Feynman Diagram Studio Guide

Guide/Your first diagram

Practical start

Your first diagram

Build e⁻e⁺ → μ⁻μ⁺ from a blank page, add particle and momentum labels, and export a vector figure for a paper or slide.

A Feynman diagram consists of vertices joined by propagator lines. Draw the geometry first, then assign line styles, arrows, and labels.

Orientation

Know the workspace

Left

Library

Your saved browser projects and every object in the active diagram. Select an object here if a crowded canvas makes clicking difficult.

Center

Canvas

The white drawing page and the four tool buttons. The page uses a 720 × 480 coordinate system and scales to the available screen.

Right

Inspector

Controls for the current tool or selected object. Figure-wide settings appear here when you enable the Figure Style panel.

Choose File → New Blank Diagram or select ＋ New blank diagram. The editor creates a local project named “Untitled diagram.” Click the title above the canvas to rename it.

Starting points

File → Starting point offers thirteen editable diagrams, including Compton scattering, vacuum polarization, scalar vertex functions, and a two-field loop. Loading a template creates an editable copy.

Walkthrough

Build e⁻e⁺ → μ⁻μ⁺

Electron positron annihilation diagramAn electron and positron enter from the left, annihilate into a virtual photon, then produce a muon and antimuon on the right. e⁻e⁺μ⁻μ⁺γ* incoming stateoutgoing stateinternal line
One tree-level contribution to e⁻e⁺ → μ⁻μ⁺ in quantum electrodynamics. The asterisk marks an off-shell internal photon.

Add four external vertices

Press A. In the inspector, choose None for the vertex icon. Click twice near the left edge and twice near the right edge.

Add two interaction vertices

Stay in the Vertex tool, switch the icon to Dot, and click at the center-left and center-right. Press V and drag any vertex to adjust its position.

Connect the incoming electron

Press C, choose Fermion, then click the upper-left endpoint followed by the first interaction vertex. The click order establishes the start-to-end direction.

Connect the incoming positron

Create another fermion line from the lower-left endpoint to the first interaction vertex. Select the line and set Arrow direction to End → start.

Add the internal photon

With the Connect tool active, choose Photon. Click the two interaction vertices. Photon lines have no arrow.

Add the outgoing muons

Choose Fermion again. Connect the second interaction vertex to each right endpoint. Keep the μ⁻ arrow start-to-end and reverse the μ⁺ arrow.

Write the labels

Press V, select each propagator, and enter e^{-}, e^{+}, \mu^{-}, \mu^{+}, or \gamma in Label (TeX).

Move labels away from lines

Drag a label on the canvas. For exact placement, change Label offset, Label X, or Label Y in the inspector.

Add a momentum arrow

Select the photon propagator and enable Momentum arrow. Enter q in Momentum label (TeX), then set the direction and side. The arrow follows the propagator, including its curvature.

Add an independent label

Open Annotate, choose Label, and click an empty part of the page. Replace the default text with \mathrm{annihilation}. Drag the label to position it.

The editor reference explains alternative line styles, curves, loops, vertex markers, and quark bundles.

Finish

Align and export

  1. Open View and keep Snap to Grid enabled. Choose fine, standard, or coarse spacing.
  2. Open Edit → Figure Style. Set the physical width, line width, and text size for the destination document.
  3. Select Export…, choose SVG, and enable transparency if the figure will sit on a colored background.
  4. Select Save as well. The .feynman.json file retains editable objects; an SVG does not.

SVG works well for browsers, slides, and vector editors. PDF suits print workflows. The export guide compares every format and LaTeX dialect.

Quick fixes

Common problems

Selecting a line

Press V. Click near the middle of the propagator or choose it from Objects in the left panel.

Reversing an arrow

Select the propagator and change Arrow direction. The momentum-arrow direction has its own control.

Raw TeX in a label

Use a supported command and omit math delimiters. Enter \gamma; the label field already uses math notation.

Undoing a change

Press ⌘Z on macOS or Ctrl+Z elsewhere. Add Shift to redo.