opening up jets and missing energy searches · if the amount of energy released is comparable to...

Opening Up Jets and Missing Energy Searches

December 20, 2007

Jay WackerSLAC

Work in progress withJ. Alwall, M-P. Le, M. Lisanti

IPMU LHC Focus Week

(at the Tevatron)

1

Outline

Introduction

Generalized Gluinos

Matching

Backgrounds

Projected Reach

Outlook

2

High Energy FrontierNo “sure thing” theory to discover

Many BSM possibilities to search forSupersymmetric Standard Model

Universal Extra DimensionsRandall-Sundrum

Little Higgs

Different TeV scale physics, but similar signalsInverse problem hard

Discovery first

Tevatron, Flavor, Precision EW, HiggsLHC may not burst into a superfire

3

Jets plus Missing EnergyA common signature

New Colored Particle Decays to WIMP

Existing searches based upon MSSM

q̃q̃ q̃g̃g̃g̃

Very general template to start from

Can find SSM, UED, RS/LH w/ T-parity

4

1j + ET! 2j + ET! 3j + ET! 4j + ET!ET j1 " 150 " 35 " 35 " 35ET j2 < 35 " 35 " 35 " 35ET j3 < 35 < 35 " 35 " 35ET j4 < 20 < 20 < 20 " 20ET! " 150 " 225 " 150 " 100HT " 150 " 300 " 400 " 300

Table 1: Summary of the cuts used by DO!

object that can cascade into Standard Model particles plus some particles that are di!cultto produce. This prospect leads to a great simplifying assumption at the Tevatron – thereis a the lightest colored particle that can be produced that will subsequently decay into jetsplus a missing singlet. We demonstrate here that there is little reason to include any otherparameters other than the masses of the particles and the production cross section.

The relative masses of the gluino and the bino are the most important quantities toparameterize in the searches for the gluino. The mass of the gluino sets the production crosssection, but also sets the maximum amount of energy that can be released in the decay. Thegluino mass minus the bino mass sets the amount of energy that is released in the decay.If the amount of energy released is comparable to the gluino mass the energy is dividedroughly evenly between the two jets and the bino. This gives rise to the signal of four hardjets plus missing energy. As the mass of the bino increases not only do the jets soften, butthe amount of momentum transferred to the bino decreases.

Spint-chanel squarksCascade decays

3 Gluino Searches

Multijet searches

Selection criteriaCutsComparison between MC + PGS and analyses

Monojets searches


3

Gg q̃q̃ q̃g̃ g̃g̃

Jets + Missing Energy Cuts at D0

HT =!

ET j(Not exclusive searches)

Will these discover anything visible in these channels?

1fb-1 analysis

5

Gluino Mass (GeV)

0 100 200 300 400 500 600

Sq

ua

rk M

as

s (

Ge

V)

0

100

200

300

400

500

600

-1DØ Preliminary, 0.96 fb

<0µ=0, 0

=3, A!tanU

A1

UA

2

LEP

CD

F IB

DØ

IA

DØ IB

no mSUGRA

solution

CD

F II Slepton & Chargino

limits

What we know about gluino limits

6

mSugra is not representative of the MSSM

Never varies decay kinematics

mg̃ : mB̃ = 6 : 1

Are there visible signals that are not being analyzed?Possible because the background is challenging

Mirage MediationAnomaly Mediation

non-Minimal Gauge Mediation

7

Outline

Introduction

Generalized Gluinos

Matching

Backgrounds

Projected Reach

Outlook

8

Examining g̃g̃ more carefully

The “gluino” module

Turn on one decay mode g̃ ! qq̄!̃0

Keep masses and total cross section freemg̃ m!̃ !(pp̄! g̃g̃X)

Captures many models (MSSM, UED, etc)

Misses heavy flavor and cascades

9

Where has the Tevatron probed “gluinos”?

mg̃

mSugra

Q = 0

m!̃Q = m!̃m g̃

=m !̃

Q = mg̃ !mB̃ > mB̃

10

Two Kinematic Limits

“Normal” Widely Spaced Statesmg̃ ! m!̃

Same multijet searches over the past 20+ years

No cascades, or t-channel squarks

Easy to simulate

11

Degenerate Searchj3

j2g̃

j1

j4

g̃B̃B̃

ET!

