Searches for vector-like quarks with the ATLAS detector

(1)

Searches for vector-like quarks with the ATLAS detector

X CPAN Days

29 – 31 October 2018, Salamanca

Tal van Daalen on behalf of the ATLAS Collaboration

(2)

Vector-Like Quark phenomenology

• Heavy top/bottom partners with similarly transforming left- and right-handed chirality components under SU(2) (vector-like)

• Predicted by many BSM theories, such as Higgs compositeness, extra-dimensions, etc.

• Charge (+2/3,-1/3) (singlet) or (+2/3,-1/3), (+5/3,+2/3), (-1/3,-4/3) (doublet)

• Collider production either in pairs or single

• Pair production via strong production, only mass dependent

• Single production via EW interaction, depending on coupling strength, potentially dominant at high VLQ masses

• Decay to Higgs-/vector-bosons and 3 rd gen. quark

• Leads to very rich phenomenology and consequently requires very wide search program

2

ν

¯ ν

t T

¯b/¯t b/t

W/Z

q q¯^′

g

T

T ¯ W − , H, Z

¯ b, t, ¯ ¯ t b, t, t W + , H, Z

g g

X CPAN Days 2018 | Tal van Daalen

(3)

VLQ phenomenology: decay configurations

33

BR ( T → Wb )

BR ( T → Ht )

Doublet configuration

Singlet configuration

T

T ¯ W

⁻

¯ b b

W

⁺

g g T

T ¯ Z

¯ t t

Z

g g

The vector-like T branching ratio triangle (similar for vector-like B)

• Any BR configuration possible

(4)

44

BR ( T → Wb )

BR ( T → Ht )

Doublet configuration

T

T ¯ W

⁻

¯ b b

W

⁺

g g T

T ¯ Z

¯ t t

Z

g g

B OOSTED

TOP QUARK ( S )

H IGH - P T B - JET ( S )

• Each BR corner produces unique final-states

(5)

55

BR ( T → Wb )

BR ( T → Ht )

Doublet configuration

T

T ¯ W

⁻

¯ b b

W

⁺

g g T

T ¯ Z

¯ t t

Z

g g

B OOSTED

TOP QUARK ( S )

• ATLAS analyses designed to target specific final-state to cover the entire BR triangle

X CPAN Days 2018 | Tal van Daalen

(6)

66

BR ( T → Wb )

BR ( T → Ht )

T

T ¯ W

⁻

¯ b b

W

⁺

g g T

T ¯ Z

¯ t t

Z

g g

B OOSTED

TOP QUARK ( S )

• H(bb)t+X

• Trilepton / SS dilepton (also VLB)

H → bb H → WW*

X CPAN Days 2018 | Tal van Daalen

(7)

77

BR ( T → Wb )

BR ( T → Ht )

T

T ¯ W

⁻

¯ b b

W

⁺

g g T

T ¯ Z

¯ t t

Z

g g

B OOSTED

TOP QUARK ( S )

• H(bb)t+X

• All hadronic (also VLB)

• Z(ll)t/b+X (also single production and VLB)

• Z(νν)t+X H → bb

H → WW*

Z → ll Z → νν Z → qq

• ATLAS analyses designed to target specific final-state to cover the entire BR triangle

(8)

88

BR ( T → Wb )

BR ( T → Ht )

T

T ¯ W

⁻

¯ b b

W

⁺

g g T

T ¯ Z

¯ t t

Z

g g

B OOSTED

TOP QUARK ( S )

• H(bb)t+X

• All hadronic (also VLB)

• Z(ll)t/b+X (also single production and VLB)

• Z(νν)t+X

• W(lv)b/t+X (also VLB) W → qq

W → lv H → bb

H → WW*

Z → ll Z → νν Z → qq

• Each BR corner produces unique final-states

(9)

