high-mass h vv signal and higgs width determination at the lhc€¦ · n. kauer high-mass h → v v...

High-mass H → V V signal and Higgs width

determination at the LHC

Nikolas Kauer

Royal Holloway, University of London (RHUL)

in collaboration with

Claire O’Brien (RHUL) and Eleni Vryonidou (Louvain)

arXiv:1206.4803 in collaboration with Giampiero Passarino

Particle Physics Seminar

University of Oxford

March 10, 2015

1 / 48

Outline

• H → ZZ,WW in ggF & VBF: sizeable off-shell Higgssignal contribution with large signal-backg. interference

• H → WW/ZZ → ℓνℓℓνℓ and ZZ → 4ℓ interference in ggF

• Interference for pp → H → ZZ + jet

• Higgs width measurement in a nutshell

• off-shell Higgs boson signal strength & novel Higgs widthbound, “pioneering” ATLAS & CMS analyses

• BSM: model dependence of the Higgs width bound

• Higgs width constraints from gg → H → γγ• Exploiting the high-mass H → V V region: EFT

• SM: Interference effects for semileptonic decay modes

• BSM: Heavy Higgs-light Higgs-bkg. interference effects

• High-mass H → V V signal at a linear collider

• LHC-HXSWG: Yellow Report 4 projects

• Summary

N. Kauer High-mass H → V V signal and Higgs width determination at the LHC PP Seminar, Oxford 10 Mar 2015 2 / 48

SM Higgs boson production and decay at the LHC

[GeV]HM90 200 300 400 1000

Hig

gs B

R +

Tota

l U

ncert

410

310

210

110

1

LH

C H

IGG

S X

S W

G 2

01

3

bb

ττ

µµ

cc

gg

γγ γZ

WW

ZZ

Discovery publications:

ATLAS, Observation of a new particle in the search for the SM Higgs boson ..., Phys. Lett. B 716 (2012) 1.

CMS, Observation of a new boson at a mass of 125 GeV ..., Phys. Lett. B 716 (2012) 30.

And many papers with updates and more detailed characterisation (couplings, spin/CP), e.g.:

ATLAS, Measurements of Higgs boson production and couplings in diboson final states ..., Phys. Lett. B 726 (2013) 88; ATLAS,

Updated coupling measurements of the Higgs boson ..., ATLAS-CONF-2014-009; ATLAS, Evidence for the spin-0 nature of the

Higgs boson ..., Phys. Lett. B 726 (2013) 120.

CMS, Observation of a new boson with mass near 125 GeV ..., JHEP 1306 (2013) 081; CMS, Study of the mass and spin-parity

of the Higgs boson candidate via its decays to Z boson pairs, Phys. Rev. Lett. 110 (2013) 081803; CMS, Measurement of the

properties of a Higgs boson in the four-lepton final state, Phys. Rev. D 89 (2014) 092007.


SM Higgs boson production and decay at the LHC

Experimental studies have been informed by numerous theoretical papers (too many to list),

summarised in Higgs physics reviews, e.g.:

A. Djouadi, The Anatomy of electro-weak symmetry breaking. I: The Higgs boson in the standard model, Phys. Rept. 457 (2008) 1.

A. Djouadi, The Anatomy of electro-weak symmetry breaking. II. The Higgs bosons in the minimal supersymmetric model, Phys. Rept.

459 (2008) 1.

A. Djouadi, Higgs Physics: Theory, Pramana 79 (2012) 513.

D. Carmi, A. Falkowski, E. Kuflik, T. Volansky and J. Zupan, Higgs After the Discovery: A Status Report, JHEP 1210 (2012) 196.

L. Reina, TASI 2011: lectures on Higgs-Boson Physics, arXiv:1208.5504 [hep-ph].

S. Dittmaier and M. Schumacher, The Higgs Boson in the Standard Model - From LEP to LHC: Expectations, Searches, and Discovery

of a Candidate, Prog. Part. Nucl. Phys. 70 (2013) 1.

Higgs Working Group Report of the Snowmass 2013 Community Planning Study, arXiv:1310.8361 [hep-ex].

J. Ellis, Higgs Physics, arXiv:1312.5672 [hep-ph].

H. E. Logan, TASI 2013 lectures on Higgs physics within and beyond the Standard Model, arXiv:1406.1786 [hep-ph].

J. Ellis, LHCP 2014: Theory Summary and Prospects, arXiv:1408.5866 [hep-ph].

and the LHC Higgs Cross Section Working Group reports (also other WGs, see above):

LHC Higgs Cross Section WG, Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables, CERN-2011-002.

LHC Higgs Cross Section WG, Handbook of LHC Higgs Cross Sections: 2. Differential Distributions, CERN-2012-002.

LHC Higgs Cross Section WG, Handbook of LHC Higgs Cross Sections: 3. Higgs Properties, CERN-2013-004.

LHC Higgs Cross Section WG, Interim recommendations to explore the coupling structure of a Higgs-like particle, arXiv:1209.0040

[hep-ph].

bottom line: no compelling Standard Model deviations found so far, search continues in Run 2


gg → H → ZZ,WW : sizeable off-shell Higgs signal with

large signal-background interference

100 2 MZ 2 Mt 1000

10−6

10−5

10−4

10−3

ZZ

HTO powered by complex - pole - scheme

MV V [ GeV]

M2 VV

dσ

dM

2 VV

[pb]

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

10

100

0 100 200 300 400 500 600 700 800 900

MZZ [GeV]

gg (→ H) → Z(γ∗)Z(γ∗) → ℓℓℓℓ, MH=126GeV

pp,√s = 8TeV

pTℓ > 3GeV, |ηℓ| < 2.6

Mℓℓ > 4GeV, pT (Z) > 2GeV

gg2VV

dσ/d

MZZ

[fb/GeV

]

Hoffshell

|H|2+|cont|2|H+cont|2

[GeV]H

M

100 200 300 1000

BR

[pb]

× σ

-410

-310

-210

-110

1

10

LH

C H

IGG

S X

S W

G 2

01

2

= 8TeVs

µl = e,

τν,µν,eν = νq = udscb

bbν± l→WH

bb-l+ l→ZH

b ttb→ttH

-τ+τ →VBF H

-τ+τ

γγ

qqν± l→WW

ν-lν+ l→WW

qq-l+ l→ZZ

νν-l+ l→ZZ

-l+l

-l+ l→ZZ

• gg → H → V V → 4ℓ and 2ℓ2ν signal-background interference very well studied at LO:

Glover, van der Bij (1989); Kao, Dicus (1991); Binoth, Ciccolini, NK, Kramer (2006) (gg2WW); Campbell, Ellis, Williams (2011)

(MCFM); NK (2012) (gg2VV); NK, Passarino (2012); Campanario, Li, Rauch, Spira (2012); Bonvini, Caola, Forte, Melnikov, Ridolfi

(2013); Caola, Melnikov (2013); NK (2013) (gg2VV); Campbell, Ellis, Williams (2013) (MCFM); Campbell, Ellis, Williams (2014)

(MCFM); Campbell, Ellis, Furlan, Rontsch (2014); related interference effects: Bredenstein, Denner, Dittmaier, Weber (2006)

(PROPHECY4f); YR3: Denner, Dittmaier, Muck (2013) and Anderson, Bolognesi, Caola, Gao, Gritsan, Martin, Melnikov, Schulze,

Tran, Whitbeck, Zhou (2013); Chen, Cheng, Gainer, Korytov, Matchev, Milenovic, Mitselmakher, Park, Rinkevicius, Snowball

(2013); Chen, Vega-Morales (2013)

• tools for ggF: MCFM-6.8, gg2VV-3.1.7 (parton-calculators and LO event generators)

• loop technology closing in on NLO calc. (bottleneck: heavy quark loop) Zurich, Karlsruhe, FNAL-RWTH, ...

