1. Felix Sefkow DESY LDC at Vienna November 17, 2005
LDC HCAL
Felix Sefkow
DESY
LDC at Vienna
November 17, 2005

2. HCAL detector outline Basic configuration Open design issues
Optimization
Felix Sefkow LDC at Vienna,
LDC HCAL

3. Configuration The HCAL is inside the coil.
No substantiated objections raised.
Felix Sefkow LDC at Vienna,
LDC HCAL

4. Technology
The conceptual choice between scintillator and gas as active medium should be based on testbeam results.
If a classification by Baseline / Alternative had to be done at this (inappropriate) time, my matrix would look like this
Fe B B’ A
Pb A
W A A A
where baseline means: can proceed to technical design and costing now
C.c.: The conceptual choice between scintillator and gas as active medium should be based on testbeam results.
Felix Sefkow LDC at Vienna,
LDC HCAL

5. Alternative options
W has less than half the hadronic interaction length of Fe
Gain depth or reduce magnet volume
Pb (with scintillator) offers “hardware compensation”
Both W and Pb would allow to build HCAL and ECAL with the same absorber - this opens new degrees of freedom to optimize the ECAL – HCAL transition
The study of these options requires (at least)
A full-fledged engineering design (only Fe is self-supporting)
To evaluate the amount of dead zones for support
Re-optimization of the granularity due to different Moliere radii
Testbeam – since the role of neutrons is quite different
Felix Sefkow LDC at Vienna,
LDC HCAL

6. Dimensions Barrel Endcap Mass 500t + 2 * 200t Depth 4.4 (5.3) 
180 < R < 280 cm
-220 < z < 220 cm
Endcap
30 < R < 270 cm
250 < |z| < 380 cm
Mass 500t + 2 * 200t
Depth 4.4 (5.3) 
Active area ~ 5000 m2
(for 38 (50) layers)
Felix Sefkow LDC at Vienna,
LDC HCAL

7. Important details Barrel endcap transition Endcap FCAL transition
Endcap ring and a smallest possible gap are probably needed for inside-out clustering / pattern recognition
Endcap FCAL transition
Cut-out most likely degrades forward jets
Apparently has already disappeared – new picture would be nice!
Felix Sefkow LDC at Vienna,
LDC HCAL

8. Depth This HCAL is a bit skinny.
PFLOW reduces the problem (for charged particles)
To what extent – at high E?
Shower shape “extrapolation” unreliable
Cannot use last HCAL layer as leakage veto!
How much does the tail catcher recover?
1st layer active!
Felix Sefkow LDC at Vienna,
LDC HCAL

9. Sampling TDR: Steel thickness follows from X0
20mm Fe, 5mm Scint, 1.5mm r/o
Steel thickness follows from X0
Scintillator should be thin but give enough light from MIPs for calibration
Thinner scintillator might become possible with more efficient photo-sensors
Compensation possible with steel
But check sampling statistics
At least gain interaction depth
Or € from coil volume
Volume ratio
(Wigmans)
Felix Sefkow LDC at Vienna,
LDC HCAL

10. Granularity
Scintillators: trade granularity against amplitude resolution
3cm tile size optimized for shower separation – and semi-digital readout
Variation with depth not fully explored
Felix Sefkow LDC at Vienna,
LDC HCAL

11. Clock+Config+Control
Readout architecture
The mechanical structure of the TESLA TDR HCAL was based on readout with clear fibres to photodetectors to be placed near the front end electronics
With SiPMs other configurations become possible – one example: following the ECAL architecture
With highly integrated electronics and early data reduction
Slab FE
FPGA
PHY
VFE
ASIC
Data
Clock+Config+Control
Conf/
Clock
Felix Sefkow LDC at Vienna,
LDC HCAL

12. Calibration and electronics
We assume that we need at least a simple light injection system for debugging and timing checks
Radioactive sources have an interesting potential
Requires auto-triggering electronics
The final electronics design depends on calibration procedure
Eg power pulsing may exclude cosmics
Benefits of time resolution for clustering should be further evaluated
NB: Also for RPCs, operational stability and monitoring issues are still to be addressed (testbeam) – with possible consequences on readout architecture
Felix Sefkow LDC at Vienna,
LDC HCAL

13. Mechanical structure
The mounting scheme for the ECAL – hanging with rails on the HCAL might need to undergo revision, too.
Felix Sefkow LDC at Vienna,
LDC HCAL

14. Summary
The HCAL readout architecture and mechanical structure should be revised.
Most important issues for optimization are
Depth
Cracks
Sampling
Granularity
Calibration
Timing
And don’t forget background
Felix Sefkow LDC at Vienna,
LDC HCAL

15. Backup slides
Felix Sefkow LDC at Vienna,
LDC HCAL

16. PFLOW performance By far not the final word, but state of the art
A. Raspereza
Felix Sefkow LDC at Vienna,
LDC HCAL

17. Use the weights which optimize hadron energy resolution
Imaging quality
Shower in scintillator appears* wider than in gas
Large model dependence of shower width
* unweighted
Use the weights which optimize hadron energy resolution
Felix Sefkow LDC at Vienna,
LDC HCAL

18. Making decisions Henry Ford I Felix Sefkow LDC at Vienna, 17.11.2005
LDC HCAL