Useful when not phase space limited Q = mg̃ !mB̃ > mB̃

Bino carries away energy but not momentum

As gluinos get boosted, jets become collinear and aligned with jetsET! !"j ET! ! 1

!g̃

If Q < mB̃

12

P j1T > 150 GeV

CD

F

P j2T < 60 GeV

P j3T < 20 GeV

ET! > 120 GeV

!"j2ET! > 0.3

g̃

g̃

j1j2

j3

ET!

B̃

B̃

Producing Degenerate Gluinos

Need additional hard jetsWant the spectrum as well

13

P j1T > 150 GeV ET! > 150 GeV

P j2T < 50 GeV !"jET! > 30"D

0g̃

g̃

j1j2

j3

ET!

B̃

B̃

Producing Degenerate Gluinos

Need additional hard jetsWant the spectrum as well

13

Gluinos are produced copiously

106 Events 103 Events 10 Events

14

Searches useful in gluino searches

n j + ET!

mg̃

mSugra

jISR + ET!

Q = 0

m!̃Q = m!̃m g̃

=m !̃

15

Transitions

ET j1

ET j2

35 GeV150 GeV

35 GeV

Fix mg̃ m!0Vary100 GeV 90 GeV! 0

1j + ET!2j + ET!

16

Transitions

ET j1

ET j2

35 GeV150 GeV

35 GeV


No ISR ISR

16

Transitions

ET j1

ET j2

35 GeV150 GeV

35 GeV


16

Transitions

150 GeV

ET!

HT

150 GeV 225 GeV

300 GeV


ET j1

ET j2

35 GeV150 GeV

35 GeV

Reduced efficiency as neutralino mass is decreased

17

Outline

Introduction

Generalized Gluinos

Matching

Backgrounds

Projected Reach

Outlook

18

Calculating Additional Jets

Parton Showering Matrix Elements

QCD Bremstrahlung Soft/Collinear Approximation

Necessary for well-separated jetsIncludes quantum interference

Fixed order calculationComputationally expensiveLimited number of partons

Resums large logsComputationally Cheap

Unlimited number of partons

Matching merges best of both worldsNecessary to avoid double counting

19

g̃!g̃! 2jg̃!g̃! 1jg̃!g̃! 0j

Calculating Additional Jets

g̃g̃ 0j g̃g̃ 1j g̃g̃ 2jMatrix Elements

Parto

n Sh

ower

Dec

ay

g̃g̃ 0j g̃g̃ 1j g̃g̃ 2j

20

0!Differential Jet Rate 1

0 50 100 150 200 25

pb/b

in

-310

-210

-110

1

10

Sum

+ 0-jet sampleg~

g~

+ 1-jet sampleg~

g~

+ 2-jet sampleg~

g~

Q-Cut

Transition from PS to ME

pT

21

1st Jet!DiJet Samples " Matched and UnMatched G150_ 40

50 100 150 200 250 300pT!GeV"

0

100

200

300

400

500

dehctaM

muN

stnevE

!1bf

!1"

50 100 150 200 250 300pT!GeV"

0

100

200

300

400

500

dehctamnU

muN

stnevE

!1bf

!1"

1st Jet!DiJet Samples " Matched and UnMatched G150_ 60

50 100 150 200 250 300pT!GeV"

0

100

200

300

400

500

dehctaM

muN

stnevE

!1bf

!1"

50 100 150 200 250 300pT!GeV"

0

100

200

300

400

500

dehctamnU

muN

stnevE

!1bf

!1"

500500

fb/1

0G

eV

g̃g̃0j

g̃g̃1j

mg̃ = 150 GeV m!̃ = 40 GeV

Effects of Matching on Signal

pT j1 pT j1

Matched Parton Shower Only

50 50250 250

mg̃ = 150 GeV m!̃ = 130 GeV20 8

g̃g̃1j

g̃g̃2j

fb/1

0G

eV

pT j1pT j150 50 250250

22

Outline

Introduction

Generalized Gluinos

Matching

Backgrounds

Projected Reach

Outlook

23

BackgroundsWant to vary cuts to maximize discovery potential

Generate SM events and compare to D0Madgraph Pythia PGS! !

24

BackgroundsWant to vary cuts to maximize discovery potential

Generate SM events and compare to D0

Three Dominant BackgroundsW/Z + jets

t tbar

QCD

Subdominant BackgroundsDiboson

Single top

Madgraph Pythia PGS! !

