English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Measurements of the proton's form factor ratio made with polarizationtransfer show a striking discrepancy relative to the ratio extracted fromunpolarized elastic electron-proton scattering cross sections. One hypothesisis that the discrepancy is caused by hard two-photon exchange (TPE), atypically neglected radiative correction that may bias the two approachesdifferently. This hypothesis has been challenging to confirm. Theoreticalestimates of TPE are model-dependent, and recent experimental determinations ofTPE lacked the kinematic reach to be conclusive. The possible impact of TPEremains a cloud over our knowledge of the proton's form factors. Recently, theOLYMPUS experiment published new elastic scattering cross sections that areinsensitive to the effects of TPE: specifically the average of electron-protonand positron-proton cross sections. The OLYMPUS experiment, conducted at DESY,Hamburg, measured elastic $e^-p$ and $e^+p$ scattering by detecting thescattered 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 overdetermined kinematics of the reaction, the absolute efficiency of spectrometercould be verified, allowing cross sections to be extracted from the data. Theseresults can help refine our knowledge of the proton's form factors, especiallyin the squared momentum-transfer region of 1--2 GeV$^2$, where some previousmeasurements are in tension.

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