Question Matter Antimatter collisions in a Quantum World

[Ray Gunn]

According to quantum theory, when not observed, particles such as electrons and positrons exist not at precise points in space but rather as spread-out "clouds" of probable positions. And yet, an electron and positron will collide and annihilate as if they exist as discrete point-like particles.

Why instead do they not collide when their "clouds" of probable position overlap?

 

[Dratonia]

According to quantum theory, when not observed, particles such as electrons and positrons exist not at precise points in space but rather as spread-out "clouds" of probable positions. And yet, an electron and positron will collide and annihilate as if they exist as discrete point-like particles.

Why instead do they not collide when their "clouds" of probable position overlap?

They probably do, but since it is not being observed, there is no noticeable difference.

 

[billslugg]

All particles exist as particles and as wave functions. When scientists calculate the probability of collision they use a "collision cross section" for each particle. It varies by the energy of each particle and is equal to that area within which, to some very high probability, the particle will be found. The units of that cross section are "barns" as in "the side of a barn" and are equal to 10^-28 square meters.

 

[iconoclast]

According to quantum theory, when not observed, particles such as electrons and positrons exist not at precise points in space but rather as spread-out "clouds" of probable positions. And yet, an electron and positron will collide and annihilate as if they exist as discrete point-like particles.

Why instead do they not collide when their "clouds" of probable position overlap?

They do "collide" when their clouds get close and overlap. And don't forget the the Uncertainty Principle.