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Enhancing Electromagnetic Object Detection via L1 and L2 Triggers in Particle Physics

This work details the design and implementation of Level 1 (L1) and Level 2 (L2) trigger systems for detecting electromagnetic objects, such as electrons and photons, in high-energy particle collisions. With a peak instantaneous luminosity of 2 x 10^32 cm^-2 s^-1 and approximately 2 fb^-1 of accumulated data, our algorithms target both high and low transverse momentum events, optimizing efficiency and minimizing background noise. We explore innovative approaches to clustering and event selection, addressing key challenges in high-rate data environments.

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Enhancing Electromagnetic Object Detection via L1 and L2 Triggers in Particle Physics

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  1. Triggering on Electromagnetic Objects • (e/) • at L1 & L2 • Mrinmoy Bhattacharjee • SUNY, Stony Brook • D0 EM ID Vertical Review • Thanks to: • Arnaud Lucotte, Kin Yip, Paul Grannis, • Manuel Martin, Levan Babukhadia, • Marc Buehler, Dave Toback, Dylan Casey

  2. Overview • Motivation • D0 Trigger system (L1 & L2) • L1 EM Trigger: • Detector information at L1 • High pT EM trigger & low pT di-electrons •  Algorithm • * Timing •  Efficiencies & Rates • L2 EM Trigger: • Detector information at L2 • High pT EM trigger & low pT di-electrons •  Algorithm • * Timing •  Efficiencies & Rates • Summary

  3. Motivation • Run II peak inst.lum. 2  1032cm2s-1 • Total accumulated data 2 fb-1 • Measurements with High PT e/ • Mt < 3.0 GeV/c2 •  ttbar/ttbar ~ 10% • anomalous properties of top • ( = 8.0pb/4.2pb pptt+X /ppt or t+X) •  Mw ~ 40MeV/c2 •  sin2W from Z asymmetry •  pdf from W asymmetry • fwd e-’s improve MW systematic (RunI) • (1.6106 W  e / 160 103 Z  ee) •  QCD with WZ •  qqbar  W & WW • trilinear couplings & • radiation zero effect •  SUSY searches

  4. Motivation • B Physics with electrons •   bbar ~ 100 b •  CP violation in Bd  J/Ks system •  Bs mixing •  Rare B decays •  Measurements on Bc meson • Low pT e-/ from ,  & Drell Yan • Accumulate large samples of e/ • High signal efficiency/background rejection • Possible with (trk - energy) matching •  Calorimeter (energy threshold) •  CFT, CPS, FPS & SMT (tracking)

  5. L1 & L2 Trigger Configuration • Level 1 Level 2 • F • E • L1 Accept • Expect 128 Trigger Termsto go to 256 Input7MHz output 7KHz time 4.2s Input 7KHz output 1KHz time 100s 5% dead time Silicon L2 STT CFT Ax L2 CTT L1CFT, CPS CPS Ax L2 CPS L2 GlobalCal+PS+CFT FORM 128 TriggerTerms CPS St FPS L1 FPS L2 FPS CAL L1 CAL L2 CAL Muon L1 Muo L2 Muo L1 Trigger Framework combine EM Tower, track/cluster FORM 128 TriggerTerms

  6. Challenges • Major Challenge: • Input Rate to L1 ~ 7.6MHz at 1032cm-2s-1 • <pT> e- for J/ee- <pT> e- for W,Z top ~ 2.7 GeV/c central decays • ~ 3.1 GeV/c forward ~ 30-40GeV/c • Low threshold in CAL Although threshold high •  high QCD rate S/B ~ 1/50,000

  7. Definition of EM object (e-/) • e = CFT trk + CPS cluster • + CCEM Trigger Tower •  = No Trk + CPS cluster • + CCEM Trigger Tower • e = MIP + FPS clust • + ECEM Trigger Tower •  = No MIP + FPS cluster • + ECEM Trigger Tower Central Region Forward Region

