Status and perspectives - Durham University
Transcript of Status and perspectives - Durham University
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Status and perspectiveson
loop-induced processes
Marek Schonherr
Universitat Zurich
ATLAS–CMS Monte Carlo Generators Workshop
Marek Schonherr 1/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Disclaimer
I am an author of the SHERPA event generator, but I will try to keep thatbias out of the following summary.
This review cannot be exhaustive, but I will focus on most importantprocesses/process classes and recent developments/tools.
I will restrict myself to published results, with the implicit understandingthat modern automated one-loop programs can calculate these processeswithout a dedicated publication.
Marek Schonherr 2/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Introduction
• Common signature gg → EW bosonsexceptions e.g. same sign top production etc.
• Distinguish two cases
1) Loop-induced as sole production mode, e.g. gg → h→ few cases with EFT approximation
2) Tree-level production in qq dominant→ gauge invariant subset of NNLO calculation→ no guarantee that dominant part of NNLO correction
• Important production mechanism even if tree-level production exists→ scales with gg/qq luminosities
• Implementations available in many parton level gens (MCFM, etc.)→ will focus on particle level implementations
• when qq exists, then part of NNLO codes (for VV , VH etc.)
• Generally known only at LO, at most estimates of NLO corrections
Marek Schonherr 3/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Higgs production in gluon fusion
• for inclusive ggh coupling HEFT working well, correction toloop-induced flat and incorporated in every implementation
• for pp → h + n jets HEFT good enough to be reweighted→ O(1) corrections throughout phase space
⇒ can be incorporated in all the multijet merged at NLO machineryavailable for HEFT
• available in MADGRAPH, OPENLOOPS, GOSAM
Hirschi, Mattelaer JHEP10(2015)146
Marek Schonherr 4/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Higgs production in gluon fusionBuschmann, Goncalves, Kuttimalai, MS, Krauss, Plehn JHEP02(2015)038
pp → H + jets production (ggF)
• correction factor/weight
r(n)t =
|M(n)(mt)|2|M(n)(mt →∞)|2
• loops from OPENLOOPS
• construct MEPS@NLO fromreweighted S-MC@NLO
• factorised approach forunknown top massdependence in Vn, otherwiseexact NLO mass dependence
0 100 200 300 400 500 600
-410
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-110
1 tmH+0j NLO
tmH+1j NLO
tmH+2j LO
tmH+jets NLO
∞ →tmH+jets NLO
GeVfb
T,Hdp
σd
[GeV]T,H
p0 100 200 300 400 500 600
0.2
0.4
0.6
0.8
1
1.2
∞→tm(N)LO
tm(N)LO
SHERPA+OPENLOOPS
dσn = dΦn r(n)t
[Bn + Vn +
∫dΦ1 Dn
]PSn + dΦn+1
[r
(n+1)t Rn − r
(n)t Dn
]Marek Schonherr 5/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Interference in Higgs production
Buschmann, Goncalves, Kuttimalai, MS, Kraus, Plehn JHEP02(2015)038
100 200 300 400 500 600 700 800 900 1000
-410
-310
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-110qq
gg
=(0,0)t,gκ
=(1,0)t,gκ
=(0,1)t,gκ
GeVfb
4ldm
σd ZZ→pp
SMHΓ=HΓ
[GeV]4lm100 200 300 400 500 600 700 800 900 10000
1
2
3
=(0,1)t,gκLO=(1,0)t,gκLO
100 200 300 400 500 600 700 800 900 1000
-410
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-110qq
gg
=(0,0)t,gκ
=(1,0)t,gκ
=(0,1)t,gκ
GeVfb
4ldm
σd ZZ→pp
SMHΓ=25HΓ
[GeV]4lm100 200 300 400 500 600 700 800 900 10000
1
2
3
=(0,1)t,gκLO=(1,0)t,gκLO
investigate new physics in pp → 4`, qq @ NLO, gg @ LOparametrised in κ framework, SM: (κt , κg ) = (1, 0)
Marek Schonherr 6/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Interference in Higgs production
Coradeschi, de Florian, Dixon, Fidanza, Hoche, Ita, Li, Mazzitelli PRD92(2015)013004
-20
-10
0
10
∆m
H@MeVD
M jj>400GeV
VBF
GF
Sum
0 1 2 3 4 5 6 7 80.001
0.01
0.1
1
10
ÈDΗjj min
Signal@fbD
mass shift in mγγ in VBF/GF–background interferencequickly increases with ΓH
Marek Schonherr 7/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Interference in Higgs production
Coradeschi, de Florian, Dixon, Fidanza, Hoche, Ita, Li, Mazzitelli PRD92(2015)013004
0 5 10 15 20-350
-300
-250
-200
-150
-100
-50
0
G� GSM
Dm
HΓΓ@MeVD
mass shift in mγγ in VBF/GF–background interferencequickly increases with ΓH
Marek Schonherr 7/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Double/Triple Higgs production in gluon fusion
Maltoni, Vryonidou, Zaro JHEP11(2014)079
• reweight in dΦB with rBt ,in dΦR with rRt
• factorised approach forvirtual corrections
100755033251413
103
102
101
pp→HH
LOFT
pp→HH
NLOFTap
prox
Mad
Gra
ph5
aMC
@N
LO
MH=125 GeV, MSTW2008 (N)LO pdf (68%cl)
HH production at pp colliders
. .
