Feynman Diagram (SVG)

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    </marker>
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  <style>
    .fermion { stroke: #0f172a; stroke-width: 2; fill: none; }
    .photon  { stroke: #1f47f5; stroke-width: 1.8; fill: none; }
    .lbl     { font: 13px Inter; fill: #0f172a; }
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  <!-- incoming electron -->
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  <!-- outgoing electron -->
  <line class="fermion" x1="180" y1="120" x2="60"  y2="180"/>
  <!-- internal electron propagator -->
  <line class="fermion" x1="180" y1="120" x2="280" y2="120" marker-end="url(#arr)"/>
  <!-- internal continued -->
  <line class="fermion" x1="280" y1="120" x2="400" y2="60"/>
  <line class="fermion" x1="280" y1="120" x2="400" y2="180"/>
  <!-- incoming photon -->
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        transform="translate(0,-40) rotate(-45 180 120)"/>
  <!-- outgoing photon -->
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        transform="translate(0,-40) rotate(45 280 120)"/>
  <!-- vertices -->
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  <circle cx="280" cy="120" r="4" fill="#dc2626"/>
  <g class="lbl">
    <text x="40" y="55">e⁻</text>
    <text x="40" y="195">e⁻</text>
    <text x="410" y="55">e⁻</text>
    <text x="410" y="195">e⁻</text>
    <text x="125" y="65" fill="#1f47f5">γ</text>
    <text x="320" y="65" fill="#1f47f5">γ</text>
    <text x="225" y="135" font-size="11" fill="#475569">e⁻</text>
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  <text x="230" y="225" font-family="Inter" font-size="12" text-anchor="middle" fill="#475569">Compton scattering: e⁻ + γ → e⁻ + γ</text>
</svg>