boosted techniques in susyhacol13.physik.uni-freiburg.de/graduiertenkolleg/talks/gk_javurek.pdf ·...

ATLAS SUSY search in 0-lepton channel with boosted W bosons

Tomas Javureksupervised by:

Gregor Herten, Zuzana Rurikova, Valerio ConsortiUniversity of Freiburg

30th April 2014

Tomas Javurek (UNI Freiburg) Boosted techniques in SUSY 30th April 2014 1 / 18

Introduction

Ongoing events:

paper in Atlas circulation: (ATL-COM-PHYS-2014-094)

int note: (ATL-COM-PHYS-2013-1224)

presented at Atlas Weekly: (https://indico.cern.ch/event/286459/)

today’s open presentation: (https://indico.cern.ch/event/315963/)

In preparation:

pMSSM legacy paper (RunI)

prospects for RunII: (https://indico.cern.ch/event/315501/)


Supersymmetry

supersymmetry:

symmetry of Lagrangianresulting to new particlesand interactions

has to be broken (similarto electroweaksymmetry)

Theoretical motivations forSUSY searches:

dark matter

gauge couplingunification

hierarchy problem

Motivation for SUSY searcheswith ATLAS:

reachable sparticlesproduction cross-section

sensitivity to othertheories (searching for

discrepancy between SM

and data in general)


Definition of ”susy 0-lepton” analysis

proton proton

jet1

jet2

NOlepton!!!

jet3

MET

MissingE

g̃

g̃

χ̃±1

χ̃∓1

p

p

q q

χ̃01

W

qq

χ̃01

W

q̃

q̃p

p

χ̃01

q

χ̃01

q

0-lepton Signal Regions (SRs):

jets: q̃,g̃ decay to q and gmaking jetsMET: because of R-parityconservation, LSP does notdecay further and contributes toMETlepton veto: to be orthogonal toother SUSY analysis

Aiming signals: mSUGRA,simplified models (gg-onestep onthe left), MUED, NUHMG


Selection criteria

ATLAS Work in progress

RequirementChannel

2j 3j 4j 5j 6j2jl 2jm 2jt 2jw 3j 4jw 4jvl 4jl 4jm 4jt 5j 6jl 6jm 6jt 6jvt

Targetted signalq̃q̃ g̃ g̃ q̃g̃ q̃q̃ q̃q̃ q̃q̃ & g̃ g̃ q̃q̃ g̃ g̃

NUHMdirect one-step direct one-step direct one-step one-step

E missT [GeV] > 160

pT(j1) [GeV] > 130pT(j2) [GeV] > 60p(j3) [GeV] > – 60 40 60 60 60

pT(j4) [GeV] > – – 40 60 60 60pT(j5) [GeV] > – – 60 60pT(j6) [GeV] > – – – 60

∆φ(j1,2,(3), E missT > 0.4

∆φ(ji>3, E missT ) > – 0.2

W candidates –2 W → j

–1 W → j

–1 W → jj

E missT /

√HT > 8 15 15 10 10

E missT /meff(Nj) > 0.35 0.3 0.25 0.4 0.25 0.2 0.2 0.2 0.25 0.15

meff(incl.) [GeV] > 800 1200 1600 1800 2200 1100 700 1000 1300 2200 1200 700 1200 1500 1700

Definition of W candidates will come later in this talk.

Powerful executing variables: ETmiss ,mmeff =∑

pT + ETmiss ,ETmiss/mmeff

Two W signal regions SR2jW and SR4jW have been newly developed.


Hadronic boosted W Introduction g̃

g̃

χ̃±1

χ̃∓1

p

p

q q

χ̃01

W

qq

χ̃01

W

There are two Ws present in one-step

simplified models.

They mostly decay hadronically:

W → qq̄ (∼ 68%) .

They can be highly boosted for large

values of ∆m(χ̃± − χ̃0) (⇒x∼1 for

LSP=60GeV)

We defined resolved W = 2 jets and

unresolved W = 1 jet (AntiKt0.4)

(right fig.)

