16324397
An NLO QCD analysis of inclusive cross-section and jet-production data from the ZEUS experiment
The ZEUS inclusive differential cross-section data from HERA, for charged and neutral current processes taken with e(+) and e(-) beams, together with differential cross-section data on inclusive jet production in e+ p scattering and dijet production in gamma p scattering, have been used in a new NLO QCD analysis to extract the parton distribution functions of the proton. The input of jet-production data constrains the gluon and allows an accurate extraction of alpha(s)( M-Z) at NLO;alpha(s)( M-Z) = 0.1183 +/- 0.0028( exp.) +/- 0.0008( model).An additional uncertainty from the choice of scales is estimated as +/- 0.005. This is the first extraction of as( M-Z) from HERA data alone.
62786869
Measurement of isolated photons accompanied by jets in deep inelastic ep scattering
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%. © 2012 Elsevier B.V.
16863612
The spectrometer system for measuring ZEUS luminosity at HERA
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.
17225927
Measurement of azimuthal asymmetries in neutral current deep inelastic scattering at HERA
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. 
15474958
Measurement of prompt photons with associated jets in photoproduction at HERA
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.
53982386
Measurement of charged current deep inelastic scattering cross sections with a longitudinally polarised electron beam at HERA
Measurements of the cross sections for charged current deep inelastic scattering in e−p collisions with longitudinally polarised electron beams are presented. The measurements are based on a data sample with an integrated luminosity of 175 pb−1 collected with the ZEUS detector at HERA at a centre-of-mass energy of 318 GeV. The total cross section is given for positively and negatively polarised electron beams. The differential cross-sections dσ/dQ2, dσ/dx and dσ/dy are presented for Q2>200 GeV2. The double-differential cross-section d2σ/dxdQ2 is presented in the kinematic range 280<Q2<30 000 GeV2 and 0.015<x<0.65. The measured cross sections are compared with the predictions of the Standard Model.
118424814
Sensitivity of de-excitation energies of superdeformed secondary minima to the density dependence of symmetry energy with the relativistic mean-field theory
The relationship between de-excitation energies of superdeformed secondary minima relative to ground states and the density dependence of the symmetry energy is investigated for heavy nuclei using the relativistic mean-field (RMF) model. It is shown that the de-excitation energies of superdeformed secondary minima are sensitive to differences in the symmetry energy that are mimicked by the isoscalar-isovector coupling included in the model. With deliberate investigations on a few Hg isotopes that have data of de-excitation energies, we find that the description for the de-excitation energies can be improved due to the softening of the symmetry energy. Further, we have investigated de-excitation energies of odd-odd heavy nuclei that are nearly independent of pairing correlations, and have discussed the possible extraction of the constraint on the density dependence of the symmetry energy with the measurement of de-excitation energies of these nuclei.
119640767
Measurement of the final states omega pi0, rho eta, and rho eta prime from psi (2S) electromagnetic decays and e+e- annihilations
Cross sections and form factors for $\ee \to \wpi$, $\rho\eta$, and $\rho\etap$ at center of mass energies of 3.650, 3.686, and 3.773 GeV are measured using data samples collected with the BESII detector at the BEPC. Also, the branching fractions of $\psi(2S) \rar \wpi$, $\rho\eta$, and $\rho\etap$ are determined to be $(1.87^{+0.68}_{-0.62}\pm0.28)\times 10^{-5}$, $(1.78^{+0.67}_{-0.62}\pm0.17)\times 10^{-5}$, and $(1.87^{+1.64}_{-1.11}\pm0.33)\times10^{-5}$, respectively.
121943751
Theoretical study of nuclear charge densities with elastic electron scattering
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.
123351519
Systematic studies of properties of nuclei by parity violating electron scattering
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.
119327380
Branching ratios of $\alpha$-decay to excited states of even-even nuclei
We make a systematic calculation on $\alpha$-decay branching ratios to members of ground-state rotational band and to excited $0^{+}$ states of even-even nuclei by a simple barrier penetration approach. The branching ratios to the excited states of daughter nucleus are determined by the $\alpha$-decay energy, the angular momentum of $\alpha$-particle, and the excitation probability of the daughter nucleus. Our calculation covers isotopic chains from Hg to Fm in the mass regions 180$<$A$<$202 and A$\geq$224. The calculated branching ratios of $\alpha$-transitions are consistent with the experimental data. Some useful predictions are made for future experiments.