Charm quark charge

That the charm quark charge is 2/3 is also borne out by the size of the increase in the ratio R (see Fig. 14.1) on crossing the charm threshold (i.e. much bigger than would be the case for a Q = 1/3 quark). 

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). 

Today cheurm particles are produced in abundance and their properties are discussed in Chapters 11-13. It is by now an experimentally well established fact that the charm quark has charge 2/3. This leads to a second quark doublet... 

Given the uncertainties in the experimental calibration one sees that the measured values of R are in reasonable agreement with a scheme based on coloured quarks with the usual fractional charges, and with the existence of a heavy lepton. Note too that the data is compatible with the charge assignment Qc = for the charm quark. 

We have repeatedly remarked that the assmnption that the charm quark has electric charge 2/3 makes it the natural candidate to be the missing... 

In contrast to the charm case, the bottom quark charge assignment Qh = —1/3 comes from the moderate increase of R above the b threshold. This assignment is confirmed by the charge of the B ub). 

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 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. 

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. 

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. 

Prom the CERN SppS colliders we have a limit on a possible second generation of gauge vector bosons (CHARM, 1989) Mz > 280 GeV. No squark or gaugino (i.e. the supersymmetric partners of quarks and gauge vectors) below 100 GeV have been found nor have any heavy stable charged particles been seen at the 1.8 Tevatron by CDF (CDF, 1989). No fourth quark generation (i.e. no 6 ) is found by DELPHI at LEP 1 below 44 GeV in the decay of the Z (DELPHI, 1990). A summary of the situation can be found in Dydak (1991). 

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. 

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