Support

Answers to the questions that come back, and how to reach us.

Frequently asked questions

The analysis says “no vertex … in model” although my diagram is right

One leg is read the wrong way: with the direction of time on, a fermion line whose arrow runs backwards in time is an antiparticle. Select the leg and tick Antiparticle, or move its end to the other side of the vertex. The message lists the vertices of the model sharing most of the fields: it is almost always the one you meant.

“diagram is not connected”

A leg or a line ends near a vertex without being attached to it. With the Line tool, release on the vertex (a snap zone surrounds it); with the Vertex tool, a vertex dropped on the free end of a leg connects to it.

The result is infinite or “nan”

A propagator is evaluated exactly on its pole: √s equal to the mass of a boson with no declared width, or a massless propagator at zero momentum. Declare a width (width) in the model or shift the energy slightly.

The total cross section diverges (Bhabha, Compton)

That is the Coulomb pole of the t-channel exchange: use the |cos θ| ≤ c cut of the Compute tab.

Only one of my diagrams seems to count

The summed diagrams are those that are checked, valid, and of the same process as the current one; legs drawn in another order are renumbered automatically. The Compute tab lists the excluded diagrams with the reason.

Formulas do not show

KaTeX rendering goes through a web view. If a “Formula rendering unavailable” badge appears, close and reopen the document; if it persists, report it with your macOS or Windows version.

Can I load a FeynRules (.fr) model?

Not directly: export it to UFO from FeynRules, then import the UFO folder into TreeLevel (folder button of the Model box). MSSM_SLHA2 imports completely.

Are my documents and models sent anywhere?

No. TreeLevel collects and transmits no data; see the Privacy page.

Reporting a problem

For a bug or a physics error, write to info@pasahome.org with, if possible:

• the .feyndiag document concerned (it contains the theory and the diagrams);
• the TreeLevel version (TreeLevel › About) and the macOS, iPadOS or Windows version;
• the result you got and the one you expected, with its source.

You can also go through TreeLevel's page on the Mac App Store (“Support”). On Windows: TreeLevel's page on the Microsoft Store.

Compatibility

macOS 14 Sonoma or later, Apple silicon and Intel; iPadOS 17 or later (universal purchase). Windows 10 (2004) or later and Windows 11, x64 and ARM64, 35 CHF (Microsoft Store, separate purchase). Interface in eleven languages.