Search for Dark Matter in Mono-Jet Topology at ATLAS · +Dark Matter at colliders 3 Maria Giulia...

+Search for Dark

Matter in Mono-Jet Topology at ATLAS

Maria Giulia RattiUniversità degli Studi di Milano and I.N.F.N.

on behalf of the ATLAS collaboration

WO RKSHO P O N T HE STAN DARD MO DEL AN D BEYO N D

C O RFU, 0 3 -0 9 -2 017

+ Dark Matter at colliders 2

Maria Giulia Ratti - [email protected] 03/09/17

¤ Dark Matter constitutes ~85% of total matter in the Universe DM and SM interact other than gravitationallyà weakly

establish complementary strategies to detect it

Detection at colliders

Indirect detection

Direct detection

+ Dark Matter at colliders 3


¤ Dark Matter constitutes ~85% of total matter in the Universe DM and SM interact other than gravitationallyà weakly

establish complementary strategies to detect it

Detection at colliders

SM

Search for direct production of DM pairsMissing transverse momentum (MET) recoiling against a “visible” X=jet,ɣ,W,Z,hMET + jet (or ‘Mono-jet’) best channel if X comes from ISR

MET + X

+Mono-jets at ATLAS 4


no electronsno muons

MET> 250 GeV

up to 3 more jetspT > 30 GeVjet

pT> 250 GeV|η|<2.4

tight quality

+

PVNumber of primary vertices N

0 5 10 15 20 25 30

RM

S [G

eV]

ymis

s,E

xmis

sTS

T E

0

10

20

30

Data

ee) MC→ Z(

ATLAS Preliminary = 13 TeVsData 2016,

-1 ee, 8.5 fb→Z

> 20 GeVT

0 jets, p

Data

ee) MC→ Z(

⟩µ⟨10 12 14 16 18 20 22 24 26 28 30

⟩ >

20

GeV

)T

(pje

tN⟨

012

34567

89

10

MC Powheg+Pythia8MC, JVT > 0.59datadata, JVT > 0.59

ATLAS Preliminary (2015 + 2016 data)-1 = 13 TeV, 13.3 fbs

selectionµµ→Z

Mono-jets at ATLAS Experimental challenges

5


no electronsno muons

MET> 250 GeV

jetpT> 250 GeV

|η|<2.4tight quality

up to 3 more jetspT > 30 GeV

Δ𝜙 > 0.4à suppress fake

MET from multi-jets

à remove pile-up jetsà suppress non-

collision background

à be pile-up robust

Njets vs pile-up

MET resolution vs pile-up

Mono-jet rate vs Jet𝜙

03/09/17Maria Giulia Ratti - [email protected]

6

Mono-jet analysis2015+2016 data

ATLAS-CONF-2017-060

+ SM backgrounds and Analysis Strategy

¤ Look for an excess of events wrt SM prediction essential to find the best way to estimate the

Z(vv)+jets background use simultaneously the shape of the “MET” in

W/Z+jets & ttbar control regions to constrain the background in the SR

this requires to know higher order corrections to W/Z+jets

à use state-of-the art perturbative calculations


¤ Crucial to measure the SM background precisely Z(vv)+jets (55-70%), W(lv)+jets (35-20%), ttbar (~3%) Diboson (~2%) Multi-jet and non-collision backgrounds

ETmiss + μ + jet

ETmiss + jet

7

V+jets control regions

NEW indicates a change wrt 2015 analysis

data-drivenfrom MC

ETmiss + e + jet

ETmiss + μμ + jet

>=1b-tags

nob-tags

Control Regions

Signal Region

following approach by Lindert et al. https://arxiv.org/pdf/1705.04664.pdf

Top CR

+ Background estimation

¤ Binned simultaneous fit of the in 4 CRs and the SR observable captures the pT

V in the various regions

¤ In addition perform 10 counting experiments for reinterpretation


pTZ ~ MET pT

W ~ pT(MET+l) pTZ ~ pT(MET+l+l)

L ~μNsig + kWZ(NZ(vv)+ NW(lv) + NZ(ll)) + ktop(Nttbar + Nt) + NVV + Nmultijet + NNCB

8We refer to the observable as“ET

miss” both in SR and CRs

a single k-factor for V+jetsa single k-factor for top

¤ V+jets simulations combined with perturbative correctionsà NLO QCD and nNLO EW accuracyà thanks to a one-dimensional reweighting 𝒙 ≡ pT

