Yousef I. MakdisiEIC Meeting

Dec 7-8, 2007

Polarized Proton/ Hadron PolarimetryWith heavily reliance on the PSTP and RSC presentations

K. Boyle, C. Camacho, H. Okada, S. Bazilevsky, I. Nakagawa, G. Bunce, L. Trueman

A preamble:Polarimeter requirements for RHICCandidate processes for high energy polarimeters

“State of the art?” What Hurdles? Further improvements 3He polarimetry Summary

Polarimeter requirements

A polarimeter has to satisfy the following:Beam polarization monitor for Physics ( < 5 % )Several samples over one fillBeam polarization diagnostic and Machine tuning tool Sample on demand and online, fast/within minutes Low systematic errorsA large dynamic range & Energy independenceLarge analyzing power, large cross section, & low background

Figure of merit (to optimize) is A2

Reasonable Cost

Unlike electron polarimeters where processes are calculable, proton reactions rely on experimental verification specially at high energies.

Measuring the beam polarization

In accelerators, the stable spin direction is normally vertical (up/down).

We measure using a nuclear reaction in a plane that is perpendicular to the polarization direction.

NL and NR are the number of scatters to the left and right.

A: is the analyzing power of the reaction

The statistical error in the measurement for PA << 1 is

The polarimeter figure of merit (to optimize) is A2

: is the cross section of the reaction

PA

N N

N N

L R

L R

1

PA N NL R

1 1

Candidate processes for polarimeters Vs. Energy

For transverse beam polarization

pp Elastic scattering

Inclusive Pion Production (significant asymmetry)

p-C elastic scattering in the CNI region (asymmetry few percent)

p-p elastic scattering in the CNI region and Jet targets (similarly)

Asymmetry in pp elastic scattering Vs energy

Good analyzing power at low t~0.3 The Analyzing power drops as 1/p

Reasonable cross sectionThe cross section fall with energy

There are measurements at beam energy of 100 GeV/c with analyzing power of few %

Asymmetry in Inclusive Pion Production

•Large + asymmetries were observed at the ZGS using 12 GeV/c beam on hydrogen and deuterium targets in the mid seventies

Wisdom had it: polarization effects will disappear at high Energies

•Large +/- and o asymmetries were observed at Fermilab with 200 GeV/c incident polarized proton beam on a hydrogen target

•For RHIC: we needed to assure the following:The asymmetry is large over the entire RHIC energy range especially at injection

A nuclear target does not dilute the asymmetry (A theorist’s warning!!!)

The - asymmetries continue to exhibit the same behavior as + as they

are easier to detect with lower background

Large Asymmetries in inclusive pion production

ZGS AGS Fermilab

(12 GeV/c) (22 GeV/c) (200 GeV/c)

Phys. Lett. B261(1991)201Phys. Lett. B264(1991)462

Phys. Rev. D.18 (1978) 3939-3945

Phys.Rev.D65:092008,2002

This formed the basis of our first design

p-p and p-C elasctic scattering the CNI region

The asymmetry is “calculable”:

J. Schwinger, Phys. Rev. 69,681 (1946)

First suggested by Nural Akchurin (Iowa) Weak beam momentum dependence The analyzing power a few percent High cross sectionRBRC Workshop (Buttimore, Kopeliovich,

Leader, Soffer, Trueman) The single flip hadronic amplitude

Unknown, estimated at ~15 % uncertainty A simple apparatus

(detect the slow recoil protons or carbon

@ ~ 900 in the lab)

PR D

48 (1993) 3026-3036

pC concept test: first at IUCF and later at the AGSCarbon targets to survive the RHIC beam heating

FermilabE704

p-Carbon CNI polarimeters

recoilCarbon

polarizedbeam

scatteredproton

Carbon

target

t = (pout – pin)2 < 0

Tkin 2 MC

0.01 < |t| < 0.02 (GeV/c)2

rightleft

rightleft

NB NN

NN

AP

1

•High counting rate, a 2% statistical measurement in <1 min.•Analyzing power ~1-2% over the carbon energy range•High statistics 105/ch/sec allow bunch to bunch analysis•Several measurements per store.•Target scans provide beam intensity and polarization profiles •Carbon targets: ~10 um, difficult to fabricate, mount, and drive•Analysis requires energy and timing calibration and Si dead layer correction per channel •Calibrated using the H-Jet at each energy.

