Searches for physics beyond the Standard Model using dijet - - PowerPoint PPT Presentation

▶
searches for physics beyond the standard model using
SMART_READER_LITE
LIVE PREVIEW

Searches for physics beyond the Standard Model using dijet - - PowerPoint PPT Presentation

Mar 04, 2023 164 likes •539 views

Searches for physics beyond the Standard Model using dijet distributions in ATLAS Lene Bryngemark Lund University Uppsala, October 1 Analysis idea L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 2 / 30

slide-1
SLIDE 1

Searches for physics beyond the Standard Model using dijet distributions in ATLAS

Lene Bryngemark

Lund University

Uppsala, October 1

slide-2
SLIDE 2

Analysis idea

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 2 / 30

slide-3
SLIDE 3

Analysis idea

  • The LHC is at the energy frontier – even more so soon!
  • Would be a waste at this point in time to not make use of available energy
  • We don’t know what awaits us, so we want broad searches

Method: invariant mass and angular distributions of the hardest jet pair

(dijet), with moderate cuts.

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 2 / 30

slide-4
SLIDE 4

Why dijets?

  • Access to energy frontier
  • highest mass reach
  • smallest scales
  • Hadron collider: partons in – partons out

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 3 / 30

slide-5
SLIDE 5

But aren’t jets just too messy?

What is a jet? The output of a jet finding algorithm.

⇒ need to be defined such that they sensibly find something corresponding to a collimated spray of particles with partonic origin

Jets (or jet algorithms) are the bullies of the event! Don’t need to worry about

  • isolation
  • charge
  • fakes
  • vertex distance parameter

⇒ dijets are in fact a very clean topology!

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 4 / 30

slide-6
SLIDE 6

But is this really true??

Jets should be intrinsically sensitive to pile-up.

  • 10-20 simultaneous proton collisions in

2012 and 2015

  • signal from these events piles up in the

calorimeter read-out

  • contributes energy (positive or negative)

within the jet

  • distorts pT measurement (scale and

resolution)

  • distorts mass (and other single jet

structure) measurement(s)

  • contributes extra jets

⇒ pile-up is a potential hurdle; suddenly “isolation”, fakes and vertex reconstruction could start to matter!

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 5 / 30

slide-7
SLIDE 7

Solution: correct for pile-up

Imagine we could measure

  • how much pile-up there is in a given event
  • how susceptible each individual jet is to pile-up

Then we could correct for it!

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 6 / 30

slide-8
SLIDE 8

Solution: correct for pile-up

... and in fact we can:

[GeV] ρ 5 10 15 20 25 30 Normalised entries 0.02 0.04 0.06 0.08 0.1 0.12 0.14 = 6

PV

N = 10

PV

N = 14

PV

N = 18

PV

N ATLAS Simulation Preliminary < 21 〉 µ 〈 ≤ 20 = 8 TeV s Pythia Dijet LCW TopoClusters

The Anti-kt jet clustering algorithm, M. Cacciari, G. P. Salam, G. Soyez JHEP 0804 (2008) 063

  • measure the median pT density (ρ) in the event
  • this is dominated by low-pT “jets” as found by the kt algorithm
  • the area A is a measure of how much pile-up a jet will contain

⇒ subtract ρ × A from the jet pT. This is the jet-area based pile-up correction implemented in ATLAS and used in most analyses since 2012 data taking.

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 7 / 30

slide-9
SLIDE 9

Performance

〉 µ 〈 5 10 15 20 25 30 35 [GeV] 〉 ρ 〈 2 4 6 8 10 12 14 16 18

Powheg+Pythia8 MC Alpgen+Herwig MC Data Preliminary ATLAS + jets µ µ → Z LCW Topoclusters

| η | 0.5 1 1.5 2 2.5 3 3.5 4 [GeV]

PV

N ∂ /

T

p ∂

  • 0.4
  • 0.2

0.2 0.4 0.6 0.8 1

ATLAS Simulation Preliminary Pythia Dijets 2012 LCW R=0.4

t

anti-k Before any correction A subtraction × ρ After After residual correction

〉 µ 〈 5 10 15 20 25 30 35 40 ) [GeV]

true T

  • p

reco T

RMS(p 5 6 7 8 9 10 11 12 13

ATLAS Simulation Preliminary

=8 TeV s Pythia Dijet LCW R=0.6

t

anti-k < 30 GeV

true T

p ≤ 20 | < 2.4 η | uncorrected ) correction

PV

, N 〉 µ 〈 f( A correction × ρ

  • correction goes to 0 in limit of no pile-up
  • reduced dependence of jet pT on pile-up
  • removes some of the resolution smearing

introduced by pile-up

  • brings the number of pile-up jets down

5 10 15 20 25 30 35 40 > 20 GeV

T

, p 〉

jet

N 〈 2 2.5 3 3.5 4 4.5 5 5.5 6 〉 µ 〈 5 10 15 20 25 30 35 40 Data/MC 0.9 0.95 1 1.05 1.1

