How Wide is the Higgs Boson:off-shell constraints from CMS

Andrei Gritsan

Johns Hopkins University

May 29, 2014

LBNL Research Progress Meeting

Overview

• Introduction

• The Higgs boson

• How we see it

• Off-shell production

• Data analysis

– H → Z∗Z∗ → 4ℓ

– H∗ → ZZ → 4ℓ

– H∗ → ZZ → 2ℓ2ν

• Theoretical considerations

• Summary and outlook

Andrei Gritsan, JHU II May 29, 2014

A FEW SLIDES OF HISTORY

July 2012: Observation of a New Boson

• Observation of a New Boson on CMS: 5σ excess

X → Z(∗)Z(∗) X → γγ

• Probability of background

∼ 0.2× 10−6

Higgs boson mass (GeV)116 118 120 122 124 126 128 130

Loca

l p-v

alue

-1210

-1110

-1010

-910

-810

-710

-610

-510

-410

-310

-210

-110

1σ1σ2

σ3

σ4

σ5

σ6

σ7

Combined obs.

Exp. for SM H

γγ →H

ZZ→H

WW→H

CMS Preliminaryγγ ZZ + WW + →H

-1 = 7 TeV, L = 5.1 fbs-1 = 8 TeV, L = 5.3 fbs

Andrei Gritsan, JHU IV May 29, 2014

July 2012: Observation of a New Boson

• Observation of a New Boson on ATLAS: 5σ excess

X → Z(∗)Z(∗) X → γγ

[GeV]4lm100 150 200 250

Even

ts/5

GeV

0

5

10

15

20

25

30

35

-1Ldt = 4.8 fb∫ = 7 TeV: s-1Ldt = 5.8 fb∫ = 8 TeV: s

4l→(*)ZZ→H

Data(*)Background ZZ

tBackground Z+jets, t=125 GeV)

HSignal (m

=150 GeV)H

Signal (m=190 GeV)

HSignal (mSyst.Unc.

Preliminary ATLAS

100 110 120 130 140 150 160

Eve

nts

/ GeV

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

Data 2011 and 2012 = 126.5 GeV)

HSig + Bkg inclusive fit (m

4th order polynomial

Selected diphoton sample

-1 Ldt = 4.8 fb∫ = 7 TeV, s

-1 Ldt = 5.9 fb∫ = 8 TeV, s

ATLAS Preliminary

[GeV]γγm

100 110 120 130 140 150 160

Dat

a - B

kg

-100

0

100

• Probability of background

∼ 0.2× 10−6

[GeV]Hm

110 115 120 125 130 135 140 145 150

0Lo

cal p

-710

-410

-110

210

510

810

Exp. Comb.

Obs. Comb.γγ →Exp. H

γγ →Obs. H

llll→ ZZ* →Exp. H

llll→ ZZ* →Obs. H

νlν l→ WW* →Exp. H

νlν l→ WW* →Obs. H

bb→Exp. H

bb→Obs. H

ττ →Exp. H

ττ →Obs. H

ATLAS Preliminary 2011 + 2012 Data = 7 TeVs, -1 L dt ~ 4.6-4.8 fb∫ = 8 TeVs, -1 L dt ~ 5.8-5.9 fb∫

σ0 σ1 σ2

σ3

σ4

σ5

Andrei Gritsan, JHU V May 29, 2014

The Higgs Boson Signal on CMS

• Excellent signal H → ZZ,WW, γγ, τ+τ−, bb̄

6.8, 4.3, 3.2, 3.2, 2.1σ

(6.7, 5.8, 3.9, 3.7, 2.1σ expected)

Andrei Gritsan, JHU VI May 29, 2014

Discovery of a Higgs Boson

• Discovery of a Higgs Boson

– absolutely new form of matter-energy

– consistent with fundamental JP = 0+

scalar excitation of a vacuum field

• It would be foolish to stop here

– mass (is Universe stable, are EW data consistent?..)

– width / lifetime (are there missing final states?)

– quantum numbers (is there CP violation?..)

– coupling strength in production and decay (is it the right Higgs?..)

