Gluon Polarization Errors at PHENIX Spin Discussion Mar. 24 & Apr. 14, 1998 Yuji Goto, RIKEN

gluon polarization measurement at PHENIX prompt photon measurement inclusive  0 measurement heavy quark measurement –J/  e + e -,  +  - –open charm single lepton e  coincidence prompt photon A LL (from N.Saito)

uncertainties x-independent uncertainties –beam polarization –luminosity x-dependent uncertainties –background subtraction –higher order correction –quark polarization –event selection uncertainties in x estimation –momentum scale –p T vs x

x-independent uncertainties beam polarization –absolute value 10% pion polarimeter - 10% by comparing E704 pC CNI –absolute value 5% pp with pol. hydrogen jet –relative value Goal:<1% –polarimeter at PHENIX ? - longitudinal

x-independent uncertainties (contd.) luminosity –absolute value 10% machine luminosity from accelerator parameters BBC + calculation –absolute value 5% Roman pot measurement at PP2PP –relative value BBC - 100K counts/sec (crossing by crossing) - saturated ZDC - 1K counts/sec (crossing by crossing)

x-dependent uncertainties statistics for prompt photon –320pb -1 for sqrt(s)=200GeV –800pb -1 for sqrt(s)=500GeV  G/G 5% - 30% statistical error for sqrt(s)=200GeV, p T = GeV/c, 5GeV/c p T bin

x-dependent uncertainties (contd.) background subtraction (for prompt photon) –reconstruction of  0 and  - 2-photon decay background - escape photon, 2-photon merge, other decays correction - asymmetry measurements of  0 and  –hadron & bremsstrahlung full detector simulation necessary –How much asymmetry remains after subtracting backgrounds considering their asymmetries ? event selection <1%? –trigger efficiency –acceptance –efficiency correction isolation cut

x-dependent uncertainties (contd.) background for prompt photon b.g. <20% for sqrt(s)=200GeV, p T = GeV/c, 5GeV/c p T bin normalized by (2  detected) normalized by after isolation cut

x-dependent uncertainties (contd.) background for prompt photon charged hadron - E/p matching by EMCal and tracking neutral hadron - shower shape anslysis by EMCal Estimation must be done with current algorithm Algorithm must be developed

x-dependent uncertainties (contd.) theoretical uncertainties –annihilation process (for prompt photon) –higher order correction –fragmentation function –color singlet - octet model (for J/  ) –Q 2 (from N.Saito) fraction of <20% & experimental determination of is necessary

x-dependent uncertainties (contd.) higher order correction L.E.Gordon and W.Vogelsang, PRD49 (1994) 170 LO NLO

x-dependent uncertainties (contd.) quark polarization (for prompt photon) –DIS experimental error & theoretical calculation –E143 - g 1 p /F 1 p error 20%-8% for x= in 15bins –asymmetry measurement of W/Z(/DY) hep-ph/ SMC - squares E143 - solid circles [Q 2 >1(GeV/c) 2 ] diamonds [Q 2 <1(GeV/c) 2 ]

uncertainty in x estimation (for prompt photon) momentum scale –momentum resolution, binning effect –systematic uncertainty - non-linearity of EMCal PMT, FEE, shower leakage –1% non-linearity - 6% cross section error at sqrt(s)=500GeV, p T =20GeV/c p T vs x –correlation –uncertainty due to k T binning effect uncertainty >50% (* slope of asymmetry)

uncertainty in x estimation (for prompt photon) p T vs x - uncertainty by k T –In PYTHIA initial radiation, k T 2 =(1-z)Q 2 z: splitting fraction of initial radiation k T 2 =0

global analysis and  0 production, open charm, DIS, semi-inclusive measurements,... (from N.Saito)

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