(x) models - ALL predictions q p pDIS data ALL measurements p constrains on G p g New global analysis is starting at BNL. - q New global analysis at BNL 1. p pDIS data 2. 3. 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. ALL measurements p p g 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.