• It is also a triumph of predictive power of scientific knowledge

– we knew where to look

– but a discovery was not guaranteed, also true for the next steps

Andrei Gritsan, JHU VII May 29, 2014

The Higgs→ ZZ → 4ℓ Signal on CMS

Andrei Gritsan, JHU VIII May 29, 2014

The Higgs→ ZZ → 4ℓ Signal on CMS

Andrei Gritsan, JHU IX May 29, 2014

The Higgs→ ZZ → 4ℓ Signal on CMS

Andrei Gritsan, JHU X May 29, 2014

TOPIC FOR TODAY

References for Today Presentation

• ”Constraints on the Higgs boson width

from off-shell production and decay to Z-boson pairs”

CMS-HIG-14-002 (Moriond - 2014), arXiv:1405.3455 [hep-ex]

submitted to PLB on May 14, 2014

• ”Measurement of the properties of a Higgs boson

in the four-lepton final state” (CMS H → ZZ Run1 ”legacy”)

CMS-HIG-13-002 (Moriond - 2013), arXiv:1312.5353 [hep-ex]

published in PRD,89,092007 on May 14, 2014

• ”Higgs Working Group Report

of the Snowmass 2013 Community Planning Study”

arXiv:1310.8361 [hep-ex]

Andrei Gritsan, JHU XII May 29, 2014

The Large Hadron Collider

Andrei Gritsan, JHU XIII May 29, 2014

The CMS Detector

• Complex detector

to sort collision debris out

Andrei Gritsan, JHU XIV May 29, 2014

The CMS Detector

Total weight 12500 t

Diameter 15 m

Length 22 m

Magnetic field 4 T

Andrei Gritsan, JHU XV May 29, 2014

The Experiment

Andrei Gritsan, JHU XVI May 29, 2014

Detection of Major Objects

• Leptons: ℓ± in Si Tracker: e± (EM Calorimeter), µ± (Muon System)

• Photons: γ (EM Calorimeter)

• Quark q & gluon g jets → ”Particle Flow” thru Hadronic Calorimer

• Neutrinos ν ⇒ missing energy (”MET”)

ZZ → (µ+µ−)(νν̄)

Andrei Gritsan, JHU XVII May 29, 2014

Production and Decay of a Higgs Boson

• Excite vacuum: gg, VBF,.. → H → ZZ(∗), WW (∗), γγ, τ+τ−, bb̄,..

[GeV] HM80 100 200 300 400 1000

H+

X)

[pb

]

→(p

p

σ

-210

-110

1

10

210= 8 TeVs

LH

C H

IGG

S X

S W

G 2

01

2

H (NNLO+NNLL QCD + NLO EW)

→pp

qqH (NNLO QCD + NLO EW)

→pp

WH (NNLO QCD + NLO EW)

→pp

ZH (NNLO QCD +NLO EW)

→pp

ttH (NLO QCD)

→pp

[GeV]HM80 100 120 140 160 180 200

Hig

gs B

R +

Tot

al U

ncer

t

-410

-310

-210

-110

1

LH

C H

IGG

S X

S W

G 2

013

bb

ττ

µµ

cc

gg

γγ γZ

WW

ZZ

gg→Hqq→qqH

V→V H

Andrei Gritsan, JHU XVIII May 29, 2014

Signal and Background

• At LHC might have produced > 200000 Higgs bosons / experiment

gluon fusion weak boson fusion associated production

• The challenge is to distinguish signal from backgrounds, examples:

qq̄ → ZZ(∗)(γ(∗)) qq̄ → Z(γ)+jets gg→ tt̄

Andrei Gritsan, JHU XIX May 29, 2014

Track / Mass Resolution

• H → ZZ → (ℓ+ℓ−)(ℓ+ℓ−)

– excellent mass resolution ∼ 1%

– good control with Z, J/ψ → ℓ+ℓ−

– measure mass mH and width ΓH

Andrei Gritsan, JHU XX May 29, 2014

Fit mass and width of Higgs→ ZZ → 4ℓ

• Employ a 3D fit

m4ℓ – invariant mass

Dkinbkg – MELA (matrix element likelihood) to suppress background

δm4ℓ – per-event error estimate on invariant mass

(GeV)l4m

120 130 140 150 160 170 180

bkg

kin

D

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.05

0.1

0.15

0.2

0.254e

µ4

µ2e2

CMS-1

= 8 TeV, L = 19.7 fbs ; -1

= 7 TeV, L = 5.1 fbs

Andrei Gritsan, JHU XXI May 29, 2014

Test with Z → 4ℓ

• Excellent candle Z → ℓ+ℓ−γ∗ → ℓ+ℓ−ℓ+ℓ−

mZ = 91.12± 0.37 GeV (compare PDG 91.19 GeV)

ΓZ = 3.6+1.0−0.8 GeV (compare PDG 2.50 GeV)

Andrei Gritsan, JHU XXII May 29, 2014

Mass H(126)

• Employ a 3D fit

mH = 125.6± 0.4 (stat.)± 0.2 (syst.) GeV

Andrei Gritsan, JHU XXIII May 29, 2014

Width H(126)

• Employ a 3D fit

ΓH = 0.0+1.3−0.0 GeV < 3.4 GeV at 95% CL

expect ΓSMH = 0.00415 GeV at mH = 125.6 GeV

Andrei Gritsan, JHU XXIV May 29, 2014

CAN WE DO BETTER?

