UNDULATOR K-PARAMETER MEASUREMENTS AT LCLS ∗
We report our first in-situ measurements of relative undulator segment K-parameters made at the LCLS. The diagnostics, calibration, procedure, and early results are described. Measurement errors and noise are discussed and the outlook for near-term develop presented.
We describe preliminary results from an effort to quantify the uncertainties in parton distribution functions and the resulting uncertainties in predicted physical quantities. The production cross section of the $W$ boson is given as a first example. Constraints due to the full data sets of the CTEQ global analysis are used in this study. Two complementary approaches, based on the Hessian and the Lagrange multiplier method respectively, are outlined. We discuss issues on obtaining meaningful uncertainty estimates that include the effect of correlated experimental systematic uncertainties and illustrate them with detailed calculations using one set of precision DIS data.