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Top Comments: Matter Particle Has Different Mass from Its Antimatter Partner [1]

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Date: 2023-04-23  

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Last week, I reported on an unsuccessful attempt to find a flaw in the Standard Model for particle physics by testing how spherical the electron is. This week came a report on the neutral charm meson, which like only a few other massive particles, can oscillate between its matter and antimatter partners.

For background, a meson is a short-lived quantum particle that consists of a quark and an antiquark. According to the Standard Model, there are three generations of quarks. The first generation—lowest in energy, and the quarks that make up protons and neutron in ordinary matter—consists of the “up” and “down” quarks (as well as their antiquarks). The second generation, higher in energy, consists of the “strange” and “charm” quarks (and their antiquarks); the third generation, highest in energy, consists of the “top” and “bottom” quarks (and their antiquarks). You can make a meson by pairing any one of the quarks with any of the antiquarks. See the link above for further details.

The neutral charm meson consists of a charm quark and an up antiquark, while its antiparticle consists of a charm antiquark and an up quark. The neutral charm meson is one of only a few material particles that can oscillate between its matter and antimatter forms. (The others are also mesons.) A matter particle and its antimatter partner should have the same energy and the same mass, according to the Standard Model. Oscillation between the two comes from the existence of what’s called a superposition state consisting of equal amplitudes of the matter and antimatter particles. (Schrödinger’s cat is an example of a superposition state, consisting of equal parts of the “alive” state and “dead” state.)

Physicists at Oxford performed an analysis of a large amount of data on the neutral charm meson produced by the LHCb experiment at the Large Hadron Collider at CERN, and discovered that the masses of matter and antimatter forms of the neutral charm meson are not the same—they are different by just 1x10-38 gram. This is a very small difference, but the Standard Model predicts that there should be no difference.

So this provides evidence that the Standard Model, as all physicists expect, is not entirely correct. Now theorists have the challenge of trying to figure out what’s causing this difference. It may provide insights into why the universe contains only matter and very little antimatter, an observation that is also in conflict with the Standard Model.

Comments are below the fold.

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