MC, No Correction Data, No Correction MC, Area Correction Data, Area Correction Preliminary ATLAS + jets µ µ → Z LCW R = 0.4

t

anti-k 2.1 ≤ | η | ≤ 0.0

After correction we can safely go back to using the bullying jets!

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 8 / 30

slide-10
SLIDE 10

Jets in ATLAS

Residual in-situ calibration EM or LCW constituent scale jets Residual pile-up correction Absolute EtaJES Origin Correction Global sequential calibration Jet area based pile- up correction

Function of µ and NPV
 applied to the jet at constituent scale Function of event pile-up energy density and jet area Jet finding applied to topological clusters at EM or LCW scale Changes the jet direction to point to the primary

  • vertex. Does not affect E.

Corrects the jet 4-vector to the particle level scale. Both the energy and direction are calibrated. Based on tracking and muon activity behind jets. Reduces flavour dependence and energy leakage effects. A final residual calibration is derived using in-situ measurements and is applied only to data

The other steps in the calibration chain:

  • bring the jets to “particle level” energy (Jet Energy Scale, JES)
  • ensure that different energy response in different detector regions is

compensated for

  • makes use of a number of in-situ techniques (using a reference
  • bject in data to restore pT balance)

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 9 / 30

slide-11
SLIDE 11

The dijet search

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 10 / 30

slide-12
SLIDE 12

Search strategy

Recall the method: invariant mass and angular distributions of the hardest

jet pair (dijet), with moderate cuts.

QCD is an overwhelming background! Make use of the knowledge:

QCD

  • No new scales above top mass

– smooth mass distributions

  • Incoming partons

predominantly undergo small-angle scattering (t-channel)

BSM

  • A new scale (particle mass,

interaction) – feature in the mass spectrum

  • New particle production or new

interaction predominantly isotropic (s-channel like)

  • Probe the scale: bin in dijet mass
  • Find the isotropic events: bin in jet rapidity difference

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 11 / 30

slide-13
SLIDE 13

yB = y1+y2

2

y∗ = y1−y2

2

χ = e2|y ∗|

  • Use lowest unprescaled single jet trigger

⇒ dictates leading jet pT > 410 GeV

  • Two or more anti-kt 0.4 jets

(pile-up dictates second jet pT > 50 GeV)

  • mjj cut for unbiased kinematics
  • The distribution in χ (or y ∗) is our isotropy measure
  • Rapidity is additive – measure in the dijet frame

more QCD-like more BSM-like

This talk refers to two searches:

Search for New Phenomena in the Dijet Angular Distributions in Proton-Proton Collisions at √s = 8 TeV with the ATLAS Detector,

  • Phys. Rev. Lett., 114:221802, 2015. arXiv link

Search for New Phenomena in Dijet Mass and Angular Distributions with the ATLAS Detector at √s = 13 TeV, ATLAS-CONF-2015-042, Aug 2015. CDS link L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 12 / 30

slide-14
SLIDE 14

Event selection

Angular distribution search:

At high mjj

  • |y∗| < 1.7
  • |yB| < 1.1
  • mjj > 2.5 TeV
  • Bin (coarsely) in mjj
  • Prediction for SM shape (lowest
  • rder: flat!) – relies on modelling
  • Deviation at low χ for some mjj ⇒

discovery (or else, limit setting) ⇒ sensitive to wide or non-resonant phenomena

Mass resonance search:

  • |y∗| < 0.6

(suppress QCD)

  • mjj > 1.1 TeV
  • Cut on y∗
  • Fit to smooth SM background – relies

“only” on good fit function choice

  • BumpHunt for most discrepant region

in mjj ⇒ discovery, or, limit setting ⇒ sensitive to narrow resonances (fit swallows other deviations)

Maximise discovery potential by exploiting this complementarity!

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 13 / 30

slide-15
SLIDE 15

The search: (angular) 8 and 13 TeV

Spring:

  • Used 17.3 fb−1 of 8 TeV data
  • Mature data set, collected since a long

time

  • Partial data set to validate search

Summer:

  • Used 80 pb−1 of 13 TeV data
  • The first approved ATLAS search
  • Lots of validation work on-the-fly

within the group

  • Analysis strategy, cuts etc already set

in stone before data taking started

Why this rush?

