3.36 Sspd_chapter 1_part 13_ asymmetrical universe

SSPD_Chapter 1_Part 13_continued_Asymmetric Universe

1.13.4. WHY WE HAVE UNIVERSE MADE OF MATTER AND NOT ANTI_MATTER

Before Hubble’s discovery (1929) of expanding Universe, it was sacredly held that matter is constant and conservation of matter holds good. Universe was suppose to be static and unchanging.

In 1928, P.A.M.Dirac successfully reconciled Quantum Mechanics and Special Theory of Relativity in his relativistic Wave Equation. This predicted the existence of anti-particle. It gave the correct value of the magnetic moment of electron. In May 1931, Dirac postulated an anti-particle in a following manner,” a hole, if there were one, would be entirely a new kind of particle, unknown to experimental physics, having the same mass but opposite charge of electron.” This was a bold assertion. In 1932 the anti-particle of electron was discovered by C.D.Anderson in Cosmic Rays. This was positron. This was not proton. E.Seagre, O.Chamberlain and their colleagues produced anti-proton in High Energy Labs in 1955.

After that a series of anti-particle was discovered namely anti-proton , anti-neutron and mesons. It became difficult to classify mesons- are they particle or antiparticle. Now we know that they are admixtures of particle and anti-particle depending upon the composition of a doublet as already discussed in Chapter 1_Part13_constituent particles.. Rewriting Eq.1.125 we get

Through C harge conjugation, P arity inversion and T ime reversal we get the following anti-particle of positive K meson. To maintain CPT symmetry, existence of K ⁺ Meson and Anti-K ⁺ Meson or K ^- Meson is a physical reality.

These discoveries changed the basic law of conservation of matter. Today ant-particles and anti-atoms are being routinely created in High Energy Particle accelerators.

According to Dirac, there is a symmetry between particle and anti-particle. And this requires continuous creation and annihilation of matter and anti-matter.

e + anti e ↔ 2γ (soft gamma photons)

p + anti p ↔ 2γ (hard gamma photons)

After the Big Bang, both matter and anti-matter were created in equal amount. Somewhere down the path of evolution. Matter was favoured over anti-Matter. This led to the conservation of :

(Baryon-antiBaryon)/(no. of energy quanta) = Baryonic Number

And conservation of:

(Lepton- antiLepton)/(no. of energy quanta)=Leptonic Number.

Thus the Law of Conservation of Matter was replaced by “symmetry of matter and anti-matter” and “conservation of Baryon Number and Lepton Number”.