Regular Article - Theoretical Physics
Constraining the low-energy pion electromagnetic form factor with space-like and phase of time-like data
Centre for High Energy Physics, Indian Institute of Science, Bangalore, 560 012, India
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Revised: 10 December 2008
Published online: 16 January 2009
The Taylor coefficients c and d of the EM form factor of the pion are constrained using analyticity, knowledge of the phase of the form factor in the time-like region, 4m π 2 ≤t≤t in and its value at one space-like point, using as input the (g−2) of the muon. This is achieved using the technique of Lagrange multipliers, which gives a transparent expression for the corresponding bounds. We present a detailed study of the sensitivity of the bounds to the choice of time-like phase and errors present in the space-like data, taken from recent experiments. We find that our results constrain c stringently. We compare our results with those in the literature and find agreement with the chiral perturbation-theory results for c. We obtain when c is set to the chiral perturbation-theory values.
© Springer-Verlag, 2009