1. Calculations of Higgs x-sections at NkLO
ATL-COM-PHYS
A.-C. Bourgaux, M. Escalier, L. Fayard

2. Tools and parameters used
Anastasiou
Tools: FEHiP, HggTotal, HNNLO, HqT
Factorisation (µF) and renormalisation (µR) scales :
mF= mR in [mH/2 ; 2mH ] to limit computations (study in appendix)
Pdf: mstw2008, (mrst 2004 for HqT) (study in appendix)
default parameters used, while waiting for a common prescription:
mt = GeV for FEHiP,
178 GeV for HNNLO (study in appendix)

3. Total x-sections (100-800 GeV)
• HNNLO mt  ∞
No correction
• FEHiP
mt  ∞ + correction:
Opening of the on-shell phase-space
Result table, approx of ∞ mass t; b  appendix

4. Total x-sections with HggTotal
Available :
Good agreement with calculations by De Florian and Grazzini, with a different choice for mR and mF.
Anastasiou : arXiv: , arXiv:hep-ph/
"We present results for the Higgs boson cross section accounting for these effects. We account for the effect of soft-gluon resummation at the Tevatron by presenting values for the scale choice µF = µR = MH /2, which is known to very accurately reproduce the reference value of the resummation result [21] for a wide range of Higgs boson masses, and provide an estimate of the remaining theoretical uncertainties arising from unknown higher-order terms and PDF errors."

6. x-sections*BR with HNNLO
s × Br(H  gg)
Br(H  gg)
(Br tables of HNNLO seem to be computed from Hdecay)

7. differential x-sections with HNNLO
5 (jet) 1 3 H 4
6 (jet) 2
gg fusion Higgs 2 photons γ
LO _ pT34 pT3 &pT4
y34 η3 & η4
NLO pT5 pT34 pT3 &pT4
NNLO pT5 pT34 pT3 & pT4
pT6 y34 η3 & η4

8. ATL-COM-PHYS-2009-161 Qian, Liu, Mansoulie, Purdham, Strandberg, Thun
photon g
mH=100 GeV
mH=800 GeV
For high masses, the photon is more central
normalized:
stable observable / pert order
mH=100 GeV
ATL-COM-PHYS Qian, Liu, Mansoulie, Purdham, Strandberg, Thun

9. photon g mH=100 GeV fixed order calculation : LO bounded at pt=mH/2
 NLO and NNLO unstables in this region
normalized:
ATL-COM-PHYS

10. Higgs mH=100 GeV mH=800 GeV normalized: stable observable / pert order
ATL-COM-PHYS
Detector acceptance will limit the rapidity range that can be measured

11. Higgs compatible with statistical error mH=100 GeV
ATL-COM-PHYS

12. PT of Higgs : HqT Construction of the curve :
Resummed : divergent terms only « resummed »=exp(Sudakov factor)
Asymptotic : limit of perturbative order when PT0 : divergent terms only
Fix order : all perturbative developpement terms, including divergent terms
Matched = Resummed + Fix order - Asymptotic

13. Higgs PT, @ LO and NLO mH=125 GeV Normalized : ≠ from HNNLO
Correction to pT(H) : appendix

14. resummation for low pT fix order for high pT
HqT
HNNLO

15. Influence of mR , mF at LO
linear scale:
log scale:
with normalization:

16. Influence of mR , mF at NLO (1)
linear scale:
log scale:
with normalization:

17. Influence of mR , mF at NLO (2)
For high pT :
dependance on scales remains almost constant : calculation is actually LO
For low pT :
dependance on scales decreases between LO and NLO
NLO
mH/2

18. Influence of resummation scale mRS at LO (1)
mRS=mH
Matched calculation is closer to fix order when resumation scale is lower

19. Influence of mRS at LO (2)
linear scale:
log scale:
with normalization:

20. Influence of mRS at NLO (1)
Resumation scale influence is lower at NLO

21. Influence of mRS at NLO (2)
linear scale:
log scale:
with normalization:

22. Acceptances with FEHiP, PYTHIA and MC@NLO

23. Appendix

25. Approximation of infinity mass of t ; b
Plot from Frank Petriello
?!?

26. Influence of µF µR Major effect: σ decreases with µR
maximum
central value
minimum
mH=120 GeV
mH=190 GeV mF
0.5 1 2 mR
14.7
15.02
15.10
5.98
5.87
5.71
11.8
12.02
12.10
4.86
4.77
4.64
9.62
9.84
9.91
4.03
3.95
3.85
Influence of µF µR
Major effect: σ decreases with µR
Minor effect: σ increases or decreases with µF
depending on mass
@ LO (same observations at NLO…), using mrst2001
Complete study in appendix

27. Influence of mt FEHiP mt  ∞ HNNLO + correction:
mt  ∞ without correction
mt : little influence
HNNLO and FEHiP differences due to F(mt)

28. Our results with FEHiP:
Influence of pdf
Our results with FEHiP:
mrst mstw2008
+14%
LO, 100 GeV: 17, ,467
+6%
NLO, 100 GeV 31, ,005
With HNNLO:
mrst mstw2008
+13%
LO, 100 GeV 16, ,704
+8%
LO, 200 GeV 3, ,937
Results compatible with:
Martin,Stirling,Thorne,Watt, arXiv: v2
+10%

29. Check of constistency:
2 equivalent photons ?
(no cuts applied at generation)
m=100 GeV

30. What is the uncertainty on PT(H)?
Balazs, Grazzini, Huston, Kulesza,Puljak arXiv:hep-ph/ v1

31. Corrections to pT(H) Finite top quark mass ; Bottom quark contribution
Keung, Petriello, hep-ph
Finite top quark mass ; Bottom quark contribution
LHC :
30 ≤PT≤50 GeV : -4 %
50≤PT≤150 : %
PT~300 GeV : -30 %

32. EW gauge boson terms (W, Z)
Keung, Petriello, hep-ph
EW gauge boson terms (W, Z)
LHC :
100≤PT≤300 GeV : -3 %

33. Prescription used for ATL-COM-PHYS-2007-024
Should we use same prescription ? Arguments for prescription ?

34. EW corrections 2-loop EW corrections for Hgg :
eg of production corrections
eg of decay corrections

35. -top quark contributions : ~15 % of light contribution
Degrassi, Maltoni, hep-ph/
Total : 5-8 % correction
contrib. of top

36. -light fermions contributions
Aglietti, Bonciani, Degrassi, Vicini,
hep-ph/
production
decay
QCD
total EW
(no top correction)
9 % to LO
up to –10 % correction