1. Rich Occupancies and Bandwidth in Minimal Upgrade Layout
My Work so far...
Robert Currie 12/04/2010

2. '... a stepping stone in development of the LHCb software...'
Simulation
Want to estimate the requirements of the electronics for the RICH detectors in the LHCb upgrade.
Using events simulated using the Minimal Upgrade Layout
(MUL without Aerogel) :
'... a stepping stone in development of the LHCb software...'
To measure the bandwidth required we need to know the Occupancy of modules within the RICH detectors.
Gauss
Boole
Occupancy
Thanks to Young Min for helpful discussions on Simulation work
Slide 2

3. Simulation Data
Physics Events Simulated in Gauss and digitized in Boole according to the MUL and the occupancy per HPD is extracted from the expert histograms.
The total number of events analysed in my work so far is:
~10k events at Lumi20
~25k events at Lumi2
Only Lumi20 results will be discussed in the main talk with Lumi2 Occupancies given in backup Slides
Slide 3

4. Cable & Bandwidth Numerical Example:
For each module in RICH, the number of GBT cables required is
Determined by the number of hits in each module and this is
calculated from it's occupancy
1 cable carries bits per cable per event[1]
1 hit in RICH module (1024 pixel)
binary readout, zero suppressed = bits of data/hit
Numerical Example:
E.g. 4 cables per module: (suitable for outer detector)
4 x 80 / 10 gives a BW limit of hits/ (module * event)
= occupancy of ~3% for each module.
Slide 4
[1] Johans slides on Torch:

5. Module Occupancies Lumi 20 Typical Low Occupancy: Outer Detector
Occupancy PDF typical of most low occupancy modules within both Rich1&Rich2
Typical Low Occupancy:
Outer Detector
Red: Data Blue: Fit
Slide 5

6. Module Occupancies Lumi 20 Highest Occupancy: Inner Detector
Occupancy PDF typical of
High Occupancy modules
at the centre of the detector
planes in Rich1&Rich2
Highest Occupancy:
Inner Detector
Red: Data Blue: Fit
Slide 6

7. Cables required to read 99% of all events across RICH 1 at Lumi20
Slide 7

8. Cables required to read 99% of all events across RICH 2 at Lumi20
Slide 8

9. Example link-map required for 99% data readout for Rich1
Slide 9

10. Example link-map required for 99% data readout for Rich2
Slide 10

11. Efficiency Map of Rich1
Slide 11

12. Efficiency Map of Rich1
Slide 12

13. Efficiency vs Bandwidth
Hits are truncated between events if BW limit is exceeded:
for a fixed number of links with the single highest occupancy
module at Lumi20 one gets:
Same module as on Slide 6 (Rich1 Col7 Row4)
Number of Links
% of events with truncated data
Max Number of transmitted hits
Average number of lost hits 2
90.5 16
51.8 4
76.4 32
38.5 8
47.3 64
19.6 12
24.7 96
8.3
10.5
128
3.0 20
3.8
160
0.9 24
1.2
192
0.2
Slide 13

14. Zero Suppression Threshold
Passing just binary readout data from the module equates
to 1024 bits of data per event.
1024 / 80 = 12.8
Hence 13 cables required for all data to be transmitted
from each module.
When zero suppression requires more than 13 cables it is
more efficient to change the data transmission strategy
to binary only readout.
Slide 14

15. Cable Numbers Only zero-suppressed data transmitted:
Rich1 Rich2
Only zero-suppressed data transmitted:
Total Number of Cables:
Max per Module:
With non-zero-suppressed data
transmitted in centre modules:
Total Number of Cables:
Max per Module:
Slide 15

16. Number of Cables for Rich1 non-zero suppressed in centre
Slide 16

17. Number of Cables for Rich2 non-zero suppressed in centre
Slide 15

18. Conclusions
Developed method to study the number of required links in RICH
for expected occupancies in LHCb Minimal Upgrade Layout.
Large numbers of cables per module required at the centre of the
RICH detectors to read zero suppressed data at high efficiencies.
Moderate numbers of links required at outer regions of detector
planes.
Link numbers suggest to employ zero-suppressed readout for
most of the detector planes, but non-zero-suppressed readout
for centre areas.
Slide 18

19. Further Work Repeat the Study for MUL with Aerogel for the simulation
(occupancy in RICH1 may be higher)
Obtain Better Statistics for Lumi20 and directly compare to
Lumis 5 & 10 as well (to check for proper evolution of occupancies)
Optimise cable number / module
Slide 19

20. BACKUPS

21. Module Occupancies Lumi 2 Typical Low Occupancy: Outer Detector
Occupancy PDF typical of most low occupancy modules within both Rich1&Rich2
Typical Low Occupancy:
Outer Detector
Red: Data Fit not plotted
Slide 5

22. Module Occupancies Lumi 2 Highest Occupancy: Inner Detector
Occupancy PDF typical of
High Occupancy modules
at the centre of the detector
planes in Rich1&Rich2
Highest Occupancy:
Inner Detector
Red: Data Fit not plotted
Slide 6