Particle physics


A high overview of the Standard Model of elementary particles

This model provides an overview of all most fundamental building blocks of matter and energy.
Protons and neutrons are made up of quarks. From that level on we can conceive various higher order levels at which these building blocks are organized. Atoms consist of protons, neutron and electrons. Molecules consist of atoms. Macroscopic chuncks of matter are made up of atoms and molecules.

For the quarks to interact to make up particles like protons we need forces. In this model three forces are distinguished which manifest themselves through the exchange of particles between the quarks. These carrier particles mediate the forces between the quarks.
The diagram above contains a coupling matrix in which is shown for which matter particles the various carrier particles are mediating the corresponding forces.

Higgs boson
The Higgs boson is actually a rather new member in this model.
Its existence has been suspected for several decades to find an explanation for the fact that many particles have mass and inertia. Until then the fundamental theoretical frameworks failed to provide a satisfactory explanation. This question became urgent because the W± and Z0 bosons which are the carriers for the weak nuclear force were supposed to be massless according to the Standard Model. But experiments told us they were not massless. Mathematical frameworks, to describe in detail the interaction between the various fundamental entities, have contributed to the suspicion that there must be some kind of scalar field through which particles can acquire mass. The strategy to find experimental evidence of the existence of this scalar field was to find a way to detect the excitations of this field. These excitations manifest themselves as bosons, the field carriers, the particles you can detect. At July 4 2012 the existence of the boson, named Higgs boson, was demonstrated. The boson is named after Peter Higgs, a prominent theoretical physicist who came with a theoretical framework to describe how elementary particles acquire mass.

Graviton ?
The graviton, the mediating particle for gravitaional interaction is left out in this model. The quantum field theory to provide some evidence for the existence for such a particle is still in its infancy. Gravity is very accurately described with Einstein's General Theory of Relativity. According to this theory energy and mass curve space and time, and because of that fact, influencing the movements of objects in their vicinity. This theory is a continuous and deterministic theory which seems hard to reconcile with a quantum theory on gravity with its probabilistic descriptions of reality in which discrete quantum states are distinguished.

There are six kinds of quarks, in the scientific community they are called flavours. So there are six flavors:
up (u)
down (d)
charm (c)
strange (s)
top (t)
bottom (b)
The common concepts used in particle physics:
Fermions: particles which have spin number = (2n+1)½
Bosons: particles which have spin number = n (integer)
Hadrons: particles which are made up of quarks
Baryons: particles which are made up of three quarks like protons and neutrons
Mesons: particles which which are made up of an equal number of quarks and anti-quarks


Lepton neutrino's
The lepton neutrino's are represented by the small white squares. Their rest energy is still subject for research and debate. Their positions along the energy axis depicts their upper limit values according to current estimations.

Decay paths of quarks
The arrows between the small squares representing the quarks are depicting the decay paths. There are bold, dotted and thin arrows. The bold arrows are representing the most likely decay path and the thin arrows the least likely.
During the decay of a quark to another kind of quark, a quark transformation, a lepton and a neutrino are emitted. But since the weak force governs this decay process, W± and Z0 bosons are involved to mediate this weak interaction.

Some remarks about the weak nuclear force
The mediation process differs from the mediation process regarding strong nuclear and electro-magnetic force. In the latter massless gluons and photons are exchanged to mediate the forces. In the case of the weak interaction a W± or a Z0 boson is actually emitted by the decaying quark. Within 10-25 seconds this boson decays into a lepton and a neutrino. This boson appears to be very heavy which is consistent with the very short range of the weak interaction (about 10-17 m), but it was a mystery how such a boson could acquire so much mass.
(see the paragraph above about the Higgs boson to learn more)

Lifetime of quarks
The lifetimes of the t, b, c, and s quarks are extremely short, between 10-25 and 10-8 seconds. The lifetime of the d quark is 900 seconds.
The u quark is the most stable one. Its lifetime has not been determined.

Lifetime of a proton
The quark configuration of a proton is "uud". The d quark with its 900 seconds of lifetime is kept stable within and because of this configuration. The lifetime of a proton has not been determined but is assumed to be finite by some scientists. According to theoretical calulations the upper limit for its lifetime is 6 x 1039 years.

Rest energy (proton) = rest energy (the three constituent quarks) + binding energy from gluons
The rest energy of a proton is 938 MeV.
The combined rest energy of the two "up" quarks and one "down" quark, the proton is consisting of, amounts to 9.40 MeV, which is 10 times less than the rest energy of the proton. This illustrates the fact that the gluons, which are responsible for binding the three quarks, represents 90% of the proton's rest energy.

The rest energy of a neutron is 939.37 MeV. Also in this case the binding energy is responsible for 90% of the total rest energy.




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