Measurement of the rare decay<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:mo>→</mml:mo><mml:msup><mml:mi>e</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>e</mml:mi><mml:mo>−</mml:mo></mml:msup></mml:math>

Abouzaid, E.; Arenton, M. W.; Barker, A. R.; Bellantoni, L.; Bellavance, A.; Blucher, E.; Bock, G. J.; Cheu, E.; Coleman, R.; Corcoran, M.; Cox, B.; Erwin, A. R.; Escobar, C. O.; Glazov, A.; Golossanov, A.; Gomes, R. A.; Gouffon, P.; Hanagaki, K.; Hsiung, Y.; Huang, H.-C.; Jensen, D.; Keßler, R.; Kotera, Katsushige; Ledovskoy, A.; McBride, P.; Monnier, E.; Nelson, K. S.; Nguyen, H. H.; Niclasen, R.; Phillips, D. G.; Ping, H.; Qi, X. R.; Ramberg, E.; Ray, R. E.; Ronquest, M.; Santos, Edivaldo Moura; Shields, Joseph C.; Slater, W.; Smith, D.; Solomey, N.; Swallow, E. C.; Toale, P. A.; Tschirhart, R.; Velissaris, C.; Wah, Y. W.; Wang, James; White, H. B.; Whitmore, J.; Wilking, M. J.; Winstein, B.; Winston, R.; Worcester, E.; Worcester, M.; Yamanaka, T.; Zimmerman, E. D.; Zukanovich, R. F.

doi:10.1103/physrevd.75.012004

Cited by 92 publications

(82 citation statements)

References 19 publications

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“…These are very rare processes and good knowledge of the TFF is required for the prediction of the branching ratios. The latest measurement of π 0 → e + e − was performed by the KTeV-E779 experiment at Fermilab [66]. The pions are tagged in K L → 3π 0 , where two of the three pions are reconstructed in the two-photon decay mode.…”

Section: Meson Decay Processes Involving Two Virtual Photonsmentioning

confidence: 99%

The hadronic light-by-light contribution to the muon’s anomalous magnetic moment

Danilkin

Redmer

Vanderhaeghen

2019

Progress in Particle and Nuclear Physics

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Section: Meson Decay Processes Involving Two Virtual Photonsmentioning

confidence: 99%

The hadronic light-by-light contribution to the muon’s anomalous magnetic moment

Danilkin

Redmer

Vanderhaeghen

2019

Progress in Particle and Nuclear Physics

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“…In fact, there appears to be a discrepancy in the observed π 0 decay width to e + e − at the ∼ 3σ level. The most precise measurement of this branching ratio, from the KTeV-E778 collaboration [56], is:…”

Section: A the Ktev Anomalymentioning

confidence: 99%

“…The KTeV-E778 collaboration extrapolated its measurement in the exclusive region m 2 ee /m 2 π > 0.95 to obtain the inclusive result with final state radiation removed[56]. Refs [60,61].…”

mentioning

confidence: 99%

A viable QCD axion in the MeV mass range

Alves

Weiner

2018

J. High Energ. Phys.

102

120

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The QCD axion is one of the most compelling solutions of the strong CP problem. There are major current efforts into searching for an ultralight, invisible axion, which is believed to be the only phenomenologically viable realization of the QCD axion. Visible axions with decay constants at or below the electroweak scale are believed to have been long excluded by laboratory searches.Considering the significance of the axion solution to the strong CP problem, we revisit experimental constraints on QCD axions in the O(10 MeV) mass window. In particular, we find a variant axion model that remains compatible with existing constraints. This model predicts new states at the GeV scale coupled hadronically, and a variety of low-energy axion signatures, such as rare meson decays, nuclear de-excitations via axion emission, and production in e + e − annihilation and fixed target experiments. This reopens the possibility of solving the strong CP problem at the GeV scale.

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“…Electromagnetic decays of the pion are particularly interesting because they combine the nonperturbative physics of dynamical mass generation and the associated generation of (pseudo-) Goldstone bosons with the Abelian anomaly and its perturbative elements, thus creating an interesting laboratory for theoretical approaches to non-perturbative QCD. Moreover, the rare decay π 0 → e + e − poses a puzzle since theoretical estimates show a discrepancy with the experimental result from the KTeV E799-II experiment at Fermilab [1,2] of similar magnitude as the muon g-2.…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic decays of the neutral pion

et al. 2017

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We complement studies of the neutral pion transition form factor π 0 → γ ( * ) γ ( * ) with calculations for the electromagnetic decay widths of the processes π 0 → e + e − , π 0 → e + e − γ and π 0 → e + e − e + e − . Their common feature is that the singly-or doubly-virtual transition form factor serves as a vital input that is tested in the non-perturbative low-momentum region of QCD. We determine this form factor from a well-established and symmetry-preserving truncation of the Dyson-Schwinger equations. Our results for the three-and four-body decays match results of previous theoretical calculations and experimental measurements. For the rare decay we employ a numerical method to calculate the process directly by deforming integration contours, which in principle can be generalized to arbitrary integrals as long as the analytic structure of the integrands are known. Our result for the rare decay is in agreement with dispersive calculations but still leaves a 2σ discrepancy between theory and experiment.

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Measurement of the rare decayπ0→e+e−

Cited by 92 publications

References 19 publications

The hadronic light-by-light contribution to the muon’s anomalous magnetic moment

The hadronic light-by-light contribution to the muon’s anomalous magnetic moment

A viable QCD axion in the MeV mass range

Electromagnetic decays of the neutral pion

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