Search for two photon exchange from e+ +eto p+bar p +gamma data.pdfVIP

Search for two photon exchange from e+ + e− → p + p¯ + γ data E. Tomasi-Gustafsson DAPNIA/SPhN, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France E. A. Kuraev, S. Bakmaev JINR-BLTP, 141980 Dubna, Moscow region, Russian Federation 7 0 0 S. Pacetti 2 t Centro Studi e Ricerche Enrico Fermi, Roma c O and INFN, Laboratori Nazionali di Frascati, Italy 2 (Dated: February 2, 2008) ] h Abstract p - p We look for asymmetries in the angular distributions of events from recent data on e+ +e− → p + e h p¯+ γ from BABAR collaboration. From first principles, as the C-invariance of the electromagnetic [ 1 interaction and the crossing symmetry, the presence of two-photon exchange would create a forward v 4 backward asymmetry in the data. The analysis of the available data shows no asymmetry, within 5 4 an error of 2%. This result is consistent with a structureless model for the proton, based on 0 0. a calculation of e+ + e− → µ+ + µ− + γ with a proper replacement of the muon mass. As 1 7 no systematic deviations are seen, we can conclude that these data do not give any hint of the 0 : presence of the two photon contribution, in all the considered kinematical range. v i X r PACS numbers: a 1 The hadron structure is preferentially investigated using electromagnetic probes, assum- ing that the interaction occurs through one photon exchange. The formalism of elastic, inelastic, polarized or unpolarized processes can