• gluon-fusion Higgs production and semileptonic decay: Dobrescu, Lykken (2010); Lykken, Martin, Winter

(2012); Kao, Sayre (2012); ATLAS arXiv:1206.2443; ATLAS arXiv:1206.6074; CMS PAS HIG-13-008


Sizeable off-shell Higgs signal in vector boson fusion

• similar effect in VBF H → V V (NK, Passarino): O(10%) of Higgs signal is off-shell

note: no exp. sensitivity to off-shell H → V V tail in V H and ttH channels (see σprod(MH))

• total off-shell Higgs signal has ∼ 10% VBF contribution

Covarelli, Anderson, Sarica

figures taken from Covarelli’s talk at LHC HXSWG workshop (12 Jun 2014)

• tools for VBF: MadGraph5 Alwall et al., Phantom Ballestrero et al., VBFNLO Baglio et al.



CMS-HIG-14-002 Higgs width constraint from off-shell H → ZZ includes

analysis of VBF contribution (as correction to ggF) Covarelli, Anderson, Sarica

4ℓ 2ℓ2ν

(a) Total gg (ΓH = ΓSMH ) 1.8±0.3 9.6±1.5

gg Signal component (ΓH = ΓSMH ) 1.3±0.2 4.7±0.6

gg Background component 2.3±0.4 10.8±1.7(b) Total gg (ΓH = 10× ΓSM

H ) 9.9±1.2 39.8±5.2

(c) Total VBF (ΓH = ΓSMH ) 0.23±0.01 0.90±0.05

VBF signal component (ΓH = ΓSMH ) 0.11±0.01 0.32±0.02

VBF background component 0.35±0.02 1.22±0.07(d) Total VBF (ΓH = 10× ΓSM

H ) 0.77±0.04 2.40±0.14(e) qq background 9.3±0.7 47.6±4.0(f) Other backgrounds 0.05±0.02 35.1±4.2

(a+c+e+f) Total expected (ΓH = ΓSMH ) 11.4±0.8 93.2±6.0

(b+d+e+f) Total expected (ΓH = 10× ΓSMH ) 20.1±1.4 124.9±7.8

Observed 11 91

table taken from arXiv:1405.3455

Expected and observed numbers of events in the 4ℓ and 2ℓ2ν channels in gg-enriched regions, defined by m4ℓ ≥330GeV and Dgg > 0.65 (4ℓ), and by mT > 350GeV and Emiss

T > 100GeV (2ℓ2ν). Numbers of expected events

are given for a SM Higgs boson (ΓH = ΓSMH ) and a Higgs boson width and squared product of the couplings scaled by

a factor 10 with respect to their SM values. Total gg and VBF include the negative interferences.



Dedicated VBF study for H → ZZ → 4ℓ Englert, Spannowsky

VBF selection cuts are applied, which essentially remove ggF contribution:

pT (j) > 20 GeV, ∆R(jj) ≥ 0.6, |yj | < 4.5,

∆y(jj) ≥ 4.5, yj1 × yj2 < 0, m(jj) ≥ 800 GeV ,

∆R(ℓj) ≥ 0.6, all ℓ inside the tagging jets’ rapidity gap ,

and a jet veto: |yvetoj | < 2.5, p

vetoT (j) > 50 GeV, ∆y(jvetoj) > 0.3

Off-shell signal: σH (VBF selection, m4ℓ ≥ 130 GeV, ℓ = e, µ) ≃ 0.04 fb at 14 TeV

54.543.532.521.51

1.75

1.5

1.25

1

0.75

0.5

0.25

statistical uncertainty for 600/fb

Γh/ΓSMh

σ/σ

SM

(WB

F)

figure taken from arXiv:1405.0285


gg → H → WW/ZZ → ℓνℓℓνℓ interference (gg2VV)Integrated cross sections (SM Higgs)

gg (→ H) → V V → ℓνℓ ℓνℓ ,

σ [fb], pp,√s = 8 TeV,

MH = 126 GeV, min. cuts,

µR = µF = Mℓνℓℓνℓ/2 interference

V V H cont |H+cont|2 R1=(S+B+I)/(S+B) R2=(S+I)/S

WW 17.318(4) 16.925(4) 32.803(8) 0.9580(3) 0.9169(6)

ZZ 0.8822(2) 2.1553(6) 2.872(1) 0.9455(4) 0.813(2)

WW/ZZ 17.402(3) 19.084(4) 34.884(7) 0.9561(3) 0.9079(5)

R3 0.9562(3) 1.0002(3) 0.9778(3) σ(|WW + ZZ|2)/σ(|WW |2 + |ZZ|2)R4 0.9540(3) 1.0002(4) 0.9759(4) (σ(|WW |2) + IWW/ZZ)/σ(|WW |2)R6 0.05094(2) 0.12735(5) 0.08756(4) σ(|ZZ|2)/σ(|WW |2)

minimal cuts: WW/ZZ interference: Higgs signal: ≈5%, gg continuum: negligible

Differential cross sections

1e-05

0.0001

0.001

0.01

0.1

20 40 60 80 100 120 140

MV V [GeV]

gg → WW/Z(γ∗)Z → ℓℓνℓνℓ, LHC8, Mℓℓ > 4GeV

dσ/d

MVV

[fb/GeV

]

|WW |2+|ZZ|2|WW+ZZ|2

gg → WW/ZZ continuum: MV V distribution

MV V > 95 GeV: WW/ZZ interference negligible

MV V < 95 GeV: WW/ZZ interference of ≈ 5%

see also: H → WW/ZZ →ℓνℓℓνℓ interference at LO &

NLO Muck, Bredenstein, Den-

ner, Dittmaier, Weber YR3

arXiv:1307.1347, Sec. 2.2


gg → H → WW/ZZ → ℓνℓℓνℓ interference (gg2VV)

Integrated cross sections (SM Higgs with Higgs search cuts)

gg (→ H) → V V → ℓνℓℓνℓ,

σ [fb], pp,√s = 8 TeV,

MH = 126 GeV,

Higgs search cuts interference

V V H cont |H+cont|2 R1 R2

WW 2.9303(7) 0.7836(4) 3.6649(8) 0.9868(4) 0.9833(4)

ZZ 0.004658(3) 0.002851(2) 0.007494(3) 0.9979(6) 0.9966(9)

WW/ZZ 2.8758(7) 0.7864(4) 3.6131(8) 0.9866(3) 0.9829(4)

R3 0.9799(4) 0.9999(8) 0.9839(3)

R4 0.9798(4) 0.9999(8) 0.9838(3)

R6 0.0015898(9) 0.003638(3) 0.002045(1)

