The Level-0 Calorimeter Trigger and the software triggers Umberto Marconi INFN Bologna CSN1 Lecce, 24 September 2003

Overview The L0 calorimeter trigger The L1&HLT trigger The Selection Crate Project Cost 2004 activity plan The L1&HLT trigger LHCb Trigger System CERN/LHCC 2003-31, LHCb TDR 10, September 2003 LHCb Reoptimized Detector Design and Performance CERN/LHCC 2003-30, LHCb TDR 9, September 2003 U. Marconi INFN, Bologna

Trigger Architecture Level-0 trigger (fixed latency 4μs) Reduce the 10MHz visible interaction rate to 1.1 MHz Event selection: the highest ET hadron, electron,photon The two highest pT muons Level-1 trigger (variable latency, 58ms max) Output rate is fixed at 40KHz The decision is delivered chronologically ordered Event selection: B vertex HLT (variable latency) Output rate is established at 200 Hz Event selection: algorithms for specific decay modes U. Marconi INFN, Bologna

The L0 Trigger Hardware trigger, custom electronics 4 systems Calorimeter trigger system Select high ET particles from their calorimeter deposits Electrons, photons, π0 and hadrons Muon trigger system Select high PT muons with fast tracking Pile-Up system Measures the number of p-p interaction in each crossing Decision unit Combines the information from the 3 sources, propose the decision to the Readout Supervisor. U. Marconi INFN, Bologna

L0 Calorimeter Trigger Detect a local high ET cluster in ECAL or HCAL 2x2 cells From 8x8 cm2 (Inner ECAL) to 52x52 cm2 (Outer HCAL) ECAL: 5952 cells -> 5952 possible clusters Validation by PS/SPD (same geometry) to get electron and photon candidates Combination to get π0 candidates. HCAL : 1484 cells -> 1484 possible clusters Add the ECAL ET in front if available Local Maximum Validation U. Marconi INFN, Bologna

The Selection Crate LHCb Note 2003-095 Data input @ 40 MHz 28 electron clusters 28 photon clusters 2x28 neutral pion clusters (local, global) 80 hadron clusters 16 SPD hits partial sums Data output to the L0DU @40MHz Highest transverse energy cluster for each cluster type (5 highest) Total transverse hadron energy (global trigger variable) Total SPD hit multiplicity (global trigger variable) Data output to the L1 trigger @1.1MHz The entire set of the processed clusters U. Marconi INFN, Bologna LHCb Note 2003-095

The Selection Board Processing Unit Input Interface Output Interface U. Marconi INFN, Bologna Slow Control Fast Control

Test of the prototypes (I) The Processing Unit functionalities are implemented in a single FPGA 1150 I/O pins FPGA U. Marconi INFN, Bologna

Test of Prototypes (II) The optical link to be used in the output interface has been successfully tested The level of the BER is around 10-13 even in the worst jitter conditions of about 10-2ps peak-to-peak U. Marconi INFN, Bologna

Test of the Prototypes(III) We are ready to start testing the input interface The prototype hosts a single 12 channels optical/voltage transducer and 8 deserializers It is built as a 1/3 of a 9U standard board U. Marconi INFN, Bologna

New Cost Estimate Old vs New Implementation The allocated INFN budget to build up the Level-0 Calorimeter Trigger is of 800KCHF The cost now is of about 450KCHF 2004 plans Build up the final prototype integrating the Input Interface, the Processing Unit, the Ouput Interface and the Slow Control (ECS) in one 9U board Old Impl. #Boards New Impl. Electron 2 1 Photon SPD Neutral Pion 4 Hadron 8 3 U. Marconi INFN, Bologna

Sharing the L0 Bandwidth The L0 thresholds has been defined by requiring the bandwidth division among a set of reference channels that minimizes the overall loss in efficiency, by miximizing Σch (εL0ch / εL0ch-max) with the constraint of 1.1MHz ouput rate where εch-max is the efficiency when the full bandwidth is available εch is the efficiency obtained for a set of thresholds Cut (GeV) M.B. Rate (KHz) Hadron ET =3.6 705 Electron ET = 2.8 103 Photon ET = 2.6 126 π° local ET = 4.5 110 π° global ET = 4.0 145 muon pT = 1.1 ΣpμT pT = 1.3 U. Marconi INFN, Bologna

L0 Trigger Efficiencies vs L0 output rate εL0ch ε L0ch-max Full bandwidth available to the channel U. Marconi INFN, Bologna

L0 Trigger Efficiency for Offline Selected Signal Channels HCAL Trigger dominates Electron Trigger dominates MuonTrigger dominates U. Marconi INFN, Bologna

L0 Trigger Efficiency for Offline Selected Signal Channels Trigger Correlations Decay Channel εL0/sel (%) Hadron Trigger Electron Trigger Muon Trigger B° π+π- 53.6 47.6 14.1 6.8 B° π+π- π° 77.2 39.4 66.2 7.9 B° D*-π+ 49.0 41.7 14.0 8.4 B°s Ds-π+ 49.4 42.2 13.1 8.3 B°s Ds-K+ 47.2 11.7 8.2 B° J/Ψ(μμ)K°s 89.3 18.6 87.2 B° J/Ψ(ee)K°s 48.3 21.5 37.4 7.0 B°s J/Ψ(μμ)Φ(K+K-) 89.7 20.0 87.4 B° K*(K+ π-) 72.9 32.7 68.1 7.8 U. Marconi INFN, Bologna

