NNLO HERAPDF1.0? H1/ZEUS fitters meeting Jan 26 th 2010 AMC-S

1. NNLO HERAPDF1.0?H1/ZEUS fitters meeting Jan 26th 2010AMC-S

2. HERAPDF1.0 at NNLO • We have already agreed results for the central values at two αS(MZ) values: 0.1145 which is preferred by the fit and the standard 0.1176 NOTE that NNLO PDFs are supposed to look different from NLO: gluon evolution is slower whereas sea evolution is faster. This is illustrated by showing Q2=2 and Q2=10 so one can see that the larger low-x gluon at Q2=2 (for alphas=0.1145) DOES NOT evolve into a much larger gluon at Q2=10 – But the Sea PDF does evolve more.

3. In the PDF4LHC community there is now an underlying drive to move to NNLO • there is a large uncertainty in the heavy quark treatment at NLO • -These discrepancies are smaller at NNLO and it is agreed that the community should move in this direction • Theoreticians are making predictions at NNLO and will only use NNLO PDFs (e.g. Catani et al arxiv: 1002.3115) this means that they are using MSTW08 and ABKM and GJR rather than CTEQ66/NNPDF- it is clear that having an NNLO set can give greater visibility • So I have run the NNLO fit for αS(MZ) =0.1145 for all the model and parametrisation variations • NOTE: • Model variations much as before BUT Q2min > 5 a bit more significant • Parametrisation variations: i)Q20=1.5 + negative gluon term is more significant • ii) Bdv≠ Buv more significant • iii) DUbar ≠ 0, DDbar ≠ 0 become insignificant • iv) Duv ≠ 0 is less significant NNLO HERAPDF1.0

4. The shape variation of d_v is mostly down to Bdv ≠ Buv This is due to a stronger negative gluon term

5. NNLO NLO The greater width of the yellow bands is due to Q2min=5 cut The shape variation of d_v is mostly down to Bdv≠Buv This is due to a stronger negative gluon term

6. Sensitivity to the parametrisation Follow the usual procedure – return to 9 PDF parameters 10th param chisq a I have retrieved a few of the 9 parameters + one at a time jobs These are the ones that have ever made any difference— the DUbar,DDbar,DDv have never been important at this atge Our usual 10th parameter Euv is the best choice

7. And starting with our usual parametrisation I have retrieved some of the important variations NLO has 574/582=0.98 NLO has 511/556=0.92 and no big shape change 3.5 to 5

8. NNLO cross-checks to Voica Alpha_s=0.1145 chisq=623.7 Voica 621.9 Buv        0.80434       0.29045E-01           Cuv         4.6748       0.15963   Euv         6.8983        1.5455          Cdv         3.7873       0.24843             ADbar      0.23742       0.94999E-02          BDbar     -0.13109       0.50767E-02               CUbar       7.2478       0.72054   CDbar       4.6805       0.99849          Bg         0.98402E-01   0.22316E-   Cg          8.2939       0.60679       Buv 0.803493854 0.028409602 Cuv 4.66702624 0.158989171 Euv 6.8648385 1.52593798 Cdv 3.78576767 0.246948783 ADbar 0.23571 0.009246213 BDbar -0.132146295 0.00498902822 CUbar 7.20525693 0.708651104 CDbar 4.64765555 0.970524693 Bg 0.102284448 0.0222984419 Cg 8.33672271 0.601400488 Alphas=0.1176 chisq=638.3 Voica 636.3  Buv        0.86171       0.23412E-01         Cuv         4.5953       0.16458    Euv         5.7522        1.3747           Cdv         3.8235       0.21896             ADbar      0.26120       0.88901E-02         BDbar     -0.11967       0.44277E-02             CUbar       9.4858       0.70083      CDbar       4.8932       0.83099            Bg         0.13663       0.24780E-01             Cg          6.9707       0.52585 Buv 0.860567384 0.0234952116 Cuv 4.59396084 0.168363544 Euv 5.778106 1.36545351 Cdv 3.8125908 0.230886994 ADbar 0.25686 0.009623 BDbar -0.121103638 0.00482499241 CUbar 9.41256469 0.718575901 CDbar 4.89010829 1.02883157 Bg 0.142760628 0.0252330946 Cg 7.01748255 0.594072802

9. Variations for alpha_s=0.1145 Q2>5 Chisq=535.7 Voica 534 Buv 0.737846811 0.0376851683 Cuv 4.70101564 0.144694628 Euv 8.98782954 1.84885886 Cdv 3.71919318 0.304912115 ADbar 0.2302353 0.0144872 BDbar -0.127821207 0.00894921063 CUbar 5.77891039 0.88565066 CDbar 3.80712724 0.883081754 Bg 0.0694983119 0.028270994 Cg 8.4448627 0.671635174 Buv        0.73810       0.38608E-01             Cuv         4.7085       0.14372 Euv         9.0454        1.8595                  Cdv         3.7195       0.31609             ADbar      0.23135       0.14651E-01             BDbar     -0.12717       0.89702E-02 CUbar       5.8010       0.90184                  CDbar       3.8222       0.93516              Bg     0.66989E-01   0.28187E-01          Cg          8.4219       0.68706       Bdv.ne.Buv Chisq=619.8 Voica 617.9  Buv        0.80488       0.26924E-01             Cuv         4.6255       0.15540 Euv         6.8059        1.5238    Bdv         1.0749       0.13217       Cdv         4.7848       0.56859             Adbar      0.24552       0.96894E-02             Bdbar     -0.12712       0.50777E-02                       CUbar       7.2628       0.69045    CDbar       8.0111        2.7948 Bg         0.83155E-01   0.23503E-01          Cg          7.4040       0.68866            0.803624474 0.0262193875 4.62203842 0.155552658 6.81104917 1.51427551 1.0639416 0.0719670411 4.7427327 0.375572608 0.2431588 0.007255562 -0.128492536 0.00393168647 7.22572511 0.683576039 7.72553066 1.05739964 0.0883410173 0.0201980778 7.50122243 0.411532943

10. Voica agrees on the effect of Bdv.ne.Buv Voica agrees on the effect of change in alphas Voica agrees on the effect of the Q2cut > 5 Voica agrees on the effect of the negative gluon term Voica has found a relatively strong difference with ACOT

11. So do we release it? With the same settings as HERAPDf1.0? IF SO… There is an argument for going back to alphas=0.1176 (The variations I have shown are for alphas=0.1145)

12. extras