Meeting Minutes
Date: April 23, 2026
Time: 10:00 AM
Location: Virtual
Attendees
- Prajwal Mohan Murthy
- Zhengqiao Zhang
- Haixin Huang
- Deepak Raparia
Absent:
- Frank Rathmann (on sick leave)
1. Administrative Updates
- Frank is on medical leave; meeting proceeded without him.
- Fiscal/bridging contract:
- MIT approval delayed due to workload (Genesis project).
- Expected approval: May 1 (MIT side).
- Additional processing time required afterward.
- Follow-up:
- Prajwal will send a When2Meet poll for fiscal discussion.
2. Presentation: Helium-3 Breakup & Veto Tagging Simulation
Presenter: Zhengqiao Zhang
2.1 Simulation Overview
- System: Helium-3 jet target in IR4.
- Goal:
- Understand breakup fragment kinematics.
- Optimize detector design and tagging.
- Tools:
- Geant4 (FTFP_BERT physics list)
- DPMJET model for collision generation
- Beamline elements:
- Two warm dipole magnets (~0.8 T, 2 m length)
- Purpose: separate breakup fragments from beam
2.2 Breakup Scenarios
Four cases simulated:
- Both beam and target breakup
- Target-only breakup
- Beam-only breakup (of primary interest)
- No breakup
- When beam-only breakup fraction is very small, poses tagging challenges.
2.3 Kinematics & Cross Sections
- Observations:
- Forward-peaked distributions (high energy at small angles).
- Cross-sections sharply decrease with angle.
- Non-trivial structure observed in proton–He³ case:
- Likely corresponds to:
- Single proton separation (~5.5 MeV)
- Full breakup (~7.7 MeV)
2.4 Tagging Efficiency
- Depends on:
- Beam energy
- Beam pipe geometry (5–7 cm diameter, 1 mm thickness)
- Detector placement
Key Results:
- High energy (e.g., 183 GeV He³–He³):
- Low energy:
- Efficiency significantly reduced (when fragments don’t reach detectors)
Key Insight:
- Efficiency includes:
- Detector response
- Transport/acceptance effects
2.5 Discussion Points
- ~2.9% inefficiency source:
- Fragments insufficiently bent to reach detectors.
- Concern:
- Must not introduce systematic uncertainty in polarization measurement.
- Requirement:
- Efficiency must be known to ≤0.1% precision.
2.6 Requested Improvements
- Include both:
- Beam breakup AND target breakup for all cases.
- Provide:
- Additional 8 plots (completing missing configurations)
- Future work:
- Extend study to AGS kinematics (longer-term)
3. MIT Progress Update (Prajwal)
3.1 Paper Strategy Revision
Original single paper → split into three papers:
Paper 1: EIC Polarimetry (aimed at J. Instrum.)
- Topic: Absolute He³ polarimetry at EIC (IR4) using ABS + storage cell
Paper 2: ABS Instrumentation (aimed at RSI)
- Focus:
- Description of upgraded He³ ABS apparatus
- Motivation:
- Document engineering work (BNL contract)
Paper 3 (Future): AGS + MEOP
- Separate study:
- AGS polarimetry using MEOP
- To be rounded out by (possibly by future postdoc)
3.2 Key Technical Results from Paper-1
- Target polarization:
- Statistical precision: ~ppm-level (very fast)
- Systematic uncertainty: ~0.2%
- Implication:
- Acceptable for ~0.5–1% beam polarization measurement
- Next step:
- Build full systematic budget including veto effects
4. Journal Strategy Discussion
- Avoided:
- NIM (requires real data, not just design/simulation)
- Selected:
- RSI for instrumentation
- J. Instrum. for EIC-ABS TDR
5. Timeline
- EIC paper draft: ~1–1.5 months
- RSI paper draft: by July 2026
- Internal review: ~1 month
- Submission target: Summer 2026
- MEOP/AGS TDR: Fall 2026 (post-grant)
6. Action Items
Zhengqiao Zhang
- Add missing breakup cases (beam + target for all systems)
- Generate additional plots (~8 more)
- Verify origin of cross-section peaks (5.5 MeV & 7.7 MeV)
- Clarify tagging efficiency definition and uncertainties
Prajwal Mohan Murthy
- Integrate veto tagging results into paper
- Finalize systematic uncertainty framework
- Circulate drafts (by July)
- Send When2Meet for fiscal meeting
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