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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?

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lhc the unbelievable in pursuit of the unimaginable

LHC: the unbelievable in pursuit of the unimaginable

Kajari Mazumdar

Department of Experimental High Energy Physics

Tata Institute of Fundamental Research



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
          • ?

What lies within…?


The probe wavelength should be smaller than the distance scale to be probed: l<< h/p = hc/E

(1 TeV = 1012 electronVolt

= 1.6 * 10 -7 Joule)


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!


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.



Standard Model (SM) of Particle Physics as of today

  • 4 types of basic forces :
  • Gravitational, Weak, Electromagnetic, Strong.
  • 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!

Relative strengths:

10 -40: 10 -5: 10-2: 1

  • 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 yetseen have to hunt it out in experiment.ef==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.

LHC is an exploratory, high energy, high intensity machine which can produce heavy particles of mass upto few TeV.

Need accelerators for high energy in a controlled fashion in the laboratory.

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.

TIFR, Mumbai is preparing to host one of the GRID computing centres for regional scientists

Typical LHC Event


About 25 faculty,

20 students from India

at present


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)


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.