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 14 / 30

slide-16
SLIDE 16

The search: (angular) 8 and 13 TeV

Spring:

  • Used 17.3 fb−1 of 8 TeV data
  • Mature data set, collected since a long

time

  • Partial data set to validate search

Summer:

  • Used 80 pb−1 of 13 TeV data
  • The first approved ATLAS search
  • Lots of validation work on-the-fly

within the group

  • Analysis strategy, cuts etc already set

in stone before data taking started

W.J. Stirling, private communication

100 1000 1 10 100

gg Σqq qg

WJS2013

ratios of LHC parton luminosities: 13 TeV / 8 TeV

luminosity ratio MX (GeV)

MSTW2008NLO

_

Discovery potential!

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 14 / 30

slide-17
SLIDE 17

SM prediction: mass spectrum

The fit is an evolution of a semi-ad hoc function f (x) = p1(1 − x)p2xp3+p4 log(x)+p5 log(x)2, where x = mjj/√s

Historically, as mass reach/luminosity has increased, more parameters added 8 TeV mass search: realised after unblinding that five parameters were needed This time around, we have

Prescale-weighted events

1 10

2

10

3

10

4

10

5

10

6

10

7

10

8

10

9

10 [data-fit]/fit

  • 1

1

[TeV]

jj

Reconstructed m

0.3 0.4 0.5 1 2 3 4 5

Signif.

  • 2

2

ATLAS

  • 1

L dt=20.3 fb

∫

=8 TeV, s Data Fit *, m = 0.6 TeV q *, m = 2.0 TeV q *, m = 3.5 TeV q

  • narrower mass region
  • smaller luminosity
  • but still no ways to change strategies after looking at data!

Solution: start with 3 parameters, use a pre-defined figure of merit for when to add more

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 15 / 30

slide-18
SLIDE 18

SM prediction: angular distribution

Use Pythia8, which gives a leading order prediction Normalise it to the data integral – this is a shape comparison!

  • NLO: QCD K-factors derived using NLOjet++
  • EW corrections from Dittmaier et. al

Dominant theory uncertainties: renormalisation and factorisation scale uncertainty PDF uncertainty largely vanishes in the normalisation! Dominant experimental uncertainty: JES

χ 1 2 3 4 5 6 7 8 10 20 30 χ 1/N dN/d 0.025 0.03 0.035 0.04 0.045

  • 1

= 8 TeV, 17.3 fb s

ATLAS > 3.2 TeV

jj

m Total uncertainties SM JES Scale Tune Generator Shower k-factor PDF

Uncertainty breakdown, 8 TeV angular search L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 16 / 30

slide-19
SLIDE 19

The 8 TeV lesson

χ

1 2 3 4 5 6 7 8 10 20 30 0.03 0.04 < 0.8 TeV

jj

0.6 < m

0.03 0.04

< 1.2 TeV

jj

0.8 < m

0.03 0.04

< 1.6 TeV

jj

1.2 < m

0.03 0.04

< 2.0 TeV

jj

1.6 < m

0.03 0.04

< 2.6 TeV

jj

2.0 < m

0.03 0.04

< 3.2 TeV

jj

2.6 < m

χ 1/N dN/d

0.02 0.04 0.06

> 3.2 TeV

jj

m

Data SM prediction Theoretical uncert. SM, no EW correction = +1

LL

η = 8 TeV, Λ CI, = -1

LL

η = 12 TeV, Λ CI, Data SM prediction Theoretical uncert. SM, no EW correction = +1

LL

η = 8 TeV, Λ CI, = -1

LL

η = 12 TeV, Λ CI,

ATLAS

  • 1

= 8 TeV, 17.3 fb s

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 17 / 30

slide-20
SLIDE 20

The 8 TeV lesson: EW corrections

χ

1 2 3 4 5 6 7 8 10 20 30 0.03 0.04 < 0.8 TeV

jj

0.6 < m 0.03 0.04 < 1.2 TeV

jj

0.8 < m 0.03 0.04 < 1.6 TeV

jj

1.2 < m 0.03 0.04 < 2.0 TeV

jj

1.6 < m 0.03 0.04 < 2.6 TeV

jj

2.0 < m 0.03 0.04 < 3.2 TeV

jj

2.6 < m

χ 1/N dN/d

0.02 0.04 0.06 > 3.2 TeV

jj

m Data SM prediction Theoretical uncert. SM, no EW correction = +1

LL

η = 8 TeV, Λ CI, = -1

LL

η = 12 TeV, Λ CI, Data SM prediction Theoretical uncert. SM, no EW correction = +1

