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

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 p.e./MeV @ 25 C Temp. Coefficient -2% / C Radiation Hardness 1000 Gy Main Emission Lines 420-440, 500 nm Refractive Index 2.16 SOUTH Small cylindrical hole in Muon Magnet Piston, Radius 22.5 cm and Depth 43.1 cm

An Old (1996) Idea of Ken Imai and Yuji Goto http://www.phenix.bnl.gov/WWW/publish/goto/Polarimetry/pol1.html 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

Present & Future PHENIX Acceptance for Calorimetry MPC NCC 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 (>3) is covered *for NCC details, see R. Seto’s talk tomorrow in this workshop

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

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.

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…

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.

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.

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”

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

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

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

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).

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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