0t, 0H, 5j, 3b 1t, 0H, 5j, 3b 0t, 1H, 5j, 3b 1t, 1H, 5j, 3b 2t, 0-1H, 5j, 3b³ 2H, 5j, 3b³0t, ³ 4b³0t, 0H, 5j, 4b³1t, 0H, 5j, 4b³0t, 1H, 5j, 4b³2tH, 5j, ³ 0t, 0H, 6j, 2b, HM 1t, 0H, 6j, 2b, HM 0t, 1H, 6j, 2b, HM 2tH, 6j, 2b, HM³ 0t, 0H, 6j, 3b, LM 1t, 0H, 6j, 3b, LM 0t, 1H, 6j, 3b, LM 0t, 0H, 6j, 3b, HM 1t, 0H, 6j, 3b, HM 0t, 1H, 6j, 3b, HM 2tH, 6j, 3b³ 4b, LM³0t, 0H, 6j, 4b, HM³0t, 0H, 6j, 4b³1t, 0H, 6j, 4b³0t, 1H, 6j, 4b³2tH, 6j, ³

Data / Bkg 0 0.5 1 1.5

2

Events

1 10 10

2

10

3

10

4

ATLAS

= 13 TeV, 36.1 fb

-1

s

Validation regions Post-fit (Bkg-only)

Data t t + light-jets

³ 1c + t

t t t + ³ 1b

t

Non-t Total Bkg unc.

1-lepton 0-lepton

[GeV]

m

T

700 800 900 1000 1100 1200 1300 1400 1500

) [pb] T T ® (pp s

-3

10

-2

10

-1

10 1

10 Theory (NNLO prediction ± 1 s ) 95% CL observed limit 95% CL expected limit

s

± 1 95% CL expected limit

s

ATLAS

= 13 TeV, 36.1 fb

-1

s

1-lepton + 0-lepton combination Ht) = 1

® BR(T

Pair production searches

9

Ht+X – JHEP 07 (2018) 089 T

T ¯ H

t ¯ t H

g g

• Search in high jet, b-jet multiplicity events for Higgs bosons and boosted top-quarks

• 1-lepton and 0-lepton (high MET) channels, split between jet, b-jet, and tagged boosted object multiplicity (total 34 signal regions)

• Also sets limits on exotic 4-top production in EFT and extra-dimensions context

• Main background from ttbar+≥1b

• Final limits on m T of

1.3 TeV for doublet and 1.4 TeV for 100% Ht decays

• 0.99 TeV coverage on entire BR triangle!

[GeV]

m

T

700 800 900 1000 1100 1200 1300 1400 1500

) [pb] T T ® (pp s

-3

10

-2

10

-1

10 1

10 Theory (NNLO prediction ± 1 s ) 95% CL observed limit 95% CL expected limit

s

ATLAS

= 13 TeV, 36.1 fb

-1

s

1-lepton + 0-lepton combination SU(2) doublet

cont ribut ion

(10)

Pair production searches

• Search for non-Z trilepton or same-sign dilepton events

• Targets T→Ht (→WW*t) and BB→WtWt modes

• Signal region categorization based on lepton, jet, b-jet multiplicity and kinematic cuts

• Also sets limits on SM and exotic 4-top production and exotic same-sign top production

• Main backgrounds from fake/non-prompt leptons, tt+V, charge misidentification

• Estimated in dedicated validation regions

• Limits over 1.2 TeV for both m T and m B

10

Trilepton / same-sign dilepton – arXiv:1807.11883* T

T ¯ W − , H, Z

¯ b, ¯ t, ¯ t t H

g g

Event Yield

0 5 10 15 20 25

Data Fake/non-prompt Charge mis-ID

Z t t

H t t

W t t Dibosons

t t t t Other bkg

1TeV (44 fb) T

T CI (40 fb) t t t t

Total bkg unc.

ATLAS

= 13 TeV, 36.1 fb-1

s

SS dilepton / trilepton VLQ/4top Signal Regions

SR1b2l SR2b2l SR3b2l_LSR3b2l SR1b3l SR2b3l SR3b3l_LSR3b3l Data / Pred. 0

1 2

X CPAN Days 2018 | Tal van Daalen

400 600 800 1000 1200 1400

[GeV]

m

T -2

10

-1

10 1 10

) [pb] T T ® (pp s

Observed limit Expected limit

s

± 1 s

± 2 Theory (NNLO) All limits at 95% C.L.

= 13 TeV, 36.1 fb

-1

s

SS dilepton / trilepton + b-jets ATLAS

400 600 800 1000 1200 1400

[GeV]

T5/3

m

-2

10

-1

10 1 ) [pb] T T ® (pp s

5/35/3

10

Observed limit Expected limit

s

± 1 s

± 2 Theory (NNLO) All limits at 95% C.L.

