LHC, CMS and DHEP. Kajari Mazumdar. Departmental Introduction, 2011

Transcription

1 LHC, CMS and DHEP Kajari Mazumdar Departmental Introduction, 2011 August 11, 2011

2 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.

3 Our Universe... Important epochs Energy =kt Length scale = hc/e 1. Quantum gravity era: t s 1032 K (1019 GeV, m) Big Bang 2. Grand Unification Era: t s 1027 K (1016 GeV, m) 13.7 Billion Years 5. Today (3K) 1028 cm 3. Protons and neutrons formed: t 10-4 s, 1013 K (1 GeV, m) 4. Nuclei are formed t = 3 minutes, 109 K (0.1 MeV, m)

4 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 ~ 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

5 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.

6 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.

7 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.

8 LHC: The Giant Marvel m under the surface, with experiments at few places 27 km at 1.9 K (superfluid He), Vaccuum ~ Atm. SuperConducting coils: 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: c, a matchstick: 250 0c) LHC machine to be maintained at c vs. (Home freezer: -8 0c Boomerang nebula: c, antarctica: c) 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.

9 What happens in LHC experiment Summer, 2011 Proton-Proton bunch/beam 1400 Protons/bunch Beam energy 3.5 TeV Luminosity /cm 2/s Crossing rate 20 MHz Collisions 108 Hz Mammoth detectors registers hard, inelastic collisions: particles with large transverse momentum.

10 190 institutions from 40 countrieswith about 3800 scientists, students,... Indian contributions in HO and Si-preshower detectors

11 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

12 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

13 CMS group at TIFR Joined CMS international collaboration in 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,..

14 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!

15 Backup

16 Dogma of Symmetry Five fold symmetry Reflection/Bilateral symmetry Radial symmetry

17 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!

18 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 to 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 s spewing out many particles isotropically in the detector. Not yet observed in collision data! few TeV BH ruled out

19 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 )

20 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.