1. AHCAL Transportation Constraints

Overview:

• The transportation team has provided the dimensional limits of the transport platform:

  • Width: 1000 mm

  • Length: 3000 mm

  • Height: 900 mm

• The current AHCAL structure exceeds these limits slightly.

Options Discussed:

1. Larger Transport Platform:

   • Would require new design and verification by civil engineering.

   • Long lead time (previous example: 3 months).

   • Estimated cost over 10k CHF?

2. Rebuild the Frame:

   • The current frame holds 40 layers and is not disassemblable.

   • Remaking the frame would be costly and time-consuming.

3. Modify the Existing Frame:

   • Mechanical feasibility under investigation.

   • May involve reducing frame thickness or trimming corners.

   • Preliminary feedback suggests this is technically challenging.

Alternative Approach:

• Custom Cradle:

  • Proposed to build a simpler cradle with lifting points 1.8 meters apart.

  • Should support the frame (without iron plates).

  • Target weight under 2 tons.

  • Could be manufactured locally in China to reduce cost.

Action Items:

• Shunliang? to provide detailed photos of the frame and potential lifting points.

• USTC mechanical engineers to evaluate the cradle design.

2. DAQ and Trigger System

TLU-Based Trigger Logic:

• The TLU board accepts 6 inputs:

  • 2 channels for veto scintillators

  • 4 channels for analog signals from AHCAL

• TLU settings (threshold, delay, veto stretch) can be adjusted via software.

• No firmware update required.

• Configuration validated during previous test beam campaigns.

Trigger Optimization (Presented by Yasuhiro Maruya):

• Simulation tested conditions for neutron rejection and ν_eCC efficiency.

• Trigger condition:

  • At least 2 of layers 18, 19, 38, or 39 receive signal > 0.2 MeV within 10 ns window.

• Efficiency:

  • ν_eCC detection: ~98%

  • Good suppression of delayed neutron background.

Engineering Concerns:

• Need to confirm where the sensitive region of AHCAL begins relative to the floor.

• This affects placement height of veto scintillators.

Action Items:

• Yunlong/Zhen to confirm sensitive region height with photos and measurements.

• Brian to propose scintillator dimensions (suggested: 80x80 cm).

3. Digitization Updates (Yasuhiro Maruya)

Key Changes:

• Implemented new digitization from Hongbin:

  • Cell-by-cell calibration of SiPM and electronics characteristics.

  • Consideration of low-gain saturation effects.

  • Artificial cap at 80 MeV per cell introduced for worst-case scenario.

Results:

• ν_eCC Energy reconstruction:

  • Std. Dev. (E_reco/E_truth):

    • Old: 29%

    • Updated: 32%

    • With saturation: 35%

• ν_eCC PID and background rejection:

  • Slight improvement with calibrated digitization.

  • Slight degradation with saturation, but within acceptable bounds.

Conclusion:

• Digitization changes do not significantly impact overall detector performance.

4. D-Meson and Tau Decay Handling

Motivation:

• GEANT4 does not fully simulate decay of charm hadrons and tau leptons.

• Previously defaulted to hadronic decay only.

Updates:

• Introduced Pythia8 decay handling.

• Enabled more realistic decay chains including leptonic channels.

Effects:

• ν_eCC PID rejection performance:

  • Slight drop (~8%) in ν_μCC and NC rejection due to muon tracks.

  • Minor effect on ν_eCC detection.

• Flux measurement uncertainty:

  • Increased slightly (from 56%~112% to 57%~118%).

Conclusion:

• No critical degradation.

• Handling of D decays via Pythia8 is preferred for realism.

5. Miscellaneous and Next Steps

Photos and Geometry

• Shunliang will visit the site and take photographs.

• Frame geometry, lifting hook placements, and sensitive region locations will be documented.

Trigger Placement and Design

• Scintillator placement depends on active volume height.

• Placement should avoid interference and align with active area.

Summary:

• Frame transportation challenge actively discussed.

• DAQ and digitization components are mostly ready.

• Trigger logic and placement design progressing.

Next Meeting Tasks:

• Share frame photos and detailed geometry.

• Finalize cradle/lifting structure design.

• Confirm trigger logic parameters with hardware.

• Validate decay model impact with further simulation if needed.