Measurement of high-Q2neutral current deep inelastice+pscattering cross sections with a longitudinally polarized positron beam at HERA
SOURCE (OR PART OF THE FOLLOWING SOURCE): Type article Title Measurement of high-Q2 neutral current deep inelastic e+p scattering cross sections with a longitudinally polarized positron beam at HERA Author(s) H. Abramowicz, . et al, G. Grigorescu, A. Keramidas, E. Koffeman, P. Kooijman, A. Pellegrino, H. Tiecke, M. Vazquez, L. Wiggers Faculty FNWI: Institute for High Energy Physics (IHEF) Year 2013

title: Measurement of charm fragmentation ratios and fractions in photoproduction at HERA
abstract: The production of D, D, D, D s and Λ + c charm hadrons and their antiparticles in ep scattering at HERA was measured with the ZEUS detector using an integrated luminosity of 79 pb. The measurement has been performed in the photoproduction regime with the exchanged-photon virtuality Q < 1 GeV and for photon-proton centre-of-mass energies in the range 130 < W < 300 GeV. The charm hadrons were reconstructed in the range of transverse momentum pT (D, Λc) > 3.8 GeV and pseudorapidity |η(D, Λc)| < 1.6. The production cross sections were used to determine the ratio of neutral and charged D-meson production rates, Ru/d, the strangeness-suppression factor, γs, and the fraction of charged D mesons produced in a vector state, P d v . The measured Ru/d and γs values agree with those obtained in deep inelastic scattering and in ee annihilations. The measured P d v value is smaller than, but consistent with, the previous measurements. The fractions of c quarks hadronising as a particular charm hadron, f(c → D, Λc), were derived in the given kinematic range. The measured open-charm fragmentation fractions are consistent with previous results, although the measured f(c → D) is smaller and f(c → Λc ) is larger than those obtained in ee annihilations. These results generally support the hypothesis that fragmentation proceeds independently of the hard sub-process. The ZEUS Collaboration S. Chekanov, M. Derrick, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida Argonne National Laboratory, Argonne, Illinois 60439-4815, USA n M.C.K. Mattingly Andrews University, Berrien Springs, Michigan 49104-0380, USA N. Pavel, A.G. Yagües Molina Institut für Physik der Humboldt-Universität zu Berlin, Berlin, Germany P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, A. Polini, L. Rinaldi, G. Sartorelli, A. Zichichi University and INFN Bologna, Bologna, Italy e G. Aghuzumtsyan, D. Bartsch, I. Brock, S. Goers, H. Hartmann, E. Hilger, P. Irrgang, H.-P. Jakob, O.M. Kind, U. Meyer, E. Paul, J. Rautenberg, R. Renner, M. Wang, M. Wlasenko Physikalisches Institut der Universität Bonn, Bonn, Germany b D.S. Bailey, N.H. Brook, J.E. Cole, G.P. Heath, T. Namsoo, S. Robins H.H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom m M. Capua, S. Fazio, A. Mastroberardino, M. Schioppa, G. Susinno, E. Tassi Calabria University, Physics Department and INFN, Cosenza, Italy e J.Y. Kim, K.J. Ma Chonnam National University, Kwangju, South Korea g M. Helbich, Y. Ning, Z. Ren, W.B. Schmidke, F. Sciulli Nevis Laboratories, Columbia University, Irvington on Hudson, New York 10027 o J. Chwastowski, A. Eskreys, J. Figiel, A. Galas, M. Gil, K. Olkiewicz, P. Stopa, D. Szuba, L. Zawiejski The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow, Poland i L. Adamczyk, T. Bo ld, I. Grabowska-Bo ld, D. Kisielewska, J. Lukasik, M. Przybycień, L. Suszycki, J. Szuba Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Cracow, Poland p A. Kotański, W. S lomiński Department of Physics, Jagellonian University, Cracow, Poland

title: Measurement of azimuthal asymmetries in neutral current deep inelastic scattering at HERA
abstract: The distribution of the azimuthal angle of charged and neutral hadrons relative to the lepton plane has been studied for neutral current deep inelastic ep scattering using an integrated luminosity of 45 pb-1 taken with the ZEUS detector. The kinematic range is 100<Q2<8000 GeV2, 0.2<y<0.8 and 0.01<x<0.1 where Q2 is the virtuality of the exchanged boson, y is the inelasticity and x is the Bjorken variable. The measurements were made in the hadronic centre-of-mass system. The analysis exploits the energy-flow method, which allows the measurement to be made over a larger range of pseudorapidity compared to previous results. The dependence of the moments of the azimuthal distributions on the pseudorapidity and minimum transverse energy of the final-state hadrons are presented. Although the predictions from next-to-leading-order QCD describe the data better than do the Monte Carlo models incorporating leading-logarithm parton showers, they still fail to describe the magnitude of the asymmetries. This suggests that higher-order calculations may be necessary to describe these data.

title: Measurement of isolated photons accompanied by jets in deep inelastic ep scattering
abstract: The production of isolated high-energy photons accompanied by jets has been measured in deep inelastic ep scattering with the ZEUS detector at HERA, using an integrated luminosity of 326pb -1 . Measurements were made for exchanged photon virtualities, Q 2 , in the range 10 to 350GeV 2 . The photons were measured in the transverse-energy and pseudorapidity ranges 4 γ jet <1.8. Differential cross sections are presented as functions of these quantities. Perturbative QCD predictions give a reasonable description of the shape of the measured cross sections over most of the kinematic range, but the absolute normalisation is typically in disagreement by 20-30%.