Cuts: pTℓ,1st > 25 GeV, pTℓ,2nd > 15 GeV, |ηℓ| < 2.5, p/T > 45 GeV, Mℓℓ > 12 GeV,

|Mℓℓ −MZ | > 15 GeV, Mℓℓ < 50 GeV, ∆φℓℓ < 1.8, 0.75MH < MT1 < MH

MT1 =√

(MT,ℓℓ + p/T )2 − (pT,ℓℓ + p/T )2 with MT,ℓℓ =√

p2T,ℓℓ

+M2ℓℓ

NK arXiv:1310.7011


gg → H → ZZ → 4ℓ interference (MCFM)

Campbell, R.K. Ellis, Williams figures taken from arXiv:1408.1723

Note: full ZZ → 4ℓ interference effects are also implemented in gg2VV


gg → H → WW/ZZ → ℓνℓℓνℓ interference (MCFM)

Campbell, R.K. Ellis, Williams figures taken from arXiv:1408.1723


Interference for pp → H → ZZ + jet

off-shell Higgs cross sections for ZZ and ZZ+jet comparable (pTj > 30 GeV)

Campbell, R.K. Ellis, Furlan, Rontsch figures taken from arXiv:1409.1897

Z bosons treated in zero-width approximation (validated for ZZ final state: excellent for m4l > 300 GeV)


Higgs width measurement in a nutshell

• Total Higgs width ΓH is not a fundamental parameter of the theory, but of great phe-

nomenological interest (Higgs mechanism → overall coupling strength)

• Direct Higgs width measurement via resonance shape is limited at LHC by experimental

mass resolution of O(1) GeV (CMS: ΓH < 3 GeV in H → γγ, but note that ΓH,SM ≈ 4 MeV)

• All resonant Higgs cross sections depend on ΓH , therefore ΓH and couplings cannot be

determined at the LHC (on-peak) without theoretical assumptions M. Duhrssen et al. (2004),

LHC Higgs Cross Section WG (2012)

• For broad class of models, assuming upper limit for HWW or HZZ coupling (e.g. SM)

→ upper bound for ΓH (ΓH = O(ΓH,SM )) M. Peskin (2012); B. Dobrescu, J. Lykken (2013)

• Assuming no BSM Higgs decays, and Higgs coupling parameterisations, can fit Higgs

width to data and agreement with SM Higgs width is found J. Ellis, You (2013)

• e+e− → Z(H → all): construct recoil mass and measure HZZ coupling → ΓH can be

determined indirectly, ILC: 6%–11% accuracy T. Han et al. (2013), M. Peskin (2013)

• Direct threshold scan at muon collider: ΓH accuracy 4%–9% T. Han, Z. Liu (2013)

• Higgs width determination could provide first evidence for BSM Higgs interactions


High-mass Higgs signal and Higgs width determination

indirect Higgs width determination via on- and off-peak Higgs cross section

F. Caola, K. Melnikov (2013)

|Mi→H→f |2 =|Mi|2 |Mf |2

|p2H −M2H + iMHΓH |2

resonance contribution to signal cross section (“on-peak”): σi→H→fNWA∝

g2i g2f

ΓH

NWA scaling degeneracy: σ unchanged if gi → ξ gi, gf → ξ gf , ΓH → ξ4 ΓH

√

p2H −MH ≫ O(ΓH) → p2H −M2H ≫ MHΓH → |Mi→H→f |2 ≈ |Mi|2 |Mf |2

|p2H −M2H |2

off-resonance contribution (“off-peak”): σi→H→f

(

√

p2H −MH ≫ O(ΓH)

)

∝ g2i g2f

sizeable off-resonance contribution to signal cross section is independent of Higgs width,

and therefore “breaks” NWA scaling degeneracy: σoff-peak/σon-peak ∝ ΓH

competitive constraints on Higgs width without assumptions(?) feasible with LHC data

large interference with cont. background (necessary to prevent unitarity violation) weakens bounds


MCFM analysisJ. Campbell, K. Ellis, C. Williams (2013) (update of Caola-Melnikov analysis)

CMS Higgs selection cuts are applied:

pTℓ1 > 20GeV, pTℓ2 > 10GeV, pTe > 7GeV, pTµ > 5GeV, |ηµ| < 2.4, |ηe| < 2.5, Mℓℓ > 4GeV,

M4ℓ > 100GeV, 40 GeV < Mℓℓ,closest < 120GeV, 12 GeV < Mℓℓ,other < 120GeV (relative to MZ )

Best prediction cross sections for pp → H → ZZ → e−e+µ−µ+ in fb, obtained

using the running scale m4ℓ/2:

m4ℓ > 130 GeV m4ℓ > 300 GeV

Energy PDF σHpeak σH

off σIoff σH

off σIoff

7 TeV MSTW 0.203 0.025 -0.053 0.017 -0.025

CTEQ 0.192 0.021 -0.047 0.015 -0.021

8 TeV MSTW 0.255 0.034 -0.073 0.025 -0.036

CTEQ 0.243 0.031 -0.065 0.022 -0.031

13 TeV MSTW 0.554 0.108 -0.215 0.085 -0.122

CTEQ 0.530 0.100 -0.199 0.077 -0.111

H

g

g

q

V

V

q

q

V

V

g

g

q

V

V


MCFM analysisFor σoff = σH

off + σIoff with

√s = 8 TeV and MSTW PDF set:

σoff (m4ℓ > 130 GeV) = 0.034

(ΓH

ΓSMH

)

︸︷︷︸Higgs signal

−0.073

√

ΓH

ΓSMH

︸︷︷︸interference

σoff (m4ℓ > 300 GeV) = 0.025

(ΓH

ΓSMH

)

− 0.036

√

ΓH

ΓSMH

Normalising to the number of events observed at the peak one can estimate number of

Higgs-related off-peak events (properly combining 7 and 8 TeV data used in CMS H →ZZ → 4ℓ analysis):

N4ℓoff (m4ℓ > 130 GeV) = 2.78

(ΓH

ΓSMH

)

− 5.95

√

ΓH

ΓSMH

N4ℓoff (m4ℓ > 300 GeV) = 2.02

(ΓH

ΓSMH

)

− 2.91

√

ΓH

ΓSMH

Second term accounts for interference between gg → H → ZZ → 4ℓ (Higgs signal amplitude) and

gg → ZZ → 4ℓ (continuum background amplitude)


MCFM analysisHiggs width bounds from cut-based analysis

Using event number observed in off-peak region (451) and number expected from

continuum background only (431± 31):

ΓH < 43.2ΓSMH (95% CL), (m4ℓ > 130 GeV analysis)

ΓH < 25.2ΓSMH (95% CL), (m4ℓ > 300 GeV analysis)

Method can be applied to H → WW channel (MT ), comparable bounds appear feasible MCFM (2013)


MCFM analysisHiggs width bounds from matrix element method (H → ZZ)Matrix element method: optimize discrimination using fully differential information

Associate probabilistic weight with each event:

P (φ) =1

σ

∑

i,j

∫

dx1dx2 δ(x1x2s−Q2)fi(x1)fj(x2)σij(x1, x2, φ)

Pqq : qq induced continuum background

Pgg : gg induced contributions

(incl. Higgs signal, cont. bkg. & interf.)

