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

AMC-S

HERAPDF1.0 at NNLOWe 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.

1. In the PDF4LHC community there is now an underlying drive to move to NNLO

2. there is a large uncertainty in the heavy quark treatment at NLO

3. -These discrepancies are smaller at NNLO and it is agreed that the community should move in this direction

4. 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

This is due to a stronger negative gluon term

The shape variation of d_v is mostly down to Bdv ≠ Buv

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

Sensitivity to the parametrisation

Follow the usual procedure – return to 9 PDF parameters

10th param chisq a

+none 645.9

+Euv 623.7

+Duv 637.6

+Dg 644.8

+Bdv 640.7

Our usual 10th parameter Euv is the best choice

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

variation a_s=0.1145 a_s=0.1176

Standard Q2>3.5

623.7/582=1.07 638.3/582=1.10

Q2>2.5 655.4/598=1.10

Q2> 5

Q2> 7

535.7/556=0.96

491.1/540=0.91

No big shape change 5 to 7

10+Bdv 619.8

10+Duv 620.4

10+DUbar 623.7

10+DDbar 623.7

10+Dg 623.7

NLO has 574/582=0.98

NLO has 511/556=0.92

and no big shape change 3.5 to 5

And starting with our usual parametrisation I have retrieved some of the important variations

NNLO cross-checks to Voica

Alpha_s=0.1145 chisq=623.7 Voica 621.9

Buv 0.803493854 0.028409602 Cuv 4.66702624 0.158989171 Euv 6.8648385 1.52593798Cdv 3.78576767 0.246948783ADbar 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

   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      

Alphas=0.1176 chisq=638.3 Voica 636.3

Buv 0.860567384 0.0234952116 Cuv 4.59396084 0.168363544 Euv 5.778106 1.36545351Cdv 3.8125908 0.230886994ADbar 0.25686 0.009623 BDbar -0.121103638 0.00482499241 CUbar 9.41256469 0.718575901 CDbar 4.89010829 1.02883157 Bg 0.142760628 0.0252330946Cg 7.01748255 0.594072802

       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       

Variations for alpha_s=0.1145

Q2>5 Chisq=535.7 Voica 534

Buv 0.737846811 0.0376851683Cuv 4.70101564 0.144694628Euv 8.98782954 1.84885886Cdv 3.71919318 0.304912115ADbar 0.2302353 0.0144872BDbar -0.127821207 0.00894921063CUbar 5.77891039 0.88565066CDbar 3.80712724 0.883081754Bg 0.0694983119 0.028270994Cg 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

0.803624474 0.02621938754.62203842 0.1555526586.81104917 1.51427551

1.0639416 0.07196704114.7427327 0.3755726080.2431588 0.007255562

-0.128492536 0.003931686477.22572511 0.6835760397.72553066 1.05739964

0.0883410173 0.02019807787.50122243 0.411532943

     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           

Voica agrees on the effect of Bdv.ne.Buv

Voica agrees on the effect of the Q2cut > 5

Voica agrees on the effect of the

negative gluon term

Voica agrees on the effect of change in alphas

Voica has found a relatively strong difference

with ACOT

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)

extras