title: Measurement of prompt photons with associated jets in photoproduction at HERA
abstract: The photoproduction of prompt photons, together with an accompanying jet, has been studied in ep collisions at a centre-of-mass energy of 318 GeV with the ZEUS detector at HERA using an integrated luminosity of 77 pb-1. Cross sections were measured for the transverse energy of the photon and the jet larger than 5 and 6 GeV, respectively. The differential γ+jet cross sections were reconstructed as functions of the transverse energy, pseudorapidity and xγobs, the fraction of the incoming photon momentum taken by the photon-jet system. Predictions based on leading-logarithm parton-shower Monte Carlo models and next-to-leading-order (NLO) QCD generally underestimate the cross sections for the transverse energies of prompt photons below 7 GeV, while the kT-factorisation QCD calculation agrees with the data better. When the minimum transverse energy of prompt photons is increased to 7 GeV, both NLO QCD and the kT-factorisation calculations are in good agreement with the data.

title: The spectrometer system for measuring ZEUS luminosity at HERA
abstract: The upgrade of the HERA accelerator has provided much increased collider luminosity. In turn, the improvements have necessitated a new design for the ZEUS luminosity measurements. The intense synchrotron radiation field, as well as the high probability of a bremsstrahlung photon in each bunch crossing, posed new experimental constraints. In this report, we describe how these challenges were met with the ZEUS luminosity spectrometer system. The design, testing and commissioning of the device are described, and the results from the initial operational experience are reported.

title: Predictions on properties of alpha decay and spontaneous fission in superheavy odd-Z nuclei
abstract: We systematically investigate the competition between a decay and spontaneous fission in the region of superheavy odd-Z nuclei up to Z = 121. The heavier cluster emissions are somewhat of interest for these superheavy nuclei (SHN) as well. In detail, on the basis of the density-dependent cluster model, the deformed a-core potential is obtained from the double-folding integral. The a-decay half-lives of involved nuclei are then achieved within the improved two-potential approach. On the other hand, the spontaneous fission half-lives are given by the employed formula related to the fissility parameter and the fission barrier height. It is interesting that the decay characteristic of studied nuclei is discussed with varying of the Z and N numbers to some extent, including the tentative detection on the "island of stability." The present results can be expected to be useful in the future experiment particularly for the unknown elements 119 and 121, namely the identification of synthesized SHN.

title: Theoretical study of nuclear charge densities with elastic electron scattering
abstract: The calculated cross sections for elastic Coulomb electron scattering from the phase-shift analysis method and the eikonal approximation are compared. It is shown that the phase-shift analysis method can reproduce the experimental data very well for both light and heavy nuclei. Then the phase-shift analysis is used to investigate elastic electron scattering along the O and S isotopic chains, where the charge densities are obtained from relativistic mean-field theory. Results show that the minima of the differential cross section shift inward and upward with the increase of the neutron number.

title: New deformed model of α-decay half-lives with a microscopic potential
abstract: The {alpha}-decay half-lives of deformed nuclei are investigated in a new version of the density-dependent cluster model. By the multipole expansion method, the deformation- and orientation-dependent double-folding potential is derived to calculate the {alpha}-decay width through a deformed Coulomb barrier. We perform systematic calculations for the ground-state {alpha} transitions of even-even nuclei with Z=52-104. The theoretical results are in good agreement with the experimental data. This is, to our knowledge, the first deformed calculation of {alpha}-decay half-lives within the framework of microscopic double-folding potentials. A unified description of {alpha}-decay half-lives of both spherical and deformed nuclei is obtained by the microscopic potentials.

title: Systematic studies of properties of nuclei by parity violating electron scattering
abstract: Two investigations by the parity violating electron scattering are performed theoretically: one is to investigate the properties of the surface for neutron-rich nuclei such as {sup 124}Sn and {sup 208}Pb, and the other is to predict the parity violating asymmetries for some isotopic chains, such as Ba and Pb, which have been proposed for the atomic parity nonconservation experiments. For the first topic, the neutron and proton densities are taken to be the 2pF distributions. Results show that the parity violating asymmetries are very sensitive to the type of neutron density. It means that the parity violating electron scattering can be used to verify the type of neutron distribution in neutron-rich stable nuclei. For the second topic, the neutron and proton densities are obtained from the relativistic mean-field (RMF) theory. By combining the results for these two topics, we find that for various proton and neutron densities the amplitudes of the parity violating asymmetries correspond to the distances between the minima of the proton and neutron form factors. Our results can provide useful references for future experiments.

title: Structure of 8Li from a reaction cross-section measurement
abstract: We have precisely measured reaction cross sections (sigma(R)) for Li-8 using Be-9, C-12, Al-27, and proton targets at intermediate energies by the transmission method. From the energy dependence of the sigma(R) including the high energy data, the density distribution of Li-8 was deduced through a modified Glauber model. It is shown that Li-8 has a shorter tail structure in the density as compared with that of B-8 and the matter radius of Li-8 is similar to those of the other nonhalo Li isotopes. The result is consistent with the previous experiments that there is a tendency for Li-8 to be a skin nucleus.