Research Highlights

It matters a lot

Subhra Priyadarshini

doi:10.1038/nindia.2008.157 Published online 20 March 2008

Tariq Aziz in the TIFR lab with the Silicon Micro Strip Detector

A global collaboration of scientists has now found evidence for a rare process that may explain why our observable Universe is dominated by matter.

The dominance of matter over antimatter in our Universe raises questions about the initial conditions of the Big Bang, and has troubled cosmologists for over 30 years. It is widely believed that the current asymmetry between matter and antimatter has evolved since the Big Bang as they are treated differently in nature — antimatter decays more rapidly.

The Belle Collaboration, a large scale experiment running at Japan's KEK high-energy physics laboratory, tackles this by using 535 million B-meson/anti-B-meson pairs to measure asymmetries. Previous work suggested a difference in the decay of charged and neutral particles — an asymmetry in the decay rate of about +7% for charged B mesons and −10% for neutral B mesons.

The new study reduces uncertainty on the charged particle decay rate by a factor of 1.7, providing stronger evidence for a large deviation in direct violation between charged and neutral B meson decays.

Tariq Aziz from Mumbai's Tata Institute of Fundamental Research (TIFR) speaking on behalf of Indian scientists participating in the Belle Collaboration, says that most of the asymmetries in the decay rates fit the pattern envisaged in the standard model developed during early 70s. The anomaly in the standard pattern arises from charged B-meson decay rate asymmetry, in particular when compared to the neutral B-meson. This anomaly could be the smoking gun for new physics. The collaboration is collecting more data to sharpen the picture.

Scientists from TIFR and Panjab University, Chandigarh are participating in the research that involves members from 13 countries.


  1. The Belle Collaboration. Difference in direct charge-parity violation between charged and neutral B meson decays. Nature 452, 332-336 (2008)