Charm, bottom and top

Not so long ago it seemed clear that the underlying symmetry group of strong interactions was SU(3) and that all hadrons could be constructed 

The most natural way to enlarge C to include hadrons is to extend the gauge invariance plus spontaneous symmetry breaking prescription to include quark fields q = (u, d, s) in an analogous fashion to the leptons but taking account of the Cabibbo mixing of d and s. 

One of the most interesting outcomes of gauge theory is the impossibility of making a reasonable model using just three quarks within the conventional Cabibbo current approach. Gauge theories require a larger group than SU(3) for hadrons. At the simplest level we require one new quark, the charm quark c. 

Already at a phenomenological level, in the language of an effective current-current Lagrangian, one can see the need for a fourth quark. 

In the current-current approach we have a parallelism between the leptonic doublets (e-)l (/u-)l quark doublet involving 

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Protons and neutrons each contain three quarks. A neutron consists of one up quark and two down quarks. A proton consists of two up quarks and one down quark. Other quarks are named strange, charm, bottom, and top., but these four are not part of atoms. Quarks are a fundamental constituent of matter according to current standard model of particle physics, but individual quarks are not seen. Instead they are always confined within other subatomic particles. There is no need to consider quarks when describing chemical interactions. Only electrons are involved in chemical reactions. The position and sizes of these particles in a helium atom is indicated in the diagram at right. A diagram... 

Many subatomic particles have been identified. Leptons and quarks are the elementary particles of matter. The electron is a lepton. Protons and neutrons are made of quarks. There are six types of quarks that differ in mass and charge. They are named up, down, strange, charm, bottom, and top. Protons consist of two up quarks and one down quark, and neutrons consist of two down quarks and one up quark. Although individual quarks have not been isolated, their existence explains the patterns of nuclear binding and decay. 

Quarks come in six different types, or flavors up and down, top and bottom, and charm and strange. Protons and neutrons are made of up (u) quarks (which have a charge of + ) and down (d) quarks (which have a charge of — g). A proton is made from two u quarks (+ )(+1) and one d quark (— g), giving a total charge of +1. A neutron contains one u quark (+ ) and two d quarks (—g)(—g) for a total charge of zero. 

Nuclei that are found in nature consist of nucleons (protons and neutrons) which themselves are made of u (up) and d (down) quarks. However, there also exist s (strange) quarks and even heavier flavors, called charm, bottom, top. The latter has just recently been discovered. Let us stick to the s quarks. They are foimd in the strange relatives of the nucleons, the so-called hyperons A, S, a, i2). The yl-particle, e.g., consists of one u, d and s quark, the S-particle even of an u and two s quarks, while the (sss) contains strange quarks only. Figure 8.19 gives an overview of the baryons, which are of interest here, and their quark content. 

The extension of the periodic system into the sectors hypermatter (strangeness) and antimatter is of general and astrophysical importance. Indeed, microseconds after the big bang the new dimensions of the periodic system, we have touched upon, certainly have been populated in the course of the baryo- and nucleo-genesis. Of course, for the creation of the universe, even higher dimensional extensions (charm, bottom, top) come into play, which we did not pursue here. It is an open question, how the depopulation (the decay) of these sectors influences the distribution of elements of our world today. Our conception of the world will certainly gain a lot through the clarification of these questions. 

Chemistry is the central science in the sense that it provides the tie between physics on the one hand and biology on the other. The world of physics, seen broadly, covers a wide spectrum. In general, the concerns of physics focus on entities smaller or larger than those of direct interest to chemistry. At the micro level physics unravels the mysteries of the elementary particles, known generally as fermions, which constimte all ordinary matter. Fermions include the quarks and their antiparticles, the antiquarks. There are six kinds of quarks, known as top, bottom, strange, charm,... 

Quark a fundamental particle hypothesized to form the basic building blocks of all matter there are six different quark types up, down, strange, charm, top, and bottom... 

There are six quarks and they have the whimsical names up, down, charm, strange, top, and bottom. As shown in Table 1, quarks have a fraction of a charge, either+2/3 or-1/3. 

