Friday, July 26, 2013

1307.6587 (Kamal K. Seth et al.)

First Measurement of the Neutral Kaon Form Factor and the Effect of
SU(3) Breaking

Kamal K. Seth, S. Dobbs, A. Tomaradze, T. Xiao, G. Bonvicini
At large momentum transfers the photon interacts with the constituent partons in a hadron and a neutral hadron acquires an electromagnetic form factor. Open flavor neutral mesons are expected to acquire finite electromagnetic form factors because their wave functions are affected by the differences in the masses of the different flavor quarks which they contain. For neutral kaons this corresponds to SU(3) breaking. We report on the first measurement of the form factor of neutral kaons at the large timelike momentum transfer of |Q^2|=17.4 GeV^2 by measuring the cross section for e+e- -> KSKL at sqrt{s} = 4.17 GeV using CLEO-c data with an integrated luminosity of 586 pb^-1. We obtain F_KSKL(17.4 GeV^2) = 3.9 x 10^-3, with a 90% confidence interval of (0-7.0) x 10^-3. This is an order of magnitude smaller than F_K+K-(17.4 GeV^2), and indicates that the effect of SU(3) breaking is small. The small SU(3) breaking effect which we find makes it unlikely that the recently observed strong violation of the pQCD prediction, $F_pi+pi-(|Q^2|)/F_K+K-(|Q^2|) = f_\pi^2/f_K^2, which is based on the assumption of similar wave functions for the pions and kaons, can be attributed to SU(3) breaking alone.
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