pC polarimeter at RHIC. Status and performance

pC polarimeter at RHIC. Status and performance.

S. Bravar, G. Bunce+, R. Gill, H. Huang, Y. Makdisi, A. Nass,

A. Zelensky: Brookhaven National Laboratory, Upton, USA

O. Jinnouchi: Riken-BNL Research Center, Upton, USA

I. Nakagawa: RIKEN, Saitama, Japan

I.G. Alekseev, V.P. Kanavets, D.N. Svirida: ITEP, Moscow, Russia

S. Dhawan: Yale University, New Haven, USA

W. Haeberli, T. Wise: University of Wisconsin, Madison, USA

G. Igo, C. Whitten, J. Wood: UCLA, Los Angeles, USA

K. Kurita: Rikkyo University, Tokyo, Japan

A. Khodinov: SUNY, Stony Brook, USA

H. Okada, N. Saito: Kyoto University, Kyoto, Japan

W. Lozowski, E. Stephenson: IUCF, Bloomington, USA+ also Riken-BNL Research Center

IX WORKSHOP ON HIGH ENERGY SPIN PHYSICS, Dubna, September 27 - October 1, 2005

Igor Alekseev (ITEP) 2

RHIC-Spin accelerator complexRHIC-Spin accelerator complex

BRAHMS & PP2PP

STARPHENIX

AGS

LINACBOOSTER

Pol. Proton Source

Spin Rotators

20% Snake

Siberian Snakes

200 MeV polarimeter AGS quasi-elastic polarimeter

Rf Dipoles

RHIC pC “CNI” polarimeters

PHOBOS

RHIC

absolute pHpolarimeter

SiberianSnakes

AGS pC “CNI” polarimeter

5% Snake


ChallengeChallenge

1. Absolute polarization measurement with Pbeam / Pbeam < 0.05 for experiments.

2. Fast (< 5 min) measurement for accelerator debugging.

3. Ramp and profile measurements. Fast but relative pC-polarimeter; Slow but absolute p-polarized H-jet polarimeter.

• Road to the absolute polarization:A JET target polarization Ptarget (Breit-Rabi polarimeter)

B AN for elastic pp in CNI region: AN = - 1 / Ptarget N’

C Pbeam = 1 / AN N”

(B & C) can be combined in a single measurement: Pbeam / Ptarget = - N’ / N”

“self calibration” works for elastic scattering only

D CALIBRATION: ANpC for pC CNI polarimeter in covered kinematical range:

ANpC = 1 / Pbeam N”’

(B & C & D) measured simultaneously with several insertions of carbon target

E BEAM POLARIZATION: Pbeam = 1 / ANpC N”” to experiments

1. Absolute polarization measurement with Pbeam / Pbeam < 0.05 for experiments.

2. Fast (< 5 min) measurement for accelerator debugging.

3. Ramp and profile measurements. Fast but relative pC-polarimeter; Slow but absolute p-polarized H-jet polarimeter.

• Road to the absolute polarization:A JET target polarization Ptarget (Breit-Rabi polarimeter)

B AN for elastic pp in CNI region: AN = - 1 / Ptarget N’

C Pbeam = 1 / AN N”

(B & C) can be combined in a single measurement: Pbeam / Ptarget = - N’ / N”

“self calibration” works for elastic scattering only

D CALIBRATION: ANpC for pC CNI polarimeter in covered kinematical range:

ANpC = 1 / Pbeam N”’

(B & C & D) measured simultaneously with several insertions of carbon target



AN arises mainly from interference between EMEM spin-flip amplitudespin-flip amplitude and

hadronic non spin-flip amplitudehadronic non spin-flip amplitude (CNI = Coulomb – Nuclear Interference)

AN arises mainly from interference between EMEM spin-flip amplitudespin-flip amplitude and

hadronic non spin-flip amplitudehadronic non spin-flip amplitude (CNI = Coulomb – Nuclear Interference)

Elastic scattering in the CNI regionElastic scattering in the CNI region

m,p M

TR

M

T

MT

T

p

Mmp R

R

R

22sin

22

• All kinematics is defined by recoil particle.

• For all RHIC beam energies recoil particle goes at 90o.

• Analyzing power small, but with weak energy dependence.

• Large cross section very good figure of merit.

• Need to collect 2-5107 events per measurement.

• Energy of the recoil particle is very small

target must be extremely thin.

Pure CNI Regge poles /Pomeron exchange

AANN is also sensitive probe to hadronic spin flip amplitude is also sensitive probe to hadronic spin flip amplitude


pC polarimeter setuppC polarimeter setup

Ultra thin Carbon ribbon Target(3.5g/cm2)

11

3344

55

66

22

Si strip detectorsSi strip detectors(TOF, E(TOF, ECC))

1515cmcm

1010mmmm

22mm pitch 12 stripsmm pitch 12 strips

pp++ implants implants~150 nm depth~150 nm depth

72 strips in total72 strips in total

Thin dead layer for low energy Thin dead layer for low energy carbon spectroscopy carbon spectroscopy

~100mV

BunchBunch

Ne

xt

Bu

nc

hN

ex

t B

un

ch

(60

bu

nc

h m

od

e)

(60

bu

nc

h m

od

e)

Shaped Si Signal

Ne

xt

Bu

nc

hN

ex

t B

un

ch

(12

0 b

un

ch

mo

de

)(1

20

bu

nc

h m

od

e)

Wave Form Digitizer (WFD)Wave Form Digitizer (WFD)420 Msamples/sec

- Pulse Height - Bunch ID- TOF - Integral (Q)- TMAX - revolution #

Select carbons at on-board LUTSelect carbons at on-board LUT Scaler dataScaler data Asymmetry calculationAsymmetry calculation Online results (to experiments)Online results (to experiments)

Event by event dataEvent by event data Stored in on-board memoryStored in on-board memory Used for offline detailed studyUsed for offline detailed study

offline

onlineN

o d

e ad

tim

e !