= 13 TeV, 36.1 fb

-1

s

SS dilepton / trilepton + b-jets ATLAS

*Submitted to JHEP

(11)

[TeV]

m

VLQ

0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4

) [pb] T T → (pp σ

1

10

−

1 10

ℬ( T→H t) = 1 95% CL limits Expected Observed

1 σ

± 2 σ

±

QQ Cross Section pp→

Theory Uncertainty

ATLAS

= 13 TeV, 36.1 fb-1

s

[TeV]

m

VLQ

0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4

) [pb] B B → (pp σ

1

10

−

1 10

ℬ( B→H b ) = 1 95% CL limits Expected Observed

1 σ

± 2 σ

±

QQ Cross Section pp→

Theory Uncertainty

ATLAS

= 13 TeV, 36.1 fb-1

s

Pair production searches T

T ¯ W − , H, Z

¯ b, t, ¯ t ¯ b, t, t W + , H, Z

g g

11

All hadronic – arXiv:1808.01771*

• Search for any fully hadronic decay mode of TT pair with boosted top-quarks and Higgs- or vector bosons

• Boosted object tagging on reclustered jets using multi-class DNN classifier

• Main background from multi-jet event (data-driven)

• Final discriminant using matrix element method

• Limits around 1 TeV for both m T and m B

V ) P (

− 2 − 1 0 1

Fraction / 0.1

0 0.05 0.1 0.15

0.2 V Higgs-boson jet -boson jet Top-quark jet Background jet

ATLAS Simulation

= 13 TeV s vRC jets

| < 2.5

|η

< 2000 GeV 150 < pT

m > 40 GeV

) ( t P

− 3 − 2 − 1 0 1 2

Fraction / 0.1

0 0.05 0.1 0.15

0.2

-boson jet V

Higgs-boson jet Top-quark jet Background jet

= 13 TeV s vRC jets

| < 2.5

|η

< 2000 GeV 150 < pT

m > 40 GeV

H ) P (

− 2 − 1 0 1 2

Fraction / 0.1

0 0.05 0.1 0.15

0.2 V -boson jet

Higgs-boson jet Top-quark jet Background jet

= 13 TeV s vRC jets

| < 2.5

|η

< 2000 GeV 150 < pT

m > 40 GeV

*Submitted to Phys. Rev. D

(12)

T

T ¯ Z

t ¯ t

Z

g g

12

Zt/b+X – arXiv:1806.10555*

• Search for high-p T Z →ll in dilepton and trilepton events

• On-shell Z boson reconstruction

• Exclusive dilepton and trilepton signal regions

• Further splitting based on large-R jet multiplicity

• Main backgrounds from ttV and diboson

• Final limits around 1 TeV for singlet (m T and m B ), 1.2 TeV for doublet and 1.3(1.2) TeV for

100% Zt(Zb) for m T (m B )

• Also single production

interpretation!

(see later)

[GeV]

H

T

800 1000 1200 1400 1600 1800 2000

Data / Bkg.

^0.5

1 1.5

Events / 100 GeV

5 10 15 20

25 ^ATLAS13 TeV, 36.1 fb-1

0-1J PP 2l 1-large-R jet SR Post-Fit

Data (900 GeV) x 5 B Singlet B Z+jets tt Other Uncertainty

[GeV]

S

T

500 1000 1500 2000 2500 3000

Data / Bkg.

^0.5 1 1.5

Events / 400 GeV

20 40 60 80 100 ATLAS

13 TeV, 36.1 fb-1

l

³ 3 PP SR Post-Fit

Data

(900 GeV) x 5 B

Singlet B +X t t Diboson

t t Z+jets Other Uncertainty

[GeV]

m

T

600 800 1000 1200 1400

) [pb] T T ® (pp s

-3

10

-2

10

-1

10 1 10 10

2

Individual expected limits 0-1J

l

PP 2 PP 2l³ 2J PP ³ 3l

Theory(NNLO+NNLL) Obs. Limit

95% CL Exp. Limit s

± 1 95% CL Exp.

s

± 2 95% CL Exp.

