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. 2

Important Units

3  10 8 m/s  10 7 s/yr ~ 10 15/16 m  I light yr 1 parsec = 3.26 light yr Image credit: 2dFGRS, SDSS, Millenium Simulation/MPA Garching, and Gerard Lemson & the Virgo Consortium. >10 26 m Radius of observable universe m Distance to the nearest large supercluster m Diameter of the disc of the Milky Way m Distance from Earth to Vega m Diameter of solar system 1.5  m Distance between Earth and Sun 10 9 m Diameter of the Sun 10 7 m North Pole to equator

300K ~0.025 eV kT ~ E

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 ….. 6 The Large Hadron Collider (LHC); a time machine

7 Blunt extrapolation for 2011 CMS LHCb ALICE ATLAS

Nothing is not nothing, it is something: vacuum energy; Quantum fluctuations Heisenberg’s uncertainty principle :  e  t < h The cosmic pie chart 8 Matter-antimatter asymmetry

An aerial view of CERN CERN accelerator complex 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 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 Electron- Positron collider (LEP) came alive in 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 tunnel. 9

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

S S’ Lorentz Transformation : y’ = y z’ = z And, likewise, transformation from S’ to S frame x =  (x’  vt’) t =  (t’  vx’) S and S’ are inertial frames. 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.