Jan Balewski, MIT FGT Project Review January 7-8, 2008 Detector requirements Disk layout e+/e- separation e/h discrimination Simu GEM response Strip layout, occupancy To-do- list Summary  FGT disks  =1.0  =1.5  =2.0 FGT Layout Simulation Results e+ shower E T =40 GeV

FGT Layout and Simulations Jan Balewski, MIT 2 FGT Requirements 1. Reconstruct charge of e+, e- from W decay for P T up to 40 GeV/c 2. Discriminate electrons against hadrons Allow for uniform performance for z-vertex spread over [-30,+30] cm Fit in geometrical space free up by the West Forward TPC (FTPC) Benefit from limited coverage of other trackers: IST, SSD Relay on vertex reconstruction and Endcap shower-max hit Relay on Endcap towers for energy reconstruction Minimize amount of material on the path of tracks Align FGT segmentation with TPC sector boundaries and Endcap halves Assure relative alignment vs. TPC is double with real particles

FGT Layout and Simulations Jan Balewski, MIT 3 Optimization of FGT Disks Location in Z Used TPC volume nHits>=5 SSD  IST1,2  beam  Z vertex =+30cm Z vertex =0cm  R-‘unconstrained’ FGT disks a) b) c) Z vertex =-30cm  =1.0  =1.5  =2.0 Endcap EMC Barrel EMC 5 hits required for helix reco FGT sustains tracking if TPC provides below 5 hits use TPC, SSD,IST for Z vertex <~0 and  <~1.3 allow Z vertex  [-30,+30]cm FGT disks geometry: Rin=7.5cm, Rout=41cm, Z1…Z6=60…150cm,  Z=18cm

FGT Layout and Simulations Jan Balewski, MIT 4 Optimization of FGT Disk Radii (Z Vertex = 0 cm ) Rxy – Z representation TPC If nHit>5 Endcap  SMD IST1,2  SSD FGT  vertex  =1.7  Rxy –  representation Used TPC volume nHits>=5  =1.0  =1.5  =2.0 Endcap Z ver =0cm  FGT track  = 1.7  Optimization Criteria Each track must cross the vertex and Endcap EMC 6 FGT disk are needed to provide enough hits for tracks at all  and all z-vertex Single track crosses less than 6 FGT disks

FGT Layout and Simulations Jan Balewski, MIT 5 Optimization of FGT Disk Radii (& location) TPC If nHit>5 Endcap  SMD IST1,2  SSD FGT  vertex a) Z Vertex = - 30 cmb) Z Vertex = 0 cmc) Z Vertex = + 30 cm R-’unconstrained’ FGT disks fitting in available R-space Critical FGT coverage depends on Z-vertex FGT disks geometry: Rin=7.5cm, Rout=41cm, Z1…Z6=60…150cm,  Z=18cm

FGT Layout and Simulations Jan Balewski, MIT 6 1  of reco track  FGT Enables Reco of Sign of e+,e- 2mm Sagitta (mm) 100cm Y/cm 40cm 20cm X/mm 1.0 Vertex  =200  m Endcap SMD hit  =1.5mm reco track  Limit for   p T track 3 FGT hits  =70  m 0 Sagitta (mm) 2mm 2.0 mm Sagitta=2mm Wrong Q-signGood Q-sign

FGT Layout and Simulations Jan Balewski, MIT 7 Track & Charge Sign Reco Efficiency FGT disks geometry: Rin=7.5cm, Rout=41cm, Z1…Z6=60…150cm,  Z=18cm N0 – thrown electrons, E T =30 GeV N1 – reco tracks (  <3 mrad) N2 – reco tracks w/ correct charge sign Track reco efficiency >80% for  up to 2.0 Wrong charge reco <20% for  above 1.5

FGT Layout and Simulations Jan Balewski, MIT 8 Zvert=0 Stability of Charge Reconstruction Studied variations of efficiency (shown in proposal): - degraded FGT cluster resolution (80  m  120  m, OK) - reduced # of FGT planes (6  4, bad, too few hits/track) - degraded transverse vertex accuracy (200  m  500  m, OK) - FGT cluster finding efficiency (100%  90%, OK, details)details - smaller FGT disk size & separation - OK Rin=18cm, Rout=37.6cm, Z1…Z6=70…120cm,  Z=10cm

FGT Layout and Simulations Jan Balewski, MIT 9 GeV  e/h Discrimination Capability of Endcap EMC Projective tower Pre Showers Post Shower Max Shower from electron E=30 GeV   =2.0  =1.08 Simu of Endcap response to Electrons (black) & charge pions (red) with E T of 30 GeV Endcap ++ e+ 30 GeV 0 ++ e+ GeV  ++ e+ ~15 GeV E T Trigger threshold

