کتاب الکترونیکی سی. پی.اچ
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نظریه سی. پی.اچ
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Hadrons are particles made from quarks and/or gluons, bound together by their strong interactions. Hadrons have no net strong charge (or color charge) but they do have residual strong interactions due to their color-charged substructure. Many types of hadrons were discovered in the 50's and 60's. The idea of the quarks was first proposed to explain the many observed hadrons. There are two classes of hadrons: baryons and mesons. باریونها
Hadrons are particles made from quarks and/or gluons, bound together by their strong interactions.
Hadrons have no net strong charge (or color charge) but they do have residual strong interactions due to their color-charged substructure. Many types of hadrons were discovered in the 50's and 60's. The idea of the quarks was first proposed to explain the many observed hadrons. There are two classes of hadrons: baryons and mesons.
باریونها
Baryons are particles made from a basic structure of three quarks (and anti-baryons from three antiquarks.) Baryons carry an odd half quantum unit of angular momentum (spin) and, hence, are fermions, which means that they obey the Pauli Exclusion Principle rules.
Baryons are particles made from a basic structure of three quarks (and anti-baryons from three antiquarks.)
Baryons carry an odd half quantum unit of angular momentum (spin) and, hence, are fermions, which means that they obey the Pauli Exclusion Principle rules.
Sample Fermionic Hadrons Baryons () and Anti-baryon ()
The proton is the only baryon that is stable in isolation. Its basic structure is two up quarks and one down quark. Neutrons are also baryons. Although neutrons are not stable in isolation, they can be stable inside certain nuclei. A neutron's basic structure is two down quarks and one up quarks. More massive baryons may be made from any set of three quarks. Baryons containing more massive quarks are all unstable because these quarks decay via weak interactions. There are also more massive baryons that have the same quark content as a proton or a neutron but have additional angular momentum. These are typically very short-lived because they can decay to a proton or a neutron and a meson via residual strong interactions. مزونها
The proton is the only baryon that is stable in isolation. Its basic structure is two up quarks and one down quark. Neutrons are also baryons. Although neutrons are not stable in isolation, they can be stable inside certain nuclei. A neutron's basic structure is two down quarks and one up quarks.
More massive baryons may be made from any set of three quarks. Baryons containing more massive quarks are all unstable because these quarks decay via weak interactions. There are also more massive baryons that have the same quark content as a proton or a neutron but have additional angular momentum. These are typically very short-lived because they can decay to a proton or a neutron and a meson via residual strong interactions.
مزونها
Mesons are color-neutral particles with a basic structure of one quark and one antiquark. There are no stable mesons. Mesons have integer (or zero) units of spin, and hence are bosons, which means that they do not obey Pauli exclusion principle rules.
Sample Bosonic Hadrons Mesons ()
The most common mesons are:
Pions (or pi mesons), made from up and down type quarks and antiquarks only (for example, a pi-plus meson is a u and an anti-d quark). K mesons, which contain one u or d type quark or antiquark and one s type (for example K-plus is a u and an anti-s quark).
Pions (or pi mesons), made from up and down type quarks and antiquarks only (for example, a pi-plus meson is a u and an anti-d quark).
K mesons, which contain one u or d type quark or antiquark and one s type (for example K-plus is a u and an anti-s quark).
These are the only types of mesons which are long-lived enough to be seen directly by their tracks in a detector. More massive mesons with the same quark content but higher angular momentum, as well as others containing one or more of the more massive quark types, are all very short lived. They have been found by studies of their decay products, but they decay too quickly to leave a track that can be detected. Particles that contain the more massive quark types, for example B, D, or Nc particles decay via weak interactions slowly enough that their production can be inferred from the fact that the decay product tracks emerge from a vertex point outside the beam collision region. Vertex detectors are precision tracking devices designed chiefly to detect such decay vertex points. ساختمان مختلط
These are the only types of mesons which are long-lived enough to be seen directly by their tracks in a detector.
More massive mesons with the same quark content but higher angular momentum, as well as others containing one or more of the more massive quark types, are all very short lived. They have been found by studies of their decay products, but they decay too quickly to leave a track that can be detected.
Particles that contain the more massive quark types, for example B, D, or Nc particles decay via weak interactions slowly enough that their production can be inferred from the fact that the decay product tracks emerge from a vertex point outside the beam collision region. Vertex detectors are precision tracking devices designed chiefly to detect such decay vertex points.
ساختمان مختلط
The quarks inside a meson or baryon are continually interacting with one another via the strong force field. At any instant in time, they may contain many virtual particles: gluons and additional quark-antiquark pairs. The picture of a proton as made of three quarks is thus a gross simplification. For example, we know from measurements that in a high-momentum proton only about half the momentum is carried by quarks, the rest is carried by gluons. گلئوبالها
The quarks inside a meson or baryon are continually interacting with one another via the strong force field. At any instant in time, they may contain many virtual particles: gluons and additional quark-antiquark pairs.
The picture of a proton as made of three quarks is thus a gross simplification. For example, we know from measurements that in a high-momentum proton only about half the momentum is carried by quarks, the rest is carried by gluons.
گلئوبالها
Theoretically, there are additional types of hadrons that have a basic structure that is made purely from gluons. These are called glueballs. Such particles do contain virtual quark-antiquark pairs, at least some of the time, so it is very difficult to find an experimental signature that can distinguish such a particle from an ordinary meson. There are, however, some observed particles that are thought to be chiefly glueball-like.
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