1. First steps on optimising RICH analysis
Outline:
Improved ring-track matching for low momentum (W.Koenig)
Pad multiplicity and comparison with simulation
Summary and conclusion
Christina Dritsa
JLU Giessen
XXV Hades Collaboration Meeting, GSI. Darmstadt November

2. Improve ring track matching for low momenta
W.Koenig

3. Improve ring track matching for low momenta
W.Koenig

4. Improve ring track matching for low momenta
W.Koenig

5. Improve ring track matching for low momenta
W.Koenig

6. Pad multiplicity and comparison with simulation

7. RICH analysis - reminder
0. Hardware thresholds (pedestals, cut on 3xσ noise)
1. Cleaning:
Removes 2 types of structures
single pads (mainly firing due to unusually high noise)
large structures with high pulse (from direct hits)
2. Labelling:
flag areas to search for rings (increase speed of analysis)
3. Ring finding
“Hough” transform
Pattern matrix
Question: Is there room for optimising these steps to enhance the ring finding efficiency without creating more fake rings?

8. Pedestals S0 S1 S2 S3 S4 S5 DATA, apr12 SIMULATION, apr12
Uniform distribution of thresholds over all the sector surface
Same for simulation

9. Thresholds S0 S1 S2 S3 S4 S5 DATA, apr12 SIMULATION, apr12
Pattern may be explained by the different lengths of circuit paths connecting the pad and the amplifier. This leads to different capacitances and hence the noise of the channels vary slightly.
Middle lines with high thresholds are due to missing CsI cathode coverage at the edges of the 3 sector segments.

10. RICH “anatomy”
Anton Johann Kastenmüller,
PhD thesis

11. Same effect observed before (old electronics)
Anton Johann Kastenmüller, PhD thesis (2000)
Note that in simulation the noise is always represented by a Gaussian function.
This is not the case in reality: noise distribution has “tails”!

12. Investigation of the pad multiplicity for different event multiplicity classes

13. Number of hits ToF+RPC

14. All firing pads, Sector 0, day 123
0-20
> Slight dependence
on event multiplicity.
> Inner part of sector has
relatively high occupancy
> Similar behaviour observed for all sectors
80-100

15. Single pads removed, sector 0, day 123
> No dependence
on event multiplicity, as expected.
> Similar behaviour observed for all sectors (not shown here)

16. Single pads remaining, sector 0, day 123
Slight dependence
on event multiplicity.
Inner part of sector has
relatively high occupancy
Are thresholds lower than needed?
Enhancement of fake rings?
Similar behaviour observed for all sectors

17. Comparison to simulation: Number of remaining pads as a function of theta
DATA
SIMULATION

18. Comparison to simulation: Number of remaining pads as a function of theta
DATA
SIMULATION

19. Comparison to simulation: Number of rings as function of theta
Data, all sectors
Simulation, all sectors
100k events
60k events
Real data are seemingly dominated by high noise in the low theta region. This might lead to fake rings which pass the standard ring quality cuts!
Discrepancy with simulation!

20. Ring-to-proton matching
θrich S0
Select protons from ToF/RPC:
β<0.7
charge==1
mom>700MeV
Select Rings:
AC>70
Centr>0
matched ring index
Selected rings match to identified protons from ToF/RPC.
Clear enhancement of the fake matches in the low theta region (RPC region)

21. Summary
New method introduced by Wolfgang improves ring-track matching for low momentum tracks by a factor up to 6!
Non uniform noise levels lead to non-uniform threshold settings:
Low theta region seems to have much higher occupancy potentially due to too low threshold settings
Problem with “good quality” fake rings matching to non-leptons for low theta
Discrepancies between simulation and measurement for pad and ring multiplicities
Outlook
Need to bring simulation and measurement closer!
Investigate different threshold settings (e.g. increase thresholds in inner theta region)
Update noise in simulation: Replace Gauss by “Gauss+tails” taken by measurement
Investigate close pair rejection (in progress by Wolfgang)

22. Improve ring track matching for low momenta
W.Koenig

23. Same effect observed before (old electronics)
Anton Johann Kastenmüller, PhD thesis (2000)
Note that in simulation
the noise is always represented
by a Gaussian function.
This is not the case in reality:
noise distribution has “tails”!
Effect smoothed out with improved grounding.
Measurements done in laboratory with pulser.

24. close pair investigation
W.Koenig