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Search for new phenomena in dijet events with the ATLAS detector at - - PowerPoint PPT Presentation

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Search for new phenomena in dijet events with the ATLAS detector at s = 13 TeV Dengfeng Zhang(Tsinghua University) ILHC-ICTP2019, ICTP May 27-31, 2019 Outline Introduction to Dijet Analysis Dijet Resonance Analysis Dijet Angular

slide-1
SLIDE 1

Search for new phenomena in dijet events with the ATLAS detector at √s = 13 TeV

Dengfeng Zhang(Tsinghua University) ILHC-ICTP2019, ICTP May 27-31, 2019

slide-2
SLIDE 2

Outline

  • Introduction to Dijet Analysis
  • Dijet Resonance Analysis
  • Dijet Angular Analysis
  • Summary

2 May 29, 2019 ILHC-ICTP2019@ICTP

slide-3
SLIDE 3

Introduction

  • pp collisions at √s = 13 TeV, providing a wide scope to search

for new phenomena at ATLAS;

  • Final states including partons dominate in some BSM models;
  • Total dijet production rates for BSM signals can be large;
  • Two complementary analysis: resonance analysis based on mjj

and angular analysis base on πœ“.

3 May 29, 2019 ILHC-ICTP2019@ICTP

Ο‡ = e2|y*|, y* = (y1 βˆ’ y2) / 2

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SLIDE 4

Dijet Event Display

4 May 29, 2019 ILHC-ICTP2019@ICTP

Recorded highest mass dijet event: leading/sub-leading jet pT=3.74 TeV, |y*|=0.38, mjj=8.02 TeV.

slide-5
SLIDE 5

Resonance Analysis

slide-6
SLIDE 6

Overview of Resonance Analysis

6 May 29, 2019 ILHC-ICTP2019@ICTP

  • In SM, hadron collisions produce jet pairs primarily via 2 β†’ 2

parton scattering processes governed by QCD;

  • QCD predicts a smoothly falling dijet invariant mass

distribution;

  • New particles decaying to two jets may introduce local excesses.
  • Sensitive to resonant signals.
  • Benchmark Model: q*, ZΚΉ, WΚΉ, W*, QBH, etc.
  • Three presented results: 15.7 fb-1, 37 fb-1 and 139 fb-1 in Run 2.
slide-7
SLIDE 7

Event Selection and Background Estimation: 15.7 fb-1

7 May 29, 2019 ILHC-ICTP2019@ICTP

Global fitting with 3-parameters function on the mjj spectrum to estimate the background directly:

Event Selection:

  • GRL
  • LAr, Tile, SCT error rejected
  • Core: Incomplete event rejected
  • PV has at least two tracks
  • Pass HLT_j380
  • β‰₯2 clean jets, Leading jet pT > 440 GeV Sub-

leading jet pT>60GeV

  • |y*| = |y1-y2|/2 < 0.6(1.2 for W*)
  • mjj > 1100 GeV(1717 GeV for W*)

Events

1 10

2

10

3

10

4

10

5

10

6

10

[TeV]

jj

m

2 3 4 5 6 7

  • Rel. Uncert.

0.4 βˆ’ 0.2 βˆ’ 0.2 0.4

|y*| < 0.6 Fit Range: 1.1 - 7.1 TeV

  • value = 0.67

p Data Fit Statistical uncertainty on fit Function choice

  • 1

=13 TeV, 15.7 fb s

ATLAS Preliminary

f(x) = p1(1 βˆ’ x)p2xp3

x = mjj/ s

ATLAS-CONF-2016-069

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SLIDE 8

SearchPhase Results: 15.7 fb-1

8 May 29, 2019 ILHC-ICTP2019@ICTP

Events

1 10

2

10

3

10

4

10

5

10

6

10

|y*| < 0.6 Fit Range: 1.1 - 7.1 TeV
  • value = 0.67
p 3 Γ— Οƒ *, q

[TeV]

jj

m

2 3 4 5 6 7 8

Significance

2 βˆ’ 2

ATLAS Preliminary

  • 1

=13 TeV, 15.7 fb s

Data Background fit BumpHunter interval = 4.0 TeV

* q

*, m q = 5.0 TeV

* q

*, m q

Events

1 10

2

10

3

10

4

10

5

10

6

10

|y*| < 1.2 Fit Range: 1.7 - 7.6 TeV
  • value = 0.83
p 30 Γ— Οƒ )=0), x Ο† W*(sin(

