Exclusive electroproduction of J/psi mesons at HERA.

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Krakauer, D. ; et al.
Nucl.Phys.B 695 (2004) 3-37, 2004.
Inspire Record 647777 DOI 10.17182/hepdata.46277

The exclusive electroproduction of J/psi mesons, ep->epJ/psi, has been studied with the ZEUS detector at HERA for virtualities of the exchanged photon in the ranges 0.15<Q^2<0.8 GeV^2 and 2<Q^2<100 GeV^2 using integrated luminosities of 69 pb^-1 and 83 pb^-1, respectively.The photon-proton centre-of-mass energy was in the range 30<W<220 GeV and the squared four-momentum transfer at the proton vertex |t|<1.The cross sections and decay angular distributions are presented as functions of Q^2, W and t. The effective parameters of the Pomeron trajectory are in agreement with those found in J/psi photoproduction. The spin-density matrix elements, calculated from the decay angular distributions, are consistent with the hypothesis of s-channel helicity conservation. The ratio of the longitudinal to transverse cross sections, sigma_L/sigma_T, grows with Q^2, whilst no dependence on W or t is observed. The results are in agreement with perturbative QCD calculations and exhibit a strong sensitivity to the gluon distribution in the proton.

20 data tables

Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 0.15 to 0.18 GeV**2.

Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 2 to 5 GeV**2.

Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 5 to 10 GeV**2.

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INVESTIGATION OF THE PROCESS E+ E- ---> E+ E- GAMMA IN THE ENERGY REGION 0.64-GEV - 1.40-GEV. (IN RUSSIAN)

Bukin, A.D. ; Kurdadze, L.M. ; Lelchuk, M.Yu. ; et al.
Yad.Fiz. 35 (1982) 1444-1447, 1982.
Inspire Record 182031 DOI 10.17182/hepdata.37152

None

3 data tables

No description provided.

No description provided.

No description provided.


Angular correlations in three-jet events in ep collisions at HERA

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.
Phys.Rev.D 85 (2012) 052008, 2012.
Inspire Record 793931 DOI 10.17182/hepdata.45283

Three-jet production in deep inelastic ep scattering and photoproduction was investigated with the ZEUS detector at HERA using an integrated luminosity of 127 pb-1. Measurements of differential cross sections are presented as functions of angular correlations between the three jets in the final state and the proton-beam direction. These correlations provide a stringent test of perturbative QCD and show sensitivity to the contributions from different colour configurations. Fixed-order perturbative QCD calculations assuming the values of the colour factors C_F, C_A and T_F as derived from a variety of gauge groups were compared to the measurements to study the underlying gauge group symmetry. The measured angular correlations in the deep inelastic ep scattering and photoproduction regimes are consistent with the admixture of colour configurations as predicted by SU(3) and disfavour other symmetry groups, such as SU(N) in the limit of large N.

9 data tables

Integrated 3-jet photoproduction cross section.

Integrated 3-jet cross sections in NC DIS.

Normalized differential 3-jet photoproduction cross section as a function of THETA(H).

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Study of the process e+e-\to \mu+\mu- in the energy region \sqrt{s}=980, 1040 -- 1380 MeV

Achasov, M.N. ; Aulchenko, V.M. ; Beloborodov, K.I. ; et al.
Phys.Rev.D 79 (2009) 112012, 2009.
Inspire Record 798415 DOI 10.17182/hepdata.50493

The cross section of the process e+e-\to\mu+\mu- was measured in the SND experiment at the VEPP-2M e+e- collider in the energy region \sqrt{s}=980, 1040 -- 1380 MeV. The event numbers of the process e+e-\to\mu+\mu- were normalized to the integrated luminosity measured using e+e-\to e+e- and e+e-\to\gamma\gamma processes. The ratio of the measured cross section to the theoretically predicted value is 1.006\pm 0.007 \pm 0.016 and 1.005 \pm 0.007 \pm 0.018 in the first and second case respectively. Using results of the measurements, the electromagnetic running coupling constant \alpha in the energy region \sqrt{s}=1040 -- 1380 MeV was obtained <1/\alpha> = 134.1\pm 0.5 \pm 1.2 and this is in agreement with theoretical expectation.