  8. L1: Tracking with CFT • Inner most tracking device at L1 is CFT (||1.5) • CFT divided into 80 sectors 4.5o wide • Fibers shared between nearest sectors • to allow for bending in magnetic field • Tracking Algorithm at Digital FE (FPGAs) •  Allowed trajectories computed analytically for • pT>1.5GeV/c (equations) •  Match hit patterns in all 8 layers with • pre-programmed equations (anchor on H layer) Sector boundary Track H CFT Sector 1 A CFT Sector 2

  9. L1: CFT Tracking (# of eqns, binning) • Neqn 1/pT per sector ( 16K eqns) • Tracks binned in pT • pT binning gives sharper turn on than offset binning • [1.5-3.0], [3.0-5.0], [5.0-10.0], [10]Gev/c

  10. L1: Energy Clustering with CPS & FPS • CPS next on path of EM particle (||1.5) • 3 layers of nested triangular strips (1280/layer) • 1 Axial Layer, strips || to z-axis • 2 Stereo Layers, strips at ~ 230 • Preceded by Solenoid & 1X0 Pb (2X0) • CPS divided into 80 sectors 4.5o wide (same as CFT) • At L1 only Axial strips used • FPS available at L1 in 1.6||2.5 • FPS divided into N/S, each side 16  sectors • 4 Layers of nested triangular strips & 2X0 Pb • 2 layers infront (MIP) of Pb; 2 behind (shower) • layers has strips making 22.50 (U & V) • MIP deposition front of Pb coincident with EM shower behind used to trigger on e-/

  11. L1: Cluster Finding ||<1.5 (CPS) • Clustering Algorithm at Digital FE (FPGAs) • Contiguous strips > Threshold forms a clusters • Two separate thresholds used for clustering • 2-5 MIPs (low) for low pT electrons (J/ee) • 5-10 MIPs (high) for high pT electrons (W,Z,top) • Only Axial strips used for L1 triggering • xxLLHLxx is one 1 high cluster (NOT 2 lows & 1 high) • Number of clusters/layer • These are input to L2 3 MIPs 5 MIPs

  12. L1: Cluster Finding 1.6<||<2.6 (FPS) • Clustering Algorithm at Digital FE (FPGAs) • Contiguous strips > Threshold forms a clusters • Two separate thresholds used for clustering • 3-5 MIPs (low) for low pT electrons (J/ee) • 5-10 MIPs (high) for high pT electrons (W,Z,top) • Cluster confirmed by MIP deposition (0.3MIPs) • 7 strip wide window centered at cluster center & • detector origin • Number of shower clusters/layer • These are input to L2 3 MIPs 5 MIPs

  13. L1: From DFE to L1 CFT/CPS, FPS & L2 • Info sent to L1 CFT/CPS • —# of () tracks per pT bin with hi/low/NO CPS axial tag • — # of isolated tracks & pT of all tracks • Info sent to L1 FPS • —# of U/V clusters (hi/low) with/without MIP hit • Info sent to CFT L2 • — list of 6 tracks per pT (46 max per quadrant) • Low pT (3GeV/c): H layer hit & (A-H) offset reported • High pT (3GeV/c): H layer hit & pT reported • Track ALSO matched to hi/low CPS Axial cluster • Info sent to CPS L2 • — From CPS Axial (48 max per Quadrants) • Axial cluster list with address and width (high & low) • Axial clusters matched to (±) CFT tracks in 3 strips • Track pT if present • — For CPS Stereo(48 max per N/S U/V) • Stereo cluster list with address & width (high & low) • Info sent to L2 FPS(48 max per N/S U/V) • —Stereo cluster list with address and width (high & low) • w/o MIP hit (48 max per quadrant)

  14. L1: Tracking & Clustering efficiency • CFT alone • efficiency 90% • FPS alone • efficiency 98% • rejection e/ 3

  15. L1: Calorimeter • Task Performed at L1 (Preamps & Analog ) • Trigger towers (TT) are 0.20.2 in  • TTs > 2.5, 5, 7 & 10GeV used as seed • L1 EM ET rounded in 0.25GeV steps • L1 Total ET truncated in 0.5GeV steps • Information available at L1 • (1) For each ref set   TT’s > Threshold (all ) • (2) EM ET /  Had ET in Large Tile Area (LTA) • (1 LTA = 8 TT’s in  & 4 TT’s in ) • (3) Number of TT’s above threshold in LTA • # TT’s > threshold for each Ref set can be made available for Quadrants • (1 Quadrant = 4 TT’s in  & 8 TT’s in ) • Send 64 AND/OR terms to L1 Framework