FGT Layout and Simulations Jan Balewski, MIT 10 e/h Discrimination : PYTHIA Events Hadrons from PYTHIA M-C QCD events e+, e- from PYTHIA M-C W-events Isolation & missing-PT cuts suppress hadrons by ~100

FGT Layout and Simulations Jan Balewski, MIT 11 Real Electrons Reconstructed in Endcap  e+, e-  MIP TPC P  [6,8] GeV/c  e+, e-  MIP TPC P  [10,14] GeV/c Endcap-based cuts Identified e+,e-

FGT Layout and Simulations Jan Balewski, MIT 12 Detailed Simulation of GEM Response (1) 1.ionization and charge amplification 2. spatial quantization on GEM grid 3. charge collection by strip planes 4. 1D cluster reconstruction Primary ionization Amplified signal is displaced Hole in GEM foil amplifies charge cloud phi-axis strip pitch=600  m R-axis strip Pitch=800  m x  hit Latice attractors spaced 130  m Charge from this hexagon is attracted by the hole best

FGT Layout and Simulations Jan Balewski, MIT 13 Simulated FGT Response (2) 22 eV/pair (760 eV/ track) 14 prim pairs/track 32 any pairs/track 22 eV/pair 14 prim pairs/track  R=122  m R*  =40  m GEM response 1D Cluster finder resolution Test beam data

FGT Layout and Simulations Jan Balewski, MIT 14 FGT Strip Layout *) 326 R-strips Top  -layer 949  -strips pitch 600  m x y X z 15 deg Endcap halves y x *) close to final  Essential for P T reco ~ 50% transparency  needed for 3D track recognition, resolving ambiguities FGT quadrant boundaries match to Endcap segmentation Bottom R-layer pitch 800  m

FGT Layout and Simulations Jan Balewski, MIT 15 Estimation of Strip Occupancy Track rate per strip for minB PYTHIA  s500 GeV Based on FGT geometry:Rin=15cm, Rout=41cm R-strips 45 deg long tracks R=41cm R=15cm  =0 deg  =90  1 track/strip per 1000 minB events tracks  -strips 400  m pitch pileup from minB events dominates 1.5 minB interactions/RHIC bXing 300nsec response of APV  3 bXings pile up  Total pileup of 5 minB events per trigger event 1 tracks per FGT quadrant per minB event (scaled from simu below) Cluster size: 1mm along , 2mm along R Cluster occupancy per triggered event per quadrant  -strips (span ~43cm)  1.2% occupancy R-strips (span 25cm)  4% occupancy (uncertainty factor of 2) minB PYTHIA  s=500 GeV

FGT Layout and Simulations Jan Balewski, MIT 16 To-do List completion of detailed (a.k.a. ‘slow’) simulator for GEM response develop 3D tracking with pattern recognition include pileup from 3 events in reco of physics events implement and optimize full array of e/h discrimination techniques completion of full W event simulation and comparison to full hadronic QCD events simulation determine background contribution from Z 0 and heavy flavor processes, above p T >20 GeV/c

FGT Layout and Simulations Jan Balewski, MIT 17 FGT Simulation Summary 1. Will be able to reconstruct charge of e+, e- from W decay for P T up to 40 GeV/c with efficiency above 80% 2. There is enough information recorded to discriminate electrons against hadrons Allow for uniform performance for z-vertex spread over [-30,+30] cm , OK Will fit in geometrical space Will use hits from IST, SSD Will relay on vertex reconstruction and Endcap shower-max hit & energy FGT quadrants are aligned with TPC sector boundaries and Endcap halves FGT disks 1 &2 overlap with TPC allowing relative calibration

FGT Layout and Simulations Jan Balewski, MIT 18 BACKUP

FGT Layout and Simulations Jan Balewski, MIT 19 Compact FGT- proof of principle Critical FGT coverage depends on Z-vertex Rin=18cm, Rout=37.6cm, Z1=70cm, …,Z6=120cm,  Z=10 cm

FGT Layout and Simulations Jan Balewski, MIT 20 FGT Material budget UPGR13, maxR=45 cm Z vert= - 30cm Z vert= 0cmZ vert= + 30cm

FGT Layout and Simulations Jan Balewski, MIT 21 FGT Material UPGR13 w/o SSD

FGT Layout and Simulations Jan Balewski, MIT 22 TPC reco with 5 points ‘regular’ tracking 5-hits tracking ‘regular’ tracking 5-hits tracking

FGT Layout and Simulations Jan Balewski, MIT 23 Alternative Snow-flake Strip Layout As in Proposal   12-fold local Cartesian ref frame

FGT Layout and Simulations Jan Balewski, MIT 24 Track Reco Strategy 1.Select EMC cluster with large energy 2.Eliminate all FGT hits outside the cone: vertex  SMD hit 3.Resolve remaining ambiguities comparing R vs.  charge 4.Consider shorter  -strips (snow flake design)  FGT