[TeV]

jj

m

2 3 4 5 6 7 8

Significance

2 βˆ’ 2

ATLAS Preliminary

  • 1

=13 TeV, 15.7 fb s Data Background fit BumpHunter interval = 2.8 TeV

W*

)=0), m

x

Ο† W*(sin( = 3.8 TeV

W*

)=0), m

x

Ο† W*(sin(

ATLAS-CONF-2016-069 p-value: 0.67 p-value: 0.83

  • BumpHunter Algorithm is employed to search for local excess
  • ver the background.
  • No significant local excess.
slide-9
SLIDE 9

Limit Setting: 15.7 fb-1

9 May 29, 2019 ILHC-ICTP2019@ICTP

Bayesian method to set upper limits at 95% C.L. on Acceptance*Xs*Br.

[TeV]

W*

M 2 2.5 3 3.5 4 BR [pb] Γ— A Γ— Οƒ

2 βˆ’

10

1 βˆ’

10 1

ATLAS Preliminary

)=0)

x

Ο† W*(sin( Observed 95% CL upper limit Expected 95% CL upper limit 68% and 95% bands

  • 1

=13 TeV, 15.7 fb s |y*| < 1.2

[TeV]

* q

M 2 4 6 BR [pb] Γ— A Γ— Οƒ

4 βˆ’

10

3 βˆ’

10

2 βˆ’

10

1 βˆ’

10 1

ATLAS Preliminary

* q Observed 95% CL upper limit Expected 95% CL upper limit 68% and 95% bands

  • 1

=13 TeV, 15.7 fb s |y*| < 0.6

ATLAS-CONF-2016-069

Model 95% CL exclusion limit Observed Expected 2012@8 TeV Observed Expected Quantum Black Hole 8.7 TeV 8.7 TeV 5.66 TeV 5.66 TeV Excited quark 5.6 TeV 5.5 TeV 4.06 TeV 3.98 TeV Wβ€² 2.9 TeV 3.3 TeV 2.45 TeV 2.51 TeV Wβˆ— 3.3 TeV 3.3 TeV 1.75 TeV 1.95 TeV

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SLIDE 10

Event Selection and Background Estimation: 37 fb-1

10 May 29, 2019 ILHC-ICTP2019@ICTP

Events / Bin

1 βˆ’

10 1 10

2

10

3

10

4

10

5

10

6

10

7

10

[TeV]

jj

m

2 3 4 5 6 7 8 9

  • Rel. Uncert.

0.4 βˆ’ 0.2 βˆ’ 0.2 0.4

|y*| < 0.6 Fit Range: 1.1 - 8.2 TeV Data Fit Statistical uncertainty in fit Function choice

  • 1

=13 TeV, 37.0 fb s

ATLAS

Same with last publication.

  • Phys. Rev. D 96 (2017) 052004

Sliding Window Fitting Method(SWiFt):

  • Slide over mass spectrum into smaller windows;
  • Perform fitting in each window;
  • Stitch background fit value in each bin together for

the full range prediction.

Event Selection:

  • GRL
  • LAr, Tile, SCT error rejected
  • Core: Incomplete event rejected
  • PV has at least two tracks
  • Pass HLT_j380
  • β‰₯2 clean jets, Leading jet pT > 440 GeV Sub-leading

jet pT>60GeV

  • |y*| = |y1-y2|/2 < 0.6(1.2 for W*)
  • mjj > 1100 GeV(1717 GeV for W*)

f(x) = p1(1 βˆ’ x)p2xp3, x = mjj/ s

slide-11
SLIDE 11

SearchPhase Results: 37 fb-1

11 May 29, 2019 ILHC-ICTP2019@ICTP

  • BumpHunter Algorithm is employed to search for local excess
  • ver the background.
  • No significant local excess.

