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 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

Variability of chemical and isotopic parameters of water from the Franciszek borehole in the Wysowa-Zdrój

Mixing of two water components and simultaneous contact with geogenic carbon dioxide are the characteristic features of waterfrom the Franciszek borehole in the Wysowa-Zdrój. During the last 45 years a systematic, slow decrease of water mineralization of this borehole has been observed. This may be due to several reasons: i) increased contribution of the infiltration component in the total inflow to the well, ii) gradual decrease of mineralization of diagenetic water or, iii) local changes of gaseous, geogenic carbon dioxide within the reservoir. Results of chemical and stable isotope measurements from the timespan of 42 years are discussed in the paper. The PHREEQC code was used in the analysis of chemical data and in the numerical simulation ofpossible processes leading to the observed changes in the water mineralization. Results of chemical calculations and stable isotope data are consistent and prove that decrease of water mineralization in the Franciszek borehole is caused by increased contribution of water of infiltration origin

Determination of groundwater age using environmental isotopes - methodological remarks

Groundwater age plays an important role in both development and management of groundwater resources. This is particularly true for groundwater systems being exploitedfor drinking water purposes and subject to anthropogenic stress. Environmental isotopes play a vital role in quantifying time scales of groundwater flow, ranging from fraction of a year to millions of years. Over the past several decades a large number of groundwater age indicators have been proposed. Apart of radioactive isotopes, also stable isotopes of water, isotopes of noble gases and anthropogenic trace substances present in the atmosphere have been usedfor this purpose. This work is focusing on methodological aspects of groundwater age determinations using tritium, radiocarbon and stable isotope composition of water. The discussion is based on a rich material available after several decades of application of environmental isotope techniques in groundwater studies in Poland

A search for excited fermions in e+p collisions at HERA

Using the ZEUS detector at HERA, we have searched for heavy excited states of electrons, neutrinos, and quarks in e+p collisions at a center-of-mass energy of 300 GeV. With an integrated luminosity of 9.4 pb-1, no evidence was found for electroweak production and decay of such states. Limits on the production cross section times branching ratio and on the characteristic couplings, f/Λ, are derived for masses up to 250 GeV. For the particular choice f/Λ = 1/Mf*, we exclude at the 95% confidence level excited electrons with mass between 30 and 200 GeV, excited electron neutrinos with mass between 40 and 96 GeV, and quarks excited electroweakly with mass between 40 and 169 GeV. © Springer-Verlag 1997

The ZEUS leading proton spectrometer and its use in the measurement of elastic ρ0 photoproduction at HERA

The differential cross section dσ/dt for elastic ρ0 photoproduction, γp → ρ0ρ (ρ0 → π+π-), has been measured in ep interactions at HERA. The squared four-momentum exchanged at the proton vertex, t, has been determined directly by measuring the momentum of the scattered proton using the ZEUS Leading Proton Spectrometer (LPS), a large scale system of silicon micro-strip detectors operating close to the HERA proton beam. The LPS allows the measurement of the momentum of high energy protons scattered at small angles with accuracies of 0.4% for the longitudinal momentum and 5 MeV for the transverse momentum. Photoproduction of ρ0 mesons has been investigated in the interval 0.073 &lt; |t| &lt; 0.40 GeV2, for photon virtualities Q2 &lt; 1 GeV2 and photon-proton centre-of-mass energies W between 50 and 100 GeV. In the measured range, the t distribution exhibits an exponential shape with a slope parameter b = 9.8 ± 0.8 (stat.) ± 1.1 (syst.) GeV-2. The use of the LPS eliminates the contamination from events with diffractive dissociation of the proton into low mass states. © Springler-Verlag 1997