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Home , ATLAS experiment, Compact Muon Solenoid

INDIA in CMS Experiment at the LHC

Research in the branch of deals with the building blocks of matter and the fundamental forces.

The Large (LHC) at CERN, Geneva, is the largest ever human endeavour with the involvement of about 10 thousand scientists addressing mysteries of nature at the deepest level.

India joined the LHC project in its early phase and contributes to all aspects: machine, experiments and computing.

CMS

LHC machine LHCf

LHC control room

LHCb ALICE

ATLAS

As of July 2012, the CMS experimental collaboration comprises of 4300 people from 179 institutes in 41 countries including India.

Visva Delhi IIT Panjab BARC SINP TIFR Bharati University Bombay NISER University 35 faculty members, 20 engineers and 40 students from 8 institutes & universities. Indian participation in CMS is jointly supported by DAE and DST. http://cms.web.cern.ch/ LHC: the discovery machine at the and luminosity frontiers

In the last decades the theoretical description of the elementary particles, better known as the , is tested very precisely (to better than 0.1%).

However, there are still several important issues which are not understood well. Some of them are: What is the origin of the of the elementary particles? Do the elementary particles of today have further sub-structures? What is the nature of the that constitutes about 20% of the universe? Why is there no in today’s universe?

Physicists hope to find answers to these questions through the experiments at the LHC. Hadron collider machines at the energy frontier are capable of discovering new, heavy particles. They also probe the behaviour of forces at high energy. The experiments test the ideas about the evolution of the universe.

What happens at the LHC

Parameters in 2012 operation The LHC is the world's most powerful microscope, exploring a distance scale of Beam Energy 8* 10 12 eV 10-18 m. luminosity 7* 10 33/cm 2 /s moving in opposite directions at number of bunches/beam 1380 99.999999% of the smash into each other to recreate conditions of number of protons/bunch 1.6* 10 11 the universe which existed a fraction of a second after the big bang.

Currently the LHC collides protons at a centre of energy of 8 TeV (equivalent to 0.0000012 per pair) every 50 nano seconds at few points where the experimental collaborations have put up detectors to study the outcome of these collisions.

At the LHC there are two multipurpose experiments, CMS and ATLAS. Additionally there are other dedicated experiments, ALICE, LHC-b and LHC-f. The preparation for the LHC project – machine and experiments alike – took almost two decades. The LHC machine has started delivering collision less than three years back. The LHC project is expected to continue for the next 20 years.

CMS, the acronym for Compact Solenoid, is an excellent detector consisting of 3 main subsystems with an envelope of high of 3.8 : • The tracking detector to identify and measure passage along the beam direction of the charged particles, like, , , etc. • The calorimeters to measure the energy and direction of particles, like, electrons, , , protons, etc. • The muon system to detect and measure the of muon. Cartoon of CMS Detector

INDIA

INDIA India in CMS experiment

Salient contributions from India: Indian Institutes: 1. Detector R&D in 1990s 1. Bhabha Atomic Research 2. Study of material for the electromagnetic detector and design Centre (BARC) Mumbai of its granularity 2. Delhi University Delhi 3. Optimization of tracker detector material/geometry 4. Fabrication of subdetector systems, installation, testing 3. Indian Instute of Technology 5. Physics studies for optimization of detector in preparatory stage (IIT) Bombay 6. Software development for detector simulation 4. National Institute of Science 7. Studies with test beam, cosmic muons Education and Research 8. Data collection, data quality monitor (sometimes remotely from India). (NISER), Bhubaneswar 9. Understanding of detector performance, possible improvements 5. Panjab University, Chandigarh 10. Calibration of detector 6. Saha Institute of Nuclear 11. Physics analyses, review of collision data leading to publications Physics (SINP), Kolkata 12. Several collaboration-wide responsibilities within CMS 13. Representing collaboration in international conferences 7. Tata Institute of Fundamental 14. In CMS via Tier2 centre Research (TIFR), 15. Detector upgrade for future operational phases of LHC including R&D Mumbai 8. Visva Bharati University, Santiniketan Indian hardware contributions in the currently operating CMS detector: Hadron Outer (HO) Calorimeter, in barrel region (TIFR, Panjab University) Logistic support to neighboring  Preshower detector of Electro Magnetic Calorimeter in endcap region country Shri Lanka (BARC, Delhi University).

Current hardware involvements for the detector upgrade: Fabrication of Resistive Plate Chambers for the endcap muon system (BARC, Panjab University) Fabrication of read-out control cards for replacement of the photo-detectors for HO (TIFR) R&D Front/back-end electronics for HCAL (TIFR, SINP) R&D for subdetector systems suitable for the high-luminosity and high-energy operation of LHC, like tracking system A proton-on-proton collision in CMS

A -on-lead collision and first Z event in HI collision

Multiple collisions during a single bunch crossing Motivation of the Experiments at the LHC

The Standard Model is able to describe all the Particle zoo in Standard Model experimental observations till date. The Higgs particle is the consequence of the phenomenon which is responsible for the masses of all the fundamental particles.

