Eur. Phys. J. A (2010) 44: 175-179
https://doi.org/10.1140/epja/i2010-10969-y

Letter

Stringent constraints on the scalar K form factor from analyticity, unitarity and low-energy theorems

¹ Centre for High Energy Physics, Indian Institute of Science, 560 012, Bangalore, India
² National Institute of Physics and Nuclear Engineering, R-077125, Bucharest, Romania

^* e-mail: anant@cts.iisc.ernet.in

Received: 15 December 2009
Revised: 22 February 2010
Accepted: 15 March 2010
Published online: 9 April 2010

Abstract

We investigate the scalar K form factor at low energies by the method of unitarity bounds adapted so as to include information on the phase and modulus along the elastic region of the unitarity cut. Using at input the values of the form factor at t = 0 and the Callan-Treiman point, we obtain stringent constraints on the slope and curvature parameters of the Taylor expansion at the origin. Also, we predict a quite narrow range for the higher-order ChPT corrections at the second Callan-Treiman point.