LHC, CMS and DHEP
Kajari Mazumdar
http://www.tifr.res.in/~mazumdar
Departmental Introduction, 2011
August 11, 2011
Eternal questions of mankind
•
What principles govern energy, matter, space
and time at the most elementary level?
•
•
•
•
What is the world made up of?
What is mass ?
Why there is no antimatter in the universe?
What is matter like within first seconds of the Big Bang?
Embarrasing situation in science: What is 96% of the Universe
made up of?
Symbiosis between Particle Physics, Astrophysics and Cosmology.
High Energy Physics: pushes back frontiers of
knowledge!
It also brings in technological spin-offs.
Our Universe ..... Important epochs
Energy =kT
Length scale = hc/E
1. Quantum gravity era: t≈ 10-43 s 1032 K
(1019 GeV, 10-34 m)
Big Bang
2. Grand Unification Era:
t ≈ 10-35 s 1027 K (1016 GeV, 10-32 m)
13.7 Billion Years
5. Today (3K)
1028 cm
3. Protons and neutrons formed:
t ≈ 10-4 s, 1013 K (1 GeV, 10-16 m)
•4. Nuclei are formed t = 3 minutes,
• 109 K (0.1 MeV, 10-12 m)
Big Bang
Length scales
Essential tool is microscope:
∆
x ﾻ
Proton
Atom
Radius of Earth
Earth to Sun
LHC
The probe wavelength
should be smaller than
the distance scale to be
probed:
Radius of Galaxies
Universe
Super-Microscope: probes physics of
t ~ 10 -12 s, E ~ 10 3 GeV = 1 TeV
1 TeV = 1012 electronVolt
= 1.6 * 10 -7 Joule
Presently, LHC provides energy upto 7 TeV,
equivalent to the kinetic energy of a fly!
20 years to plan, build ,
20 more to work with
h
E
cm
Hubble
AMS
ALMA
VLT
What we have learnt till now:
All behaviour of matter particles can be explained in terms of few
forces carried by exchange or carrier particles.
4 basic forces in today’s universe: gravitational weak,
electromagnetic and strong
 Relative strength ~10 -40 : 10 -5 : 10 -2 : 1
•2 groups: matter particles (fermions) and carriers of
inetractions (boson): graviton,( W,±Z ), photon, gluon
•Fermions affected by the forces, divided into subgroups
according to conformity with different interactions.
Wild spectrum of masses: electron mass= 0.5 MeV/c2
proton mass = 1 GeV/c2
mass of heaviest quark known (top) = 175 GeV/c2
No thorough understanding of the origin of the masses, mass pattern
Masses are to be determined experimentally.
Understanding the essential
• A symmetry of a physical system is a physical or mathematical feature
of the system (observed or intrinsic) that is "preserved" under some
change. eg.,the temperature of a room is invariant under a shift in the
measurer's position.
Symmetry is the guiding principle in understanding laws of Nature.
•Weak interaction is short ranged  carriers are massive unlike photon!
•The symmetry between EM and Weak interactions is broken!
Mγ =0, MW ~ 80 Gev/c2, Mz ~ 90 Gev/c2
Arguments for mathematical description similar to QED do not hold!
Signature of electroweak symmetry breaking is the existence of a
new soin-0, neutral particle: Higgs boson,
• yet to be discovered, but closing in on it!
• unknown mass, though the bounds can be deduced.
Higgs is the corner stone of the most successful theoretical model we
have which explains very well all experimental data till date.
Symmetry Breaking
• Nature has various symmetries
• Some of the symmetries are also broken, sometimes,
spontaneously (Nambu: 2008 Nobel prize).
• At higher temperature, or excited state both the Lagrangian and the
state are symmetric. At lower temperature the ground state loses its
symmetry.
• Potential changes its shape : phase transition
Below Curie
point
Above Curie
point
Anderson-Englert-Brout-Higgs-Guralnik-Hagen-Kibble mechanism
Primary goal of LHC : find the Higgs boson, (if it ever existed in
nature), OR, learn what principles are behind mass generation.
LHC: The Giant Marvel
• 50-175 m under the surface, with experiments at few places
• 27 km at 1.9 K (superfluid He), Vaccuum ~ 10-13 Atm.
• SuperConducting coils: 12000 tonnes (thousands magnets)
In operation since 2009: doing great right now big expectations!
Excellent experiments, capable of searching for Higgs, Supersymmetry, extra-dimension, other exotics and the unknown.
• Temperature generated at LHC due to proton-proton collision
~1016 0c, (sun: 5506 0c, a matchstick: 250 0c)
• LHC machine to be maintained at -271 0c vs. (Home freezer: -8 0c
Boomerang nebula: -272 0c, antarctica: -89.2 0c)
Largest ever human endeavour, requires huge resources to be put in.
being passed on to younger generations of today and tomorrow: YOU!
