gluon-gluon Fusion Process

Goal of the group

Group Contacts

Daniel de Florian (Buenos Aires U.), Kirill Melnikov (Johns Hopkins U.) Frank Petriello (Northwestern U.), Biagio di Micco (Roma), Giovanni Petrucciani (CERN)

Group Members

Group contact persons plus everybody who wants to contribute

Available Tools

  • ihixs ( C. Anastasiou et al): Program for inclusive Higgs boson cross-section at hadron colliders;
  • HRes ( D. de Florian, G. Ferrera, M. Grazzini, D. Tommasini): Exclusive cross section at QCD NNLL (transverse momentum resummation);
  • HIGLU ( M. Spira): Inclusive cross section at QCD NLO, full top and bottom mass effects;
  • gg2VV ( N. Kauer): Parton-level integrator and event generator for gg(→H)→WW and gg(→H)→ZZ processes;

Results

Calculation by de Florian and Grazzini

NNLL+NNLO results including EW corrections and exact top and bottom contributions up to NLL+NLO: update of Phys.Lett.B674 (2009) 291.
The following table includes the central values of the inclusive cross section at 7 TeV, computed with MSTW2008 PDFs, together with the 68% CL PDF+αs and PDF uncertainties in percent.

mH (GeV) σ(pb) +(PDF+αs) -(PDF+αs) +PDF -PDF +scale -scale
90 29.4764 4.05 3.06 1.03 1.58 8.22 8.72
95 26.4775 4.04 3.05 1.05 1.56 8.04 8.56
100 23.9685 4.02 3.04 1.03 1.56 7.82 8.40
105 21.7439 4.00 3.04 1.05 1.56 7.65 8.26
110 19.8093 3.99 3.04 1.06 1.56 7.50 8.13
115 18.1150 3.98 3.04 1.08 1.56 7.36 8.01
120 16.6269 3.96 3.05 1.10 1.56 7.23 7.91
125 15.3055 3.95 3.06 1.12 1.57 7.11 7.80
130 14.1317 3.95 3.06 1.14 1.58 6.99 7.71
135 13.0817 3.94 3.07 1.17 1.59 6.88 7.61
140 12.1379 3.94 3.09 1.19 1.60 6.78 7.53
145 11.2888 3.93 3.10 1.22 1.61 6.69 7.45
150 10.5178 3.93 3.11 1.25 1.63 6.60 7.37
155 9.7978 3.93 3.13 1.28 1.65 6.52 7.30
160 9.0763 3.92 3.15 1.31 1.66 6.44 7.23
165 8.3519 3.92 3.16 1.34 1.69 6.37 7.16
170 7.7607 3.93 3.18 1.37 1.71 6.29 7.10
175 7.2409 3.93 3.20 1.40 1.73 6.22 7.04
180 6.7633 3.93 3.22 1.44 1.75 6.15 6.98
185 6.3241 3.94 3.24 1.47 1.77 6.12 6.92
190 5.9235 3.94 3.26 1.50 1.79 6.09 6.87
195 5.5733 3.95 3.28 1.54 1.82 6.06 6.81
200 5.2668 3.96 3.30 1.57 1.84 6.04 6.76
210 4.7375 3.97 3.35 1.63 1.90 6.00 6.67
220 4.2932 3.99 3.39 1.70 1.94 6.48 6.58
230 3.9153 4.02 3.44 1.78 2.00 5.92 6.49
240 3.5926 4.04 3.49 2.27 2.06 5.88 6.41
250 3.3159 4.07 3.53 1.91 2.11 5.85 6.34
260 3.0779 4.10 3.57 1.98 2.16 5.83 6.27
270 2.8727 4.13 3.62 2.05 2.23 5.83 6.20
280 2.6969 4.16 3.68 2.11 2.29 5.82 6.14
290 2.5478 4.19 3.72 2.18 2.34 5.81 6.08
300 2.4245 4.23 3.76 2.25 2.40 5.80 6.03
320 2.2496 4.31 3.87 2.38 2.53 5.76 5.95
340 2.1989 4.39 3.97 2.51 2.65 5.76 5.92
360 2.3612 4.48 4.06 2.64 2.76 5.85 5.86
380 2.2626 4.51 4.16 2.65 2.88 5.90 5.63
400 2.0267 4.71 4.26 2.91 3.00 5.91 5.43
450 1.3657 5.04 4.50 3.20 3.29 5.93 5.28
500 0.8654 5.41 4.75 3.50 3.58 5.97 5.22
550 0.5381 5.79 5.01 3.79 3.86 6.01 5.16
600 0.3356 6.16 5.26 4.07 4.14 6.11 5.16
650 0.2124 6.53 5.53 4.34 4.42 6.17 5.21
700 0.1364 6.89 5.79 4.61 4.70 6.26 5.27
750 0.0889 7.25 6.06 4.87 4.97 6.37 5.36
800 0.0588 7.61 6.34 5.13 5.24 6.45 5.42
850 0.0394 7.98 6.62 5.38 5.52 6.55 5.49
900 0.0267 8.34 6.91 5.63 5.79 6.66 5.59
950 0.0183 8.75 7.20 5.89 6.06 6.79 5.66
1000 0.0127 9.09 7.49 6.14 6.33 6.97 5.74

Higgs pT treatment

The Higgs pT was extensively discussed at the following meeting Higgs pT meeting. The present recommendations comes as outcome of that discussion.