𝑽

our MC theory prediction

pTV distribution inour MC

arxiv: 1705.04664

+ Control Regions


9

300 400 500 600 700 800 900 1000 1100 1200

[Eve

nts/

GeV

]m

iss

TdN

/dE

1−10

1

10

210

310

410

510

610

Data 2015+2016Standard Model

) + jetsνν →Z() + jetsν l→W(

ll) + jets→Z( + single toptt

Dibosons

ATLAS-1 = 13 TeV, 36.1 fbs

Preliminary

) Control Regionν e→W(>250 GeVmiss

T(j1)>250 GeV, E

Tp

[GeV]missTE

300 400 500 600 700 800 900 1000 1100 1200

Dat

a / S

M

0.91

1.11.2300 400 500 600 700 800 900 1000 1100 1200

[Eve

nts/

GeV

]m

iss

TdN

/dE

1−10

1

10

210

310

410

510Data 2015+2016Standard Model



Dibosons


Preliminary

) Control Regionνµ →W(>250 GeVmiss

T(j1)>250 GeV, E

Tp

[GeV]missTE

300 400 500 600 700 800 900 1000 1100 1200

Dat

a / S

M

0.91

1.1

300 400 500 600 700 800 900 1000 1100 1200

[Eve

nts/

GeV

]m

iss

TdN

/dE

1−10

1

10

210

310




Dibosons


Preliminary

) Control Regionµµ→Z(>250 GeVmiss

T(j1)>250 GeV, E

Tp

[GeV]missTE

300 400 500 600 700 800 900 1000 1100 1200

Dat

a / S

M

0.81

1.2300 400 500 600 700 800 900 1000 1100 1200

[Eve

nts/

GeV

]m

iss

TdN

/dE

2−10

1−10

1

10

210

310




Dibosons


Preliminary

Top Control Region>250 GeVmiss

T(j1)>250 GeV, E

Tp

[GeV]missTE

300 400 500 600 700 800 900 1000 1100 1200

Dat

a / S

M

0.5

1

1.5

~ pTW

W (μv) + jets W (ev) + jets

~ pTZ

Z(μμ) +jets Top (semi-leptonic)

~ pTW

+ Results


10

Signal Region

v Major systematic components: lepton efficiency jet/MET scale&reso

v Reached high precision in the bkg prediction uncertainty 𝜎bkg

~2% at ‘low’ MET ~7% in the TeV regime

... no significant deviations from SM prediction

à sizeable improvement wrt to 2015 analysis:

~ halved 𝜎bkg

300 400 500 600 700 800 900 1000 1100 1200

[E

vents

/GeV

]m

iss

TdN

/dE

1−10

1

10

210

310

410

510

610

710Data 2015+2016

Standard Model

) + jetsνν →Z(

) + jetsν l→W(

ll) + jets→Z(

+ single toptt

Dibosons

multijets + ncb

) = (500, 495) GeV0

)χ∼, b

~m(

)= (400, 1000) GeVmed

, MDM

(m

=6400 GeVD

ADD, n=4, M


Preliminary

Signal Region>250 GeV

miss

T(j1)>250 GeV, E

Tp

[GeV]miss

TE300 400 500 600 700 800 900 1000 1100 1200

Da

ta /

SM

0.8

1

1.2

+

[GeV]AZm

0 1000 2000

[GeV

]χ

m

0

500

1000 expσ 2 ±Expected limit

)expσ 1 ±Expected limit (

)PDF, scaletheoryσ 1 ±Observed limit (

Perturbativity Limit

Relic Density (MadDM)-1 = 13 TeV, 3.2 fbsATLAS

ATLAS Preliminary-1 = 13 TeV, 36.1 fbs

Axial-Vector MediatorDirac Fermion DM

= 1.0χ

= 0.25, gqg95% CL limits

χ

= 2 m

AZm

[GeV]χm1 10 210 310 410

]2-p

roto

n) [c

mχ (

SDσ

42−10

39−10

36−10

33−10

30−10PICO-60Axial-Vector Mediator

90% CL limits

Dirac Fermion DM = 1.0χ

= 0.25, gqg


Exclusion limit in mDM – mA plane

Exclusion limit in DM-proton 𝜎 – mDM

excluded by ATLAS

excluded by directdetection

excluded by ATLAS

Dark Matter Results


11A axial-vector spin-1jet from ISRgSM,=0.1 gDM=0.25

ATLAS/CMS DM forum recommendations:arxiv: 1507.00966

(a selection of)

+ Dark Matter Results


12

Exclusion limits in mDM – mA plane

Exclusion limits in DM-proton 𝜎 – mDM

excluded by ATLAS

excluded by directdetection

ATLAS/CMS DM forum recommendations:arxiv: 1507.00966

A axial-vector spin-1jet from ISRgSM,=0.1 gDM=0.25

MET + X Dijet + X

(a selection of)

+More DM/SUSY/Add Interpretations 13


[GeV]1t

~m300 400 500 600

[Ge

V]

