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.
17108236
Measurement of charm fragmentation ratios and fractions in photoproduction at HERA
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
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. 
119232865
Diffractive photoproduction of dijets in ep collisions at HERA
Diffractive photoproduction of dijets was measured with the ZEUS detector at the ep collider HERA using an integrated luminosity of 77.2 pb-1. The measurements were made in the kinematic range Q2 < 1 GeV2, 0.20<y<0.85 and xIP<0.025, where Q2 is the photon virtuality, y is the inelasticity and xIP is the fraction of the proton momentum taken by the diffractive exchange. The two jets with the highest transverse energy, ETjet, were required to satisfy ETjet>7.5 and 6.5 GeV, respectively, and to lie in the pseudorapidity range -1.5<ηjet<1.5. Differential cross sections were compared to perturbative QCD calculations using available parameterisations of diffractive parton distributions of the proton. 
125090919
Search for lepton-flavor violation at HERA
A search for lepton-flavor-violating interactions ep -> mu X and ep -> tau X has been performed with the ZEUS detector using the entire HERA I data sample, corresponding to an integrated luminosity of 130 pb(-1). The data were taken at center-of-mass energies, root s, of 300 and 318 GeV. No evidence of lepton-flavor violation was found, and constraints were derived on leptoquarks (LQs) that could mediate such interactions. For LQ masses below root s, limits were set on lambda(eq1) root beta(lq), where lambda(eq1) is the coupling of the LQ to an electron and a first-generation quark q(1), and beta(eq) is the branching ratio of the LQ to the final-state lepton l (mu or tau) and a quark q. For LQ masses much larger than root s, limits were set on the four-fermion interaction term lambda(eq alpha)lambda(eq beta)/M(L)(2)Q for LQs that couple to an electron and a quark q(alpha) and to a lepton l and a quark q(beta), where alpha and beta are quark generation indices. Some of the limits are also applicable to lepton-flavor-violating processes mediated by squarks in R-Parity-violating supersymmetric models. In some cases, especially when a higher-generation quark is involved and for the process ep -> tau X, the ZEUS limits are the most stringent to date.
29379793
Scaled momentum spectra in deep inelastic scattering at HERA
Charged particle production has been studied in neutral current deep inelastic ep scattering with the ZEUS detector at HERA using an integrated luminosity of 0.44 fb−1. Distributions of scaled momenta in the Breit frame are presented for particles in the current fragmentation region. The evolution of these spectra with the photon virtuality, Q2, is described in the kinematic region 10 < Q2 < 41000Ge V2. Next-to-leading-order and modified leading-log-approximation QCD calculations as well as predictions from Monte Carlo models are compared to the data. The results are also compared to e+e− annihilation data. The dependences of the pseudorapidity distribution of the particles on Q2 and on the energy in the γp system, W, are presented and interpreted in the context of the hypothesis of limiting fragmentation.
121588345
Coupled-channels study of fine structure in the {alpha} decay of well deformed nuclei
We formulate a theoretical model for the {alpha} decay of well-deformed even-even nuclei based on the coupled-channel Schroedinger equation. The {alpha}-decay half-lives and fine structures observed in {alpha} decay are well described by the five-channel microscopic calculations. Since the branching ratios to high-spin states are hard to understand in the traditional {alpha}-decay theories, this success could be important to interpret future observations of heavier nuclei. It is also found that the {alpha} transition to high-spin states is a powerful tool to probe the energy spectrum and deformation of daughter nuclei.
121138073
BESII detector simulation
A Monte Carlo program based on GEANT3 has been developed for BESII detector simulation. The organization of the program is outlined, and the digitization procedure for simulating the response of various sub-detectors is described. Comparisons with data show that the performance of the program is generally satisfactory.
55143067
Systematic Law for Half-lives of Double $\beta$-decay with Two Neutrinos
Nuclear double $\beta$-decay with two neutrinos is a rare and important process for natural radioactivity of unstable nuclei. The experimental data of nuclear double $\beta^{-}$-decay with two neutrinos are analyzed and a systematic law to calculate the half-lives of this rare process is proposed. It is the first analytical and simple formula for double $\beta$-decay half-lives where the leading effect from both the Coulomb potential and nuclear structure is included. The systematic law shows that the logarithms of the half-lives are inversely proportional to the decay energies for the ground state transitions between parent nuclei and daughter nuclei. The calculated half-lives are in agreement with the experimental data of all known eleven nuclei with an average factor of 3.06. The half-lives of other possible double $\beta$-decay candidates with two neutrinos are predicted and these can be useful for future experiments. The law, without introducing any extra adjustment, is also generalized to the calculations of double $\beta $-decay half-lives from the ground states of parent nuclei to the first $0^+$ excited states of daughter nuclei and the calculated half-lives agree very well with the available data. Some calculated half-lives are the first theoretical results of double $\beta $-decay half-lives from the ground states of parent nuclei to the first $0^+$ excited states of daughter nuclei. The similarity and difference between the law of $\alpha$-decay and that of double $\beta^{-}$-decay are also analyzed and discussed.
122517028
Structure of 8Li from a reaction cross-section measurement
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.
122071638
Half-lives and cluster preformation factors for various cluster emissions in trans-lead nuclei
The generalized density-dependent cluster model (GDDCM) is extended to study cluster radioactivity in even-even and odd-$A$ nuclei decaying to the doubly magic nucleus $^{208}\mathrm{Pb}$ or its neighboring nuclei. The microscopic cluster-daughter potential is numerically constructed in the double-folding model with M3Y nucleon-nucleon interactions plus proton-proton Coulomb interactions. Instead of the WKB barrier penetration probability, the exact solution of the Schr\"odinger equation with outgoing Coulomb wave boundary conditions is presented. The cluster preformation factor is well taken into account based on some available experimental cases. The calculated half-lives are found to be in good agreement with the experimental data. This indicates that a unified description of $\ensuremath{\alpha}$ decay and cluster radioactivity has been achieved by the GDDCM. Predictions of cluster emission half-lives are made for promising emitters, which may guide future experiments.