Events / Bin

1 βˆ’ 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 |y*| < 0.6 Fit Range: 1.1 - 8.2 TeV
  • value = 0.63
p 10 Γ— Οƒ *, q Significance 2 βˆ’ 2

[TeV]

jj

m

2 3 4 5 6 7 8 9

MC Data-MC 0.5 βˆ’ 0.5 JES Uncertainty

ATLAS

  • 1
=13 TeV, 37.0 fb s Data Background fit BumpHunter interval = 4.0 TeV * q *, m q = 5.0 TeV * q *, m q

Events / Bin

1 βˆ’ 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 |y*| < 1.2 Fit Range: 1.7 - 8.1 TeV
  • value = 0.83
p 100 Γ— Οƒ )=0), x Ο† W*(sin( Significance 2 βˆ’ 2

[TeV]

jj

m

2 3 4 5 6 7 8

MC Data-MC 0.5 βˆ’ 0.5 JES Uncertainty

ATLAS

  • 1
=13 TeV, 37.0 fb s Data Background fit BumpHunter interval = 2.8 TeV W* )=0), m x Ο† W*(sin( = 3.8 TeV W* )=0), m x Ο† W*(sin(
  • Phys. Rev. D 96 (2017) 052004

p-value: 0.63 p-value: 0.83

slide-12
SLIDE 12

SearchPhase Results: 37 fb-1

12 May 29, 2019 ILHC-ICTP2019@ICTP

[TeV]

W*

m 2 3 4 5 BR [pb] Γ— A Γ— Οƒ

3 βˆ’

10

2 βˆ’

10

1 βˆ’

10 1

ATLAS

)=0)

x

Ο† W*(sin( Observed 95% CL upper limit Expected 95% CL upper limit Οƒ 2 Β± and Οƒ 1 Β± Expected

  • 1

=13 TeV, 37.0 fb s |y*| < 1.2

[TeV]

* q

m 2 4 6 BR [pb] Γ— A Γ— Οƒ

4 βˆ’

10

3 βˆ’

10

2 βˆ’

10

1 βˆ’

10 1

ATLAS

* q Observed 95% CL upper limit Expected 95% CL upper limit Οƒ 2 Β± and Οƒ 1 Β± Expected

  • 1

=13 TeV, 37.0 fb s |y*| < 0.6

Bayesian method to set upper limits at 95% C.L. on Acceptance*Xs*Br.

  • Phys. Rev. D 96 (2017) 052004

Model 95% CL exclusion limit Observed Expected 2016 Observed Expected Quantum Black Hole 8.9 TeV 8.9 TeV 8.7 TeV 8.7 TeV Excited quark 6.0 TeV 5.8 TeV 5.6 TeV 5.5 TeV Wβ€² 3.6 TeV 3.7 TeV 2.9 TeV 3.3 TeV Wβˆ— 3.4 TeV 3.6 TeV 3.3 TeV 3.3 TeV

slide-13
SLIDE 13

Latest Resonance Analysis: 139 fb-1

13 May 29, 2019 ILHC-ICTP2019@ICTP Event Selection:

  • Good Run List (GRL)
  • LAr, Tile, SCT error rejected,
  • Core: Incomplete event rejected,
  • PV has at least two tracks,
  • Pass HLT_j420,
  • β‰₯2 clean jets, Leading jet pT > 420 GeV, Sub-

leading jet pT > 150 GeV,

  • |y*|=|y1-y2|/2<0.6
  • |mjj|>1100 GeV
  • Sliding Window Fitting Method(SWiFt) is still robust:
  • BumpHunter Algorithm is used to search for local excess over the background.
  • No significant local excess.