ATLAS 13 TeV, 36.1 fb

-1

Doublet (XT) T

T

Combination

[GeV]

m

T

600 800 1000 1200 1400

) [pb] T T ® (pp s

-3

10

-2

10

-1

10 1 10 10

2

Individual expected limits 0-1J

l

PP 2 PP 2l³ 2J PP ³ 3l

Theory(NNLO+NNLL) Obs. Limit

95% CL Exp. Limit s

± 1 95% CL Exp.

s

± 2 95% CL Exp.

ATLAS 13 TeV, 36.1 fb

-1

Zt) = 100%

BR(T ® T T

Combination

(13)

• Search for T → Z(νν)t events in high MET 1-lepton channel

• Boosted top-quark identification with reclustered jets

• Main backgrounds from ttbar, single top, and W+jets

• Estimated from dedicated control regions

• Final limits on m T of 900 GeV for singlet, 1 TeV for doublet scenario, and 1.1 TeV for 100% Zt decays

13

Z( νν )t/b+X – JHEP 08 (2017) 052 T

T ¯ Z

t ¯ t

Z

g g

TVR WVR STVR SR

tot s exp - n obs n 1 -

0 1

Events

0 20 40 60 80 100 120 140 160 180 200

220 t t 2L

´ 1.05

1.05

t

´

1L1 t t

1.05

1L

´

t t

0.70

W+jets

´

Single top +V t t Diboson Data Total pred.

0 5 10 15 ATLAS 20

= 13 TeV, 36.1 fb

-1

s

miss T,sig

H

5 10 15 20 25 30 35

Data/Pred. 0.5 1 1.5

miss T,sig

H

Events / 3

0 20 40 60 80 100 120 140

160 Data Total pred.

1.05 1L´ t t

Single top

0.70

´ W+jets

Others

ATLAS

= 13 TeV, 36.1 fb-1

s

control region t

t

m

_T

[GeV]

800 1000 1200 1400

) [pb] T T ® (pp s

-2

10

-1

10

1

Observed limit

Expected limit s

± 1 Expected limit

2 s Expected limit ±

production T T

ATLAS

= 13 TeV, 36.1 fb

-1

s

Limit at 95% CL

SU(2) doublet

miss

Zt+X 1l+E

T

[GeV]

m

T

800 1000 1200 1400

) [pb] T T ® (pp s

-2

10

-1

10

1

Observed limit

Expected limit s

± 1 Expected limit

s

± 2 Expected limit

production T T

ATLAS

= 13 TeV, 36.1 fb

-1

s

Limit at 95% CL

)=100%

® Zt T B(

miss

Zt+X 1l+E

T

(14)

14

Wt+X – JHEP 08 (2018) 048 & Wb+X – JHEP 10 (2017) 141

• Search for boosted W bosons in 1-lepton events

• Separate analysis strategy for TT and BB searches

• TT search: reconstruct leptonic T mass

• BB search: split between reconstructed final-state or BDT strategy

• Region categorization based on jets, b-jets, and large-R jets

• Limits of 1.2 (1.1) TeV for singlet m T (m B ) and 1.35 (1.25) TeV for 100% Wb(Wt) decays on m T (m B )

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

BDT discriminant 0.8

0.9 1 1.1

Data / Pred.

1 10 102

103

104

105

106

Events / bin

ATLAS = 13 TeV s 36.1 fb-1

BDTSR

Post-Fit

Data m^WtWtB =1.3 TeV t

t W+jets

Single top Diboson V

t

t Z+jets

Multi-jet Total uncertainty

[GeV]

lep

m

T

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Data / Pred.

0.2

0.6 1 1.4 1.8

Events / bin

0 10 20 30 40 50 60

ATLAS = 13 TeV s 36.1 fb-1

Signal Region Pre-Fit ℬ(T→W b) = 1

Data mT= 1TeV

t t

+jets W Single top Others Uncertainty

400 600 800 1000 1200 1400

[GeV]

had

mB 0.2

0.6 1 1.4

Data / Pred.