-
√s[TeV]
σ(N
)LO[fb]
100755033251413
100
10−1
pp→HHH
LOFT
pp→HHH
NLOFT ap
prox
Mad
Gra
ph5
aMC
@N
LO
MH=125 GeV, MSTW2008 (N)LO pdf (68%cl)
HHH production at pp colliders
. .
-
√s[TeV]
σ(N
)LO[fb]
Marek Schonherr 8/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Double Higgs production in gluon fusionMaierhofer, Papaefstathiou JHEP03(2014)126
0j inc.ETclus = 50GeV
ETclus = 60GeV
ETclus = 70GeV
10−5
10−4
10−3
10−2
Separation between Higgs bosons
dσ/d
∆R(h,h)[pb]
1 2 3 4 5 6
0.5
1
1.5
2
∆R(h, h)
Ratio
0j inc.ETclus = 50GeV
ETclus = 60GeV
ETclus = 70GeV
10−8
10−7
10−6
10−5
10−4
hh p⊥
dσ/dphh ⊥[pb/GeV
]100 200 300 400 500 600
0.6
0.8
1
1.2
1.4
phh⊥ [GeV]Ratio
• LO merging for pp → hh + 0, 1 jets in MLM scheme
• use exact loop-induced, no reweighting
• using HERWIG+++OPENLOOPS
Marek Schonherr 9/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Associated Higgs production
• only gg → HZ , gg → HZg , gq → HZq and gg → Hγg
• relative size of contribution strongly dependent on observable
Hirschi, Mattelaer JHEP10(2015)146
Marek Schonherr 10/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Associated Higgs productionHespel, Maltoni, Vryonidou JHEP06(2015)065
g
gg
H
Z
g
g
g
H
Z
g
g
g
H
Z
ggg
g
H
g
Zq
H
Z
q q
H
Z
q
q
q
H
Z
gZ
H
gq
q
MLM merge loop-inducedZH productiongg → ZHgg → ZHg and gq → ZHq
powerwimpy
scale uncertaintiesZH + ZHj, merged
MadGraph5aMC@NLO
PHT [GeV]
5004003002001000
partonpowerwimpy
scale uncertaintiesZH
LHC14TeVMSTW2008LO
-
.
PHT [GeV]
dσ/d
PH T
[fb/b
in]
5004003002001000
1
0.1
0.01
0.001
Marek Schonherr 11/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Associated Higgs production
Goncalves, Krauss, Kuttimalai, Maierhofer PRD92(2015)7,073006
pp → ``H + jets production
• MEPS@NLO for qqMEPS@LOOP2 for gg
• care for qg → ZHq:
→ part of NLO ZHj→ in loop-induced as gauge→ inv. subset of NNLO ZHj
10−3
10−2
10−1
dσ
/d(|E
mis
sT−
pll T|/
pll T)
[pb]
Sherpa+OpenLoops
MEPS@NLO [scale variations]MEPS@NLO 0-jet exclusive
MEPS@Loop2 [scale variations]
MEPS@Loop2 [k-factor variations]
MEPS@Loop2 0-jet exclusive
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40|Emiss
T − pllT|/pll
T
0.0
0.2
0.4
0.6
0.8
Rat
ioto
inc.