2 4 6 8

1 βˆ’

10 1 10

2

10

3

10

4

10

5

10

6

10

7

10

8

10

Events

|y*| < 0.6 Fit Range: 1.1 - 8.1 TeV
  • value = 0.8
p 0.1 Γ— Οƒ *, q

2 3 4 5 6 7 8

[TeV]

jj

m

2 βˆ’ 2

Significance

ATLAS Preliminary

  • 1

=13 TeV, 139 fb s Data Background fit BumpHunter interval = 4.0 TeV

* q

*, m q = 5.0 TeV

* q

*, m q

p-value: 0.8

Full Run2 Data

f(x) = p1(1 βˆ’ x)p2xp3+p4lnx, x = mjj/ s

ATLAS-CONF-2019-007

slide-14
SLIDE 14

Latest Resonance Analysis: 139 fb-1

14 May 29, 2019 ILHC-ICTP2019@ICTP

More results of other channels and Dib-jet analysis are coming soon for

  • ne paper.

[TeV]

q*

m 2 3 4 5 6 7 8 BR [pb] Γ— A Γ— Οƒ

4 βˆ’

10

3 βˆ’

10

2 βˆ’

10

1 βˆ’

10 1

Theory Observed 95% CL Expected 95% CL Οƒ 1 Β± Οƒ 2 Β±

ATLAS Preliminary

  • 1

= 13 TeV, 139 fb s

ATLAS-CONF-2019-007 Mq*<6.7 TeV

  • CLs technique implemented in HistFitter framework to set upper

limits at C.L. of 95%.

slide-15
SLIDE 15

Angular Analysis

slide-16
SLIDE 16

Overview of Angular Analysis

16 May 29, 2019 ILHC-ICTP2019@ICTP

  • In SM, t-channel dominates the parton scattering process, most

dijet productions occur at small angles, differential cross section tends to be flat;

  • BSM predicts additional dijet production at large angles.

Ο‡ = e2|y*|, y* = (y1 βˆ’ y2) / 2 y = 1 2 ln( E + pz E βˆ’ pz )

  • Sensitive to resonant/non-resonant signals;
  • Benchmark Models: CI, QBH, etc.
  • Two published results: 15.7 fb-1, 37 fb-1.
slide-17
SLIDE 17

Event Selection and Background Estimation

17 May 29, 2019 ILHC-ICTP2019@ICTP

Event Selection:

  • GRL
  • Quality cuts
  • HLT_j380
  • β‰₯2 clean jets, Leading jet pT

> 440 GeV Sub-leading jet pT>60GeV

  • |y*| = |y1-y2|/2 < 1.7
  • |yB| = |y1+y2|/2 < 1.1
  • mjj > 2500 GeV

Background Estimation:

  • QCD background modeled from MC

simulation,

  • EW corrections applied as a function of

(mjj ,Ο‡),

  • QCD NLO corrections applied as a

function of (mjj ,Ο‡),

  • Normalize QCD background to data.

Same in two released analysis: 15.7 fb-1 and 37 fb-1

slide-18
SLIDE 18

Angular Analysis Results: 15.7 fb-1

18 May 29, 2019 ILHC-ICTP2019@ICTP ATLAS-CONF-2016-069 CLb p value: 0.07

Model 95% CL exclusion limit Observed Expected Contact interactions (Ξ·LL =+1) 12.6 TeV 13.7 TeV Contact interactions (Ξ·LL =-1) 19.9 TeV 23.7 TeV

slide-19
SLIDE 19

Angular Analysis Results: 37 fb-1

19 May 29, 2019 ILHC-ICTP2019@ICTP

Ο‡ 1 2 3 4 5 6 7 10 20 30 < 3.7 TeV jj 3.4 < m Ο‡ 1 2 3 4 5 6 7 10 20 30 0.03 0.04 0.05 < 4.0 TeV jj 3.7 < m < 4.3 TeV jj 4.0 < m 0.03 0.04 0.05 < 4.6 TeV jj 4.3 < m < 4.9 TeV jj 4.6 < m 0.04 0.06 < 5.4 TeV jj 4.9 < m Data SM =22 TeV Ξ› 1, βˆ’ = LL Ξ· CI =15 TeV Ξ› 1, + = LL Ξ· CI Theoretical uncert. Total uncertainty

Ο‡ 1/N dN/d

0.04 0.06 > 5.4 TeV jj m

ATLAS

  • 1

=13 TeV, 37.0 fb s

[TeV] Ξ›

16 18 20 22 24 26 28 30 th

Οƒ / Οƒ

1 βˆ’

