Searches for New Physics in Boosted Topologies

Takuya Nobe*

on behalf of ATLAS Collaboration*University of Tokyo

Rencontres de Moriond QCD and High Energy Interactions

La Thuile, 21/3/2016

2

CERN Courier

LHC@13TeV!

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100 10001

10

100

gg Σqq qg

WJS2013

ratios of LHC parton luminosities: 13 TeV / 8 TeV

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MX (GeV)

MSTW2008NLO

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Early run-2 physics= focus on high-mass

LHC@13TeV!

Heavy resonances in high energy pp collisions

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Heavy Vector Triplet Z’k/MPl=1

• Many beyond the SMs predict high-mass VV/Vh/Zγ/hh/tt resonances(V : denotes W and Z boson)

• Model-independent search is important

JHEP 09 (2014) 060

• A key is tagging high-pT objects from high-mass resonances

• Large-R jet

• ΔR of 2 particles from a 2-body decay :

• At high-pT region, two quarks from W/Z decay cannot be separated by standard Anti-kT R=0.4 algorithm

• Reconstruct boosted W/Z→qq, h→bb, and t→qqb as one jet with large cone size (Anti-kT, R=1.0)

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Boosted object tagging

R = 2M/pT

• Pile-up and soft-QCD subtraction

• Remove sub-constituents of large-R jet if f<5%

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Trimming

ATLAS-PHYS-PUB-2015-033

※ f=pT(sub)/pT(J)

Trimming!

Jet sub-structure• Using sub-constituents’ kinematics inside the large-R jet, we can define

good variables to reject backgrounds more• For W/Z-tagging:

• Using D2β=1 variable (see details in backup)

• Mass + D2β=1 cut : 50% signal efficiency v.s. b.g. rejection is factor ~50

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arXiv:1510.05821

2-prong-like

Dibosons resonance@8 TeV

• Full-hadronic channel : local significance : 2.6-3.4σ, global 2.5σ＠2TeV

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arXiv:1512.05099JHEP 12 (2015) 55• After the combination

with leptonic modes the local significance is ~2σ

• High-centrality to reject QCD b.g.

• Data-driven b.g. estimation

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VV→qqqq→JJ

����pT,J1 � pT,J2

pT,J1 + pT,J2

���� < 0.15

・

・

13TeV spectra�y (JJ) < 1.2

• 1-lepton + missing ET (W mass constraint) + boson-tagged large-R jet

• b-jet veto to suppress top quarks• Newly applied relative boson-pT cut :

pT(V)/m(VV) > 0.4 improves the sensitivity by 10% w.r.t. run-1

WV→lνJ

ATLAS-CONF-2015-073

ATLAS-CONF-2015-068ATLAS-CONF-2015-071

ATLAS-CONF-2015-075

Limits on diboson resonances

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Full-hadronic

1-lepton

2-lepton(Z→ll + J)

missing ET(Z→νν + J)

m<~1TeV excluded

m<850GeV excluded

Limits on diboson resonances

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Limits on diboson resonances

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m<1.7TeV excluded

Vh resonances• Boosted higgs-tagging technique

• At least one b-jets inside large-R jet using a new b-tagging technique with ‘track-jets’, R=0.2 (see details in backup)

• Large-R jet mass peaks at 125 GeV

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ATLAS-CONF-2015-074

Wh→lνJ Zh→llJZh→ννJ

Limits on Vh resonance

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m<~1.48TeV excluded

m<~1.49TeV excluded

m<~1TeV excluded

MET + Jbb Analysis

lν + Jbb Analysis ll + Jbb Analysis

3-prong-like

Boosted top tagging

• 80% signal efficiency v.s. b.g. rejection is factor ~4

• b-jet tagging using ‘track-jet’ can reduce the b.g. more while keeping high efficiency

15

arXiv:1603.03127

ATL-PHYS-PUB-2015-053

boosted top

1lepton + missing ET

at least 1 b-jets • Mass and sub-structure• pT>300GeV

top anti-top resonance

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electron channel

muon channel

Limit on Z’→tt cross-section

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m<~2.1TeV excluded

Vector like quark (VLQ) / four top quarks search

• Large-R jets to probe boosted higgs/top (no sub-structure cut is applied; m>100GeV)+ 1-lepton + ET

miss + multi-jets

• Signal regions are categorized into 11 sub-regions using number of boosted jets, number of b-jets and number of small-R jets

