RESUMO
We report on a precision measurement of the parity-violating asymmetry in fixed target electron-electron (Møller) scattering: A(PV) = [-131 +/- 14(stat) +/- 10(syst)] x 10(-9), leading to the determination of the weak mixing angle sin2(thetaW(eff) = 0.2397 +/- 0.0010(stat) +/- 0.0008(syst), evaluated at Q2 = 0.026 GeV2. Combining this result with the measurements of sin2(thetaW(eff) at the Z0 pole, the running of the weak mixing angle is observed with over 6sigma significance. The measurement sets constraints on new physics effects at the TeV scale.
RESUMO
We report a measurement of the parity-violating asymmetry in fixed target electron-electron (Møller) scattering: A(PV)=[-175+/-30(stat)+/-20(syst)] x 10(-9). This first direct observation of parity nonconservation in Møller scattering leads to a measurement of the electron's weak charge at low energy Q(e)(W)=-0.053+/-0.011. This is consistent with the standard model expectation at the current level of precision: sin((2)theta(W)(M(Z))((-)MS)=0.2293+/-0.0024(stat)+/-0.0016(syst)+/-0.0006(theory).
RESUMO
Phenyl-substituted analogues of 2-[(phenylmethyl)sulfonyl]pyridine 1-oxide preemergent herbicides were examined in order to determine quantitative relationships between structure and activity against the following three weed species: switch grass (Panicum virgatum L.), barnyard grass (Echinochloa crusgalli L. Beauv.), and green foxtail (Setaria viridis L. Beauv.). Analogues were chosen to provide maximum parameter orthogonality. Regression analysis yielded structure-activity relationships wherein the most significant substituent parameters associated with herbicidal activity were found to be the partition coefficient (pi), the molar refractivity (MR), and two indicator variables, Z (denoting the presence of an alpha-methyl group) and H (denoting an ortho substituent capable of hydrogen bonding). For green foxtail, the structure-activity relationship was found to be: -log ED50 = 0.43 pi -0.052MR + 0.50H + 0.24Z + 0.61, where ED50 is expressed in moles per acre. The regression equations were found to explain 79-93% of the bioactivity for the three weed species studied. It was further shown that these equations represent the best possible correlations within the limitations of the biological data.