10 1

ATLAS 1 βˆ’ = LL Ξ· ;
  • 1
= 13 TeV, 37.0 fb s Observed 95% CL upper limit Expected 95% CL upper limit Οƒ 2 Β± and Οƒ 1 Β± Expected

[TeV] Ξ›

10 15 20 25 30 th

Οƒ / Οƒ

1 βˆ’

10 1

ATLAS 1 + = LL Ξ· ;
  • 1
= 13 TeV, 37.0 fb s Observed 95% CL upper limit Expected 95% CL upper limit Οƒ 2 Β± and Οƒ 1 Β± Expected
  • Phys. Rev. D 96 (2017) 052004

CLb p value: 0.06

Model 95% CL exclusion limit Observed Expected Contact interactions (Ξ·LL =+1) 13.1 TeV 15.0 TeV 17.4-29.5 TeV Contact interactions (Ξ·LL =-1) 21.8 TeV 28.3 TeV

slide-20
SLIDE 20

Summary

  • Performed new physics search in dijet events in resonance and

angular analysis using the full Run2 data collected by ATLAS;

  • No significant deviation from the background is observed;
  • Improved upper limits set on several benchmark models;
  • In Dijet Resonance Analysis, results of other channels and Dib-jet

analysis are coming soon for one paper.

20 May 29, 2019 ILHC-ICTP2019@ICTP

Thanks

slide-21
SLIDE 21

Backup

slide-22
SLIDE 22

SearchPhase Results

22 May 29, 2019 ILHC-ICTP2019@ICTP

Events / Bin 1 βˆ’ 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 |y*| < 0.6 Fit Range: 1.1 - 8.2 TeV
  • value = 0.63
p 10 Γ— Οƒ *, q Significance 2 βˆ’ 2 [TeV] jj m 2 3 4 5 6 7 8 9 MC Data-MC 0.5 βˆ’ 0.5 JES Uncertainty ATLAS
  • 1
=13 TeV, 37.0 fb s Data Background fit BumpHunter interval = 4.0 TeV * q *, m q = 5.0 TeV * q *, m q Events / Bin 1 βˆ’ 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 |y*| < 1.2 Fit Range: 1.7 - 8.1 TeV
  • value = 0.83
p 100 Γ— Οƒ )=0), x Ο† W*(sin( Significance 2 βˆ’ 2 [TeV] jj m 2 3 4 5 6 7 8 MC Data-MC 0.5 βˆ’ 0.5 JES Uncertainty ATLAS
  • 1
=13 TeV, 37.0 fb s Data Background fit BumpHunter interval = 2.8 TeV W* )=0), m x Ο† W*(sin( = 3.8 TeV W* )=0), m x Ο† W*(sin(

Events / Bin

1 βˆ’ 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 |y*| < 0.6 Fit Range: 1.1 - 8.2 TeV
  • value = 0.63
p QBH

[TeV]

jj

m

2 3 4 5 6 7 8 9

Significance 2 βˆ’ 2 ATLAS
  • 1
=13 TeV, 37.0 fb s Data Background fit BumpHunter interval = 5.0 TeV th QBH, m = 6.5 TeV th QBH, m

Events / Bin

1 βˆ’ 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 |y*| < 0.6 Fit Range: 1.1 - 8.2 TeV
  • value = 0.63
p 100 Γ— Οƒ W',

[TeV]

jj

m

2 3 4 5 6 7 8 9

Significance 2 βˆ’ 2 ATLAS
  • 1
=13 TeV, 37.0 fb s Data Background fit BumpHunter interval = 1.5 TeV W' W', m = 2.0 TeV W' W', m
  • Phys. Rev. D 96 (2017) 052004
slide-23
SLIDE 23

Upper limits on q*,W’,QBH and W*

23 May 29, 2019 ILHC-ICTP2019@ICTP

[TeV]

* q

m 2 4 6 BR [pb] Γ— A Γ— Οƒ

4 βˆ’

10

3 βˆ’