Higgs pT central value

The Higgs pT central value for ggF process is given by the MC used for the simulation, possible choices are Powheg+(Pythia6,Pythia8,Herwig) and MC@NLO 4.10 plus Herwig (the use of Herwig++ is also possible but no studies were done with this configuration up to now).

Below follow technical implementation for the Powheg and MC@NLO generators.

Powheg

  • Analysis sensitive to high pT Higgs (pT > mH) should modify the Powheg code to use dynamic scale instead of the fixed Higgs mass scale, this is believed to be more appropriate at high pT and allows a more correct comparison and systematic determination respect to MC@NLO, an example code to allow dynamic scales in Powheg can be found at the following link LHCHXSWGPowhegDynamic.

  • All analysese sensitive to the Higgs pT should generate the following samples using the ggF including HQ mass effect in Powheg:

  1. Switch on the top mass only and use hfact=mH/1.2;
  2. Swith on the top and bottom mass and use hfact=4.75;
  3. Switch on the top mass only and use hfact=4.75;
  4. Normalise the samples 1,2,3 to the cross section indicated by Powheg and apply a k factor k= σYR/(σ1+σ2-σ3), the signal samples is obtained by combining the samples above as 1 + 2 - 3 (giving negative weight to the sample 3).

MCatNLO

  • MCatNLO uses dyanmic scale as default so doesn't need further patches, the version 4.10 allows to setup different scales for different processes. The instructions below refer to v4.10
  1. Produce a first sample with IMODEHGG=0, HVQMASS#0, HGGBMASS=0;
  2. Produce a second sample with IMODEHGG=1, HVQMASS#0, HGGBMASS#0;
  3. Normalise the samples 1,2 to the cross section indicated by MC@NLO and apply a k factor k= σYR/(σ1+σ2), the signal sample is obtained by combining the samples above as 1 + 2.

Higgs pT systematics.

  • Higgs pT systematics should be computed with HRES 2.0 using both bottom and top contributions, the following systematic variations should be considered:

  1. Scale variation: μR and μF varied between 2mH and mH/2 excluding μR/μF = 1/4 and 2;
  2. Resummation scales: Q1 varied between mH/4 and mH (the central value being mH/2) and Q2 varied between 3mb and mb/3 (the central value being mb);
  3. The maximum spread between 1 and 2 must be taken as uncertainty;
  4. PDF: The envelope among CT10, MSTW2008 and NNPD 2.1 must be taken as systematics (the envelope can be computed also using pdf reweighting on generated samples).
  5. For the technical implementation, several samples tuned to match the scale varied distribution of HRES would be recommended, for practical reason pT reweighting using the difference respect to the nominal HRES 2.0 prediction can be applied to compute uncertainties.

References

The calculations of the Higgs production cross sections are the result of the very hard work done by the theory community. We thus believe that the following papers should be directly acknowledged in the experimental work.

Inclusive cross section:

[1] Djouadi, Spira, Zerwas, PLB 264 (1991) 440; S. Dawson NPB 359 (1991) 283; Spira et al. NPB 453 (1995) 17.

[2] Kramer, Laenen and Spira, NPB 511 (1998) 523; Chetyrkin et al. NPB 510 (1998) 61.

[3] Harlander, Kilgore PRL 88 201801(2002); Anastasiou, Melnikov NPB 646 220 (2002); Ravindran, Smith, van Neerven NPB 665 325 (2003).

[4] Catani, de Florian Grazzini, Nason, JHEP 0307 028 (2003).

[6] Aglietti, Bonciani, Degrassi, Vicini PLB 595 432 (2004); Actis, Passarino, Sturm, Uccirati, PLB 670 12 (2008).

[7] Anastasiou,Boughezal, Petriello, JHEP 0904 003 (2009); de Florian, Grazzini, PLB 674 (2009) 291.

[8] Moch, Vogt, Phys. Lett. B631 (2005) 48; Laenen, Magnea Phys. Lett. B632 (2006) 270; Idilbi et al, Phys. Rev. D73 (2006) 077501; V.Ravindran, Nucl. Phys. B746 (2006) 58.

[9] Anastasiou,Buehler, Herzog,Lazopoulos, JHEP 1112 058 (2011).

Cross section with cuts:

[10] Anastasiou, Melnikov, Petriello, PRL 93 262002 (2004), NPB 724 197 (2005); Anastasiou, Dissertori, Stoeckli, JHEP 0709 (2007) 018.

[11] Catani, Grazzini, PRL 98 222002 (2007); M.Grazzini, JHEP 02 (2008) 043.

Jet bin uncertainties

[12] Stewart, Tackmann, Phys.Rev. D85 (2012) 034011

Meetings

Links

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Topic revision: r21 - 2014-11-04 - ReiTanaka
 
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