Nucleon parton distributions in a light-front quark model

Continuing with our analysis of parton distributions in the nucleon, we extend our light-front quark model in order to obtain both the helicity independent and helicity dependent parton distributions, analytically matching the results of global fits at the initial scale $\mu \sim 1$ GeV, and which also contain the correct Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution. We also calculate the transverse parton, Wigner and Husimi distributions from a unified point of view, using our light-front wave functions and expressing them in terms of the parton distributions $q_v(x)$ and $\delta q_v(x)$. Our results are very relevant for the current and future program of the COMPASS experiment at SPS (CERN)

Possible hadronic molecule structure of the Y(3940) and Y(4140)

In the present article we report on evidence for hadronic molecule structures in the charmonium sector. In particular we discuss the Y(3940) and the recently observed Y(4140) as heavy hadron molecule states with quantum numbers $J^{PC} = 0^{++}$ or $2^{++}$. The Y(3940) state is considered to be a superposition of $D^{\ast +}D^{\ast -}$ and $D^{\ast 0} \overline{D^{\ast 0}}$, while the Y(4140) is a bound state of $D_s^{\ast +}$ and $D_s^{\ast -}$ mesons. We give predictions for both the strong Y(3940) to J/psi omega, Y(4140) to J/psi phi and radiative Y(3940)/Y(4140) to gamma gamma decay widths in a phenomenological Lagrangian approach. The results for the strong hidden charm decay modes clearly support the molecular interpretation of the Y(3940) and Y(4140), while our estimates for the radiative decays provide a sensitive test for the underlying meson structure of the two Y mesons discussed here. The alternative assignment of $J^{PC} = 2^{++}$ is also tested, giving similar results for the strong decay widths.Comment: 5 pages, 2 figures. To appear in the Proceedings of XIII International Conference on Hadron Spectroscopy, November 29 - December 4, 2009, Florida State Universit

Nucleon Properties in the Perturbative Chiral Quark Model

We apply the perturbative chiral quark model (PCQM) to analyse low-energy nucleon properties: electromagnetic form factors, meson-nucleon sigma-terms and pion-nucleon scattering. Baryons are described as bound states of valence quarks surrounded by a cloud of Goldstone bosons (pi, K, eta) as required by chiral symmetry. The model is based on the following guide lines: chiral symmetry constraints, fulfilment of low-energy theorems and proper treatment of sea-quarks, that is meson cloud contributions. Analytic expressions for nucleon observables are obtained in terms of fundamental parameters of low-energy pion-nucleon physics (weak pion decay constant, axial nucleon coupling constant, strong pion-nucleon form factor) and of only one model parameter (radius of the nucleonic three-quark core). Our results are in good agreement with experimental data and results of other theoretical approaches.Comment: 8 pages. Invited talk given at Workshop on the Physics of Excited Nucleons "NSTAR2001", Mainz, Germany, March 7-10, 200

Decay Widths of X(1835) as Nucleon-Antinucleon Bound State

Partial decay widths of various decay channels of the X(1835) are evaluated in the 3P0 quark model, assuming that the X(1835) is a nucleon-antinucleon bound state. It is found that the decays to rho+rho, omega+omega and pion+a0(1450) dominate over other channels, and that the product branching fractions of J/psi to pion+pion+eta and J/psi to pion+pion+eta' are in the same order. We suggest that the X(1835) may be searched in the pion+a0(1450) channel.Comment: Changed X(1850) to X(1835) in Abstrac

Ökobilanz integrierter und ökologischer Apfelerzeugung in Hamburg

In 1997-1999 a life-cycle assessment of organic-extensive, organic-intensive and integrated apple production in Hamburg was carried out. The investigation was based on an analysis of 7 organic and 7 integrated farms in Hamburg and the surrounding area. The life-cycle assessment included 12 impact categories. The functional unit (1 kg apple or 1 ha farm land) differed depending on the impact categories. Compared to integrated production, organic production gave advantages in the impact categories ecotoxicity, human toxicity, drinking water protection, biodiversity and landscape image, whereas integrated production showed better results in the environmental effects that are caused by energy use. The investigation revealed potential for optimisation of organic production concerning the biotope structure, the use of copper preparations and especially the use of energy and machinery