**Research Highlights**

**
Determination of the strong coupling constant at high precision
using renormalization group and Borel summation methods
**

- *B. Ananthanarayan, Gauhar Abbas*, CHEP

The determination of the strong coupling constant, which is the
analog of the Sommerfeld fine structure constant of elecrodynamics,
is one of the most important issues in elementary particle physics.
The problem is a very subtle and difficult one due to the inherent
uncertainties of renormalization group methods. Recently, an
important new development has been advanced by a
student, **Gauhar Abbas** (now a post-doctoral fellow at the
Institute of
Mathematical Sciences, Chennai) and **B. Ananthanarayan**
(Professor and Chairman, CHEP) from the Centre for High Energy Physics of the
Indian Institute of Science, working in collaboration with
**Irinel Caprini** from Bucharest,
Romania, in the use of a particular method of resumming renormalization
group effects in the extraction of the strong coupling constant
from the decays of the tau-lepton, a superheavy cousin of the electron.
This result was published in Phys.Rev. D85 (2012) 094018 some months
ago, and has already been cited in an influential review by
Siegfried Bethke in his `World Summary' for this constant for
the year 2012. The trio above has more recently collaborated
with **Jan Fischer** from Prague, Czech Republic,
to accelerate the convergence of the
relevant perturbation expansion in the Borel plane, as the theory
is known to have a zero radius of convergence. F. Dyson had addressed
the corresponding problem in electrodynamics over a half century ago.
These authors have presently put together powerful tools of complex
analysis and Borel summation methods and have obtained impressive
results by combining these with renormalization group summation
and have provided an excellent determination of the strong coupling
constant with reduced errors. This work
has been published in
Phys. Rev. D 87 (2013) 014008 on January 7, 2013.
The CHEP group has thus broken new ground and have contributed in a
fundamental manner to the advance of elementary particle physics.