Pseudoscalar meson

In high-energy physics, a pseudoscalar meson is a meson with total spin 0 and odd parity (usually noted as JP=0−). Compare to scalar meson.

The pseudoscalar mesons consisting of up, down, and strange quarks only form a nonet

Pseudoscalar mesons are commonly seen in proton-proton scattering and proton-antiproton annihilation. The pion was first proposed to exist by Yukawa in the 1930s as the primary force carrying boson of the Yukawa Potential in nuclear interactions, and was later observed at nearly the same mass that he originally predicted for it. In the 1950s and 1960s, the pseudoscalar mesons began to proliferate, and were eventually organized into a multiplet according to Murray Gell-Mann's so-called "Eightfold Way".

Gell-Mann further predicted the existence of a ninth resonance in the pseudoscalar multiplet, which he originally called X. Indeed, this particle was later found and is now known as the eta prime meson. The structure of the pseudoscalar meson multiplet, and also the ground state baryon multiplets, led Gell-Mann (and Zweig, independently) to create the well known quark model.

Among all of the mesons known to exist, the pseudoscalars are perhaps the most well known in a sense. The masses of the pion, kaon, eta and eta prime particles are known with great precision. However, the decay properties of the pseudoscalar mesons, particularly of eta and eta prime, are somewhat contradictory to the mass hierarchy. While the eta prime meson is much more massive than the eta meson, the eta meson is thought to contain a larger component of strange and anti-strange quarks than the eta prime meson, which appears contradictory. The presence of an eta(1405) state also brings glueball mixing into the discussion. It is possible that the eta and eta prime mesons mix with the pseudoscalar glueball which should occur, in its pure state, somewhere above the scalar glueball in mass. This is one of a few ways in which the unexpectedly large eta prime mass of 957.78 MeV/c2 can be explained, relative to its model-predicted mass around 250 to 300 MeV/c2.

Examples
gollark: I don't think you can *in general*, but you'll probably know in some cases what the content might be. Lots of network protocols and such include checksums and headers and defined formats, which can be validated, and English text could be detected.
gollark: But having access to several orders of magnitude of computing power than exists on Earth, and quantum computers (which can break the hard problems involved in all widely used asymmetric stuff) would.
gollark: Like how in theory on arbitrarily big numbers the fastest way to do multiplication is with some insane thing involving lots of Fourier transforms, but on averagely sized numbers it isn't very helpful.
gollark: It's entirely possible that the P = NP thing could be entirely irrelevant to breaking encryption, actually, as it might not provide a faster/more computationally efficient algorithm for key sizes which are in use.
gollark: Well, that would be inconvenient.

See also
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.