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Calculations of Higgs x-sections at N k LO ATL-COM-PHYS-2009-161 A.-C. Bourgaux, M. Escalier, L. Fayard. Tools and parameters used. Anastasiou. Tools: FEHiP, HggTotal, HNNLO, HqT Factorisation ( µ F ) and renormalisation ( µ R ) scales : - PowerPoint PPT Presentation
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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
12
PT of Higgs : HqT
13
Higgs PT, @ LO and NLOmH=125 GeV )(Hdp
d
T
Correction to pT(H) : appendix
Normalized : ≠ from HNNLO
14
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
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