Transverse extension of partons in the proton probed in the sea-quark range by measuring the DVCS cross section

The COMPASS Collaboration

Research output: Contribution to journalArticle


We report on the first measurement of exclusive single-photon muoproduction on the proton by COMPASS using 160 GeV/c polarised μ+ and μ beams of the CERN SPS impinging on a liquid hydrogen target. We determine the dependence of the average of the measured μ+ and μ cross sections for deeply virtual Compton scattering on the squared four-momentum transfer t from the initial to the final proton. The slope B of the t-dependence is fitted with a single exponential function, which yields B=(4.3±0.6stat|sys−0.3+0.1)(GeV/c)−2. This result can be converted into a transverse extension of partons in the proton, 〈r 2〉=(0.58±0.04stat|sys−0.02+0.01±0.04model)fm. For this measurement, the average virtuality of the photon mediating the interaction is 〈Q2〉=1.8(GeV/c)2 and the average value of the Bjorken variable is 〈xBj〉=0.056.

Original languageEnglish (US)
Pages (from-to)188-194
Number of pages7
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
StatePublished - Jun 10 2019



  • Deep inelastic scattering
  • Deeply virtual Compton scattering
  • Exclusive reactions
  • Generalized Parton Distributions
  • Proton size
  • Quantum chromodynamics

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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