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.