Quark Flavor Tagging in Polarized Hadronic Processes

We describe a general approach to quark flavor tagging in polarized hadronic processes, with particular emphasis on semi-inclusive deep inelastic scattering. A formalism is introduced that allows one to relate chosen quark flavor polarizations to an arbitrary combination of final-state hadron spin asymmetries. Within the context of the presented formalism, we quantify the sensitivity of various semi-inclusive hadron asymmetries to the light quark flavors. We show that unpolarized Lambda's may allow one to measure strange quark and antiquark polarizations independently. We also highlight several applications of our formalism, particularly to measurements intended to probe further the spin structure of the nucleon.Comment: 5 pages, 2 EPS figures (new), version to be published in PRD (Rapid Communication

Precision Determination of the Neutron Spin Structure Function g1n

We report on a precision measurement of the neutron spin structure function $g^n_1$ using deep inelastic scattering of polarized electrons by polarized ^3He. For the kinematic range 0.014<x<0.7 and 1 (GeV/c)^2< Q^2< 17 (GeV/c)^2, we obtain $\int^{0.7}_{0.014} g^n_1(x)dx = -0.036 \pm 0.004 (stat) \pm 0.005 (syst)$ at an average $Q^2=5 (GeV/c)^2$. We find relatively large negative values for $g^n_1$ at low $x$. The results call into question the usual Regge theory method for extrapolating to x=0 to find the full neutron integral $\int^1_0 g^n_1(x)dx$, needed for testing quark-parton model and QCD sum rules.Comment: 5 pages, 3 figures To be published in Phys. Rev. Let

Radiation emission of autoionising hole states of Al induced by XUV free electron laser radiation with FLASH at DESY

The analysis of the radiative properties of plasmas created by XUV and X-ray free electron laser radiations provides a tremendous challenge to researchers to investigate matter under extreme conditions. In the present work we report about the theoretical analysis of the radiation emission of Al heated by the interaction of 10 fs focused (1 μm) free electron laser radiation at 13.5 nm at intensities of about 1016 W/cm2. The data show strong resonance line emission 3l -2l′ from Ne-like Al but also numerous intense broad emission structures in the spectral range from 10-30 nm. Atomic structure analysis indicate that these emission structures might originate from multiple excited states with L-holes. By means of a genetic algorithm we analyze possible excitation channels driven directly by the FLASH free electron laser as well as by heated plasma electrons

XUV Emission from Autoionizing Hole States Induced by Intense XUV-FEL at Intensities up to 101710^{17} W/cm2cm^2

Aluminium targets were irradiated with 92 eV radiation from FLASH Free Electron Laser at DESY at intensities up to 1017 W/cm2 by focussing the beam on target down to a spot size of ∼1 μm by means of a parabolic mirror. High resolution XUV spectroscopy was used to identify aluminium emission from complex hole-states. Simulations carried out with the MARIA code show that the emission characterizes the electron heating in the transition phase solid-atomic. The analysis allows constructing a simple model of electron heating via Auger electrons. © 2010 IOP Publishing Ltd