We try to reconstruct Ws in the final

state using the windows in the

invariant mass of one or two jets

(next slide).

χ̃−

χ̃0

W−

q̄

q

Jet

χ̃−χ̃−

χ̃−

χ̃0

W−

q̄

q

Jet2

Jet1

Resolved

Unresolved

W-finderFind unresolved Ws among

the jets. y Find resolved Ws

as a combination of two

closest jets in ∆R among

rest of the jets.


Hadronic boosted W Introduction

(W)TP0 100 200 300 400 500 600 700 800 900 1000

R∆

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8ATLAS Work in progress

truth level study(W)

T) vs. Pq R(q,∆

=1200 GeV g~

m

=360 GeVχ ~

m

=60 GeVLSPm

squark→chargino→LSP,m(LSP) =60[GeV]

(W)TP0 100 200 300 400 500 600 700 800 900 1000

R∆

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8ATLAS Work in progress

truth level study(W)

T) vs. Pq R(q,∆

=1200 GeV g~

m

=1060 GeVχ ~

m

=60 GeVLSPm

gluino→chargino→LSP,m(LSP) =60[GeV]

We have been using AntiKt0.4 jets so far to be consistent with previous0-lepton analysis. The plan is to switch to AntiKt1.0


Hadronic boosted W Introduction

Distribution of invariant mass for

candidates on resolved W when

N(unres.W ) ≥ 1

⇒ 60-100 GeV window was used to

reconstruct W

⇒ SR2jw: N(unres.W ) ≥ 2

⇒ SR4jw: N(unres.W ) ≥ 1, N(res.W ) ≥ 1

Alternative statistical treatmentBackground can be fitted by quadratic

function and χ2-test can be used to

test hypothesis of signal.