0 5 10 15 20 25 30 35

Events / bin

ATLAS = 13 TeV s 36.1 fb-1

RECOSR

Post-Fit

Data m^WtWtB =1.3 TeV t

t W+jets

Single top Others Total uncertainty

[GeV]

m T

500 600 700 800 900 1000 1100 1200 1300 1400

) [pb] T T ® (pp s

-3

10

-2

10

-1

10 1 10

Theory Observed Limit Expected Limit s

± 1 Expected

s

± 2 Expected All limits at 95% CL

Wb+X 1-lepton

® T T

ℬ (T → W b) = 1 ATLAS

= 13 TeV, 36.1 fb

-1

s

(15)

• Individual ATLAS searches have complementary sensitivity

• Important to cover largest possible portion of parameter space

• Limits here presented in BR triangle with exclusion planes

• Next slide: summary plots show limits on m T and m B on a BR triangle for a mass grid:

• For each of the individual analyses shown previously

• For full combination

15

Limits and combinations

(16)

16

0 0.2 0.4 0.6 0.8 0

0.2 0.4 0.6 0.8

Unphysical

= 1200 GeV m

T

0 0.2 0.4 0.6 0.8

Unphysical

= 1300 GeV m

T

0 0.2 0.4 0.6 0.8 1

Unphysical

= 1400 GeV m

T

0.2 0.4 0.6 0.8

Unphysical

= 1050 GeV m

T

Unphysical

= 1100 GeV m

T

Unphysical

= 1150 GeV m

T

0.2 0.4 0.6 0.8

Unphysical

= 950 GeV m

T

Unphysical

= 1000 GeV m

T

0.2 0.4 0.6 0.8

Unphysical

= 800 GeV m

T

Unphysical

= 900 GeV m

T

1

® Wb) BR(T

Ht) ® BR(T

ATLAS

= 13 TeV, 36.1 fb

-1

s

SU(2) doublet SU(2) singlet Exp. exclusion Obs. exclusion

[arXiv:1707.03347]

)b+X n W(l

[arXiv:1803.09678]

H(bb)t+X

[arxiv:1705.10751]

)t+X n n Z(

[CERN-EP-2018-171]

Trilep./same-sign

[arXiv:1806.10555]

Z(ll)t/b+X

[CERN-EP-2018-176]

All-had

0 0.2 0.4 0.6 0.8 0

0.2 0.4 0.6 0.8

Unphysical

= 1200 GeV m

B

0 0.2 0.4 0.6 0.8

Unphysical

= 1300 GeV m

B

0 0.2 0.4 0.6 0.8 1

Unphysical

= 1400 GeV m

B

0.2 0.4 0.6 0.8

Unphysical

= 1050 GeV m

B

Unphysical

= 1100 GeV m

B

Unphysical

= 1150 GeV m

B

0.2 0.4 0.6 0.8

Unphysical

= 950 GeV m

B

Unphysical

= 1000 GeV m

B

0.2 0.4 0.6 0.8

Unphysical

= 800 GeV m

B

Unphysical

= 900 GeV m

B

1

® Wt) BR(B

Hb) ® BR(B

ATLAS

= 13 TeV, 36.1 fb

-1

s

SU(2) (T,B) doublet SU(2) (B,Y) doublet SU(2) singlet

Exp. exclusion Obs. exclusion

[arXiv:1806.01762]

)t+X n W(l

[CERN-EP-2018-171]

Trilep./same-sign

[arXiv:1806.10555]

Z(ll)t/b+X

[CERN-EP-2018-176]

All-had

• Before combination: VLT at entire BR triangle

excluded at 1100 GeV • Before combination: VLB at entire BR triangle excluded at 900 GeV

VLT pair production VLB pair production

arXiv:1808.02343

X CPAN Days 2018 | Tal van Daalen cont ribut ion

(Submitted to PRL)

(17)

