The Electromagnetic Calorimeter – 2005 Operation J. Sowinski for the Collaboration and the Builders Indiana Univ. Michigan State Univ. ANL MIT BNL Penn. State Univ. JINR Rice Univ. Kent State Univ. Texas A&M Univ. Valparaiso Univ. Funded by NSF STAR

 P  x P  x a LL gpart LL ^ pQCD Measure Know from DIS “  G” DG via partonic scattering from a gluon Dominant reaction mechanism Experimentally clean reaction mechanism Large a Prefer LL ^ STAR Hard scattering pQCD, factorization Heavy flavor rare g-jet coinc. rare Jets and p 0 s 

The STAR Detector at RHIC At the heart of STAR is the world’s largest Time Projection Chamber STAR STAR Detector Large solid angle Not hermetic Tracking in 5kG field EM Calorimetry “Slow” DAQ (100Hz) Sophisiticated triggers

Detector  =0 Forward Pion Detector Endcap EM Calorimeter Beam-Beam Counters Time Projection Chamber -2<η< 2 Barrel EM Calorimeter -1<η< 1 1<η< <η< <|η|< 5 Solenoidal Magnetic Field 5kG  =2  = -1 Tracking Lum. Monitor Local Polarim Triggering h = - ln(tan(q/2) STAR

Barrel EMC Endcap EMC Star poletipStar magnet TPC EM Calorimeters in STAR

Endcap ElectroMagnetic Calorimeter Pb Scint sampling calorimeter 21 radiation lengths 720 projective towers Depth Segmentation –2 preshower layers, e/h  0 /  disc. –High position resol. SMD  0 /  disc. –Postshower layer e/h discc. L0 trigger- high tower, jet patches Simulated EM Shower

Shower Maximum Detector EEMC Resolves closely spaced showers for  –  ID ~7000 individually read out scintillating strips U and V plane in each 30 o sector Essentially no coverage gaps SMD profiles for a 9 GeV  0 candidate UV 8 cm7 cm

Tower Energy signal PMT Box MAPMT Boxes PMTs and electronics on back of poletip 16 ch MAPMT and miniturized electronics For SMDs and Pre/Post Shower Detector Readout and Trigger Light carried out of magnet on fiber optics Photomultiplier tubes for all signals Digitized every beam crossing (110 ns) Stored in pipeline for transfer on trigger Tower energy can generate level 0 trigger –Highest tower –Total energy –Jet patch (1/6 th in f) summed energy –Coincidences between jet patches and other detectors

Highest tower ADC by patch Highest Tower trigger Thr =2.4 GeV prescale 6 Thr =2.9 GeV no prescale Jet Patch trigger Summed E in1/6 th of f Thr = 3.8 GeV STAR

MIP coincidence between all subsystems Coincidence between 2 SMD planes Hit pattern xx each plane Calibration and status from Minimum Ionizing Particles Internally defined as MIP behavior in all 4 subsystems 10% calib. of Tower Energy – 20% of other elements All but a handful of channels out of 9360 working Tower Gains from MIPs

p 0 s in the EEMC Cluster finding algorithm Consider SMD strips in hit towers Cluster around highest strip above 8 MeV threshold Include 5 strips either side Cluster around next highest strip above threshold + estimated tail of found clusters Find all clusters Pair up between U and V considering geometry of sector Requires 2 clusters in each SMD p T ~3-6 GeV Construct few % p 0 s in HT triggers (thr>2.9 Gev) At low p T trigger favors asymmetric decay Cluster finding favors symmetric decay 2005 data enough stats to continue developing higher p T algorithms Initial attempts to understand spectrum shape

Jets found with Endcap HT trigger Jets h jet Df Endcap Calo Away side jets in TPC + Calo’s Need to develop better tracking in forward region Df = f jet – f HT STAR

Summary One year with full coverage Two years of operation with full system First large pp data set (6/05) being processed >99% of elements working Continued work on – p 0 finding – Tracking in forward region - Jets – direct g finding – e/h discrimination

Clustering Algorithm Typical cases for 15 GeV p 0

Detector  =0 Forward Pion Detector Endcap EM Calorimeter Beam-Beam Counters Time Projection Chamber -2<η< 2 Barrel EM Calorimeter -1<η< 1 1<η< <η< <|η|< 5 Solenoidal Magnetic Field 5kG  =2  = -1 Tracking Lum. Monitor Local Polarim Triggering h = - ln(tan(q/2) STAR