The production of additional bosons and the impact on the Large - - PowerPoint PPT Presentation

SLIDE 1

The production of additional bosons and the impact on the Large Hadron Collider

presented by Alan S. Cornell 
 for the HEP group, University of the Witwatersrand With N.Chakrabarty, T .Mandal and 
 B.Mukhopadhyaya (HRI/Uppsala)

SLIDE 2

• arXiv:1506.00612
• arXiv:1603.01208
• arXiv:1606.01674
• arXiv:1608.03466
• arXiv:1706.02477
• arXiv:1706.06659

Most relevant references

SLIDE 3

Outline

• The Effective Lagrangian
• Study with Run I data
• Formulation of the hypothesis
• Compatibility with Run II data
• Prediction of signatures at the LHC

SLIDE 4

Bottom-up approach: What if?

g g h ?

• Initially we were interested in 


investigating the Higgs boson 
 transverse momentum

• What if the Higgs boson is also being 


produced in association with something 
 else?

• What can we fill the blob with?

SLIDE 5

The Lagrangian

Introducing H and 𝝍 fields with the interactions 
 listed below

SLIDE 6

Main decay modes of H

H h χ χ

Used effective coupling

Decay to single Higgs and 
 a DM candidate

• DM is assumed scalar for 


simplicity

• This was our strategy, 


but we can infer different physics 
 in the blob

H h h Decay to 


double 
 Higgs pair.

H Z, W ⌥ Z, W ±

Decay to 
 vector boson 
 pairs.

SLIDE 7

Higgs boson pT spectra

8_10 PT

Entries 40000 Mean 75.01 RMS 33.47

(GeV)

T

Higgs p 20 40 60 80 100 120 140 160

Events

500 1000 1500 2000 2500

8_10 PT

Entries 40000 Mean 75.01 RMS 33.47

Spectra

T

• n Higgs p

X

Effect of m

=10GeV

X

m =20GeV

X

m =30GeV

X

m =40GeV

X

m =50GeV

X

m =60GeV

X

m =70GeV

X

m =80GeV

X

m

= 13TeV s

MH=300 GeV

SLIDE 8

Study of Run I data

Category Experiment Result Higgs pT spectra ATLAS h ➝ 𝛿𝛿 and h ➝ ZZ CMS h ➝ 𝛿𝛿 and h ➝ ZZ Di-Higgs resonance searches ATLAS Limits on H ➝ hh ➝ bb𝜐𝜐, 
 𝛿𝛿WW, 𝛿𝛿bb, and bbbb CMS Limits on H ➝ hh ➝ bb𝜐𝜐, 𝛿𝛿bb, 
 and multi-lepton Top associated Higgs production ATLAS Limits on h ➝ 𝛿𝛿 Measurements on h ➝ bb, and multi-lepton CMS Measurements on h ➝ 𝛿𝛿, h ➝ bb, and multi-lepton Decays to weak vector bosons ATLAS Limits on H ➝ ZZ and WW CMS Limits on H ➝ ZZ and WW Four groups of final states received consideration

SLIDE 9

Satisfactory goodness of the global fit, including Higgs pT

SLIDE 10

In terms of significance

[GeV]

H

m

260 270 280 290 300 310 320 BSM 2

χ −

SM 2

χ

2 4 6 8 10 12

pp Collisions @ 7 TeV and 8 TeV

σ 1 σ 2 σ 3

• To see how significant the

result is, we use a test statistic: 𝜓SM2 - 𝜓BSM2

• This gives an

improvement on the null hypothesis (the Standard Model) in units of sigma

• For one degree of

freedom, the best fit point has a 3 sigma

• improvement. This does

not mean evidence yet.

SLIDE 11

The combined result

[GeV]

H

m

260 270 280 290 300 310 320 2

χ Minimised

28 29 30 31 32

pp Collisions @ 7 TeV and 8 TeV

GeV

9 − 12 +

= 272

H

Best fit: m

H → pp )H t H + t( t t → pp

χ χ h → H VV → H hh → H χ χ h → H hh → H

• Combining all of the 


results produces a 
 best fit at 
 mH = 272 GeV

• The errors are +12 GeV


and -9 GeV, which are 


• ne sigma deviations 


from the best fit point

• At this point:

BR (H ➝ hh) BR (H ➝ VV) BR (H ➝ h𝜓𝜓) 𝛾g 0.030 ± 0.037 0.082 ± 0.059 0.89 ± 0.096 1.5 ± 0.6

