Author/Authors :
Q2) Original Research Article
Pages 471-502
H1 Collaboration، نويسنده , , S. Aid، نويسنده , , A. V. Andreev، نويسنده , , B. Andrieu، نويسنده , , R.-D. Appuhn، نويسنده , , M. Arpagaus، نويسنده , , A. Babaev and NRMI Investigators، نويسنده , , Matthias J. Bahr، نويسنده , , J. B?n، نويسنده , , Y. Ban، نويسنده , , P. Baranov، نويسنده , , E. Barrelet، نويسنده , , R. Barschke، نويسنده , , W. Bartel، نويسنده , , Joan M. Barth، نويسنده , , U. Bassler، نويسنده , , H.P. Beck، نويسنده , , H.-J. Behrend، نويسنده , , V. A. Belousov، نويسنده , , Ch. Berger، نويسنده , , et al.، نويسنده ,
Abstract :
At the electron-proton collider HERA the inclusive D∗± meson photoproduction cross section has been measured with the H1 detector in two different, but partly overlapping, kinematical regions. For the first, where 〈Wγp〉 ≈ 200 GeV and Q2 < 0.01 GeV2, the result is σ(γp → ccX) = (13.2 ± 2.2−1.7 −4.8+2.1 +9.9) μb. The second measurement for Q2 < 4 GeV2 yields σ(γp → ccX) = (9.3 ± 2.1−1.8 −3.2+1.9 +6.9) μb at 〈Wγp〉 ≈ 142 GeV and σ(γp → ccX) = (20.6 ± 5.5−3.9 −7.2+4.3 +15.4 μb at 〈Wγp〉 ≈ 230 GeV, respectively. The third error accounts for an additional uncertainty due to the proton and photon parton density parametrizations. Differential cross sections are presented as a function of the D∗± transverse momentum and rapidity. The results compare reasonably well with next-to-leading order QCD calculations. Evidence for diffractive photoproduction of charm quarks is presented.