PH : gg induced Higgs amplitude squared

Discriminant:

DS = log

(PH

Pgg + Pqq

)

SD

5 4 3 2 1 0 1 2 3 4 5

S /

d D

σd

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

=10)4ξ (H

σ

C

σ

=10) 4ξ (H+C

σ

ΓH <(15.7−2.9

+3.9

)ΓSMH (95% CL), (DS > 1) bound 1.6 × better than for m4ℓ > 300 GeV


CMS analysis

arXiv:1405.3455 (May 2014)improvements:

• include 2ℓ2ν final states

• include VBF channel (contributes ∼ 7% on peak, and O(10%) above 2MZ )

• include known QCD and EW corrections F. Caola, T. Kasprzik, G. Passarino, M. Zaro et al.

• slightly different kinematic discriminant (PH → Pgg), backgrounds fully considered

ΓH < 5.4 ΓSMH (95% CL)


ATLAS analysisarXiv:1503.01060 (July 2014, March 2015)

improvements:

• similar to CMS, thorough consideration of systematic uncertainties

• provide results as function of the unknown gg → ZZ background K-factor,

variation: [0.5, 2]× signal K-factor

• off-shell signal strength 95%-CL upper limit [5.1, 8.6] ([6.7, 11] expected)

ME Discriminant

-4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5

Events

/ 0

.2

0

10

20

30

40

50

Data

syst)⊕SM (stat

=10)off-shell

µTotal (

) ZZ →(H*→gg+VBF

ZZ→qBackground q

tBackground Z+jets, t

ATLAS

4l→ ZZ →H

-1Ldt = 20.3 fb∫ = 8 TeV: s

HSMΓ/HΓ

0 2 4 6 8 10Λ

-2ln

0

2

4

6

8

10

12

14 ATLAS

g/V,off-shellκ=g/V,on-shellκZZ+WW off-shell+on-shell→H

-1Ldt = 20.3 fb∫ = 8 TeV: s

observed with syst.

observed no syst.

expected with syst.

expected no syst.

ΓH < [4.5, 7.5] ΓSMH (95% CL)


Higgs (width) constraints from vector boson fusion

J.M. Campbell, R.K. Ellis (2015), arXiv:1502.02990

(see also C. Englert, M. Spannowksy (2014) arXiv:1405.0285)

ΓH < 61 ΓSMH (LHC Run 1)

ΓH < 4.4 ΓSMH (LHC 100 fb−1 data)

ΓH < 3.2 ΓSMH (LHC 300 fb−1 data)


Model builder’s considerations, BSM searches

Constraining higher dimensional operators with the off-shell Higgs

Limitations of model-independence

Disentangling New Physics with the off-shell Higgs boson

EFT studies including the off-shell Higgs boson

J. Gainer, J. Lykken, K. Matchev, S. Mrenna, M. Park (2014); C. Englert, M. Spannowsky (2014);

M. Ghezzi, G. Passarino, S. Uccirati (2014); G. Cacciapaglia, A. Deandrea, G. Drieu La Rochelle,

J. Flament (2014); A. Azatov, C. Grojean, A. Paul, E. Salvioni (2014); A. Biekoetter, A. Knochel, M.

Kraemer, D. Liu, F. Riva (2014)

g

g

Hφ

φ

φ

g

g

H

φ

φ0.70.60.50.40.30.20.1

10

1

10−1

10−2

10−3

10−4

10−5

3,mϕ = 400 GeV3,mϕ = 65 GeV

ggh, mt,mb

ggh, mt → ∞ggZZ, mq

√s = 8 TeV

2mt

m(4ℓ) [TeV]

dσ/d

m(4

ℓ)[a

b/2

0G

eV]

C. Englert, M. Spannowsky (2014)


BSM benchmark scenario studies

0.80.70.60.50.40.3

1000

100

10

1

0.1

0.01

mt ≃ 300 GeV, low MSUSY

mt ≃ 300 GeVmt ≃ 170 GeV, low MSUSY

mt ≃ 170 GeVdecoupling

√s = 13 TeV

m(4ℓ) [TeV]

dσ/d

m(4

ℓ)[a

b/2

0G

eV]

10.90.80.70.60.50.40.30.20.1

100

10

1

0.1

0.01

0.001

continuumh + φ signals

φ signalh signal

full√

s = 13 TeV

2mt

m(4ℓ) [TeV]

dσ/d

m(4

ℓ)[a

b/2

0G

eV]

left: MSSM, right: portal-extended SM model

C. Englert, Y. Soreq, M. Spannowsky (2014)

also: C. Englert, I. Low, M. Spannowsky (2015)


Loophole: additional light scalar in the s-channel [H.E. Logan, 1412.7577]

h H

SM: h cancels growth ∝ E/v of tt → ZZ amplitude.

Modified h couplings: cancellation imperfect; growth of amplitude with E provides

LHC sensitivity at high mZZ !

Extended Higgs sector: Require κht κ

hZ + κH

t κHZ = 1 for unitarity of tt → ZZ

(automatic in renormalizable models): κht κ

hZ = 1 +∆ > 1, κH

t κHZ = −∆

Amplitude relative to SM:

Mh +MH

MhSM

= (1 +∆)−∆p2 −m2

h

p2 −m2H

≃ 1−∆(m2

H −m2h)

p2

→ 1 for p2 ≫ m2h,H

-1

0

1

2

3

4

200 300 400 500 600 700 800 900 1000

Sca

lar-

exch

an

ge

am

plit

ud

e (

no

rma

lize

d t

o S

M)

mZZ [GeV]

SMh only

mH = 150 GeVmH = 225 GeVmH = 300 GeV

Presence of H at low mass (well below 350 GeV) causes gg → ZZ cross section

to be SM-like at high mZZ , even if κht κ

hZ is strongly non-SM-like.


Higgs width via interferometry in gg → H → γγ

S. Martin (2012) (proposal and LO analysis)

Higgs signal continuum background interference induces sizeable peak shift in gg → H →γγ (but negligible in gg → H → ZZ∗)

124.95 125 125.05Mγγ [GeV]

-100

-50

0

50

100

dσ

/dM

γγ [fb

/GeV

]

110 115 120 125 130 135 140Mγγ [GeV]

-0.2

-0.1

0.0

0.1

0.2

dσ

int/d

Mγγ

[

fb/G

eV

]

1.3 GeV1.5 GeV1.7 GeV2.0 GeV2.4 GeV

σMR

=

122 123 124 125 126 127 128

Mγγ [GeV]

0.0

1.0

2.0

3.0

dσ

/dM

γγ

[fb

/Ge

V]

left fig.: interference contribution (real term) before detector resolution effects

center fig.: interference contribution (real term) for different mass resolutions (Gaussian, σMR)

right fig.: peak shift of invariant mass distribution (σMR = 1.7 GeV): ∆Mγγ = −120 MeV at LO

(H → γγ)+jet at LO: negligible mass peak shift (< 20 MeV for pTj > 25 GeV)

Daniel de Florian, et al. (2013); S. Martin (2013)


Higgs width via interferometry in gg → H → γγL. Dixon, Y. Li (2013) (NLO analysis)

120 122 124 126 128 130

0

1

2

3

4

MΓΓ @GeVD

dΣ

sig�d

MΓΓ@f

b�G

eVD

Higgs Signal � NLO HggL

Higgs Signal � LO HggL

NLO (gg): +

+ +

LO (gg): H LO (qg):

120 122 124 126 128 130

-0.10

-0.05

0.00

0.05

0.10

MΓΓ @GeVD

dΣ

int �

dMΓΓ@f

b�G

eVD

Interference � NLO HggL

Interference � LO HqgL

Interference � LO HggL

0 5 10 15 20-400

-300

-200

-100

0

100

200

300

GH �GH

SM

DM

H�

MeV

Constructive Interf.

