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Question Video: Arranging Subatomic Particles according to Their Masses Physics

Order the following particles according to their mass from least to greatest. Up quark, Charm quark, Top quark, Higgs boson, Electron.

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Video Transcript

Order the following particles according to their mass from least to greatest: up quark, charm quark, top quark, Higgs boson, electron.

On this list of particles, we have three quarks, one boson, and one lepton. So let’s start by comparing similar particles, that is, quarks to quarks, and then figure out where the Higgs boson and electron fit in. Recall that in the standard model quarks come in three pairs, often called generations. The up and down quark are the first generation. The charm and strange quark are the second generation. And the top and bottom quark are the third generation.

Ordered this way, each of the quarks in a particular generation have greater mass than the quarks in the preceding generations. So the charm and strange quarks of the second generation each have a greater mass than either the up or the down quark of the first generation. And the top and bottom quarks of the third generation each have a greater mass than the charm and strange quarks of the second generation and, in turn, also a greater mass than the up and down quarks of the first generation. So of up, charm, and top, we can clearly see that top has a greater mass than charm, which has a greater mass than up.

Now we just need to figure out where the Higgs boson and the electron fall on this list. Recall that the Higgs boson is actually the second most massive particle in the standard model, second only to the top quark. So on our list, the Higgs boson should go between the charm and the top quark. As for the electron, recall that the electron has about one two thousandths of the mass of a proton, which is a hadron, a composite particle made up of up and down quarks.

Even though only about one percent of the mass of the proton is due to the mass of its constituent quarks, the proton is so much more massive than the electron that it is still clear that the electron is lighter than any of the quarks that make up the proton. Since the proton is made up of quarks from the least massive generation, it’s clear then that the electron is less massive than all of the quarks and actually belongs at the beginning of our list. So our final list is electron with the least mass, then up quark, charm quark, Higgs boson, and finally top quark with the greatest mass.

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