Spin/CP Combination in ATLAS Higgs Hunting 2015, LAL Orsay YSF - - - PowerPoint PPT Presentation

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Spin/CP Combination in ATLAS Higgs Hunting 2015, LAL Orsay YSF - - - PowerPoint PPT Presentation

Dec 11, 2022 102 likes •295 views

Not reviewed, for internal circulation only Spin/CP Combination in ATLAS Higgs Hunting 2015, LAL Orsay YSF - July 30th Lars Egholm Pedersen* on behalf on the ATLAS Collaboration *The Niels Bohr Institute, University of Copenhagen 1

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Spin/CP Combination in ATLAS

Higgs Hunting 2015, LAL Orsay
 YSF - July 30th

1

Lars Egholm Pedersen*

  • n behalf on the ATLAS Collaboration

*The Niels Bohr Institute, University of Copenhagen

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

Outline

2

  • Analyses aim to examine the Higgs Spin/CP nature

1:

  • Test pure BSM spin-0 and spin-2 models against the Standard Model
  • Constrain possible SM and BSM mixing of Spin-0 boson
  • Extend previous publication

2 with updated spin-2 results and HVV EFT approach

  • Combine results from all sensitive vector boson channels:
  • H→ZZ*→4l, H→WW*→eνμν (+≦1jet)

3 and H→γγ

  • ZZ* and WW* are used to examine both spin-0 and spin-2 models, whereas γγ

contributes to spin-2

3: Determination of spin and parity of the Higgs boson in the WW*→eνμν decay channel with the ATLAS detector 1: Study of the spin and parity of the Higgs boson in di-boson decays with the ATLAS detector 2: Evidence for the spin-0 nature of the Higgs boson using ATLAS data

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

  • Spin-0: a) Testing SM against pure BSM scalar (0+h) and pseudo-scalar (0-)



 b) Constrain continuum of BSM / SM couplings:

  • Testing SM against three spin-2 coupling configurations: κq/κg = 0,1 and 2

Models

  • Classification framework proposed in ‘A framework for Higgs characterisation’*
  • SM without Higgs plus generic boson described with EFT. 


(EFT scale here chosen to Λ=1 TeV)

3

*JHEP11(2013)043

Values of spin-2 quark and gluon couplings pX

T selections (GeV)

κq = κg Universal couplings – – κq = 0 Low light-quark fraction < 300 < 125 κq = 2κg Low gluon fraction < 300 < 125

  • Test SM against graviton-like spin-2. Including only quark and gluon couplings in production
  • Others estimated to be insignificant: σEW/σQCD ≅ 0.03%

S p i n

  • 2

W W* , Z Z* , γ γ

JP Model Values of tensor couplings κSM κHV V κAV V α 0+ SM Higgs boson 1 0+

h

BSM spin-0 CP-even 1 0− BSM spin-0 CP-odd 1 π/2

W W* , Z Z*

(˜ κAV V /κSM) · tan α, ˜ κHV V /κSM

✓ ˜ κX = 1 4 ν ΛκX ◆

CP-even CP-odd

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

Hypothesis discrimination

  • Different approaches used in final states

4

0.02 0.04 0.06 0.08 0.1 0.12

  • MELA discriminant
P

J 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 discriminant

ZZ

BDT 1 − 0.5 − 0.5 1 1.5 2

Data SM + = 0 P Signal J Background ZZ* + Zjets

ATLAS 4l → ZZ* → H

  • 1
= 7 TeV, 4.5 fb s
  • 1
= 8 TeV, 20.3 fb s

Category C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 Signal fraction 0.1 0.2 0.3 0.4 0.5

Data SM + =0 P J g κ = q κ + =2 P J =0 q κ + =2 P J g κ =2 q κ + =2 P J

ATLAS

  • 1

= 8 TeV , 20.3 fb s

BDT output 2 4 6 8 10 12 Entries 20 − 20 40 60 80 100 120

−

= 0

P

J Data - Bkg ATLAS

  • 1

= 8 TeV, 20.3 fb s µ = 0, e

j

WW*, n → H

−

vs 0

+

H→ZZ*→4l H→WW*→eνμν H→γγ

Possible to fully reconstruct final state Discriminants constructed from BSM, SM matrix elements BDT suppresses backgrounds

Each test based on two BDTs: Spin-0: SM vs Bkg.+ SM vs Alt.
 0 Jet category
 Spin-2: SM vs Bkg + Alt. vs Bkg.
 0+1 Jet categories BDTs trained on lepton
 kinematics and MET Discriminant based on polar angle, |cos(θ*)| 10 categories from 0 to 1 Extend with 11th category 
 with pT ∈ [125, 300] GeV Per-category mγγ-fit
 determines signal fraction

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

h +

= 0

P

J

−

= 0

P

J

g κ = q κ +

= 2

P

J

<300 GeV T p =0 q κ +

= 2

P

J

<125 GeV T p =0 q κ +

= 2

P

J

<300 GeV T p g κ =2 q κ +

= 2

P

J

<125 GeV T p g κ =2 q κ +

= 2

P

J

q ~

  • 30
  • 20
  • 10

10 20 30 40

ATLAS l 4 → ZZ* → H

  • 1

= 7 TeV, 4.5 fb s

  • 1

= 8 TeV, 20.3 fb s

νµν e → WW* → H

  • 1

= 8 TeV, 20.3 fb s

γ γ → H

  • 1

= 7 TeV, 4.5 fb s

  • 1

= 8 TeV, 20.3 fb s Observed Expected σ 1 ± SM

+

σ 2 ± SM

+

σ 3 ± SM

+

σ 1 ±

P

J σ 2 ±

P

J σ 3 ±

P

J

  • Tests examining the Spin/CP nature of the Higgs boson:
  • Spin-0: CP-even BSM and pseudo-scalar
  • Spin-2: Universal couplings and κq/κg = 0 and 2
  • Combining diboson final states: WW*, ZZ* and γγ
  • Exclusion determined from CLS :

