Quarks colour and quarks confinement.

Quarks colour

The problem associated with the idea that baryons are composed of quarks is that two or three same type of quarks are contain in a particular particle for example two u quarks in proton and three s quarks in 𝝮⁻ baryons violates the exclusion principle. Quarks must follow exclusion principle because they are fermions and have half integral spin (1/2). To solve this problem, it was considered that quarks have an additional property called colours and its possibilities are red, green and blue. The antiquark colours are antired, antigreen and antiblue.

According to colour hypothesis, each baryon consist of three quarks of different colours which satisfies the exclusion principle, since all quarks have different states even if two or three particles are identical, such combination is thought to be white. The antibaryon is made of antired, antigreen and antiblue quarks.

The meson is consist of quark of one colour and an antiquark of corresponding anticolour and thus cancelling the effect of colours. Thus the hadrons and antihadrons are colourless.

On deeper level, strong interactions are based on quark colour as the electromagnetic interactions are based on electric charge.

Proton and antiproton.

Neutron and antineutron.

Quarks confinement

Quarks confinement means we cannot isolate quarks.

Explanation of quarks confinement is based on the idea that, as quarks are connected by spring, the attractive force between two quarks increase with increase in their distance. Thus more energy is needed to isolate quark particles. But with enough energy quarks instead of seperating produces a quark antiquark pair, which result in a meson that escapes.

For example when an energetic 𝛾 photon reacts with neutron having composition udd as shown in figure causes a uū quark antiquark pair to come into existence. The udd + uū rearranges to form a proton (uud) and a negative π meson, the reaction is given as

Quarks confinement.

Comments

Mass defect, packing fraction and binding energy.

Mass defect, packing fraction and binding energy: It was assumed that mass of the nucleus is equal to the mass of its constituents (i.e protons and neutrons). But experimentally it was found that the actual mass of the nucleus is less than the theoretical mass. Thus, the difference between the theoretical mass and experimental mass is called mass defect i.e ∆m={[Zmₚ + (A-Z)mₙ] - M} Where mₚ= mass of proton mₙ= mass of neutron M= actual mass of nucleus Z= atomic number A= mass number The ratio of mass defect and mass number (A) is called packing fraction (f) f = ∆m/A Thus packing fraction is the mass defect available per nucleon. The packing fraction explains the stability of the nucleus. The packing fraction may be positive, negative or zero. The positive value of packing fract...

Different kinds of beta decay.

Different kinds of beta decay 1) Negative beta decay process: When there is excess number of neutrons in the nucleus, the neutron is converted into proton with the emission of electron and antineutrino particle and this process is called negative beta decay process. Negative beta decay. 2) Positive beta decay process: When there is excess number of protons in the nucleus, the proton is converted into neutron with the emission of positron and neutrino particle and this process is called positive beta decay process. Positive beta decay. 3) Electron Capture: When there is excess number of protons in the nucleus, sometimes the nucleus will absorbed the nearby electrons in the nearest electron orbital emitting neutron and a neutrino and this process is called electron capture. Electron capture. 4) Inverse beta decay: Inverse beta decay. Thus such kind of reaction in which neutrinos are absorbed to create some sort of beta decay is called inverse beta decay. Inverse beta decay confirm t...

Beta decay

Beta decay; Beta decay is a spontaneous radioactive decay process in which either a neutron gets converted into proton or a proton gets converted into neutron with the emission of electron or positron respectively. Whenever proton or neutron are in higher energy level because they are in excess they get converted into another kind of particle and thus decreasing the energy of the system and increasing its stability. In ¹²B there are seven neutrons and five protons while in ¹²C there are six neutrons and six protons, since both protons and neutrons are fermions and no more than two same kind of fermions can occupy the given energy level. Thus the figure below shows the nuclear energy diagram of ¹²C and ¹²B. Since in ¹²B nucleus, there are two neutrons present in excess, if a neutron gets converted in proton, then this new proton occupies an energy level lesser in energy than that of neutron and thus giving a stable ¹²C nucleus. Pauli theory of beta decay; An interesting historical ...

Modern Physics

Search This Blog