Wednesday, August 29, 2012

India at The Large Hadron Collider A Backgrounder

The accepted view today is that the Universe started with a gigantic explosion called the "Big Bang". For fractions of a second after the Big Bang, the Universe consisted of the most elementary constituents of matter interacting with each other through other particles which are carriers of different kinds of forces existing in nature. And, the carriers of all forces in Nature are "bosons", named after the famous Indian physicist Satyendra Nath Bose. The behaviour of these elementary particles is described today by a mathematical model called the Standard Model. According to Standard Model, all particles acquire mass through their interaction with another particle called the Higgs particle (also popularly called the "God Particle" in the Media), named after the British physicist Peter Higgs. The Higgs particle is again a boson. It is a matter of pride for us that bosons play such an important part in the evolution of Universe and, perhaps, also in the ultimate fate of the Universe.

            Physical situations similar to what existed at fractions of a second after the Big Bang are experimentally created in laboratories through collision of particles or nuclei. That is the primary intellectual reason why high energy particle accelerators are built. The Standard Model has been tested with considerable precision in accelerator experiments so far and has come out with flying colours. The only missing link has been the Higgs Boson. Unfortunately, the Standard Model does not predict the mass of the Higgs Boson. As the Model continued to have excellent agreement with experimental observations, the anxiety to find the Higgs Boson also kept growing, especially because it plays such an important role in the structure of the Standard Model. All accelerators in the past continued with their search and put bounds on its possible mass.

The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) was planned with the special aim of detecting the Higgs particle if its mass was below 1000 GeV. CERN, as a result of two experiments has recently reported discovery of a new particle, expected to be the long sought after Higgs particle.

            The Department of Atomic Energy (DAE) and the Department of Science and Technology (DST) of the Government of India are organizing a one-day National Meet on "India at the Large Hadron Collider (LHC)" at the Indian National Science Academy (INSA), New Delhi with assistance from INSA and Vigyan Prasar, Noida. The purpose of the Meet is to showcase Indian contributions to the construction of LHC, the CMS (Compact Muon Solenoid) and ALICE (A Large Ion Collider Experiment) Experiments and the development of the LHC Computing Grid.

The Large Hadron Collider at CERN

            LHC is the most ambitious project undertaken by CERN so far. The LHC is a giant particle accelerator buried underneath the ground, 27 km in circumference and crossing throughSwitzerland and France several times. After the feasibility study and financial assurance from various countries in the world, the construction of LHC was launched in 1996. It is designed to produce proton-proton collisions with a centre of mass energy of 14 TeV, to be followed by collisions between lead nuclei involving a centre of mass energy of 1150 TeV. At the present time, it is producing proton-proton collisions at a centre of mass energy of 8 TeV. LHC, even at this lower operating energy at present, is already the highest energy particle accelerator ever built by mankind. Even a greater achievement has been the extremely large "luminosity" of collision that has been accomplished by the machine. This essentially means that protons can be made to interact at the interaction points with extremely large flux. The total cost of building the LHC has been about 4.5 Billion Euro and its annual operating budget is around 800 Million Euro. The physics studies are carried out at LHC at 6 ‘collision points’, 4 of which are equipped with large detector set-ups. These are CMS, ALICE, ATLAS and LHCb and will provide the scientists a peek into a totally unexplored micro-cosmic world. Scientists from India have taken part in building the LHC machine and the first two of these four detector set-ups. Further, the data volume at LHC is a big challenge for computing and this has been tackled via the development of LHC computing Grid, a new paradigm.

LHC as an example of Mega Science

Facilities such as the LHC, by virtue of their resource requirements, technical complexity of building, and the gigantic efforts required in carrying out and analyzing the data produced by the experiments, fall into the class of research facilities which are commonly called now as "Mega Science Facilities". The outstanding questions in Particle Physics today are at a length scale which require particle probes at extremely high energies. The physics questions that it tends to answer belong to the sub-nuclear length scales or to very early stages in the evolution of the Universe (picoseconds to microseconds after the Big Bang). Such high energy probes are produced at particle accelerators like the LHC which are multi-billion dollar facilities. These are no more affordable for individual nations and, hence, international consortia engage in building and managing such facilities. Technologically, such facilities are engineering marvels pushing the technology frontiers to their extreme in wide range of engineering disciplines. All of this requires that the best in the world pool not only their financial resources but also their intellectual resources to build such facilities. The coordination among scores of research laboratories spread all over the globe and participating in such efforts is remarkable.

Such facilities have a long list of very useful technological spin-offs – the World Wide Web being one of them. WWW was invented at CERN in connection with previous generation experiments at the Large Electron Positron (LEP) collider facility.

