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Elastic photoproduction of J/psi and Upsilon mesons at HERA.

The H1 collaboration Adloff, C. ; Andreev, V. ; Andrieu, B. ; et al.

Phys.Lett.B 483 (2000) 23-35, 2000.

Inspire Record 525022 DOI 10.17182/hepdata.46894

Cross sections for elastic photoproduction of J/Psi and Upsilon mesons are presented. For J/Psi mesons the dependence on the photon-proton centre-of-mass energy W_gammap is analysed in an extended range with respect to previous measurements of 26<=W_gammap<= 285 GeV. The measured energy dependence is parameterized as sigma_gammap proportional W_gammap^delta with delta=0.83+-0.07. The differential cross section dsigma/dt for J/Psi mesons is derived, its dependence on W_gammap and on t is analysed and the effective trajectory (in terms of Regge theory) is determined to be alpha(t)=(1.27+-0.05)+(0.08+-0.17)*t/GeV^2. Models based on perturbative QCD and on pomeron exchange are compared to the data.

5 data tables

Table 1

The cross sections for the elastic photoproduction of J/PSI particles.

Table 2

Differential cross section, DSIG/DT, for the elastic photoproduction of J/PSI particles.

Table 3

The slope of the DSIG/DT distribution.

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Elastic Electroproduction of $\rh0$ and $J/\Psi$ Mesons at large $Q~2$ at HERA

The H1 collaboration Aid, S. ; Andreev, V. ; Andrieu, B. ; et al.

Nucl.Phys.B 468 (1996) 3-36, 1996.

Inspire Record 416228 DOI 10.17182/hepdata.51967

The total cross sections for the elastic electroproduction of $\rh0$ and $J/\Psi$ mesons for $Q~2$ $>$ 8 GeV$~2$ and $\langle W \rangle \simeq 90$ GeV/c$~2$ are measured at HERA with the H1 detector. The measurements are for an integrated electron$-$proton luminosity of $\simeq$3pb$~{-1}$. The dependences of the total virtual photon$-$proton ($\gamma~* p$) cross sections on $Q~2$, $W$ and the momentum transfer squared to the proton ($t$), and, for the $\rho$, the dependence on the polar decay angle ($\cos \theta~*$), are presented. The $J/\Psi$ : $\rh0$ cross section ratio is determined. The results are discussed in the light of theoretical models and of the interplay of hard and soft physics processes.

20 data tables

Table 1

Overall EP cross section for M(PI+PI-) < 1.5 GEV.

Table 2

Overall EP cross section, taking into account the J/PSI --> LEPTON+ LEPTON - branching fraction 0.12.

Table 3

Integrated EP cross section.

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Elastic Photoproduction of $\rho~{0}$ Mesons at HERA

The H1 collaboration Aid, S. ; Andreev, V. ; Andrieu, B. ; et al.

Nucl.Phys.B 463 (1996) 3-32, 1996.

Inspire Record 415281 DOI 10.17182/hepdata.44784

The cross section for the elastic photoproduction of \r0\ mesons ($\gamma p \rightarrow \rho~0 p$) has been measured with the H1 detector at HERA for two average photon-proton centre-of-mass energies of 55 and 187GeV. TheFcenterline lower energy point was measured by observing directly the $\rho~{0}$ decay giving a cross section of $9.1\pm 0.9\,(\stat)\pm 2.5\,(\syst)\;\mu$b. The logarithmic slope parameter of the differential cross section, ${\rm d}\sigma/{\rm d}t$, is found to be $10.9 \pm 2.4\,(\stat) \pm 1.1\,(\syst)\;$GeV$~{-2}$. The \r0\ decay polar angular distribution is found to be consistent with s-channel helicity conservation. The higher energy cross section was determined from analysis of the lower part of the hadronic invariant mass spectrum of diffractive photoproduction and found to be $13.6\pm 0.8\,(\stat)\pm 2.4\,(\syst)\;\mu$b.

6 data tables

Table 1

PI+ PI- cross section.

Table 2

RHO0 cross section by selecting Mpipi to lie between 2Mpi and Mrho + 5width0.

Table 3

No description provided.