Title: A CNI Polarimeter for RHIC Spin Results from IUCF CE75
1A CNI Polarimeter for RHIC Spin Results from IUCF
CE75 AGS E950
- M. Bai, G. Bunce, H. Huang, Y. Makdisi, T.
Roser, A. Rusek, M. Syphers - Brookhaven National Laboratory
- K. Imai , M. Nakamura, J. Tojo, K. Yamamoto, L.
Zhu - Kyoto University/ RIKEN
- B. Bassalleck, S. Eilerts, D.E. Fields , B.
Lewis, B. Smith, T.L. Thomas - University of New Mexico
- Y. Goto, M. Ishihara, K. Kurita, N. Saito, A.
Taketani - RIKEN
- D. Underwood
- Argonne National Laboratory
- J. Doskow, K. Kwiatkowski, B. Lozowski, H.O.
Meyer, B. v. Przewoski, T. Rinckel - Indiana University Cyclotron Facility
- I. Alekseev, D. Svirida, V.Kanavets
- ITEP
- A. Deshpande, V. Hughes
- Yale University
- RIKEN/BNL Research Center
2A CNI Polarimeter for RHIC Spin Results from IUCF
CE75 AGS E950
- Motivation for CNI Polarimeter
- CNI Theoretical Status
- Initial tests - IUCF CE75 and Kyoto tests
- AGS E950 Experimental Setup
- E950 Analysis
- E950 Results
- RHIC Polarimeter Preliminary Design
3Motivation
- RHIC schedule
- First Year running Oct.99 - Aug. 00
- Siberian Snakes installed
- Spin Rotators not installed yet
- Commissioning only, No Spin Physics
- Second Year running Oct. 00 - Aug. 01
- Spin rotators installed
- Higher (Blue Book) Luminosity
- Good Physics (DG)
- BUT Need relative polarimeter for First Year
commissioning !
4Motivationp C CNI polarimeter
- Pros
- Inexpensive setup
- Solid target
- High figure of merit
- Little energy dependence
- Polarization profile
- Cons
- Difficult Carbon recoil detection
- Not absolute
5TheorypC Coulomb Nuclear Interference
- CNI is an interference effect between the purely
Coulombic spin-flip term and the hadronic non
spin-flip term in the scattering potential. - For the interference term to be important, the
scattering must take place outside of the
nucleus (rgtgtR), but well within the screening
radius of the atomic electrons (rltltao).
6Theory
- CNI analyzing power is given by
- so no direct energy dependence.
- At 25 - 250 GeV, Hadronic AN is thought to be
lt10 of - the CNI AN .
7Theory
p
k
qp-k
pp
12C
pC
t -q2
E950
900keV
450keV
8Measurementspp elastic at 200GeV/c
(E704)Physical Review D48 (1993) 3026-3036.
Curve has no hadronic spin flip.
9Initial tests - IUCF CE75
10CE75 Silicon
- Two standard Silicon detectors around 90o.
- Off-the-shelf on-board pre-amps.
- Cooled FETs and silicons.
11IUCF CE75 Results
- Red points are for detector closer to 90o.
- So, green points (more forward detector) have
higher Carbon energy. - Matches predicted angle vs. energy.
- 200KeV threshold.
12Silicon Detector Re-design
- 12 Channel 6 channel.
- On-board pre-amps.
- Cooled by mount.
Silicon Detector
Pre-amp location
13Initial tests - Kyoto
14Kyoto Results
- Could resolve down to 200keV Carbon recoils.
15AGS E950 Experimental Setup
16AGS E950 Experimental Setup
TOF measurement
Micro ribbon Carbon target
MCP
MCP
e
e
C
Silicon strip detector
Carbon foil
0
13
25 cm
Energy measurement
17Targets
- Carbon Ribbons
- 6mm wide
- 3.7mg/cm2 thick
- 3cm long
18Micro-Channel-Plate Detectors
Si PC board
Silicon
MCP
Repeller
e-
12C
Mirror
MCP
Accelerator
C foil
Mirror
19Data Acquisition
- Read out events at end of spill.
- Home made Linux based acquisition.
- On-line analysis capable.
20E950 On-line Analysis
- Target out configuration still had a frame.
- Rate was sensitive to beam position.
Target Out
Target In
Carbon
TDC distribution
ADC distribution
21E950 Analysis
- Bunch width was 25ns.
- TDC start was beam RF.
- Inherent 7.2ns width from beam bunches.
- Using Si - MCP gives inherent Si time resolution
of 2.5ns .
Si only
Si -MCP
s2.5ns
s7.5ns
Projection along the profile
22E950 Analysis
- Since E calibration not good (yet), use time
slices to get -t bins.
Carbon band
4 sigma cut
TDC Values (ns)
6 time bins
prompt
ADC values(ch)
23E950 Results
-t
- Follows general trend expected.
- Not yet absolute (at any scale).
E950 Preliminary
Asymmetry
Error bars are statistical only
Time bins
24RHIC Polarimeter Preliminary Design
25RHIC Polarimeter Preliminary Design