Setup for pC scattering – the RHIC polarimeters

Ultra thin Carbon ribbon Target

(3.5g/cm2, 5-10 m wide)beamdirection

1

34

5

6

2

Si strip detectors(ToF, EC)

30cm all Si stripsparallel to beam

Beam direction

•Recoil carbon ions detected with Silicon strip detectors•Readout by specially designed Waveform digitizers•72 channels read out channel (each channel is an “independent polarimeter”)•45o detectors: sensitive to vertical and radial components of Pbeam and unphysical asymmetries

p-Carbon CNI RHIC

EC, keV

TOF, nsTypical mass reconstruction

Carbon

AlphaC*

PromptsAlpha

Carbon

Prompts

MR, GeV

Tkin= ½ MR(dist/ToF)2

non-relativistic kinematics

110 bunches@ flattop messed spin pattern

The RHIC Polarized Hydrogen Jet Target

Hyperfine states (1),(2),(3),(4)

(1),(2)

Pz+ : (1),(4) SFT ON (2)(4)

Pz- : (2),(3) WFT ON (1)(3)Pz0: (1),(2),(3),

(4) (SFT&WFT ON )

•pumps 1000 l/sec compression 106 for H

•Nozzle Temperature 70K

•Sextupoles 1.5T pole field and 2.5T/cm grad.

•RF transitions SFT (1.43GHz) WFT (14MHz)

•Holding field 1.2 kgauss B/B = 10-3

•vacuum 10-8Torr jet on / 10-9 Torr jet off.

•Molecular Hydrogen contamination 1.5%

•Overall nuclear polarization dilution of 3%

•Jet beam intensity 12.4 x 1016 H atoms /sec

•Jet beam polarization 92.4% +/- 1.8%

•Jet beam size 6.6 mm FWHM

•In 2006 the Jet measured the beam to jet polarization ratio to 10% per 6-hr. store.

Target polarization

Correct H2, H2O contamination. Divide with factor 1.037

Ptarget = 92.4% 1.8%1 day

Nuclear polarization of the atoms measured by BRP: 95.8% 0.1%

Nuclear polarization

Polarization cycle (+/ 0/ ) = (300/30/300) seconds

%2P

P

etargt

etargt

No depolarization due to beam bunching observed

Ptarget from BRP

Pbeam by H-Jet-polarimeter

Effective ANpC of RHIC

pC-polarimeter

Fill by fill beam polarizations for experiments

AN of pp pp

1. Confirmation of the system works well.

2. Physics motivation.

Stream of offline analysis

target , beam

beampC

H-jet polarimeterRHIC pC polarimeter

Recoil Silicon Strip Spectrometer

targetNtarget

beamNbeam

PA

PA

targettarget

beambeam PP

NN

NN

For p-p elastic scattering only:

H. Okada et al., PLB 638 (2006), 450-454

Results of AN in the CNI region @ 100 GeV/c

|r5| =0

2hadNF

emNF

*hadSF

hadNF

emSFN ImA

AN Results at Lower RHIC Energies

Set rSet r55 as free parameter as free parameter

Im rIm r55 = = 0.108 0.108 0.074 0.074

Re rRe r55 = = 0.006 0.006 0.031 0.031

22/ndf = 2.87/7/ndf = 2.87/7

preliminary

|r5|=0

0.8 M events 24 GeV/c

31 GeV/c

The analyzing power vs energy seems constant !

5 M events

2005 Polarimeters Normalization Summary

P(blue)/P(blue) = 5.9%

P(yellow)/P(yellow) = 6.2%

[P(blue) x P(yellow) ]/[P_b x P_y] = 9.4%

A_N(2005) = A_N(2004) x (S +/- A(jet stat)/A +/- A(jet syst)/A +/- A(pC syst)/A)

A_N(05)=A_N(04)x( 1.01 +/- .031 +/- .029 +/- .005)

P/P(profile)=4.0%

A_N(05)=A_N(04)x( 1.02 +/- .028 +/- .029 +/- .022)

P/P(profile)=4.1%

Goal:10%

Blue

Yellow

p-Crabon raw asymmetry @ 100 GeV

X-90X-90

X-45X-45

X-averageX-average

Cross asymmetryCross asymmetry

Radial asymmetryRadial asymmetry

False asymmetry ~0

Good agreement btw X90 vs. X45

Regular polarimeter runsRegular polarimeter runs (every 2 hours) (every 2 hours)--measurements taken simultaneously with Jet ---measurements taken simultaneously with Jet -

targettarget--very stable behavior of measured asymmetries--very stable behavior of measured asymmetries----P = 3% per measurement (20 M events, 30 s)P = 3% per measurement (20 M events, 30 s)

H-Jet Performance at 100 GeV

Run6 BlueRun6 YellowRun5 BlueRun5 Yellow

Target asymmetry in Jet-Pol

TRecoil (MeV)

JetTarget

Jet performance is very stable through the YearsBackground is small and its effect on Jet

Target is small Beam polarization is measured reliably by Jet-Pol

pC vs HJet 2006

Fill Number

Hurdles-Monitoring and Analysis

The RHIC polarimetry comprises two separate but connected experiments and analyses requiring a significant collaborative effort and coordination.FY 04 pC polarimeter JetCoordinator A. Bravar (BNL, Phys) Analysis O. Jinnouchi (RIKEN/RBRC) H. Okada (Kyoto)FY05 BravarAnalysis I. Nakagawa (RIKEN/RBRC) K.O. Eyser (UCR)FY06 Bravar, NakagawaAnalysis S. Bazilevsky (RBRC) K. Boyle (USB)