Discovery of the is therefore very crucial for the completeness of the of elementary particles and their interactions. The most important goal for the LHC experiments is to resolve the issue of Higgs (whether it exists or not). Since all the masses have to be measured experimentally, the LHC is indeed capable of producing the Higgs particle. The mandate of the major experiments, like CMS, are: 1. Resolve the issue of by Everyday matters We were missing this discovering the Higgs particle or ruling out its consists of only particle predicted in existence. these Standard Model till now 2. Probe the physics at the new energy region of TeV.

Rediscovery of known physics at LHC as precursor to discovery Resonances in di-muon final state observed in p-p & Pb-Pb collisions

Particle Physics of last lastcentury century rediscovered with rediscoveredearly LHC data.

The main focus during the early phase of the experiment was on analyzing collision data to establish the detector performance along with various cross checks of known results as shown above. Occurrence of Higgs boson and other new, massive particles are very rare , once in few billion collisons. Hence data have to be collected for a long time.

The foundation for the discovery of Higgs boson is laid with the measurement of background processes and comparing their rates as predicted in theory.

The observation essentially implies excess of events above background expectation. Discovery of a new boson of mass 125 GeV

H ZZ 4 l candidate

http://cms.web.cern.ch/news/observation-new-particle-mass-125-gev

• Search for the Higgs particle at the LHC is very challenging and required excellent performance of machine, all the subsystems of the CMS experiment as well as LHC computing .

• The experimentally highly sensitive and high resolution discovery channels are when the Higgs particle decays in the modes : H2 photons and HZZ 4 charged (pairs of , muon). • In the first case the resonance structure is detected above huge but smoothly falling background with a significance of 4.1 sigma. • In the second case again the peak is visible with 3.2 sigma significance. • Both the peaks are at the same position corresponding to a mass of about 125 GeV.

• The combined confidence level of the observation of a resonance in CMS experiment is 5 sigma. • This corresponds to a probability of the background fluctuation to be at least as large as the observed maximum excess: less than 20 in a hundred million.

• ATLAS experiment has similar result and hence there is independent confirmation. • This resonance is likely to be the Higgs boson being sought after. • Confirmation of its properties needs more data which is being collected and analyzed during current phase of LHC operation.

• There are other possible discoveries at the LHC in the coming decade. Hadron Outer Calorimeter (HO)

Participation from TIFR (Mumbai) and Panjab University (Chandigarh) • Importance : better energy measurement  crucial for energy balance in event  key observable for discoveries. • Fabrication of 432 Plastic scintillator tiles with wavelength shifting fibres covering about 400m2 . + 72 honeycomb panel housings • Photosensors for hadron calorimeter to be upgraded in future for better sensitivitites  lot of R&D s in India. • Control boards for Silicon photo multiplier tubes for HO being fabricated and tested in India.

HO detector units installed in CMS Tower structure of detector including HO

Silicon single sensor Silicon Preshower Detector in Electromagnetic calorimeter Endcap region

Participation from BARC and Delhi University  Silicon preshowers in the endcap region of CMS detector provides the required sensitivity to identify Higgs to 2 photon decays in that region.  Plays crucial role in the discovery of the Higgs particle.

 Two Endcaps: total 4200 silicon strip detectors covering an area of 17 m2  Strip width 1.8 mm, pitch 1.8 mm, area 63 mm  63 mm .  Fabrication at BEL with the close supervision of BARC.  Characterization studies at Delhi University  Large area silicon detectors made in India for the first time.  High quality of detectors, comparable with international producers.  India has provided more than what was initially planned.

assembly of 7 micromodules with system mother board Additional layer of RPCs for Muon Endcap region

Completed RPC under test before shipment

Aluminium patch panels for cooling rings. Copper tubes being bent. Completed cooling system.

CMS detector will have better measurement of muon due to an additional layer of Resistive Plate Chamber in the endcap regions. RPCs are large area high precision chambers to be used for extending capability of muon trigger at large angles.

25% of the total required detectors as well as all the cooling accessories are being fabricated in India by BARC and Panjab University, Chandigarh. Grid computing Tier2 centre • Grid computing is the new paradigm emerged due to the demands of the experiments at LHC. The processing, storage and management of several Petabytes of data every year is possible only by pooling all the available resources together.

• It is natural evolution of internet where information across long distance flows at comparable rate with the internal speed of the computer  distributed computing. CMS computing Grid • High speed connectivity is the key for grid computing.

• CMS Tier2 center in India is operational before start of the LHC.

• Important contribution for CMS computing efforts.

• Additional storage facility for 1 Tier 0 Indian scientists to support their 7 Tier 1 T2-IN-TIFR analyses efforts. 50 Tier 2 indiacms