Benefits of ecological engineering practices

With the intention to further promote the field of ecological engineering and the solutions it provides, a workshop on “Benefits of Ecological Engineering Practices” was held 3 December 2009. It was conducted by the International Ecological Engineering Society in Paris at the conference “Ecological Engineering: from Concepts to Application” organized by the Ecological Engineering Applications Group GAIE. This paper presents the results of the workshop related to three key questions: (1) what are the benefits of ecological engineering practices to human and ecosystem well-being, (2) which concepts are used or useful to identify, reference, and measure the benefits of ecological engineering practices, and (3) how and to whom shall benefits of ecological engineering practices be promoted. While benefits of ecological engineering practices are diverse, general conclusions can be derived to facilitate communication. Identifying benefits requires valuation frameworks reaching beyond the scope of ecology and engineering. A distinction between human and ecosystem well-being in this regard may not be easy or useful, but instead humans embedded in ecosystems should be addressed as a whole. The concepts of resource efficiency, ecosystem services, ecosystem health, and multifunctional land use could serve as suitable references to frame ecological engineering benefits, as well as referring to international political goals such as biodiversity protection, climate change mitigation and poverty reduction. Sector and application specific criteria of good practice could be worked out. Regional, area specific reference systems for sustainable development could provide comparative advantages for ecologically engineered solutions. Besides people with high decision making power and people with high motivation for change are good target groups to be addressed

Measurement of the proton and deuteron structure functions, F2p and F2d, and of the ratio sigma(L)/sigma(T)

The muon-proton and muon-deuteron inclusive deep inelastic scattering cross sections were measured in the kinematic range 0.002 < x < 0.60 and 0.5 < Q2 < 75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV. These results are based on the full data set collected by the New Muon Collaboration, including the data taken with a small angle trigger. The extracted values of the structure functions F2p and F2d are in good agreement with those from other experiments. The data cover a sufficient range of y to allow the determination of the ratio of the longitudinally to transversely polarised virtual photon absorption cross sections, R= sigma(L)/sigma(T), for 0.002 < x < 0.12 . The values of R are compatible with a perturbative QCD prediction; they agree with earlier measurements and extend to smaller x.Comment: In this replacement the erroneously quoted R values in tables 3-6 for x>0.12, and R1990 values in tables 5-6 for all x, have been corrected, and the cross sections in tables 3-4 have been adapted. Everything else, including the structure functions F2, remained unchanged. 22 pages, LateX, including figures, with two .sty files, and three separate f2tab.tex files for the F2-tables. Accepted for publication in Nucl.Phys.B 199

Flavor decomposition of the sea quark helicity distributions in the nucleon from semi-inclusive deep-inelastic scattering

Double-spin asymmetries of semi-inclusive cross sections for the production of identified pions and kaons have been measured in deep-inelastic scattering of polarized positrons on a polarized deuterium target. Five helicity distributions including those for three sea quark flavors were extracted from these data together with re-analyzed previous data for identified pions from a hydrogen target. These distributions are consistent with zero for all three sea flavors. A recently predicted flavor asymmetry in the polarization of the light quark sea appears to be disfavored by the data.Comment: 5 pages, 3 figure

Single-spin asymmetries in semi-inclusive deep-inelastic scattering on a transversely polarized hydrogen target

Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic scattering of positrons are measured for the first time with transverse target polarization. The asymmetry depends on the azimuthal angles of both the pion ($\phi$) and the target spin axis ($\phi_S$) about the virtual photon direction and relative to the lepton scattering plane. The extracted Fourier component \cmpi is a signal of the previously unmeasured quark transversity distribution, in conjunction with the so-called Collins fragmentation function, also unknown. The Fourier component \smpi of the asymmetry arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson productio

Evidence for Quark-Hadron Duality in the Proton Spin Asymmetry A1A_1

Spin-dependent lepton-nucleon scattering data have been used to investigate the validity of the concept of quark-hadron duality for the spin asymmetry $A_1$. Longitudinally polarised positrons were scattered off a longitudinally polarised hydrogen target for values of $Q^2$ between 1.2 and 12 GeV$^2$ and values of $W^2$ between 1 and 4 GeV$^2$. The average double-spin asymmetry in the nucleon resonance region is found to agree with that measured in deep-inelastic scattering at the same values of the Bjorken scaling variable $x$. This finding implies that the description of $A_1$ in terms of quark degrees of freedom is valid also in the nucleon resonance region for values of $Q^2$ above 1.6 GeV$^2$.Comment: 5 pages, 1 eps figure, table added, new references added, in print in Phys. Rev. Let

