Phys. Rev. Lett. 96, 101801 (2006) [5 pages]Measurement of the K0 Charge Radius and a CP-Violating Asymmetry and a Search for CP-Violating E1 Direct Photon Emission in the Rare Decay KL→π+π-e+e-Received 3 August 2005; published 17 March 2006 Using the complete KTeV data set of 5241 candidate KL→π+π-e+e- decays (including an estimated background of 204±14 events), we have measured the coupling gCR=0.163±0.014(stat)±0.023(syst) of the CP conserving charge radius process and from it determined a K0 charge radius of ⟨rK02⟩=[-0.077±0.007(stat)±0.011(syst)]fm2. We have determined a first experimental upper limit of 0.04 (90% C.L.) for the ratio |gE1|/|gM1| of the couplings for the E1 and M1 direct photon emission processes. We also report the measurement of |gM1| including a vector form factor |g˜M1|(1+a1/a2/(Mρ2-MK2)+2MKEγ*), where |g˜M1|=1.11±0.12(stat)±0.08(syst) and a1/a2=[-0.744±0.027(stat)±0.032(syst)] GeV2/c2. Finally, a CP-violating asymmetry of [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 KL center of mass is reported. © 2006 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.96.101801
DOI:
10.1103/PhysRevLett.96.101801
PACS:
13.20.Eb, 13.25.Es, 13.40.Gp, 13.40.Hq
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