Meson
In particle physics, mesons (/ˈmiːzɒnz/ or /ˈmɛzɒnz/) are hadronic subatomic particles composed of one quark and one antiquark, bound together by the strong interaction. Because mesons are composed of sub-particles, they have a physical size, with a diameter of roughly one fermi, which is about 2⁄3 the size of a proton or neutron. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond. Charged mesons decay (sometimes through intermediate particles) to form electrons and neutrinos. Uncharged mesons may decay to photons.
Mesons are not produced by radioactive decay, but appear in nature only as short-lived products of very high-energy interactions in matter, between particles made of quarks. In cosmic ray interactions, for example, such particles are ordinary protons and neutrons. Mesons are also frequently produced artificially in high-energy particle accelerators that collide protons, anti-protons, or other particles.
In nature, the importance of lighter mesons is that they are the associated quantum-field particles that transmit the nuclear force, in the same way that photons are the particles that transmit the electromagnetic force. The higher energy (more massive) mesons were created momentarily in the Big Bang, but are not thought to play a role in nature today. However, such particles are regularly created in experiments, in order to understand the nature of the heavier types of quark that compose the heavier mesons.
Eta meson
The eta (η) and eta prime meson (η′) are mesons made of a mixture of up, down and strange quarks and their antiquarks. The charmed eta meson (η
c) and bottom eta meson (η
b) are forms of quarkonium; they have the same spin and parity as the light eta but are made of charm quarks and bottom quarks respectively. The top quark is too heavy to form a similar meson, due to its very fast decay.
General
The eta was discovered in pion-nucleon collisions at the Bevatron in 1961 by A. Pevsner et al. at a time when the proposal of the Eightfold Way was leading to predictions and discoveries of new particles from symmetry considerations.
The difference between the mass of the η and that of the η' is larger than the quark model can naturally explain. This " η-η' puzzle" can be resolved by the 't Hooft instanton mechanism, whose 1/N realization is also known as Witten-Veneziano mechanism.
Quark composition
The η particles belong to the "pseudo-scalar" nonet of mesons which have spin J = 0 and negative parity, and η and η′ have zero total isospin, I, and zero strangeness and hypercharge. Each quark which appears in an η particle is accompanied by its antiquark (the particle overall is "flavourless") and all the main quantum numbers are zero.
Pion
In particle physics, a pion (or a pi meson, denoted with the Greek letter pi: π) is any of three subatomic particles: π0, π+, and π−. Each pion consists of a quark and an antiquark and is therefore a meson. Pions are the lightest mesons (and, more generally, the lightest hadrons), because they are composed of the lightest quarks (the u and d quarks). They are unstable, with the charged pions π+ and π− decaying with a mean lifetime of 26 nanoseconds (6992260000000000000♠2.6×10−8 seconds), and the neutral pion π0 decaying with a much shorter lifetime of 6983840000000000000♠8.4×10−17 seconds. Charged pions most often decay into muons and muon neutrinos, and neutral pions into gamma rays.
The exchange of virtual pions, along with the vector, rho and omega mesons, provides an explanation for the residual strong force between nucleons. Pions are not produced in radioactive decay, but are produced commonly in high energy accelerators in collisions between hadrons. All types of pions are also produced in natural processes when high energy cosmic ray protons and other hadronic cosmic ray components interact with matter in the Earth's atmosphere. Recently, detection of characteristic gamma rays originating from decay of neutral pions in two supernova remnant stars has shown that pions are produced copiously in supernovas, most probably in conjunction with production of high energy protons that are detected on Earth as cosmic rays.
Podcasts:
Meson
ALBUMS
- Schematics for Power, Volume 1 released: 2003
-
by Mason
-
by Mason
-
by Mason
-
by Mason
-
by Mason
-
by Mason
-
by Mason
-
by Mhisani
-
by Mhisani
-
by Mhisani
-
by Mysonne
-
by Mysonne
-
by Mysonne
-
by Mysonne
-
by Maesion
-
by Maesion
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Muzion
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
-
by Mission
It's Time For Turkey And No It's Not Thanksgiving
by: MasonParty lifestyles of the Warehouse and Co. Saving lives
before it was cool, that's all you need to know. Baby,
baby, I'd miss you more if you could speak. Baby, baby,
baby talk dirty to me or you won't ever be able to come
back to us.. Water?
I still got pictures of you, they read like a trainwreck
and stereo instructions. You've derailed. The off button
is to the left right next to you. You? On 3 we attack.
Immature is a word that describes 16 year old girls. You
were supposed to be beautiful.
I don't want to be associated with any of the letters
that could represent your name 'The babiest deer under a
baby blue sky'... Immature is a word that describes 16