  16. L1: Trigger Terms • Trigger information from different detectors are sent to the Trigger Framework to be matched & final trigger decision • EM Trigger Terms • TTK(n,p): CFT track pT > p. • TEL(n,p): CPS cluster/CFT track pT(>p) match within 4.50. • TPQ(n,q): CPS cluster/CFT track (>lo/1.5Gev) match by quad. • TNQ(n,q): CPS cluster (>lo) by quadrant (no track = EM). • TDL(p,s): 2 trk/CPS cand. (pT>1.5 or 5GeV), same/opp sign • FPQ(n): FPS cluster/CAL tower(>2.5GeV) match by quad. • FQN/S(n): FPS cluster/CAL tower (>2.5GeV) match by quadrant (e+). • CEM(n,E): Cal EM tower (>2.5,5.7,10GeV) in CC or EC. • CEQ(n,q): CPS cluster/CAL Tower (>2.5GeV) match by quad q. • CER(n,E,): 1/2 CAL EM tower >2.5/5GeV in N,S,CC

  17. L1 electron algorithm (high pT) • Central (1.6) • 1 CPS cluster  high matched to 1 track 5GeV/c in 4.50 • 1 Calorimeter EM tower  7-10GeV (1.6) matched to CPS cluster by quadrant • Forward (1.62.6) • 1 FPS cluster  high + MIP confirmation • 1 Calorimeter EM tower  7-10GeV (1.62.6) matched to FPS cluster by quadrant • Track/MIP matching to PS optional; perform only if rates high ||1.0 1.6  ||2.6 Cal EM >7GeV

  18. L1 EM trigger rates (high pT) • Rates at L=21032cm2/s • Cluster/Track & CCAL Quadrant match • Cluster & ECAL Quadrant match • CEM(1,10,C) 200 W mass, QCD  • CEM(1,7,C)CEQ(1)TNQ(1) 62 QCD  • CEM(1,10,C)TEL(1,5) 3 W mass, WZ  • CEM(1,10,N/S) 690 EC W mass • CEM(1,10,N/S)FQN(1) 400 FWD EM • CEM(1,10,N/S)FPQ(1) 200 EC W mass • Rates highly dependent on thresholds in CAL • Quadrant matching give 2-4 in rates rejection ||1.0

  19. L1 Trigger timing issues • FE is 32 deep pipe line • L1 Trigger: • L1 decision conveyed to AFE in ~25 crossings • Upon L1 accept AFE/DFE send L2 data • 4.8s deadtime due to SVX readout & empty pipeline • Readout to L2: • Have to be completed within 36 crossings (4.8 s)

  20. L2 EM Trigger • Advantages at L2 are: • (1) Large decision time 100sec • (2) Finer detector information available • -- clustering in PS • -- clustering in CAL • (3) Due to more time finer matching can be • performed • -- L1 CAL/PS matching in quadrant • -- L2 CAL/PS match within 0.20.2 • in 

  21. L2: CAL Preprocessor • L1 EM Trigger based on following reference set • 2.5, 5, 7 & 10 GeV ET • (1) L2 uses TT’s above low threshold ref. set • (2) Find 2nd. Maximum in 33 around seed • (3) ETEM = ETEMseed + ET2nd > Thr • (4) EMF = ETEM/(ETEM+ETHAD) • (5) TISO =  ET(EM+Had)/ETEM( 33  - seed ) • =ETEM/ET(EM+HAD) (33  includes seed) • Both EMF & Isolation useful in background rejection

