LHC: the unbelievable in pursuit of the unimaginable
Kajari Mazumdar
Department of Experimental High Energy Physics
Tata Institute of Fundamental Research
Mumbai
Eternal Questions
What principles govern energy, matter, space
and time at the most elementary level?
• What is the world made up of?
• How does it work?
High Energy Physics tries to answer them all!
92 Elements
 Atoms
 Nuclei (and Electrons)
?
 protons & neutrons
 quarks
?
Tool
What lies within…?
The probe wavelength should be smaller than
the distance scale to be probed: l<< h/p = hc/E
x 
E
(1 TeV = 1012 electronVolt
= 1.6 * 10 -7 Joule)
1 mm  104 eV
2
1 nm  10 eV
10
20
13
m  10 eV
 10 TeV
LHC is the Biggest and most
Expensive Science Experiment
ever attempted
Price Tag:
US $ 9.1 billion
No of scientists: 8000+
8.6 Km
Technological progress
pushes frontiers of basic
science research and there
are important spin offs.
Eg. World Wide Web!
Working Principle of a
Collider Machine
What will happen in LHC
Mammoth detectors will register signals
Cosmic Recipe: How we understand the universe
• LHC takes us back in time towards the beginning of the universe!
at an epoch of 10-12 sec. after the big bang.
•Earlier experiments have probed the prevailing situation upto a time
t ≈ 10-10 s, when the world was as hot as 1015 K
•Protons and neutrons formed around: t ≈ 10-4 s, 1013 K
•Nuclei are formed after t = 3 minutes, 109 K
(equivalent energy density ~0.1 MeV, distance scale ~10-12 m)
•Today: t = 14 Billion years since the beginning, 3 K
Present wisdom: Behaviour of matter particles can be explained in
terms of very few fundamental interactions, which might have
evolved over time as the universe cooled down from a single unified
one.
GRAND UNIFIED THEORY!
Standard Model (SM) of Particle Physics as of today
• 4 types of basic forces :
Gravitational, Weak, Electromagnetic, Strong.
Relative strengths:
10 -40: 10 -5: 10-2: 1
• And 2 types of fundamental particles :
(i) fermions (matter particles like electron, quarks)
(ii) bosons (carrier particles, like photon)
• Almost all the predictions of SM match very well, till date, with
experimental observations.SM is still not a satisfactory Theory!
• One of the most disturbing fault of our understanding as of today, is,
we can’t explain the origin and the mass patterns of particles.
• Theoretically, in an unified description, massless particles can be
described very well.
• But, in nature, we do encounter mass of elementary particles.
Introduction of mass in the theory causes complications!
We got to unravel the mystery of mass!
Most plausible: all fundamental particles acquire mass by interacting
with an all pervading field, as a consequence, this idea also evokes
another fundamental particle, the Higgs Boson!
Higgs particle not yet seen have to hunt it out in experiment. e
f==a
Strategy: Heavy particles (by nature unstable) of interesting
properties should show up if enough energy is gathered to produce
them. (E=mc2). They were produced, existed when universe was hot.
Need accelerators for high energy in a controlled fashion in the
laboratory.
LHC is an exploratory, high energy, high intensity machine which can
produce heavy particles of mass upto few TeV.
The primary goal of the LHC is to find the Higgs boson…
… if it isn’t found, to find out why it isn’t there!
Most sophisticated and
complex detectors with size of
big buildings.
Unprecedented computing
challenge to be met by GRID
technology.
Typical LHC Event
TIFR, Mumbai is preparing to
host one of the GRID
computing centres for regional
scientists
About 25 faculty,
20 students from India
at present
Installation of detector components built in India (2006)
LHC Timeline
 First LHC studies were done in 1982
 Project was approved in 1994 ; final decision in 1996
 Construction started in 2002
 First beams sent around the storage ring: September 10, 2008
 Helium leak caused by electric short-circuit delayed start
 Official inauguration: October 21, 2008
 First collisions will start around summer 2009
 By October 2009 collision energy should reach 10 TeV
 Energy upgrade to 14 TeV by mid 2010
 Higgs boson discovery (?) by 2012
Several Indian groups working for LHC accelerator and experiments
for last 10-12 years.
Interesting factoids about LHC:
• LHC when running will consume as much power as a medium-sized
European town
• LHC budget is comparable to the GDP of a small country, e.g. Fiji or
Mongolia
• LHC vacuum is 100 times more tenuous then the medium in
which typical communications satellites move
• LHC magnetic fields of 8.4 Tesla are 100,000 times the Earth’s
• LHC magnets will use 700,000 litres of liquid Helium and
12,000,000 litres of liquid Nitrogen
• LHC protons will have energies comparable to that of a flying
mosquito
• LHC optical grid at 1.5 Gb/s could eventually make the Internet 300
times faster
Extra Dimensions: String theory with Radical ideas!
• Different particles and forces are just different oscillation modes
of tiny strings, of length ~ 10-33 cm.
• Instead of usual 3 spatial dimensions, there may be additional
ones, which are curled up too small to be observed!
• Gravity may appear weak only because its force is being shared
with (or leaks into) other spatial dimensions.
Or, LHC may produce almost 10 Million completely harmless Micro
Quantum Black Holes per year!
The Black Hole will disappear within 10 -25 sec after creation due to
Hawking Radiation!
No threat whatsoever of any kind.
What do we expect the LHC to find?
Many good reasons to discover Higgs boson and more
For the rest…
Like asking what a new continent is going to be like
when we can just glimpse the shore….
Four possible scenarios
(J. Bagger et al hep-ex/0007022)
There is always the possibility that one
may find something really exotic….
THANK YOU
TransPlanckian phenomenon:
Laboratory Black Holes
S.B. Giddings, S. Thomas, PRL 65 (2002) 056010
S. Dimopoulos, G. Landsberg, PRL 87 (2001) 161602
Hawking radiation
Black Hole production
In large extra dimensions Schwarzchild
radius of proton increases from 10-33 to 10-17 cm
If the impact parameter
of two colliding protons
is smaller than this
distance, they coalesce
into a micro blackhole .
It evaporates, via
Hawking radiation,
within 10-25 s spewing
out many particles
isotropically in the
detector.