Off-shell effects

• mH = 125.6 GeV < 2mZ = 182.4 GeV

⇒ H → Z(∗)Z∗ with off-shell Z∗ ⇒ suppression

• Higgs boson remains on shell dσgg→H→ZZ

dm2ZZ

∼g2ggHg

2HZZ

(m2ZZ −m2

H)2 +m2

HΓ2H

Andrei Gritsan, JHU XXVI May 29, 2014

Higgs off-shell effects

100

2 MW

2 MZ 2 Mt 1000

10−6

10−5

10−4

10−3

10−2

10−1

WW

ZZ

HTO powered by complex - pole - scheme

8 TeV

MV V [ GeV]

M2 VV

dσ

dM

2 VV

[pb]

• Sizeable off shell H

gg → H → Z(∗)Z∗

on shell H, suppressed Z∗

gg → H∗ → ZZ

suppressed H∗, on shell Z

N. Kauer, G. Passarino

arXiv:1206.4803 [hep-ph]

MC: gg2VV, LO in QCD

Tot [pb] mZZ > 2mZ [pb] R[%]

gg → H → all 19.146 0.1525 0.8

gg → H → ZZ 0.5462 0.0416 7.6

Andrei Gritsan, JHU XXVII May 29, 2014

Higgs boson width from off-shell production

dσgg→H→ZZ

dm2ZZ

∼g2ggHg

2HZZ

(m2ZZ −m2

H)2 +m2

HΓH2

• On peak (mZZ ∼ mH) and off peak (mZZ −mH ≫ ΓH)

F. Caola, K. Melnikov: arXiv:1307.4935 [hep-ph]

σonpeakgg→H→ZZ = constg2ggHg

2HZZ

ΓH

σoffpeakgg→H→ZZ = const′ g2ggHg2HZZ

⇒ measurement of ΓH

• Complication: signal - background destructive interference

Andrei Gritsan, JHU XXVIII May 29, 2014

Higgs boson width from off-shell production

σonpeakgg→H→ZZ = constg2ggHg

2HZZ

ΓH

σoffpeakgg→H→ZZ = const′ g2ggHg2HZZ

• Given the signal strength at the peak µ = σ/σSM

⇒ off-shell signal ∝ ΓH , interference ∝√ΓH

Andrei Gritsan, JHU XXIX May 29, 2014

Monte Carlo Simulation (off shell)

100100100 200200200 300300300 400400400 500500500 600600600 700700700 800800800 900900900 100010001000

000

0.20.20.2

0.40.40.4

0.60.60.6

0.80.80.8

1.01.01.0

1.21.21.2

NNLO

LO

HHH virtuality [ GeV]

Lin

eshape

by Giampiero

arXiv:1312.2397

• gg → ZZ(∗)/Zγ∗ gg2VV and

MCFM: J. Campbell, K. Ellis, C. Williams

arXiv:1311.3589 [hep-ph]

– LO in QCD, Pythia shower

– running QCD scale µR,F = mZZ/2

– uncertainties µR,F ∈ [mZZ ,mZZ/4]

– signal K-factor ∼ 2

– bkg K-factor = signal K ±10%

(soft-collinear approximation arXiv:1304.3053 for gg → WW )

• No references for width studies in VBF: V ∗V ∗ → ZZ(∗)

use Phantom: A. Ballestrero et al., arXiv:0801.3359 [hep-ph]

• Generate sig, bkg, sig+bkg+interference ⇒ extract interference

match signal on-peak cross-section to best knownAndrei Gritsan, JHU XXX May 29, 2014

