PDF fitting to the HERA average data Various comparisons AMCS- January 29 th 2008
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Transcript of PDF fitting to the HERA average data Various comparisons AMCS- January 29 th 2008
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PDF fitting to the HERA average dataVarious comparisonsAMCS- January 29th 2008 Compare ZEUS-JETS/ inbetween/ H1 parametrizations Compare starting Q2: Q02 = 4/ Q02 = 2 GeV2 Compare massless/ massive variable flavour schemes for heavy quark treatment Compare methods of error treatment in 2: Quadratic/ Hessian/ Offset
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ZEUS-Jets Parametrization in between H1 parametrization
First compare different parametrizations:ZEUS-JETS, inbetween and H1 (hopefully Joel has defined these!) in terms of uv, dv, Sea, GlueThis page Q2=4 GeV2 other Q2 values in EXTRASCentral values are really very similar- quite remarkable since ZEUS and H1 parametrizations are not- however the size of errors differs, with in between being the most conservative
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ZEUS-Jets Parametrization in between H1 parametrization
Now in terms of U, D, Ubar, DbarThis page Q2=4 GeV2 other Q2 values in EXTRAS
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ZEUS-Jets Parametrization in between H1 parametrization
xubarxdbarxcbarxsbarNow in terms of ubar, dbar, sbar, cbarThis page Q2=4 GeV2 other Q2 values in EXTRASThe similarity of these is perhaps even more remarkable given the different treatment of charm- clearly the fixed fraction fc=0.15 is about right compared to dynamical turn on at Q2=mc2
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ZEUS-Jets Parametrization in between H1 parametrization
Finally in terms of d/u and dbar-ubarHere we do see a difference in central values. I like the fact that in-between reflects the fact that we dont know anything!This page Q2=4 GeV2 other Q2 values in EXTRAS
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Inbetween with Q02=2
Inbetween with Q02=4 Now comparing Q02=4 (standard) with Q02=2=mc2 for the inbetween parametrizationIn the latter case the fixed fraction fc=0.0 rather than fc=0.15. One can thus make it fully consistent with dynamical generation.Starting at a different Q0 is equivalent to a different parametrization. It will be necessary if we are ever to move to NNLO- it makes charm treatment more rational.Central values fairly similar (d-valence?) error estimates smaller for Q02=2
uv,dv,Sea, gluonThis page Q2=4 GeV2
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Now U,D,Ubar,Dbar This page Q2=4
Inbetween with Q02=4Inbetween with Q02=2
.Central values similar error estimates smaller for Q02=2
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ubar, dbar, sbar, cbar This page Q2=4
Inbetween with Q02=4Inbetween with Q02=2
.Central values similar (high-x dbar?) error estimates smaller for Q02=2
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Now d/u and dbar-ubar This page Q2=4.Error estimates smaller for Q02=2
Inbetween with Q02=4Inbetween with Q02=2
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Return to the standard Q02=4. Stick with inbetween. Compare dynamical generation of charm zero-mass (ZMVFN) with massive dynamical generation a la Thorne (RTVFN) uv,dv,Sea glueZMVFNRTFVNuv,dv,Sea, gluonThis page Q2=4 GeV2Other Q2 in EXTRASCentral values similar. Errors fairly similar- larger at low-x for RTVFN
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ZMVFNRTFVN U,D,Ubar,DbarThis page Q2=4 GeV2
Central values reflect the fact that charm turns on more slowly- hence less U and Ubar at low-x. Errors slightly larger for RTVFN
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RTFVN has a slow turn on of charm the other sea quarks try to compensate to make a similar total SeaZMVFNubar,dbar,sbar,cbarubar,dbar,sbar,cbarThis page Q2=4 GeV2 Q2 =10 next pageRTFVN
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ubar,dbar,sbar,cbarThis page Q2=10 GeV2ZMVFNRTFVN RTFVN has a slow turn on of charm still hasnt quite caught up at Q2=10.
