Indian scientists in antimatter discovery

Subhra Priyadarshini

doi:10.1038/nindia.2011.58 Published online 26 April 2011

Artist's rendering of an anti-Helium-4 nucleus emerging from the collision.

© Brookhaven National Laboratory

Scientists from six Indian research bodies are excited over the detection of the heaviest ever antimatter by the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory, USA.

The Indian scientists are part of the international STAR collaboration at RHIC which reported detecting the heaviest ever antimatter partner of the helium nucleus — antihelium-4 — last week. The collaboration has been working on the particle accelerator used to recreate and study conditions of the early universe. The new particle, also known as the anti-alpha, is the heaviest antinucleus ever detected.

The Indian presence in the 12-country, 54-institution effort at RHIC draws from the Panjab University, Chandigarh; Indian Institute of Technology, Mumbai; University of Jammu; Variable Energy Cyclotron Centre (VECC), Kolkata; Institute of Physics, Bhubaneswar and University of Rajasthan, Jaipur.

Says Yogendra Pathak Viyogi, leader of the Indian conglomerate and head of the experimental high energy physics group at VECC, Kolkata,"It is certainly a matter of great pride for all of us to be a part of the discovery of anti-alpha, the heaviest anti-matter to have been seen in terrestrial experiments."

Since the year 2000, about 30 scientists and research scholars from India have been associated with the STAR experiment. Indian scientists have built a Photon Multiplicity Detector (PMD) for measurement of photons emitted from hot and dense matter formed in the collision. Although PMD is not involved in the discovery, Indian scientists and students have been involved in several other analyses, Viyogi told Nature India.

3-D rendering of STAR time projection chamber showing antihelium-4 track in red.

© the STAR Collaboration

The detection of antihelium-4 is extremely rare since the next weightier antimatter nucleus that does not undergo radioactive decay is predicted to be a million times more rare — and out of reach of today's technology, according to a release by the Brookhaven National Laboratory.

The findings could provide a benchmark for possible future observations of anti-alpha in the cosmos.

The RHIC investigates fundamental questions about the nature of matter, antimatter, and the early universe. One of the great mysteries of physics is why our universe appears to be made entirely of ordinary matter when matter and antimatter are understood to have been created in equal amounts at the time of the Big Bang.

Similar experiments are also being undertaken at the Large Hadron Collider at CERN, the European laboratory for nuclear and particle physics research, though at energies more than an order of magnitude higher than at RHIC.

At RHIC, gold ions moving at nearly the speed of light were collided head-on. This simulated conditions just after the Big Bang. In these atomic smashups, quarks and antiquarks emerged with approximately equal abundance.

The scientists then sifted through data for half a trillion charged particles emitted from almost one billion collisions to detect 18 examples of the unique 'signature' of the antihelium-4 nucleus. Each such signature consists of two antiprotons and two antineutrons in a stable bound state that does not undergo radioactive decay.

The antihelium-4 nucleus has a negative electric charge that is twice that of an electron. Its mass is very close to four times that of a proton.

The findings will also form part of a PhD thesis for an Indian researcher from the Institute of Physics in Bhubaneswar directly involved in the discovery.


  1. Tang, A. et al. Observation of the antimatter helium-4 nucleus. Nature. doi: 10.1038/nature10079 (2011)