Calculations of Higgs x-sections at N k LO ATL-COM-PHYS-2009-161

Calculations of Higgs x-sections at NkLO

ATL-COM-PHYS-2009-161

A.-C. Bourgaux, M. Escalier, L. Fayard1

Tools: FEHiP, HggTotal, HNNLO, HqT

Factorisation (µF) and renormalisation (µ

R) scales :

F=

R in [m

H/2 ; 2m

H ] 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 = 172.7 GeV for FEHiP,

178 GeV for HNNLO (study in appendix)

Tools and parameters used

2

TeVs 10

Anastasiou

Total x-sections (100-800 GeV)

• HNNLO mt ∞No correction

• FEHiP mt ∞ + correction:

)(

)()(

tLO

tLOt m

mmF

3

Result table, approx of ∞ mass t; b appendix

tt

4

Total x-sections with HggTotalGood agreement with calculations by De Florian and Grazzini, with a different choice for R and F.

Anastasiou : arXiv:0811.3458, arXiv:hep-ph/0207004

"We present results for the Higgs boson cross section accounting for these e ects. We account for the e ect of ff ffsoft-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."

Available : http://www.phys.ethz.ch/~babis/Software/

5

x-sections*BR with HNNLO

× Br(H )

6

Br(H )

(Br tables of HNNLO seem to be computed from Hdecay)

7

differential x-sections with HNNLO

gg fusion Higgs 2 photons γ

LO _ pT34 pT3 &pT4

y34 η3 & η4

NLO pT5 pT34 pT3 &pT4

y34 η3 & η4

NNLO pT5 pT34 pT3 & pT4

pT6 y34 η3 & η4

1

2

H3

4

5 (jet)

6 (jet)

)(

d

d

For high masses, the photon is more central

8

mH=100 GeVstable observable / pert order

mH=100 GeV mH=800 GeVphoton

normalized:ATL-COM-PHYS-2009-161 Qian, Liu,

Mansoulie, Purdham, Strandberg, Thun

)(

Tdp

dmH=100 GeV

fixed order calculation :LO bounded at pt=mH/2 NLO and NNLO unstables in this region

9

photon

normalized: ATL-COM-PHYS-2009-161

)(Hdy

d

mH=100 GeV mH=800 GeV

Detector acceptance will limit the rapidity range that can be measured 10

Higgs

stable observable / pert ordermH=100 GeVnormalized:

ATL-COM-PHYS-2009-161

)(Hdp

d

T

11

Higgs compatible with statistical error

mH=100 GeV

ATL-COM-PHYS-2009-161

Construction of the curve :

• Resummed : divergent terms only « resummed »=exp(Sudakov factor)

• Asymptotic : limit of perturbative order when PT0 : divergent terms only

• Fix order : all perturbative developpement terms, including divergent terms

Matched = Resummed + Fix order - Asymptotic

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PT of Higgs : HqT

13

Higgs PT, @ LO and NLOmH=125 GeV )(Hdp

d

T

Correction to pT(H) : appendix

Normalized : ≠ from HNNLO

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HNNLOHqTresummation for low pT fix order for high pT

Investigate resummation scale in the code ?

15

To be done :

- Influence of resummation scale

- Cuts influences in fehip and hnnlo for acceptances studies

-Preliminary studies up to now…

Appendix

16

17

Approximation of infinity mass of t ; b

Plot from Frank Petriello

?!?http://agenda.hep.wisc.edu/getFile.py/access?contribId=9&resId=0&materialId=slides&confId=189

18

19

@ LO (same observations at NLO…), using mrst2001Complete study in appendix

Major effect: σ decreases with µR

Influence of µF µR

Minor effect: σ increases or decreases with µF depending on mass

maximum central value minimum

mH=120 GeV mH=190 GeV

F F

0.5 1 2 0.5 1 2

R 0.5 14.7 15.02 15.10 R 0.5 5.98 5.87 5.71

1 11.8 12.02 12.10 1 4.86 4.77 4.64

2 9.62 9.84 9.91 2 4.03 3.95 3.85

Influence of mt

HNNLOmt ∞ without correction

FEHiPmt ∞+ correction:

)(

)()(

tLO

tLOt m

mmF

program hnnlo hnnlo fehip fehip fehipmt (GeV) 178 172 172.7 172 F(mt)=1 LO (100 GeV) 18.704 18.706 19.467 19.474 18.702 NLO (100 GeV) 31.643 _ 33.006 33.017 31.708 LO (200 GeV) 3.937 _ 4.686 4.694 3.935 NLO (200 GeV) 7.21 _ 8.585 8.599 7.209 LO (800 GeV) 0.063 0.063 0.078 0.077 0.063 NLO (800 GeV) 0.126 _ 0.156 0.155 0.126

mt : little influence

HNNLO and FEHiP differences due to F(mt) 20

Influence of pdf Our results with FEHiP:

mrst2001 mstw2008+14%

LO, 100 GeV: 17,159 19,467+6%

NLO, 100 GeV 31,117 33,005

With HNNLO:mrst2002 mstw2008

+13% LO, 100 GeV 16,507 18,704

+8% LO, 200 GeV 3,632 3,937

Results compatible with:Martin,Stirling,Thorne,Watt, arXiv:0901.0002v2

+10%mrst2002 mstw2008 21

Check of constistency:2 equivalent photons ?(no cuts applied at generation)

)()( 43

d

d

d

d

)()( 43

TT dp

d

dp

d

m=100 GeV

22

23

What is the uncertainty on PT(H)?

Balazs, Grazzini, Huston, Kulesza,Puljak arXiv:hep-ph/0403052v1

Corrections to pT(H)

LHC :30 ≤PT≤50 GeV : -4 %50≤PT≤150 : %PT~300 GeV : -30 %

Keung, Petriello, hep-ph 0905.2775

• Finite top quark mass ; Bottom quark contribution

24

• EW gauge boson terms (W, Z)

Keung, Petriello, hep-ph 0905.2775

LHC :100≤PT≤300 GeV : -3 %

25

26

Prescription used for ATL-COM-PHYS-2007-024

Should we use same prescription ? Arguments for prescription ?

EW corrections

2-loop EW corrections for H :

eg of production corrections eg of decay corrections

27

28

contrib. of top

-top quark contributions : ~15 % of light contributionDegrassi, Maltoni, hep-ph/0407249Total : 5-8 % correction

29

(no top correction)

-light fermions contributionsAglietti, Bonciani, Degrassi, Vicini,hep-ph/0404071

QCD

EWtotal

production decay

9 % to LOup to –10 % correction