Transverse Extension of Partons in the Proton probed by Deeply Virtual Compton Scattering

• Published in: arXiv.org 2019-12
• Main Authors: Amoroso, A, Andrieux, V, Anfimov, N V, Antoshkin, A, Austregesilo, A, Badelek, B, Ball, M, Bedfer, Y, Bicker, K, Bielert, E R, Bodlak, M, Bordalo, P, Buechele, M, Burtin, E, W -C Chang, Chatterjee, C, Chiosso, M, Cicuttin, A, Crespo, M L, Dhara, L, Donskov, S V, Doshita, N, Dusaev, R R, Dziewiecki, M, Eversheim, P D, Faessler, M, Finger, M, N du Fresne von Hohenesche, Frolov, V, Gerassimov, S, Giarra, J, Gnesi, I, Grasso, A, Gridin, A, Herrmann, F, C -Y Hsieh, Ishimoto, S, Ivanov, A, Jary, V, Juraskova, K, Khokhlov, Yu A, Klein, F, Kolosov, V N, Konorov, I, Kraemer, M, Kurjata, R P, Lednev, A A, Levchenko, E A, Levillain, M, Levorato, S, Y -S Lian, Longo, R, Lyubovitskij, V E, Magnon, A, Makins, N, Marianski, B, Marzec, J, Matousek, J, Matsuda, H, Matsuda, T, Meyer, M, Mikhailov, Yu V, Mitrofanov, N, Miyachi, Y, W -D Nowak, Nukazuka, G, Olshevsky, A G, Orlov, I, Ostrick, M, Panzieri, D, Paul, S, J -C Peng, Pesek, M, Pretz, J, Quaresma, M, Rybnikov, A, Rychter, A, Salac, R, Santos, C, Sarkar, S, Savin, I A, Sbrizzai, G, Schmieden, H, Sirtl, S, Smolik, J, Srnka, A, Steffen, D, Stolarski, M, Subrt, O, Sulc, M, Tessaro, S, Tosello, F, Uhl, S, Veloso, J, Vidon, A, Virius, M, Wilfert, M, Zaremba, K, Zavertyaev, M
• Format: Article
• Language: English
• Subjects: CERN; Dependence; Elastic scattering; Exponential functions; Liquid hydrogen; Momentum transfer; Partons; Protons; Synchrotrons
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1802.02739

We report on the first measurement of exclusive single-photon muoproduction on the proton by COMPASS using 160 GeV/\(c\) polarized \(\mu^+\) and \(\mu^-\) beams of the CERN SPS impinging on a liquid hydrogen target. We determine the dependence of the average of the measured \(\mu^+\) and \(\mu^-\) cross sections for deeply virtual Compton scattering on the squared four-momentum transfer \(t\) from the initial to the final final proton. The slope \(B\) of the \(t\)-dependence is fitted with a single exponential function, which yields \(B=(4.3 \ \pm \ 0.6_{\text{stat}}\_{- \ 0.3}^{+ \ 0.1}\big\rvert_{\text{sys}}) (\text{GeV}/c)^{-2}\). This result can be converted into an average transverse extension of partons in the proton, \(\sqrt{\langle r_{\perp}^2 \rangle} = (0.58 \ \pm \ 0.04_{\text{stat}}\_{- \ 0.02}^{+ \ 0.01}\big\rvert_{\text{sys}})\text{fm}\). For this measurement, the average virtuality of the photon mediating the interaction is \(\langle Q^2 \rangle = 1.8\,(\text{GeV/}c)^2\) and the average value of the Bjorken variable is \(\langle x_{\text{Bj}} \rangle = 0.056\).