) [GeV]k,ji

m(j0 20 40 60 80 100 120 140 160 180 200 220

events

/6GeV

1

10

-1L dt=20.3 fb∫

=8TeV)sData 2012 (

SM Total

)=600

1χ∼

)=1150,m(±

1χ∼

)=1200,m(g~

m(g~

g~

)=600

1χ∼

)=675,m(±

1χ∼

)=700,m(q~

m(q~

q~

Multijet

Z+jets

W+jets

(+X) &single toptt

Diboson

Work in progressATLAS

SR - 4 jets

) [GeV]k,ji

m(j0 20 40 60 80 100 120 140 160 180 200 220D

ATA/MC

00.51

1.52

2.5

Mass of 2 jets [GeV]0 50 100 150 200 250 3000

5

10

15

20

25

30

35

40

all BG

quadr.+N*sigMC fit MC BG

quadr.+sigMC fit MC BG

SM_SS_onestep_600_575_60

Validation Region

not used for fit

+bx+c+sigMC)= 11.982(ax2χ

+bx+c+N.sigMC)= 2.912(ax2χ

+bx+c+N.sigMC) in VR= 1.032(ax2χ

0.30±N= 0.10

Work in progressATLAS-1

L dt = 20.3 fb∫


Interesting distributions for 2jW region

) [GeV]i

m(j40 60 80 100 120 140 160 180 200 220

events/6GeV

1

10

210

310

410 -1L dt = 20.3 fb∫

= 8 TeV)sData 2012 (

SM Total

)=600

1χ∼

)=1150,m(±1

χ∼

)=1200,m(g~

m(g~g~

)=600

1χ∼

)=675,m(±1

χ∼

)=700,m(q~

m(q~q~

Multijet

Z+jets

W+jets

(+X) & single toptt

Diboson


SR - 2 jets

) [GeV]i

m(j40 60 80 100 120 140 160 180 200 220D

ATA/MC

00.51

1.52

2.5

mass of whichever jet in 2jet SRs

) [GeV]i

m(j40 60 80 100 120 140 160 180 200 220

events/6GeV

1

10

210 -1L dt = 20.3 fb∫


SM Total

)=600

1χ∼

)=1150,m(±1

χ∼

)=1200,m(g~

m(g~g~

)=600

1χ∼

)=675,m(±1

χ∼

)=700,m(q~

m(q~q~

Multijet

Z+jets

W+jets

(+X) & single toptt

Diboson


SR - 2 jets

) [GeV]i

m(j40 60 80 100 120 140 160 180 200 220D

ATA/MC

00.51

1.52

2.5

mass of whichever jet, 1 unresolved Wrequired, 2jet SRs

)jets

(Neff

/mmiss

TE

0 0.2 0.4 0.6 0.8 1 1.2

events/0.04

1

10

210

-1L dt = 20.3 fb∫


SM Total

)=600

1χ∼

)=1150,m(±1

χ∼

)=1200,m(g~

m(g~g~

Multijet

Z+jets

W+jets

(+X) & single toptt

Diboson


SR - 2 jets (W)

2jW

)jets

(Neff

/mmiss

TE0 0.2 0.4 0.6 0.8 1 1.2D

ATA/MC

00.51

1.52

2.5

E missT /meff distribution for 2jW region

(incl.) [GeV]effm0 500 1000 1500 2000 2500 3000 3500 4000

events/420GeV

1

10

-1L dt=20.3 fb∫

=8TeV)sData 2012 (

SM Total

)=600

1χ∼

)=1150,m(±

1χ∼

)=1200,m(g~

m(g~g~

Multijet

Z+jets

W+jets

(+X) &single toptt

Diboson


SR - 2 jets (W)

2jW

(incl.) [GeV]effm0 500 1000 1500 2000 2500 3000 3500 4000D

ATA/MC

00.51

1.52

2.5

meff distribution for 2jW region


Interesting distributions for 4jW region

) [GeV]i

m(j40 60 80 100 120 140 160 180 200 220

events/6GeV

1

10

210

310

-1L dt = 20.3 fb∫


SM Total

)=600

1χ∼

)=1150,m(±1

χ∼

)=1200,m(g~

m(g~g~

)=600

1χ∼

)=675,m(±1

χ∼

)=700,m(q~

m(q~q~

Multijet

Z+jets

W+jets

(+X) & single toptt

Diboson


SR - 4 jets

) [GeV]i

m(j40 60 80 100 120 140 160 180 200 220D

ATA/MC

00.51

1.52

2.5

mass of whichever jet in 4jet SRs

) [GeV]k,ji

m(j0 20 40 60 80 100 120 140 160 180 200 220

events

/6GeV

1

10

-1L dt=20.3 fb∫

=8TeV)sData 2012 (

SM Total

)=600

1χ∼

)=1150,m(±

1χ∼

)=1200,m(g~

m(g~

g~

)=600

1χ∼

)=675,m(±

1χ∼

)=700,m(q~

m(q~

q~

Multijet

Z+jets

W+jets

(+X) &single toptt

Diboson


SR - 4 jets

) [GeV]k,ji

m(j0 20 40 60 80 100 120 140 160 180 200 220D

ATA/MC

00.51

1.52

2.5

mass of remaining di-jet combination, 1unresolved W required, 4jet SRs

)jets

(Neff

/mmiss

TE

0 0.2 0.4 0.6 0.8 1 1.2

events/0.04

1

10

210

310-1

L dt = 20.3 fb∫= 8 TeV)sData 2012 (

SM Total

)=600

1χ∼

)=675,m(±1

χ∼

)=700,m(q~

m(q~q~

Multijet

Z+jets

W+jets

(+X) & single toptt

Diboson


SR - 4 jets (W)

4jW

)jets

(Neff

/mmiss

TE0 0.2 0.4 0.6 0.8 1 1.2D

ATA/MC

00.51

1.52

2.5

E missT /meff distribution for 4jW region

(incl.) [GeV]effm0 500 1000 1500 2000 2500 3000 3500 4000

events/100GeV

1

10-1

L dt=20.3 fb∫=8TeV)sData 2012 (

SM Total

)=600

1χ∼

)=675,m(±

1χ∼

)=700,m(q~

m(q~q~

Multijet

Z+jets

W+jets

(+X) &single toptt

Diboson


SR - 4 jets (W)

