ZEUS fits-report: FL session Feb 2009 A.M.Cooper-Sarkar and C. Gwenlan. Report on fitting new FINAL data: e- CC (175pb -1 : P=0.30 71pb -1 , P=-0.27 104pb -1 ) (DESY-08-177) e- NC (169pb -1 , P=+0.29, P=-0.27) (DESY-08-202)
A.M.Cooper-Sarkar and C. Gwenlan
This takes 509 data points up to 760 data points
Remember we have shown this before with preliminary e- data- this is now final
PDFs from the new fit compared to published
ZEUS-JETS fit – central values of the PDFs do not change much…..
The d-flavour sector is less well known- hence we look forward to CCe+ data
The xuv PDF uncertainties are reduced at high-x ….. as expected since NC and CC e- cross-sections are both u dominated
However some other uncertainties increase marginally- this can always happen when OFFSETing correlated errors
This takes 760 data points up to 922 data points
PDFs from the new fit compared to the ZEUS-pol fit (showing just impact of HER,MER,LER data) – central values of the PDFs do not change much….
All systematics added in quadrature (i.e. no treatment for correlations) impact of LER,MER,HER data on low-x sea and low-x gluon is clearly visible
However using the OFFSET method to account for correlated systematic errors this is less clear. The new HER,MER, LER data reduce the uncertainties on the low-x sea- as expected since this is the kinematic region of the data and the data relate DIRECTLY to the sea.
The relationship of the gluon is less direct - Gluon uncertainty at very low x is reduced, but uncertainty band wider at higher x