What is Particle Physics
The Universe is a remarkable place, full of wonder on scales
large, small, and in between. The very large and the very
small are scientifically tied together…. Particle physicists
and cosmologists, astrophysicists are all trying to find the
solution to the same puzzle : our universe – its history and
its future
About Scales in universe
Particle Physics is the study of the fundamental building blocks of nature at the
level of ultimate deconstruction. It tries to understand the nature of time and
space, forces and energy, how the universe evolved into its present form and what
is its future.
There is also radiation :
Electromagnetic waves, photons,
 - rays, x-rays etc…..
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Important Units
Energy:
1 electron volt (eV) = 1.6  1019 C 
1 keV = 103 eV
1 MeV = 106 eV
1 GeV = 109 eV
1 TeV = 1012 eV
1 PeV = 1015 eV
1 V = 1.6  1019 J
103 eV = 1 meV
106 eV = 1 (micro) eV
109 eV = 1 nano-eV
1012 eV = 1 pico-eV
1015 eV = 1 femto-eV
From E= mc2, Mass: 1 eV/c2 = 1.78 ×10−36 kg; c = 3 × 108 m/s
Momentum: 1 eV/c = 5.34×10−28 kg⋅m/s
From [eV] = [kBT] where kB = Boltzmann’s constant
= 1.3806488(13)×10−23 J/K = 8.6173324(78)×10−5 eV/K
Temp : eV/kB= 11600 K/eV
h= Planck’s constant= 6.626070040(81)×10−34 Js = 4.135667662(25)×10−15
eVs ; ℏ = h/2 = 6.58×10−16 eVs
Value of ħc = 0.197 eVm
>1026 m Radius of observable universe
1024 m Distance to the nearest large supercluster
1021 m Diameter of the disc of the Milky Way
1017 m Distance from Earth to Vega
1013 m Diameter of solar system
1.5  1011 m Distance between Earth and Sun
109 m Diameter of the Sun
107 m North Pole to equator
Image credit: 2dFGRS,
SDSS, Millenium
Simulation/MPA
Garching, and Gerard
Lemson & the Virgo
Consortium.
3  108 m/s  107 s/yr ~ 1015/16 m  I light yr
1 parsec = 3.26 light yr
300K ~0.025 eV
kT ~ E
The Large Hadron Collider (LHC); a time machine
From 8 TeV to close to 14 TeV in 2015
Particle physicists try to
study the interactions by
replicating the energetic
conditions of the earlier
universe by accelerating
particles and colliding them
and study the results with
a fine “tooth-comb”, thus
understanding what really
happened way back when
…..
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LHCb
Blunt extrapolation for 2011
CMS
LHC ring at CERN:
27 km circumference
ALICE
So far:
Now 13 TeV proton—proton collisions
In 2015
ATLAS
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The cosmic pie chart
Nothing is not nothing, it is
something: vacuum energy;
Quantum fluctuations
Heisenberg’s uncertainty principle : et < h
Matter-antimatter asymmetry
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An aerial view of CERN
The accelerator complex is built
upon a number of inter-dependent
accelerators. The oldest, the
Proton Synchrotron (PS), built in
the 1950s was briefly the world's
highest energy accelerator (28
GeV), operation in 1959.
CERN accelerator complex
The Super Proton Synchrotron (SPS), built in
the 1970s, started in 1976 at 350 GeV beam
energy, was the scene of CERN's first Nobel
prize in the 1980s. The Large ElectronPositron collider (LEP) came alive in 1989.
Built in a circular underground tunnel, it was
27 km in circumference. The Large Hadron
Collider (LHC), a proton-proton collider,
under operation now, is housed in the same
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tunnel.
An Overview of Special Relativity
From Griffith, Chapter 3
Einstein: Space-time are related, we live in a 4-dimensional universe
Rotation of a vector:
The vector remains unchanged, but each component
changes.
Likewise three space dimensions and one time
dimension are related in simple relativity, which
usually does not manifest in ordinary lives because v
<< c, or v/c << 1
The relativistic factor is known as  (gamma) and
Here,  = v/c
Note: the smallest value of  is 1,
and is independent of the sign of v
Lorentz Transformation :
S
S’
y’ = y
z’ = z
And, likewise, transformation
from S’ to S frame
S and S’ are inertial frames.
x =  (x’  vt’)
t =  (t’  vx’)
Einstein’s postulates:
1. Physics laws remain invariant in all inertial reference frames (one
frame moving at constant velocity w.r.t another). [Frame S’ is
moving w.r.t S with a velocity v along positive x-axis, but frame S is
moving w.r.t S’ with a velocity –v along (negative) x-axis.]
2. The velocity of light measured is c in all inertial frames.
Show the film clip
The length x is at rest measured in inertial frame S, x’ is how it would
be observed from the inertial frame S’ moving w.r.t frame S. This could
be the length of a rod L resting in frame S, then it would appear shrunk
in frame S’ by the factor . This is known as length contraction.
Likewise, if a rod of length L’ is at rest in frame S’, it would appear shrunk in the frame S w.r.t
which S’ (and the rod is moving).
A clock tick is a bit more tricky, because if the time difference between each second tick gets
lengthened, the difference between two events will be in shorter time interval, in essence
the clock slowing down when observed from a moving reference frame.
So
Here, t’ is the time interval between two events taking place in S’, as
seen from frame S, and the time t is the time interval where the clock
measuring it is at rest. This is known as time dilation.
Of critical importance is to recognize in which system the object is at rest, and in which
system the measurement is made.