sam
ple
pp → Z [→`` ]H[→ inv] + jets
Marek Schonherr 12/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Associated Higgs production
Goncalves, Krauss, Kuttimalai, Maierhofer PRD92(2015)7,073006
pp → ``H + jets production
• MEPS@NLO for qqMEPS@LOOP2 for gg
• care for qg → ZHq:
→ part of NLO ZHj→ in loop-induced as gauge→ inv. subset of NNLO ZHj
[GeV]BDRSHm
80 100 120 140 160
GeVfb
BDRS
Hdm
σd
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-310
-210
MEPS@NLO HZ+0,1j HZ+0,1j2MEPS@Loop
Sherpa+OpenLoops
[GeV]BDRSHm
80 100 120 140 1600.20.30.40.5 /MEPS@NLO2MEPS@Loop
F/CA0.18 C
[GeV]BDRSHm
80 100 120 140 1600.20.40.60.8 jet-veto/incl
pp → Z [→``]H[→bb] + jets
Marek Schonherr 12/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Vector boson pair production
• relative size of contribution strongly dependent on observable,but typically < 10%
Hirschi, Mattelaer JHEP10(2015)146
Marek Schonherr 13/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Vector boson pair productionCascioli, Hoche, Krauss, Maierhofer, Pozzorini, Siegert arXiv:1309.5912
pp → 4`+ 0, 1 jetsand pp → 2`2ν + 0, 1 jets
• MEPS@NLO for qqMEPS@LOOP2 for gg
• includes loop-inducedgg → 4`,gg → 4`+ g , gq → 4`+ q,qq → 4`+ g
Sherpa+OpenLoops
MEPS@NLO 4ℓ+ 0, 1jµF,R/2 · · · 2µF,RµQ/
√2 · · ·
√2µQ
Unc. quad. sum
MC@NLO 4ℓNLO 4ℓ
0
10
20
30
40
50
60
70
80
90
Azimuthal lepton distance (ATLAS, Njet = 0)
dσ/d
∆φℓℓ[fb]
0.80.91.01.11.2
dσ/d
σMEPS@NLO
0 0.5 1 1.5 2 2.5 3
0.02
0.04
0.06
0.08 MEPS@LOOP2 4ℓ+ 0, 1j
∆φℓℓ
dσ/d
σMEPS@NLO
Marek Schonherr 14/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Vector boson pair productionCascioli, Hoche, Krauss, Maierhofer, Pozzorini, Siegert arXiv:1309.5912
pp → 4`+ 0, 1 jetsand pp → 2`2ν + 0, 1 jets
• MEPS@NLO for qqMEPS@LOOP2 for gg
• includes loop-inducedgg → 4`,gg → 4`+ g , gq → 4`+ q,qq → 4`+ g
Sherpa+OpenLoops
MEPS@NLO 4ℓ+ 0, 1jµF,R/2 · · · 2µF,R
µQ/√2 · · ·
√2µQ
Unc. quad. sum
MC@NLO 4ℓNLO 4ℓ+ 1j
0
0.1
0.2
0.3
0.4
0.5
Lepton pair mass (CMS, Njet = 1)
dσ/dm
ℓℓ[fb/GeV]
0.80.91.01.11.2
dσ/d
σMEPS@NLO
50 100 150 200 250 300
0.02
0.04
0.06
0.08 MEPS@LOOP2 4ℓ+ 0, 1j
mℓℓ [GeV]
dσ/d
σMEPS@NLO
Marek Schonherr 14/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Multiboson production
• many process, generally very small cross section
Hirschi, Mattelaer JHEP10(2015)146
Marek Schonherr 15/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Tools
Process specific tools:
• gg2VV+HERWIG/PYTHIA Kauer JHEP12(2013)082
- gg → 2`2ν, 4`
...
General tools:
• MADGRAPH+HERWIG/PYTHIA Hirschi, Mattelaer JHEP10(2015)146
- all on-shell 2→ 2 and 2→ 3 processes, some 2→ 4 in SM- MLM merging possible with PYTHIA6
• SHERPA+OPENLOOPS several publications
- all off-shell 2→ 2 and 2→ 3, e.g. gg → 4`g- MEPS@LOOP
2 merging possible
Marek Schonherr 16/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Timings – MADGRAPH
Timing for 10k unweighted events (number of phase space points needed)
Hirschi, Mattelaer JHEP10(2015)146
Marek Schonherr 17/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Timings – OPENLOOPS
Timing per phase space point using COLLIER
Process ms/point Process ms/point Process ms/point
gg → h 0.11 gg → hh 1.3gg → hg 1.6 gg → hhg 47 gg → γg 2.7gg → hgg 50 gg → γgg 117gg → he+e− 2.0 gg → e+e− 0.28 gg → e+e−γ 4.3gg → he+e−g 61 gg → e+e−g 4.9 gg → e+e−γg 128
Process ms/point Process ms/point
gg → e+e−µ+µ− 8.9 gg → e+νeµ−νµ 2.0gg → e+e−µ+µ−g 238 gg → e+νeµ−νµg 72gg → e+e−e+e− 25 gg → e+νee−νe 6.2gg → e+e−e+e−g 638 gg → e+νee−νeg 202
Marek Schonherr 18/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Conclusion
• all processes in SM available by several toolsprocess specific, MADGRAPH+HERWIG/PYTHIA,SHERPA+OPENLOOPS, SHERPA+GOSAM
• improve EFT used otherwiseinclude important subleading process where qq channel exists,gg has different propertiescalculate signatures inaccessible otherwise
• NLO corrections are two-loop, usually with many mass scales→ generally not available
• NLO K -factors are estimated to be large ≈ 2
• selected BSM processes appeared in the literature
• timings/efficiencies vary between tools
Marek Schonherr 19/20
Loop-induced as sole production mechanism Loop-induced as additional production mechanism Tools Conclusion
Thank you for your attention!
Marek Schonherr 20/20