First Measurement of Timelike Compton Scattering

DOI

10.1103/PhysRevLett.127.262501

Authors

• P Chatagnon, Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France.
• S Niccolai, Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France.
• S Stepanyan, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA.
• M J. Amaryan, Old Dominion University, Norfolk, Virginia 23529, USA.
• G Angelini, The George Washington University, Washington, D.C. 20052, USA.
• W R. Armstrong, Argonne National Laboratory, Argonne, Illinois 60439, USA.
• H Atac, Temple University, Philadelphia, Pennsylvania 19122, USA.
• C Ayerbe Gayoso, College of William and Mary, Williamsburg, Virginia 23187-8795, USA.
• N A. Baltzell, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA.
• L Barion, INFN, Sezione di Ferrara, 44100 Ferrara, Italy.
• M Bashkanov, University of York, York YO10 5DD, United Kingdom.
• M Battaglieri, INFN, Sezione di Genova, 16146 Genova, Italy.
• I Bedlinskiy, National Research Centre Kurchatov Institute-ITEP, Moscow, 117259, Russia.
• F Benmokhtar, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, USA.
• A Bianconi, INFN, Sezione di Pavia, 27100 Pavia, Italy.
• L Biondo, INFN, Sezione di Genova, 16146 Genova, Italy.
• A S. Biselli, Fairfield University, Fairfield, Connecticut 06824, USA.
• M Bondi, INFN, Sezione di Genova, 16146 Genova, Italy.
• F Bossù, IRFU, CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France.
• S Boiarinov, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA.
• W J. Briscoe, The George Washington University, Washington, D.C. 20052, USA.
• W K. Brooks, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA.
• D Bulumulla, Old Dominion University, Norfolk, Virginia 23529, USA.
• V D. Burkert, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA.
• D S. Carman, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA.
• J C. Carvajal, Florida International University, Miami, Florida 33199, USA.
• M Caudron, Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France.
• A Celentano, INFN, Sezione di Genova, 16146 Genova, Italy.
• T Chetry, Mississippi State University, Mississippi State, Mississippi 39762-5167, USA.
• G Ciullo, Universita' di Ferrara, 44121 Ferrara, Italy.
• L Clark, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
• P L. Cole, Lamar University, 4400 M. L. King, Jr. Boulevard, P.O. Box 10046, Beaumont, Texas 77710, USA.

Document Type

Journal Article

Publication Date

12-24-2021

Publication Title

Physical review letters

Volume

127

Issue

26

First Page

262501

Abstract

We present the first measurement of the timelike Compton scattering process, γp→p^{'}γ^{*}(γ^{*}→e^{+}e^{-}), obtained with the CLAS12 detector at Jefferson Lab. The photon beam polarization and the decay lepton angular asymmetries are reported in the range of timelike photon virtualities 2.25 < Q^{'2} < 9  GeV^{2}, squared momentum transferred 0.1 < -t < 0.8  GeV^{2}, and average total center-of-mass energy squared s=14.5  GeV^{2}. The photon beam polarization asymmetry, similar to the beam-spin asymmetry in deep virtual Compton scattering, is sensitive to the imaginary part of the Compton form factors and provides a way to test the universality of the generalized parton distributions. The angular asymmetry of the decay leptons accesses the real part of the Compton form factors and thus the D-term in the parametrization of the generalized parton distributions.

Open Access

Green Final

Preprint

https://arxiv.org/abs/2108.11746

Repository Citation

Chatagnon, P., Niccolai, S., Stepanyan, S., Amaryan, M. J., Angelini, G., Armstrong, W. R., Atac, H., Ayerbe Gayoso, C., Baltzell, N. A., Barion, L., Bashkanov, M., Battaglieri, M., Bedlinskiy, I., Benmokhtar, F., Bianconi, A., Biondo, L., Biselli, A. S., Bondi, M., Bossù, F., Boiarinov, S., Briscoe, W. J., Brooks, W. K., Bulumulla, D., Burkert, V. D., Carman, D. S., Carvajal, J. C., Caudron, M., Celentano, A., Chetry, T., Ciullo, G., Clark, L., & Cole, P. L. (2021). First Measurement of Timelike Compton Scattering. Physical review letters, 127 (26), 262501. https://doi.org/10.1103/PhysRevLett.127.262501