Single Spin Transverse Asymmetries of Neutral Pions at Forward Rapidities in s62 GeV Polarized Proto

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Single Spin Transverse Asymmetries of Neutral
Pions at Forward Rapidities in ?s62 GeV
Polarized Proton Collisions at RHIC

• Mickey Chiu
• University of Illinois at Urbana-Champaign

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PHENIX Muon Piston Calorimeter Upgrade
Small cylindrical hole in Muon Magnet Piston,
Radius 22.5 cm and Depth 43.1 cm
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An Idea of Ken Imai and Yuji Goto in 1996!
http//www.phenix.bnl.gov/WWW/publish/goto/Polarim
etry/pol1.html

• Rediscovered recently by UIUC and ORNL group (M.
  Perdekamp, T. Awes, and MC)
• 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

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Present Future PHENIX Acceptance for
Calorimetry
EMCAL
0 f coverage 2p
EMCAL
-3 -2 -1
0 1 2
3 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
  (?gt3) is covered
• Along with Nose-Cone Calorimeter, it would give
  PHENIX very good calorimetry coverage.

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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

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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/APDs did not function
• Some problems with noisy electronics
• Cannot fix since they are in an inaccessible
  region of the detector
• Better than 80 of the acceptance is okay.

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South MPC Run06 MIP and ?0 Peak

• PbWO4 -dE/dx 13 MeV/cm ? MIP peak sits at 234
  MeV
• Along with ?0,? mass peak position, should allow
  us to set and confirm energy scale

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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 3.1lt?lt3.7 with (almost) full
  acceptance in phi.

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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.

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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 massgt0.01 masslt0.30 high energy

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MPC 62 GeV Transverse Raw Asymmetries
yellow
blue
yellow
blue

• asymmetry in yellow (xF)
• consistent with 0 in blue (-xF)
• increases with energy

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MPC 62 GeV Long. Raw Asymmetries
yellow
blue
yellow
blue
Asymmetry disappears in longitudinal
collisions. All analysis done exactly identically.
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North MPC

• Installation and start-up tuning is on-going this
  week and next
• Smaller beam-pipe in the north
• 220 crystals, larger acceptance (3.1lt?lt3.9)
• More uniform azimuthal coverage

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Summary and Status

• New electromagnetic calorimeter (MPC) has been
  installed into PHENIX for Run06 on a short time
  scale, giving coverage for ?0 at forward
  rapidities
• Very important to confirm results from other
  experiments
• Data Sets from Run06
• 200 GeV Transverse (0/pb) Very little useful
  data, due to late arrival of electronics
• 200 GeV Longitudinal (7.5/pb) forward ?0 ALL,
  di-hadron ALL
• 62 GeV Transverse (20/nb) Raw Asymmetries seen
  from 2-3 days data, commissioning as a local
  polarimeter
• 62 GeV Longitudinal (80/nb) Unique data set at
  RHIC.
• Currently installing North MPC, with slightly
  larger acceptance, and with lessons from the
  South, to be ready for the beginning of Run07
  (cooldown on Dec. 1).

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