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ZMVFNdbar-ubar and d/u at Q2=4RTFVN No differences worth remarking on
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Now compare methods of treating errors: Quadratic/Hessian/Offset (back to standard fit ZMVFN and ZEUS-JETS parametrization)QuadraticHessianOffset procedural errors- rest quadraticuv,dv,Sea,gluonThis page Q2=4 GeV2Other Q2 in EXTRASCentral values very similar (not obvious for Hessian) Errors generally largest for OFFSET procedural (high-x dv?), but not much difference compared to using ZEUS data alone- systematic errors not so big now
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Offset just procedural errorsOffset 27 of the 47 total errors (MINUIT limitations!) procedural are not included hereuv,dv,Sea, gluonThis page Q2=4 GeV2Other Q2 in EXTRASProcedural seem to be the most significant
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HessianQuadraticOffset proceduralU,D,Ubar,DbarThis page Q2=4 GeV2Other Q2 in EXTRASCentral values very similar (not obvious for Hessian) Errors generally largest for OFFSET procedural (high-x D?), but not much difference compared to using ZEUS data alone- systematic errors not so big now
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QuadraticHessianOffset proceduralubar,dbar,sbar,cbarThis page Q2=4 GeV2Other Q2 in EXTRASCentral values very similar (not obvious for Hessian) Errors generally largest for OFFSET procedural, but not much difference compared to using ZEUS data alone- systematic errors not so big now
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Conclusions/ to doGo with some sort of inbetween parametrizationMove to Q02=2 and RTVFNUse latest data set!Use either Hessian or OFFSET not quadratic I favour OFFSET but offsetting all 47 is a pain (even when minuit cooperates). Offsetting the 4 procedural seems the most important. Hessian method does seem to reproduce similar size errors and is more straightforward - ideas?Agree with Joel on these alternative fits
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EXTRAS
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ZEUS-Jets Parametrization in between H1 parametrization
Q2=10 GeV2in terms of uv, dv, Sea, Glue
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ZEUS-Jets Parametrization in between H1 parametrization
Q2=1 GeV2in terms of uv, dv, Sea, Glue
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ZEUS-Jets Parametrization in between H1 parametrization
Q2=10 GeV2Now in terms of U, D, Ubar, Dbar
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ZEUS-Jets Parametrization in between H1 parametrization
xubarxdbarNow in terms of ubar, dbar, sbar, cbarQ2= 10 GeV2xcbarxsbar
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ZEUS-Jets Parametrization in between H1 parametrization
xdbarxubarQ2= 1 GeV2xsbarxcbarNow in terms of ubar, dbar, sbar, cbar
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ZEUS-Jets Parametrization in between H1 parametrization
xubarxdbarThis page is all for Q2=1.8225= mc2, not for Q2=1xsbarxcbarNow in terms of ubar, dbar, sbar, cbar
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Q2= 10 GeV2Finally in terms of d/u and dbar-ubar
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uv,dv,Sea, gluonThis page Q2=10GeV2Inbetween with Q02=4Inbetween with Q02=2
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Inbetween with Q02=4Inbetween with Q02=2uv,dv,Sea, gluonThis page Q2=1GeV2
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ZMVFNRTFVN thompsonuv,dv,Sea, gluonThis page Q2=10 GeV2
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ZMVFNRTFVN uv,dv,Sea, gluonThis page Q2=1 GeV2
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Offset just procedural errorsOffset 27 of the 47 total errors (MINUIT limitations!) procedural are not included hereU,D,Ubar,DbarThis page Q2=4 GeV2Other Q2 in EXTRASProcedural seem to be the most significant
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Offset 27 of the 47 total errors (MINUIT limitations!) procedural are not included hereOffset just procedural errorsProcedural seem to be the most significantUbar,dbar,sbar,cbarThis page Q2=4 GeV2Other Q2 in EXTRAS
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QuadraticHessianOffset proceduralOffset 27uv,dv,Sea, gluonThis page Q2=10GeV2
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QuadraticHessianOffset 27uv,dv,Sea, gluonThis page Q2=1GeV2
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HessianQuadraticOffset proceduralOffset 27U,D,Ubar,DbarThis page Q2=10GeV2
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QuadraticHessianOffset proceduralOffset 27ubar,dbar,sbar.cbarThis page Q2=10GeV2
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HessianQuadraticOffset 27d/u and dbar-ubarThis page Q2=4 GeV2Other Q2 in EXTRASCentral values very similar (not obvious for Hessian) Errors generally largest for OFFSET procedural, but not much difference compared to using ZEUS data alone- systematic errors not so big now
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QuadraticHessianOffset 27d/u and dbar-ubarThis page Q2=4 GeV2Other Q2 in EXTRAS