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

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

Measurement of the reaction γ∗p→ϕp\gamma^*p \rightarrow \phi p in deep inelastic e+pe^+p scattering at HERA

The production of phi mesons in the reaction e(+)p --> e(+)phi p (phi --> K+K-), for 7 phi p cross section rises strongly with W. This behaviour is similar to that previously found for the gamma*p --> rho(0)p cross section. This strong dependence cannot be explained by production through soft pomeron exchange, It is, however, consistent with perturbative QCD expectations, where it reflects the rise of the gluon momentum density in the proton at small x. The ratio of sigma(phi)/sigma(rho(0)), which has previously been determined by ZEUS to be 0.065 +/- 0.013 (stat.) in photoproduction at a mean W of 70 GeV, is measured to be 0.18 +/- 0.05 (stat.) +/- 0.03 (syst.) at a mean Q(2) of 12.3 GeV2 and mean W of approximate to 100 GeV and is thus approaching at large Q(2) the value of 2/9 predicted from the quark charges of the vector mesons and a flavour independent production mechanism

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

High energy physics studies. Progress report. Part I. Experimental program. Part II. Theoretical program. [Summaries of research activities at Ohio State University]

Experimental Program: assembly of an experiment as Fermilab E-531 to measure decay lifetimes, with tagged emulsion of charmed particles produced by high energy neutrinos was finished, and data taking now is in progress. An experiment to measure prompt neutrino production at Fermilab, E-613, was approved and detailed design of it is continuing. Search for parity violation in scattering of polarized protons, an experiment E-446-ZGS at ANL, was performed with the sensitivity of 10/sup -6/ for detection of that process and yielded null results. Another run with improved sensitivity of 10/sup -7/ is in preparation. Data analysis of the neutrino experiment E-310 at Fermilab will continue. Trimuon events, a new discovery, were identified in those data. Analysis of data on meson production from experiments performed at the ZGS--ANL, E-397, E-420 and E-428, with charged and neutral spectrometer will continue. A new relatively broad resonance (T approx. 70 MeV) with quantum numbers IJ/sup P/ = 00/sup -1/ was discovered in the data from E-397. Analysis of beta decay of polarized ..sigma../sup -/ hyperons is in progress. Participation in the design of the experimental areas for the Isabelle colliding proton beam accelerator will continue. Theoretical Program: topics which will be investigated in the coming year are: the instanton-anti-instanton QCD gauge fields, discrete symmetries which may determine quark masses in the SU(2) x U(1) model, calculation of charmed meson production in e/sup +/e/sup -/ collisions and formation of gluon jets, Higgs boson production in pp collisions, calculation of Higgs boson mass in terms of vector boson mass, study of Lagrangians with gauge and Higgs scalar fields, investigation of Faddeev--Popov determinants as related to quantum chromodynamics, a study of quantum flavor dynamics and anomalies in the axial vector Ward identity and a study of super symmetry as a part of a realistic model of leptonic interactions. A list of publications is included