4jW

(incl.) [GeV]effm0 500 1000 1500 2000 2500 3000 3500 4000D

ATA/MC

00.51

1.52

2.5

meff distribution for 4jW region


Statistical treatmentMain background: Z,W+jets, Top, QCD, Diboson

Control regions (CR): CRY, CRQ, CRW, CRT

Signal regions (SR):

NSRexp = NCR

obsNSR

raw

NCRraw

transfer factornormalized through all CRs via likelihood fit

Likelihood: L(n|µ,s,b,θ) = PSR · PCRY · PCRQ · PCRT · PCRW · Csyst

CR SR Background CR process CR selection

CRY Z (→ νν)+jets γ+jets Isolated photon

CRQ Multijets MultijetsReversed ∆φ(ji ,E

missT ) and E miss

T /√

HT

or E missT /mmeff(Nj) cuts

CRW W (→ `ν)+jets W (→ `ν)+jets 30 GeV < mT (`,E missT ) < 100 GeV, b-veto

CRT tt̄ and single-t tt̄ → bbqq′`ν 30 GeV < mT (`,E missT ) < 100 GeV, b-tag

ATLAS Work in progress


Expected exclusion limits for one-step simplified models,m(LSP) = 60[GeV]

squark mass [GeV]

200 400 600 800 1000 1200

,LS

P)

q~m

(∆

,LS

P)/

± χm

(∆

x=

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1

0χ∼

1

0χ∼

W

+ Wq q→

1

χ∼

1

+χ∼ q q→* q~q~Simplified model,

ATLAS

=8 TeVs, 1

L dt = 20.3 fb∫Work in progress

0lepton combinedm(LSP)=60[GeV]

, 7 TeV)1

Observed limit (4.7 fb

)expσ1 ±Expected limit (

2jW

3jW

5j

6jt+

2jt

6jt+

6jl

5j

3jW

6jl

6jl

4jl

3jW

5j

6jt+

2jt

2jW

6jl5j

4jl

2jW

6jt+

4jt

6jt+

6jt+

4jl

4jt

6jt+

4jl

4jt

3j

4jt

6jt+

4jl

5j

6jt+

6jt+

6jt

5j

4jl 3j

2jW

6jt+

6jt+5j

3jW2jW

2jW

5j

2jt6jt+

4jl

4jl

4jl

6jt+

5j

5j

2jW

4jt

5j

4jt

5j

5j

2jW

3jW

5j

4jl

5j

4jt

6jl

6jt+

5j

3jW

6jl

5j

4jl

6jt+

4jt

6jt+

5j

3jW

3jW

5j

2jW

6jl

5j

4jl2jW

4jl

4jt

6jt+5j

4jt

2jW

2jm

6jt+

4jl

2jW

4jl

4jl

4jt2jl

6jt+

5j

6jt

4jl

5j

4jt

6jt+

6jt+

4jl

5j

5j

6jl

4jt

5j

6jt+

6jl

4jl

6jl

5j

4jl

squark→chargino→LSP,m(LSP) =60[GeV]

gluino mass [GeV]

200 400 600 800 1000 1200 1400 1600

,LS

P)

g~m

(∆

,LS

P)/

± χm

(∆

x=

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1

0χ∼

1

0χ∼ ±

W±

Wqqq q→ 1

±χ∼1

±χ∼ qqq q→ g~g~Simplified model,

ATLAS

=8 TeVs, 1

L dt = 20.3 fb∫Work in progress

0lepton combinedm(LSP)=60[GeV]

