Report on fitting new FINAL data:
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Transcript of Report on fitting new FINAL data:
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•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)
•HER(Ep=920,44.5pb-1), MER(Ep=575, 7.1pb-1), LER(Ep=460, 14.0pb-1) reduced cross-sections (DESY-08-666!!!)
•THIS TALK-- Improvement to PDF uncertainties
•On Friday High Q2 talk- Electroweak parameters
•What are we planning before DIS09?- to include NC and CC e+ polarised data
ZEUS fits-report: FL sessionFeb 2009
A.M.Cooper-Sarkar and C. Gwenlan
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PDFs from the new fit compared to published
ZEUS-JETS fit – central values of the PDFs do not change much…..
Adding New NC and CCe- data to ZEUS-JETS fit → ZEUS-pol fit
(NEW)
This takes 509 data points up to 760 data points
(NEW)
Dataset 2/ndp ndp
CC-ve poln. 1.33 37
CC+ve poln. 0.96 34
NC-ve poln. 0.99 90
NC+ve poln. 0.96 90
Quadratic 2
Remember we have shown this before with preliminary e- data- this is now final
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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
The d-flavour sector is less well known- hence we look forward to CCe+ data
(NEW)
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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….
Adding HER, MER, LER data to ZEUS-pol fit → ZEUS-pol-FL fit !
This takes 760 data points up to 922 data points
Dataset 2/ndp ndp
HER 1.09 54
MER 0.69 54
LER 0.84 54
Quadratic 2
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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
Quadratic Errors
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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
Offset method
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Summary/questions
• The new HER, MER, LER data has impact on the fit• I doubt that ZEUS wants to reconsider the use of its
traditional OFFSET method in favour of Hessian or Quadratic at this stage
• But the combination of this with the H1 data could be dramatic