Absolute polarimetry a t RHIC Hiromi Okada (BNL) I. Alekseev, A. Bravar, G. Bunce, S. Dhawan, O. Eyser, R. Gill, W. Haeberli, O. Jinnouchi, A. Khodinov, K. Kuri ta, Z. Li, Y. Makdisi, I. Nakagawa, A. Nass, S. Rescia, N. Saito, E. Stephenson, D. Svirida, T. Wise, A. Zelensk i 1.How to measure absolute beam polarization? 2.Polarized hydrogen atomic gas jet target system 3.Recoil spectrometer and analysis 4.A N results from RUN4 5.Beam polarization measurements from RUN5 6.Next step towards the best accuracy
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Absolute polarimetry at RHIC Hiromi Okada (BNL) I. Alekseev, A. Bravar, G. Bunce, S. Dhawan, O. Eyser, R. Gill, W. Haeberli, O. Jinnouchi, A. Khodinov,
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Absolute polarimetry at RHIC
Hiromi Okada (BNL)I. Alekseev, A. Bravar, G. Bunce, S. Dhawan, O. Eyser, R. Gill,
W. Haeberli, O. Jinnouchi, A. Khodinov, K. Kurita, Z. Li, Y. Makdisi, I. Nakagawa, A. Nass, S. Rescia, N. Saito,
E. Stephenson, D. Svirida, T. Wise, A. Zelenski
1. How to measure absolute beam polarization?
2. Polarized hydrogen atomic gas jet target system
How to choose an ideal interaction for polarimeter ?
inp
outp A
Polarized Proton beam
Elastic scattering process Elastic scattering process ppAA ppAA in very small in very small --tt region. region. Our case: A is proton or Carbon.Our case: A is proton or Carbon.
AGS and RHIC polarimeter complex
IP12
AGS ppCC polarimeter pC pC
Beam
H-Jet polarimeter pp pp RHIC ppCC polarimeter
pC pC
Wednesday 15:40~
Y. Makdisi
• Calibration for RHIC pC polarimeter (OFFLINE)
• ONLINE monitor,• Fill by Fill beam
polarization (OFFLINE).
Ptarget from BRP
<Pbeam> from H-Jet-polarimeter
Effective ANpC of RHIC p
C-polarimeter
Fill by fill beam polarizations for experiments
AN of pp pp
Physics motivation.
Confirmation of the system works well.
Road to fill by fill Pbeam (OFFLINE)
target , beam
beampC
H-jet polarimeterRHIC pC polarimeter
Details of pC pol. are …
Today 16:00 ~
A. Bazilevsky
B. Morozov
Thursday 9:00~
I. Nakagawa
Beam and target are both protons, AN should be same.
Ptarget is measured by BRP precisely.
Method to get <Pbeam>
P
P
tAbeam
beam
etargt
etargtN
RHIC proton beam
Forward scatteredproton
H-jet target
recoil proton
PPetargt
beametargtbeam
02 inout ppt
Minimize systematic Minimize systematic uncertainty by using the uncertainty by using the same system !same system !
Checking AChecking ANN, we confirm , we confirm
our system works our system works properly.properly.%5
P
P
P
P
target
target
beam
beam
How precisely we know AHow precisely we know ANN??
2hadNF
emNF
*hadSF
hadNF
emSFN ImA
Physics motivation: Precise AN data in CNI region
• Unpredictable• Parameter r5
Re r5= 0.02 r5= 0 Re r5= 0.02
E704, FNAL 200 GeV/c
Phys. Rev. D 48, 3026 (1993)
0.001
Understanding of AN before 2004
0.001
Expected to be dominant and calculable.
1st term
%5A
A
N
N
Spin-orbit interaction from the motion of the neutron magnetic moment in the nuclear-coulomb field (Schwinger 1948)
• Target thickness along z-axis: (1.3 0.2 )1012 atoms/cm2
Achieve designed values! Measurements were done by using 2.0
mm diameter compression tube
Fix RHIC proton beam position (diameter ~1mm).
Move H-Jet-target system for every 1.5 mm step.
Recoil detector can detect H-Jet-target !
Using RHIC-beam and Recoil detector
Using 2.0 mm diameter compression tube
Find the best collision point !
Recoil detector set up
Analysis
1. Recoil proton kinetic energy correction
2. Elastic event selection
Raw asymmetry
RHIC proton beam
H-jet target
IP12
recoil proton
Si detectors (8cm 5cm)3 L-R sides
Strip runs along RHIC beam axis
1ch width = 4mm (400strips)
Channel # relates to recoil angle R, 5 mrad pitch.
Each channel measures kinetic energy TR and TOF.
L = 0.8 m
Read out electronics
Three left-right pairs of Si detectors
・ 96 read-out channels
・ 96 charge-sensitive preamplifiers
RHIC-ring, IP12 Recoil spectrometer
Counting room
1. Signal shaping
2. Wave Form Digitizer
3. DAQ-PC55 m twisted pair cables (category 5)
Ch#1
source for energy calibration 241Am(5.486 MeV)
How to identify elastic events ?
proton beam
Forward scatteredproton
proton target recoil proton
Array of Si detectors measures TR & ToF of recoil particles. Channel # corresponds to recoil angle R.2 correlations (TR & ToF ) and (TR & R ) the elastic process
Recoil proton kinetic energy corrections -t-t = 2m = 2mppTTRR
Measured deposit energy = kinetic energy ; 1< TR <7 MeV
Energy loss correction in “the entrance-window” for low energy recoil protons: TR < 1 MeV.
Full Full depositdeposit
Punch-throughPunch-through
Punch through correction for high energy recoil protons: TR > 7 MeV.
R
p
T2
mLcal.ToF
Recoil protons : |ToFca
l. ToF| < 8 nsec
Blue area: |ToFcalToF| 8 nsec
Red line:expected spectrum from ToF and TR resolutions
Recoil proton identification
Forward scattered proton identification
Blue area: ”selected” channels
Red line: Expected spectrum from TR and R resolutions
22RpR #chsinm2T
Select proper 2 ~3 channels for each TR bin.
Channel#
Inelastic threshold
Calculation is done using square-root formula target : Based on H-Jet target polarization sign. (sign changes every 500 seconds) beam : Based on beam polarization sign. (sign changes every bunch) Sort with -t (=2mpTR) Apply background correction, RBG: 2~3% (RHIC-beam origin)
BGetargt
etargtN
RLRL
RLRL
R1
1
PA
NNNN
NNNN
Raw-asymmetry calculation of selected elastic events
AN from RUN4
• Compare measured AN and expected curve with |r5| =0 2/ndf = 13.4/14.
• Tool itself has a beautiful AN and described from first principle QED explanation at 100 GeV/c.
PLB 638 (2006), 450-454
AN at 100 GeV/c
|r5| =0
2hadNF
emNF
*hadSF
hadNF
emSFN ImA
Set r5 as free parameter: 2/ndf = 11.1/12 |r5| is consistent with
zero at 100GeV/c !
UnpredictableParameterized with r5
Errors on the data points Errors on the data points are statistics only.are statistics only.
Components of Components of systematic uncertaintysystematic uncertainty