Non-universality of transverse Coulomb exchange at small x

Within an explicit scalar QED model we compare, at fixed x << 1, the leading-twist K_T-dependent `quark' distribution f_q(x, K_T) probed in deep inelastic scattering and Drell-Yan production, and show that the model is consistent with the universality of f_q(x, K_T). The extension of the model from the aligned-jet to the 'symmetric' kinematical regime reveals interesting properties of the physics of Coulomb rescatterings when comparing DIS and DY processes. At small x the transverse momentum induced by multiple scattering on a single centre is process dependent, as well as the transverse momentum broadening occurring in collisions on a finite size nuclear target.Comment: 28 pages, 3 eps figure

Asymptotic geometry of negatively curved manifolds of finite volume

We study the asymptotic behavior of simply connected Riemannian manifolds X of strictly negative curvature admitting a non-uniform lattice Γ. If the quotient manifold X = Γ\X is asymptotically 1=4-pinched, we prove that Γ is divergent and U X has finite Bowen-Margulis measure (which is then ergodic and totally conservative with respect to the geodesic flow); moreover, we show that, in this case, the volume growth of balls B(x,R) in X is asymptotically equivalent to a purely exponential function c.x/eδR, where δ is the topological entropy of the geodesic flow of X . This generalizes Margulis' celebrated theorem to negatively curved spaces of finite volume. In contrast, we exhibit examples of lattices Γ in negatively curved spaces X (not asymptotically 1/4-pinched) where, depending on the critical exponent of the parabolic subgroups and on the finiteness of the Bowen- Margulis measure, the growth function is exponential, lower-exponential or even upper-exponential

Conservation tillage in organic farming

Organic farmers are interested in adopting conservation tillage to preserve soil quality and fertility and to prevent soil erosion. Within the framework of a French national study, we compared conventional (ploughing) and conservation tillage systems in organic farming for arable and vegetable cropping systems. Field experiments and on-farm surveys were conducted in several regions of France in order to assess the effects of different tillage systems on soil fertility (physical, chemical, biological) and on weed and crop development. Conservation tillage techniques induced a more compact soil, an increase of carbon and microorganisms in the first soil layer, and an increase of earthworm biomass for very superficial tillage. Weed control was only a major problem for the very superficial tillage, which in turn generated lower crop yields than conventional tillage. The main issues raised by this programme deal with the long-term effects of these techniques on soil fertility, and the improvement of conservation tillage techniques in organic farming

Initial-State Interactions and Single-Spin Asymmetries in Drell-Yan Processes

We show that the initial-state interactions from gluon exchange between the incoming quark and the target spectator system lead to leading-twist single-spin asymmetries in the Drell-Yan process. The QCD initial-state interactions produce a $T-$odd spin-correlation between the target spin and the virtual photon production plane which is not power-law suppressed in the Drell-Yan scaling limit. The origin of the single-spin asymmetry in $\pi p^\uparrow \to \ell^+ \ell^- X$ is a phase difference between two amplitudes coupling the proton target with $J^z_p = \pm {1\over 2}$ to the same final-state, the same amplitudes which are necessary to produce a nonzero proton anomalous magnetic moment. The calculation requires the overlap of target light-front wavefunctions differing by one unit of orbital angular momentum projection $L_z;$ thus the SSA in the Drell-Yan reaction provides a direct measure of orbital angular momentum in the QCD bound state. The single-spin asymmetry predicted for the Drell-Yan process $\pi p^\uparrow \to \ell^+ \ell^- X$ is similar to the single-spin asymmetries in deep inelastic semi-inclusive leptoproduction $\ell p^\uparrow \to \ell' \pi X$ which arises from the final-state rescattering of the outgoing quark.Comment: LaTex, 15 pages, 2 figure

System size dependence of nuclear modification and azimuthal anisotropy of jet quenching

We investigate the system size dependence of jet-quenching by analyzing transverse momentum spectra of neutral pions in Au+Au and Cu+Cu collisions at $\sqrt{s_{\textrm{NN}}}$ =200 GeV for different centralities. The fast partons are assumed to lose energy by radiating gluons as they traverse the plasma and undergo multiple collisions. The energy loss per collision, $\epsilon$, is taken as proportional to $E$(where $E$ is the energy of the parton), proportional to $\sqrt{E}$, or a constant depending on whether the formation time of the gluon is less than the mean path, greater than the mean free path but less than the path length, or greater than the path length of the partons, respectively. NLO pQCD is used to evaluate pion production by modifying the fragmentation function to account for the energy loss. We reproduce the nuclear modification factor $R_\textrm{AA}$ by treating $\epsilon$ as the only free parameter, depending on the centrality and the mechanism of energy loss. These values are seen to explain the nuclear modification of prompt photons, caused by the energy lost by final state quarks before they fragment into photons. These also reproduce the azimuthal asymmetry of transverse momentum distribution for pions within a factor of two and for prompt photons in a fair agreement with experimental data.Comment: 26 pages, 17 figures. One more figure added. Discussion expanded. Typographical corrections done, several references added. To appear in Journal of Physics

Degrees of Freedom of the Quark Gluon Plasma, tested by Heavy Mesons

Heavy quarks (charm and bottoms) are one of the few probes which are sensitive to the degrees of freedom of a Quark Gluon Plasma (QGP), which cannot be revealed by lattice gauge calculations in equilibrium. Due to the rapid expansion of the QGP energetic heavy quarks do not come to an equilibrium with the QGP. Their energy loss during the propagation through the QGP medium depends strongly on the modelling of the interaction of the heavy quarks with the QGP quarks and gluons, i.e. on the assuption of the degrees of freedom of the plasma. Here we compare the results of different models, the pQCD based Monte-Carlo (MC@sHQ), the Dynamical Quasi Particle Model (DQPM) and the effective mass approach, for the drag force in a thermalized QGP and discuss the sensitivity of heavy quark energy loss on the properties of the QGP as well as on non-equilibrium dynamicsComment: proceedings symposion "New Horizons" Makutsi, South Africa, Nov 201

Improving baking quality, nutritional value and safety of organic winter wheat / Améliorer la qualité technologique, nutritionnelle et sanitaire du blé biologique, Principaux leviers agronomiques et technologiques

The organic bread wheat market has been diversified over time through the emergence of different sale channels. Processors require organic bread wheat of higher quality and safety in order to meet the consumers’ demand. The overall objective of the AGTEC-Org project was to identify agronomical and technological ways to improve the performance of organic wheat and flour. The findings would contribute to enhanced baking quality and nutritional value of organic flour, as well as prevention of mycotoxin contamination. The project involved 9 research centers or universities from 5 European countries for a total budget of about 1.5 million €. More than 400 experimental treatments were analyzed from 23 agronomic trials and 4 lab-experiments on food technology. Choice of cultivar is an efficient way to obtain higher grain quality. Intercropping legumes (grain or forage) improves weed control and N availability for wheat crop or succeeding crop. Green manure can be an effective alternative to farmyard manure. Fertilization with organic fertilizers improves yield and quality when water is available. Reduced tillage affects soil fertility and wheat yield but has little effects on grain quality. Milling process strongly influences flour characteristics. Stone milling improves the nutritive value and flour characteristics remain very stable independently of the milling yield. However, stone milling slightly raises DON levels. Characteristics of flour produced by means of roller milling appear very dependent on milling yield, instead. Increasing milling yield with the aim of enriching nutritional quality has a detrimental effect on either safety (DON) or bread-making quality (bread volume). Debranning before milling has a very positive impact on flour safety by reducing its DON content by 50 %

Predictions for p+p+Pb Collisions at sNN=5\sqrt{s_{NN}} = 5 TeV: Comparison with Data

Predictions made in Albacete {\it et al} prior to the LHC $p+$Pb run at $\sqrt{s_{NN}} = 5$ TeV are compared to currently available data. Some predictions shown here have been updated by including the same experimental cuts as the data. Some additional predictions are also presented, especially for quarkonia, that were provided to the experiments before the data were made public but were too late for the original publication are also shown here.Comment: 55 pages 35 figure

Heavy-flavour and quarkonium production in the LHC era: from proton-proton to heavy-ion collisions

This report reviews the study of open heavy-flavour and quarkonium production in high-energy hadronic collisions, as tools to investigate fundamental aspects of Quantum Chromodynamics, from the proton and nucleus structure at high energy to deconfinement and the properties of the Quark-Gluon Plasma. Emphasis is given to the lessons learnt from LHC Run 1 results, which are reviewed in a global picture with the results from SPS and RHIC at lower energies, as well as to the questions to be addressed in the future. The report covers heavy flavour and quarkonium production in proton-proton, proton-nucleus and nucleus-nucleus collisions. This includes discussion of the effects of hot and cold strongly interacting matter, quarkonium photo-production in nucleus-nucleus collisions and perspectives on the study of heavy flavour and quarkonium with upgrades of existing experiments and new experiments. The report results from the activity of the SaporeGravis network of the I3 Hadron Physics programme of the European Union 7th Framework Programme