Determination of the Parity of the Neutral Pion via the Four-Electron Decay
hep-ex
/ Authors
E. Abouzaid, M. Arenton, A. R. Barker, L. Bellantoni, E. Blucher, G. J. Bock, E. Cheu, R. Coleman, M. D. Corcoran, B. Cox
and 37 more authors
A. R. Erwin, C. O. Escobar, A. Glazov, A. Golossanov, R. A. Gomes, P. Gouffon, Y. B. Hsiung, D. A. Jensen, R. Kessler, K. Kotera, A. Ledovskoy, P. L. McBride, E. Monnier, H. Nguyen, R. Niclasen, D. G. Phillips, E. J. Ramberg, R. E. Ray, M. Ronquest, E. Santos, W. Slater, D. Smith, N. Solomey, E. C. Swallow
/ Abstract
We present a new determination of the parity of the neutral pion via the double Dalitz decay pi^0 -> e+ e- e+ e-. Our sample, which consists of 30511 candidate decays, was collected from K_L -> pi0 pi0 pi0 decays in flight at the KTeV-E799 experiment at Fermi National Accelerator Laboratory. We confirm the negative pi^0 parity, and place a limit on scalar contributions to the pi^0 -> e+ e- e+ e- decay amplitude of less than 3.3% assuming CPT conservation. The pi^0 gamma* gamma* form factor is well described by a momentum-dependent model with a slope parameter fit to the final state phase space distribution. Additionally, we have measured the branching ratio of this mode to be B(pi^0 -> e+ e- e+ e-) = (3.26 +- 0.18) x 10^(-5).