• Final discriminant : effective mass, meff = Σ pT,i; i is all of lepton, jets and ETmiss

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Limits on VLQ TT and tttt productions

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m<900GeV is exluded m<1.45TeV is exluded

Limit on branching fraction of VLQ

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ADD GKK + g/q − ≥ 1 j Yes 3.2 n = 2 Preliminary6.86 TeVMD

ADD non-resonant ℓℓ 2 e, µ − − 20.3 n = 3 HLZ 1407.24104.7 TeVMS

ADD QBH→ ℓq 1 e, µ 1 j − 20.3 n = 6 1311.20065.2 TeVMth

ADD QBH − 2 j − 3.6 n = 6 1512.015308.3 TeVMth

ADD BH high!pT ≥ 1 e, µ ≥ 2 j − 3.2 n = 6, MD = 3 TeV, rot BH ATLAS-CONF-2016-0068.2 TeVMth

ADD BH multijet − ≥ 3 j − 3.6 n = 6, MD = 3 TeV, rot BH 1512.025869.55 TeVMth

RS1 GKK → ℓℓ 2 e, µ − − 20.3 k/MPl = 0.1 1405.41232.68 TeVGKK mass

RS1 GKK → γγ 2 γ − − 20.3 k/MPl = 0.1 1504.055112.66 TeVGKK mass

Bulk RS GKK →WW → qqℓν 1 e, µ 1 J Yes 3.2 k/MPl = 1.0 ATLAS-CONF-2015-0751.06 TeVGKK mass

Bulk RS GKK → HH → bbbb − 4 b − 3.2 k/MPl = 1.0 ATLAS-CONF-2016-017475-785 GeVGKK mass

Bulk RS gKK → tt 1 e, µ ≥ 1 b, ≥ 1J/2j Yes 20.3 BR = 0.925 1505.070182.2 TeVgKK mass

2UED / RPP 1 e, µ ≥ 3 b, ≥ 3 j Yes 3.2 Tier (1,1), BR(A(1,1) → tt) = 1 Preliminary1.46 TeVKK mass

SSM Z ′ → ℓℓ 2 e, µ − − 3.2 ATLAS-CONF-2015-0703.4 TeVZ′ mass

SSM Z ′ → ττ 2 τ − − 19.5 1502.071772.02 TeVZ′ mass

Leptophobic Z ′ → bb − 2 b − 3.2 Preliminary1.5 TeVZ′ mass

SSM W ′ → ℓν 1 e, µ − Yes 3.2 ATLAS-CONF-2015-0634.07 TeVW′ mass

HVT W ′ →WZ → qqνν model A 0 e, µ 1 J Yes 3.2 gV = 1 ATLAS-CONF-2015-0681.6 TeVW′ mass

HVT W ′ →WZ → qqqq model A − 2 J − 3.2 gV = 1 ATLAS-CONF-2015-0731.38-1.6 TeVW′ mass

HVT W ′ →WH → ℓνbb model B 1 e, µ 1-2 b, 1-0 j Yes 3.2 gV = 3 ATLAS-CONF-2015-0741.62 TeVW′ mass

HVT Z ′ → ZH → ννbb model B 0 e, µ 1-2 b, 1-0 j Yes 3.2 gV = 3 ATLAS-CONF-2015-0741.76 TeVZ′ massLRSM W ′

R→ tb 1 e, µ 2 b, 0-1 j Yes 20.3 1410.41031.92 TeVW′ mass

LRSM W ′R→ tb 0 e, µ ≥ 1 b, 1 J − 20.3 1408.08861.76 TeVW′ mass

CI qqqq − 2 j − 3.6 ηLL = −1 1512.0153017.5 TeVΛCI qqℓℓ 2 e, µ − − 3.2 ηLL = −1 ATLAS-CONF-2015-07023.1 TeVΛ

