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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   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.

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