Measurement of the Charge-Averaged Elastic Lepton-Proton Scattering Cross Section by the OLYMPUS Experiment

Bernauer, J. C.; Schmidt, Axel; Henderson, Brian S.; Ice, Lauren; Khaneft, D.; O'Connor, Colton; Russell, Rebecca L.; Акопов, Н.; Alarcón, R.; Ates, O.; Avetisyan, A.; Beck, R.; Belostotski, S.; Bessuille, J.; Brinker, Frank; Calarco, J. R.; Carassiti, V.; Cisbani, E.; Ciullo, G.; Contalbrigo, M.; Лео, Р. Де; Diefenbach, J.; Donnelly, T. W.; Dow, K.; Elbakian, G.; Eversheim, P.D.; Frullani, S.; Funke, Ch.; Gavrilov, G.; Gläser, B.; Görrissen, N.; Hasell, D.; Hauschildt, J.; Hoffmeister, P.; Holler, Y.; Ihloff, E.; Izotov, A.; Kaiser, R.; Karyan, G.; Kelsey, J.; Kiselev, A.; Klassen, P.; Krivshich, A.; Köhl, M.; Lehmann, I.; Lenisa, P.; Lenz, Dan; Lumsden, S.; Ma, Yue; Maas, F. E.; Marukyan, H.; Miklukho, O. V.; Milner, R.; Movsisyan, A.; Murray, M.; Naryshkin, Y.; Benito, R. Pérez; Perrino, R.; Redwine, R.; Piñeiro, D. Rodríguez; Rosner, G.; Schneekloth, U.; Seitz, B.; Statera, M.; Thiel, A.; Vardanyan, H.; Veretennikov, D.; Vidal, C.; Winnebeck, A.; Yeganov, V.

doi:10.1103/physrevlett.126.162501

Cited by 10 publications

(10 citation statements)

References 38 publications

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“…The results [16] are shown in Fig. 3, in comparison to other recent global fits of proton cross section data [23][24][25][26].…”

Section: Resultsmentioning

confidence: 82%

“…Determining absolute cross sections was difficult for OLYMPUS, which was designed to measure cross section ratios in which the effects of acceptance, efficiency, and absolute luminosity normalization largely cancel. Nevertheless, the over-determined kinematics in elastic scattering The charge-averaged cross section as measured by OLYMPUS [16], compared to other recent proton form-factor predictions [23][24][25][26]. A normalization uncertainty of ±7.5% is not shown.…”

Section: Charge-averaged Cross Section Analysismentioning

confidence: 98%

“…One of these recent experiments, OLYMPUS, has recently published absolute cross sections for both electron and positron elastic scattering [16]. The average of the two-the lepton charge averaged cross section-has the convenient feature of being insensitive to two-photon exchange effects at lowest order.…”

Section: Unpolarized Global Fitmentioning

confidence: 99%

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Charged-averaged elastic lepton-proton scattering cross section results from OLYMPUS

Schmidt¹

2021

Preprint

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Measurements of the proton's form factor ratio made with polarization transfer show a striking discrepancy relative to the ratio extracted from unpolarized elastic electron-proton scattering cross sections. One hypothesis is that the discrepancy is caused by hard two-photon exchange (TPE), a typically neglected radiative correction that may bias the two approaches differently. This hypothesis has been challenging to confirm. Theoretical estimates of TPE are model-dependent, and recent experimental determinations of TPE lacked the kinematic reach to be conclusive. The possible impact of TPE remains a cloud over our knowledge of the proton's form factors. Recently, the OLYMPUS experiment published new elastic scattering cross sections that are insensitive to the effects of TPE: specifically the average of electron-proton and positron-proton cross sections. The OLYMPUS experiment, conducted at DESY, Hamburg, measured elastic 𝑒 − 𝑝 and 𝑒 + 𝑝 scattering by detecting the scattered lepton and recoiling proton in coincidence in a large-acceptance, toroidal magnetic spectrometer. OLYMPUS was designed to measure the 𝑒 + 𝑝/𝑒 − 𝑝 cross section raio to isolate the effects of TPE. By exploiting the over determined kinematics of the reaction, the absolute efficiency of spectrometer could be verified, allowing cross sections to be extracted from the data. These results can help refine our knowledge of the proton's form factors, especially in the squared momentum-transfer region of 1-2 GeV 2 , where some previous measurements are in tension.

