Precision measurement of the neutral pion lifetime

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, M. M.; 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, V. V.; Taylor, S.; Vasiliev, A.; Wood, M.; Ye, L.; Zihlmann, B.

doi:10.1126/science.aay6641

Title: Precision measurement of the neutral pion lifetime

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 π ⁰ into two photons (γγ), leading to its unusually short lifetime. We precisely measured the decay width Γ of the $π^{0} \to γ γ$ process. The differential cross sections for π ⁰ photoproduction at forward angles were measured on two targets, carbon-12 and silicon-28, yielding $Γ (π^{0} \to γ γ) = 7.798 \pm 0.056 (stat .) \pm 0.109 (syst .) eV$ , 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 $Γ (π^{0} \to γ γ) = 7.802 \pm 0.052 (stat .) \pm 0.105 (syst .) eV$ . Our final result has a total uncertainty of 1.50% and confirms the prediction based on the chiral anomaly in quantum chromodynamics.

Authors:

^[1];

^[2];

^[3]; Gan, L. ^[4]; Miskimen, R. ^[5];

^[6];

^[7];

^[3]; Pasyuk, E. ^[8]; Gao, H. ^[2];

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^[8]; Burkert, V. ^[8]; Clinton, E. ^[5]; Deur, A. ^[8];

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Alikhanov Institute for Theoretical and Experimental Physics, National Research Center (NRC) “Kurchatov Institute,” Moscow, 117218, Russia., Department of Physics, University of Massachusetts, Amherst, MA 01003, USA.
Department of Physics, Duke University, Durham, NC 27708, USA., Triangle Universities Nuclear Laboratory, Durham, NC 27708, USA.
Department of Physics, North Carolina A&T State University, Greensboro, NC 27411, USA.
Department of Physics and Physical Oceanography, University of North Carolina Wilmington, Wilmington, NC 28403, USA.
Department of Physics, University of Massachusetts, Amherst, MA 01003, USA.
Department of Physics, Norfolk State University, Norfolk, VA 23504, USA.
Department of Physics and Nuclear Engineering, Idaho State University, Pocatello, ID 83209, USA.
Thomas Jefferson National Accelerator Facility, Newport News, VA 23606, USA.
Alikhanov Institute for Theoretical and Experimental Physics, National Research Center (NRC) “Kurchatov Institute,” Moscow, 117218, Russia.
Department of Physics and Astronomy, Mississippi State University, Mississippi State, MS 39762, USA.
Department of Physics, Moscow State University, Moscow 119991, Russia., B. P. Konstantinov Petersburg Nuclear Physics Institute, NRC “Kurchatov Institute,” Gatchina, St. Petersburg, 188300, Russia.
Joint Institute for Nuclear Research, Dubna, 141980, Russia.
Kharkov Institute of Physics and Technology, Kharkov, 310108, Ukraine.
Department of Physics, Florida International University, Miami, FL 33199, USA.
Department of Physics, Moscow State University, Moscow 119991, Russia.
Department of Physics, The Catholic University of America, Washington, DC 20064, USA.
Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
School of Nuclear Science and Technology, Lanzhou University, Lanzhou, 730000, China.
Department of Physics, Arizona State University, Tempe, AZ 85281, USA.
Department of Physics, George Washington University, Washington, DC 20064, USA.
RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan.
Department of Physics, Computer Science and Engineering, Christopher Newport University, Newport News, VA 23606, USA.
School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK.
Department of Physics, Moscow Engineering Physics Institute, Moscow, Russia.
Yerevan Physics Institute, Yerevan 0036, Armenia.
Institute for High Energy Physics, NRC “Kurchatov Institute,” Protvino, 142281, Russia.

Publication Date:: 2020-04-30

Research Org.:: Mississippi State Univ., Mississippi State, MS (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Nuclear Physics (NP); National Science Foundation (NSF)

Contributing Org.:: PrimEx-II Collaboration

OSTI Identifier:: 1616652

Alternate Identifier(s):: OSTI ID: 1778963

Grant/Contract Number:: AC05-06OR23177; FG02-07ER41528; PHY-0079840

Resource Type:: Published Article

Journal Name:: Science

Additional Journal Information:: Journal Name: Science Journal Volume: 368 Journal Issue: 6490; Journal ID: ISSN 0036-8075

Publisher:: AAAS

Country of Publication:: United States

Language:: English

Subject:: 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS

Citation Formats


                    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, M. M., 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, V. V., Taylor, S., Vasiliev, A., Wood, M., Ye, L., Zihlmann, B., and PrimEx-II Collaboration. Precision measurement of the neutral pion lifetime.  United States: N. p., 2020. 
Web.  https://doi.org/10.1126/science.aay6641.

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                    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, M. M., 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, V. V., Taylor, S., Vasiliev, A., Wood, M., Ye, L., Zihlmann, B., & PrimEx-II Collaboration. Precision measurement of the neutral pion lifetime.  United States.  https://doi.org/10.1126/science.aay6641

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                    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, M. M., 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, V. V., Taylor, S., Vasiliev, A., Wood, M., Ye, L., Zihlmann, B., and PrimEx-II Collaboration. Thu .  
"Precision measurement of the neutral pion lifetime".  United States.  https://doi.org/10.1126/science.aay6641.

