Muon闪烁体能损Landau分布拟合

Exported on 2026-06-01

User

Jun 2, 2026, 02:20

/geant4-planer

创建一个固体闪烁体探测器 (20x20x5cm) 置于空气中, 能量为 1GeV 的宇宙线 muon 从中心正上方 (10x10cm, 距离闪烁体 1cm) 击中探测器. 模拟 muon 在闪烁体中的能量沉积并绘制能损分布图. 使用 Landu 分布拟合能损分布图.

                 |
                 | muon 1GeV
                 |
                 V
    +---------------------------+
    |                           |
    |                           | 5cm
    +---------------------------+
                 20cmThe user explicitly mentioned these skills in their message: /geant4-planer. Use the corresponding skill tool when it is relevant to accomplishing the user's request.

Assistant

Jun 2, 2026, 02:21 (deepseek/deepseek-v4-pro)

Now I have a clear picture of the existing project. Let me present the assessment and current status.

Project Assessment

The existing codebase is a skeleton Geant4 project. Here’s what I found:

There are also several compilation errors (undefined variables, missing method declarations) that need fixing.

Given your requirements — all phases need to be (re)implemented. Let me create the tracking file and we’ll start from Phase 1.

Assistant

Jun 2, 2026, 02:21 (deepseek/deepseek-v4-pro)

Phase 1: Geometry & Materials

Your requirements are clear: 20×20×5 cm³ solid scintillator in a world of air. Before I generate the code, I need to confirm the scintillator material:

Assistant

Jun 2, 2026, 02:22 (deepseek/deepseek-v4-pro)

NaI(Tl) — good choice. Let me load the detector construction skill to generate proper geometry code.

Assistant

Jun 2, 2026, 02:22 (deepseek/deepseek-v4-pro)

G4_SODIUM_IODIDE is available as a NIST material. The geometry is straightforward — let me generate the Phase 1 code now.

Assistant

Jun 2, 2026, 02:22 (deepseek/deepseek-v4-pro)

The return value needs fixing — let me correct that.

Assistant

Jun 2, 2026, 02:22 (deepseek/deepseek-v4-pro)

Now let me try building to verify the geometry compiles:

Assistant

Jun 2, 2026, 02:23 (deepseek/deepseek-v4-pro)

Pre-existing errors in g4.cc — let me fix them so we can build.

Assistant

Jun 2, 2026, 02:23 (deepseek/deepseek-v4-pro)

Now let me also fix the other compilation issues in existing user-action files so we get a clean build.

Assistant

Jun 2, 2026, 02:24 (deepseek/deepseek-v4-pro)

Build succeeds. Phase 1 implementation is done:

• World: 1m³ box filled with G4_AIR
• Scintillator: 20×20×5 cm³ NaI (G4_SODIUM_IODIDE, cyan color) centered at origin

Let me update the tracking file and present for your confirmation.

Assistant

Jun 2, 2026, 02:24 (deepseek/deepseek-v4-pro)

Phase 1 is complete. Please verify the geometry in GUI mode:

./build/g4

You should see a cyan NaI scintillator slab (20×20×5 cm³) centered in the air-filled world. After confirming, reply confirm and we’ll proceed to Phase 2 (Physics List).

User

Jun 2, 2026, 02:26

confirm, proceed

Assistant

Jun 2, 2026, 02:26 (deepseek/deepseek-v4-pro)

The physics needs are straightforward here. Let me verify the reference patterns:

Assistant

Jun 2, 2026, 02:26 (deepseek/deepseek-v4-pro)

Phase 2: Physics List Assessment

For a 1 GeV muon in NaI, the physics needs are purely electromagnetic:

The muon processes covered: ionization (Bethe-Bloch dE/dx, the dominant mechanism), multiple scattering, bremsstrahlung, and pair production.

The existing PhysicsList.cc already implements exactly this configuration — no code changes needed. Confirm to proceed to Phase 3 (particle source).

User

Jun 2, 2026, 02:27

need hadronic physics process

Assistant

Jun 2, 2026, 02:27 (deepseek/deepseek-v4-pro)

For muon simulations, hadronic processes cover secondary particle production (neutrons, protons, pions from nuclear reactions). I’ll use the modular approach — keeping G4EmStandardPhysics_option4 for EM and adding hadronic builders:

Assistant

Jun 2, 2026, 02:27 (deepseek/deepseek-v4-pro)

Build passes. Phase 2 update:

Assistant

Jun 2, 2026, 02:27 (deepseek/deepseek-v4-pro)

Confirm to proceed to Phase 3 (1 GeV muon source from above the scintillator).

User

Jun 2, 2026, 02:28

hadronic process can be low precision

Assistant

Jun 2, 2026, 02:28 (deepseek/deepseek-v4-pro)

Switched hadronic from FTFP_BERT → QGSP_BERT (faster, lower precision). Build passes.