Monte Carlo Simulation

[GeV]T

p0 50 100 150 200 250

0

0.05

0.1

• On-shell signal MC arXiv:1309.4819

– NLO QCD production POWHEG

– H → V V → 4f decay JHUGen

– anomalous couplings with JHUGen

spin-0, 1, 2, qq̄, gg, VBF, V H, H2j

• Dominant qq̄ → ZZ background

– NLO QCD POWHEG

NLO EW re-weighting

follow arXiv:1307.4331, arXiv:1305.5402

−(5− 10)% in 220− 500 GeV range

∼ 40% uncertainty on the correction

Andrei Gritsan, JHU XXXI May 29, 2014

Use Kinematics to Suppress Background

• One challenge is the dominant qq̄ → ZZ background

• Follow the same approach as at the Higgs discovery

MELA technique

(Matrix Element Likelihood Approach)

to suppress qq̄ → ZZ

vs gg → ...→ ZZ

MELA > 0.5

Andrei Gritsan, JHU XXXII May 29, 2014

Matrix Element Likelihood Approach

Andrei Gritsan, JHU XXXIII May 29, 2014

Matrix Element Likelihood Approach

Andrei Gritsan, JHU XXXIV May 29, 2014

Matrix Element Likelihood Approach

vs.

• Optimal discriminant to separate gg → ZZ vs qq̄ → ZZ

Dgg =Pgg

tot

Pggtot + Pqq̄

bkg

=

1 +Pqq̄

bkg

10×Pggsig +

√10× Pgg

int + Pggbkg

−1

MCFM - continuum, JHUGen - onpeak signal, analytical

• Higgs discovery:

Dkinbkg =

P0+

P0+ + Pqq̄bkg

• Higgs spin-parity:

DJP =P0+

P0+ + PJP

Andrei Gritsan, JHU XXXV May 29, 2014

Kinematics

• MELA Dgg(mZZ ,mZ1,mZ2, cos θ1, cos θ2, cos θ∗,Φ,Φ1)

Andrei Gritsan, JHU XXXVI May 29, 2014

H∗ → ZZ → 4ℓ Mass after Kinematic Selection

• Optimal use of kinematic information

before after Dgg > 0.65

Andrei Gritsan, JHU XXXVII May 29, 2014

Semileptonic Channel H → ZZ → 2ℓ2ν

• Partial reco, but ×5.5 higher branching

⇒ comparable to 4ℓ sensitivity at high mass

but no hope at low mass (overwhelmed with Z+jets background)

m2T =

[

√

pT,2ℓ2 +m2ℓ2 +

√

EmissT

2+m2ℓ

2

]2

−[

~pT,2ℓ + ~EmissT

]2

Andrei Gritsan, JHU XXXVIII May 29, 2014

Semileptonic Channel H → ZZ → 2ℓ2ν

• Partial reco, but ×5.5 higher branching

⇒ comparable to 4ℓ sensitivity at high mass

but no hope at low mass (overwhelmed with Z+jets background)

m2T =

[

√

pT,2ℓ2 +m2ℓ2 +

√

EmissT

2+m2ℓ

2

]2

−[

~pT,2ℓ + ~EmissT

]2

Andrei Gritsan, JHU XXXIX May 29, 2014

Look at enhanced signal region

• For illustration purpose define the enhanced signal regions

H → ZZ → 4ℓ H → ZZ → 2ℓ2ν

m4ℓ > 330 GeV, Dgg > 0.65 mT > 350 GeV, EmissT > 100 GeV

Andrei Gritsan, JHU XL May 29, 2014

Enhanced signal H → ZZ → 4ℓ and 2ℓ2ν

4ℓ 2ℓ2ν

(a) total gg (ΓH = ΓSM

H) 1.8±0.3 9.6±1.5

gg signal component (ΓH = ΓSM

H) 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 = ΓSM

H) 0.23±0.01 0.90±0.05

VBF signal component (ΓH = ΓSM

H) 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) qq̄ 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 = ΓSM

H) 11.4±0.8 93.2±6.0

(b+d+e+f) total expected (ΓH = 10× ΓSM

H) 20.1±1.4 124.9±7.8

observed 11 91

Andrei Gritsan, JHU XLI May 29, 2014

How to Extract the Width• Relative size of low and high mass Higgs signal

– analysis at high mass ⇒ gggH gHZZ (gg→ H) or gHVV gHZZ (VBF)

– must relate to on-peak to measure Γ

• Composition of production: gg→ H vs VBF

– need to know to describe the shape

• Is the coupling gHVV(mZZ) running (anomalous)?