Interpret this as H→h+X

Close to one degree of freedom, 𝛾g

SLIDE 12

The Hypothesis

1. The starting point of the hypothesis is the existence

• f a boson, H, that contains Higgs-like interactions,

with a mass in the range 250-295 GeV 2. In order to avoid large quartic couplings and to incorporate a mediator with Dark Matter a real scalar, S, is introduced. S interacts with the SM:

Also decays to SM

SLIDE 13

The intermediate scalar, S

• DM is introduced in the form of a scalar and the decay

H→h𝜓𝜓 via effective quartic couplings

• Due to gauge invariance we encounter an awkward

situation where a three body decay may be larger or comparable to a two body decay. This can be naturally explained by introducing an intermediate real scalar S

Also decays to SM

SLIDE 14

The Lagrangian

Note that some of the effective quartic couplings shown earlier appear here as trilinear. What was formerly a three body decay is now a two body decay (see below).

SLIDE 15

The Decays of H

• In the general case, H can have couplings as

those displayed by a Higgs boson in addition to decays involving the intermediate scalar and DM

H → WW, ZZ, qq, gg, Zγ, γγ, χχ + H → SS, Sh, hh

H → h(+X), S(+X)

Diboson decay Dominant decays

SLIDE 16

Compatibility with 
 the Run II data

• 1. hh limits
• 2. VV spectrum
• 3. tth→N leptons search
• 4. Impact on measured Higgs boson

cross-sections

• 5. Higgs boson pT spectrum

SLIDE 17

σ(pp → H → hh) ≈ 600 fb

Persistent excess with weak sensitivity to H→hh 
 cross-section because 𝜹𝜹bb missing. Now CMS has 
 very recently made 𝜹𝜹bb results (see next slide)

SLIDE 18

SLIDE 19

VBF has wide

• excess. Excess

driven by 4e, but also present in 4µ ATLAS-CONF-2017-058

SLIDE 20

ATLAS-CONF-2017-058

SLIDE 21

CMS-PAS-HIG-2016-41

Excess of ~20 events
 in the range 252-272
 corresponding to 2.5σ

SLIDE 22

Top associated Higgs production

(Multilepton final state) h

+

H S/h S/h

Can explain 
 µ~2

SLIDE 23

Reduced cross-section of ttH+tH is compensated by di-boson, (SS, Sh) decay and large Br(S→WW). Production of same sign leptons, three leptons is enhanced. 
 Enhanced tH cross-section

S, h → WW, ττ, ZZ

SLIDE 24

Table with signal strength w.r.t the SM in the search for tth with multiple leptons

SLIDE 25

This table includes all data available to data. ATLAS still needs to make available results with most of 2016 data public

µ = 1.92 ± 0.38

Very important to see results with the complete Run 2 data set. Need insight into the kinematics of the leptons and jet activity of these events. 
 (see next slide)

