The ordinary matter is made up of fermions and these fermions interact via vector bosons(spin 1). The fermions can be further classified on the basis of interactions they take part in.
There are 4 kind of interactions we have in nature (which we have found so far):
| Force(Interaction) | particle (responsible for interaction) | spin of particle |
|---|---|---|
| Electromagnetic | photon | 1 |
| strong force | gluon | 1 |
| weak force | \(W^{+}\),\(W^{-}\), Z | 1 |
| Gravitation | graviton (not yet observed) | 2 |
The weight of universe is mostly due to dark energy (67%), dark matter (27%) and ordinary matter (5%). The ordinary matter is what we, earth, sun, and stars are made up of. The ordinary matter consist of atoms of different atomic numbers. All atoms are made up of nucleus and electrons around them. The electrons does not contribute much to weight of universe as they are least massive particle (except neutrinos). It turns out that most of mass of atom comes from neutrons and proton. Here \(M_{proton} \approx 1836 \times M_{electron}\).
From deep inelastic scattering experiments, we know that protons and neutrons are not fundamental particles, hence these could be themselves made up some fundamental particles. Later on it turns out that the protons and neutrons are made up of quarks and antiquarks.
In fact there are infinite number of quarks and antiquarks inside protons and neutrons , but all keeps on appearing and disappearing but three of the quarks remains. So we say that the neutrons and quarks are made up of 3 quarks. Now these quarks are not just one kind of...
It turns out that, the quarks exist in 2 kinds and 3 generation of each kinds. In total we say that the quarks come in 6 flavours.
| count | quark name | generation | charge | spin | mass |
|---|---|---|---|---|---|
| 1 | up (u) | 1 | +2/3 | 1/2 | 2.2±0.4 MeV/c² |
| 2 | down (d) | 1 | -1/3 | 1/2 | 4.7±0.5 MeV/c² |
| 3 | Charm (c) | 2 | +2/3 | 1/2 | 1.27±0.03 GeV/c² |
| 4 | Strange (s) | 2 | -1/3 | 1/2 | 95±5 MeV/c² |
| 5 | top (t) | 3 | +2/3 | 1/2 | 173.21±0.51 GeV/c² |
| 6 | bottom (b) | 3 | -1/3 | 1/2 | 4.18±0.03 GeV/c² |
Note that the mass of top quark is heavy than the gold atom.
Now how can the 3 quarks with same spin exist inside proton and neutron, what about Pauli exclusion principle (which state that no two fermions can be in same state). The state of fermions is defined by all possible quantum numbers(flavour quantum number, spin quantum number, charge, lepton number). These quantum numbers are also termed as degree of freedom of particle (as the range of values of these quantum numbers defines the d.o.f of the particle).
The particle \(\Delta^{++}\) consist of uuu, and it is supposed that all the three up quarks are in same state, to get out the dilemma (possible violation of Pauli exclusion principle), 0 . W. Greenberg proposed that the quarks also have extra quantum number (degree of freedom), a color charge with 3 degree of freedom in color space(R(Red),G(Green),B(Blue)).
The most weight of ordinary matter is due to weight of protons and neutrons, and the weight of neutrons and protons comes form sum of quarks which neutrons and protons consist of.
The proton is bound state of uud quarks, and the neutron is bound state of udd quarks.
The sum of the individual quarks is roughly around 10 MeV(2.2+2.2+4.7 MeV for uud and 2.2+4.7+4.7 MeV) but the actual weight of uud is 1000 MeV. So from where the additional mass comes from?????
The extra mass of neutrons and proton comes from the energy of the system (uud or udd). The mass is basically the energy content of object. That was essence of Einstein's energy mass equivalence.
The quarks are interacting with each other via strong interactions. Unlike the spreading electric fields of two opposite or same charges, the strong interaction flux remains in very thin flux tube called as strings.
My job is to find the string tension of the quark antiquark pair in background of so many quarks composed of 2 light quark (up or down, considering them of same mass), and one heavy quark (strange quark). The background of these quarks generates some temperature. I need to find the string tension at varying temperatures. Temperatures will also be increased to the limit that the quark and anti quarks exist as individual free particles.