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“…The results [16] are shown in Fig. 3, in comparison to other recent global fits of proton cross section data [23][24][25][26].…”

Section: Resultsmentioning

confidence: 82%

Section: Charge-averaged Cross Section Analysismentioning

confidence: 98%

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Charged-averaged elastic lepton-proton scattering cross section results from OLYMPUS

Schmidt¹

2021

Preprint

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show abstract

“…One of these recent experiments, OLYMPUS, has recently published absolute cross sections for both electron and positron elastic scattering [14]. The average of the two-the lepton charge averaged cross section-has the convenient feature of being insensitive to two-photon exchange effects at lowest order.…”

Section: Introductionmentioning

confidence: 99%

Charge-averaged elastic lepton-proton scattering cross section results from OLYMPUS

Schmidt¹

2022

Proceedings of Particles and Nuclei International Conference 2021 — PoS(PANIC2021)

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Measurements of the proton's form factor ratio made with polarization transfer show a striking discrepancy relative to the ratio extracted from unpolarized elastic electron-proton scattering cross sections. One hypothesis is that the discrepancy is caused by hard two-photon exchange (TPE), a typically neglected radiative correction that may bias the two approaches differently. This hypothesis has been challenging to confirm. Theoretical estimates of TPE are model-dependent, and recent experimental determinations of TPE lacked the kinematic reach to be conclusive. The possible impact of TPE remains a cloud over our knowledge of the proton's form factors. Recently, the OLYMPUS experiment published new elastic scattering cross sections that are insensitive to the effects of TPE: specifically the average of electron-proton and positron-proton cross sections. The OLYMPUS experiment, conducted at DESY, Hamburg, measured elastic − and + scattering by detecting the scattered lepton and recoiling proton in coincidence in a large-acceptance, toroidal magnetic spectrometer. OLYMPUS was designed to measure the + / − cross section ratio to isolate the effects of TPE. By exploiting the over determined kinematics of the reaction, the absolute efficiency of spectrometer could be verified, allowing cross sections to be extracted from the data. These results can help refine our knowledge of the proton's form factors, especially in the squared momentum-transfer region of 1-2 GeV 2 , where some previous measurements are in tension.

show abstract

“…An in-depth review can be found in [3]. Previous measurements [4,5] observed a small (∼1%) "hard" two-photon exchange contribution but were limited to relatively low Q 2 (< 2.1 (GeV/c) 2 ) where the proton form factor discrepancy is not clear. TPEX would make measurements at Q 2 up to 4.6 (GeV/c) 2 where the discrepancy is more obvious.…”

mentioning

confidence: 99%

Test of streaming and triggered readout schemes for the TPEX Lead Tungstate Calorimeter

I.¹,

Cline²,

Bernauer³

et al. 2021

Preprint

Self Cite

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Tests of a prototype lead tungstate calorimeter were made over two weeks at the end of September, 2019, at the DESY II Test Beam Facility in Hamburg, Germany. The purpose of these tests was to gain experience with the construction, operation, and performance of a simple lead tungstate calorimeter, and also to compare a traditional triggered readout scheme with a streaming readout approach. These tests are important for the proposed Two-Photon Exchange experiment at the DESY test beam facility and for work towards a future electromagnetic calorimeter that could be used in an Electron-Ion Collider detector. Details on all aspects of the test, the subsequent analysis, and the results are presented.

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Measurement of the Charge-Averaged Elastic Lepton-Proton Scattering Cross Section by the OLYMPUS Experiment

Cited by 10 publications

References 38 publications

Charged-averaged elastic lepton-proton scattering cross section results from OLYMPUS

Charged-averaged elastic lepton-proton scattering cross section results from OLYMPUS

Charge-averaged elastic lepton-proton scattering cross section results from OLYMPUS

Test of streaming and triggered readout schemes for the TPEX Lead Tungstate Calorimeter

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