W predictions at LHC using the H1-ZEUS combined fit
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W predictions at LHC using the H1-ZEUS combined fit. W  e cross-sections at LHC calculated at NLO with MCFM. Goal : look at how the uncertainties are reduced with the DIS’08 combined fit, comparisons with Mandy. Cuts: P T,e > 25 GeV |  e | < 3

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W predictions at LHC using the H1-ZEUS combined fit

W  e cross-sections at LHC calculated at NLO with MCFM.

Goal : look at how the uncertainties are reduced with the DIS’08 combined fit,

comparisons with Mandy.

Cuts: PT,e > 25 GeV

| e | < 3

R (j, e) > 0.7 if real emission

Use the MCFM interface to LHAPDF to calculate the predictions with

various fits :

- CTEQ 6.1

- H1pdf2k

- ZEUS 2002 ZM but some jobs crashed

- H1ZEUS DIS’08 (I first put the fit results into a LHgrid file).

14 May 08


Differential cross-sections

  • H1ZEUS gives larger cross-section than CTEQ 6.1

  • Note the much smaller uncertainty (see later)

  • Calculations with CTEQ 6.1 : differences between my xs and Mandy’s xs :

  • due to the R cut that I have in the MCFM calculations.

  • Without this cut, my total xsection is ~ 15% higher.

14 May 08


CTEQ 6.1, Mandy vs. mine : different shape at high eta.

To be checked with MCFM without the R cut.

14 May 08


Relative uncertainties of W predictions

My errors: sym.

formula, i.e.

(up – down) / 2.

  • Fit uncertainty : large reduction with H1ZEUS, compared with H1pdf2k.

  • Full uncertainty : yellow hist = mine - the 6 model variations.

  • black dashed = Mandy’s - vary Q20 (largely dominant)

  • Many and I get the same rel. uncertainty.

  • Much smaller than the error obtained from CTEQ 6.1

14 May 08



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