Speaker
Description
Why is there something instead of nothing? Every particle in nature has it's corresponding antiparticle.In theory as well as in experiments it is seen that particle antiparticle always comes in pairs.Yet we only observe matter in our everyday environment.So does our universe fundamentally favours matter over antimatter?
Was this matter antimatter asymmetry present at the birth of the universe or did the universe developed it later.
To answer this question Andrei Sakharov in 1967 proposed following conditions necessary for breaking matter antimatter symmetry:
1. Baryon Number Violation: According to Grand Unified Theory baryon number is not conserved in integration of fermions with heavy GUT scale gauge and Higgs bosons.GUT tells us that the early universe had very high energy density that could lead to creation of heavy particles (leptoquarks)which could mediate B violation.
2.CP Violation:
Parity operator operates on the particle's wave function by reflecting all the vectors through origin which changes the handed-ness of the particle.For parity conservation both both left handed and right handed particles should decay with equal probability.
Charge conjugation operates on a particle to convert it into it's antiparticle.
If we apply both the operators on a right-handed particle it will result in a left-handed antiparticle.For CP to be conserved rate of RH particle should be equal to LH antiparticle.
In 1980 Val Fitch and Jim Cronin performed an experiment on K mesons which showed the CP violation.Since CP treats matter and antimatter differently so during early universe it must have enhanced the rate of conversion of antimatter to matter.
3.Thermal non equilibrium: In thermal equilibrium all the processes and their reverse have same rate but for matter to be dominating than antimatter it shall require thermal non equilibrium
Beyond the Standard Model:
1.The CP violation from weak forces accounts for a very small amount which is not enough to even leave matter for one galaxy. Could CP violation also be present in the strong interaction and if not then could there be some other hidden force beside the Standard Model responsible for the CP violation
2.Baryon number violation can exist in Grand Unified Theory but to check if GUT is possible in our universe we need to look for proton decay which is not supported in Standard Model
3.Leptogenesis: they are the scenarios where lepton number violation generated in heavy sterile neutrino produces baryon asymmetry
Experimental work is being done by Fermilab to detect difference in neutrino and antineutrino oscillations(morphing) which can provide a strong evidence for the Leptogenesis
| Session | Beyond the Standard Model |
|---|
