D* Production in Deep Inelastic Scattering at HERA

This paper presents measurements of D^{*\pm} production in deep inelastic scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The data have been taken with the ZEUS detector at HERA. The decay channel $D^{*+}\to (D^0 \to K^- \pi^+) \pi^+$ (+ c.c.) has been used in the study. The $e^+p$ cross section for inclusive D^{*\pm} production with $5<Q^2<100 GeV^2$ and $y<0.7$ is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region {$1.3<p_T(D^{*\pm})<9.0$ GeV and $| \eta(D^{*\pm}) |<1.5$}. Differential cross sections as functions of p_T(D^{*\pm}), $\eta(D^{*\pm}), W$ and $Q^2$ are compared with next-to-leading order QCD calculations based on the photon-gluon fusion production mechanism. After an extrapolation of the cross section to the full kinematic region in p_T(D^{*\pm}) and $\eta$(D^{*\pm}), the charm contribution $F_2^{c\bar{c}}(x,Q^2)$ to the proton structure function is determined for Bjorken $x$ between 2 $\cdot$ 10$^{-4}$ and 5 $\cdot$ 10$^{-3}$.Comment: 17 pages including 4 figure

Observation of Scaling Violations in Scaled Momentum Distributions at HERA

Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of $x$ and $Q^2$ using the ZEUS detector. The evolution of the scaled momentum, $x_p$, with $Q^2,$ in the range 10 to 1280 $GeV^2$, has been investigated in the current fragmentation region of the Breit frame. The results show clear evidence, in a single experiment, for scaling violations in scaled momenta as a function of $Q^2$.Comment: 21 pages including 4 figures, to be published in Physics Letters B. Two references adde

Observation of hard scattering in photoproduction events with a large rapidity gap at HERA

Events with a large rapidity gap and total transverse energy greater than 5 GeV have been observed in quasi-real photoproduction at HERA with the ZEUS detector. The distribution of these events as a function of the $\gamma p$ centre of mass energy is consistent with diffractive scattering. For total transverse energies above 12 GeV, the hadronic final states show predominantly a two-jet structure with each jet having a transverse energy greater than 4 GeV. For the two-jet events, little energy flow is found outside the jets. This observation is consistent with the hard scattering of a quasi-real photon with a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil

Observation of Events with an Energetic Forward Neutron in Deep Inelastic Scattering at HERA

In deep inelastic neutral current scattering of positrons and protons at the center of mass energy of 300 GeV, we observe, with the ZEUS detector, events with a high energy neutron produced at very small scattering angles with respect to the proton direction. The events constitute a fixed fraction of the deep inelastic, neutral current event sample independent of Bjorken x and Q2 in the range 3 · 10-4 \u3c xBJ \u3c 6 · 10-3 and 10 \u3c Q2 \u3c 100 GeV2

Extraction and characterisation of interstitial pore-waters from Ruprechtov

This report describes work carried out by the British Geological Survey as part of a contract (Ref GA/02F/107) with Gesellscahft für Anlagen und Reaktorsicherheit (GRS) to carry out the practical extraction and characterisation of interstitial clay pore-waters from the Ruprechtov site. The contract is a continuation of earlier work carried out by the BGS in 1999/2000 (Reeder et al. 2000) Seven samples were tested for pore-water extraction by mechanical squeezing. These were tested in two phases: the first three in December 2002, and the second four in the Spring of 2004. The report describes the methods used to carry out these tests and summarises all the data produced

Geochemical interactions between supercritical CO2 and the Midale Formation. V : experiments investigating reactions of the Midale Vuggy

This report describes work undertaken at the British Geological Survey (BGS) that forms part of the international IEA Weyburn Carbon Dioxide (CO2) Monitoring and Storage Project. This project aims to monitor and predict the behaviour of injected CO2 into the Midale reservoir at the Weyburn oil field in southern Saskatchewan, Canada, using methods that include; time-lapse geophysics, modelling its subsurface distribution and migration, and simulating likely chemical interactions with the host rock. This report aims to provide a description of fluid chemical and mineralogical changes occurring in a series of experiments that have been conducted within the Hydrothermal Laboratory of the British Geological Survey. These experiments were undertaken to identify what geochemical changes would result from the injection of CO2 into the Midale Vuggy formation. The experiments utilised samples of Midale Vuggy core material from the Weyburn field, synthetic formation water based upon measured well fluid compositions, and either CO2 or N2 as a pressurising medium. The experiments were conducted at 60°C and pressurised to either 150 bar [15 MPa] or 250 bar [25 MPa], using either CO2 or N2. Experiment durations ranged from one week to 6 months. The evolution over time of a selection of solutes was followed. Relative to the N2 ‘baseline’ experiments, it was found that the impact of CO2 was to: - increase the concentrations of Ca, Si and HCO3 - - decrease the concentrations of total S and possibly Sr, and pH values - have little impact on the concentrations of Mg, Mn and Al It is noted that these fluid chemical changes are not dissimilar to those found in the Midale Marly experiments (Rochelle et al., 2003a) All monoliths reacted in CO2-rich synthetic pore waters showed clear evidence of ‘tidemarks’ on their external surfaces, with the area below the water-CO2 interface appearing bleached. After 4 weeks of reaction of the monoliths with CO2, euhedral prismatic gypsum crystals up to 500 µm in length formed below the water line in the CO2 experiment. By 8 weeks reaction the gypsum crystals were at least 2.5 mm long, and at 17 weeks reaction gypsum crystals up to 500 µm long also developed in the baseline N2 experiment. In addition, most calcite and anhydrite surfaces below the water line were corroded to a depth of 10-30 µm in both the CO2 and the baseline N2 experiments. This porosity was easily distinguishable from the vuggy porosity developed during diagenesis. Scanning electron microscopy also revealed that a fine coating of halite developed above the water-CO2 interface during the experiment. In the experiments containing crushed Midale Vuggy, euhedral tabular prismatic gypsum crystals up to 1.8 mm long developed after 2 weeks reaction. Only limited evidence for minor corrosion was tentatively observed. After 26 weeks of reaction, the only evidence for dissolution in the <250 µm crushed samples was slightly less ‘dust’ in the baseline N2 experiment relative to the CO2 experiment. It was noted that the CO2 experiments give lower S concentrations compared to the N2 experiments, with S (as SO4) removed from solution by gypsum precipitation. During the early parts of the experiments at least, this appears to be faster than the rate of SO4 addition from anhydrite dissolution. Later in the CO2 experiments steady-state concentrations appear to be reached, and it is likely that saturation with respect to gypsum balances lower S concentrations with higher Ca concentrations. The changes described above were interpreted as being due to some calcite dissolution (probably more than observed in the Midale Marly experiments), some anhydrite dissolution, a little aluminosilicate mineral dissolution and a fair amount of gypsum precipitation. It is still unclear if there is an overall net increase or decrease in porosity or permeability. However, if significant gypsum precipitation reduced the permeability of the Midale Vuggy unit, then this may be a beneficial reaction in terms of the EOR operation, as it might reduce the potential for the injected CO2 to ‘under-ride’ the target Marly unit