Results-I: Fixed hypotheses

5

γγ

ZZ+WW

SM is favoured and alternative models excluded > 95%CLS

Tested Hypothesis palt

exp,µ=1

palt

exp,µ=ˆ µ

pSM

  • bs

palt

  • bs
  • Obs. CLs (%)

0+

h

2.5 · 10−2 4.7 · 10−3 0.85 7.1 · 10−5 4.7 · 10−2 0− 1.8 · 10−3 1.3 · 10−4 0.88 < 3.1 · 10−5 < 2.6 · 10−2 2+(κq = κg) 4.3 · 10−3 2.9 · 10−4 0.61 4.3 · 10−5 1.1 · 10−2 2+(κq = 0; pT < 300GeV ) < 3.1 · 10−5 < 3.1 · 10−5 0.52 < 3.1 · 10−5 < 6.5 · 10−3 2+(κq = 0; pT < 125GeV ) 3.4 · 10−3 3.9 · 10−4 0.71 4.3 · 10−5 1.5 · 10−2 2+(κq = 2κg; pT < 300GeV ) < 3.1 · 10−5 < 3.1 · 10−5 0.28 < 3.1 · 10−5 < 4.3 · 10−3 2+(κq = 2κg; pT < 125GeV ) 7.8 · 10−3 1.2 · 10−3 0.80 7.3 · 10−5 3.7 · 10−2

CLS(JP

alt) =

p(JP

alt)

1 − p(JP

SM)

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

Results-II: Spin-0 coupling ratios

6

Data in agreement with Standard Model expectations

  • Combined fit performed on ZZ* and WW* final states
  • Results translated to effective BSM cross section fraction

C P

  • O

d d C

  • n

t r i b u t i

  • n

C P

  • E

v e n B S M C

  • n

t r i b u t i

  • n
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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

Conclusions and outlook

7

  • Analysis of Higgs Spin/CP nature:
  • Pure BSM CP-even scalar (0+

h) and pseudo-scalar (0-) excluded in favour of SM

  • SM furthermore favoured over spin-2 models with different κq/κg coupling

configurations

  • Spin-0 BSM/SM coupling ratio fits indicate that data is agreement with SM
  • Looking forward to Run-II:
  • Continue development of EFT approach to study HVV interaction
  • Add different Higgs production mechanisms
  • Simultaneous fit of couplings
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Backup

8

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

Models - Expanded

9

JP Model Values of tensor couplings κSM κHV V κAV V α 0+ SM Higgs boson 1 0+

h

BSM spin-0 CP-even 1 0− BSM spin-0 CP-odd 1 π/2 Values of spin-2 quark and gluon couplings pX

T selections (GeV)

κq = κg Universal couplings – – κq = 0 Low light-quark fraction < 300 < 125 κq = 2κg Low gluon fraction < 300 < 125

Spin-0 Spin-2

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

Per final state results

10

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

Per final state results, tensor structure

11

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

H→ZZ*→4l

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Hypothesis tests Discriminants Normalisations

  • Background discriminant from production

related observables:
 η4l, pT,4l, m4l, cos(θ*) and Φ1

JP − MELA = P(H1) P(H1) + P(H2)

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

H→ZZ*→4l

13

  • Background discriminant from production

related observables:
 η4l, pT,4l, m4l, cos(θ*) and Φ1

Tensor structure fit discriminants

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

H→WW*→4l

14

  • Spin-2 tests training parameters: pTll, mll, ΔΦll, mT
  • SM vs 0+h Training parameters: pTll, mll, ΔΦll, pmiss
  • SM vs 0- Training parameters: mll, pTl1 -0.5pTl2 + 0.5pTmiss, ΔpT, ΔΦll

Spin-2, UC Spin-0

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

H→γγ

15

  • Category normalisation from fitting function:

Δηγγ: Separation in pseudorapidity 
 between the two photons

*)| θ |cos( 0.2 0.4 0.6 0.8 1 *)| θ (1/N) dN/d|cos( 0.02 0.04 0.06 0.08 0.1 0.12 0.14

SM

+

=0

P

J

g

κ =

q

κ

+

=2

P

J =0

q

κ

+

=2

P

J

g

κ =2

q

κ

+

=2

P

J

ATLAS Simulation = 8 TeV s <125 GeV

γ γ T

p

  • fS[c](mγγ) : Chrystal Ball + Gaussian
  • fB[c](mγγ) : Exponential of first or second degree polynomial
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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

Combination

16

  • Construct combined likelihood model including all final states
  • Common systematic uncertainties are identified and correlated between final states
  • WW*, ZZ*: Luminosity, VV background renormalisation+factorisation scale and parton density function
  • ZZ*, γγ: E-Cal resolution model

Ratio of SM/BSM likelihoods exclude pure spin-0 and spin-2 models Profiled likelihood scan limits coupling ratios

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

Coupling ratios to effective cross section fraction

17

Assuming one BSM coupling Cross section fractions from MadGraph5_aMC@NLO

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Lars Egholm Pedersen, The Niels Bohr Institute Higgs Hunting 2015, Orsay, July 30th

References

  • Study of the spin and parity of the Higgs boson in diboson decays with the

ATLAS detector
 http://arxiv.org/abs/1506.05669

  • Determination of spin and parity of the Higgs boson in the WW* →eνμν

decay channel with the ATLAS detector
 http://dx.doi.org/10.1140/epjc/s10052-015-3436-3

  • A framework for Higgs characterisation


http://link.springer.com/article/10.1007%2FJHEP11%282013%29043

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