Virtual Compton scattering measurements in the nucleon resonance region

A. Blomberg; H. Atac; N. Sparveris; M. Paolone; P. Achenbach; M. Benali; J. Beričič; R. Böhm; L. Correa; M. O. Distler; A. Esser; D. Flay; H. Fonvieille; I. Friščić; Y. Kohl; H. Merkel; U. Müller; Z. E. Meziani; M. Mihovilovic; J. Pochodzalla; A. Polychronopoulou; B. Pasquini; M. Schoth; F. Schulz; S. Schlimme; C. Sfienti; S. Sirca; A. Weber

doi:10.1140/epja/i2019-12877-0

EPJ

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2021 Impact factor 3.131

Hadrons and Nuclei

Open Access

Eur. Phys. J. A (2019) 55: 182
https://doi.org/10.1140/epja/i2019-12877-0

Letter

Virtual Compton scattering measurements in the nucleon resonance region

A. Blomberg¹, H. Atac¹, N. Sparveris¹^*, M. Paolone¹, P. Achenbach², M. Benali³, J. Beričič⁴, R. Böhm², L. Correa², M. O. Distler², A. Esser², D. Flay¹, H. Fonvieille³, I. Friščić², Y. Kohl², H. Merkel², U. Müller², Z. E. Meziani¹, M. Mihovilovic⁴, J. Pochodzalla², A. Polychronopoulou¹, B. Pasquini⁵, M. Schoth², F. Schulz², S. Schlimme², C. Sfienti², S. Sirca⁴^,6 and A. Weber²

¹ Temple University, 19122, Philadelphia, PA, USA
² Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, D-55099, Mainz, Germany
³ Clermont Université, Université Blaise Pascal, CNRS/IN2P3, LPC, BP 10448, F-63000, Clermont-Ferrand, France
⁴ Jožef Stefan Institute, SI-1000, Ljubljana, Slovenia
⁵ Dipartimento di Fisica, Università degli Studi di Pavia, I-27100, Pavia, Italy
⁶ Faculty of Mathematics and Physics, University of Ljubljana, SI-1000, Ljubljana, Slovenia

^* e-mail: sparveri@temple.edu

Received: 31 January 2019
Accepted: 5 September 2019
Published online: 22 October 2019

Abstract

We report on new measurements of the electric Generalized Polarizability (GP) of the proton in a kinematic region where a puzzling dependence on momentum transfer has been observed, and we have found that fm³ at (GeV/c)². The new measurements, when considered along with the rest of the world data, suggest that can be described by either a local plateau or by an enhancement in the region (GeV/c)² to 0.33 (GeV/c)². The experiment also provides the first measurement of the Coulomb quadrupole amplitude in the transition through the exploration of the reaction. The new measurement gives at (GeV/c)² and is consistent with the results from the pion electroproduction world data. It has been obtained using a completely different extraction method, and therefore represents a strong validation test of the world data model uncertainties.