Measurements of the decay KL-->e+ e- gamma

Area of Science:

• Particle Physics
• High Energy Physics
• Experimental Physics

Background:

• Neutral kaon decays offer insights into fundamental particle physics.
• Previous measurements of K(L)-->e+e-gamma(gamma) decay had limited precision.
• Understanding kaon form factors is essential for testing the Standard Model.

Purpose of the Study:

• To precisely measure the decay width of K(L)-->e+e-gamma(gamma).
• To determine parameters of K(L)gamma*gamma form factor models.
• To provide high-precision data for theoretical calculations in particle physics.

Main Methods:

• Analysis of 83,262 K(L)-->e+e-gamma(gamma) events collected by the E799-II experiment at Fermilab.
• Normalization of the measured decay width to the K(L)-->pi0pi0pi(D)0 decay.
• Fitting experimental data to two distinct K(L)gamma*gamma form factor models: Bergström-Massó-Singer and D'Ambrosio-Isidori-Portolés.

Main Results:

• Measured Gamma(K(L)-->e+e-gamma(gamma))/Gamma(K(L)-->pi0pi0pi(D)0) = (1.3302 ± 0.0046(stat) ± 0.0102(syst)) x 10(-3).
• Determined the Bergström-Massó-Singer parameter Calpha(K*) = -0.517 ± 0.030(stat) ± 0.022(syst).
• Determined the D'Ambrosio-Isidori-Portolés parameter alpha(DIP) = -1.729 ± 0.043(stat) ± 0.028(syst).

Conclusions:

• The E799-II experiment has provided the most precise measurement to date of the K(L)-->e+e-gamma(gamma) decay width.
• The results offer stringent constraints on theoretical models of K(L)gamma*gamma form factors.
• This data advances our understanding of rare kaon decays and tests of the Standard Model.