C. M. Camacho (LANL)H. Liu (LANL)

Online A. Hoffman (MIT) R. Gill (BNL-Phys)Monitoring A. Dion (SBU) Zelenski & YM(BNL-CAD)FY08 Bazilevsky, B. Morozov (BNL, Phys)

It takes over a year to produce the final results

Technical Hurdles-Jet Target

The molecular hydrogen fraction represents the largest uncertainty 2%. Better handle on this measurement Assess vs the jet profile Effort is underway to measure in situ using beam luminescence

A better handle on backgrounds from incident beam-gas scattering as well as from the opposite beam. Measure An vs the jet beam profile Simultaneous measurements with both beams.

How close can we get the two beams What is the resultant background Acceptance issues

Improve the jet Pbeam measurement per fill (currently 10% in 6 hrs.) Increase silicon t-range acceptance Open up the holding field magnet aperture

Hurdles pC polarimeters

Data handling: Improve the silicon “effective dead layer” analysis for better stability as

this directly impacts the effective analyzing power. Decouple the Time of Flight and Energy determination Measure the dead layer using a carbon beam from the Tandem

Beam profile and polarization profile Installed a better target drive mechanism Improved the target mounting and positioning mechanism New target mounts allow alternating between vertical and horizontal

targets within one fillVacuum issues with target changing

Borozov: Replace the silicon strips with APDs w/ better energy resolution. A test in the AGS polarimeter is planned for this run.

Molecular Hydrogen Component

With the jet off the beam line, we measured the hydrogen component with a modified 12 mm - wide QMA which covers the full jet profile.

The molecular hydrogen fraction comprised 1.5 % -> 3% nuclear dilution assuming the molecular hydrogen is unpolarized.

We repeated the measurement using an electron beam to ionize the jet beam and a magnet to analyze the outcome. This indicated a similar H2 content. But we could not reproduce the cross section that is quoted in the literature.

We are currently engaging to measure the same in situ using the proton beam luminescence and a CCD camera. We have seen the atomic hydrogen lines but not the molecular line. A spectrometer was installed this year and will attempt the same during the upcoming polarized proton run.

The effort will continue as this represents the largest systematic error from the jet.

Systematics

Fill and collide bunches with different polarization states:

Measure the beam polarization on a bunch by bunch basis Measure the Luminosity for each bunch Measure the asymmetries for each type of bunch crossing Reconfigure the bunch combinations by recogging the beams Flip the beam polarization

p-3He Elastic Scattering (from L. Trueman)

pol. p--3He

p—pol 3He

No Hadron helicity flip Hadron helicity flip

Looking Ahead

The polarized jet target will map the analyzing power in pp elastic scattering at various RHIC energies from 24 GeV/c (injection) to 250 Gev/c (top energy)

Replace the polarized hydrogen jet target with two unpolarized hydrogen targets. (proposed by Bravar)

Increase the jet density several fold resulting in better statistical accuracy within a fill. With higher number of bunches planned for EIC, this represents a lower sensitivity to

rate compared to carbon targets. Recoil elastic protons traverse a significant path in the silicon compared to recoil

carbon. The dead layer correction represents a minimal hurdle to the jet analysis. Need to adjust to the more restricted bunch spacing

p-Carbon polarimeters will be needed for profile / polarization measurements

We need guidance as to what accuracy is required for EIC physics; how many sigma away or scale issues.

Summary

• Proton polarimetery at high energies is NOT an easy task.

• p-Carbon CNI polarimeters form the main stay now in the AGS and RHIC.

• The polarized H-Jet target provided a calibration of the polarimeters at any energy.

• The goal of 5% at 100 GeV was achieved should do the same at any RHIC energy.

• The challenge is still ahead for closer bunch spacing at eRHIC, and to reduce the H-Jet molecular Hydrogen error below 2%.

• We have just started (PSTP2007) to look at 3HeA workshop is planned in conjunction with SPIN 2008

When it comes to proton polarimetry at high energies: we have come a long way!!We have a long way to go if the goals set at the 1-2 % level.

PHENIX (p)

AGS

LINACBOOSTER

Pol. H- Source

Solenoid Partial Siberian Snake

200 MeV Polarimeter

Helical Partial Siberian Snake

Spin Rotators(longitudinal polarization)

Siberian Snakes

Spin Rotators(longitudinal polarization)

Strong AGS Snake

RHIC pC PolarimetersAbsolute Polarimeter (H jet)

STAR (p)

BRAHMS(p)

AGS Polarimeters

Spin flipper