The need, challenges and benefits of engaging in such "Mega Science" pursuits will be discussed during the Meet.

History of CERN-India Collaboration – the run-up to LHC
The history of Collaboration between CERN and India is a long one. It started with scientist-to-scientist and institutional collaborations in the 1960`s. Scientists from TIFR won recognition for their contribution to the L3 detector in the 80`s. The collaborations gradually built up with time. In order to further increase the pace of accelerator development in our country and to give a thrust to experimental high energy physics programme, DAE and CERN signed an agreement of cooperation in 1991 for a ten year period. In the early years of this agreement, the Raja Ramanna Centre for Advanced Technology (RRCAT), Indore successfully delivered a few sub-systems for upgradation of LEP-200 project, thereby confirming viability of such an arrangement. The formal framework provided by this agreement was also tapped by the Indian High Energy Physics (HEP) community by participating in a frontier area of research involving the heavy (lead) ion collision programme being carried out at CERN. A number of DAE institutions and universities (supported by DST) took part in these efforts and won recognition for their scientific efforts. So, when CERN launched its most expensive LHC project, and was looking for competent partners  in this programme, in terms of ideas, hardware and manpower, our past association came in handy. A protocol was signed in March 1996 between DAE and CERN and India joined the LHC project and agreed to provide in-kind contribution in terms of hardware, skilled manpower and software to the tune of 25 million USD (equivalent to 34.4 million Swiss francs). By 2001-02, different components identified for Indian contributions to LHC had touched 34 million Swiss francs and large-scale fabrication of many such components was well on course, with the help of large industrial enterprises in the country. This convincingly established our credentials and ultimately resulted in (i) CERN extending the 1991 cooperation agreement with India for a further ten-year period; (ii) our in-kind contribution on the request of CERN being enhanced to 60.4 millions Swiss francs; and (iii) India being accorded the ‘Observer status by CERN Governing Council with only Israel, Japan, the Russian Federation, Turkey, USA, EC and UNESCO being the other observers. The CERN-India Collaboration has reached a new height recently with Indiabecoming an Associate Member.

Indian Contributions towards building up of LHC

The in-kind contributions that India committed to CERN involved hardware, software as well as skilled manpower support. The hardware supply opened a door for Indian industry to take up the challenge of delivering high-quality products for a cutting-edge international research project. RRCAT, Indore with a major programme in accelerators, was the nodal DAE institution which had the responsibility to carry out necessary R&D work to prototype and develop the components, so as to meet the given specifications before their large-scale production was entrusted to industry. The other institutions involve were BARC, VECC and IGCAR. India successfully supplied items like superconducting corrector magnets-sextupoles (MCS), decapoles (MCD) and octupoles (MCO); mechanical systems, namely precision magnet positioning system-jacks (PMPS-jacks); accelerator protection system-quench protection heater power supply (QPS), quench detection electronics (QDE) and control electronics for high current circuit breakers; vacuum system-vacuum system design for long beam transport lines for beam dumps; cryogenics-large capacity liquid nitrogen tanks and test facility for testing of Sc magnets at 4.2 K; engineering studies-analysis of cryogenic distribution line interconnects and test and analysis for magnets along with necessary technical documentation; and so on.

Indian Contribution to the CMS Experiment
            One of the leading experiments/detectors at CERN is the CMS (Compact Muon Solenoid) Experiment/Detector.  This is one of the two experiments at LHC which have led to the discovery of a new resonance, expected to be the much sought after Higgs Boson. This experiment will also probe into some other fundamental issues in physics, namely, physics beyond the Standard Model like supersymmetric particles; detailed properties of the top quark; search for new heavy gauge bosons; possible quark and lepton substructure, and so on.

            5 Indian institutions have been are participating in this experiment: TIFR, BARC,Delhi UniversityPanjab UniversityChandigarh and Visva Bharati, Santiniketan (as an associate of TIFR group). Lately, SINP, Kolkata and IIT, Mumbai (as an associate of BARC group) have also joined this experiment. Participation of NISER, Bhubaneswar is under discussion. This research has been jointly funded by DAE and DST on 50:50 basis.

            Towards hardware of the CMS Detector, the Indian groups have already contributed the Hadron Barrel Outer Calorimeter (HO-B) and the Silicon Strip based Pre-shower Detector (PSD) of the endcap electromagnetic calorimeter. In addition, the Indian groups have significantly contributed towards development of software, analyses strategy from early days of CMS and, finally, physics analyses of data. Frequent presentations of scientific results on behalf of CMS collaboration by Indian scientists in international conferences also indicate the significant role being played by the Indian scientific community in the overall functioning of CMS. The members of Indian collaboration have also been assigned CMS-wide coordination roles. At present, Indian scientists are also deeply involved in collection of data, monitoring and certification of data as well possible improvement in the performance of various detector subsystems.

