India becomes Associate Member of CERN, Geneva

[Hindustani78]

CHENNAI April 11, 2017 20:40 IST
Updated: April 11, 2017 20:40 IST
http://www.thehindu.com/sci-tech/sc...ision-point/article17929411.ece?homepage=true


The High Energy Accelerator Research Organisation (KEK) completed the much-awaited ‘rolling-in’ of the Belle-II experiment in Tsukuba, Japan, today. This experiment is designed to study violations of the Standard Model and dark matter. A grand collaboration of 700 scientists from 23 countries, Belle-II has a significant Indian participation both on experimental and theoretical sides. The fourth layer of the six-layer, highly sensitive particle detector, which is at the heart of Belle-II, has been built by Indian scientists, led by Tariq Aziz and Gagan Mohanty, who are with the Tata Institute of Fundamental Research (TIFR), Mumbai. “In 1998, when Indians [in this field] were working mostly with CERN (European Organisation for Nuclear Research), KEK first wanted us to participate in this experiment, which had a complementary approach,” says Prof Aziz.

Belle-II has better sensitivity, some 50 times higher, than its predecessor, Belle. “Initially, we did not have the chance to build the detector, and this is the second step — to work with the inner part of the detector, where the resolution has to be high. We are happy we did it and are now among four important groups in the world that can build such detectors,” Professor Aziz says.

Scientists from the Indian Institutes of Technology (IITs) in Bhubaneswar, Chennai, Guwahati and Hyderabad; the Institute of Mathematical Sciences (IMSc), Chennai; Punjab University; Punjab Agricultural University; MNIT (Malaviya National Institute of Technology), Jaipur; IISER (Indian Institutes of Science Education and Research) Mohali; and TIFR, Mumbai, are participating in this research. “Building the silicon vertex detector has been a directing force that brought us together. It is a very young team, with an average age of 30 years, apart from some senior leaders,” says Professor Mohanty.


The lone person leading theoretical studies among this group of 35-40 experimentalists, IMSc’s Rahul Sinha says, “Some of the modes and techniques that will be possible for Belle-II to study were first proposed by the group at IMSc.”

Complementary to the direct search experiments being carried out at the Large Hadron Collider in CERN, Belle-II will indirectly probe new physics using intense electron-positron beams and a sensitive detector. Indian scientists led by TIFR have built a part of the highly sensitive silicon vertex detector, which will be attached to the set up at a later date, now that the rest have been successfully integrated. The silicon vertex detector has a six-layered structure and the fourth layer was constructed by Indian scientists.

 

[Hindustani78]

A view of the Belle-II experiment in which the detector is being loaded into the collision point. | Photo Credit: KEK

http://www.thehindu.com/sci-tech/sc...k-at-beauty/article18058157.ece?homepage=true

In Japan’s Belle-II experiment Indians have built one layer of the detector
The High Energy Accelerator Research Organisation (KEK) in Japan is getting ready to launch the Belle-II experiment, a massive collaboration of 700 scientists from across the globe. At Belle-II, highly intense electron-positron beams will be made to collide and a huge number of B-mesons (a boson containing the B, or beauty, quark) produced. Building a detector to observe the resultant decay products is a challenging task and that is one area where Indians have contributed significantly.

Indians have been involved in the preceding experiment, Belle, for decades now, however, with Belle-II, their engagement is deeper. “Initially we did not have the chance to build the detector, and this is the second step – to work with the inner part of the detector, where the resolution has to be high. We are happy we did it and are now among four important groups in the world that can build such detectors,” says Tariq Aziz of Tata Institute of Fundamental Research, Mumbai, who led the effort along with Gagan Mohanty.

Crucial folding
Indians built the fourth layer of the six-layer silicon vertex detector and developing the analysis and theory. The highly miniaturised sensor engineering and the “origami chip-on sensor” design of the readout chip, which improves the signal to noise ratio, are novel and highly complex aspects.

The strips from one side of the silicon microstrip sensors are first connected to a flexible electrical circuit, which is turn is connected to readout chips. “We fold over the flexible circuit such that the strips of the other side of the sensor can be connected to the readout chip. This ‘folding over’ enables us to place the readout chips as close as possible to the strips reducing the noise,” explains Prof. Mohanty in an email to this correspondent.

Belle-II is some fifty times more sensitive than its predecessor Belle. The SVD detector is meant to measure the charged particles passing through it to an accuracy of 15-20 microns. Compare this with the average thickness of human hair, which is 100 microns. Such a precise position measurement significantly enhances the physics potential of the Belle-II experiment.

Physicists’ goal
This experiment has the same aim as the LHCb experiment at CERN — to study the decay of the short-lived B-mesons, and unearth clues to “new physics”. If these experiments are successful in their endeavour, they will cause a massive rethink of particle physics as we know it today. The two setups are complementary. “But the idea in both cases is to search for new physics and discover it,” says Rahul Sinha of The Institute of Mathematical Sciences, Chennai, who is leading the theoretical studies. Both will seek evidence that can significantly enlarge the picture of particle physics painted by the Standard Model.

For nearly fifty years, the world of elementary particles has been best described by the Standard Model. This also provides a unified description of all the forces in the universe except gravitation. It accounts for various particles and how they get their masses with the help of the Higgs boson. However, now many questions remain which could be helped by Belle-II.

The group at IMSc focuses on decays in which the beauty quark within a meson changes to a different flavour of quark known as the strange quark. These processes are very rare according to the Standard model, but can possibly be detected at Belle-II and LHCb.

 

[Hindustani78]

The Large Hadron Collider beauty experiment is one of the seven particle physics experiments collecting data at CERN. | Photo Credit: Special arrangement

http://www.thehindu.com/sci-tech/sc...new-physics/article18109006.ece?homepage=true

The European organisation for nuclear research (CERN) on Tuesday came out with a news that has more than raised an eyebrow among particle physicists. The LHCb experiment in CERN has shown a feeble but persistent sign of physics that contradicts a basic assumption of the Standard Model, indicating that this theory which has ruled the roost may not be complete in itself.

The cautiously worded news update on the CERN website mentioned that this result, which has a statistical significance of 2.2-2.5 sigma “in two bins,”is not conclusive in itself and needs support from further investigations. However experts feel that this is a very big discovery.

Dr. Rahul Sinha, a faculty member at The Institute of Mathematical Sciences, Chennai, and who has done pioneering work in this sector, says, “It is a giant step towards discovering new physics. The effect is big and people around the world will work to explain this.”

So what is it that LHCb has found?

At the subatomic level, there are two types of processes that have been compared by the physicists at LHCb. One is the decay of what is called a B meson into an excited K meson and a pair of muons (muon-plus and muon-minus). The other is where the B meson decays into K meson giving an electron-positron pair.

According to the standard model, since the muons and electrons are identical except for their masses, the rates of these two reactions should be the same. However, the carefully done experiment finds the rates are quite different. The researchers have taken care to factor out all the experimental error possibilities.

Dr. Amol Dighe of Tata Institute of Fundamental Research, a particle physicist working on the physcs of LHCb, advocates caution. “

They have announced a confidence level of around 97%. As such it constitutes an ‘indication’ and not a ‘discovery’. I will wait for this to go higher,” he says. Dr Dighe adds that in the next run, the LHCb will get five times more data and since they have set up the experiment carefully, they will likely get a better result.