CI uutt 2 e, µ (SS) ≥ 1 b, ≥ 1 j Yes 20.3 |CLL | = 1 1504.046054.3 TeVΛ

Axial-vector mediator (Dirac DM) 0 e, µ ≥ 1 j Yes 3.2 gq=0.25, gχ=1.0, m(χ) < 140 GeV Preliminary1.0 TeVmA

Axial-vector mediator (Dirac DM) 0 e, µ, 1 γ 1 j Yes 3.2 gq=0.25, gχ=1.0, m(χ) < 10 GeV Preliminary650 GeVmA

ZZχχ EFT (Dirac DM) 0 e, µ 1 J, ≤ 1 j Yes 3.2 m(χ) < 150 GeV ATLAS-CONF-2015-080550 GeVM∗

Scalar LQ 1st gen 2 e ≥ 2 j − 3.2 β = 1 Preliminary1.07 TeVLQ mass

Scalar LQ 2nd gen 2 µ ≥ 2 j − 3.2 β = 1 Preliminary1.03 TeVLQ mass

Scalar LQ 3rd gen 1 e, µ ≥1 b, ≥3 j Yes 20.3 β = 0 1508.04735640 GeVLQ mass

VLQ TT → Ht + X 1 e, µ ≥ 2 b, ≥ 3 j Yes 20.3 T in (T,B) doublet 1505.04306855 GeVT mass

VLQ YY →Wb + X 1 e, µ ≥ 1 b, ≥ 3 j Yes 20.3 Y in (B,Y) doublet 1505.04306770 GeVY mass

VLQ BB → Hb + X 1 e, µ ≥ 2 b, ≥ 3 j Yes 20.3 isospin singlet 1505.04306735 GeVB mass

VLQ BB → Zb + X 2/≥3 e, µ ≥2/≥1 b − 20.3 B in (B,Y) doublet 1409.5500755 GeVB mass

VLQ QQ →WqWq 1 e, µ ≥ 4 j Yes 20.3 1509.04261690 GeVQ mass

T5/3 →Wt 1 e, µ ≥ 1 b, ≥ 5 j Yes 20.3 1503.05425840 GeVT5/3 mass

Excited quark q∗ → qγ 1 γ 1 j − 3.2 only u∗ and d∗, Λ = m(q∗) 1512.059104.4 TeVq∗ mass

Excited quark q∗ → qg − 2 j − 3.6 only u∗ and d∗, Λ = m(q∗) 1512.015305.2 TeVq∗ mass

Excited quark b∗ → bg − 1 b, 1 j − 3.2 Preliminary2.1 TeVb∗ mass

Excited quark b∗ →Wt 1 or 2 e, µ 1 b, 2-0 j Yes 20.3 fg = fL = fR = 1 1510.026641.5 TeVb∗ mass

Excited lepton ℓ∗ 3 e, µ − − 20.3 Λ = 3.0 TeV 1411.29213.0 TeVℓ∗ mass

Excited lepton ν∗ 3 e,µ, τ − − 20.3 Λ = 1.6 TeV 1411.29211.6 TeVν∗ mass

LSTC aT →W γ 1 e, µ, 1 γ − Yes 20.3 1407.8150960 GeVaT mass

LRSM Majorana ν 2 e, µ 2 j − 20.3 m(WR ) = 2.4 TeV, no mixing 1506.060202.0 TeVN0 mass

Higgs triplet H±± → ℓℓ 2 e, µ (SS) − − 20.3 DY production, BR(H±±L → ℓℓ)=1 1412.0237551 GeVH±± mass

Higgs triplet H±± → ℓτ 3 e,µ, τ − − 20.3 DY production, BR(H±±L→ ℓτ)=1 1411.2921400 GeVH±± mass

Monotop (non-res prod) 1 e, µ 1 b Yes 20.3 anon−res = 0.2 1410.5404657 GeVspin-1 invisible particle mass

Multi-charged particles − − − 20.3 DY production, |q| = 5e 1504.04188785 GeVmulti-charged particle mass

Magnetic monopoles − − − 7.0 DY production, |g | = 1gD , spin 1/2 1509.080591.34 TeVmonopole mass

