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

Multi Point Water Quenched Prove for Spatially Averaged Hot Gas Sampling in Industrial Combustors

Paper from the AFRC 2015 conference titled Multi Point Water Quenched Prove for Spatially Averaged Hot Gas Sampling in Industrial CombustorsExtracting gas samples through intrusive probes remains the most common and simple means of gas com-; position analysis. After extraction, the probe delivers the gas sample to an online or oine gas analysis; unit; these devices operate on many dierent principles but ultimately measure the composition of the gas; at the sampling unit. This procedure works well when the measured species are homogeneous in space and; when the gas temperature is low enough to freeze any chemical reactions prior to extraction. In industrial; combustors, these conditions are typically only met when the sample is taken from the exhaust stream;; where heat exchangers and other devices mix the gas and remove heat prior to sampling. When these; conditions are not met, such as when sampling from an industrial heater or gas turbine transition piece,; special design considerations are needed to ensure reliability in the measurement. In particular, the probe; must be able to quench reactions in situ to avoid subsequent oxidation and spatially average the sample.; This paper describes the design procedure for a new multi point gas sampling probe that incorporates these; considerations. A chemical kinetics analysis was performed to nd the required cooling rate to quench the; chemical reactions. With the required quenching rate known, a one-dimensional single-point probe was; designed using a heat transfer model that delivered the required cooling rate. Next, a series of these single; point probes were combined in a sample rake designed to spatially average the gas sample. The rake's; quenching rate was validated with a two-dimensional heat transfer model using ANSYS. The new multi; point probe is shown to have sucient spatial averaging and quenching rate characteristics suggesting that; it is an appropriate design for species measurement within typical industrial combustors

Particle Production and Fragmentation.

Recent results from HERA are presented on a range of topics: charged multiplicities, production of non-strange mesons and strange particles, charm fragmentation, baryons decaying to strange particles, antideuteron production, Bose-Einstein correlations, and new interpretations of results on prompt photon production in DIS.Comment: latex, 10 pages, 6 fig