Destructive Interf. HSML

SM mass shift: ∆Mγγ = −70 MeV at NLO

Vary Higgs width and couplings (maintaining on-peak SM signal strenghts):

ΓH < 15 ΓSMH (14 TeV, 3 ab−1, 95% CL)


BSM dependence of H → γγ mass peak shift?

124.95 125 125.05Mγγ [GeV]

-100

-50

0

50

100

dσ

/dM

γγ [fb

/GeV

]

110 115 120 125 130 135 140Mγγ [GeV]

-0.2

-0.1

0.0

0.1

0.2

dσ

int/d

Mγγ

[

fb/G

eV

]

1.3 GeV1.5 GeV1.7 GeV2.0 GeV2.4 GeV

σMR

=

122 123 124 125 126 127 128

Mγγ [GeV]

0.0

1.0

2.0

3.0

dσ

/dM

γγ

[fb

/Ge

V]

Higgs resonance - BSM continuum interference effects?

new feature: BSM EW light degrees of freedom active in loop-induced H → γγ decay?


EFT analysis of on- and off-shell H → ZZ → 4ℓ dataA. Azatov, C. Grojean, A. Paul, E. Salvioni (2014)

(see also G. Cacciapaglia, A. Deandrea, G. Drieu La Rochelle, J. Flament (PRL 2014))

ct

g

g

Z

Z

g

gZ

Z

cg

g

g

Z

Z

L = −ctmt

vtth+

g2s48π2

cgh

vGµνG

µν

Mgg→ZZ = Mh +Mbkg = ct Mct + cg Mcg +Mbkg

σ ∼ |ct + cg |2: on-shell degeneracy ct + cg = const is broken by far-off-shell data

Constraints in (ct, cg) plane (68%, 95% and 99% probability contours): (not MELA improved!)

LHC 8 TeV CMS data LHC 14 TeV 3 ab−1 data


Effective ggH coupling: boosted v. off-shell Higgs sensitivity

]-1

L [fb200 400 600 800 1000 1200 1400 1600 1800 2000

s

CL

0.001

0.01

0.1

T,H, p

jetsExclusion plot based on n

95% exclusion

σ1 σ2

expected 95% CL

=(0.7,0.3)tgk

WW→H

]-1

L [fb500 1000 1500 2000 2500 3000

s

CL

0.001

0.01

0.1

4l and meθExclusion plot based on cos

95% exclusion

σ1 σ2

expected 95% CL

=(0.7,0.3)tgk

ZZ→gg

left: boosted analysis, right: off-shell analysis (not MELA improved)

M. Buschmann, D. Goncalves, S. Kuttimalai, M. Schoenherr, F. Krauss, T. Plehn (2014) (1410.5806)


Interference for semileptonic H decay modes in ggF

Charged currents (representative Feynman graphs)

gg → H → W−W+ → ℓνqq′ (and c.c.)

W−

W+

ℓ

νq

q′

H

g

g

q

ν

ℓ

g

g

q′

q

W−

ℓ

νq

q′g

g

q

W−

W+

signal loop background tree background

new feature of signal-background interference: O(e2) tree-level graphs contribute

part of pp → (W → ℓν)+2 jet @ LO and pp → W → ℓν @ NNLO

Similarly: Neutral currents (representative Feynman graphs)

gg → H → ZZ → ℓℓqq

ℓ

ℓq

qg

g

q

Z, γ∗

ℓ

ℓq

q

H

g

g

q

ℓ

ℓ

g

g

q

q

Z, γ∗

Z, γ∗

Z, γ∗

Z, γ∗

signal loop background tree background

tree background part of pp → (Z → ℓℓ)+2 jet @ LO and pp → Z → ℓℓ @ NNLO



Parton-level signal processes

gg → H → W−W+ → ℓνℓquqd

gg → H → W+W− → ℓνℓquqd

gg → H → ZZ → ℓℓququ

gg → H → ZZ → ℓℓqdqd

(Note: for crossed processes: t-channel Higgs propagator)

Input parameters and settings

pp,√s = 8 TeV, MH = 125.5 GeV, µR = µF = 0.5MV V , other: default settings of

gg2VV-3.1.6

Selection cutsminimal cuts (“min. cuts”): pTj > 4 GeV, for ZZ also: Mqq > 4 GeV, Mℓℓ > 4 GeV

LHC cuts: minimal cuts & pTℓ > 20 GeV, |ηℓ| < 2.5, pTj > 25 GeV, |ηj | < 4.5, for WWalso: p/T > 20 GeV

background suppression cuts (“bkg. cuts”): note: here MH = 400GeV

LHC cuts & |Mjj −MV | < 5ΓV , pTj,1st > 60 GeV and pTj,2nd > 40 GeV, |ηj | < 2.8,

∆Rjj < 1.3 ATLAS arXiv:1206.6074

no jet clustering, technical cut: pTV > 1 GeV to exclude numerical instabilities → ≈ 0.3% uncertainty on σ



Integrated results

using standard multi-channel phase space sampling and FeynArts/FormCalc/LoopTools adapted amplitude code, various tests

amplitudes validated with independent implementation in MG5-MadLoop, validation of integrated results in progress (Vryonidou)

W−

W+

ℓ

νq

q′

H

g

g

q

ν

ℓ

g

g

q′

q

W−

ℓ

νq

q′g

g

q

W−

W+

M = Msignal (LO) +Mbackground = Msignal +Mloop +Mtree

Notation for amplitude contributions to cross sections:

S ∼ |Msignal|2

Itree ∼ 2Re(M∗signal Mtree)

Iloop ∼ 2Re(M∗signal Mloop)

Ifull ∼ 2Re(M∗signal Mbackground)

Mloop contains all closed quark loop graphs. (NLO EW corrections to Itree not included.)

relative measure for interf. with bkg. i: Ri =σ(|Msignal|2 + 2Re(M∗

signalMi))

σ(|Msignal|2)



NK, C. O’Brien, E. Vryonidou (gg2VV and MG5 aMC@NLO)

Integrated results

gg → H → W−W+ → ℓνℓquqdσ [fb], pp,

√s = 8 TeV interference ratio

cuts S Itree Iloop Ifull Rtree Rloop Rfull

min. 67.3(4) –2.48(2) –4.99(5) –7.42(7) 0.963(7) 0.926(7) 0.890(7)

LHC 1.96(1) 0.269(3) –2.65(3) –2.38(2) 1.137(8) –0.35(1) –0.21(1)

bkg. 13.29(7) –0.0062(6) –1.03(1) –1.04(1) 1.000(7) 0.922(7) 0.922(7)

gg → H → W+W− → ℓνℓquqdσ [fb], pp,



min. 67.2(4) –2.47(2) –4.99(5) –7.47(7) 0.963(7) 0.926(7) 0.889(7)

