Slajd 1

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FPD
N. Poljak, U. of Zagreb
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Layout
TPC -1.0 lt ? lt 1.0 FTPC 2.8 lt ??? lt 3.8 BBC
2.2 lt ??? lt 5.0 EEMC1 lt ? lt 2 BEMC-1 lt ? lt
1 FPD ? 4.0 3.7
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pQCD Physics results

• Unlike at lower energies, the inclusive
  differential cross section for pion production at
  200 GeV is consistent with NLO pQCD calculations
  at 3.3lt? lt4.0
• As ? increases, systematics regarding the
  comparison with NLO pQCD calculations begin to
  emerge. The data at low pT are more consistent
  with the Kretzer set of fragmentation functions.

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AN results
AN grows with increasing xF for values larger
then 0.35 Results from run2 dont yet
discriminate between different dynamics First
result for the AN(pT) was obtained using combined
statistics from run3 and run5. There is evidence
that the p0 analyzing power at xF gt0.4 decreases
with increasing pT
J. Adams et al. (STAR), Phys. Rev. Lett. 92
(2004) 171801
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Run 2 Published Result.
Run 3 Preliminary Result. -More Forward
angles. -FPD Detectors.
Run 3 Preliminary Backward Angle Data. -No
significant Asymmetry seen. ( Presented
at Spin 2004 hep-ex/0502040)
Run 3 Run 5 Preliminary lt?gt3.7,4.0 (Presented
SPIN 2005 Dubna Sept 27-Oct 1, Absolute
polarization still preliminary)
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FPD Physics for Run6
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Basic physics GoalsIdeas to be tested using
FPD in Run6

• Prototype for FMS (RUN7)
• Discriminate dynamical origin of the forward AN
• Measurement of jetlike events and AN for those
• Similar to FPD (left, right) but with larger
  active area
• Measure shape of forward jet
• Measure direct photons cross section, possibly AN
  --- separation of p0 and direct gamma
• Continue the study of p0 asymmetry in pp
• other

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Jet spin asymmetry

• Is the single spin asymmetry observed for p0
  also present for the jet the p0 comes from?
• Answer discriminates between Sivers and Collins
  contributions
• Trigger on energy in small cells, reconstruct p0
  and measure the energy in the entire FPD
• Average over the Collins angle and define a new
  xF for the event, then see if analyzing power
  increases with xF

Expect that jet-like events are 15 of p0 events
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Where do decay partners go?
di-photon parameters zgg E1-E2/(E1E2) fgg
opening angle Mm 0.135 GeV/c2 (p0) Mm0.548
GeV/c2 (h)

• Gain sensitivity to direct photons by making
  sure we have high probability to catch decay
  partners
• This means we need dynamic range, because
  photon energies get low (0.25 GeV), and
  sufficient area (typical opening angles few
  degrees at our h ranges).

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Sample decays on FPD
The FPD is much closer to FPD then FMS will be.
We can mimic the FPD trigger and search for the
second p0 around the first With FPD module
size and electronic dynamic range, the yellow
area marks where we have 95 probability of
detecting second photon from p0 decay
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Status report

• Calorimeter cells for free thanks to FNAL /
  U.Col. and Protvino
• Cells were refurbished and tested in physics
• South enclosure in place on STAR west platform,
  readout in place
• cell by cell IN SITU tests and cables connected

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To do list
RUN 6
RUN 7
Put the north module in place Conect the readout
electronics and test all readout Finalize the
readout and trigger details Perform measurements
with 15/pb delivered integrated luminosity (for
4-5 ? measurement of AN in jet like events)
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BACKUP SLIDES
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FMS . To be installed for RUN7

• Expanding the eta coverage -1lt?lt4
• Measurement of the same side correlations
• Opposite side correlated pions (dijets)
• Sivers effect
• d-Au (Gluon saturation in Nuclei)
• Other future objectives
• Forward Lepton pairs
• Charm
• Drell Yan

Planned FMS Wall
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• Reconstruction
• FPD (Forward Pion Detector) proved we can
  reconstruct forward p0 in all (pp, dAu, CuCu)
  environments

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Separated xF and pT dependence
Shows the data consistency
Similar to ISR analysis J. Singh, et al Nucl.
Phys. B140 (1978) 189.
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AN(pT) in run3run5 at vs200 GeV

• Combined statistics from run3 and run5 allowed to
  distinguish nonzero effect in AN(pT) plot
• There is an evidence that analyzing power at
  xFgt0.4 decreases with increasing pT
• Theoretical predictions needed (for constraint
  on Sivers function).

Online calibration of CNI polarimeter
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How to detect direct photons?

• We have good sensitivity to both photons in decay
  of known particles, so that unpaired photons
  become candidates for being direct.
• p0??? M0.135 GeV BR98.8
• K0 ? p0p0 ??? ?? 0.497 31
• ?? ?? 0.547 39
• ?? p0 ? ??? ? 0.782 8.9
• ?? ?? 0.958 2.1
• Other decay modes yield more photons with less Q
• Background simulations underway

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Proposed readout