p comes in our mind, what happened to the

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1.Introduction
The
Big Bang Theory is the leading explanation about the formation

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of Universe. it says that
universe is started with a small singularity,

then inflated over the next
13.8 billion years to the cosmos that
we
know today. We all know that equal amount of matter and
antimatter
have
been created during the big bang, as beleived by Scientists. But what
we
are seeing today that everything on Earth from the smallest life to
the
largest
stellar objects is made almost entirely of matter. Comparatively,
there
is not much antimatter to be found. Here is the question comes in our
mind,
what happened to the antimatter, or why we see matter/antimatter
asymmetry
Ref. 1.
Antimatter
particles have same mass as their matter counterparts but
opposite
charge. For example positron(positively charged electron) is the
antiparticle
to the negatively charged electron. Matter and antimatter par-
ticles
are always produced in pair and if they come in contact, they
annihilate
with
one another with producing energy. so if matter and antimatter are
created
and destroyed together then universe should contain nothing, but
this
is not the case. In the preceding few decades, scientists have
learned
fron
particle physics experiments that the laws of nature do not equally
ap-
plicable
to matter and antimatter. Sakharov showed that the Universe can
initially
start off with exactly the same amount of matter and antimatter,
but
then develop into a state that which has more of one than the other
if
three
conditions are satisfied.
2.Sakharov
Conditions
In
1967, Andrei Sakharov described three minimum properties of Nature
which
explains why there is dominance of matter over antimatter Ref. 2.

Baryon number violation

Baryon
number is violated. Baryon number is the sum of the number of
protons
and neutrons of an object. Essentially, this counts how much matter
there
is.

C and CP violation

Charge
conjugation symmetry, C, and Charge conjugation times Parity, CP,
are
both violated. These essentially allow the theory to distinguish
between
matter
and antimatter.

The Universe is out of
thermal equilibrium. This means that there is a

direction
of time that is measurable microscopically. If the Universe was
always
in thermal equilibrium, the processes that create matter over anti-
matter
would occur at exactly the same rate as the processes that create
antimatter
over matter.
In
this article I am focussing on the second property i.e CP violation.
3.What
is CP violation
There
are symmetries in our universe. For example : Sunflowers boast radial
symmetry
and an interesting type of numerical symmetry known as the
Fibonacci
sequence, Most animals have bilateral symmetrywhich means that
they
can be split into two matching halves, if they are evenly divided
down
a
center line, humans possess bilateral symmetry and some scientists
believe
that
a persons symmetry is the most important factor in whether we find
them
physically beautiful or not, There are around 5,000 types of orb web
spiders,
and all create nearly perfect circular webs with almost equidistant
radial
supports coming out of the middle and a spiral woven to catch prey
e.t.c.
In physics, Symmetry exists when a system remains unchanged after
a
transformation i.e a transformation can be applied without changing
the
laws
of physics.
Now
let’s have a look on C, P and CP symmetry- C-symmetry is charge
conjugation
symmetry: it transforms a particle into its antiparticle or vice
versa.
P-symmetry is parity symmetry: it transforms everything into its
mirror
image, so left becomes right and vice versa. CP symmetry is a
composite
of C and P symmetry.
CP
Violation is the violaion of charge conjugation parity symmetry i.e.
when
we change a system by C symmetry or P symmetry then some de-
scriptions
of the system dont stay the same before and after the change.
4.CP
violation explains matter-antimatter asymmetry
Baryons
are made up of protons(three quark(uud)) and neutrons(dud) that
make
up all the matter in the universe. The LHCb (Large Hadron Collider
beauty)
experiment is one of several new experiments constructed at CERN,
which
will explore the decays of beauty (B) and charm (D) hadrons.
The
LHCb
experiment has found charge-aprity (CP) violation in baryons. CP

symmetry
is related to the idea that baryons made of matter behave

exactly
like antibaryons i.e. their antimatter counterparts.
Any
violation of this
symmetry
would imply that the laws of physics are not the same for matter
and
antimatter particles. A detailed understanding of how this symmetry
is
violated in nature can contribute to explaining the excess of matter
over
antimatter
observed in our universe, despite the fact that the Big Bang
should
have created equal amounts of matter and antimatter in the first
place.
The
Standard Model (SM) Ref. 3 of particle physics predicts that the
amount of

CP
violation exists in the baryon sector is very small. Although
CP-violating
processes have been studied for over 50 years, no significant
effects
had been seen with baryonic particles. Moreover, CP violation as
described
in the SM is not large enough to account for the much larger
matter-antimatter
unbalance. So one need to go beyond the SM to get the
large
amount of CP violation. Therefore, other CP violation sources must
contribute,
and the experiments held on LHCb is trying to search for
the
new sources of CP violation, one of the main goal of LHCb.

5.CP
Violation in Quark Sector
CP
violation was first discovered in decays of the K meson also known
as
the kaon. Experiments on investigation of CP violation in the strange
and
bottom quark sectors has been conducted over the past few decades
but
The measured asymmetries are are too small to explain the observed
matter-antimatter
asymmetry of the universe. In contrast to the strange and
bottom
quark sectors, CPV in the top quark sector is relatively unexplored.
The
top quark behaviour shows deviations as predicted by Standard Model.
3So
it plays an important role to search for new physics beyond the
standard
model.
In the SM, CP violation in the production and decay of top quark-
antiquark
pairs is predicted to be very small. so one need to go beyond the
SM
to test for CP violation. In many theories of physics beyond the SM
sizable
CP-violating effects could be observed, which have the potential to
shed
light on the matter-antimatter asymmetry of the Universe.
LHC(The
Large Hadron Collider), a particle accelerator under develop-
ment
by CERN, the world’s largest organization devoted to particle
physics,
is
conducting many experiments to test for CP violation in top quark
pair
both
at production and decay. In Ref. 4 it has been shown how CP
vioaltion
can
be tested in the process gg ? tt? ? (bl + ? l )( b?l ? ??
l ).
6.Summary
and Outlook
In
this article we have discussed about formation of Universe in brief
and
the
matter antimatter asymmetry in the Universe and how it could be un-
derstand
with the conditions given by Sakharov. Also, we had discuseed the
role
of CP violation in undersanding the mater antimatter asymmetry of
the
Universe and how much amount of CP violation is observed in quarks.
Apart
from this CP violation can also explain phenomenon like leptogenesis,
Baryogenesis,
Dark matter e.t.c.