RHIC Polarimetery in Run9, sqrt (s)=200 GeV
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Transcript of RHIC Polarimetery in Run9, sqrt (s)=200 GeV
RHIC Polarimetery in Run9, sqrt(s)=200 GeV
A.Bazilevsky for RHIC Polarimetry group
May 12, 2009
HJet
HJet
proton beam
Forward scatteredproton
proton target recoil proton
Array of Si detectors measures TR & ToF of recoil proton. Channel # corresponds to recoil angle R.Correlations (TR & ToF ) and (TR & R ) the elastic process
BLUE side
YELLOW side
Energy vs Channel #
ToF vs Energy
HjetFill 10663
target
target beam
beam PP target
target beam
beam PP
Hjet: StabilityTarget asymmetry
Should be constant vs fill (for fixed Ptarget)
Should be consistent between blue and yellow
0.04170.0004 vs 0.04180.0004
Should be consistent between Years (for fixed Ptarget)
Run5: 0.04090.0004
Run6: 0.04130.0002
Run8: 0.04220.0003
Multi-Year consistency within ~1%
targettarget P
A ppN
Hjet: StabilityBackground
Background (with two beam mode) is on the same level as with one beam mode
~Constant vs fill
On the same level as in Run5&6(removed collimators in Run8 larger background)
Hjet: results
<P>=55%
<P>=55%
Fill-by-fill variations as well as variations within a fill should be estimated from pC polarimter
pC
pCTwo independent
polarimeters in each ring(so 4 polarimeters!)
12 carbon targets in each polarimter (6 vertical and 6 horizontal)6 detectors in each polarimeter3 types of detectors: “BNL strip”: 12 strip in each detector
“Hamamatsu strip”: 12 strip in each of 2 detector (blue2)
“Hamamatsu pad”: 2 pads in each of 2 detector (yellow2)
Ultra thin Carbon ribbon Target(5 g/cm2)
11
3344
55
66
22
Si strip detectorsSi strip detectors(TOF, E(TOF, ECC))
18cm18cm
pC Rate historys=200 GeV
Severe rate problems observed during Run9 sqrt(s)=500 GeV
Higher rate lower measured polariation
Target changed in Yellow1 to thicker one (from Fill 10686) Rate problems!
pC measurements
Fills 10616 (Apr 18) – 10713 (May 8)
“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
May show a gradual decrease (5-7%) from fill 10616 to 10713may come from detector degradation
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 10616-10713)
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 10616-10713)
HJet/Yell1 1.07
HJet/Yell2 1.00
More precise Hjet-pC comparisonHjet: fills combined in 8 periodsClear correlation between Hjet and pCConsistency vs fill 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
Horizontal profile
pC: Consistency within a Fill
pC: Consistency within a Fill
Clear polarization decay
Consistent between Pol1 and Pol2
10685-Blue10704-Blue
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: Injection
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>~55%(similar to flattop)
pC: injection vs flattop
On the average no difference within 4%:
Assuming that we don’t lose polarization on the ramp AN(inj)/ AN(ftp) is known within 4% 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 <4%
SummaryHJet:
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 ~4%Correction for polarization decay and rate effects at flattop may lead to even better consistentcy…
“Fast offline” results can be used only with special care/cautionNeeds monitoring: parameter retuning sometimes fails
Backups
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
Statistically Ok !