Why is mass uncertain in case of Heisenberg Principle?

Feb 2017
I read that for Higgs Boson Heisenberg Uncertainty Principle applies. But why is mass uncertain in case of short lived unstable particle? That being said the momentum is uncertain which tells us that the position is known. Is the position known by measuring the Higgs Bump? Is the velocity also known for the Higgs Bosons?
Jun 2016
The Heisenberg found his principle as an inescapable consequence of the mathematical description of quantum particles.
It has since been demonstrated experimentally (many times).

It is frequently confused with a similar problem regarding the measurement of quantum particles
(you cannot measure a quantum system without affecting the system being measured).

I think with your "Higgs Bump" you are introducing a third confusion.
The CERN result showing the existence of the Higgs Boson is obtained by (statistically) combining millions of experimental results.
The consequence of averaging lots of results is that the random noise tends to cancel out, but consistent signals don't cancel and so stand out from the noise.
However measurement accuracy will mean that the signals will not all be exactly at the same spot, hence a bump (rather than a spike).
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Apr 2015
Somerset, England
Why is mass uncertain in case of Heisenberg Principle?
As Woody has indicated, there are at least two forms of uncertainty,

Uncertainty inherent in a measurement process such as the minimum length a light microscope will resolve.
Sometimes measurement uncertainty can be circumvented by using a different measurement method eg an electron microscope.

And uncertainty inherent in the mathematical model in use.
Heisenberg uncertainty is of this second type.
Unfortunately, you can't get round this by simply using a different formula for your mathematical model as this would imply that one model contradicts another and they can't both be right.
Heisenberg uncertainty involves momentum and hence mass.

However, again as Woody has indicated, there is yet another quantity involved here. Experimental error.
Experimental error can be eliminated in theory by a perfect experiment.
But finding a perfect experiment would result in the biggest Nobel prize of all time.
The best we have ever been able to do it make lots of repeat experiments and take an average.