RHIC pC Polarimeter status A.Bazilevsky For RHIC CNI Group February 26, 2008

pC: Online Polarizations Only scan measurements at store Measures average polarization over trans. profile This is what directly (should) relate to HJet measurements, but… Absolute scale in not yet fixed A N from Run4! Feb 28Feb 14

pC: averaging Mainly in blue: Intensity profile is flat  we stay longer at beam center than at periphery  measured polarization is closer to P max than to /P max ~ 0.93 for blue, see next slides Yellow looks fine for this

Polarization Profile   P(L/L max ): just an example If there are problems with target position determination  Exclude position from calculations: R=0.29  0.07 for Hjet for experiments (assumes equal horiz. and vert. profiles )

Polarization Profile R vs fill ~ 0.30 /P max ~0.88 ~ 0.16: /P max ~ 0.93 Run5/6: R~ 0.10  0.15

pC stability: “Dead Layer” Thick target  too high event rate (5MHz)

pC stability: T0 Stable

Online vs “fast offline” “Fast offline” and online are different due to QA and energy correction Absolute scale in not yet fixed

pC vs Hjet HJet-yellow HJet-blue P online (pC)/P(Jet)=1.08  %: C energy correction and cuts (online/fast_offline difference) +9%: change in A N A N (Run8)/ A N (Run4)~1.09 A N from Run4! P online (pC)/P(Jet)=1.17  %: from “bad” scans in this period (flat intensity profiles) +4%: C energy correction and cuts (online/fast_offline difference) +7%: change in A N A N (Run8)/ A N (Run4)~1.07 A N (Run5)/ A N (Run4) ~ 1.01 A N (Run6)/ A N (Run4) ~ 1.15

Fast offline, normalized to HJet Feb 28Feb 14 Comparison within a beam can be done using shown (statistical) errors When comparing different beam measurements, the ~6% relative normalization uncertainty should be accounted for

Other exercises Measurements of vert and horiz pol. profiles at injection To check what we get from AGS Looks not sharp (R~<0.1), similar in both directions Measurements with different bunch intensity (0.5, 1.2, 1.5)  AGS pC measurements drop faster than RHIC pC Measurements with different target thickness Two targets with  7 different thickness No difference seen within stat. uncertainties (~5% relative) Continuous scan instead of step-wise Looks working Safer for target, more robust, more flexibility Etc.

Summary HJet demonstrates very stable/consistent measurements Consistent target asymmetry vs -t (with the same target polarization) Same (and even lower in Run8) background level pC data Measurement (finished scans) are stable; QA performed on daily basis Polarization profile in blue is similar to Run5/6; polarization profile in yellow is sharper Experiments see more polarization than HJet due to intensity squared weighting: by 7%-relative in blue and by 12%-relative in yellow (if vertical and horizontal profiles are the same!) Blue-online polarizations are overestimated by (17  6)%-relative +7% - from A N (compared to Run4) Yellow-online polarizations are overestimated by (8  5)%-relative +9% - from A N (compared to Run4)

pC vs STAR Loc. Pol. Pol. Profile correction taken into account: Experiments see 7% (12%) higher polarization in blue (yellow) compared to HJet due to polarization profile (assumes horiz. and vertical profiles are the same) Only “STAR” fills shown