# What is the smallest distance between a decaying vertex and an interaction point a detector can measure?

A short lived particle is created at the interaction point and then decaying a distance $d$ away, in some detector. My question is what is the smallest distance $d$ that can be measured experimentally? Of course it will be different from a detector to another.

Any links that explain how this analysis, of discovering a particle, is done experimentally would be appreciated.

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As a rough guide, for the ATLAS detector the resolution is of the order $10\mu m$. It's also possible to resolve the vertex displacement in the longtitudinal direction alone, in the case that there's only one charged particle track to extrapolate backwards. In this case the resolution is about an order of magnitude worse.