First Measurement of Timelike Compton Scattering

DOI

10.1103/PhysRevLett.127.262501

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

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