10χ∼

m

250

300

350

400

450

500

550

600

650-1=13 TeV, 36.1 fbsPreliminary

1

0χ∼c→

1t~

production, 1t~1t~

All limits at 95% CL

ATLAS

-1=13 TeV, 3.2 fbsATLAS

)theory

SUSYσ1±Observed limit (

)expσ1 ±Expected limit (

expσ2 ±Expected limit

c+ m

0

1χ∼

< m

1t~m

W+ m

b+ m

0

1χ∼

> m

1t~m

SUSY SUSY

SUSY SUSY

[GeV]1t

~m300 400 500 600

[G

eV

]10

χ∼m

200

250

300

350

400

450

500

550


1

0χ∼ bff’→

1t~

production, 1t~1t~


ATLAS

)theory

SUSYσ1 ±Observed limit (



0

1χ∼

< m

1t~m

[GeV]1b

~m400 600 800

[G

eV

]10

χ∼m

100

200

300

400

500

600

700

800


1

0χ∼ b→

1b~

production, 1

b~

1b~


ATLAS

)theory

SUSYσ1 ±Observed limit (



b + m0

1χ∼

< m1b

~m

[GeV]1

q~m

200 400 600 800

[G

eV

]10

χ∼-m 1q~

m

6

8

10

12

14

16

18

20

22

24

)theorySUSY

σ1 ±Observed limit (



-1=13 TeV, 3.2 fbsATLAS

-1=13 TeV, 36.1 fbs

Preliminary

1

0χ∼ q→

1q~ production,

1q~

1q~


ATLAS

ADD

[GeV]VZm

0 1000 2000

[GeV

]χ

m

0

500

1000 expσ 2 ±Expected limit

)expσ 1 ±Expected limit (

)PDF, scaletheoryσ 1 ±Observed limit (

Relic Density (MadDM)


Vector MediatorDirac Fermion DM

= 1.0χ

= 0.25, gqg95% CL limits

χ

= 2 m

VZm

DM

vector interaction

+ Conclusions

¤ ATLAS mono-jet analysis with 2015+2016 data

sizeable sensitivity improvement wrt to previous search paper with more DM interpretations soon to be out…

¤ More data ahead, new challenges try to go lower in MET (work in region where trigger is not at

plateau?) improve precision with constraint from ɣ+jets data use additional discriminating variables


14

q g

q̄

η

gqχ

χ

χ̄

gqχ

Stay tuned !

https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2017-060/ATLAS-CONF-2017-060à

+


15

BACK-UP

+ Useful links

¤ ATLAS Mono-jet 2015+2016 results: https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2017-060/

¤ ATLAS Exotics summary plots: https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CombinedSummaryPlots/EXOTICS/

¤ ATLAS Exotics public results: https://twiki.cern.ch/twiki/bin/view/AtlasPublic/ExoticsPublicResults

¤ ATLAS Jet/Etmiss public results: https://twiki.cern.ch/twiki/bin/view/AtlasPublic/JetEtmissPublicResults

¤ LHC DM Working group documents: Benchmark models: https://arxiv.org/abs/1507.00966 Presentation of results for MET+X: https://arxiv.org/abs/1603.04156 Presentation of results for MET+X and Dijet: http://arxiv.org/pdf/1703.05703

¤ Precise predictions for V+jets dark matter backgrounds: https://arxiv.org/abs/1705.04664

16


+ Dark Matter Models


A

qg

χ

q̄ χ̄

gq gχ

Simplified models to describe Dark Matter pair production (ATLAS/CMS DM forum 1507.00966)

Axial-vector (and vector) mediator and pseudo-scalar mediators, s-channel

jet from ISR

mediator has spin 1, couples to all generations of quarks

4 free parameters: mA, mχ, gq, g𝛘 minimal mediator width

Scalar colored mediator, t-channel

jet either from ISR or from mediator decay

mediator has spin 0, couples to first two generations of quarks

3 free parameters: m𝛈, mχ, gqχ

minimal mediator width

17

q g

q̄

η

gqχ

χ

χ̄

gqχq

g

ηgqχ

χ

χ̄

gqχ

q

q

gqχ

η

g

η

χ

χ̄

gqχ

q

+ SUSY and ADD


SUSY Squark pair production

compressed scenarios: pT of quark and LSP are low, system is boosted by ISR jet

parameters: squark mass, four scenarios considered:

ADD Large Extra-Dimensions

n additional dimensions compatcified are assumed, where gravity propagates, scale MD is the fundamental scale of the 4+n-dim theory

gravitons escaping the extra dimensions => ETmiss

limits on MD as a function of the n := #extra-spatial dimensions assumed

18

Search for Dark Matter in Mono-Jet Topology at ATLAS · +Dark Matter at colliders 3 Maria Giulia...

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