Uncertainties of Parton Distributions (II) Results Sept 2003 PHYSTAT

Estimate the uncertainty on the predicted cross section for ppbar  W+X at the Tevatron collider. global c2 local c2’s Sept 2003 PHYSTAT

Each experiment defines a “prediction” and a “range”. This figure shows the Dc2 = 1 ranges. Sept 2003 PHYSTAT

This figure shows broader ranges for each experiment based on the “90% confidence level” (cumulative distribution function of the rescaled c2). Sept 2003 PHYSTAT

The final result is an uncertainty range for the prediction of sW. Survey of swBln predictions (by R. Thorne) … PDF set energy swBln [nb] PDF uncert Alekhin Tevatron 2.73  0.05 MRST2002 2.59  0.03 CTEQ6 2.54  0.10 LHC 215.  6. 204.  4. 205.  8. Sept 2003 PHYSTAT

How well can we determine the value of aS( MZ ) from Global Analysis? For each value of aS, find the best global fit. Then look at the c2 value for each experiment as a function of aS. Sept 2003 PHYSTAT

Each experiment defines a “prediction” and a “range”. This figure shows the Dc2 = 1 ranges. Particle data group (shaded strip) is 0.1170.002. The fluctuations are larger than expected for normal statistics. The vertical lines have Dc2global=100, as(MZ)=0.11650.0065 Sept 2003 PHYSTAT

Gluon and U quark at Q2 = 10 GeV2. Uncertainties of the PDF’s themselves (only interesting to the model builders) Gluon and U quark at Q2 = 10 GeV2. Sept 2003 PHYSTAT

Comparing “alternate sets” red – CTEQ6.1 blue – Fermi2002 (H1, BCDMS, E665) Gluon at Q2 = 10 GeV2 U quark at Q2 = 10 GeV2 Sept 2003 PHYSTAT

CTEQ error band with MRST2002 superimposed Q2 = 10 GeV2 Sept 2003 PHYSTAT

Uncertainties of LHC parton-parton luminosities Provides simple estimates of PDF uncertainties at the LHC. Sept 2003 PHYSTAT