Review of recent results in spin physics

Recent results in polarized DIS are reviewed. Particular emphasis is placed on new measurements of transverse and longitudinal asymmetries, on the tests of the spin sum rules and on the analysis of the spin structure function $g_1$ in perturbative QCD at NLO.Comment: 15 pages, LaTex, 15 eps figures included, to be published in Proceedings of 7th Int. Workshop on Deep Inelastic Scattering and QCD (DIS99

A Polarized HERA Collider

A brief review is given of the status of nucleon spin structure functions as determined from polarized deep inelastic lepton-nucleon scatttering, including current outstanding problems. The characteristics of a polarized HERA collider, some of the particle physics topics it could address, and the accelerator physics challenges it must meet are discussed.Comment: 5 Pages, 6 Figures, To be published in the Proceedings of the DIS99 Conference April 1999, DESY Zeuthen, German

A multi-objective optimisation model for a general polymer electrolyte membrane fuel cell system

This paper presents an optimisation model for a general polymer electrolyte membrane (PEM) fuel cell system Suitable for efficiency and size trade-offs investigation. Simulation of the model for a base case shows that for a given output power, a more efficient system is bigger and vice versa. Using the weighting method to perform a multi-objective optimisation, the Pareto sets were generated for different stack output powers. A Pareto set, presented as a plot of the optimal efficiency and area of the membrane electrode assembly (MEA), gives a quantitative description of the compromise between efficiency and size. Overall, our results indicate that, to make the most of the size-efficiency trade-off behaviour, the system must be operated at an efficiency of at least 40% but not more than 47%. Furthermore, the MEA area should be at least 3 cm(2) W-1 for the efficiency to be practically useful. Subject to the constraints imposed on the model, which are based on technical practicalities, a PEM fuel cell system such as the one presented in this work cannot operate at an efficiency above 54%. The results of this work, specifically the multi-objective model, will form a useful and practical basis for subsequent techno-economic studies for specific applications. (C) 2009 Elsevier B.V. All rights reserved

Flavor Singlet Axial Coupling of the Proton - An Updated Analysis

We present a combined analysis of SESAM and TxL data for the flavor singlet axial coupling G_A^1 of the proton, which is very helpful to stabilize the disconnected signals at small quark masses. From connected and disconnected contributions we use the tadpole improved renormalization constant Z_A and obtain G_A^1=0.21(12).Comment: 3 pages, contribution to LATTICE99 (matrix elements

Spin dependent structure function g1g_1 at small xx and small Q2Q^2

Theoretical expectations concerning the low $x$ and low $Q^2$ behaviour of $g_1$ are summarized and compared with the recent SMC data.Comment: 4 pages, plain LATEX, 1 eps figure; contribution to 3rd UK Phenomenology Workshop on HERA Physics, St. John's College, Durham, UK, September 199

Polarized lepton nucleon scattering - summary of the experimental spin sessions at DIS 99

This paper summarizes the contributions to the experimental sessions on polarized lepton nucleon scattering at the DIS 99 workshop. Results are reported about the flavor decomposition of the quark polarization, a first direct measurement of a positive gluon polarization, the observation of a double-spin asymmetry in diffractive rho production, the polarization of lambda hyperons, the observation of transverse single-spin asymmetries and the measurement of the Gerasimov-Drell-Hearn sum rule. Prospects of future fixed target and collider facilities are discussed.Comment: 8 pages, 5 figures, Proc. of the 7th Int. Workshop on Deep Inelastic Scattering and QCD (DIS99), Zeuthen, Germany, April 19-23, 1999, to appear in Nucl. Phys. B (Proc. Suppl.

The spin content of the proton in full QCD

We present preliminary results on the proton spin structure function in full QCD. The measurement has been done using 4 flavours of staggered fermions and an improved definition of the lattice topological charge density.Comment: 3 pages, 3 figures, contribution to Lattice-97. Latex file including espcrc2.sty. The colour of a line in the first figure has been changed to avoid problems on some printer

Parton distributions in a constituent quark scenario

A simple picture of the constituent quark as a composite system of point-like partons is used to construct the unpolarized and polarized parton distributions by a convolution between constituent quark momentum distributions and constituent quark structure functions. We achieve good agreement with experiments in the unpolarized, as well as, in the polarized case. When our results are compared with similar calculations using non-composite constituent quarks, the accord with the experiments of the present scheme is impressive. We conclude that DIS data are consistent with a low energy scenario dominated by composite constituents of the nucleon.Comment: 4 pages; latex using espcrc1.sty; 4 postscript figures; Invited talk at the Workshop ``Nucleon '99'', Frascati; Italy 7-9 June 1999. Submitted to Nuc. Phys.