Pair production searches

17

0 0.2 0.4 0.6 0.8 0

0.2 0.4 0.6 0.8

Unphysical

= 1200 GeV m

T

0 0.2 0.4 0.6 0.8

Unphysical

= 1300 GeV m

T

0 0.2 0.4 0.6 0.8 1

Unphysical

= 1400 GeV m

T

0.2 0.4 0.6 0.8

Unphysical

= 1050 GeV m

T

Unphysical

= 1100 GeV m

T

Unphysical

= 1150 GeV m

T

0.2 0.4 0.6 0.8

Unphysical

= 950 GeV m

T

Unphysical

= 1000 GeV m

T

0.2 0.4 0.6 0.8

Unphysical

= 800 GeV m

T

Unphysical

= 900 GeV m

T

1

® Wb) BR(T

Ht) ® BR(T

ATLAS

= 13 TeV, 36.1 fb

-1

s

VLQ Combination

SU(2) doublet SU(2) singlet

95% CL expected exclusion

95% CL observed exclusion

0 0.2 0.4 0.6 0.8 0

0.2 0.4 0.6 0.8

Unphysical

= 1200 GeV m

B

0 0.2 0.4 0.6 0.8

Unphysical

= 1300 GeV m

B

0 0.2 0.4 0.6 0.8 1

Unphysical

= 1400 GeV m

B

0.2 0.4 0.6 0.8

Unphysical

= 1050 GeV m

B

Unphysical

= 1100 GeV m

B

Unphysical

= 1150 GeV m

B

0.2 0.4 0.6 0.8

Unphysical

= 950 GeV m

B

Unphysical

= 1000 GeV m

B

0.2 0.4 0.6 0.8

Unphysical

= 800 GeV m

B

Unphysical

= 900 GeV m

B

1

® Wt) BR(B

Hb) ® BR(B

ATLAS

= 13 TeV, 36.1 fb

-1

s

VLQ Combination

SU(2) (T,B) doublet SU(2) (B,Y) doublet SU(2) singlet

95% CL expected exclusion

95% CL observed exclusion

• After combination: VLT at entire BR triangle

excluded at 1300 GeV • After combination: VLB at entire BR triangle excluded at 1000 GeV

VLT pair production VLB pair production

X CPAN Days 2018 | Tal van Daalen cont ribut ion arXiv:1808.02343

(Submitted to PRL)

(18)

Single production searches

Phenomenology and analysis strategies

• Electroweak production, coupling dependent

• Allows for more model-dependent interpretations, besides usual model-independent interpretation

• Different final-states than pair production require different analysis strategy

• Less busy final-state, presence of forward-jets from initial-state quark

ℓ

t T

¯ b/ t ¯ b/t

W/Z

q q ¯ ′

g

Z

Potential for VLQ reconstruction

18

(19)

Single production searches

Single T/B → Z(ll)t/b – arXiv:1806.10555*

• Search for high-p T Z →ll in dilepton and trilepton events

• On-shell Z boson reconstruction

• Dilepton: fully reconstruct VLQ mass if top-tagged jet present

• Trilepton: less straight-forward, use kinematic variables

• Main backgrounds from ttV and Z+jets

• Final limits on m T between 1 and 1.2 TeV (depending on couplings)

• Limits presented both model-dependent and -independently

ℓ

t T

¯ b/ ¯ t b/t

W/Z

q q ¯

^′

g

Z

19

[GeV]

m

T

600 800 1000 1200 1400 1600 1800 2000

tZ) [pb] ® BR(T ´ Tbq) ® (pp s

-2

10

-1

10 1

Individual expected limits l

SP 2 SP ³ 3 l

(singlet model) 0.25

» Zt)

® BR(T

= 0.5 k

T

NLO QCD,

Obs. Limit 95% CL Exp. Limit

s

± 1 95% CL Exp.

s

± 2 95% CL Exp.

ATLAS 13 TeV, 36.1 fb

-1

Single-T Production Combination

800 1000 1200 1400 1600 1800

[GeV]

m

T

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

| q |sin

L

1

95% CL Exp. ^±²^s

s

± 1 95% CL Exp.

95% CL Exp. Limit Observed Limit

ATLAS

13 TeV, 36.1 fb

-1

(20)

Single production searches

Single B → H( → γγ)b – ATLAS-CONF-2018-024

• Search for Higgs → diphoton events with additional b-jet

• Combination of diphoton and b-jet used to reconstruct VLQ mass

• Main background from continuous diphoton+jets spectrum

• Data-driven estimation from sideband regions

• Recent result with 80 fb -1

• Limits set on m B at 1.2 TeV for fixed coupling strength

γ

b B

¯ b b

Z

q q

g

H

20

(21)

Summary and the future of VLQ searches

• Very complete vector-like quark program within ATLAS

• Individual and complementary searches all push limits beyond TeV scale

• Combinations produce even more powerful limits and ensure full coverage of parameter space

• Full Run-2 efforts underway!