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@article{osti_1616652,

  title        = {Precision measurement of the neutral pion lifetime},

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

  abstractNote = {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 π 0 into two photons (γγ), leading to its unusually short lifetime. We precisely measured the decay width Γ of the π 0 →   γ γ process. The differential cross sections for π 0 photoproduction at forward angles were measured on two targets, carbon-12 and silicon-28, yielding Γ ( π 0 →   γ γ ) = 7.798 ± 0.056 ( stat . ) ± 0.109 ( syst . )  eV , 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 Γ ( π 0 →   γ γ ) = 7.802 ± 0.052 ( stat . ) ± 0.105 ( syst . )  eV . Our final result has a total uncertainty of 1.50% and confirms the prediction based on the chiral anomaly in quantum chromodynamics.},

  doi          = {10.1126/science.aay6641},

  journal      = {Science},

  number       = 6490,

  volume       = 368,

  place        = {United States},

  year         = {2020},

  month        = {4}

}

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Title: Precision measurement of the neutral pion lifetime

Abstract

Citation Formats

New Precise Measurement of the Pion Weak Form Factors in π + → e + ν γ Decay journal, July 2009

Direct measurement of the lifetime of the neutral pion journal, August 1985

Nuclear charge-density-distribution parameters from elastic electron scattering journal, May 1987

Neutral pion lifetime measurements and the QCD chiral anomaly journal, January 2013

Formation of the pseudoscalars π 0 , η , and η’ in the reaction γγ→γγ journal, September 1988

Decay Width of the Neutral π Meson journal, December 1974

Axial-Vector Vertex in Spinor Electrodynamics journal, January 1969

Incoherent photoproduction of pseudoscalar mesons off nuclei at forward angles journal, January 2012

Review of Particle Physics journal, August 2018

Chiral expansions of the π 0 lifetime journal, April 2009

Photo-Production of Neutral Mesons in Nuclear Electric Fields and the Mean Life of the Neutral Meson journal, March 1951

Electromagnetic corrections in the anomaly sector journal, May 2002

Energy dependence of the form factor for elastic electron scattering from C 12 journal, September 1991

A PCAC puzzle: π0→γγ in the σ-model journal, March 1969

The bremsstrahlung tagged photon beam in Hall B at JLab journal, February 2000

High precision measurement of Compton scattering in the 5 GeV region journal, October 2019

Pion-Pole Contribution to Hadronic Light-By-Light Scattering in the Anomalous Magnetic Moment of the Muon journal, September 2018

New Measurement of the π 0 Radiative Decay Width journal, April 2011

Nuclear targets for a precision measurement of the neutral pion radiative width journal, December 2009

Single- π ± and - K + Photoproduction from Complex Nuclei at 8 and 16 GeV journal, December 1969

Review of Particle Physics journal, September 2008

Decay π 0 → γ γ to next to leading order in chiral perturbation theory journal, October 2002

New Precise Measurement of the Pion Weak Form Factors in $π^{+} \to e^{+} ν γ$ Decay
journal, July 2009

Direct measurement of the lifetime of the neutral pion
journal, August 1985

Nuclear charge-density-distribution parameters from elastic electron scattering
journal, May 1987

Neutral pion lifetime measurements and the QCD chiral anomaly
journal, January 2013

Formation of the pseudoscalars $π^{0}$ , η , and η’ in the reaction γγ→γγ
journal, September 1988

Decay Width of the Neutral $π$ Meson
journal, December 1974

Axial-Vector Vertex in Spinor Electrodynamics
journal, January 1969

Incoherent photoproduction of pseudoscalar mesons off nuclei at forward angles
journal, January 2012

Review of Particle Physics
journal, August 2018

Chiral expansions of the $π^{0}$ lifetime
journal, April 2009

Photo-Production of Neutral Mesons in Nuclear Electric Fields and the Mean Life of the Neutral Meson
journal, March 1951

Electromagnetic corrections in the anomaly sector
journal, May 2002

Energy dependence of the form factor for elastic electron scattering from ${}^{12}C$
journal, September 1991

A PCAC puzzle: π0→γγ in the σ-model
journal, March 1969

The bremsstrahlung tagged photon beam in Hall B at JLab
journal, February 2000

High precision measurement of Compton scattering in the 5 GeV region
journal, October 2019

Pion-Pole Contribution to Hadronic Light-By-Light Scattering in the Anomalous Magnetic Moment of the Muon
journal, September 2018

New Measurement of the $π^{0}$ Radiative Decay Width
journal, April 2011

Nuclear targets for a precision measurement of the neutral pion radiative width
journal, December 2009

Single- $π^{\pm}$ and - $K^{+}$ Photoproduction from Complex Nuclei at 8 and 16 GeV
journal, December 1969

Review of Particle Physics
journal, September 2008

Decay $π^{0} \to γ γ$ to next to leading order in chiral perturbation theory
journal, October 2002