Now Phase 3: 1 GeV muon source from above. Per your spec: - Particle: μ⁻ (muon) - Energy: 1 GeV, mono-energetic - Position: center above scintillator at (0, 0, 2.6 cm) — 1 cm above the top surface (scintillator half-height is 2.5 cm, so top is at +2.5 cm; 1 cm above = +3.5 cm from center) - Direction: straight down (0, 0, -1) - Beam spot: 10×10 cm² area — uniform distribution in XY

Wait, let me re-read the spec: “从中心正上方 (10x10cm, 距离闪烁体 1cm)” — this means the muon source is a 10×10 cm² area positioned 1 cm above the scintillator surface. So the source is a square plane at z = +3.5 cm (scintillator top at +2.5 cm, plus 1 cm), with X and Y uniformly distributed over [-5, +5] cm.

Let me implement this in PrimaryGeneratorAction.

Assistant

Jun 2, 2026, 02:29 (deepseek/deepseek-v4-pro)

Phase 3 done. Source configuration:

Now Phase 4: Energy deposit recording. I’ll use G4AnalysisManager to create a histogram of energy deposition per event and write it to a ROOT file. This needs changes in SteppingAction (accumulate per-step edep), EventAction (fill histogram at end of event), and RunAction (open/close output file).

Assistant

Jun 2, 2026, 02:29 (deepseek/deepseek-v4-pro)

First, update RunAction to manage the analysis output:

Assistant

Jun 2, 2026, 02:29 (deepseek/deepseek-v4-pro)

Now update SteppingAction to accumulate energy deposit in the scintillator:

Assistant

Jun 2, 2026, 02:29 (deepseek/deepseek-v4-pro)

Build passes. Let me create a run macro and update TODO.md:

Assistant

Jun 2, 2026, 02:30 (deepseek/deepseek-v4-pro)

Phase 4 implementation:

Run with: ./build/g4 run.mac

Assistant

Jun 2, 2026, 02:30 (deepseek/deepseek-v4-pro)

Now Phase 5: Analysis & Landau fit.

Assistant

Jun 2, 2026, 02:30 (deepseek/deepseek-v4-pro)

The requirements are clear. I’ll generate a ROOT C++ macro for the Landau fit analysis:

Assistant

Jun 2, 2026, 02:31 (deepseek/deepseek-v4-pro)

All 5 phases complete. Here’s the final project summary:

Simulation

                    μ⁻ 1 GeV
                    (0,0,-1)
                       ↓
  z=3.5cm ─ ─ ─ ─ ─ ─ ─ ─ ┐ 10×10 cm² source plane
            air             │ (1 cm gap)
  z=2.5cm ╔═══════════════╗ ┘
          ║   NaI(Tl)     ║ 5 cm
  z=-2.5cm╚═══════════════╝
              20×20 cm²

How to Run

# 1. Run simulation (10000 events)
./build/g4 run.mac

# 2. Fit energy deposit with Landau
root -l -q fit_edep.C

# 3. View plot
open edep_landau_fit.png

Key Files

User

Jun 2, 2026, 02:33

Warning in : fit range is outside histogram range, no fit data for xaxis Warning in : Fit data is empty

Assistant

Jun 2, 2026, 02:33 (deepseek/deepseek-v4-pro)

Two issues: the energy loss for a 1 GeV muon through 5 cm NaI is ~30 MeV, far exceeding the 0-5 MeV histogram range. Let me fix both the simulation and the fit macro.

Assistant

Jun 2, 2026, 02:34 (deepseek/deepseek-v4-pro)

Now fix the fit macro:

Assistant

Jun 2, 2026, 02:34 (deepseek/deepseek-v4-pro)

Fixed two issues:

1. Histogram range: 0-5 MeV → 0-50 MeV (expected energy loss for 1 GeV μ⁻ through 5 cm NaI is ~27 MeV)
2. Fit macro: Fixed fit range to 5-50 MeV (was auto-detecting from bin content, which failed); added empty-histogram guard

Re-run:

./build/g4 run.mac && root -l -q fit_edep.C

User

Jun 2, 2026, 02:34

The following tool was executed by the user

User

Jun 2, 2026, 02:35

The following tool was executed by the user

User

Jun 2, 2026, 02:35

proceed, generate report

Assistant

Jun 2, 2026, 02:36 (deepseek/deepseek-v4-pro)

Analysis report generated at ANALYSIS_REPORT.md. Here’s the final summary:

Results

The MPV of 22.7 MeV corresponds to ~1.24 MeV·cm²/g dE/dx in NaI — consistent with a minimum-ionizing muon. The Landau fit quality (χ²/ndf ≈ 2.8) is typical for this absorber thickness; the Vavilov distribution would be more precise for the 18.3 g/cm² mass thickness.

Project Files