Download - RHIC Polarimetery in Run9, sqrt (s)=200 GeV
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RHIC Polarimetery in Run9, sqrt(s)=200 GeV
A.Bazilevsky for RHIC Polarimetry group
RHIC Spin Collaboration MettingMay 15 (Friday), 2009
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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
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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
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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
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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
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More precise Hjet-pC comparison
Hjet: fills combined in 9 periodsClear correlation between Hjet and pCConsistency vs period within 5%
pC-blueHJet
pC-yellowHJet
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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
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Backups
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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%
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Rate historys=500 GeV
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C Mass
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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
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pC: Consistency within a Fill
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pC: Consistency within a Fill
Clear polarization decay
Consistent between Pol1 and Pol2
10685-Blue10704-Blue
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Statistically Ok !
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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
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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)
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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)
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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)%