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Flavour break-up July9th 2008

Flavour break-up July9th 2008. We have decided to use non-dynamic WITH fc=0.15 ± 0.03 for fc model dependence fc=0 at Q20=2 and fc=0.22 at Q20=6 fc=0.13 at mc=1.5 and fc=0.18 at mc=1.35 After having looked compared charm fractions and intercepts in dynamic and non-dynamic jobs.

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Flavour break-up July9th 2008

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  1. Flavour break-up July9th 2008 We have decided to use non-dynamic WITH fc=0.15 ± 0.03 for fc model dependence fc=0 at Q20=2 and fc=0.22 at Q20=6 fc=0.13 at mc=1.5 and fc=0.18 at mc=1.35 After having looked compared charm fractions and intercepts in dynamic and non-dynamic jobs. This means many things remain as they were for DIS08 Only the fc,Q20 and mc model dependences can be different. Nothing we have shown the world looks different

  2. We did not actually show the world how our six model uncertainties affect the uncertainty separately But I have shown it in these meetings, so I did it again with the new fc settings First I looked at uv,dv, Sea, glue and U,D, Ubar Dbar There is NO DIFFERENCE for: mb, fs, Q2min Or for mc: – these model uncertainties are so small that the fact that fc is now changing with mc just doesn’t show up There is a small difference for fc itself which only shows up on the U,D,Ubar,Dbar plot There is also a small difference for Q20, which shows up on the U,D,Ubar Dbar plot….. These two small differences are shown below, the rest are in a file which I sent to Joel.

  3. NEW OLD Include only variation of charm fraction fc: 0.10 →0.20 OLD 0.12 → 0.18 NEW This model dependence is smaller now as it should be! If you look at flavour break-up U/D you can see that the fc matters less than it did..make a tif file?

  4. NEW OLD Include only variation of starting scale Q02: 2 → 6 GeV2 Has a small asymmetric effect on PDF ucertainties NEW has smaller model dependence than old- this is also as expected

  5. Now consider flavour break-up ubar,dbar cbar, sbar Clearly this is going to be more dependent on our assumptions Remember we have not yet shown this to the world First we ‘ll look at the total model dependence with all model uncertainty Then at break up of this into the 6 different sources

  6. All 6 sources OLD NEW Now there really IS a big new/old difference ..where does it come from in detail? (don’t bother looking at the blue lines- that’s another story)

  7. NEW OLD Old had mb and mc New haS JUST mc.. it is no longer true that changing mc gives no model dependence! This makes sense. We now change the amount of charm with mc- this is a new source of model error

  8. Variation of fc NEW OLD Variation of fc is now smaller OLD: 0.15 ± 0.05 NEW: 0.15 ± 0.03

  9. Change of Q20 NEW OLD Change of Q20 used to affect the flavour break up a lot because fs and fc were not changed accordingly. Now that fs anf fc are changed with Q20, the change of Q20 itself is not a big effect.

  10. The predictions for W and Z do not look very different but have benefited from a decrease in model errors from varying fc with Q20 So what I showed the world was conservative.

  11. NEW plus 6 model errors OLD plus 6 model errors

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