  22. L2: CAL Efficiency, Rates & Timing • (In 1.62.6) • L1 seed tower 7GeV / 10GeV • ETEM  10GeV / 12GeV • EMF  0.85 • TISO  0.4 • pT 15Gev/c 20GeV/c 32.5GeV/c • L2/L1 93.3% 99.5% 100.0% • “ 86.0% 100.0% 100.0% • Dijet Rates • L1(1,7GeV) L2(1,10GeV) L2(1,12GeV) • @2E32 900Hz 145Hz 90Hz • L2 CAL Timing(available 50sec) • L2Seed cut 0.5GeV 1.0GeV 1.5GeV 2.0GeV • # of seeds 77 19 10 7 • Time s 179 46 25 18

  23. L2: CPS Preprocessor • At L2, CPS provides 3D point combining X,U,V • Input to L2PP • Axial = cluster address, width & threshold (h/L), • tracks pT if present • Stereo = cluster address, width & threshold (H/L) • Algorithm • Hit U,V  Xuv (</=1280) & Zuv (±125cm) • Xuv -True X within ±10 Strips (0.05 in ) • Calculate  from parameterization vs. Zuv (0.004 in ) • Calculate  from Axial hit strip • Bin CPS , into 0.250.25 for CAL matching at L2 Global • OUTPUTS of L2 CPS: • HEADER: Cluster Count • DATA: Cluster  bin, • Cluster  bin, HiLo, Track Tag

  24. L2: FPS Preprocessor • At L2, FPS provides 3D point combining U & V • Input to L2PP • Stereo =cluster address, width & threshold (H/L), MIP bits • Algorithm •  parameterized as hit U + V •  parameterized as hit U - V • Confirm  as valid (within FPS detector) • Bin FPS , into 0.25*0.25 for CAL matching at L2 Global • OUTPUT of L2 FPS: • HEADER: Cluster Count • DATA: Cluster  bin, Cluster  bin, • HiLo, MIP Bit pattern

  25. L2: Preshower Timing 3MIPs 5MIPs • Available 50sec • Timing  number of clusters • CPS Low threshold ~ 90% in 40sec (500Hz devoted) • FPS Low threshold ~ 95% in 24sec (500Hz devoted) CPS FPS

  26. L2: STT & CTT Preprocessor • No STT: • L1CFT to L2CTT (Quadrants) • Converts L1 pT information to track pT (lookup table) • Extrapolates H layer  to EM3 • Merge track lists & order in pT & convert to L2 objectSend info to L2Global upto 184 tracks • With STT: • L1CFT to STT sextant boards • 48 tracks per sextant • covers 60o in  & overlap region allow for track bending • ordered in pT bin • Sextant boards to L2STT • 46 tracks per sextant • Matches CTT tracks to SMT clusters and refit • get track pT ,, dE/dX & b • send tracks to L2CTT in 12 cables 30o in  • L2STT send tracks to L2CTT • Merge 12 track lists pT • Merge 12 track lists & order in b • Send tracks to L2Global upto 184 tracks

  27. L2: CTT Timing • L2 Preprocessor Time depends on # of tracks • Time taken to make L2 objects, sort them in pT • & output them to L2Glb • Ntrk 0 1 2 4 8 16 32 64 • Time(s) 0.8 1.3 1.9 3.1 5.7 11.8 27.8 78.8 • Study performed on 233MHz board • Alpha timing 1.6 factor better

  28. L2 electron algorithm (high pT) • Central (1.6) (L2 Global 50sec) • 1 CAL tower 7GeV • 1 CPS Axial cluster  5MIPs + CFT Track tag • CPS 3D match of X,U,V ,  • (1) Axial ,U, V = 5MIPs • (2) Axial = 5MIPs & U,V = 3MIPs • Different detector info combined at L2 Global • CPS-CAL match within 0.250.25 in  • (Z  ee, 93.7%) • (1) efficiency loss for ET <40GeV(W+Jets, 84.0%) • (Z  ee, 99.0%) • (2) regains lost electrons at low ET(W+Jets, 95.4%)

  29. L2 electron algorithm (high pT) • Forward (1.62.6) (L2 Global 50sec) • CAL Cluster (ETEM)> 10GeV, • CAL EMF >/= 0.85 • CAL Isolation </= 0.4 • FPS 3D match of U,V ,  • (1) U, V = high • (2) U = high & V = low OR vice versa • Different detector info combined at L2 Global • FPS, CAL matching within 0.250.25 in  • Z  ee 94.3% - 97.5% (HH / HL.OR.LH) 900Hz @ 21032cm2/s 145Hz 80Hz 2 PS-Cal match