Observation of a Single-Spin Azimuthal Asymmetry in Semi-Inclusive Pion Electro-Production

Single-spin asymmetries for semi-inclusive pion production in deep-inelastic scattering have been measured for the first time. A significant target-spin asymmetry of the distribution in the azimuthal angle phi of the pion relative to the lepton scattering plane was observed for pi+ electro-production on a longitudinally polarized hydrogen target. The corresponding analyzing power in the sin(phi) moment of the cross section is 0.022 +/- 0.005 +/- 0.003. This result can be interpreted as the effect of terms in the cross section involving chiral-odd spin distribution functions in combination with a time-reversal-odd fragmentation function that is sensitive to the transverse polarization of the fragmenting quark.Comment: 5 pages of RevTex, 3 ps figures, 2 table

Search for an exotic S=-2, Q=-2 baryon resonance at a mass near 1862 MeV in quasi-real photoproduction

A search for an exotic baryon resonance with $S=-2, Q=-2$ has been performed in quasi-real photoproduction on a deuterium target through the decay channel $\Xi^- \pi^- \to \Lambda \pi^- \pi^- \to p \pi^- \pi^- \pi^-$. No evidence for a previously reported $\Xi^{--}(1860)$ resonance is found in the $\Xi^- \pi^-$invariant mass spectrum. An upper limit for the photoproduction cross section of 2.1 nb is found at the 90% confidence level. The photoproduction cross section for the $\Xi^{0}(1530)$ is found to be between 9 and 24 nb

Measurement of Longitudinal Spin Transfer to Lambda Hyperons in Deep-Inelastic Lepton Scattering

Spin transfer in deep-inelastic Lambda electroproduction has been studied with the HERMES detector using the 27.6 GeV polarized positron beam in the HERA storage ring. For an average fractional energy transfer = 0.45, the longitudinal spin transfer from the virtual photon to the Lambda has been extracted. The spin transfer along the Lambda momentum direction is found to be 0.11 +/- 0.17 (stat) +/- 0.03 (sys); similar values are found for other possible choices for the longitudinal spin direction of the Lambda. This result is the most precise value obtained to date from deep-inelastic scattering with charged lepton beams, and is sensitive to polarized up quark fragmentation to hyperon states. The experimental result is found to be in general agreement with various models of the Lambda spin content, and is consistent with the assumption of helicity conservation in the fragmentation process.Comment: 8 pages, 3 figures; new version has an expanded discussion and small format change

Beam-Induced Nuclear Depolarisation in a Gaseous Polarised Hydrogen Target

Spin-polarised atomic hydrogen is used as a gaseous polarised proton target in high energy and nuclear physics experiments operating with internal beams in storage rings. When such beams are intense and bunched, this type of target can be depolarised by a resonant interaction with the transient magnetic field generated by the beam bunches. This effect has been studied with the HERA positron beam in the HERMES experiment at DESY. Resonances have been observed and a simple analytic model has been used to explain their shape and position. Operating conditions for the experiment have been found where there is no significant target depolarisation due to this effect.Comment: REVTEX, 6 pages, 5 figure

The Q^2-Dependence of Nuclear Transparency for Exclusive ρ0\rho^0 Production

Exclusive coherent and incoherent electroproduction of the $\rho^0$ meson from $^1$H and $^{14}$N targets has been studied at the HERMES experiment as a function of coherence length ($l_c$), corresponding to the lifetime of hadronic fluctuations of the virtual photon, and squared four-momentum of the virtual photon ($-Q^2$). The ratio of $^{14}$N to $^1$H cross sections per nucleon, known as nuclear transparency, was found to increase (decrease) with increasing coherence length for coherent (incoherent) $\rho^0$ electroproduction. For fixed coherence length, a rise of nuclear transparency with $Q^2$ is observed for both coherent and incoherent $\rho^0$ production, which is in agreement with theoretical calculations of color transparency.Comment: 5 pages, 4 figure