SLIDE 26

``` µµ

eµ

CMS-PAS-HIG-17-005

Discrepancy at level of 2.6σ

CMS has made public kinematics of leptons and jets with minimal cuts. The deviation from the SM seems larger than that obtained in the tth search

SLIDE 27

Impact on measurement of h→WW→𝓶𝓶

Njet 1 2 3 4 5 6 7 8 9 10 Unity 0.05 0.1 0.15 0.2 0.25 0.3 0.35

mH = 270 GeV, mh = 125 GeV

mS = 140 GeV mS = 145 GeV mS = 150 GeV mS = 155 GeV mS = 160 GeV mS = 165 GeV mS = 170 GeV

Because the contamination from additional Higgs bosons, production from H→Sh comes with additional jets (or leptons) measurement of signal strengths depends on the decay. In particular: µγγ,ZZ

Inclusive

µW W

0j,1j

> 1

Work in progress with IHEP , Beijing

Contamination Minimum 
 contamination

SLIDE 28

The survival probability of the H→Sh against a jet veto is model dependent. 
 Here we assume S to be a Higgs-like scalar, for which the survival probability for 0j and 1j is ~10% (assuming Br(S→𝜓𝜓)=0). 
 Low MET can also have significant impact on acceptance (under study).

SLIDE 29

Assuming dominance of H→Sh. 
 With 𝛾g2~2, cross-section at 13 TeV is ~20 pb. Over-measurement of the tth→N lepton and under-measurement of Vh(→bb) and h→WW→ll are a prediction of the model.

SLIDE 30

µ = 1.92 ± 0.38

tth→N lepton searches (SS,3l,4l+b-jets)

µ = 1.087 ± 0.084

Inclusive fiducial cross-section (𝜹𝜹, ZZ→4ℓ) Contamination from H→Sh is ~35%

µ = 0.8 ± 0.1

Vh(→bb) and h→WW→ℓℓ Final states with jet and lepton vetoes Contamination from H→Sh The tension between the upper and lower measurements is 2.9σ. Below we are going to assume that the “true” rate of the SM (SM') is given by the channels with no contamination (i.e. 0.8)

SLIDE 31

20 40 60 80 100 120 140 160 180 200 [GeV]

γ γ T

p 0.2 0.4 0.6 0.8 1 [fb/GeV]

γ γ T

p /d

fid

σ d

ATLAS data SM prediction BSM prediction SM + BSM

= 13 TeV s γ γ → h → pp = 265 GeV

H

m = 135 GeV

S

m Sh → H → gg BSM: = 1.3

2 g

β = 0.8

SM

µ

50 100 150 200 250 300 350 [GeV]

γ γ T

p 0.5 1 1.5 2 2.5 [fb/GeV]

γ γ T

p /d

fid

σ d

CMS data SM prediction BSM prediction SM + BSM

= 13 TeV s γ γ → h → pp = 265 GeV

H

m = 135 GeV

S

m Sh → H → gg BSM: = 1.3

2 g

β = 0.8

SM

µ

20 40 60 80 100 120 140 160 180 200 [GeV]

l 4 T

p 10 20 30 40 50 60 70 80 90

3 −

10 × [fb/GeV]

l 4 T

p /d

fid

σ d

CMS data SM prediction BSM prediction SM + BSM

= 13 TeV s l 4 → ZZ* → h → pp = 265 GeV

H

m = 135 GeV

S

m Sh → H → gg BSM: = 1.3

2 g

β = 0.8

SM

µ

20 40 60 80 100 120 140 160 180 200 [GeV]

l 4 T

p 0.02 0.04 0.06 0.08 0.1 0.12 [fb/GeV]

l 4 T

p /d

fid

σ d

ATLAS data SM prediction BSM prediction SM + BSM

= 13 TeV s l 4 → ZZ* → h → pp = 265 GeV

H

m = 135 GeV

S

m Sh → H → gg BSM: = 1.3

2 g

β = 0.8

SM

µ

Higgs pT Run II

13.3 fb-1

SLIDE 32

Normalising the SM as described in the previous slide. Results correspond to a fit to the four distributions simultaneously. ATLAS h𝜹𝜹 corresponds to 13.3 fb-1, 
 while the rest are from the entire 2015-2016 set:

χ2

SM 0 − χ2 BSM = 3.35σ

• ut of which the choice of normalisation

explains 2.2

SLIDE 33

Status of deviations in Run II

Final state Significance

H→hh ~2σ ZZ→4𝓶 in region of 240-270 GeV 3.6σ (ATLAS), 2.5σ (CMS) Leptons + b-jets (tth search) µ(tth) and lepton/jet kinematics 3.5σ Tension between h→WW→𝓶𝓶 with Wh(→bb) and tth 2.9σ Good description of Higgs pT, assuming µ(h)=0.8±0.1 2.2σ

Combination is model dependent. Enough data in Run II to have direct evidence in ZZ→4𝓶

SLIDE 34

Outlook and Conclusions

• A number of features of the Run I data triggered

the development of a model that includes a scalar boson with the mass in the range 
 250-300 GeV, H, and a mediator, S, with dominance of H→Sh decay

• Predict different levels of contamination in Higgs

measurements

• Maximum in tth→Nℓ searchers, minimum in Wh(→bb),

H→WW→ℓℓ where jet (and lepton) vetoes are applied

SLIDE 35

• Including Run II data observe the following

features, compatible with the model:

• Overshoot rate of tth→Nℓ and undershoot of Wh(→bb),

H→WW→ℓℓ w.r.t. to SM with 3σ tension

• Run II H→ZZ→4ℓ search displays 2σ (ATLAS), 2.5σ (CMS)

in the region of 250-270 GeV

• When normalising the SM to the combined from

Wh(→bb), H→WW→ℓℓ measurements can describe inclusive Higgs pT spectrum with a 3.35σ with respect to this assumption

• The production of 4W leading to 4ℓ is a striking

signature

• Experimental data with 2 and 3 leptons cannot exclude

the production of 4W, as predicted here

SLIDE 36