1. Mickey Chiu University of Illinois at Urbana-Champaign
Single Spin Transverse Asymmetries of Neutral Pions at Forward Rapidities in s=62 GeV Polarized Proton Collisions at RHIC
Mickey Chiu
University of Illinois at Urbana-Champaign

2. MPC, or, What else can we stick in PHENIX?
Density
8.28 g/cm3
Size
2.2x2.2x18 cm3
Length
20 X0, 0.92 
Weight
721.3 g
Moliere radius
2.0 cm
Radiation Length
0.89 cm
Interaction Length
22.4 cm
Light Yield
~10 25 C
Temp. Coefficient
-2% / C
Radiation Hardness
1000 Gy
Main Emission Lines
, 500 nm
Refractive Index
2.16
SOUTH
Small cylindrical hole in Muon Magnet Piston, Radius 22.5 cm and Depth 43.1 cm

3. An Old (1996) Idea of Ken Imai and Yuji Goto
Rediscovered recently by UIUC and ORNL group (M. Perdekamp, T. Awes, and M. Chiu)
Many hurdles, but main one was satisfying the muon tracker group that the new detector would not increase the backgrounds significantly in the tracker.
Elegant solution chosen in which PHENIX leveraged expertise, design, and equipment from Kurchatov and Hiroshima collaborators on PHENIX and PHOS (Alice)
Implementation possible on a very fast time-scale

4. Present & Future PHENIX Acceptance for Calorimetry
MPC
NCC
EMCAL
f coverage p
EMCAL
rapidity
Addition of MPC increases PHENIX acceptance for calorimetry by a factor of 4 (with a detector more than 10 times smaller)
Especially important that the very forward region (>3) is covered
*for NCC details, see R. Seto’s talk tomorrow in this workshop

5. FermiLab Test Beam Results
FNAL Meson Test Beam Facility
FNAL MTBF: Secondary beam with electron/hadron identification
Energy Resolution is at worst 14%/E
Analysis is ongoing…
Improved Calibrations, Shower Shape extraction

6. January 2006 MPC South Installation
May 11, 1st 0 peak
Muon Piston Calorimeter (MPC) Run06 Summary
Only South Side Installed, 192 PbWO4 crystals with APD readout
About 12 crystals did not function
Some problems with noisy crystals and electronics
Cannot fix since they are in an inaccessible region of the detector
Better than 80% of the acceptance is good.

7. South MPC Run06 MIP and 0 Peak
MIP Peak
PWO -dE/dx = 13 MeV/cm  MIP peak sits at 234 MeV
Should allow us to set the energy scale, along with the 0,eta mass peak position
Analysis is on-going…

8. South MPC Acceptance
=3.7
=3.1
Generated 10K single photons of 10 GeV at South MPC, flat in phi and theta in PISA to look at the response.
Coverage is from 3.1<<3.7 with (almost) full acceptance in phi.

9. Fwd 0 xF distribution, Run06 62 GeV
PYTHIA based study, 0.02/pb
62.4 GeV
At 200 GeV, PYTHIA gives same cross-section as that measured by STAR
At 62 this is not yet known if PYTHIA also matches the forward 0 cross-section
This assumes a perfect detector, which the MPC is not (Run06 was commissioning run)
Acceptance includes smearing effect from z-vertex dist, and 30 cm cut, but not detector noisy/dead areas, or reconstruction efficiencies.

10. MPC Left-Right Transverse Asymmetry
yellow
blue
Asymmetry seen in yellow beam (positive xF), but not in blue (negative xF)
Only 10% of total statistics from 62 GeV Transverse Run
Simple 3x3 tower sum clustering, with no overlap shower splitting
Cuts: mass>0.01 && mass<0.30 && high “energy”

11. MPC 62 GeV Transverse Raw Asymmetries
yellow
blue
yellow
blue
asymmetry only in yellow

12. MPC 62 GeV Long. Raw Asymmetries
yellow
blue
yellow
blue
asymmetry disappears in longitudinal collisions.

13. North MPC Installation and checking is on-going this week and next
Smaller beam-pipe in the north
220 crystals, larger acceptance (3.1<<3.8)
Better azimuthal coverage

14. Summary and Status
New electromagnetic calorimeter (MPC) has been installed into PHENIX for Run06, giving coverage for 0 at forward rapidities
Data Sets from Run06
200 GeV Transverse (~0) – very little useful data, due to late electronics
200 GeV Longitudinal (7.5/pb) – Analysis is ongoing…
62 GeV Transverse (20/nb) – Raw Asymmetries seen from 2-3 days data, Analysis is ongoing…
62 GeV Longitudinal (80/nb) – Analysis is ongoing…
Currently working on installation of North MPC, with slightly larger acceptance, and with the lessons from the South, to be ready for the beginning of Run07 (starting whenever).

15. Backup

16. MPC Raw Asymmetry 62 GeV Transverse 62 GeV Longitudinal
Qualitative Behavior 100% consistent with physics asymmetry
Only yellow beam (+xF) has asymmetry
Asymmetry disappears in Longitudinal Mode
All for same cuts, same analysis method, etc.
Not divided by polarization
Also not bkg subtracted, so asymmetry could be bigger
eta is between 3.1 and 3.7