Status  Confirmed 
Seminar Series  IPNX 
Subjects  hepph 
Date  Thursday 22 June 2017 
Time  11:00 
Institute  IPN 
Seminar Room  Salle A201 
Speaker's Last Name  Ghosh 
Speaker's First Name  Shayan 
Speaker's Email Address  
Speaker's Institution  Indian institute of Science, Bangalore 
Title  Analytic solutions to massive twoloop sunset diagrams, and applications to Chiral Perturbation Theory 
Abstract  In this talk, we begin by showing how it is possible to obtain full analytic results for the twoloop three distinct mass scale sunset diagrams that appear in the expressions for the masses and decay constants of the pion, kaon and eta particles in twoloop SU(3) chiral perturbation theory. We then talk about two applications of these results: a) how it allows one to obtain small quark mass ratios to arbitrarily high powers, and b) how it allows one to make fits to lattice data to extract greater information about low energy constants. We then change track and discuss in more detail the MellinBarnes method used in our calculations, and demonstrate how this method can be extended using analytic continuation to obtain results for Feynman diagrams whose mass value parameters are such that it is impossible to use a direct calculation. We show how such methods of analytic continuation can also be helpful in contexts where a direct calculation does yield results, and thus set the stage for more widespread application of this technique. 
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