  30. B Physics: di-electron trigger • Triggering on low pT di-electrons: • Requirements: • - Low ET cut for in EM CAL (2.0 GeV) • - Low threshold PS clusters (2.0-.5.0 MIPs) • - Low pT track/charge sign (1.5 GeV/c) • L1 trigger • FPS • 2 CALEM towers > 2.5GeV • 2 PS candidates • =3 wedges • CPS • 2 CALEM towers > 2.5GeV • 2 PS candidates+Track • match within 3 strips • CAL / PS Cluster (quadrant) = factor 2 QDC rejection • Level-2 trigger: • - Matching: CAL / PS clusters in 0.250.25 in  • - EM fraction, DR(e-,e+), M (e-,e+), DF(e-,e+),ETISO

  31. B Physics: di-electron trigger • L1 & L2 Trigger Performance: • Central Region (CAL EM>2.5GeV, CPS>3MIPs) • eff (pT>1.5GeV) = 10%, Rates = 50Hz • Forward region (CAL EM>2.5GeV, FPS>5MIPs) • L1 eff (pT>1.5GeV) = 10%, Rates = 1.0-1.5KHz • L2 eff (pT>1.5GeV) = 4-5%, Rates = 50Hz

  32. Summary • L1 Trigger • electron (pT>5GeV) efficiency> 95% (7-10GeV CAL) • background rates1.5 Hz (7GeV CAL thr) • 200 - 500 Hz (10GeV CAL Thr) • di-e (pT>1.5GeV) efficiency~ 20%(cen), 10%(fwd) • background rates1-2kHz (cen+fwd) • PS/CAL Quadrant matching 2-3 in rates • L2 Trigger • electron (pT>5GeV) efficiency > 95% (10GeV ETEM) • background rates 50-100 Hz (10GeV ETEM) • di-e (pT>1.5GeV) efficiency ~ 10%(cen),5%(fwd) • background rates 100Hz(cen+fwd) • CAL EMF, Isolation, Invariant mass helps • PS/CAL 0.250.25 in  match = 2-3 in rates

  33. L1: CFT pT binning • Backup 1

  34. Central & Forward Preshower • CPS • FPS • Backup 2

  35. Trigger Task: L1 • L1 Calorimeter Dan Edmunds •  tsim_l1cal Josh K, Mary Anne C., Philippe L. • (Input = CAL cells; Output = TT’s & AND/OR) •  L1 framework & tsim_l1frm • Cristian Opazo-Castillo, Beatriz Pinero • (64 AND/OR terms from L1 CAL) •  CFT/CPS(axial) • AFE/DFE Kin Yip, Fred B. • L1 & L2 COL/BC Manuel M, Juan •  FPS • DFE Levan B., Manuel M. • L1 COL/BC Satish D., Manuel M. • L2 COL/BC Mrinmoy B. Manuel M. •  tsim_l1ft (CFT+CPS+FPS) • Kin Yip, Levan B., Mrinmoy B., Satish D. •  STT Overlap & sextant boards • Brian Connoly, Manuel M.,William Lee •  L1 Trigger Terms • Jerry Blazey • Backup 3

  36. Trigger Task: L2 •  L2 Global & tsim_l2glb (include tools) • Roger Moore, Dylan Casey • (combine CAL, PS, CFT; write EM objects) •  L2 STT & tsim_l2stt • Silvia R.,John H.,Wendy T. • (perform track fitting, track pT, impact) •  L2 CAL & tsim_l2cal • Robert Hirosky, Marc Beuhlar • (cal cluster, EMF, Isolation) •  L2 CTT & tsim_l2ctt • Dave Toback, Drew Baden • (track pT, impact, EM3, track sign) •  L2 PS & tsim_l2prs (CPS+FPS) • Mrinmoy B. • (cluster , threshold, MIP pattern, track tag) • Backup 4

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