Andrei Gritsan, JHU XLII May 29, 2014

Extracting the Width

• Determine strength and production composition from the peak

– µggH and µVBF provide both (ratio to SM µ = σ/σSM)

Ponshelltot (~x) = µggH × [Pgg

sig(~x) + P tt̄Hsig (~x)] + µVBF × [PVBF

sig (~x) + PVHsig (~x)]

+ Pqq̄bkg(~x) + Pgg

bkg(~x) + . . .

• Relate to high mass

– ΓH is the only free parameter remaining

Poffshelltot (~x) =

µggH × ΓH

Γ0× Pgg

sig(~x) +

√

√

√

√µggH × ΓH

Γ0×Pgg

int(~x) + Pggbkg(~x)

+

µVBF ×ΓH

Γ0× PVBF

sig (~x) +

√

√

√

√µVBF ×ΓH

Γ0×PVBF

int (~x) + PVBFbkg (~x)

+ Pqq̄bkg(~x) + . . .

Andrei Gritsan, JHU XLIII May 29, 2014

CONSTRAINTS FROM THE LOW MASS

Constraints from the low mass

• Employ a 3D fit and 2 jet tagging catetories

m4ℓ – invariant mass

Dkinbkg – MELA (matrix element likelihood) to suppress background

if at least 2 jets: Djet – to identify VBF or VH (mjj, ηjj)

if <2 jets: pT (4ℓ) – to identify VBF or VH

Andrei Gritsan, JHU XLV May 29, 2014

Constraints from the low mass

• Employ a 3D fit and 2 jet tagging catetories

m4ℓ – invariant mass

Dkinbkg – MELA (matrix element likelihood) to suppress background

if at least 2 jets: Djet – to identify VBF or VH (mjj, ηjj)

if <2 jets: pT (4ℓ) – to identify VBF or VH

(GeV)l4m

120 130 140 150 160 170 180

bkg

kin

D

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.05

0.1

0.15

0.2

0.254e

µ4

µ2e2

CMS-1

= 8 TeV, L = 19.7 fbs ; -1

= 7 TeV, L = 5.1 fbs

Andrei Gritsan, JHU XLVI May 29, 2014

Production Mechanism Results

Ponshelltot (~x) = µggH × [Pgg

sig(~x) + P tt̄Hsig (~x)] + µVBF × [PVBF

sig (~x) + PVHsig (~x)]

+ Pqq̄bkg(~x) + Pgg

bkg(~x) + . . .

µggH = 0.80+0.46−0.36 σSM(ggH + tt̄H) = 14.99 pb + 0.085 pb

µVBF = 1.7+2.2−2.1 σSM(VBF+ V H) = 1.214 pb + 0.896 pb

µ = σ/σSM = 0.93+0.26+0.13−0.23−0.09

Andrei Gritsan, JHU XLVII May 29, 2014

CONSTRAINTS FROM THE HIGH MASS

High Mass: H → ZZ → 4ℓ

Poffshelltot (~x) =

µggH × ΓH

Γ0× Pgg

sig(~x) +

√

√

√

√µggH × ΓH

Γ0×Pgg

int(~x) + Pggbkg(~x)

+

µVBF ×ΓH

Γ0×PVBF

sig (~x) +

√

√

√

√µVBF ×ΓH

Γ0× PVBF

int (~x) + PVBFbkg (~x)

ΓH = 1.9+11.7−1.9 MeV < 33 MeV at 95% CL

expected: 4.2+17.3−4.2 MeV < 42 MeV at 95% CL

Andrei Gritsan, JHU XLIX May 29, 2014

1D Fit in H → ZZ → 4ℓ

Andrei Gritsan, JHU L May 29, 2014

High Mass: H → ZZ → 2ℓ2ν

• Combine H → ZZ → 2ℓ2ν at high mass and 4ℓ at low mass

ΓH = 1.8+12.4−1.8 MeV < 33 MeV at 95% CL

expected: 4.2+19.3−4.2 MeV < 44 MeV at 95% CL

Andrei Gritsan, JHU LI May 29, 2014

Combined Result

ΓH = 1.8+7.7−1.8 MeV < 22 MeV = 5.4× ΓSM

H at 95% CL

expected: 4.2+13.5−4.2 MeV < 33 MeV = 8× ΓSM

H at 95% CL

Andrei Gritsan, JHU LII May 29, 2014

Model (in)dependence

σonpeakgg→H→ZZ = constg2ggHg

2HZZ

Γσoffpeakgg→H→ZZ = const′ g2ggHg

2HZZ

• Higgs boson coupling HV V (gHV V )