• Pair production has been main focus in ATLAS so far

• Limits extend very far, combination proves very powerful

• Searches will continue with improved and more sophisticated strategies

• Single production efforts are expanding, as full Run-2 dataset of ~150 fb -1 integrated luminosity allows sensitivity to masses well beyond current pair production limits

• Potential unusual interpretations, exotic decays, and internal combinations under full consideration

• Discussions with theory community always prove fruitful (e.g. this public meeting)

21

X CPAN Days 2018 | Tal van Daalen

(22)

Questions?

22

Tal van Daalen

(23)

Backup material

23

Tal van Daalen

(24)

Ht+X – analysis strategy

• Search conducted in both 1L and 0L channels

• Preselection requirements:

• Region splitting based on multiplicities of:

• Small-R jets

• b-jets (at 77% WP)

• Top-tagged large-R jets:

• pT > 300 GeV, mass > 140 GeV, # subjets >= 2

• Higgs-tagged large-R jets:

• pT > 300 GeV, 105 GeV < mass < 140 GeV

• # subjets = 2 for pT < 500 GeV

• # subjets <= 2 for pT > 500 GeV

• In 0L further splitting based on m b T,min to enhance S/B

• Final signal discrimination given by Profile likelihood fit on shape of

effective mass: 24

(25)

q D

0

)/

q q - (

- 2 - 1.5 - 1 - 0.5 0 0.5 1 1.5 2 0.23)

± 1b normalisation (0.90

³ + t t

+light-jets parton shower t

t

+light-jets generator t

t

Jet Energy Resolution term) Pile-up offset (N

PV

term) Pile-up offset (p

T

correction 1c NNLO top-p

T

³ + t t

1b rad.

³ + t t

1c norm.

³ + t t

³ 2tH) V+b-jets norm. (0l,

³ 2tH) V-jets norm. (0l,

1b generator

³ + t t

extrap.

b-tag high-p

T

³ 2tH) QCD norm. (0l,

Statistical only

µ D

- 0.2 0 0.2

µ : Pre-fit impact on

q + D = q

q q = q - D q µ : Post-fit impact on

q + D = q

q q = q - D q Nuis. Param. Pull

ATLAS

= 13 TeV, 36.1 fb

-1

s

doublet (1.2 TeV) T

Ht+X – results on VLTs

T

• Observed (expected) 95%

CL limits set on m T :

25

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

® Wb) BR(T 0.1

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Ht) ® BR(T

700 800 900 1000 1100 1200 1300 1400

95% CL mass limit [GeV]

ATLAS

= 13 TeV, 36.1 fb

-1

s

1-lepton + 0-lepton combination Observed limit

1000 1100

1200 1300 1400

SU(2) doublet

SU(2) singlet

(26)

CMS results

T mass (GeV)

800 1000 1200 1400 1600 1800

)[pb] T (T s

-2

10

-1

10 1

(tH,tZ) = 0.5 B

(bW) = 2 B

1+2+3 leptons

(13 TeV) 35.9 fb

-1

CMS 95% CL upper limits

Observed Expected 68% expected 95% expected (theo.) T

® T pp

T mass (GeV)

800 1000 1200 1400 1600 1800

)[pb] T (T s

-2

10

-1

10 1

(tZ) = 0.5 B (tH) = B

1+2+3 leptons

(13 TeV) 35.9 fb

-1

Observed Expected 68% expected 95% expected (theo.) T

® T pp

B mass (GeV)

800 1000 1200 1400 1600 1800

)[pb] B (B s

-2

10

-1

10 1

10 B (tW) = 2 B (bH,bZ) = 0.5 1+2+3 leptons

(13 TeV) 35.9 fb

-1

Observed Expected 68% expected 95% expected (theo.) B

® B pp

B mass (GeV)

800 1000 1200 1400 1600 1800

)[pb] B (B s

-2

10

-1

10 1

10 B (bH) = B (bZ) = 0.5 1+2+3 leptons

(13 TeV) 35.9 fb

-1

Observed Expected 68% expected 95% expected (theo.) B

® B pp

26

B (tH)

0 0.2 0.4 0.6 0.8 1

(bW) B

0 0.2 0.4 0.6 0.8 1

900 1000 1100 1200 1300

1260 1260 1260 1240 1240 1240

1220 1220 1200 1200 1210

1190 1180 1180 1180

1160 1150 1160

1140 1140

1150

95% CL expected T quark mass limit (GeV)

