First measurement of the electromagnetic form factor of the neutral kaon at a large momentum transfer and the effect of [formula omitted] breaking

Kamal K Seth,S Dobbs,A Tomaradze,T Xiao,G Bonvicini

doi:10.1016/j.physletb.2014.02.003

Kamal K Seth, S Dobbs + Show 3 more

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https://doi.org/10.1016/j.physletb.2014.02.003

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Abstract

At large momentum transfers the photon interacts with the charges and spins of the constituent partons in a hadron. It is expected that the neutral kaon can acquire finite electromagnetic form factors because its wave function is affected by the order of magnitude difference between the mass of the strange quark and that of the down quark, or flavor SU(3) breaking. We report on the first measurement of the form factor of neutral kaons at the large timelike momentum transfer of |Q2|=17.4 GeV2 by measuring the cross section for e+e−→KSKL at s=4.17 GeV using CLEO-c data with an integrated luminosity of 586 pb−1. We obtain FKSKL(17.4 GeV2)=5.3×10−3, with a 90% C.L. interval of (2.9–8.2)×10−3. This is nearly an order of magnitude smaller than FK+K−(17.4 GeV2)=(44±1)×10−3, and indicates that the effect of SU(3) breaking is small. In turn, this makes it unlikely that the recently observed strong violation of the pQCD prediction, Fπ+π−(|Q2|)/FK+K−(|Q2|)=fπ2/fK2, which is based on the assumption of similar wave functions for the pions and kaons, can be attributed to SU(3) breaking alone.

Highlights

As the fundamental theory of the strong interaction
One of the most important tools for the study of the internal structure of hadrons is the measurement of their electromagnetic form factors at large momentum transfers at which the probe photon sees the charges and spins of the quarks and gluons in the hadron rather than the composite hadron
With the strange quark being more than an order of magnitude more massive than the up/down quarks [1] the S U(3) flavor symmetry is broken in the kaon, and its wave function acquires an antisymmetric component

Summary

Introduction

As the fundamental theory of the strong interaction. One of the most important tools for the study of the internal structure of hadrons is the measurement of their electromagnetic form factors at large momentum transfers at which the probe photon sees the charges and spins of the quarks and gluons in the hadron rather than the composite hadron. According to perturbative QCD (pQCD), measurement of the form factor of the neutral kaon at a large momentum transfer provides a sensitive measure of the effect of S U(3) The existing measurements of timelike form factors of neutral kaons are limited to small momentum transfers [3, 4].

Results

Conclusion