The high mass μ + μ − pairs produced by 280 GeV μ + on a carbon target are studied in a search for the Y production. The high mass continuum in the region 2–18 GeV is interpreted in terms of QED pair production and of μ pairs originating from the decay of hidden and open charm particles as well as of hadrons ( π , K) from deep inelastic interactions. The upper limit for the upsilon production by muons is found to be, at the 90% confidence level, σ γ ·(γ→μ + μ − )<13·10 −39 cm 2 /nucleon.
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Mean values and differential distributions of event-shape variables have been studied in neutral current deep inelastic scattering using an integrated {luminosity} of 82.2 pb$^{-1}$ collected with the ZEUS detector at HERA. The kinematic range was $80 < Q^2 < 20 480\gev^2$ and $0.0024 < x < 0.6$, where $Q^2$ is the virtuality of the exchanged boson and $x$ is the Bjorken variable. The data are compared with a model based on a combination of next-to-leading-order QCD calculations with next-to-leading-logarithm corrections and the Dokshitzer-Webber non-perturbative power corrections. The power-correction method provides a reasonable description of the data for all event-shape variables studied. Nevertheless, the lack of consistency of the determination of $\alpha_s$ and of the non-perturbative parameter of the model, $\albar$, suggests the importance of higher-order processes that are not yet included in the model.
Mean value of the event shape variable 1-THRUST(C=T).
Mean value of the event shape variable B(C=T).
Mean value of the event shape variable RHO**2.
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