K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -1- Absolute Polarization Measurement at RHIC in the

K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region

-1-

AbsolutePolarization Measurement

at RHIC in theCoulomb Nuclear Interference Region

K. Oleg EyserUniversity of California, Riverside

SPIN 200617th International Spin Physics Symposium

Kyoto, JapanOctober 2, 2006


-2-Polarized Protons in RHIC

this talk: normalization with the Jet Polarimeter

TANSTAAFL !!! (x)

two Carbon polarimeters plus one Jet polarimeter

fast measurements (30 seconds) with fiber targetsneeds normalization

normalization with polarized gas jet targetslow (several days) measurement

(x) R. Heinlein


-3-Polarization Measurement

scattered

recoil

N

L

S

left

right

NN PA

Rabi spectrometer: hydrogen hyperfine structure

Elastic scattering: proton-proton, proton-Carbon, etc.

rightleft

rightleft

NN

NN

cos PAN

W/W0

B/BC


-4-The Jet Polarimeter

x

y

jet

targetNtarget

beamNbeam

PA

PA

targettarget

beambeam PP

96 silicon strips:(6 x 2 x 8)

geometry reflectskinematics of elastic ppscattering

displacement of beams

~ 80 cm

8 cm

5 c

m


-5-DAQ and Calibration

TR (MeV)

t TO

F (

ns)

prompt events (large yield, filtered)

ADCpeak or integral

calibrationAm (5.486 MeV)Gd (3.183 MeV)

TDC¼ rise time

scale 1.19 ns

recoil protonsfrom elastic scattering

2

2

dt

Tm TOFRP

TDC (a.u.)

AD

C (

a.u

.)

FPGA

onboardmemory

DAQ PC

a typical waveform

single strip example


-6-Proton Identification

TR (MeV)

t TO

F (

ns)

20 2 cT

mdttt

R

PTDCTOF

tTDC (ns)

t 0 (

ns)

t0 (ns)

single strip example


-7-Asymmetry Measurement

(dashed)scaled with target polarization:96% atomic / 92% effective

scaled with asymmetry ratio:beam / target(1 MeV – 4 MeV)

rightleftrightleft

rightleftrightleft

NNNN

NNNN

(solid)formal descriptionin terms of helicity amplitudes

M

M

M

M

M

5

4

3

2

1

TR (MeV) TR (MeV)


-8-Background Contributions I

yield (polarization up / down) 1.0 – 1.5 MeV

beamgas background:empty target runs normalized with beam intensities

background yield:between 2.4% and 3.4%

about 0.3 to 0.5 oftotal background

no polarizationdependence


-9-Background Contributions II

abort gap 2abort gap 1

bunch number

bunch number

prompt background contribution from displaced beam in signal region

gap 2

gap 1

abort gaps:prompt background contribution from displaced beamkinematics: no elastic proton signal

background yields:between 1.2 % and 5.0 %

blue

yellowblue

N

NN


-10-Systematic Errors

target

beamtargetbeam PP

,rightleft

rightleft

NN

NN

rightleftNN

NN

,

rightleftrightleft

rightleftrightleft

NNNN

NNNN

target

beamtarget

target

ssbeam

ss

targetbeam NN

NNP

NN

NNPP

)()(

)()(

)()( bs NNN

targetrightleftrightleft

beamrightleftrightleft

targetrightrightleftleftbeamrightrightleftleft

NNNNNNNN

NNNNNNNN

determination of beam polarization:

simple asymmetries:for cross checks

(creates acceptance asymmetry) (creates luminosity asymmetry)

(s)ignal and (b)ackground yields:background 5% - 7%

)(bN not polarizationdependent

background contributes in second orderto determination of beam polarization


-11-Background Effects

elastic pp scattering signal:two detector strips (out of eight) in each (of six) detector pads

background roughlyevenly distributed 4 x background

asymmetries reflect anincrease in background

asymmetry ratio(beam polarization) is onlyweakly affected

backgound yield < 7%systematic error ΔP < 2%

two strips four strips eight strips

t

b

tb,

target asymmetrybeam asymmetry



TR (MeV)TR (MeV)TR (MeV)

TR (MeV)TR (MeV)TR (MeV)


-12-Polarization Measurements at RHIC

%65

pCpCN

N

pptarget

target

beam

beam

A

A

P

P

P

P

goal:

contains systematic errors of Jet and pC

• Polarizations of up to 49.4% have been measured at RHIC in 2005.

• Statistical errors are as small as 1.4%.• An upper limit for systematic uncertainties of 2%

has been determined.• The total uncertainty for fast measurements is

coming close to goal.• Systematic studies of Jet and pC polarimeters

are ongoing.• Hadronic helicity amplitudes can be further

determined from data sets.

yellow beam P ΔPstat

period 1 41.9 % 2.9 %

period 2 41.1 % 2.9 %

period 3 45.4 % 1.4 %

blue beam P ΔPstat

period 1 43.8 % 2.8 %

period 2 48.2 % 3.8 %

period 3 49.4 % 1.7 %

normalization uncertainty for pC measurements


-13-Thank You!

I. Alekseev,(1) A. Bravar,(2) G. Bunce,(2,3)

S. Dhawan,(4) R. Gill,(2) W. Haeberli,(5)

H. Huang,(2) Y. Makdisi,(2), I. Nakagawa,(6)

A. Nass,(7) H. Okada,(6,8), E. Stephenson,(9)

D. Svirida,(1) T. Wise,(5) J. Wood,(2) A. Zelenski (2)

(1) ITEP(2) Brookhaven National Laboratory

(3) RIKEN BNL Research Center(4) Yale University

(5) University of Wisconsin, Madison(6) RIKEN

(7) University of Erlangen(8) Kyoto University

(9) Indiana University, Bloomington

I. Alekseev,(1) A. Bravar,(2) G. Bunce,(2,3)

S. Dhawan,(4) R. Gill,(2) W. Haeberli,(5)

H. Huang,(2) Y. Makdisi,(2), I. Nakagawa,(6)

A. Nass,(7) H. Okada,(6,8), E. Stephenson,(9)

D. Svirida,(1) T. Wise,(5) J. Wood,(2) A. Zelenski (2)

(1) ITEP(2) Brookhaven National Laboratory

(3) RIKEN BNL Research Center(4) Yale University

(5) University of Wisconsin, Madison(6) RIKEN

(7) University of Erlangen(8) Kyoto University

(9) Indiana University, Bloomington

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K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -1- Absolute Polarization Measurement at RHIC in the