– experimental limits prefer tree-level SM HV V coupling

– anomalous HV V couplings enhance off-shell production

⇒ conservative limit

• Higgs boson production in gluon fusion (gggH)

– top quark dominance, no new particles in the loop

• Higgs boson production mechanism

– very mild dependence (e.g. VH vs VBF), fit directly in the data

• Background model

– no BSM in background; benefit from improved SM calculations

Andrei Gritsan, JHU LIII May 29, 2014

CP Results in H → ZZ → 4ℓ

• Assumed tree-level HV V coupling either in decay or VBF production

A(HV V ) =1

v

(

a1m2V ǫ

∗1ǫ

∗2 + a2f

∗(1)µν f ∗(2),µν + a3f

∗(1)µν f̃ ∗(2),µν

)

SM Higgs 0+: (a1) CP ∼few% (a2) CP ∼10−10 ? (a3) CP6

(or beyond SM) (or beyond SM)

• Test with optimal MELA observables for many JP models, e.g. 0−

Andrei Gritsan, JHU LIV May 29, 2014

CP Results in H → ZZ → 4ℓ

• Exclude pure pseudo-scalar 0− at 99.95% CL

fa3 =σ(a3)

σ(a1) + σ(a3)= 0.00+0.17

−0.00 < 0.51 at 95%CL

• and many other models:

spin-0, 1, 2

consistent with JP = 0+

Andrei Gritsan, JHU LV May 29, 2014

Anomalous HV V Couplings and Off-shell Effects

A(HV V ) =1

v

(

g1m2V ǫ

∗1ǫ

∗2 + g2f

∗(1)µν f ∗(2),µν + g4f

∗(1)µν f̃ ∗(2),µν

)

• Higher-dimensional non-renormalizable operators lead to

σ4/σ1 blowing up at higher q2 (for pseudoscalar 0−)

same effect for 0+h , spin-2, spin-1; example of f f̄ → V ∗(q2) → V H

[GeV] s200 300 400 500 600 700 800 900 1000

[fb]

σ

1

10

210

310

410

[GeV] s200 300 400 500 600 700 800 900 1000

[fb]

σ

1

10

210

310

410

0−

0+h

0+m (SM) 0+m (SM)

arXiv:1309.4819 Analytic MELA calc.

Andrei Gritsan, JHU LVI May 29, 2014

Anomalous HV V Couplings and Off-shell Effects

• Same enhancement σi/σ1 with higher-dim. operators H∗(q2 = m2ZZ)

[GeV] ZZm200 400 600 800 1000 1200

1σ/ 4σ

0

10

20

30

40

50

60

[GeV] ZZm200 400 600 800 1000 1200

1σ/ 2σ

0

5

10

15

20

25

30

JHUGenMELA calc.

AnalyticMELA calc.

similar study also in arXiv:1403.4951 [hep-ph]

• Conclusion on anomalous HV V couplings:

– experimental data consistent with SM coupling a1

– there is still room for small anomalous contributions

– width constraint would be only tighter if those are present

Andrei Gritsan, JHU LVII May 29, 2014

Anomalous ggH Couplings

• In gg → H rely on the dominance of t-quark in the loop

– assume no new particles in the loop

– otherwise some modification to offshell / onshell ratio

Andrei Gritsan, JHU LVIII May 29, 2014

WHAT IS THE HIGGS BOSON LIFETIME

Higgs Boson Lifetime

• How long does the Higgs boson live?

τH =h̄

ΓH, expect 1.6× 10−22 s

we know it is not stable (H → ZZ, ...)

observe 0.3× 10−22 s < τH <∞

• Can we set a better upper bound?

– expect σv ∼ 50µm vertex resolution, p ∼ 50 GeV

– flight distance ∼ pmccτH ∼ 2 · 10−14 m = 20 fm ∼ 4× 10−10 × σv

could reach 0.3× 10−22 s < τH < (?) 0.4× 10−12 s <∞

Andrei Gritsan, JHU LX May 29, 2014

Summary: How Wide is the Higgs Boson?

0 < ΓH < 22 MeV = 5.4× ΓSMH at 95% CL

(0.3× 10−22 s < τH <∞)

mild assumptions (no new particles in ggH loop)

• Rich physics with the Higgs boson

– mass

– width and lifetime

– quantum numbers / CP

– production and decay couplings

• So far consistent picture

reduced room to decay to new states...

Andrei Gritsan, JHU LXI May 29, 2014