Indian Contribution to the ALICE Experiment

            Apart from accelerating protons, the Large Hadron Collider (LHC) will also accelerate and collide heavy ions, e.g. Pb ions with a centre of mass energy of 1150 TeV.

            The collision of such ultra-relativistic heavy ions is predicted to produce a new phase of strongly interacting matter at extremely high energy densities, called the Quark Gluon Plasma (QGP). This phase of matter is also believed to have existed in the very early Universe.  Search for QGP is an important goal at LHC. The ALICE (A Large Ion Collider Experiment) Experiment is the only dedicated experiment at LHC which will search for QGP.

            8 Indian institutions are participating in this experiment: VECC and SINP, Kolkata, IOP, BhubaneswarPanjab UniversityChandigarhRajasthan University, Jaipur, JammuUniversityJammuAligarh Muslim UniversityAligarh and IIT, Bombay. 4 new institutions – IIT-Indore, Bose Institute, Kolkata, Gauhati University and NISER, Bhubaneswar are expected to join this experiment very shortly. This research has also been jointly funded by DAE and DST on 50:50 basis.

            On the hardware side, the Indian groups have built a Photon Multiplicity Detector (PMD) and some Tracking Chambers for the Forward Muon Spectrometer. The Indian groups have also developed a special chip for the Forward Muon Spectrometer, called the MANAS chip.

            In addition, the Indian groups have participated in development of software, experimental runs and, finally, in the physics analysis of data.

Indian Contributions to the Worldwide LHC Computing Grid (WLCG)

The 4 experiments at LHC, viz. ALICE, ATLAS, CMS and LHCb, detect subsidiary particles generated during the collision of particle beams. The number of interactions among protons when the proton beams collide every 50 nano-second is almost thousand million. A major detector like CMS has about 10 Million electronic channels to collect information of the collision. Through judicious choice the data archival rate is reduced by many orders of magnitude and finally about few Giga bytes of data is stored for subsequent analyses in detail. In the heavy operation, each collision is expected to generate up to 2000 subsidiary particles, which is observed through 180,000 channels. The total data generation amounts to about 8-10 Petabytes (1000, 000 Gigabytes) in a year of experiment time.

CERN has used very effectively the technology of Grid Computing to carry out physics analysis with this voluminous amount of data. This has been possible due to the availability of high speed networking over large distance. The basic principle is to store, manage, monitor and make available data to a collaborating scientist at anytime, anywhere in the world. Effective use of this technology is partly responsible for quick results from the experimental runs so far. The WLCG is a tiered structure of distributed computing resources used by all scientists working at the LHC. India hosts 2 Tier-2 Centres at TIFR and VECC and a large number of Tier-3 Centres at various institutions.

     Indian scientists at BARC have developed and deployed a number of software projects successfully in collaboration with IT Division, CERN. They have developed important software tools like GRIDVIEW and SHIVA. Gridview is a tool that is used by the WLCG/EGEE communities to visualize various functional metrics of the grid. The members of the Gridview team in Computer Division are seen as experts in availability and reliability and are acknowledged for their experience in developing and running the very large Terabyte scale databases used by Gridview. SHIVA is a software tool for implementing problem tracking systems for software projects. In addition, all groups in the CMS and ALICE Experiments have utilized the WLCG for simulations and for analyzing the physics data.

This research has also been jointly funded by DAE and DST on 50:50 basis.

Total Investments so far

            The investments in LHC-related activities since 1996 (i.e. over 15 year period) will be approximately Rs. 400 crore.

Impact of India`s engagements at LHC

It will not be an exaggeration to say that India`s engagements at CERN and LHC have madeIndia arrive on the global Mega Science scene. Since our effective participation in LHC, several international consortia have approached India for participation and India is now participating in the FAIR project in Germany, TMT project in USA and so on. The number of experimental groups in experimental high energy physics have steadily grown because of our LHC involvement. Several students who completed their doctorates on LHC related projects have joined leading institutions after valuable post-doctoral experience abroad. At the national level also, our engagement with LHC has led to increased collaboration among institutions in the country. It has also led to exemplary coordination and cooperation between DAE and DST.

Finally, as a result of our efforts and investments, India proudly shares the results coming out of LHC which are at the very frontiers of human knowledge. There is today in the country a vibrant 150-200 strong community of scientists and research students in the area of experimental high energy physics. And, most importantly, a large number of young scientists are in the making at any give time due to their participation in these intellectually challenging and exciting scientific ventures.

No comments: