Relativistic Chiral Theory of Nuclear Matter and QCD Constraints

We present a relativistic chiral theory of nuclear matter which includes the effect of confinement. Nuclear binding is obtained with a chiral invariant scalar background field associated with the radial fluctuations of the chiral condensate Nuclear matter stability is ensured once the scalar response of the nucleon depending on the quark confinement mechanism is properly incorporated. All the parameters are fixed or constrained by hadron phenomenology and lattice data. A good description of nuclear saturation is reached, which includes the effect of in-medium pion loops. Asymmetry properties of nuclear matter are also well described once the full rho meson exchange and Fock terms are included.Comment: Talk given by G. Chanfray at PANIC 08, Eilat (Israel), november 10-14, 200

Relation between growth characteristics and yield of barley in different environments

The increasing interest in organic farming has increased the interest in examining the importance of the different growing characteristics, such as attack of diseases, grain weight, lodging and heading date. One of the important questions raised was whether the relationship between the growing characteristics and yield would be the same for conventionally and organically grown crop or would some growing characteristics be more important for organically than for conventionally grown crops. This work will focus on that question. The analyses are performed using two datasets with comparable trials in both conventional and organic grown systems for barley (Hordeum vulgare). The two datasets were from Sweden and Denmark. From Sweden 22 conventional and 22 organic grown trials were available. The trials were laid out at 4 locations in Northern Sweden during the years from 1994-2003. The number of varieties per trial varied between 7 and 15 and 50 varieties were represented. Most of the trials were laid out as split-plot designs with 2 nitrogen levels in the conventional grown trial and 2 seed rates in the organic grown trials. From Denmark 4 conventional and 4 organic grown trials were available. The trials were laid out as a-designs at 2 locations in 2 years (2003 and 2004). The number of varieties per trial varied between 108 and 113 and 146 varieties were represented. The data from each country were analysed in a linear mixed model. The effects of location, year, variety, their interaction and interaction with system were included as random effect. The effect of growing system and growing characteristics were included as fixed effects to see how much of the variation caused by varieties and interaction with varieties that could be explained by the growing characteristic and to se if the effect of the growing characteristics depended on the growing system. The analyses showed that the growing characteristics could explain a considerable part of the variance components for variety or interaction with variety. The effect of some growing characteristics depended significantly on the growing system, but the results varied to some extent between the two countries. In Sweden the effect of volume weight were more important in the conventional grown trials than in the organic grown trials whereas in Denmark grain weight was more important in the organic grown trials than in the conventional grown trials. In Denmark powdery mildew decreased the yield significantly more in conventional grown trials than in organic grown trials. In most cases the other diseases decreased the yield more in the organic grown trials than in the conventional grown trials. In some models the yield in organic grown trials increased as the level of scald attach increased. The results indicated that the effect of a given disease level decreased the yield more in the conventional grown trials than in the organic grown trials – or in some cases increased the yield in the organic grown trial while the yield in conventionally grown trials were increased less or decreased

Scalar response of the nucleon chiral symmetry and nuclear matter properties

In this talk we present a description of nuclear binding in a chiral approach based on the existence of a chiral invariant scalar field associated with the generation of the masses through spontaneous chiral symmetry breaking. We discuss the emergence of such a field on the example of the NJL model. We also incorporate the effect of confinement at the level of the nucleon substructure to stabilize nuclear matter. In a particular quark-diquark model we illustrate the simutaneous influences of spontaneous chiral symmetry breaking and confinement on the nucleon mass and on the nuclear matter description.Comment: Talk given by G. chanfray at "Achievements and New Directions in Subatomic Physics: Workshop in Honour of Tony Thomas' 60th Birthday Adelaide, South Australia. February 15 - February 19, 2010"

QCD susceptibilities and nuclear matter saturation in a chiral theory: inclusion of pion loops

We derive the equation of state of symmetric nuclear matter in a relativistic theory with $\sigma$ and $\omega$ exchange. We take a chiral version of this model which insures all the chiral constraints. Going beyond the mean field approach we introduce the effects of the pion loops. For the parameters of the model, in order to fix those linked to pion exchange, we exploit the most recent information on the short-range part of the spin-isospin interaction. For those linked to the scalar meson exchange we make use of an analysis of lattice results on the nucleon mass evolution with the quark mass. With these inputs we are able reach a correct description of the saturation properties. From the equation of state of symmetric nuclear matter we alsoderive the density dependence of the quark condensate and of the QCD susceptibilities

Neutrino versus antineutrino cross sections and CP violation

We discuss the nuclear interactions of neutrinos versus those of antineutrinos, a relevant comparison for CP violation experiments in the neutrino sector. We consider the MiniBooNE quasielastic-like double differential neutrinos and antineutrinos cross sections which are flux dependent and hence specific to the MiniBooNE set-up. We combine them introducing their sum and their difference. We show that the last combination can bring a general information, which can be exploited in other experiments, on the nuclear matrix elements of the axial vector interference term. Our theoretical model reproduces well the two cross sections combinations. This confirms the need for a sizeable multinucleon component in particular in the interference term

Chiral Symmetry Restoration and Parity Mixing

We derive the expressions of the vector and axial current from a chiral Lagrangian restricted to nucleons and pions. They display mixing terms between the axial and vector currents. We study the modifications in the nuclear medium of the coupling constants of the axial current, namely the pion decay constant and the nucleonic axial one due to the requirements of chiral symmetry. We express the renormalizations in terms of the local scalar pion density. The latter also governs the quark condensate evolu- tion and we discuss the link between this evolution and the renormaliza- tions. In the case of the nucleon axial coupling constant this renormali- zation corresponds to a new type of exchange currents, with two exchanged pions. We give an estimate for the resulting quenching. Although moderate it helps explaining the quenching experimentally observed.Comment: Latex, 15 pages. Several references and one figure added. New discussion of some points has been included. Treatment of the renormali- zation of the nucleon axial coupling constant has been develope

Neutrino energy reconstruction problems and neutrino oscillations

We discuss the accuracy of the usual procedure for neutrino energy reconstruction which is based on the quasielastic kinematics. Our results are described in terms of a probability distribution for a real neutrino energy value. Several factors are responsible of the deviations from the reconstructed value. The main one is the multinucleon component of the neutrino interaction which in the case of Cherenkov detectors enters as a quasielastic cross section, increasing the mean neutrino energy which can differ appreciably from the reconstructed value. As an application we derive, for excess electron events attributed to the conversion of muon neutrinos, the true neutrino energy distribution based on the experimental one which is given in terms of the reconstructed value. The result is a reshaping effect. For MiniBooNE the low energy peak is suppressed and shifted at higher energies, which may influence the interpretation in terms of oscillation. For T2K at the Super Kamiokande far detector the reshaping translates into a narrowing of the energy distribution