, 7 TeV)1

Observed limit (4.7 fb

)expσ1 ±Expected limit (

3jW

3jW

2jW

5j

6jt+

6jt+

4jt

6jl

6jl

6jt+

3jW 2jW

6jl

6jt+

2jW

6jl

3jW

6jt+

5j

6jt+

2jW

2jW

4jt

6jl6jm

4jl

2jW

6jt+

4jt

4jt

6jt

6jt+

6jt+

4jt

6jl

2jW

6jt+

6jt

6jt+

6jl

6jt+

6jt+

6jt+

6jt+

4jl

6jl

6jt+

6jl6jt+

6jl

6jt+

6jt+

6jt+

6jt+

5j

6jm

5j

6jl

6jt+

2jW3jW2jW

2jW

6jt+

6jt+

6jt+

2jW

6jt+

4jl

6jm

6jl

4jl

5j

3jW

6jt+

2jW

6jt+

6jl

2jW

6jt+

6jl

6jt+

6jt+

6jl5j

6jt+

3jW

6jt+

6jt+

3jW

6jt+

4jl

6jl

6jt

6jt+

4jt

5j

6jt+

6jt+

5j

6jt+

6jt+

2jW4jl

6jt+

6jt+

6jt+

6jt+

6jl

6jm

2jW4jl

2jW

6jt+

6jt

3jW

2jW

3jW

3jW

6jt+

6jt+

2jW

6jt+

6jt+

2jW

6jl

3jW

6jt

6jt+

6jl

6jl

6jt+

2jW

4jl

6jt+

4jm

6jt+

4jl

3jW

4jm

5j

6jt6jl

6jt+

5j

6jt

6jl

6jl

6jl

6jt+

6jt+

6jt+

2jW

3jW

5j

4jl

6jl

5j

4jt

6jt+

6jl

2jW

5j

4jl

6jl

6jl

6jt+

2jW

6jt+

gluino→chargino→LSP,m(LSP) =60[GeV]

Older results with 3jW. Boosted SRs improve exlusion limit for

x ≡ ∆(mg̃,LSP)∆(mχ̃−,LSP) ∼ 1!


Ongoing studies


Motivation for implementation of MT 2 variable

M2T 2 def.

minp1+p2=MET

[max [M2T (W1, p1),M2

T (W2, p2)]]

g̃

g̃

χ̃±1

χ̃∓1

p

p

q q

χ̃01

W

qq

χ̃01

W

MT 2 is designed toreconstruct mass ofparticle which is producedin pair and decays intoinvisible (ν, χ̃0)

in our case: target is toreconstruct mass ofintermediate gauginos:

χ̃− →W−χ̃0

χ̃02 → Hχ̃0

1

and use MT 2 to suppressthe background


MT 2 distribution in unres-res + unres-unres W channels

) [GeV]2W1(WTm20 200 400 600 800 1000

events/20GeV

1

10

210

-1L dt = 20.3 fb∫

= 8 TeV)sData 2012 (SM Total

700,690,60q~q~

700,460,60q~q~

800,790,60q~q~

1200,1190,60g~g~

MultijetZ+jetsγ+ jetsW+jetsttbar & single topDiboson

InternalATLAS

SR

) [GeV]2W1

(WT2

m0 200 400 600 800 1000D

ATA/MC

00.51

1.52

2.5

) [GeV]2W1(WTm20 200 400 600 800 1000

events/20GeV

1

10

-1L dt = 20.3 fb∫


700,690,60q~q~

700,460,60q~q~

800,790,60q~q~

1200,1190,60g~g~

MultijetZ+jetsγ+ jetsW+jetsttbar & single topDiboson

InternalATLAS

SR

) [GeV]2W1

(WT2m0 200 400 600 800 1000D

ATA/MC

00.51

1.52

2.5

Selection:

all preselection 0-letpton cutsusedpT (j1) >130GeV,pT (j2) >60GeV, E miss

T >160GeVqcd redc.: ∆(φ)(j1,2,3) >0.4E miss

T /meff >0.3 (only bottomfig.)

Interesting:

see gg-1step point (niceseparation from background)MT 2 > 500. suppress QCDsee effect of E miss

T /meff >0.3(bottom figure on the left)


Correlation between meff and MT 2

410

310

210

effm

0 500 1000 1500 2000 2500 3000

T2

M

0

200

400

600

800

1000

sig_meff_mt2_corrsig_meff_mt2_corr

gg-onestep mg̃ = 1200,mχ̃+ =1190,mlsp = 60[GeV]

1

10

210

effm

0 500 1000 1500 2000 2500 3000

T2

M

0

200

400

600

800

1000

allbgallbg

Sum of all SM backgrounds,

MT 2 > 300?