LL

η = 8 TeV, Λ CI, = -1

LL

η = 12 TeV, Λ CI,

ATLAS

  • 1

= 8 TeV, 17.3 fb s

Zoom in:

  • Significant improvement in data/MC

agreement with EW corrections

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 17 / 30

slide-21
SLIDE 21

EW corrections

  • Combination (cancellation) of tree-level

effects and loop corrections

  • increasingly important at high mjj, low χ
  • this is our search region

EW corrections to the angular distribution, 8 TeV

χ 1 2 3 4 5 6 78 10 20 30 EW K-factor 0.98 1 1.02 1.04 1.06 1.08 1.1 1.12 < 0.8 TeV

jj

0.6 < m < 1.2 TeV

jj

0.8 < m < 1.6 TeV

jj

1.2 < m < 2.0 TeV

jj

1.6 < m < 2.6 TeV

jj

2.0 < m < 3.2 TeV

jj

2.6 < m > 3.2 TeV

jj

m

Dittmaier, Huss, Speckner R = 0.6

t

= 8 TeV, anti-k s

Weak radiative corrections to dijet production at hadron colliders, Dittmaier et. al, arXiv:1210.0438 EW corrections, 8 TeV EW corrections, 14 TeV

Even more important at 13 TeV!

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 18 / 30

slide-22
SLIDE 22

Jet Energy Scale uncertainties

  • Dominated by η intercalibration uncertainty
  • η intercalibration: use dijet pT balance to calibrate jets in the

forward region

  • residual correction applied to data
  • corrects scale and reduces uncertainty
  • very important for the angular search!

4 − 3 − 2 − 1 − 1 2 3 4

Number of Jets 2000 4000 6000 8000 10000 12000 Pythia8 Data

ATLAS Preliminary

  • 1

= 13TeV, 0.22 nb s = 0.4 R

t

k anti > 25 GeV

jet T

|< 4.5, p

jet

|y

η detector 4 − 3 − 2 − 1 − 1 2 3 4

MC Data-MC 0.5 − 0.5

Properties of jets and inputs to jet reconstruction and calibration with the ATLAS detector using proton-proton collisions at √s = 13 TeV ATL-PHYS-PUB-2015-036 L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 19 / 30

slide-23
SLIDE 23

An aside on SM prediction methods

Dijet mass spectrum fit: data driven

  • small uncertainties, “early” search
  • angular search uses MC; historically a little later
  • First Run2 result: made public together as one search

We have shown that the understanding of the ATLAS detector is already good enough for an early first-Run2 data angular result!

Remarkable understanding of

  • detector
  • jet calibration
  • simulation

This understanding builds from the 8 TeV experience.

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 20 / 30

slide-24
SLIDE 24

Benchmark models

  • Contact Interactions (CI)
  • effective four-point interaction model
  • characterised by compositeness scale Λ
  • and by constructive or destructive interference with the QCD

process q ¯ q → q ¯ q

  • generated together with QCD in Pythia8 and brought to

NLO using CIJET

  • (non-thermal) Quantum Black Holes
  • ADD scenario with fundamental quantum gravity scale

MD = Mth (threshold mass), n = 6

  • two generators: BlackMax and QBH
  • different modelling but final distributions mostly differ by cross

section

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 21 / 30

slide-25
SLIDE 25

13 TeV results

Events

1 10

2

10

3

10

4

10 |y*| < 0.6 Fit Range: 1.1 - 5.3 TeV

  • value = 0.79

p

[TeV]

jj

m

2 3 4 5 6 7

Signif. 3 −2 − 1 − 1 2 3

ATLAS Preliminary

  • 1

=13 TeV, 80 pb s Data Background fit BumpHunter interval BlackMax, m = 4.0 TeV BlackMax, m = 5.0 TeV

χ

1 2 3 4 5 6 7 8 10 20 30 0.05 0.1 < 2.8 TeV

jj

2.5 < m 0.05 0.1 < 3.1 TeV

jj

2.8 < m 0.05 0.1 < 3.4 TeV

jj

3.1 < m χ 1/N dN/d 0.02 0.04 0.06 > 3.4 TeV

jj

m

Data SM = 6.5 TeV

th

QBH, M Theoretical uncert. Total uncertainties | < 1.1

B

|y*| < 1.7, |y

ATLAS Preliminary

  • 1

= 13 TeV, 80 pb s

  • No significant deviations from the background predictions
  • p-values of 0.79 and 0.57 respectively