Quarks were first identified by observing the products formed in high-energy nuclear collisions. Six types of quarks are recognized. Each quark type is known as a flavor. The six flavors are up, down, top, bottom, strange, and charm. Only two of these—the up and down quarks—compose protons and neutrons. A proton is made up of two up quarks and one down quark, while a neutron consists of one up quark and two down quarks. The other four types of quarks exist only in unstable particles that spontaneously break down during a fraction of a second. 

The well-known proton, neutron, and electron are now thought to be members of a group that includes other fundamental particles that have been discovered or hypothesized by physicists. These very elemental particles, of which all matter is made, are now thought to belong to one of two families namely, quarks or leptons. Each of these two families consists of six particles. Also, there are four different force carriers that lead to interactions between particles. The six members or flavors of the quark family are called up, charm, top, down, strange, and bottom. The force carriers for the quarks are the gluon and the photon. The six members of the lepton family are the e neutrino, the mu neutrino, the tau neutrino, the electron, the muon particle, and the tau particle. The force carriers for these are the w boson and the z boson. Furthermore, it appears that each of these particles has an anti-particle that has an opposite electrical charge from the above particles. 

The six quarks, namely the up quark (u), the down quark (d), the strange quark (s), the charm quark (c), the top quark (t), sometimes also called truth quark, and the bottom quark (b), also dubbed beauty quark, carry a colour charge. The bosons that act on colour, are called gluons, which are the carriers of the colour interaction. The residue of this interaction is the strong nuclear interaction, which is operative between the hadrons (for instance the proton and the neutron within an atomic nucleus). 

The second family in Table 10.2 contains the "heavy electron", the muon and the muon neutrino, and the charm and the strange quarks. The third family contains the tau particle, the tau electron, and the two quarks referred to as top (or truth) and bottom (or beauty). These quarks can only be produced in high energy particle reactions. 

In this zoo of particles, only the electron, which was discovered even before the atomic theory was proven and the atomic structure was known, is really unseeable, stable, and isolatable. The proton also is stable and isolatable, but it is made up of two quarks up (with charge -1-2/3) and one quark down (with charge —1/3). As for the quarks, while expected to be stable, they have not been isolated. The other particle constitutive of the atomic nucleus, the neutron, is also made up of three quarks, one up and two down, but it is not stable when isolated, decaying into a proton, an electron, and an antineutrino (with a 15-min lifetime). The fermions in each of the higher two classes of the electron family (muon and tau) and of the two quark families (strange charmed and bottom/top) are unstable (and not isolatable for the quarks). Only the elusive neutrinos in the three classes, which were postulated to ensure conservation laws in weak interaction processes, are also considered as being unseeable, stable, and isolatable. 

Quarks are the fundamental particles that make up protons and neutrons, as well as several other types of particles. There are six types of quarks, which are referred to as different flavors. These are named up, down, top, bottom, charm, and strange. Protons and neutrons are each made up of three quarks. Two up and one down quark make up a proton. Two down and one up quark make up a neutron. 

The same convenient representation of hadronic states in terms of quark and antiquark hues will be carried over to the new sector of heavy quarks (charm c, bottom or beauty b, top f,...). 

The subject of heavy flavours has e3q>anded tremendously in recent years stretching from the static properties (mainly spectroscopy, i.e. energy levels, lifetimes, branching ratios, decays, mixing etc.) of hadrons with one or more heavy quarks, e.g. bottom or charm, to more dynamical properties (like fragmentation, structure functions, jets etc.) and on to more exotic topics, e.g. production and decay of as yet undiscovered flavours like top, or speculations on a fourth generation or imphcations on Higgs or on non-standard effects and so on. 

Note that we do not consider any fundamental component of c, b or t quarks in the nucleon. Their presence, in the form of qq pairs, is better thought of as a dynamic effect arising from pair production from gluons (see Fig. 16.10), i.e. a QCD effect, and will be treated in Section 23.8. This means that the formulae for the scaling functions to be presented in this section require additional contributions to be added to them when the kinematics is such as to allow charm or bottom production. Given present estimates of the top mass the production of top is not a relevant consideration. 

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