Indian contributions in LHC magnet components, detectors, computing,
physics.
What happens in LHC experiment
Summer, 2011
Proton-Proton
bunch/beam
1400
Protons/bunch
2. 1011
Beam energy
3.5 TeV
Luminosity
2.1033 /cm 2/s
Crossing rate
20 MHz
Collisions
108 Hz
Mammoth detectors registers
hard, inelastic collisions: particles
with large transverse momentum.
190 institutions from 40 countrieswith about 3800 scientists, students,...
Indian contributions in HO and Si-preshower detectors
Higgs event in CMS
Mass of the Higgs particle is
already very constricted to a
small region. More collisions
at LHC in near future will take
us to discovery (yes/no) and
much more interesting situation.
Busy environment
of proton collision
to be reduced to
Powerful techniques must be at work
 fun of the research!
Event size:
~1 MByte
Processing Power:
~X TFlop
The LHC computing GRID: information highway.
Novel computing technology  distributed computing and data
storage infrastructure to meet the challenge of data processing.
• tens of thousands of standard PCs collaborate worldwide
• much more processing capacity than a single supercomputer
• seemless access to data to thousands of scientists all over the world.
• Key is the high speed connectivity
Yesterday web
Today GRID
Indian contributions in GRID
middleware developement
CMS Tier2 GRID
computing centre at TIFR.
ALICE T2 in Kolkata
CMS group at TIFR
• Joined CMS international collaboration in 1993.
• Leading the collaborating institutes in India.
• Contributing in hardware (including upgrade), computing, physics and
other current activities (data collection, calibration..) of CMS experiment.
Learn more about these from faculties: Aziz, Banerjee, Dugad, Guchait,
Majumder, Mazumdar, Mohanty, Katta (D Block 2nd floor, C-Block 1st floor).
• Several students already finished Ph.D.s based on CMS experiment.
(recently, 2 ,with analyses based on collision data of 2010)
• Several students are very active in various analyses, few are just
starting: talk to them.
•Great opportunity right now for excellent work on hot topics based on lot
of data, interesting hardware for detector upgrade, computing, ..
Conclusion
LHC is poised to tackle some of the most profound questions
very soon.
Today, the LHC is attracting immense attention, it is possibly
THE most watched science project.
• Higgs particle is very elusive, it has not yet shown up in
experiments conclusively.
• LHC will shortly settle the issue about the existence of the Higgs
•particle. LHC experiments will also provide idea about the NEXT.
• Fascinating science, the curiosity provides the sustenance
over time.
• Forefront technologies in accelerator, detector, computing.
Sociological experiment as well: SUN never sets in CMS.
Stay Tuned!
Backup
Dogma of Symmetry
Five fold symmetry
Reflection/Bilateral symmetry
Radial symmetry
Is LHC meant for only searching the Higgs particle?
• Will we find the particle(s) that
make up the mysterious ‘dark
matter’ in our Universe?
• Will we understand the primordial state of matter
after the Big Bang before protons and neutrons
formed?
• Will we find the reason why antimatter and matter did not completely
destroy each other?
Next several years are going to be very exciting !
Black holes at LHC?
• If there are extra spatial dimensions in addition to usual 3, it is possible
that gravitational force is being shared by all  explains weakness
• LHC could prize open the inconspicuous dimensions just
enough to allow particles to move between the normal 3D
world and other dimensions, manifesting itself in the sudden
disappearance of a particle.
•Or, LHC may produce with very, very small probability, a
completely harmless Micro Quantum Black Hole!
• 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.
Not yet observed in collision data!  few TeV BH ruled out
Bringing in symmetry considerations in mathematical description
Dirac equation for spin1/2 particles (electron) remain invariant
under a global change of phase: Ψ (x)  e iθ Ψ (x)
leads to conservation of charge.
Now demand invariance under local change of phase :
Ψ (x)  e iθ(x) Ψ (x)
Requires existence of massless vector field (photon).
Quantum electrodynamics is the most complete, successful
theory: predictions match with measurements within 9 digits
after decimal !
Tempting to applying similar consideration to explain weak
Interaction among elementary particles: (n p e- ν = d  u e- ν )
Pecuiliarities about experiments
• Huge
mammoth size detectors 40m X 50 m X 50 m, weighing 12.5 kTon
• The magnetic field in CMS experiment 4 Tesla ~ 105 times earth’s field
• Silicon-based detector at the heart with total area 250 sq. m
• 80 thousand scintillator crystals (96% metal by mass), supported by
0.4 mm thick glass/carbon fibre structure.
•Brass used as absorbing material came from dismantled artillery shells
of Russian warships.
•1 sec. running of the experiment produces data volume ~ 10K
encyclopedia Britannica.
•Data production to reach ~ Tbyte/day when LHC runs in full force.
• Good fraction of data analysis from remote centres.