HEPData Search

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Measurements of inelastic J/psi and psi' photoproduction at HERA.

The ZEUS collaboration Chekanov, S. ; Krakauer, D. ; Magill, S. ; et al.

Eur.Phys.J.C 27 (2003) 173-188, 2003.

Inspire Record 601166 DOI 10.17182/hepdata.46546

The cross sections for inelastic photoproduction of J/psi and psi' mesons have been measured in ep collisions with the ZEUS detector at HERA, using an integrated luminosity of 38.0 pb-1. The events were required to have 0.1 < z < 0.9 and 50 < W < 180 GeV, where z is the fraction of the incident photon energy carried by the J/psi in the proton rest frame and W is the photon-proton centre-of-mass energy. The psi' to J/psi cross-section ratio was measured in the range 0.55 < z < 0.9. The J/psi data, for various ranges of transverse momentum, are compared to theoretical models incorporating colour-singlet and colour-octet matrix elements. Predictions of a next-to-leading-order colour-singlet model give a good description of the data, although there is a large normalisation uncertainty. The J/psi helicity distribution for z > 0.4 is compared to leading-order QCD predictions.

10 data tables

Table 1

Measurment of the total cross section, with various PT thresholds, in the high Z > 0.9 region.

Table 2

Ratio of cross section for PSI(2S) to J/PSI production. as a function of PT. Statistical errors only.

Table 3

Ratio of cross section for PSI(2S) to J/PSI production. as a function of W. Statistical errors only.

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Measurement of elastic J / psi photoproduction at HERA

The ZEUS collaboration Breitweg, J. ; Derrick, M. ; Krakauer, D. ; et al.

Z.Phys.C 75 (1997) 215-228, 1997.

Inspire Record 442537 DOI 10.17182/hepdata.44626

The reaction gamma p -> J/Psi p has been studied in ep interactions using the ZEUS detector at HERA. The cross section for elastic J/Psi photoproduction has been measured as a function of the photon-proton centre of mass energy W in the range 40 < W < 140 GeV at a median photon virtuality Q^2 of 5*10^{-5} GeV^2. The photoproduction cross section, sigma_{gamma p -> J/Psi p}, is observed to rise steeply with W. A fit to the data presented in this paper to determine the parameter $\delta$ in the form sigma_{gamma p -> J/Psi p} \propto W^{\delta} yields the value \delta = 0.92 \pm 0.14 \pm 0.10. The differential cross section dsigma/d|t| is presented over the range |t| < 1.0 GeV^2 where t is the square of the four-momentum exchanged at the proton vertex. d\sigma/d|t| falls exponentially with a slope parameter of 4.6 \pm 0.4 (+0.4-0.6) GeV^{-2}. The measured decay angular distributions are consistent with s-channel helicity conservation.

9 data tables

Table 1

Data from the electron channel. Second systematic error is that attributed to the uncertainty in the modelof proton dissociation used for background subtraction.

Table 2

Data from the muon channel. Second systematic error is that attributed to the uncertainty in the modelof proton dissociation used for background subtraction.

Table 3

Data from the electron channel. Second systematic error is that attributed to the uncertainty in the modelof proton dissociation used for background subtraction.

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Rescattering probed by the emission of slow target associated particles in high-energy heavy ion interactions

The EMU01 collaboration Adamovich, M.I ; Aggarwal, M.M ; Alexandrov, Y.A ; et al.

Phys.Lett.B 363 (1995) 230-236, 1995.

Inspire Record 406952 DOI 10.17182/hepdata.28438

In this letter the distribution of slow target associated particles emitted in Au + Emulsion interactions at 11.6 A GeV/ c is studied. The three models RQMD, FRITIOF and VENUS are used for comparisons and especially their treatment of rescattering is investigated.

6 data tables

Table 1

No description provided.

Table 2

PROJECTILE ASSOCIATED HE-FRAGMENTS.

Table 3

No description provided.