24

W/Z + jets BackgroundsHit Z+jets to within QCD K-factors

W+jets need a ~30% MET-independent scaling probably PGS efficiency at losing a lepton

25



Top BackgroundNeed MET-dependent K-factor

...until matching 2 additional jetstt̄ 2j ! (b!") (b̄!") 2j

25



Top BackgroundNeed MET-dependent K-factor

...until matching 2 additional jetstt̄ 2j ! (b!") (b̄!") 2j

QCD BackgroundNo attempt to simulate ET! > 100 GeV

25

(GeV)T

E

0 50 100 150 200 250 300 350 400 450 500

Even

ts / 2

0

1

10

210

310

410

0 50 100 150 200 250 300 350 400 450 500

1

10

210

310

410DØ Preliminary

Data + jets! l"W + jets!! "Z

ttWW,WZ,ZZ

+ jets-

l+

l"Zsingle-tSignal

,any jet) (degrees)TE(min#$

0 20 40 60 80 100 120 140 160 180

Even

ts / 5

0

50

100

150

200

250

300

0 20 40 60 80 100 120 140 160 1800

50

100

150

200

250

300

DØ Preliminary


ttWW,WZ,ZZ

+ jets-

l+

l"Zsingle-tSignal

(GeV)T

H0 100 200 300 400 500 600 700

Even

ts / 5

0

0

2

4

6

8

10

12

14

16

0 100 200 300 400 500 600 7000

2

4

6

8

10

12

14

16DØ Preliminary


ttWW,WZ,ZZ

+ jets-

l+

l"Zsingle-tSignal

(GeV)T

E

0 50 100 150 200 250 300 350 400 450 500

Even

ts / 2

0

-110

1

10

210

310

0 50 100 150 200 250 300 350 400 450 500

-110

1

10

210

310

DØ Preliminary


ttWW,WZ,ZZ

+ jets-

l+

l"Zsingle-tSignal

Before HT ET! cuts2 jet analysis

26

(GeV)T

E

0 50 100 150 200 250 300 350 400 450 500

Ev

en

ts /

20

1

10

210

310

410

0 50 100 150 200 250 300 350 400 450 500

1

10

210

310

410DØ Preliminary


ttWW,WZ,ZZ

+ jets-

l+

l"Zsingle-tSignal


0 20 40 60 80 100 120 140 160 180

Ev

en

ts /

5

0

50

100

150

200

250

300

0 20 40 60 80 100 120 140 160 1800

50

100

150

200

250

300

DØ Preliminary


ttWW,WZ,ZZ

+ jets-

l+

l"Zsingle-tSignal

(GeV)T

H0 100 200 300 400 500 600 700

Ev

en

ts /

50

0

2

4

6

8

10

12

14

16

0 100 200 300 400 500 600 7000

2

4

6

8

10

12

14

16DØ Preliminary


ttWW,WZ,ZZ

+ jets-

l+

l"Zsingle-tSignal

(GeV)T

E

0 50 100 150 200 250 300 350 400 450 500

Ev

en

ts /

20

-110

1

10

210

310

0 50 100 150 200 250 300 350 400 450 500

-110

1

10

210

310

DØ Preliminary


ttWW,WZ,ZZ

+ jets-

l+

l"Zsingle-tSignal

Before ET! cuts4 jet analysis

27

(GeV)T

E

0 50 100 150 200 250 300 350 400 450 500

Ev

en

ts /

20

1

10

210

310

410

0 50 100 150 200 250 300 350 400 450 500

1

10

210

310

410DØ Preliminary


ttWW,WZ,ZZ

+ jets-

l+

l"Zsingle-tSignal


0 20 40 60 80 100 120 140 160 180

Ev

en

ts /

5

0

50

100

150

200

250

300

0 20 40 60 80 100 120 140 160 1800

50

100

150

200

250

300

DØ Preliminary


ttWW,WZ,ZZ

+ jets-

l+

l"Zsingle-tSignal

(GeV)T

H0 100 200 300 400 500 600 700

Ev

en

ts /

50

0

2

4

6

8

10

12

14

16

0 100 200 300 400 500 600 7000

2

4

6

8

10

12

14

16DØ Preliminary


ttWW,WZ,ZZ

+ jets-

l+

l"Zsingle-tSignal

(GeV)T

E

0 50 100 150 200 250 300 350 400 450 500

Ev

en

ts /

20

-110

1

10

210

310

0 50 100 150 200 250 300 350 400 450 500

-110

1

10

210

310

DØ Preliminary


ttWW,WZ,ZZ

+ jets-

l+

l"Zsingle-tSignal

0 100 200 300 400Missing ET !GeV"

1.

10.

100.

1000.

