31 July 2005HjC at STAR in Warsaw Forward Meson Spectrometer (FMS) status report Hank Crawford for FMS group L.Bland, F.S.Bieser, R.Brown, A.A.Derevschikov, J.Drachenberg, C.Eskew, C.Gagliardi, S.Heppelmann, J.Engelage, L.Eun, E.Judd, V.I.Kravtsov, Yu.A.Matulenko, A.P.Meschanin, D.A.Morozov, M.Ng, L.V.Nogach, S.B.Nurushev, A.Ogawa, J.Passaneau, C.Perkins, G.Rakness, J.Rothenberg, K.R.Shestermanov, M.Tatarowicz, A.V.Vasiliev, M.Zucker

31 July 2005HjC at STAR in Warsaw Overview STAR Forward   Detector (FPD) proved we can reconstruct forward   in pp, dAu, and CuCu environments

31 July 2005HjC at STAR in Warsaw Overview (2) Spin Physics Results Discovered π 0 asymmetry in p  p Proved NLO pQCD works in forward region at RHIC J. Adams et al. (STAR), Phys. Rev. Lett. 92 (2004)

31 July 2005HjC at STAR in Warsaw Overview (3) Probing the gluon density in the Au nucleus Showed suppression of forward π 0 in dAu G. Rakness, for STAR [hep-ex/ ]

31 July 2005HjC at STAR in Warsaw Overview (4) FPD++ and Forward Meson Spectrometer (FMS) FMS proposed to enlarge acceptance for gluon distribution studies Stage FPD++ for Run6 as FMS engineering run Stage full FMS for Run7 dAu

31 July 2005HjC at STAR in Warsaw FMS Physics Goals These we know we can do from FPD analysis of π 0 1. Measure gluon distributions xg(x) in protons and gold nuclei from 0.001<x b <0.1 Check universality of xg(x) in region of overlap with DIS (0.02<x b <0.1) 2. Characterize correlated pion distributions as a function of Q 2 to search for onset of saturation effects Is Au a Color Glass Condensate (CGC)? 3. Resolve the origin of large transverse spin asymmetries in p  +p ->  0 +x for forward  0 production

31 July 2005HjC at STAR in Warsaw Expanded FMS Physics Goals We intend to test these ideas using an FPD++ in Run6 4. Measure g(x) using direct photons Is known asymmetry in pp  π 0 present in pp   ? Much simpler probe because no final-state effects 5. Measure J/  (with small acceptance) Simulations underway

31 July 2005HjC at STAR in Warsaw How do we measure g(x)? Quark from Blue beam scatters off gluon in Yellow beam to produce π 0 or  in forward direction (2.8<  <4.2) We measure E, , and  for π 0 or  in coincidence with π 0,  or leading hadron jet surrogate from BEMC, EEMC, or accompanying  (s) within FMS to cover 0.001< x <0.1

31 July 2005HjC at STAR in Warsaw How do we tell if there is a CGC?  ln( 1/x) and the scale (Q) is taken as p T Require two   (jets) in FMS  probes smallest x gluons in Au nucleus (largest  ) Look for broadening or disappearance of  peak as p T decreases p T decreasing

31 July 2005HjC at STAR in Warsaw Run-5 FPD Run-6 FPD++ Run-7 FMS FPD++ Physics for Run6 We intend to stage a large version of the FPD to prove our ability to detect direct photons. These give a cleaner signal of the underlying qg interaction because they are free of final state interactions.

31 July 2005HjC at STAR in Warsaw How do we detect direct photons? Isolate photons by having sensitivity to partner in decay of known particles: π 0  M=0.135 GeV BR=98.8% K 0  π 0 π 0   %   %  π 0    %  ’   % Other decay modes yield more photons with less Q Background simulations underway

31 July 2005HjC at STAR in Warsaw Where do decay partners go? 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  ranges). m =    di-photon parameters z  = |E 1 -E 2 |/(E 1 +E 2 )   = opening angle M m = GeV/c 2 (   ) M m =0.548 GeV/c 2 (  )

31 July 2005HjC at STAR in Warsaw Sample decays on FPD++ With FPD++ module size and electronic dynamic range, have >95% probability of detecting second photon from   decay.

31 July 2005HjC at STAR in Warsaw On to the Full FMS Following Run6 we will have shown direct photon capability which will only improve with larger detector. We will have proven electronics and trigger schemes and may well have shown J/  capability, which will also only improve with acceptance of FMS

31 July 2005HjC at STAR in Warsaw STAR detector layout with FMS TPC: -1.0 <  < 1.0 FTPC: 2.8 <  < 3.8 BBC : 2.2 <  < 5.0 EEMC:1 <  < 2 BEMC:-1 <  < 1 FPD: |  | ~ 4.0 & ~3.7 FMS: 2.5<  < 4.0

31 July 2005HjC at STAR in Warsaw Calorimeter cells - all for free Thanks to FNAL (U.Col) and Protvino 800 cells (5.8x5.8x60 cm 3 : 25 L rad ) of lead glass (PbGl) from E831 at FNAL including PMTs (XP2202) with active bases Arrived at BNL in June. Students from PSU, UCB, and TAMU working to refurbish, test, and characterize in bldg 510 rm cells (3.8x3.8x45 cm 3 : 25 L rad ) of PbGl from IHEP Protvino including PMTs (FEU-84) needing bases 150 on site and used in FPD West. 500 more expected to arrive at BNL in September These are fully understood in terms of response

31 July 2005HjC at STAR in Warsaw FNAL E831Cells head to BNL

31 July 2005HjC at STAR in Warsaw Students prepare cells at test Lab at BNL

31 July 2005HjC at STAR in Warsaw FPD++ and FMS Timeline

31 July 2005HjC at STAR in Warsaw Electronics New digitizer boards - 32 channels in 9U VME 12 bit ADC pC sensitivity 5 bit TAC - 5 ns sensitivity 10 MHz operation - fully pipelined bit selection for L0 triggering (sum, HT, ID, other?)) Use existing FPDW DSM tree

31 July 2005HjC at STAR in Warsaw Conclusions We have shown we can do π 0 reconstruction in the FPD for CuCu and pp and discovered large spin asymmetry at large  in polarized pp where the cross section is explained by NLO pQCD. We have observed suppression of forward π 0 in dAu We intend to use the FPD++ arrays to show that we can measure direct  signal and to continue the study of asymmetry in p  p Run6 will allow engineering test of “new” calorimeter cells and of the new 12 bit digitizer boards We will work with BNL management to produce the full electronics set for the FMS and stage it for Run7 measurements of the gluon distribution in protons and Au nuclei covering 0.001<x<0.1, checking the universality of the pdf’s determined through DIS

31 July 2005HjC at STAR in Warsaw Sivers Geometry

31 July 2005HjC at STAR in Warsaw FMS Inner cells are 3.8 cm edge, outer are 5.8 cm Showing FPD N,S,T,B for size scale Circles indicate  range of detector