تقرير
Hard Two-Photon Contribution to Elastic Lepton-Proton Scattering: Determined by the OLYMPUS Experiment
| العنوان: | Hard Two-Photon Contribution to Elastic Lepton-Proton Scattering: Determined by the OLYMPUS Experiment |
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| المؤلفون: | Henderson, B. S., Ice, L. D., Khaneft, D., O'Connor, C., Russell, R., Schmidt, A., Bernauer, J. C., Kohl, M., Akopov, N., Alarcon, R., Ates, O., Avetisyan, A., Beck, R., Belostotski, S., Bessuille, J., Brinker, F., Calarco, J. R., Carassiti, V., Cisbani, E., Ciullo, G., Contalbrigo, M., De Leo, R., Diefenbach, J., Donnelly, T. W., Dow, K., Elbakian, G., Eversheim, P. D., Frullani, S., Funke, Ch., Gavrilov, G., Gläser, B., Görrissen, N., Hasell, D. K., Hauschildt, J., Hoffmeister, Ph., Holler, Y., Ihloff, E., Izotov, A., Kaiser, R., Karyan, G., Kelsey, J., Kiselev, A., Klassen, P., Krivshich, A., Lehmann, I., Lenisa, P., Lenz, D., Lumsden, S., Ma, Y., Maas, F., Marukyan, H., Miklukho, O., Milner, R. G., Movsisyan, A., Murray, M., Naryshkin, Y., Benito, R. Perez, Perrino, R., Redwine, R. P., Piñeiro, D. Rodríguez, Rosner, G., Schneekloth, U., Seitz, B., Statera, M., Thiel, A., Vardanyan, H., Veretennikov, D., Vidal, C., Winnebeck, A., Yeganov, V. |
| المصدر: | Phys. Rev. Lett. 118, 092501 (2017) |
| سنة النشر: | 2016 |
| المجموعة: | Nuclear Experiment |
| مصطلحات موضوعية: | Nuclear Experiment |
| الوصف: | The OLYMPUS collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio, $R_{2\gamma}$, 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 $\approx 20\degree$ to $80\degree$. The relative luminosity between the two beam species was monitored using tracking telescopes of interleaved GEM and MWPC detectors at $12\degree$, as well as symmetric M{\o}ller/Bhabha calorimeters at $1.29\degree$. A total integrated luminosity of 4.5~fb$^{-1}$ was collected. In the extraction of $R_{2\gamma}$, 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 $R_{2\gamma}$, presented here for a wide range of virtual photon polarization $0.456<\epsilon<0.978$, are smaller than some hadronic two-photon exchange calculations predict, but are in reasonable agreement with a subtracted dispersion model and a phenomenological fit to the form factor data. Comment: 5 pages, 3 figures, 2 tables |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1103/PhysRevLett.118.092501 |
| الوصول الحر: | http://arxiv.org/abs/1611.04685Test |
| رقم الانضمام: | edsarx.1611.04685 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1103/PhysRevLett.118.092501 |
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