2 data tables

The E+ E- --> MU+ MU- cross section obtained using the (GAMMA GAMMA) luminosity measurement.

The measured E+ E- --> E+ E- cross section in the electron angle 30 to 150 degrees.


Measurement of D mesons production in deep inelastic scattering at HERA.

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.
JHEP 07 (2007) 074, 2007.
Inspire Record 749371 DOI 10.17182/hepdata.45530

Charm production in deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 82 pb^{-1}. Charm has been tagged by reconstructing D^{*+}, D^0, D^{+} and D_s^+ (+ c.c.) charm mesons. The charm hadrons were measured in the kinematic range p_T(D^{*+},D^0,D^{+}) > 3 GeV, p_T(D_s^+)>2 GeV and |\eta(D)| < 1.6 for 1.5 < Q^2 < 1000 GeV^2 and 0.02 < y < 0.7. The production cross sections were used to extract charm fragmentation ratios and the fraction of c quarks hadronising into a particular charm meson in the kinematic range considered. The cross sections were compared to the predictions of next-to-leading-order QCD, and extrapolated to the full kinematic region in p_T(D) and \eta(D) in order to determine the open-charm contribution, F_2^{c\bar{c}}(x,Q^2), to the proton structure function F_2.

24 data tables

Production cross section for all D0 mesons, those not originating fom D* decays and those originating from D* decays.

Production cross section for additional D* mesons (not decaying to D0) and all D* mesons.

Production cross section for D+ mesons.

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Leading neutron energy and p(T) distributions in deep inelastic scattering and photoproduction at HERA.

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.
Nucl.Phys.B 776 (2007) 1-37, 2007.
Inspire Record 744787 DOI 10.17182/hepdata.45630

The production of energetic neutrons in $ep$ collisions has been studied with the ZEUS detector at HERA. The neutron energy and $p_T^2$ distributions were measured with a forward neutron calorimeter and tracker in a $40 \pb^{-1}$ sample of inclusive deep inelastic scattering (DIS) data and a $6 \pb^{-1}$ sample of photoproduction data. The neutron yield in photoproduction is suppressed relative to DIS for the lower neutron energies and the neutrons have a steeper $p_T^2$ distribution, consistent with the expectation from absorption models. The distributions are compared to HERA measurements of leading protons. The neutron energy and transverse-momentum distributions in DIS are compared to Monte Carlo simulations and to the predictions of particle exchange models. Models of pion exchange incorporating absorption and additional secondary meson exchanges give a good description of the data.

35 data tables

Ratio of leading neutron to inclusive cross sections integrated to the full PT range.

Normalized double differential cross sections for leading neutron production for the full DIS sample. Statistical errors only are given.

Normalized double differential cross sections for leading neutron production for the full DIS sample. Statistical errors only are given.

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The Q**2 dependence of dijet cross sections in gamma p interactions at HERA.

The ZEUS collaboration Breitweg, J. ; Chekanov, S. ; Derrick, M. ; et al.
Phys.Lett.B 479 (2000) 37-52, 2000.
Inspire Record 523610 DOI 10.17182/hepdata.46968

The dependence of the photon structure on the photon virtuality, Q^2, is studied by measuring the reaction e^+p\to e^+ + {\rm jet} + {\rm jet} + {\rm X} at photon-proton centre-of-mass energies 134 < W < 223 GeV. Events have been selected in the Q^2 ranges \approx 0 GeV^2, 0.1-0.55 GeV^2, and 1.5-4.5 GeV^2, having two jets with transverse energy E_T^{jet} > 5.5 GeV in the final state. The dijet cross section has been measured as a function of the fractional momentum of the photon participating in the hard process, x_gamma. The ratio of the dijet cross section with x_gamma < 0.75 to that with x_gamma > 0.75 decreases as Q^2 increases. The data are compared with the predictions of NLO pQCD and leading-order Monte Carlo programs using various parton distribution functions of the photon. The measurements can be interpreted in terms of a resolved photon component that falls with Q^2 but remains present at values of Q^2 up to 4.5 GeV^2. However, none of the models considered gives a good description of the data.

