| Title: |
Hard Two-Photon Contribution to Elastic Lepton-Proton Scattering Determined by the OLYMPUS Experiment |
| Authors: |
Henderson, Brian; Ice, Lauren; Ates, Ozgur; Avetisyan, Albert; Beck, Reinhard; Belostotski, Stanislav; Bessuille, Jason; Brinker, Frank; Calarco, John; Carassiti, V.; Cisbani, E.; Ciullo, G.; Khaneft, Dmitry; Contalbrigo, Marco; De Leo, R.; Diefenbach, Juergen; Donnelly, T. W.; Dow, Karen; Elbakian, G.; Eversheim, P. D.; Frullani, Salvatore; Funke, Christian; Gavrilov, Gennady; O'Connor, Colton; Gläser, B.; Goerrissen, Nico; Hasell, Douglas; Hauschildt, Jan; Hoffmeister, Philipp; Holler, Yorck; Ihloff, E.; Izotov, Anton; Kaiser, Ralf; Karyan, Gevorg; Russell, Rebecca; Kelsey, James; Kiselev, Alexander; Klassen, Peter; Krivshich, A.; Lehmann, Inti; Lenisa, Paolo; Lenz, Dennis; Lumsden, S.; Ma, Yue; Maas, Frank; Schmidt, Axel; Marukyan, Hrachya; Miklukho, Oleg; Milner, Richard; Movsisyan, Aram; Murray, Morgan; Naryshkine, Iouri; Perez Benito, R.; Perrino, R.; Redwine, Robert; Rodriguez Pineiro, David; Bernauer, Jan; Rosner, G.; Schneekloth, Uwe; Seitz, B.; Statera, M.; Thiel, A.; Vardanyan, Henrik; Veretennikov, Denis; Vidal, C.; Winnebeck, Alexander; Yeganov, Vladislav; Kohl, Michael; OLYMPUS Collaboration; Akopov, Norair; Alarcon, Ricardo |
| Source: |
Physical review letters 118(9), 092501 (2017). doi:10.1103/PhysRevLett.118.092501 |
| Publisher Information: |
APS |
| Publication Year: |
2017 |
| Collection: |
DESY Publication Database (PUBDB) |
| Subject Terms: |
info:eu-repo/classification/ddc/550 |
| Subject Geographic: |
DE |
| Description: |
The OLYMPUS collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio, $\it R_{2 \gamma}$, a direct measure of the contribution of hard two-photon exchange to the elastic cross section. In the OLYMPUS measurement, 2.01 GeV electron and positron beams were directed through a hydrogen gas target internal to the DORIS storage ring at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight scintillators detected elastically scattered leptons in coincidence with recoiling protons over a scattering angle range of $\approx$ 20° to 80°. The relative luminosity between the two beam species was monitored using tracking telescopes of interleaved GEM and MWPC detectors at 12°, as well as symmetric Møller/Bhabha calorimeters at 1:29°. A total integrated luminosity of $4.5 fb^{-1}$ was collected. In the extraction of $\it R_{2\gamma}$, radiative effects were taken into account using a Monte Carlo generator to simulate the convolutions of internal bremsstrahlung with experiment-specific conditions such as detector acceptance and reconstruction efficiency. The resulting values of $\it R_{2\gamma}$, presented here for a wide range of virtual photon polarization 0:456 < $\epsilon$< 0:978, are smaller than hadronic two-photon exchange calculations predict, but are consistent with phenomenological models. |
| Document Type: |
article in journal/newspaper |
| Language: |
English |
| ISSN: |
0031-9007 |
| Relation: |
info:eu-repo/semantics/altIdentifier/arxiv/arXiv:1611.04685; info:eu-repo/semantics/altIdentifier/wos/WOS:000396045900004; info:eu-repo/semantics/altIdentifier/pmid/pmid:28306315; info:eu-repo/semantics/altIdentifier/issn/0031-9007 |
| Availability: |
https://bib-pubdb1.desy.de/record/315044; https://bib-pubdb1.desy.de/search?p=id:%22PUBDB-2016-05579%22 |
| Rights: |
info:eu-repo/semantics/openAccess |
| Accession Number: |
edsbas.DED399CE |
| Database: |
BASE |