Low Q^2 Jet Production at HERA and Virtual Photon Structure

The transition between photoproduction and deep-inelastic scattering is investigated in jet production at the HERA ep collider, using data collected by the H1 experiment. Measurements of the differential inclusive jet cross-sections dsigep/dEt* and dsigmep/deta*, where Et* and eta* are the transverse energy and the pseudorapidity of the jets in the virtual photon-proton centre of mass frame, are presented for 0 < Q2 < 49 GeV2 and 0.3 < y < 0.6. The interpretation of the results in terms of the structure of the virtual photon is discussed. The data are best described by QCD calculations which include a partonic structure of the virtual photon that evolves with Q2.Comment: 20 pages, 5 Figure

Hadron Production in Diffractive Deep-Inelastic Scattering

Characteristics of hadron production in diffractive deep-inelastic positron-proton scattering are studied using data collected in 1994 by the H1 experiment at HERA. The following distributions are measured in the centre-of-mass frame of the photon dissociation system: the hadronic energy flow, the Feynman-x (x_F) variable for charged particles, the squared transverse momentum of charged particles (p_T^{*2}), and the mean p_T^{*2} as a function of x_F. These distributions are compared with results in the gamma^* p centre-of-mass frame from inclusive deep-inelastic scattering in the fixed-target experiment EMC, and also with the predictions of several Monte Carlo calculations. The data are consistent with a picture in which the partonic structure of the diffractive exchange is dominated at low Q^2 by hard gluons.Comment: 16 pages, 6 figures, submitted to Phys. Lett.

Measurement of D* Meson Cross Sections at HERA and Determination of the Gluon Density in the Proton using NLO QCD

With the H1 detector at the ep collider HERA, D* meson production cross sections have been measured in deep inelastic scattering with four-momentum transfers Q^2>2 GeV2 and in photoproduction at energies around W(gamma p)~ 88 GeV and 194 GeV. Next-to-Leading Order QCD calculations are found to describe the differential cross sections within theoretical and experimental uncertainties. Using these calculations, the NLO gluon momentum distribution in the proton, x_g g(x_g), has been extracted in the momentum fraction range 7.5x10^{-4}< x_g <4x10^{-2} at average scales mu^2 =25 to 50 GeV2. The gluon momentum fraction x_g has been obtained from the measured kinematics of the scattered electron and the D* meson in the final state. The results compare well with the gluon distribution obtained from the analysis of scaling violations of the proton structure function F_2.Comment: 27 pages, 9 figures, 2 tables, submitted to Nucl. Phys.

Measurement of Leading Proton and Neutron Production in Deep Inelastic Scattering at HERA

Deep--inelastic scattering events with a leading baryon have been detected by the H1 experiment at HERA using a forward proton spectrometer and a forward neutron calorimeter. Semi--inclusive cross sections have been measured in the kinematic region 2 <= Q^2 <= 50 GeV^2, 6.10^-5 <= x <= 6.10^-3 and baryon p_T <= MeV, for events with a final state proton with energy 580 <= E' <= 740 GeV, or a neutron with energy E' >= 160 GeV. The measurements are used to test production models and factorization hypotheses. A Regge model of leading baryon production which consists of pion, pomeron and secondary reggeon exchanges gives an acceptable description of both semi-inclusive cross sections in the region 0.7 <= E'/E_p <= 0.9, where E_p is the proton beam energy. The leading neutron data are used to estimate for the first time the structure function of the pion at small Bjorken--x.Comment: 30 pages, 9 figures, 2 tables, submitted to Eur. Phys.

Charmonium Production in Deep Inelastic Scattering at HERA

The electroproduction of J/psi and psi(2S) mesons is studied in elastic, quasi-elastic and inclusive reactions for four momentum transfers 2 Q^2 80 GeV^2 and photon-proton centre of mass energies 25 W 180 GeV. The data were taken with the H1 detector at the electron proton collider HERA in the years 1995 to 1997. The total virtual photon-proton cross section for elastic J/psi production is measured as a function of Q^2 and W. The dependence of the production rates on the square of the momentum transfer from the proton (t) is extracted. Decay angular distributions are analysed and the ratio of the longitudinal and transverse cross sections is derived. The ratio of the cross sections for quasi-elastic psi(2S) and J/psi meson production is measured as a function of Q^2. The results are discussed in terms of theoretical models based upon perturbative QCD. Differential cross sections for inclusive and inelastic production of J/psi mesons are determined and predictions within two theoretical frameworks are compared with the data, the non-relativistic QCD factorization approach including colour octet and colour singlet contributions, and the model of Soft Colour Interactions

Classification of peanuts by wet chemical analysis, instrumental methods, electronic nose devices and sensory analysis

The peanut is the third most important oilseed crop in the world. Several species and types of wild and cultivated kinds of peanuts are known. Since they contain 50-55% oil and 25-28% protein, the potential for the development of an off-flavour during storage is significant (Ory et al., 1992; Bett et al, 1994). In routine analysis wer chemical methods are used for the determination of quality. These methods are always related to certain lipid parameters, for example the acid value is the amount of potassium hydroxide required to neutralise the fatty acids in 1g of fat, while the peroxide value is the quantity, which oxidises potassium under certain operating conditions. In addition, instrumental methods (e.g. gas chromatography) and sensory analysis are described as usable tools for the determination of the storage period, the quality and the origin. Apart from the time- consuming aspect of these methods, they are sensitive to misinterpretation. In the last ten years new devices, so called "electronic noses", have been described in the literature as a both cost-effective and timesaving substitute for these methods. Most of these chemical sensors showed deficiencies in selectivity, sensitivity und reproducibility (Haugen, 2001). The coupling of gas chromatography with an array of chemical sensors, the High Resolution Gas Chromatography-Selective Odorant Measurement by Multisensor Array (HRGC/SOMSA, Schieberle et al. 1997) represents the coupling of gas chromatography with an array of chemical sensors. This device has been used for the detection of odour-active compounds (Bücking and Steinhart, 2001). The aim of this paper is to compare these methods with regard to their utility for the classification of peanuts

Electrochemical synthesis of coaxial TiO2–Ag nanowires and their application in photocatalytic water splitting

A new method for the formation of coaxial TiO2–Ag nanowires is presented, in which TiO2 nanotubes were formed by the templated electrochemically induced sol–gel method, followed by thermal annealing. The as-formed TiO2 nanotubes have been successfully filled with a Ag core using a subsequent electrodeposition step. Coaxial nanowires have a very suitable architecture for photocatalysis, solar cells or batteries due to the high contact area between the two different phases, the large outer surface area exposed to the reactant, and short electron diffusion paths. The coaxial nanowires showed a higher efficiency than empty TiO2 nanotubes and TiO2 nanotubes with attached Ag nanoparticles in photocatalytic water splitting. Coaxial TiO2–Ag nanowires formed H2 at a rate of 1.23 × 10−3 ± 0.3 × 10−3 mol g−1 h−1 without deactivation for at least 6 h