Deborah & William Hillyard
Deborah & William Hillyard
Deborah & William Hillyard
Deborah & William Hillyard
Deborah & William Hillyard
Science - Sub-Atomic Particles
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| Particle Type | Quark Composition | Rest Mass in MeV |
| ? Pion (neutral) Pion (+ charge) Pion (- charge) |
(uu - dd) / 2 ud du |
135.0 139.6 139.6 |
| Rho (neutral) ? Rho (+ charge) Rho (- charge) |
(uu - dd) / 2 ud du |
775.5 775.4 775.4 |
| Omega (v) | (uu + dd) / 2 | 782.7 |
| Phi (f) | ss | 1,020.0 |
| D Meson Ds Meson |
cd cu cs |
1,869.4 1,864.6 1,969.0 |
| Psi (J/Y) | cc | 3,096.9 |
| B (+ve) B (neutral) B (strange) B (charmed) |
ub db sb cb |
5,279.2 5,279.5 5,366.3 6,276.0 |
| ? Upsilon | bb | 9,460.4 |
Mesons are unstable particles comprising a quark/antiquark pair, either of the same or different flavors. The table to the left shows some of the Mesons identified so far, their quark composition and approximate rest mass. Note the massive Upsilon particle that has a mass more than ten times that of the Proton. It is also interesting to refer to the estimated quark masses, and look at the correlation between those masses and the masses given in the Standard Model section. It is clear that in many particles, most of the mass derives not from the component quarks themselves, but from the mass equivalent of the energy derived from quark kinetic energy and from gluon energy.
Having integer spin, mesons are classed as bosons. This means that they can act as force mediating particles over short distances, and participate in processes such as the nuclear interaction. Mesons participate in both the weak and strong nuclear interactions, and charged Mesons participate in the electromagnetic interaction. Mesons are intrinsically unstable, but generally the more massive the particle, the more unstable it is. Mesons have been instrumental in many quark experiments; for example, the charm quark was first seen in the Psi meson in 1974, and the bottom quark in the upsilon meson in 1977.
Each meson has a corresponding antiparticle (antimeson) where quarks are replaced by their corresponding antiquarks and vice-versa.
Having integer spin, mesons are classed as bosons. This means that they can act as force mediating particles over short distances, and participate in processes such as the nuclear interaction. Mesons participate in both the weak and strong nuclear interactions, and charged Mesons participate in the electromagnetic interaction. Mesons are intrinsically unstable, but generally the more massive the particle, the more unstable it is. Mesons have been instrumental in many quark experiments; for example, the charm quark was first seen in the Psi meson in 1974, and the bottom quark in the upsilon meson in 1977.
Each meson has a corresponding antiparticle (antimeson) where quarks are replaced by their corresponding antiquarks and vice-versa.
Quark Summary
| 1st Generation | 2nd Generation | 3rd Generation | |
| "Up" Type Quarks |
Up Quark Mass: 1.5-4.0 MeV Charge: 2/3 Spin: 1/2 ID: u, u |
Charm Quark Mass: 1.16-1.5 GeV Charge: 2/3 Spin: 1/2 ID: c, c |
Top Quark Mass: 171-176 GeV Charge: 2/3 Spin: 1/2 ID: t, t |
| "Down" Type Quarks |
Down Quark Mass: 3.5-8.0 MeV Charge: -1/3 Spin: 1/2 ID: d, d |
Strange Quark Mass: 70-150 MeV Charge: -1/3 Spin: 1/2 ID: s, s |
Bottom Quark Mass: 4.2 or 4.68 GeV Charge: -1/3 Spin: 1/2 ID: b, b |
Mesons
| The Rho is considered an excited state of the Pion. Note the vastly different masses for the same Quark composition. |
| The combination of a bottom quark and an anti-bottom quark is also called, rather delightfully, Bottomonium! |
| No; I do not fully understand this either. Some sources quote either uu or dd. It appears to be an artifact of quark mass. |