10

2 βˆ’

10

1 βˆ’

10 1

ATLAS

* q Observed 95% CL upper limit Expected 95% CL upper limit Οƒ 2 Β± and Οƒ 1 Β± Expected

  • 1

=13 TeV, 37.0 fb s |y*| < 0.6

[TeV]

th

M 4 6 8 10 [pb] A Γ— Οƒ

5 βˆ’

10

4 βˆ’

10

3 βˆ’

10

2 βˆ’

10

1 βˆ’

10

ATLAS

QBH Observed 95% CL upper limit Expected 95% CL upper limit Οƒ 2 Β± and Οƒ 1 Β± Expected

  • 1

=13 TeV, 37.0 fb s |y*| < 0.6

[TeV]

W'

m 2 4 6 BR [pb] Γ— A Γ— Οƒ

4 βˆ’

10

3 βˆ’

10

2 βˆ’

10

1 βˆ’

10 1

ATLAS

W' Observed 95% CL upper limit Expected 95% CL upper limit Οƒ 2 Β± and Οƒ 1 Β± Expected

  • 1

=13 TeV, 37.0 fb s |y*| < 0.6

[TeV]

W*

m 2 3 4 5 BR [pb] Γ— A Γ— Οƒ

3 βˆ’

10

2 βˆ’

10

1 βˆ’

10 1

ATLAS

)=0)

x

Ο† W*(sin( Observed 95% CL upper limit Expected 95% CL upper limit Οƒ 2 Β± and Οƒ 1 Β± Expected

  • 1

=13 TeV, 37.0 fb s |y*| < 1.2

  • Phys. Rev. D 96 (2017) 052004
slide-24
SLIDE 24

Upper limits on Zβ€²

24 May 29, 2019 ILHC-ICTP2019@ICTP

[TeV]

Z’

m 1.5 2 2.5 3 3.5

q

g 0.05 0.1 0.15 0.2 0.25 0.3

  • 1

= 13 TeV, 37.0 fb s ATLAS

Observed 95% CL upper limit Expected 95% CL upper limit

[TeV]

Z’

m 1.5 2 2.5 3 3.5

q

g 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45

  • 1

= 13 TeV; 15.7 fb s Preliminary ATLAS

  • bs. limit
  • exp. limit
  • Phys. Rev. D 96 (2017) 052004

ATLAS-CONF-2016-069

The 95% CL exclusion limits for the Zβ€² model described in the text, as a function of the coupling to quarks, gq, and the mass, mZβ€², obtained from the dijet invariant mass mjj

  • distribution. For a given mass, the cross-sections rise with gq, and thus the upper left unfilled

area is excluded, as indicated by the direction of the hatched band. The exclusion applies up to gq=0.5, in the sensitivity range of the method as explained in the text. Points were simulated with 0.5 TeV spacing in mass and spacing as fine as 0.05 in gq, A smooth curve is drawn between points by interpolating in gq followed by an interpolation in mZβ€².

slide-25
SLIDE 25

Upper limits on Gaussian signals

25 May 29, 2019 ILHC-ICTP2019@ICTP The 95% CL upper limits obtained from the dijet invariant mass mjjjj distribution on cross- section times acceptance times branching ratio to two jets, σ×AΓ—BR, for a hypothetical signal with a cross-section ΟƒG that produces a Gaussian contribution to the particle-level mjj distribution, as a function of the mean of the Gaussian mass distribution mjj. Observed limits are obtained for different widths, from a narrow width to 15% of mjj. The expected limit and the corresponding Β± 1Οƒ and Β± 2Οƒ bands are also indicated for a narrow-width resonance.

