Precision measurement of the neutral pion lifetime.

Journal Article (Journal Article)

The explicit breaking of the axial symmetry by quantum fluctuations gives rise to the so-called axial anomaly. This phenomenon is solely responsible for the decay of the neutral pion π0 into two photons (γγ), leading to its unusually short lifetime. We precisely measured the decay width Γ of the [Formula: see text] process. The differential cross sections for π0 photoproduction at forward angles were measured on two targets, carbon-12 and silicon-28, yielding [Formula: see text], where stat. denotes the statistical uncertainty and syst. the systematic uncertainty. We combined the results of this and an earlier experiment to generate a weighted average of [Formula: see text] Our final result has a total uncertainty of 1.50% and confirms the prediction based on the chiral anomaly in quantum chromodynamics.

Full Text

Duke Authors

Cited Authors

  • Larin, I; Zhang, Y; Gasparian, A; Gan, L; Miskimen, R; Khandaker, M; Dale, D; Danagoulian, S; Pasyuk, E; Gao, H; Ahmidouch, A; Ambrozewicz, P; Baturin, V; Burkert, V; Clinton, E; Deur, A; Dolgolenko, A; Dutta, D; Fedotov, G; Feng, J; Gevorkyan, S; Glamazdin, A; Guo, L; Isupov, E; Ito, MM; Klein, F; Kowalski, S; Kubarovsky, A; Kubarovsky, V; Lawrence, D; Lu, H; Ma, L; Matveev, V; Morrison, B; Micherdzinska, A; Nakagawa, I; Park, K; Pedroni, R; Phelps, W; Protopopescu, D; Rimal, D; Romanov, D; Salgado, C; Shahinyan, A; Sober, D; Stepanyan, S; Tarasov, VV; Taylor, S; Vasiliev, A; Wood, M; Ye, L; Zihlmann, B; PrimEx-II Collaboration,

Published Date

  • May 2020

Published In

Volume / Issue

  • 368 / 6490

Start / End Page

  • 506 - 509

PubMed ID

  • 32355026

Electronic International Standard Serial Number (EISSN)

  • 1095-9203

International Standard Serial Number (ISSN)

  • 0036-8075

Digital Object Identifier (DOI)

  • 10.1126/science.aay6641


  • eng