Estabilidade da resistência à brusone, mancha-parda, escaldadura e mancha-estreita nas folhas de arroz.

Foi estudada a estabilidade de resistência de 20 cultivares/linhagens de arroz a quatro doenças foliares

Low mass dimuon production in proton and ion induced interactions at SPS

The low mass dimuon spectra collected in $p$-U collisions by the NA38 experiment significantly exceeds the total cross section expected from previous analysis, done by other experiments. The 'excess' events have a harder $p_{T}$ distribution than the muon pairs from $\eta$ and $\omega$ Dalitz decays, expected to dominate the mass window 0.4—0.65~GeV/$c^2$. We conjecture that the excess events might be due to $q\bar{q}$ annihilations, negligible at low $p_{T}$ but made visible by the $m_{T}$ cut applied in the NA38 data. Taking this assumption to parametrise the $p$-U spectra, we proceed with the analysis of the S-Cu, S-U and Pb-Pb data, collected by the NA38 and NA50 experiments, where we find that the measured mass spectra does not seem to exceed the expected low mass `cocktail' by more than 20%

Low mass dimuon production in proton and ion induced interactions at SPS

The low mass dimuon spectra collected in p-U collisions by the NA38 experiment significantly exceeds the total cross section expected from previous analysis, done by other experiments. The `excess' events have a harder \pt\ distribution than the muon pairs from $\eta$ and $\omega$ Dalitz decays, expected to dominate the mass window 0.4--0.65~GeV/$c^2$. We conjecture that the excess events might be due to \qqbar\ annihilations, negligible at low \pt\ but made visible by the \mt\ cut applied in the NA38 data. Taking this assumption to parametrise the p-U spectra, we proceed with the analysis of the S-Cu, S-U and Pb-Pb data, collected by the NA38 and NA50 experiments, where we find that the measured mass spectra does not seem to exceed the expected low mass `cocktail' by more than 20\,\%

Results on Charmonium States in Pb-Pb Interactions

We present cross-sections for J/$\psi$, $\psi^{\prime}$ and Drell-Yan production in lead-lead interactions at 158 GeV/nucleon. The Pb-Pb data, when compared with previous results obtained with lighter target or projectiles, show a similar behaviour for Drell-Yan, but exhibit an anomalous J/$\psi$ suppression, which increases with centrality

Intermediate mass dimuons in NA38/NA50

The NA38/NA50 experiments have measured, at the CERN SPS, the dimuon production in proton-nucleus and nucleus-nucleus collisions. In this paper it is shown that the mass continuum between the $\phi$ and the $J/{\psi}$ can be satisfactorily described, after having removed the combinatorial background due to uncorrelated $\pi$ and $K$ decays, as a sum of two contributions, namely the Drell-Yan process and the semi-leptonic decay of pairs of charmed mesons, whose mass shape in the acceptance of the experiment has been evaluated using PYTHIA. However, in order to describe the A - B (namely S - U and Pb - Pb) mass spectra, the dimuon yield from open charm decays, which in $p$ - A collisions is found to be consistent with direct open charm measurements from other CERN and FNAL experiments, has to be enhanced with respect to a linear extrapolation of $p$ - A results. The size of the enhancement smoothly increases from peripheral S - U to central Pb - Pb interactions, reaching a factor $\sim$ 3 in central Pb - Pb collisions. The $P_{T}$ distributions of the events in the mass continuum are also compatible with the hypothesis of open charm enhancement in A - B collisions