Measurement of Light-Cone Wave Functions by Diffractive Dissociation

Diffractive dissociation of particles can be used to study their light-cone wave functions. Results from Fermilab experiment E791 for diffractive dissociation of 500 GeV/c pi- mesons into di-jets show that the |q qbar> light-cone asymptotic wave function describes the data well for Q^2 ~ 10 (GeV/c)^2 or more.Comment: Talk given at the Recontres de Moriond, QCD and High Energy Hadronic Interactions, Les Arcs, March 2002. 5 pages 4 figure

The spin structure of the Lambda hyperon in quenched lattice QCD

It has been suggested to use the production of Lambda hyperons for investigating the nucleon spin structure. The viability of this idea depends crucially on the spin structure of the Lambda. Using nonperturbatively O(a) improved Wilson fermions in the quenched approximation we have studied matrix elements of two-quark operators in the Lambda. We present results for the axial vector current, which give us the contributions of the u, d, and s quarks to the Lambda spin.Comment: Lattice2001(matrixelement), 3 pages, 2 figure

Depopulation of dense α-synuclein aggregates is associated with rescue of dopamine neuron dysfunction and death in a new Parkinson's disease model.

Parkinson's disease (PD) is characterized by the presence of α-synuclein aggregates known as Lewy bodies and Lewy neurites, whose formation is linked to disease development. The causal relation between α-synuclein aggregates and PD is not well understood. We generated a new transgenic mouse line (MI2) expressing human, aggregation-prone truncated 1-120 α-synuclein under the control of the tyrosine hydroxylase promoter. MI2 mice exhibit progressive aggregation of α-synuclein in dopaminergic neurons of the substantia nigra pars compacta and their striatal terminals. This is associated with a progressive reduction of striatal dopamine release, reduced striatal innervation and significant nigral dopaminergic nerve cell death starting from 6 and 12 months of age, respectively. In the MI2 mice, alterations in gait impairment can be detected by the DigiGait test from 9 months of age, while gross motor deficit was detected by rotarod test at 20 months of age when 50% of dopaminergic neurons in the substantia nigra pars compacta are lost. These changes were associated with an increase in the number and density of 20-500 nm α-synuclein species as shown by dSTORM. Treatment with the oligomer modulator anle138b, from 9 to 12 months of age, restored striatal dopamine release, prevented dopaminergic cell death and gait impairment. These effects were associated with a reduction of the inner density of large α-synuclein aggregates and an increase in dispersed small α-synuclein species as revealed by dSTORM. The MI2 mouse model recapitulates the progressive dopaminergic deficit observed in PD, showing that early synaptic dysfunction is associated to fine behavioral motor alterations, precedes dopaminergic axonal loss and neuronal death that become associated with a more consistent motor deficit upon reaching a certain threshold. Our data also provide new mechanistic insight for the effect of anle138b's function in vivo supporting that targeting α-synuclein aggregation is a promising therapeutic approach for PD

Temperature dependence of J–V and C–V characteristics of n-InAs/p-GaAs heterojunctions prepared by flash evaporation technique and liquid phase epitaxy

In this work, n-type of InAs films have been successfully fabricated on p-GaAs monocrystalline substrates by both flash evaporation technique and liquid phase epitaxy. The elemental composition of the prepared films has been confirmed by energy dispersive X-ray (EDX) spectroscopy. The morphology of the films has been characterized by scanning electron microscopy (SEM). The current transport mechanisms of n-InAs/p-GaAs heterojunctions in the temperature range 300-400 K have been investigated. Temperature-dependent dark current density-voltage (J–V) studies under forward and reverse bias have been carried out for this purpose. In the temperature range studied, the dark current contribution in the low bias range is believed to be due to the generation-recombination of minority carriers in the space-charge region. A change in the preparation technique does not seem to have altered the dark current conduction mechanism. Capacitance-voltage (C–V) at various temperatures has been measured to identify the junction type as well as determination of the important junction parameters

Pion-nucleus reactions in a microscopic transport model

We analyse pion-nucleus reactions in a microscopic transport model of the BUU type, which propagates nucleons, pions, deltas and N(1440)-resonances explicitly in space and time. In particular we examine pion absorption and inelastic scattering cross sections for pion kinetic energies T(pi) =85-315MeV and various target masses. In general, the mass-dependence of the experimental data is well described for energies up to the delta-resonance (\approx 160 MeV) while the absorption cross sections are somewhat overestimated for the higher energies. In addition we study the possible dynamical effects of delta- and pion-potentials in the medium on various observables as well as alternative models for the in-medium delta-width.Comment: 31 pages, UGI-93-0

Tensor interaction constraints from beta decay recoil spin asymmetry of trapped atoms

We have measured the angular distribution of recoiling daughter nuclei emitted from the Gamow-Teller $\beta$ decay of spin-polarized $^{80}$Rb. The asymmetry of this distribution vanishes to lowest order in the Standard Model (SM) in pure Gamow-Teller decays, producing an observable very sensitive to new interactions. We measure the non-SM contribution to the asymmetry to be $A_{T}$= 0.015 $\pm$ 0.029 (stat) $\pm$ 0.019 (syst), consistent with the SM prediction. We constrain higher-order SM corrections using the measured momentum dependence of the asymmetry, and their remaining uncertainty dominates the systematic error. Future progress in determining the weak magnetism term theoretically or experimentally would reduce the final errors. We describe the resulting constraints on fundamental 4-Fermi tensor interactions.Comment: 11 pages, 13 figures; v2 published in Phys. Rev. C, with referee clarifications and figures improved for black-and-whit