Significance, combination of cuts

meff : meff >1500[GeV]E miss

T /meff : E missT /meff >0.3

MT 2: MT 2 >500[GeV]

meff meff ,MT 2 E missT /meff E miss

T /meff ,MT 2 E missT /meff ,meff E miss

T /meff ,meff ,MT 2

allbg 21770 149.2 546.5 70.3 36.1 12.4q̃q̃ 14.3 8.2 16 11.3 8.1 7.0g̃ g̃ 14 10.5 10.5 10.1 9.9 9.3s/√

b + s(q̃q̃) 0 0.7 0.7 1.3 1.2 1.6s/√

b + s(g̃ g̃) 0 0.8 0.5 1.1 1.5 2.0

Impact of combination of cuts on significance.g̃ g̃ -1step: m(gl) = 1200,m(char) = 1190,m(lsp) = 60.q̃q̃-1step: m(sq) = 800,m(char) = 790,m(lsp) = 60.At least 1 unresolved and 1 resolved W or 2 unresolved W required. Selection same as onprevious slides.

Best significancies achieved when combining all three cuts.


Conclusions&Plans

Conclusions:

boosted W regions have been developeddata/MC ratio is fairly close to one for all distributions in SRs and CRssuch new SRs improve expected exclusion limits

Plans:

finishing 0-lepton paper and work on pMSSM paperpreparing boosted 0-lepton analysis for 14 TeVstudying possibility of using shape fits on W mass peakstudying jet substructure and MT 2


back-up


SUSY analysis using some boosted technique

0-lepton: ATL-COM-PHYS-2013-1224

0-lepton stop: ATL-COM-PHYS-2013-1092

1-lepton stop: ATL-COM-PHYS-2013-1490 (boosted top tagging,AntiKt10 Jets)

boosted 3jet RPV: ATL-COM-PHYS-2012-793 (7TeV, 8TeV inprogress)


meff distribution in unres-res + unres-unres W channels

GeV0 500 1000 1500 2000 2500 3000 3500 4000

events

/ 1

00

1

10

210

1L dt = 20.3 fb∫


700,690,60q~

q~

700,460,60q~

q~

800,790,60q~

q~

1200,1190,60g~

g~

MultijetZ+jetsγ + jetsW+jetsttbar & single topDiboson

InternalATLAS

SR

GeV

0 500 1000 1500 2000 2500 3000 3500 4000DA

TA

/ M

C

00.5

11.5

22.5

meff distribution before E missT /meff

cut with same selection as on

previous slides

GeV0 500 1000 1500 2000 2500 3000 3500 4000

events

/ 1

00

1

10

1L dt = 20.3 fb∫


700,690,60q~

q~

700,460,60q~

q~

800,790,60q~

q~

1200,1190,60g~

g~

MultijetZ+jetsγ + jetsW+jetsttbar & single topDiboson

InternalATLAS

SR

GeV

0 500 1000 1500 2000 2500 3000 3500 4000DA

TA

/ M

C

00.5

11.5

22.5

E missT /meff > 0.3, meff is

unfortunately as powerful as MT 2,

but their combination could give

improvement!


Correlation between MET/meff and MT 2

-310

-210

-110

effm

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

T2

M

0

200

400

600

800

1000

sig_metmeff_mt2_corrsig_metmeff_mt2_corr

MET/

gg-onestep mg̃ = 1200,mχ̃+ =1190,mlsp = 60[GeV]

1

10

210

310

effMET/m

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

T2

M

0

200

400

600

800

1000

allbgallbg

Sum of all background, MT 2 > 300?


boosted techniques in susyhacol13.physik.uni-freiburg.de/graduiertenkolleg/talks/gk_javurek.pdf ·...

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