Determination of the parity of the neutral pion via its four-electron decay

E Abouzaid; M Arenton; A R Barker; L Bellantoni; E Blucher; G J Bock; E Cheu; R Coleman; M D Corcoran; B Cox; 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 2nd; E J Ramberg; R E Ray; M Ronquest; E Santos; W Slater; D Smith; N Solomey; E C Swallow; P A Toale; R Tschirhart; Y W Wah; J Wang; H B White; J Whitmore; M J Wilking; B Winstein; R Winston; E T Worcester; T Yamanaka; E D Zimmerman; R F Zukanovich; KTeV Collaboration

doi:10.1103/PhysRevLett.100.182001

Determination of the parity of the neutral pion via its four-electron decay

Phys Rev Lett. 2008 May 9;100(18):182001. doi: 10.1103/PhysRevLett.100.182001. Epub 2008 May 6.

Affiliation

¹ The Enrico Fermi Institute, The University of Chicago, Chicago, Illinois 60637, USA.

PMID: 18518364
DOI: 10.1103/PhysRevLett.100.182001

Abstract

We present a new determination of the parity of the neutral pion via the double Dalitz decay pi0-->e+e-e+e-. Our sample, which consists of 30,511 candidate decays, was collected from KL-->pi0pi0pi0 decays in flight at the KTeV-E799 experiment at Fermi National Accelerator Laboratory. We confirm the negative pi0 parity and place a limit on scalar contributions to the pi0-->e+e-e+e- decay amplitude of less than 3.3% assuming CPT conservation. The pi0gamma*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(pi0-->e+e-e+e-)=(3.26+/-0.18)x10(-5).