Welcome to Physics Group
Variable Energy Cyclotron Centre, Kolkata
Posted on 26th August, 2015 by Saila Bhattacharya and Tilak Ghosh
Dr. Tapan Kumar Rana has been selected as the best Young Physicist in the Young Physicists Colloquium (YPC 2015) held in the last week (20-21 August, 2015) at Saha Institute of Nuclear Physics. He was awarded the S.N. Ghosal award with a handful of cash prize, apart from books and a certificate. Young Physicist Colloquium (YPC) is a well known yearly event, organized by the Indian Physical Society. 21 young physicists (of age less than 35 years) were selected from the country to present their research work. A board of judges selected the best three presentations.
In the colloquium Tapan presented his research work that deals with the famous Hoyle State saga.
The Hoyle state saga:
The world around us has been fascinating our imagination since the early days of human civilisation: ‘What we are made up of, and what are the constituents of our mother earth?’ Now we know that the life on the earth would not have existed without the presence of the element Carbon, which is the fourth most abundant element on earth. In addition, we also have a long series of elements up to Uranium. How these elements were formed?
The story unfolds from the time zero, dating back to ~13.8 billion years from today, when the universe started with an explosion called ‘Big Bang’ and produced mostly Hydrogen and Helium through a process called Big Bang Nucleosynthesis. However this phase lasted only for a few (~3 - 20) minutes. So, at the end, there is no Carbon, no heavy element, no life – a dull universe indeed!
The next stage of cooking started much later (~ 500 million years) - when stellar bodies were formed to carry forward the fusion chain to produce heavier elements – only to end up in a roadblock, as stable elements corresponding to mass numbers A = 5 and 8 do not exist ! As the way out, it was proposed that the synthesis of Carbon might have taken place through a successive 3alpha capture process: alpha + alpha => 8Be (t1/2 ~ 10-16 s); 8Be + alpha = 12C. To enhance the reaction rate and explain the abundance of Carbon on earth, Fred Hoyle postulated the existence of a resonant state of 12C just above the 3alpha decay threshold; this 02+ state at 7.654 MeV above the ground state is the famous Hoyle state.
Though postulated initially to solve an astrophysical puzzle, Hoyle state soon turned out to be a puzzle in itself– so much so that even six decades into its discovery, it still evokes a lot of interest; and the problems are manifold – indicating large gaps in our present day understanding of nuclear physics. To mention in brief:
-it is also known to have larger radius compared to that in the ground state, giving rise to wild speculations about its exotic shapes like linear 3a chain, bent-arm or compact triangular configurations. At the same time, it is also considered as a dilute Bose gas which may end up in a nuclear 3a Bose-Einstein Condensate!!
- it is not reproducible by standard shell-model calculation – a classic example of alpha-cluster nuclear states in light nuclei, which led to the development of the most advanced ab-initio and no-core shell model methods to tackle the problem.
Thus it is worth taking up the challenge to unravel the mysteries of Hoyle state! Tapan along with his group members at this centre have been involved in this exciting game to determine quantitative contributions and extract ‘signatures’ of the exotic structure of the Hoyle state and other Hoyle-like bands in light nuclei using light particle beams from the cyclotron.
Well done Tapan, congratulations !!