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

2. 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 , LHCb TDR 10, September 2003
LHCb Reoptimized Detector Design and Performance
CERN/LHCC , LHCb TDR 9, September 2003
U. Marconi
INFN, Bologna

3. 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

4. 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

5. 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

6. 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
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
The entire set of the processed clusters
U. Marconi
INFN, Bologna
LHCb Note

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

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

9. 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 even in the worst jitter conditions of about 10-2ps peak-to-peak
U. Marconi
INFN, Bologna

10. 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

11. 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

12. 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

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

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

15. 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

16. 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

17. 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

18. 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

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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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