LHC 1.96(1) 0.270(3) –2.65(3) –2.38(2) 1.138(8) –0.35(1) –0.21(1)

bkg. 13.30(7) –0.0055(9) –1.03(1) –1.04(1) 1.000(7) 0.922(7) 0.922(7)



Integrated results

gg → H → ZZ → ℓℓququσ [fb], pp,



min. 1.96(1) –0.190(4) –0.343(3) –0.541(5) 0.903(7) 0.825(7) 0.724(7)

LHC 0.1166(6) 0.017(2) –0.194(2) –0.176(6) 1.15(2) –0.67(2) –0.51(5)

bkg. 1.342(7) –0.0012(2) –0.0882(9) –0.0892(9) 0.999(7) 0.934(7) 0.934(7)

gg → H → ZZ → ℓℓqdqdσ [fb], pp,



min. 2.51(2) –0.248(3) –0.439(6) –0.680(7) 0.901(7) 0.825(7) 0.729(7)

LHC 0.1497(8) 0.0223(6) –0.245(5) –0.227(3) 1.149(9) –0.64(3) –0.52(2)

bkg. 1.720(9) –0.00130(5) –0.113(1) –0.114(1) 0.999(7) 0.934(7) 0.934(7)



Differential results

0

0.2

0.4

0.6

0.8

1

0 100 200 300 400 500 600 700 800

MWW [GeV]

gg → H → W−W+ → ℓνℓqdqu

MH = 125.5 GeVpp,

√s = 8 TeV

min. cuts

dσ/d

MW

W[fb/G

eV] S + Ibkg,tree

S + Ibkg,full

S

-0.02

0

0.02

0.04

0.06

0.08

0.1

0 100 200 300 400 500 600 700 800

MWW [GeV]


MH = 125.5 GeVpp,

√s = 8 TeV

LHC cuts

dσ/d

MW

W[fb/G

eV] S + Ibkg,tree

S + Ibkg,full

S

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 100 200 300 400 500 600 700 800 900

MWW [GeV]


MH = 400 GeVpp,

√s = 8 TeV

bkg. cuts

dσ/d

MW

W[fb/G

eV] S + Ibkg,tree

S + Ibkg,full

S

0

2

4

6

8

10

0 20 40 60 80 100 120 140

Mℓν [GeV]


MH = 125.5 GeVpp,

√s = 8 TeV

min. cuts

dσ/d

Mℓν

[fb/G

eV] S + Ibkg,tree

S + Ibkg,full

S

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0 20 40 60 80 100 120 140 160

Mℓν [GeV]


MH = 125.5 GeVpp,

√s = 8 TeV

LHC cuts

dσ/d

Mℓν

[fb/G

eV] S + Ibkg,tree

S + Ibkg,full

S

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 20 40 60 80 100 120 140 160

Mℓν [GeV]


MH = 400 GeVpp,

√s = 8 TeV

bkg. cuts

dσ/d

Mℓν

[fb/G

eV] S + Ibkg,tree

S + Ibkg,full

S




0

0.5

1

1.5

2

2.5

0 50 100 150 200 250 300

pT (ℓ) [GeV]


MH = 125.5 GeVpp,

√s = 8 TeV

min. cuts

dσ/d

pT(ℓ

)[fb/G

eV] S + Ibkg,tree

S + Ibkg,full

S

-0.05

0

0.05

0.1

0.15

0.2

0.25

0 50 100 150 200 250 300

pT (ℓ) [GeV]


MH = 125.5 GeVpp,

√s = 8 TeV

LHC cuts

dσ/d

pT(ℓ

)[fb/G

eV] S + Ibkg,tree

S + Ibkg,full

S

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0 50 100 150 200 250 300

pT (ℓ) [GeV]


MH = 400 GeVpp,

√s = 8 TeV

bkg. cuts

dσ/d

pT(ℓ

)[fb/G

eV] S + Ibkg,tree

S + Ibkg,full

S

0

5

10

15

20

-4 -2 0 2 4

ηℓ


MH = 125.5 GeVpp,

√s = 8 TeV

min. cuts

dσ/d

η ℓ[fb] S + Ibkg,tree

S + Ibkg,full

S

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

-4 -2 0 2 4

ηℓ


MH = 125.5 GeVpp,

√s = 8 TeV

LHC cuts

dσ/d


S + Ibkg,full

S

0

1

2

3

4

5

-4 -2 0 2 4

ηℓ


MH = 400 GeVpp,

√s = 8 TeV

bkg. cuts

dσ/d


S + Ibkg,full

S


Heavy Higgs - light Higgs - background interference

consider a heavy Higgs h2 (signal) in addition to a light Higgs h1 at 125 GeV (background)

Two-Higgs model: SM & real EW singlet scalar, as defined in YR3 arXiv:1307.1347, Sec. 13.3

1e-08

1e-06

0.0001

0.01

1

100

10000

100 200 300 400 500 600

MZZ [GeV]

gg → H → ZZ → ℓℓνℓνℓ, MH=125GeV

pp,√s = 8TeV

gg2VV

dσ/d

MZZ

[fb/GeV

]

|H|2+|cont|2|H+cont|2Hoffshell

HZWA

100 500 600 700 800 1000

10−5

10−4

10−3

10−2

10−1

1 HTO powered by complex - pole - scheme 8 TeV

pZ

⊥> 0.25 MZZ

400↓

500↓600

↓700ց

↓800

MZZ [ GeV]

Bdσ

dM

ZZ

[fb

/G

eV]

centre fig.: NK (arXiv:1201.1667, backup slides) right fig.: G. Passarino (arXiv:1206.3824)

What is the impact of interference with the off-shell tail of the 125 GeV Higgs

for a heavy Higgs of 300, 600 or 900 GeV?

S ∼ |Mh2|2

Ih1 ∼ 2Re(M∗

h2 Mh1)

Ibkg ∼ 2Re(M∗

h2 Mbkg)

Ifull ∼ 2Re(M∗

h2 (Mh1 + Mbkg))

Two-Higgs model details: θ = π/8 (σh1 ≈ σH,SM up to 20%), Γh1 = 4.2577 · 10−3 GeV for Mh1 = 125 GeV,

Γh2 = 1.70204 (20.7236) [69.1805] GeV for Mh2 = 300 (600) [900] GeV



NK, C. O’Brien arXiv:1502.04113 (gg2VV)

Integrated results

gg → h2 → W−W+ → ℓνℓ′ν′

min. cuts

σ [fb], pp,√s = 8 TeV interference ratio

Mh2 [GeV] S Ih1 Ibkg Ifull Rh1 Rbkg Rfull

300 1.4144(6) 0.1173(3) –0.0453(5) 0.0730(4) 1.0829(7) 0.9679(7) 1.0516(7)

600 0.18744(7) –0.0558(2) 0.0942(2) 0.03882(7) 0.7025(8) 1.503(1) 1.2071(7)

900 0.017991(7) –0.03500(3) 0.04957(4) 0.01468(2) –0.945(2) 3.755(3) 1.816(2)

gg → h2 → W−W+ → ℓνℓ′ν′

min. cuts & |MV V − Mh2| < Γh2



300 0.98(2) 0.00033(4) 0.03431(8) 0.03464(9) 1.00(2) 1.03(2) 1.04(2)