Tracks T track Upstream track VELO seeds Long track (forward) Long track (matched) VELO track T seeds Downstream track Long tracks  highest quality for physics (good IP & p resolution) Downstream tracks  needed for efficient KS finding (good p resolution) Upstream tracks  lower p, worse p resolution, but useful for RICH1 pattern recognition T tracks  useful for RICH2 pattern recognition VELO tracks  useful for primary vertex reconstruction (good IP resolution) U. Marconi INFN, Bologna

L1 Trigger 250cm 2D RZ-tracks in the VELO PV reconstruction 3D reconstruction (of large impact parameter tracks) Measure pT using the 3D VELO tracks to TT then 3D matching to the L0 objects RMSx,y=25μm RMSz =60μm 250cm U. Marconi INFN, Bologna

VELO-TT Tracking in L1 In average 8.5 tracks need to be reconstructed in 3D from 60 forward 2D tracks in the VELO in a minimum bias event requiring an impact parameter between 0.15 and 3 mm The reconstruction efficiency on reconstructable B-decay product is 94% U. Marconi INFN, Bologna

The Level-1 Trigger Variables Mbias Mbias Bππ Mbias U. Marconi INFN, Bologna

Level-1 Efficiencies Decay Channel εL1 (%) B° π+π- 62.7 B° π+π- π° 46.6 B° D*-π+ 56.0 B°s Ds-π+ 63.0 B°s Ds-K+ 62.6 B° J/Ψ(μμ)K°s 67.7 B° J/Ψ(ee)K°s 54.9 B°s J/Ψ(μμ)Φ(K+K-) 71.4 B° K*(K+ π-) 51.9 U. Marconi INFN, Bologna

L1 Computing Time On average 8.3ms is spent in L1 with the algorithm on a 1GHz PIII CPU (not optimized to allow large scale stabilized physics studies) The L1 trigger algorithm has been speed up in the meanwhile. The average processing time is now 6ms The average processing time per event is expected will be less than 1ms in the 2007 Present time+Moore’s law: <1000 CPU nodes 1 GHz Pentium III U. Marconi INFN, Bologna

HLT L1-Confirmation HLT (L1 Confirmation) 10MHz of visible pp interaction contains 100KHz of beauty events bb(%) cc(%) Generated 1.1 5.6 Level-0 3.0 10.6 Level-1 9.7 14.2 HLT-L1C 14.0 14.7 The beauty content of the 20 KHz of the events which have to be analyzed after the HLT L1-confirmation is still dominated by light quark events U. Marconi INFN, Bologna

HLT Selection Algorithms The combined output rate of all channels under study at the moment in LHCb, including the background, is less than 1Hz The HLT will have a significatively larger output rate due the need to relax the final selection cuts to study the sensitivity and systematics The RICH reconstruction on the event passing the HLT filter can be executed at a rate of a few hundred Hz Algorithm HLT rate (Hz) B J/Ψ(μμ)X 21±4 B h+h- 12±3 B Dsh B° K*0(K+ π-)π+ 13±3 U. Marconi INFN, Bologna

Efficiencies, Event Yields and Bbb/S ratios Nominal year = 1012 bb pairs produced (107 s at L=21032 cm2s1 with bb=500 b) Yields include factor 2 from CP-conjugated decays Branching ratios from PDG or SM predictions U. Marconi INFN, Bologna

Conclusions The design of the Selection Crate is almost complete. The 28 input channels optical interface of the Selection Board still has to be tested A final prototype of the Selection Board will be built in the 2004 The design phase of the L1&HLT triggers of LHCb is finished. The trigger system is flexible, robust, efficient. U. Marconi INFN, Bologna

Monte Carlo Generation total = 100 mb visible = 65 mb pp interactions Minimum bias events from PYTHIA 6.2 Hard QCD processes, single and double diffraction Multiple parton interactions tuned to reproduced track multiplicities observed at SPS and Tevatron energies bb events Extracted from minimum bias sample bunch crossings in LHCb Size of luminous region Simultaneous pp interactions (“pileup”) number of visible interactions n (in events with at least one) distributed according to L = 2  1032 cm2 s1, <> = 30 MHz bb/ visible = 0.8% x= y = 70 m, z = 5 cm At least two tracks reconstructible in whole spectrometer <n>min bias = 1.23 <n>bb event = 1.42 U. Marconi INFN, Bologna

Result of Track Finding T1 T2 T3 VELO TT Typical event display: Red = measurements (hits) Blue = all reconstructed tracks Average multiplicity in bb event <p/p> efficiency (IP) 26 long tracks 0.37% 94% for p >10 GeV/c 40 m 4 downstream tracks 0.43% 80% for p > 5 GeV/c 11 upstream tracks ~15% 75% for p > 1 GeV/c 5 T tracks 26 VELO tracks Total = 72 tracks 2050 hits assigned to a long track 98.7% correctly assigned U. Marconi INFN, Bologna