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 22 / 30

slide-26
SLIDE 26

13 TeV results: highest mjj signal-like event

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 23 / 30

slide-27
SLIDE 27

95% CL lower limits

For CI, 13 TeV data set too small to be competitive. 8 TeV limits on constructive interference best to date: Λ > 12.0 TeV

13 TeV, resonance, QBH and BlackMax [TeV]

th

M 4 5 6 7 8 [pb] A × σ

3 −

10

2 −

10

1 −

10 1 10

BlackMax QBH Observed 95% CL upper limit Expected 95% CL upper limit 68% and 95% bands s

  • 1

ATLAS Preliminary

=13 TeV, 80 pb |y*| < 0.6

13 TeV, angular, QBH and BlackMax [TeV]

th

M 5.5 6 6.5 7 7.5 8 [pb] A × σ

  • 2

10

  • 1

10 1 10

2

10 Observed 95% CL Expected 95% CL σ 1 ± Expected σ 2 ± Expected BlackMax QBH

  • 1

= 13 TeV, 80 pb s ATLAS Preliminary

> 3.4 TeV

jj

m | < 1.1

B

|y*| < 1.7, |y

8 TeV, angular, constr. int. CI = -1

LL

η [TeV], Λ Compositeness scale 7 8 9 10 11 12 13 14 Signal strength 0.5 1 1.5 2 2.5

Observed 95% CL Expected 95% CL σ 1 ± Expected σ 2 ± Expected

  • 1

= 8 TeV, 17.3 fb s ATLAS

  • Resonance limits: Mth > 6.5 (6.8) TeV for BlackMax (QBH)
  • Angular limits: 6.4 (6.5) TeV
  • Angular distributions only slightly less sensitive to these resonant

phenomena!

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 24 / 30

slide-28
SLIDE 28

Outlook: extensions

Startup of Run2 – exciting times! ...but what if we don’t find anything?

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 25 / 30

slide-29
SLIDE 29

Outlook: extensions

Startup of Run2 – exciting times! ...but what if we don’t find anything?

  • we don’t stop looking

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 25 / 30

slide-30
SLIDE 30

Outlook: extensions

Startup of Run2 – exciting times! ...but what if we don’t find anything?

  • we don’t stop looking
  • we try harder

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 25 / 30

slide-31
SLIDE 31

Outlook: extensions

Startup of Run2 – exciting times! ...but what if we don’t find anything?

  • we don’t stop looking
  • we try harder
  • we add in more information!

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 25 / 30

slide-32
SLIDE 32

Strengths that can get stronger

The dijet analysis is sensitive to scale and isotropy.

  • Dijet/event properties
  • Add in single jet properties to enhance discovery potential
  • One example model: 4-jet final state

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 26 / 30

slide-33
SLIDE 33

Example model

Compositeness of light right-handed quarks as outlined in “Strong Signatures of Right-Handed Compositeness”, by M. Redi, V. Sanz, M. de Vries and A. Weiler, arXiv:1305.3818

  • compatible with constraints from precision SM tests and flavour

physics

  • large cross sections for production of resonances coupled to light

quarks

  • focus: spin-1 gluon partner, colour octet with mass mρ

Dominant production and decay modes L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 27 / 30

slide-34
SLIDE 34

... why dijets?

We don’t know the mass of the mediator or the composite quarks! Imagine mρ >> mQ

  • we get very boosted Q which subsequently decay to quarks
  • the single jet mass picks up mQ
  • the dijet mass picks up mρ
  • decays distinct from the t-channel QCD both in angle and scale

Imagine mρ ∼ 2mQ

  • Q decays to quarks at rest
  • the dijet mass picks up mQ
  • the four-jet mass picks up mρ
  • decays distinct from the t-channel QCD both in angle and scale

These are the extremes of the spectrum. Ideally a resolved and a boosted analysis is done together.

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 28 / 30

slide-35
SLIDE 35

Conclusions

  • Dijets probe the energy frontier
  • Broad search for new phenomena
  • I have shown first results from the 13 TeV data taking
  • We see good agreement between data and our background

modelling

  • We set new limits on the threshold mass of Quantum Black

Holes

  • Fast results possible due to preparation and experience – in

the team and in ATLAS

  • Longer term: extend with larger sensitivity to single-jet

properties

L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 29 / 30

slide-36
SLIDE 36

Thank you

Two or four jets? in the ATLAS Live event stream (very raw!!) L Bryngemark (Lund University) BSM searches with dijets in ATLAS Uppsala, October 1 30 / 30