RHIC Polarimetery in Run9, sqrt(s)=200 GeV

A.Bazilevsky for RHIC Polarimetry group

RHIC Spin Collaboration MettingMay 15 (Friday), 2009

pC Rate historys=200 GeV

Target changed in Yellow1 to thicker one (from Fill 10686) Rate problems!

Target changed in both Blues from fill 10732 Blue2 rates slightly increased

pC measurements

Fills 10616 (Apr 18) – 10749 (May 15)

“Online” polarizations: 0.50-0.60

Pol-1 measure slightly lower than Pol-2: by ~6%

Blue1/Blue2: consistent within stat. uncertainties

Yell1/Yell2: shows variations above stat. uncertainties

Online Polarization (%), not normalized (!) vs fill

pC-Blue vs HJet

Hjet/pC is stable over fills within (large) stat. errors (of HJet)

HJet: <P>=55%(fills 10616-10732)

HJet/Blue1 1.05

HJet/Blue2 0.99

pC-Yellow vs HJet

Hjet/pC is stable over fills within (large) stat. errors (of HJet)

HJet: <P>=55%(fills 10616-10732)

HJet/Yell1 1.07

HJet/Yell2 1.00

More precise Hjet-pC comparison

Hjet: fills combined in 9 periodsClear correlation between Hjet and pCConsistency vs period within 5%

pC-blueHJet

pC-yellowHJet

pC: Pol. Profile 2

2

P

IR

Polarimeters 2Polarimeters 1

Usual…R0.15 in previous years (100 GeV beams)R0.1 Experiments see 5% more polarization than Hjet

Horizontal profile

Vertical profile

Vertical profile

Vertical profile

Horizontal profile Horizontal profile

Backups

Summary

HJet: Running in stable conditions: <P>~55%

pC: Blue1 vs Blue2 consistent behavior

Yell1 vs Yell2 show systematic effects ~5-7% (may be due to larger rate effects in Yell1)

pC vs Hjet: consistent within stat. errorsHjet/Pol1 ~ 1.06; Hjet/Pol2 ~ 1

Might be ~5% drop in the pC measurements from the beginning to the end of the run due to detector degradation (“dead layer” increase)

Measurements are statistically consistent within a fill

Polarization decay Tdecay ~ 100-200 hours

Polarization profile no sharper than in previous yearsExperiments see ~5% more polarization than Hjet

Measurements at injection and flattop are consistent within ~2%

Rate historys=500 GeV

C Mass

pC: Polarization Profile

pC Scan C target over the beam cross:

Target Position

Inte

nsity

Pola

rizati

on

2

2

P

IR

I

P

2. Obtain R directly from the P(I) fit:

2

2

max 2exp)(

P

xPxP

2

2

max 2exp)(

I

xIxI

R

L

LPP

maxmax

P

I

Precise target positioning is NOT necessary

1. Directly measure I and P :

R=0.290.07

pC: Consistency within a Fill

pC: Consistency within a Fill

Clear polarization decay

Consistent between Pol1 and Pol2

10685-Blue10704-Blue

Statistically Ok !

pC: Consistency within a Fill

Should be uniform if variations within a fill are only due to stat. errors

Should show higher density near 0 if there are “sizable” syst. effects

Prob(2, NDF) – from the fit to a constant in a fill

No systematic effects (comparable to stat. errors) are seen within a fill

Pol. Decay

<Tdecay> = 80-180 hours

<Tdecay> = 250-800 hours

May need rate correction!

Run6:

<Tdecay> ~150 hours

Run8:

<Tdecay> ~400 hours

<Tdecay> ~100 hours

In a fill: fit to exp(-t/Tdecay)

pC: pol. at injection

Pol1 measures smaller values than Pol2 by ~5%(similar to flattop, or slightly smaller due to smaller rate effect at injection)

<P>~56%(similar to flattop)

pC: injection vs flattop

On the average no difference within 2%:

Assuming that we don’t lose polarization on the ramp AN(inj)/ AN(ftp) is known within 2% Correction due to rate effect and polarization decay at store may be needed

Assuming that AN(inj)/ AN(ftp) is correct Polarization loss on the ramp <2%

(-2.11.2)%

(-0.91.1)%

(-1.21.0)%

(3.52.5)%