600 0.135(2) –0.00183(3) 0.01584(4) 0.01401(4) 0.99(2) 1.12(2) 1.10(2)

900 0.01288(2) –0.001343(5) 0.00432(3) 0.00298(3) 0.896(2) 1.335(3) 1.231(3)



Integrated results

gg → h2 → ZZ → ℓℓℓ′ ℓ′

min. cuts



300 0.12609(5) 0.01187(3) 0.00358(4) 0.01545(5) 1.0941(6) 1.0284(6) 1.1225(7)

600 0.018199(7) –0.00506(2) 0.00571(2) 0.00064(2) 0.7217(8) 1.3135(9) 1.035(2)

900 0.0017746(7) –0.003296(4) 0.003403(3) 0.000107(5) –0.857(3) 2.918(2) 1.060(3)

gg → h2 → ZZ → ℓℓℓ′ ℓ′

min. cuts & |MV V − Mh2| < Γh2



300 0.0879(2) 4.0(4)e–05 0.00547(2) 0.00551(2) 1.000(2) 1.062(2) 1.063(2)

600 0.01318(2) –0.00020(2) 0.001045(7) 0.00084(2) 0.985(3) 1.079(3) 1.064(3)

900 0.001273(2) –0.000130(2) 0.000373(2) 0.000243(3) 0.898(3) 1.293(3) 1.191(3)




-0.001

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

200 300 400 500 600 700 800 900 1000 1100

MWW [GeV]

gg → h2 → W−W+ → ℓνℓ′ν′

Mh2 = 600 GeV Mh1 = 125 GeVpp,

√s = 8 TeV

min. cuts

dσ/d

MW

W[fb/G

eV] S + Ih1

S + Ih1 + Ibkg

S (h2)

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

200 300 400 500 600 700 800 900 1000 1100

MWW [GeV]

gg → h2 → W−W+ → ℓνℓ′ν′


√s = 8 TeV

min. cuts

dσ/d

MW

W[fb/G

eV] S + Ih1

S + Ih1 + Ibkg

S (h2)

0

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

0.0014

200 300 400 500 600 700 800 900 1000 1100

MZZ [GeV]

gg → h2 → ZZ → ℓℓℓ′ℓ′


√s = 8 TeV

min. cuts

dσ/d

MZ

Z[fb/G

eV] S + Ih1

S + Ih1 + Ibkg

S (h2)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

200 300 400 500 600 700 800 900 1000 1100

MZZ [GeV]



√s = 8 TeV

min. cuts

dσ/d

MZ

Z[fb/G

eV] S + Ih1

S + Ih1 + Ibkg

S (h2)




0.0001

0.001

0.01

0.1

1

200 250 300 350 400 450

MWW [GeV]

gg → h2 → W−W+ → ℓνℓ′ν′


√s = 8 TeV

min. cuts

dσ/d

MW

W[fb/G

eV] S + Ih1

S + Ih1 + Ibkg

S (h2)

1e-06

1e-05

0.0001

0.001

0.01

0.1

1

200 300 400 500 600 700 800 900 1000 1100

MWW [GeV]

gg → h2 → W−W+ → ℓνℓ′ν′


√s = 8 TeV

min. cuts

dσ/d

MW

W[fb/G

eV] S + Ih1

S + Ih1 + Ibkg

S (h2)

1e-06

1e-05

0.0001

0.001

0.01

200 400 600 800 1000 1200 1400 1600

MWW [GeV]

gg → h2 → W−W+ → ℓνℓ′ν′


√s = 8 TeV

min. cuts

dσ/d

MW

W[fb/G

eV] S + Ih1

S + Ih1 + Ibkg

S (h2)

0.0001

0.001

0.01

0.1

200 250 300 350 400 450

MZZ [GeV]



√s = 8 TeV

min. cuts

dσ/d

MZ

Z[fb/G

eV] S + Ih1

S + Ih1 + Ibkg

S (h2)

1e-09

1e-08

1e-07

1e-06

1e-05

0.0001

0.001

0.01

0.1

200 300 400 500 600 700 800 900 1000 1100

MZZ [GeV]



√s = 8 TeV

min. cuts

dσ/d

MZ

Z[fb/G

eV] S + Ih1

S + Ih1 + Ibkg

S (h2)

1e-07

1e-06

1e-05

0.0001

0.001

200 400 600 800 1000 1200 1400 1600

MZZ [GeV]



√s = 8 TeV

min. cuts

dσ/d

MZ

Z[fb/G

eV] S + Ih1

S + Ih1 + Ibkg

S (h2)


Heavy Higgs interference in VBF

similar study for VBF (SM-like light & heavy Higgs)

[GeV]WWm

200 400 600 800 1000 1200

[fb

/GeV

]W

W/d

mσ

d

0

0.0005

0.001

0.0015

0.002

0.0025

0.003=800 GeV

HM

=600 GeVH

M

=126 GeVH

M

=100 GeVH

M

LH

C H

IGG

S X

S W

G 2

013

[GeV]WWm

200 400 600 800 1000 1200 1400

[fb

/GeV

]W

W/d

mσ

d

0

0.01

0.02

0.03

0.04

0.05 POWHEG CPSVBFNLO REPOLO

LH

C H

IGG

S X

S W

G 2

013

figures taken from YR3 arXiv:1307.1347, Sec. 12.4

Michael Rauch, Franziska Schissler (VBFNLO)

left: SM Higgs with MH including continuum background and interference

right: heavy SM Higgs signal only (blue),

blue plus interference with cont. bkg. & light SM Higgs (red)

standard VBF cuts & LHC detector acceptance cuts are applied

→ Michael Rauch’s talk for additional related results


High-mass H → V V signal at a linear collider

S. Liebler, G. Moortgat-Pick, G. Weiglein (2014), arXiv:1502.07970

e+

e−

νV (∗)

V

ν

W

W HH

e+

e−

ν

W+

W−

ν

W

W

e+

e−

Z

V

V (∗)

H

200 400 600 800 1000

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

mZZ [GeV]

dσ/dm

ZZ

[fb/G

eV]

e+e− → ννZZ√

s = 1 TeV

Pol(e+, e−) = (0.3,−0.8)

100 200 300 400 500

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

mZZ [GeV]

dσ/d

mZ

Z[fb/G

eV]


s = 350 GeV

Pol(e+, e−) = (0.3,−0.8)

100 200 300 400 500

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

mZZ [GeV]

dσ/d

mZ

Z[fb/G

eV]


s = 500 GeV

Pol(e+, e−) = (0.3,−0.8)


High-mass H → V V signal at a linear colliderS. Liebler, G. Moortgat-Pick, G. Weiglein (2014), arXiv:1502.07970

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mWW [GeV]

dσ/dm

WW[fb/G

eV]

e+e− → ννWW√s = 1TeV

Pol(e+, e−) = (0.3,−0.8)

100 200 300 400 500

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mWW [GeV]dσ/dm

WW[fb/G

eV]

e+e− → ννWW√s = 350GeV

Pol(e+, e−) = (0.3,−0.8)