4 data tables

Dijet cross section for the low ET set of cuts.

Dijet cross section for the high ET set of cuts.

Ratio of Dijet cross sections as a function of Q**2 for XOBS(C=GAMMA) less than to greater than 0.75 for the lower ET cuts.

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Measurement of K0(S), Lambda, anti-Lambda production at HERA

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.
Eur.Phys.J.C 51 (2007) 1-23, 2007.
Inspire Record 734144 DOI 10.17182/hepdata.45796

The production of the neutral strange hadrons $K^{0}_{S}$, $\Lambda$ and $\bar{\Lambda}$ has been measured in $ep$ collisions at HERA using the ZEUS detector. Cross sections, baryon-to-meson ratios, relative yields of strange and charged light hadrons, $\Lambda$ ($\bar{\Lambda}$) asymmetry and polarization have been measured in three kinematic regions: $Q^2 > 25 \gev^2$: $5 < Q^2 < 25 \gev^2$: and in photoproduction ($Q^2 \simeq 0$). In photoproduction the presence of two hadronic jets, each with at least $5 \gev$ transverse energy, was required. The measurements agree in general with Monte Carlo models and are consistent with measurements made at $e^+ e^-$ colliders, except for an enhancement of baryon relative to meson production in photoproduction.

59 data tables

Differential K0S cross section in DIS events as a function of transverse momentum (lab). for Q**2 from 5 to 25 GeV**2.

Differential K0S cross section in DIS events as a function of transverse momentum (lab). for Q**2 > 25 GeV**2.

Differential K0S cross section in DIS events as a function of pseudorapidity (lab). for Q**2 from 5 to 25 GeV**2.

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Measurement of neutral current cross sections at high Bjorken-x with the ZEUS detector at HERA.

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.
Eur.Phys.J.C 49 (2007) 523-544, 2007.
Inspire Record 723329 DOI 10.17182/hepdata.11718

A new method is employed to measure the neutral current cross section up to Bjorken-x values of one with the ZEUS detector at HERA using an integrated luminosity of 65.1 pb-1 for e+p collisions and 16.7 pb-1 for e-p collisions at sqrt{s}=318 GeV and 38.6 pb-1 for e+p collisions at sqrt{s}=300 GeV. Cross sections have been extracted for Q2 >= 648 GeV2 and are compared to predictions using different parton density functions. For the highest x bins, the data have a tendency to lie above the expectations using recent parton density function parametrizations.

114 data tables

The double differential cross section for the 96-97 E+ P NC scattering data.

The double differential cross section for the 96-97 E+ P NC scattering data.

The double differential cross section for the 96-97 E+ P NC scattering data.

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Study of the e+ e- --> eta gamma process with SND detector at the VEPP-2M e+ e- collider.

Achasov, M.N. ; Aulchenko, V.M. ; Beloborodov, K.I. ; et al.
Phys.Rev.D 74 (2006) 014016, 2006.
Inspire Record 717778 DOI 10.17182/hepdata.41804

In experiment with the SND detector at VEPP-2M $e^+e^-$ collider the $e^+e^-\to\eta\gamma$ cross section was measured in the energy range $E$=0.60--1.38 GeV with the integrated luminosity of 27.8 pb$^{-1}$. The measured cross section is well described by the vector meson dominance model with contributions from the $\rho(770)$, $\omega(783)$, $\phi(1020)$, $\rho^{\prime}(1465)$ resonances and agrees with results of previous measurements. The decay probabilities $\BR(\phi\to\eta\gamma)$, $\BR(\omega\to\eta\gamma)$ and $\BR(\rho\to\eta\gamma)$ were measured with the accuracies better than or comparable to the world averages.

2 data tables

Cross section from the ETA --> 3PI0 decay mode.

Cross section from the ETA --> PI+ PI- PI0 decay mode.