[TeV]

G

m 2 4 6 BR [pb] Γ— A Γ— Οƒ

4 βˆ’

10

3 βˆ’

10

2 βˆ’

10

1 βˆ’

10 1

ATLAS

  • 1

=13 TeV, 37.0 fb s |y*| < 0.6

= 0

G

/m

G

Οƒ

  • Exp. 95% CL upper limit for

Οƒ 2 Β± and Οƒ 1 Β± Expected

  • Obs. 95% CL upper limit for:

= 0.15

G

/m

G

Οƒ = 0.10

G

/m

G

Οƒ = 0.07

G

/m

G

Οƒ = 0.03

G

/m

G

Οƒ = 0

G

/m

G

Οƒ

[TeV]

G

m 2 4 6 BR [pb] Γ— A Γ— Οƒ

4 βˆ’

10

3 βˆ’

10

2 βˆ’

10

1 βˆ’

10 1

ATLAS Preliminary

  • 1

=13 TeV, 15.7 fb s |y*| < 0.6 = 0.15

G

/m

G

Οƒ = 0.10

G

/m

G

Οƒ = 0.07

G

/m

G

Οƒ = Res.

G

/m

G

Οƒ

  • Phys. Rev. D 96 (2017) 052004

ATLAS-CONF-2016-069

slide-26
SLIDE 26

Upper limits on Gaussian signals

26 May 29, 2019 ILHC-ICTP2019@ICTP The 95% CL upper limits obtained from the dijet invariant mass mjjjj distribution on cross- section times acceptance times branching ratio to two jets, σ×AΓ—BR, for a hypothetical signal with a cross-section ΟƒG that produces a Gaussian contribution to the particle-level mjj distribution, as a function of the mean of the Gaussian mass distribution mjj. Observed limits are obtained for different widths, from a narrow width to 15% of mjj. The expected limit and the corresponding Β± 1Οƒ and Β± 2Οƒ bands are also indicated for a narrow-width resonance.

[TeV]

G

m 2 4 6 BR [pb] Γ— A Γ— Οƒ

4 βˆ’

10

3 βˆ’

10

2 βˆ’

10

1 βˆ’

10 1

ATLAS

  • 1

=13 TeV, 37.0 fb s |y*| < 0.6

= 0

G

/m

G

Οƒ

  • Exp. 95% CL upper limit for

Οƒ 2 Β± and Οƒ 1 Β± Expected

  • Obs. 95% CL upper limit for:

= 0.15

G

/m

G

Οƒ = 0.10

G

/m

G

Οƒ = 0.07

G

/m

G

Οƒ = 0.03

G

/m

G

Οƒ = 0

G

/m

G

Οƒ

[TeV]

G

m 2 4 6 BR [pb] Γ— A Γ— Οƒ

4 βˆ’

10

3 βˆ’

10

2 βˆ’

10

1 βˆ’

10 1

ATLAS Preliminary

  • 1

=13 TeV, 15.7 fb s |y*| < 0.6 = 0.15

G

/m

G

Οƒ = 0.10

G

/m

G

Οƒ = 0.07

G

/m

G

Οƒ = Res.

G

/m

G

Οƒ

  • Phys. Rev. D 96 (2017) 052004

ATLAS-CONF-2016-069

slide-27
SLIDE 27

Upper limits on Gaussian signals

27 May 29, 2019 ILHC-ICTP2019@ICTP The 95% CL upper limits obtained from the dijet invariant mass mjjjj distribution on cross- section times acceptance times branching ratio to two jets, σ×AΓ—BR, for a hypothetical signal with a cross-section ΟƒG that produces a Gaussian contribution to the particle-level mjj distribution, as a function of the mean of the Gaussian mass distribution mjj. Observed limits are obtained for different widths, from a narrow width to 15% of mjj. The expected limit and the corresponding Β± 1Οƒ and Β± 2Οƒ bands are also indicated for a narrow-width resonance.

[TeV]

G

m 2 3 4 5 6 7 BR [pb] Γ— A Γ— Οƒ

4 βˆ’

10

3 βˆ’

10

2 βˆ’

10

1 βˆ’

10 1

= 3% G / m G Οƒ = 5% G / m G Οƒ = 7% G / m G Οƒ = 10% G / m G Οƒ = 15% G / m G Οƒ = 3% G / m G Οƒ
  • Exp. 95% CL upper limit for
  • Obs. 95% CL upper limit for:

ATLAS Preliminary

  • 1

= 13 TeV, 139 fb s

ATLAS-CONF-2019-007