(13 TeV) 35.9 fb

-1

CMS

B (tH)

0 0.2 0.4 0.6 0.8 1

(bW) B

0 0.2 0.4 0.6 0.8 1

900 1000 1100 1200 1300

1300 1290 1290 1280 1270 1270

1280 1260 1260 1250 1250

1240 1230 1220 1220

1190 1180 1180

1160 1150

1140

95% CL observed T quark mass limit (GeV)

(13 TeV) 35.9 fb

-1

CMS

B (bH)

0 0.2 0.4 0.6 0.8 1

(tW) B

0 0.2 0.4 0.6 0.8 1

900 1000 1100 1200 1300

930 930 920 920 920 930

1050 1040 1040 1040 1050

1100 1100 1100 1110

1160 1160 1160

1190 1190

1240

95% CL expected B quark mass limit (GeV)

(13 TeV) 35.9 fb

-1

CMS

B (bH)

0 0.2 0.4 0.6 0.8 1

(tW) B

0 0.2 0.4 0.6 0.8 1

900 1000 1100 1200 1300

960 960 950 920 910 910

1080 1080 1080 1070 1080

1150 1150 1140 1160

1190 1180 1180

1220 1200

1240

95% CL observed B quark mass limit (GeV)

(13 TeV) 35.9 fb

-1

CMS

(27)

ATLAS VLQ combination – more details

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

® Wb) BR(T 0.1

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Ht) ® BR(T

1300 1320 1340 1360 1380 1400 1420

ATLAS

= 13 TeV, 36.1 fb -1

s

VLQ combination Observed limit

1320 1350

1375 1400

27

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

® Wt) BR(B 0.1

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Hb) ® BR(B

1000 1050 1100 1150 1200 1250 1300 1350 1400

ATLAS

= 13 TeV, 36.1 fb -1

s

VLQ combination Observed limit

1100

1200

1300

SU(2) (T,B) doublet

SU(2) (B,Y) doublet

SU(2) singlet

(28)

ATLAS VLQ combination – more details

0 0.2 0.4 0.6 0.8 0

0.2 0.4 0.6 0.8

-2

10

-1

10 1 10

Unphysical

= 1200 GeV m

T

0 0.2 0.4 0.6 0.8

Unphysical = 1300 GeV m

T

0 0.2 0.4 0.6 0.8 1

Unphysical

= 1400 GeV m

T

0.2 0.4 0.6 0.8

Unphysical

= 1050 GeV m

T

Unphysical = 1100 GeV m

T

Unphysical

= 1150 GeV m

T

0.2 0.4 0.6 0.8

Unphysical

= 950 GeV m

T

Unphysical = 1000 GeV m

T

0.2 0.4 0.6 0.8

Unphysical

= 800 GeV m

T

Unphysical

= 900 GeV m

T

- 2

10

- 1

10 1

1 10

® Wb) BR(T

Ht) ® BR(T

ATLAS

= 13 TeV, 36.1 fb

-1

s

VLQ Combination

s

VLQ

s / on

Observed 95% CL limit

28

0 0.2 0.4 0.6 0.8 0

0.2 0.4 0.6 0.8

-2

10

-1

10 1 10

Unphysical

= 1200 GeV m

B

0 0.2 0.4 0.6 0.8

Unphysical

= 1300 GeV m

B

0 0.2 0.4 0.6 0.8 1

Unphysical

= 1400 GeV m

B

0.2 0.4 0.6 0.8

Unphysical

= 1050 GeV m

B

Unphysical

= 1100 GeV m

B

Unphysical

= 1150 GeV m

B

0.2 0.4 0.6 0.8

Unphysical

= 950 GeV m

B

Unphysical

= 1000 GeV m

B

0.2 0.4 0.6 0.8

Unphysical

= 800 GeV m

B

Unphysical

= 900 GeV m

B

- 2

10

- 1

10 1

1 10

® Wt) BR(B

Hb) ® BR(B

ATLAS

= 13 TeV, 36.1 fb

-1

s

VLQ Combination

s

VLQ

s / on

Observed 95% CL limit

SU(2) (T,B) doublet

SU(2) (B,Y) doublet

SU(2) singlet