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Constraints on Gluon Polarization in the Proton from PHENIX A LL data

Constraints on Gluon Polarization in the Proton from PHENIX A LL data. A.Bazilevsky Brookhaven National Laboratory 2007 Annual Meeting of the Division of Nuclear Physics of the American Physical Society October 10-13, 2007 Marriott Newport News at City Center Newport News, VA USA.

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Constraints on Gluon Polarization in the Proton from PHENIX A LL data

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  1. Constraints on Gluon Polarization in the Proton from PHENIX ALL data A.Bazilevsky Brookhaven National Laboratory 2007 Annual Meeting of the Division of Nuclear Physics of the American Physical Society October 10-13, 2007Marriott Newport News at City CenterNewport News, VA USA

  2. Unpol. Cross Section in pp pp0 X : PRD76, 051106 (2007) pp X: PRL 98, 012002 ||<0.35 Good agreement between NLO pQCD calculations and data  confirmation that pQCD can be used to extract spin dependent pdf’s from RHIC data. • Same comparison fails at lower energies

  3. Double longitudinal spin asymmetry ALL is sensitive to G Probing G in pol. pp collisions pp  hX

  4. PHENIX Preliminary Run5 pi0 ALL pp0 X : PRD76, 051106 (2007) Data not consistent with “G=G” Data consistent with “G=0” and “std” Let’s try to say more…

  5. GRSV: G/G(x) and 0 ALL By W.Vogelsang & M.Stratmann GRSV: G(Q2=1GeV2)= 1.76  +1.89 For each G refit of DIS data is done

  6. Only experimental stat. errors included: 1: [ 0.07; 0.3] 3: [-0.9; 0.5] 3 Scale uncertainty Experimental syst. uncertainties (scale and shift) can be easily included 1 Chi2 vs G pp0 X : PRD76, 051106 (2007) No theoretical uncertainties considered

  7. Chi2 vs G: recent data Calc. by W.Vogelsang and M.Stratmann  • “std” scenario, G(Q2=1GeV2)=0.4, is excluded by data on >3 sigma level: 2(std)2min>9 • Only exp. stat. uncertainties are included (the effect of syst. uncertainties is expected to be small in the final results) • Theoretical uncertainties are not included

  8. Remark: Global fit vs G fit From M. Stratmann For each G,  is refit  we’re doing “a king of” global analysis of DIS + PHENIX data (constraining both G and  ) If  is fixed (known from somewhere else), the constrain of G from RHIC ALL data will be considerably stronger

  9. Remark: G shape Gehrmann-Stirling models Current 0 ALLdata is sensitive to G for xgluon= 0.020.3 We use GRSV model: fixed functional shape of G(x) We can use our technique to investigate the sensitivity of our data to G(x) shape within our xgluon range (“almost” model independent constrain of G in limited xgluon range )

  10. Once again … • 2 map from our experimental data includes only stat. uncertainties  define 1 (3) uncertainty for G from 22min = 1 (9). • Effect of experimental syst. uncertainties can be easily included. • Other data can be easily included in this fit (taking into account exp. syst. uncertainties, both correlated and non-correlated, properly) • Will include soon the  and  ALL at sqrt(s)=200 GeV; and 0 ALL data at sqrt(s)=62 GeV • Shape of G(x) for limited x range can be studied

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