Double-Spin Asymmetry in the Cross Section for Exclusive rho^0 Production in Lepton-Proton Scattering

Evidence for a positive longitudinal double-spin asymmetry = 0.24 +-0.11 (stat) +-0.02 (syst) in the cross section for exclusive diffractive rho^0(770) vector meson production in polarised lepton-proton scattering was observed by the HERMES experiment. The longitudinally polarised 27.56 GeV HERA positron beam was scattered off a longitudinally polarised pure hydrogen gas target. The average invariant mass of the photon-proton system has a value of = 4.9 GeV, while the average negative squared four-momentum of the virtual photon is = 1.7 GeV^2. The ratio of the present result to the corresponding spin asymmetry in inclusive deep-inelastic scattering is in agreement with an early theoretical prediction based on the generalised vector meson dominance model.Comment: 10 pages, 4 embedded figures, LaTe

Double spin asymmetry in exclusive rho^0 muoproduction at COMPASS

The longitudinal double spin asymmetry A_1^rho for exclusive leptoproduction of rho^0 mesons, mu + N -> mu + N + rho, is studied using the COMPASS 2002 and 2003 data. The measured reaction is incoherent exclusive rho^0 production on polarised deuterons. The Q^2 and x dependence of A_1^rho is presented in a wide kinematical range: 3x10^-3 < Q^2 < 7 (GeV/c)^2 and 5x10^-5 < x < 0.05. The presented results are the first measurements of A_1^rho at small Q2 (Q2 < 0.1 (GeV/c)^2) and small x (x < 3x10^-3). The asymmetry is in general compatible with zero in the whole kinematical range.Comment: 6 Figures, 15 pages, version 2 with updated author list, technical latex problem fixe

Expression of mRNA for the neurotrophin receptor trkC in neuroblastomas with favourable tumour stage and good prognosis

Childhood neuroblastoma rumours of the sympathetic nervous system show a remarkable clinical heterogeneity ranging from spontaneous regression to unfavourable outcome despite intensive therapy. Favourable neuroblastomas often express high levels of trkA mRNA, encoding the tyrosine kinase receptor for nerve growth factor. We have investigated mRNA expression for the neurotrophin receptor trkC in 23 primary neuroblastomas using a sensitive RNAase protection assay. TrkC expression was detected in 19 of these rumours al highly variable levels with a 300-fold difference between the highest and lowest values. Significantly higher levels of trkC mRNA were found in tumours from patients with favourable features such as low age (P < 0.012), favourable tumour stage (P < 0.012) and favourable prognosis (P < 0.05). Children with intermediate or high trkC mRNA expression had better prognosis compared with those with low or undetectable levels (83.3% vs 20%: P = 0.005). Further characterisation of trkC mRNA expression by reverse transcriptase-polymerase chain reaction (RT-PCR) showed that mRNA encoding the full-length cytoplasmic tyrosine kinase domain of the receptor was only expressed in a subset of favourable tumours. These data show that favourable neuroblastomas may express the full trkC receptor while advanced rumours, in particular MYCN-amplified neuroblastoma, seem to either express no trkC or truncated trkC receptors of as yet unknown biological function. These data are suggestive of a role for trkC and its preferred ligand neutotrophin-3, NT-3, in neuroblastoma differentiation and/or regression