Precision measurement of the neutral pion lifetime

I Larin^{1

2}, Y Zhang^{3

4}, A Gasparian⁵, L Gan⁶, R Miskimen², M Khandaker⁷, D Dale⁸, S Danagoulian⁹, E Pasyuk¹⁰, H Gao^{3

4}, A Ahmidouch⁹, P Ambrozewicz⁹, V Baturin¹⁰, V Burkert¹⁰, E Clinton², A Deur¹⁰, A Dolgolenko¹, D Dutta¹¹, G Fedotov^{12

13}, J Feng⁶, S Gevorkyan¹⁴, A Glamazdin¹⁵, L Guo¹⁶, E Isupov¹², M M Ito¹⁰, F Klein¹⁷, S Kowalski¹⁸, A Kubarovsky¹⁰, V Kubarovsky¹⁰, D Lawrence¹⁰, H Lu¹⁹, L Ma²⁰, V Matveev¹, B Morrison²¹, A Micherdzinska²², I Nakagawa²³, K Park¹⁰, R Pedroni⁹, W Phelps²⁴, D Protopopescu²⁵, D Rimal¹⁶, D Romanov²⁶, C Salgado⁷, A Shahinyan²⁷, D Sober¹⁷, S Stepanyan¹⁰, V V Tarasov¹, S Taylor¹⁰, A Vasiliev²⁸, M Wood², L Ye¹¹, B Zihlmann¹⁰; PrimEx-II Collaboration

Affiliations

¹ Alikhanov Institute for Theoretical and Experimental Physics, National Research Center (NRC) "Kurchatov Institute," Moscow, 117218, Russia.
² Department of Physics, University of Massachusetts, Amherst, MA 01003, USA.
³ Department of Physics, Duke University, Durham, NC 27708, USA.
⁴ Triangle Universities Nuclear Laboratory, Durham, NC 27708, USA.
⁵ Department of Physics, North Carolina A&T State University, Greensboro, NC 27411, USA. gasparan@jlab.org.
⁶ Department of Physics and Physical Oceanography, University of North Carolina Wilmington, Wilmington, NC 28403, USA.
⁷ Department of Physics, Norfolk State University, Norfolk, VA 23504, USA.
⁸ Department of Physics and Nuclear Engineering, Idaho State University, Pocatello, ID 83209, USA.
⁹ Department of Physics, North Carolina A&T State University, Greensboro, NC 27411, USA.
¹⁰ Thomas Jefferson National Accelerator Facility, Newport News, VA 23606, USA.
¹¹ Department of Physics and Astronomy, Mississippi State University, Mississippi State, MS 39762, USA.
¹² Department of Physics, Moscow State University, Moscow 119991, Russia.
¹³ B. P. Konstantinov Petersburg Nuclear Physics Institute, NRC "Kurchatov Institute," Gatchina, St. Petersburg, 188300, Russia.
¹⁴ Joint Institute for Nuclear Research, Dubna, 141980, Russia.
¹⁵ Kharkov Institute of Physics and Technology, Kharkov, 310108, Ukraine.
¹⁶ Department of Physics, Florida International University, Miami, FL 33199, USA.
¹⁷ Department of Physics, The Catholic University of America, Washington, DC 20064, USA.
¹⁸ Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
¹⁹ Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
²⁰ School of Nuclear Science and Technology, Lanzhou University, Lanzhou, 730000, China.
²¹ Department of Physics, Arizona State University, Tempe, AZ 85281, USA.
²² Department of Physics, George Washington University, Washington, DC 20064, USA.
²³ RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan.
²⁴ Department of Physics, Computer Science and Engineering, Christopher Newport University, Newport News, VA 23606, USA.
²⁵ School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK.
²⁶ Department of Physics, Moscow Engineering Physics Institute, Moscow, Russia.
²⁷ Yerevan Physics Institute, Yerevan 0036, Armenia.
²⁸ Institute for High Energy Physics, NRC "Kurchatov Institute," Protvino, 142281, Russia.

PMID: 32355026
DOI: 10.1126/science.aay6641

Precision measurement of the neutral pion lifetime

I Larin et al. Science. 2020.

. 2020 May 1;368(6490):506-509.

doi: 10.1126/science.aay6641.

Authors

Affiliations

¹ Alikhanov Institute for Theoretical and Experimental Physics, National Research Center (NRC) "Kurchatov Institute," Moscow, 117218, Russia.
² Department of Physics, University of Massachusetts, Amherst, MA 01003, USA.
³ Department of Physics, Duke University, Durham, NC 27708, USA.
⁴ Triangle Universities Nuclear Laboratory, Durham, NC 27708, USA.
⁵ Department of Physics, North Carolina A&T State University, Greensboro, NC 27411, USA. gasparan@jlab.org.
⁶ Department of Physics and Physical Oceanography, University of North Carolina Wilmington, Wilmington, NC 28403, USA.
⁷ Department of Physics, Norfolk State University, Norfolk, VA 23504, USA.
⁸ Department of Physics and Nuclear Engineering, Idaho State University, Pocatello, ID 83209, USA.
⁹ Department of Physics, North Carolina A&T State University, Greensboro, NC 27411, USA.
¹⁰ Thomas Jefferson National Accelerator Facility, Newport News, VA 23606, USA.
¹¹ Department of Physics and Astronomy, Mississippi State University, Mississippi State, MS 39762, USA.
¹² Department of Physics, Moscow State University, Moscow 119991, Russia.
¹³ B. P. Konstantinov Petersburg Nuclear Physics Institute, NRC "Kurchatov Institute," Gatchina, St. Petersburg, 188300, Russia.
¹⁴ Joint Institute for Nuclear Research, Dubna, 141980, Russia.
¹⁵ Kharkov Institute of Physics and Technology, Kharkov, 310108, Ukraine.
¹⁶ Department of Physics, Florida International University, Miami, FL 33199, USA.
¹⁷ Department of Physics, The Catholic University of America, Washington, DC 20064, USA.
¹⁸ Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
¹⁹ Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
²⁰ School of Nuclear Science and Technology, Lanzhou University, Lanzhou, 730000, China.
²¹ Department of Physics, Arizona State University, Tempe, AZ 85281, USA.
²² Department of Physics, George Washington University, Washington, DC 20064, USA.
²³ RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan.
²⁴ Department of Physics, Computer Science and Engineering, Christopher Newport University, Newport News, VA 23606, USA.
²⁵ School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK.
²⁶ Department of Physics, Moscow Engineering Physics Institute, Moscow, Russia.
²⁷ Yerevan Physics Institute, Yerevan 0036, Armenia.
²⁸ Institute for High Energy Physics, NRC "Kurchatov Institute," Protvino, 142281, Russia.

PMID: 32355026
DOI: 10.1126/science.aay6641

Abstract

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.

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π⁰ decay precision-tests the chiral anomaly.
Meyer HB. Meyer HB. Science. 2020 May 1;368(6490):469. doi: 10.1126/science.aba8063. Science. 2020. PMID: 32355017 No abstract available.

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Precision measurement of the neutral pion lifetime

Affiliations

Precision measurement of the neutral pion lifetime

Authors

Affiliations

Abstract

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