Search for DiBoson Resonances in the Semi-Leptonic Final State at 13 TeV with CMS

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Search for DiBoson Resonances in

the Semi-Leptonic Final State at 13 TeV with CMS

Dermot Moran (Universidad Autónoma de Madrid) On behalf of the CMS Collaboration

VIII CPAN Days

2016 Zaragoza

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DiBoson Resonance

Many BSM theories predict the existence of heavy particles (X) which decay to pairs of vector bosons ( V = Z/W )

→ Graviton, Heavy Higgs, W´, Z´

Search for local enhancement in ZV invariant mass distribution Using 2.7 f

^-1

of 13 TeV Data

BSM Signal

ZV Invariant Mass SM Z+Jets

V Z

X

1

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Hadronic V Reconstruction

V ^{Boosted V} ^Single

Merged Jet (AK8) Jet1 (AK4)

Jet2 (AK4) Resolved V

Pt

Run 1 Higgs ->ZV ->2l2q Search (JHEP 10 (2015) 144)

Resolved Boosted

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Boosted V Tagging

Discriminate V from QCD Jet using : Jet Grooming (Pruning, Softdrop) Remove soft and wide angle constituents

Pushes QCD to lower mass Improve V mass resolution

EXO-15-002

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Boosted V Tagging

Discriminate V from QCD Jet using : N-Subjettiness τ

_N

Quantifies how consistent Jet is with having N Subjets τ

₂

/ τ

₁

used to identify 2 prong substructure

(LO)

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Boosted V and Top Tagging

X qq Search EXO-16-030

Merged Jets with 3 prong substructure Merged Jets with 2 prong substructure

X tt Search B2G-15-002

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Leptonic Z Candidate :

→ e⁺e^- or μ⁺μ^- in Z Mass Window

→ Single Lepton Triggers with Isolation

Hadronic V Candidate :

→ Boosted and Resolved Selections used

X->ZV Candidate Search

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Boosted V Selection

Z+Jets from MC (NLO + LO) Top from eu Data

SM ZV from MC

B2G-16-010 P_T > 200 GeV

τ₂₁^{< 0.45}

Leptonic Z + Merged Jet Candidates

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Resolved V Selection

NLO Z+Jets gives much improved description of many variables with respect to Run 1

P_T > 100 GeV

Leptonic Z + DiJet Candidates

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X → ZV Selection

Boosted Category

(Primary) Resolved Category

(If no Boosted Candidate)

Signal

Region Signal

Region Side

band Sideband

Sideband Sideband

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B Tagging Categorisation

Z Hadronic decays have relatively large Branching Ratio to Heavy Flavour

B-Tagging of Jets/Subjets using Secondary Vertex and IP Info (Loose and Medium CSV Tags)

Increase signal sensitivity using Tagged and UnTagged categories : L+M for Resolved, 1 M for Boosted

Most b-like SubJet Most b-like Jet

10

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Fit to m _ZV in Sideband

Verify Background prediction + constrain

norm in Signal region Correction of Z+Jets MC norm and shape

to data in each category

Boosted UnTagged

Boosted Tagged

Resolved Tagged Resolved

UnTagged

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Fit to m _ZV in Signal Region

Resolved Tagged Resolved

UnTagged

Resolved Tagged Boosted

UnTagged

Correction of Z+Jets MC norm and shape

to data in each category

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m _ZV in Signal Region

Excess consistent with X->ZV Signal at 650 GeV

Model Randall Sundrum Graviton Bulk Graviton

Local p-value 3.4 σ 3.9 σ

Including LEE 2.9 σ 3.5 σ

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650 GeV Signal Candidate

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Graviton Model Limits

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X->ZV High Mass Search Strategy

SR

SB SB

Accounts for Close By Lepton Effects : → Lepton Trigger without Isolation

→ Looser Lepton Reconstruction

Only Merged Jets used τ₂₁used to define 2 categories

Background determination : → Parametric fit to m_ZV in SB → Apply α to get SR prediction α = Z+Jets SR / Z+ Jets SB

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m _ZV in Signal Region (High Mass Strategy)

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Graviton Model Limits

HIGH MASS STRATEGY

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Conclusions

Search for X->ZV Resonances using 2.7 f

^-1

of 13TeV Data Using Merged Jets with substructure and DiJets

Observed an excess consistent with Signal at 650 GeV 36 f

^-1

Search for DiBoson Resonances in the Semi-Leptonic Final State at 13 TeV with CMS