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mWW [GeV]

dσ/dm

WW[fb/G

eV]

e+e− → ννWW√s = 500GeV

Pol(e+, e−) = (0.3,−0.8)

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mWW [GeV]

dσ/d

mW

W[fb/G

eV]

e+e− → ZWW√

s = 250 GeV

Pol(e+, e−) = (0.3,−0.8)

100 200 300 400 500

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mWW [GeV]

dσ/d

mW

W[fb/G

eV]

e+e− → ZWW√

s = 350 GeV

Pol(e+, e−) = (0.3,−0.8)

100 200 300 400 500

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mWW [GeV]dσ/d

mW

W[fb/G

eV]

e+e− → ZWW√

s = 500 GeV

Pol(e+, e−) = (0.3,−0.8)


Heavy Higgs-light Higgs interference at a linear collider

S. Liebler, G. Moortgat-Pick, G. Weiglein (2014), arXiv:1502.07970

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mZZ [GeV]

dσ/dm

ZZ[fb/G

eV]

e+e− → ννZZ,√s = 1TeV

Pol(e+, e−) = (0.3,−0.8)

2HDM, sβ−α = 0.99/0.98/0.95mh = 125GeV, mH = 400GeV

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mZZ [GeV]

dσ/dm

ZZ[fb/G

eV]

e+e− → ννZZ,√s = 1TeV

Pol(e+, e−) = (0.3,−0.8)

2HDM, sβ−α = 0.99/0.98/0.95mh = 125GeV, mH = 600GeV


LHC-HXSWG: Yellow Report 4 projects

• validation of automatised (event) generation for all gg (→ H) → V V → fff fprocesses at LO

• work on tools for pp (→ H) → V V +jet(s) at NLO incl. gg-type at LO and PS merging

(Sherpa+OpenLoops, 1309.0500)

• NLO gg → ZZ,WW calculation (with finite quark mass effects)

• NNLO pp → V V tools

• explore mitigating high mass model dependence using LHC Run 2 data

• ggF & VBF heavy Higgs searches (interference effects)

• anomalous off-shell coupling studies (discuss further with WG2)

• additional high-mass ZZ EFT studies (discuss further with WG2)

• studies for BSM benchmark scenarios (discuss with WG3)

• automatised tools for EFT and BSM benchmark analyses

• enhanced H → γγ peak shift analysis & model dependence studies

• thorough assessment of what value is added by off-shell/interference enabled Higgs

analyses compared to on-shell analyses is desirable in the medium term


Summary• H → ZZ,WW in ggF & VBF @ LHC: O(10%) high-mass Higgs signal contribution with

large Higgs(-Higgs)-continuum interference: now taken into account, provides

complementary physics information (similar at high-energy linear collider)

• gg → H → ZZ,WW → 2ℓ2ℓ, 4ℓ, 2ℓ2ν: interference studied in great detail,

tools & events available (caveat: LO); NLO calculation: very hard, in progress

• First analysis of interference (& Higgs width bounds) for pp → H → ZZ + jet

• Semileptonic channels gg → H → WW → ℓνqq′ and gg → H → ZZ → ℓℓqqcontribute to ongoing (heavy) Higgs analyses; first analysis of interference effects in

semileptonic channels, new feature: interfering tree-level background

• First analysis of heavy Higgs-light Higgs-bkg. interference effects in gg → H → V V ,

complementary studies for VBF and linear collider

• Direct Higgs width measurement at LHC limited by mass resolution: ΓH . 750 ΓSMH

• high-mass Higgs tail not Higgs width dependent → provides complementary constraints on

Higgs width ΓH and Higgs couplings

• Assuming no E-dependence of relevant Higgs couplings, a bound on ΓH can be

obtained; optimise bound with fully differential discriminant (Matrix Element Method)

• LHC Run 1: CMS: ΓH < 5.4 ΓSMH , ATLAS: ΓH < [4.5, 7.5] ΓSM

H (95% CL)

• H → γγ: interference-facilitated bound ΓH < 15 ΓSMH (14 TeV, 3 ab−1, 95% CL)

• LHC Run 2: improved bounds (ggF & VBF), high-mass H → V V EFT and BSM benchmark

studies


Backup Slides

Signal-background interference for MH = 400 GeV

gg (→ H) → W−W+ → lνl l′νl′ and gg (→ H) → ZZ → lll′ l′

Settings and cuts

µR = µF = MH/2 = 200 GeV, ΓH = 29.16 GeV (HDECAY)

MSTW2008LO (68% C.L.), other: LHC Higgs Cross Section WG,

arXiv:1101.0593 [hep-ph], App. A (with NLO ΓV and Gµ scheme)

WW standard cuts:

pTℓ > 20 GeV , |ηℓ| < 2.5

p/T > 30 GeV , Mℓℓ′ > 12 GeV

WW Higgs search cuts (MH = 400 GeV): standard cuts and

pTℓmin > 25 GeV , pTℓmax > 90 GeV

Mℓℓ′ < 300 GeV , ∆φℓℓ′ < 175◦

ZZ standard cuts:

pTℓ > 20 GeV , |ηℓ| < 2.5

76 GeV < Mℓℓ,Mℓ′ ℓ′ < 106 GeV

ZZ Higgs search cuts: standard cuts and

|Mlll′ l′ −MH | < ΓH


Integrated results

σ [fb], pp,√s = 7 TeV, MH = 400 GeV interference

process cuts |MH |2 |Mcont|2 |MH +Mcont|2 R1 R2

gg (→ H) → WW stand. 4.361(3) 6.351(4) 10.582(7) 0.9879(8) 0.970(2)

gg (→ H) → WW Higgs 2.502(2) 0.633(1) 3.007(3) 0.959(2) 0.949(2)

gg (→ H) → ZZ stand. 0.3654(4) 0.3450(4) 0.7012(8) 0.987(2) 0.975(3)

gg (→ H) → ZZ Higgs 0.2729(3) 0.01085(2) 0.2867(3) 1.010(2) 1.011(2)

σ [fb], pp,√s = 14 TeV, MH = 400 GeV interference

process cuts |MH |2 |Mcont|2 |MH +Mcont|2 R1 R2

gg (→ H) → WW stand. 23.38(2) 26.47(2) 48.26(4) 0.9680(8) 0.932(2)

gg (→ H) → WW Higgs 13.54(2) 3.201(5) 15.74(2) 0.940(2) 0.926(2)

gg (→ H) → ZZ stand. 1.893(3) 1.417(2) 3.205(5) 0.969(2) 0.945(3)

gg (→ H) → ZZ Higgs 1.377(2) 0.0531(1) 1.445(2) 1.011(2) 1.011(3)



gg (→ H) → W−W+ → lνl l′νl′ , LHC, 7 TeV, standard cuts

pT l [GeV] (left) and ηl (right) distributions [fb/[o]]




pT l,min [GeV] (left) and pT l,max [GeV] (right) distributions [fb/[o]]




Mll′ [GeV] (left) and ∆φll′ [◦] (right) distributions [fb/[o]]



gg (→ H) → ZZ → lll′ l′, LHC, 7 TeV, standard cuts

Mlll′ l′ [GeV] (left) and Mll [GeV] (right) distributions [fb/[o]]

high-mass h vv signal and higgs width determination at the lhc€¦ · n. kauer high-mass h → v v...

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