https://doi.org/10.1140/epjc/s10052-008-0859-0
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
* e-mail: anant@cts.iisc.ernet.in
Received:
4
November
2008
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