FPGA block diagram: V9FPGA block diagram: V9

ADC Virtex FPGA

140 MHz

Bunch 0

Level Trigger

BaselineSubtraction

BaselineCalculation

Bunch #, Rev. #

Amplitude

WaveformFIFO / Delay

CA

MA

C r

eado

ut

Time CFD, TMAX

1/4

ResultFIFO

Int/Ampl LUT

Scalers&histograms

MUX

Integral

Time/Ampl LUT

AND

:2

70 M

Hz

+1

SYNC andWindow Logic

Bunch # Distr.

Energy P+ Distr. Energy P– Distr.

Energy P0 Distr.Special Scalers:P+,P–,P0, BG

always accessible

Con

trol

Log

ic

INH2-dim T(E) Hist. OR

Ext INHBunch Polarization Pattern

Delim

3pt Filter

to Memory


FPGA algorithmsFPGA algorithms

baseline

AMAX/4

AMAX

tCFD

tMAX

Pipeline(for each bunch crossing)

• Baseline subtraction

• AMAX and tMAX

• Integral

• tCFD

• Use AMAX versus tCFD lookup table

• Fill internal histograms

• Move to memory FIFO

Baseline is averaged for about a dozen bunch crossings without signal.

No dead time processing and accepting events.Nearly 2·108 events can be stored in the onboard

memory for one measurement.


Improvements 2005Improvements 2005

New ceramic supports

USB 2.0 readout: up to 2 Mevents/second all measurements are done now in event mode all data are available for off-line analysis.

Independent BLUE and YELLOW DAQ hardware. Better WFD time and amplitude reconstruction.

New ceramic supports

USB 2.0 readout: up to 2 Mevents/second all measurements are done now in event mode all data are available for off-line analysis.

Independent BLUE and YELLOW DAQ hardware. Better WFD time and amplitude reconstruction.

Cer

amic

sup

port

Connector mount holes

GROUND ROW

Ground ring

Bondwires

NO BEAM CHARGE INDUCED SIGNAL !!!

(Up to 2·1011 p/bunch)

Top secret: every second line IS GROUND the whole way down to the very strip No pileup in the preamp Lower limit in –t is only by the detector noise No signal distortion No upper limit on –t


Recoil particle identification (2004)Recoil particle identification (2004)

Invariant Mass

MMCC ~ 11.17 GeV ~ 11.17 GeV

MM ~ 1.5 GeV ~ 1.5 GeV

carboncarbon

alphaalpha

promptsprompts

R

RT

TOFMv

T1

2

2

Plots by O. Jinnouchi


pC: shape is different !pC: shape is different !

ReRerr55=0, Im=0, Imrr55=0=0no hadron spin-flipno hadron spin-flip

p = 3.9 GeV/c

p = 6.5 GeV/c

p = 9.7 GeV/c

p = 21.7 GeV/c

AGS pr

elim

inar

yAN (

%)

recoil Carbon energy (keV)

100 GeV

24 GeV

100 GeV

RH

IC p

relim

inary

Fit with CNI theory function (hep-ph/0305085)

Crosses zero

Doesn’t cross zero

24 GeV

100 GeV

Plots by O. Jinnouchi

Plot by S. Bravar


Beam polarization profile (2005)Beam polarization profile (2005)

1mm

Plots by I. Nakagawa


Roadmap to absolute polarizationRoadmap to absolute polarization

A JET target polarization Ptarget (Breit-Rabi polarimeter) 2%.

B AN for elastic pp in CNI region: AN = - 1 / Ptarget N’.

C Pbeam = 1 / AN N”.

(B & C) can be combined in a single measurement:

Pbeam / Ptarget = - N’ / N” stat 4% in 2 weeks (one ring)

D CALIBRATION: ANpC for pC CNI polarimeter in covered kinematical

range: ANpC = 1 / Pbeam N”’.

(B & C & D) measured simultaneously with several insertions of carbon target stat(pC) 0% - very large statistics.


(ANpC) < 1-2% if jet is run continuously.

A JET target polarization Ptarget (Breit-Rabi polarimeter) 2%.

B AN for elastic pp in CNI region: AN = - 1 / Ptarget N’.

C Pbeam = 1 / AN N”.

(B & C) can be combined in a single measurement:

Pbeam / Ptarget = - N’ / N” stat 4% in 2 weeks (one ring)

D CALIBRATION: ANpC for pC CNI polarimeter in covered kinematical

range: ANpC = 1 / Pbeam N”’.

(B & C & D) measured simultaneously with several insertions of carbon target stat(pC) 0% - very large statistics.


(ANpC) < 1-2% if jet is run continuously.

%5arg

arg

pCpCN

N

ppett

ett

beam

beam

A

A

P

P

P

P

2% 4% 1-2% 0%

Documents

pC polarimeter at RHIC. Status and performance