[en] The cross section for WW production is measured and limits on anomalous WWγ and WWZ trilinear gauge couplings are set using WW → ee/eμ/μμ events collected by the Run II D0 detector at the Fermilab Tevatron Collider corresponding to 1 fb^-1 of integrated luminosity at √s = 1.96 TeV. Across the three final states, 108 candidate events are observed with 40.8 ± 3.8 total background expected, consistent with σ(p(bar p) → WW) = 11.6 ± 1.8(stat) ± 0.7(syst) ± 0.7(lumi) pb. Using a set of SU(2)_L (direct_product) U(1)_Y conserving constraints, the one-dimensional 95% C.L. limits on trilinear gauge couplings are -0.63 < Δκ_γ < 0.99, -0.15 < λ_γ < 0.19, and -0.14 < Δg₁^Z < 0.34

[en] The authors report on a new measurement of the branching ratio B(K_L → π⁰γγ) using the KTeV detector. They reconstruct 1982 events with an estimated background of 608, that results in B(K_L → π⁰Γγ) = (1.29 ± 0.03_stat ± 0.05_syst) x 10^-6. They also measure the parameter, a_V, which characterizes the strength of vector meson exchange terms in this decay. They find a_V = -0.31 ± 0.05_stat ± 0.07_syst. These results utilize the full KTeV data set collected from 1997 to 2000 and supersede earlier KTeV measurements of the branching ratio and a_V

[en] Using the complete KTeV data set of 5241 candidate K_L → π⁺π^-e⁺e^- decays (including an estimated background of 204 ± 14 events), we have measured the coupling g_CR = 0.163 ± 0.014 (stat) ± 0.023 (syst) of the CP conserving charge radius process and from it determined a K⁰ charge radius of < r_K#sup 0#²> = (-0.077 ± 0.007(stat) ± 0.011(syst))fm². We have also determined a first experimental upper limit of 0.04 (90% CL) for the ratio |g_E1|/|g_M1| of the coupling for the E1 direct photon emission process relative to the coupling for M1 direct photon emission process. We also report the measurement of |g_M1| including its associated vector form factor |(bar g)_M1|1 + a₁/a₂/(M_p² - M_K²)+2M_KE_γ* where |(bar g)_M1| = 1.11 ± 0.12 (stat) ± 0.08 (syst) and a₁/a₂ = (-0.744 ± 0.027 (stat) ± 0.032 (syst)) GeV²/c². In addition, a measurement of the manifestly CP violating asymmetry of magnitude (13.6 ± 1.4 (stat) ± 1.5 (syst))% in the CP and T odd angle φ between the decay planes of the e⁺e^- and π⁺π^- pairs in the K center of mass system is reported

[en] In this paper the KTeV collaboration reports the analysis of 112.1 x 10³ candidate K_L → π⁺π^-γ decays including a background of 671 ± 41 events with the objective of determining the photon production mechanisms intrinsic to the decay process. These decays have been analyzed to extract the relative contributions of the Cp violating bremsstrahlung process and the CP conserving M1 and CP violating E1 direct photon emission processes. The M1 direct photon emission amplitude and its associated vector form factor parameterized as |(bar g)_M1|(1 + a₁/a₂/(M_ρ²-M_K²) + 2M_KE_γ) have been measured to be |(bar g)_M1| = 1.198 ± 0.035(stat) ± 0.086(syst) and a₁/a₂ = =0.738 ± 0.007(stat) ± 0.018(syst) GeV²/c² respectively. An upper limit for the CP violating E1 direct emission amplitude |g_E1| (le) 0.1 (90%CL) has been found. The overall ratio of direct photon emission (DE) to total photon emission including the bremsstrahlung process (IB) has been determined to be DE/(DE + IB) = 0.689 ± 0.021 for E_γ (ge) 20 MeV

[en] Using the published KTeV samples of K_L → π^±e^±ν and K_L → π^±μ^±ν decays, we perform a reanalysis of the scalar and vector form factors based on the dispersive parameterization. We obtain phase space integrals I_K^e = 0.15446 ± 0.00025 and I_K^μ = 0.10219 ± 0.00025. For the scalar form factor parameterization, the only free parameter is the normalized form factor value at the Callan-Treiman point (C); our best fit results in ln C = 0.1915 ± 0.0122. We also study the sensitivity of C to different parametrizations of the vector form factor. The results for the phase space integrals and C are then used to make tests of the Standard Model. Finally, we compare our results with lattice QCD calculations of F_K/F_π and f₊(0).