Mass scale [TeV]10−1 1 10√s = 8 TeV

√s = 13 TeV

ATLAS Exotics Searches* - 95% CL ExclusionStatus: March 2016

ATLAS Preliminary"L dt = (3.2 - 20.3) fb−1

√s = 8, 13 TeV

*Only a selection of the available mass limits on new states or phenomena is shown. 21

Summary• 13TeV pp collisions data opens a whole new world!• Early run-2 = focus on high mass region, where our sensitivity is already

better than 8 TeV• Boosted object tagging is an important key to probe high-mass new physics• Reported the latest ATLAS search results for VV/Vh/tt/TT/tttt resonances

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Dibosons resonance ttbar resonance

Backup slides

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• Decay of W/Z : 2-prong-like

• A variable:is used to enhance signals

D2β=1 and τ32

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ECF2 =X

ij

pT,ipT,j�Rij

ECF1 =X

i

pT,i

ECF3 =X

ijk

pT,ipT,jpT,k�Rij�Rjk�Rki

There’re 2 high-pT constituents with large ΔRij; and no the other constituents with high-pT: → large ECF2 but small ECF3

D�=12 = ECF3

✓ECF1

ECF2

◆3

• Decay of top : 3-prong-like

• A variable:is used to enhance signals

⌧32 =

Pi pT,i min (�Ra1,i,�Ra2,i, Ra3,i)P

i pT,i min (�Ra1,i,�Ra2,i)

3-prong-like signal shows small τ32

b-tagging in dense environment

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Standard technique (outside-in)

New technique (inside-out)

1. Reconstruct jet using energy deposits in calorimeter 2. b-tagging using ‘matched’ tracks and vertices3. Good energy resolution but large contaminations from

non-b particles’ tracks in dense hadronic environmenti.e. many other charged particles are expected near b-quark from boosted top/higgs(high pT=small ΔR)

1. Anti-kT algorithm seeded by inner detector tracks are employed (track-jet R=0.2)

2. Good angular resolution / high secondary vertex reconstruction efficiency even in dense environment

3. Worse energy resolution:Track-jet is used only for b-tagging and jet energy is measured in calorimeter

b-tagging in dense environment• Data/MC difference is taken into account by ‘b-tag scaling factor’,

which is estimated using isolated b-quarks from top quark decay

• After applying the scaling factor, data agree well with MC even if b-jet is associated with large-R jet (g→bb enriched sample by muon-in-jet tagging)

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ATLAS-CONF-2016-002

double b-tag efficiency for large-R jet (assuming g→bb)

pT and mass scales agree with MC after the b-tagging

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Full-hadronic dibosons resonance search

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ZV→ννJ• Large missing ET + large-R jet

• Normalizations of W/Z+jets b.g. are determined in 1-/2-lepton control regions (common with lvJ/llJ)

• Final discriminant : transverse mass

The other dibosons spectra• 2-lepton (Z mass constraint) + large-R jet

• Variable cone-size lepton isolation depending on pT

• pT(V)/m(VV) > 0.4

ZV→llJ

Z+γ resonance

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dilepton+γ Large-R jet +γ

hh resonance• hh→bbbb channel (3 b-tag or 4 b-tag)

• Using boosted higgs tagging technique

• Data-drived multi-jet b.g. estimation (b-veto → b-tag)

• Combined with resolved channel

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VLQ search: event yields in each category

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LHC@13TeV!

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• c.f. total 8TeV data in 2012 : 20/fb

q q

W/Z

topo-clusters

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large-R jet

protonproton

Illustration of W/Z tagging

lepton missing ET

q qW/Z

sub-jet

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large-R jet

protonproton

Illustration of W/Z tagging

lepton missing ET

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large-R jet

protonproton

Illustration of W/Z tagging

Trimmingremove sub-jet if f<5%f = pT(sub)/pT(J)

ATLAS-PHYS-PUB-2015-033

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large-R jet

protonproton

Illustration of W/Z tagging

Trimmingremove sub-jet if f<5%f = pT(sub)/pT(J)

ATLAS-PHYS-PUB-2015-033

Jet sub-structurerequiring 2-prong-like (small D2)