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Recent results from COMPASS on the GPD program
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| Zeitschriftentitel: | EPJ Web of Conferences |
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| Personen und Körperschaften: | |
| In: | EPJ Web of Conferences, 192, 2018, S. 00012 |
| Format: | E-Article |
| Sprache: | Unbestimmt |
| veröffentlicht: |
EDP Sciences
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| Schlagwörter: |
| Zusammenfassung: | <jats:p>The dedicated COMPASS GPD program started in 2012 with a short pilot ’DVCS run’ and the first results from this run on DVCS, exclusive <jats:italic>π</jats:italic><jats:sup>0</jats:sup> and exclusive <jats:italic>ω</jats:italic> channels have been obtained. From the sum of cross sections measured with positive and negative beam polarities the DVCS cross-section and its dependence on the squared four-momentum transfer <jats:italic>t</jats:italic> have been extracted. It allowed a first estimate of the transverse size of the partonic distribution of the nucleon √〈r<jats:sup>2</jats:sup>⊥〉 i in a range of intermediate <jats:italic><jats:sup>x</jats:sup>B<jats:sub>j</jats:sub></jats:italic> with a mean <jats:italic><jats:sup>x</jats:sup>B<jats:sub>j</jats:sub></jats:italic> value of 0.056. We report also on the absolute value of the cross section for exclusive <jats:italic>π</jats:italic><jats:sup>0</jats:sup> production and its dependence on <jats:italic>t</jats:italic> and azimuthal angle <jats:italic>ϕ</jats:italic> between the scattering plane and <jats:italic>π</jats:italic><jats:sup>0</jats:sup> production plane. These measurements are aiming to constrain the GPDs, in particular chiral-odd (transversity) GPDs. Further, we present results on the spin density matrix elements for exclusive <jats:italic>ω</jats:italic> meson production and discuss the contributions from unnaturaly parity exchanges and from transitions that do not conserve helicity.</jats:p> |
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| Umfang: | 00012 |
| ISSN: |
2100-014X
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| DOI: | 10.1051/epjconf/201819200012 |