High Precision Measurements of the Form Factors of Pion, Kaon, and Proton at Large Timelike Momentum Transfers

TL;DR

This paper reports high-precision measurements of the electromagnetic form factors of protons, pions, and kaons at large timelike momentum transfers, confirming some pQCD predictions and revealing new insights into proton form factor behavior.

Contribution

It provides the first high-precision measurements of these form factors at large |Q^2|, testing perturbative QCD predictions and highlighting differences in proton form factor behavior.

Findings

Q^2F(Q^2) nearly constant for pions and kaons at large Q^2

Significant difference observed in proton form factor behavior at different Q^2 values

Results support the constancy of |Q^2|G_M(|Q^2|)/mu_p for protons

Abstract

High precision measurements of the form factors of proton, pion, and kaon for timelike momentum transfers of |Q^2|=s=14.2 and 17.4 GeV^2 have been made. Data taken with the CLEO-c detector at sqrt(s)=3.772 GeV and 4.170 GeV, with integrated luminosities of 805 pb^-1 and 586 pb^-1, respectively, have been used to study $e^+e^-$ annihilations into pi+pi-, K+K^-, and ppbar. The perturbative QCD prediction that at large Q^2 the quantity Q^2F(Q^2) for vector mesons is nearly constant, and varies only weakly as the strong coupling constant alpha_S(Q^2) is confirmed for both pions and kaons. In contrast, a significant difference is observed between the values of the corresponding pQCD suggested near-constant quantity, |Q^4|G_M(|Q^2|)/mu_p for protons at |Q^2|=14.2 GeV^2 and 17.4 GeV^2. The results suggest the constancy of |Q^2|G_M(|Q^2|)/mu_p, instead.