How do you know these particles actually exist?

In other words, a particle exists in at least two different positions simultaneously.

All particles exist in states that may be characterized by a certain energy, momentum and mass.

Thus we have experimental evidence that virtual particles exist and have real effects.

When R is all of 3d position space, the integral must be 1 if the particle exists.

According to the quantum philosophy, particles like electrons don't exist as points of mass and charge.

By next summer, they said, they will have enough data to say finally whether the elusive particle really exists.

This leads to an inevitable question: Does the particle even exist?

This implies, then, that the particle exists in every possible position.

The longer the virtual particle exists, the closer its characteristics come to those of ordinary particles.