Events#20

A quick comparison

But how much do we trust this? 30%??

Need to be aware of S/B for counting experiments

28

Outline

Introduction

Generalized Gluinos

Matching

Backgrounds

Projected Reach

Outlook

29

Exclusive Jets + MET Search

1j + ET! 2j + ET! 3j + ET! 4j + ET!ET j1 " 150 " 35 " 35 " 35ET j2 < 35 " 35 " 35 " 35ET j3 < 35 < 35 " 35 " 35ET j4 < 20 < 20 < 20 " 20ET! " 150 " 225 " 150 " 100HT " 150 " 300 " 400 " 300

Table 1: Summary of the cuts used by DO!

object that can cascade into Standard Model particles plus some particles that are di!cultto produce. This prospect leads to a great simplifying assumption at the Tevatron – thereis a the lightest colored particle that can be produced that will subsequently decay into jetsplus a missing singlet. We demonstrate here that there is little reason to include any otherparameters other than the masses of the particles and the production cross section.

The relative masses of the gluino and the bino are the most important quantities toparameterize in the searches for the gluino. The mass of the gluino sets the production crosssection, but also sets the maximum amount of energy that can be released in the decay. Thegluino mass minus the bino mass sets the amount of energy that is released in the decay.If the amount of energy released is comparable to the gluino mass the energy is dividedroughly evenly between the two jets and the bino. This gives rise to the signal of four hardjets plus missing energy. As the mass of the bino increases not only do the jets soften, butthe amount of momentum transferred to the bino decreases.

Spint-chanel squarksCascade decays

3 Gluino Searches

Multijet searches


Monojets searches


3

4 Separate Searches, Individually Optimized

Maximize significance for each mg̃,m!̃

30

4+Jets Search

HT

ET! ET! ET!

Standard Model 360, 60 360, 60 (mSugra)

Cascade decays turn missing energy to visible energy

Significantly degrade search

27/cell 7/cell 3/cell

31

ET cut! ET cut!

ET cut! ET cut!

HT

cut

HT

cut H

Tcu

tH

Tcu

tS/B

S/!

B

360,60 mSugra 360,60

> 1< 1

1!2!

5!

<1!

32

HT

ET! ET! ET!

360,120 360, 200Standard Model

At the Boundary of Visibility

20/cell 3/cell 3/cell

Accentuates the difference

33

1!2!

5!

<1!

ET cut! ET cut!

ET cut! ET cut!

HT

cut

HT

cut H

Tcu

tH

Tcu

tS/B

S/!

B

360,120 360, 200

<0.1

1

2

34

m!̃

mg̃

S/B>1

Multijet Searches

Harder cuts than D0

Looser cuts than D0m!̃

mg̃

S/B>0.1

35

The Degenerate Region

Monojet S/B>1

Dijet

m!̃

mg̃

m!̃

mg̃

S/B>1

Good in degenerate region

Fills in some gaps

36

Out[1377]=

100 200 300 400 5000

50

100

150

200

250

300

Gluino Mass !GeV"

Bino

Mass!GeV

"Final Exclusion plot for 2fb-1

m!̃

S/B>0.1

S/B>1

mg̃ Tighter cuts

Looser cuts

mSugra

37

Outline

Introduction

Generalized Gluinos

Matching

Backgrounds

Projected Reach

Outlook

38

Other modules

Have only focused on moduleg̃

q̃ q̃ ! q!

q̃ ! q!, g̃ ! qq̄!q̃g̃

g̃ g̃ ! qq̄!!,!! ! qq̄!

g̃ ! qq̄!!!,!!! ! qq̄!!,!! ! qq̄!g̃

3 parameters

4 parameters

5 parameters

7 parameters

...39

Should be a better way of searchingDon’t want to miss a visible signal

Jets plus MET Searches are effectively:Jet classification criterion

Visible Energy and Missing Energy Cuts

As parameters in a module vary, visible and missing energy change dramatically

40

d2!

dHT dET!!HT !ET!

One ProposalFor each jet multiplicity

Set a limit on

ET!

HT

<5fb

<10fb

<20fb

5+2!2fb

10+3!3fb

10+8!8fb

<2fb

<3fb

<5fb200

400

600

800

100 200 400300

e.g.4 jets

41

We are probing the Energy Frontier

Don’t know what we are looking for

Models are just motivation

We need more model-independent searches

Worst tragedy is to not discover a visible signal

42

opening up jets and missing energy searches · if the amount of energy released is comparable to...

Documents