Measurement of inclusive ( D s ±) photoproduction at HERA

Physics Letters B, 1997

Inclusive photoproduction of D * ± in ep collisions at HERA has been measured with the ZEUS detector for photon-proton centre of mass energies in the range 115 < W < 280 GeV and photon virtuality Q 2 < 4 GeV 2 . The cross section σ ep → D * X integrated over the kinematic region p D * ⊥ > 3 GeV and −1.5 < η D * < 1.0 is (10.6 ± 1.7(stat.) ± 1.6 1.3 (syst.)) nb. Differential cross sections as functions of p D * ⊥ , η D * and W are given. The data are compared with two next-to-leading order perturbative QCD predictions. For a calculation using a massive charm scheme the predicted cross sections are smaller than the measured ones. A recent calculation using a massless charm scheme is in agreement with the data.

Physics Letters B, 1999

We estimate the cross section for γp → Υp by two independent methods. First, by studying the corrections to the naive leading-order QCD formula and, second, by using parton-hadron duality. The estimates are in good agreement with each other and with the recent measurements of the cross section at HERA.

The European Physical Journal C, 2012

The inclusive photoproduction of D * mesons and of D * -tagged dijets is investigated with the H1 detector at the ep collider HERA. The kinematic region covers small photon virtualities Q 2 < 2 GeV 2 and photon-proton centreof-mass energies of 100 < W γp < 285 GeV. Inclusive D * meson differential cross sections are measured for central rapidities |η(D * )| < 1.5 and transverse momenta p T (D * ) > 1.8 GeV. The heavy quark production process is further ina

Nuclear Physics B, 2005

Inclusive jet cross sections in photoproduction for events containing a D * meson have been measured with the ZEUS detector at HERA using an integrated luminosity of 78.6 pb −1 . The events were required to have a virtuality of the incoming photon, Q 2 , of less than 1 GeV 2 , and a photon-proton centre-ofmass energy in the range 130 < W γp < 280 GeV. The measurements are compared with next-to-leadingorder (NLO) QCD calculations. Good agreement is found with the NLO calculations over most of the measured kinematic region. Requiring a second jet in the event allowed a more detailed comparison with QCD calculations. The measured dijet cross sections are also compared to Monte Carlo (MC) models which incorporate leading-order matrix elements followed by parton showers and hadronisation. The NLO QCD predictions are in general agreement with the data although differences have been isolated to regions where contributions from higher orders are expected to be significant. The MC models give a better description than the NLO predictions of the shape of the measured cross sections.

The European Physical Journal C, 2007

Differential photoproduction cross sections are measured for events containing D * ± mesons. The data were taken with the H1 detector at the ep collider HERA and correspond to an integrated luminosity of 51.1 pb −1 . The kinematic region covers small photon virtualities Q 2 < 0.01 GeV 2 and photon-proton centre-of-mass energies of 171 < W γ p < 256 GeV. The details of the heavy quark production process are further investigated in events with one or two jets in addition to the D * ± meson. Differential cross sections for D * +jet production are determined and the correlations between the D * ± meson and the jet(s) are studied. The results are compared with perturbative QCD predictions applying collinear-or k t -factorisation.

Physics Letters B, 1995

We report the first observation of charmed mesons with the ZEUS detector at HERA using the decay channel D*+ --f (Do -+ K-n't)rr+ (f cc.). Clear signals in the mass difference AM=M(D*)-M(D') as well as in the M(Kv) distribution at the Do mass are found. The ep cross section for inclusive D** production with Q* < 4 GeV* in the yp centre-of-mass energy range 115 < W < 275 GeV has been determined to be (32&7$) nb in the kinematic region {p~( D' ) 2 1.7 GeV, Jv( D*) 1 < 1 S}. Extrapolating outside this region, assuming a mass of the charm quark of 1.5 GeV, we estimate the ep charm cross section to be a(ep -+ cEX) = (0.45 f O.ll?b$_,) pub at 4 = 296 GeV and (W) = 198 GeV. The average yp charm cross section (~(yp -+ cEX) is found to be (6.3 f 2.2:t.i) pub at (W) = 163 GeV and ( 16.9 f 5.2$y5') ,ub at (W) = 243 GeV. The increase of the total charm photoproduction cross section by one order of magnitude with respect to low energy data experiments is well described by QCD NLO calculations using singular gluon distributions in the proton.

Physics Letters B, 1994