Patrick Czodrowski - University of Alberta -

Seminar at theUniversity of Geneva

20.04.2016

SEARCHES FOR STRONG GRAVITY SIGNATURES

PRODUCED IN P-P COLLISIONS WITH THE ATLAS DETECTOR AT THE CERN LHC

The LHC

CERN

2

Exotics Searches by ATLAS

20 May 2015 ATLAS Exotics Overview 5S. Willocq

Signatures / Subgroups

illustration by:

3

Exotics Searches by ATLAS

420 May 2015 ATLAS Exotics Overview 5S. Willocq

Signatures / Subgroups

A small Selection of Results so far

5

Model ℓ, γ Jets† EmissT

!L dt[fb−1] Limit Reference

Ext

rad

ime

nsi

on

sG

au

ge

bo

son

sC

ID

ML

QH

eavy

qu

ark

sE

xcite

dfe

rmio

ns

Oth

er

ADD GKK + g/q − ≥ 1 j Yes 3.2 n = 2 Preliminary6.86 TeVMD

ADD non-resonant ℓℓ 2 e, µ − − 20.3 n = 3 HLZ 1407.24104.7 TeVMS

ADD QBH→ ℓq 1 e, µ 1 j − 20.3 n = 6 1311.20065.2 TeVMth

ADD QBH − 2 j − 3.6 n = 6 1512.015308.3 TeVMth

ADD BH high!pT ≥ 1 e, µ ≥ 2 j − 3.2 n = 6, MD = 3 TeV, rot BH ATLAS-CONF-2016-0068.2 TeVMth

ADD BH multijet − ≥ 3 j − 3.6 n = 6, MD = 3 TeV, rot BH 1512.025869.55 TeVMth

RS1 GKK → ℓℓ 2 e, µ − − 20.3 k/MPl = 0.1 1405.41232.68 TeVGKK mass

RS1 GKK → γγ 2 γ − − 20.3 k/MPl = 0.1 1504.055112.66 TeVGKK mass

Bulk RS GKK →WW → qqℓν 1 e, µ 1 J Yes 3.2 k/MPl = 1.0 ATLAS-CONF-2015-0751.06 TeVGKK mass

Bulk RS GKK → HH → bbbb − 4 b − 3.2 k/MPl = 1.0 ATLAS-CONF-2016-017475-785 GeVGKK mass

Bulk RS gKK → tt 1 e, µ ≥ 1 b, ≥ 1J/2j Yes 20.3 BR = 0.925 1505.070182.2 TeVgKK mass

2UED / RPP 1 e, µ ≥ 2 b, ≥ 4 j Yes 3.2 Tier (1,1), BR(A(1,1) → tt) = 1 ATLAS-CONF-2016-0131.46 TeVKK mass

SSM Z ′ → ℓℓ 2 e, µ − − 3.2 ATLAS-CONF-2015-0703.4 TeVZ′ mass

SSM Z ′ → ττ 2 τ − − 19.5 1502.071772.02 TeVZ′ mass

Leptophobic Z ′ → bb − 2 b − 3.2 Preliminary1.5 TeVZ′ mass

SSM W ′ → ℓν 1 e, µ − Yes 3.2 ATLAS-CONF-2015-0634.07 TeVW′ mass

HVT W ′ →WZ → qqνν model A 0 e, µ 1 J Yes 3.2 gV = 1 ATLAS-CONF-2015-0681.6 TeVW′ mass

HVT W ′ →WZ → qqqq model A − 2 J − 3.2 gV = 1 ATLAS-CONF-2015-0731.38-1.6 TeVW′ mass

HVT W ′ →WH → ℓνbb model B 1 e, µ 1-2 b, 1-0 j Yes 3.2 gV = 3 ATLAS-CONF-2015-0741.62 TeVW′ mass

HVT Z ′ → ZH → ννbb model B 0 e, µ 1-2 b, 1-0 j Yes 3.2 gV = 3 ATLAS-CONF-2015-0741.76 TeVZ′ massLRSM W ′

R→ tb 1 e, µ 2 b, 0-1 j Yes 20.3 1410.41031.92 TeVW′ mass

LRSM W ′R→ tb 0 e, µ ≥ 1 b, 1 J − 20.3 1408.08861.76 TeVW′ mass

CI qqqq − 2 j − 3.6 ηLL = −1 1512.0153017.5 TeVΛCI qqℓℓ 2 e, µ − − 3.2 ηLL = −1 ATLAS-CONF-2015-07023.1 TeVΛ

CI uutt 2 e, µ (SS) ≥ 1 b, 1-4 j Yes 20.3 |CLL | = 1 1504.046054.3 TeVΛ

Axial-vector mediator (Dirac DM) 0 e, µ ≥ 1 j Yes 3.2 gq=0.25, gχ=1.0, m(χ) < 140 GeV Preliminary1.0 TeVmA

Axial-vector mediator (Dirac DM) 0 e, µ, 1 γ 1 j Yes 3.2 gq=0.25, gχ=1.0, m(χ) < 10 GeV Preliminary650 GeVmA

ZZχχ EFT (Dirac DM) 0 e, µ 1 J, ≤ 1 j Yes 3.2 m(χ) < 150 GeV ATLAS-CONF-2015-080550 GeVM∗

Scalar LQ 1st gen 2 e ≥ 2 j − 3.2 β = 1 Preliminary1.07 TeVLQ mass

Scalar LQ 2nd gen 2 µ ≥ 2 j − 3.2 β = 1 Preliminary1.03 TeVLQ mass

Scalar LQ 3rd gen 1 e, µ ≥1 b, ≥3 j Yes 20.3 β = 0 1508.04735640 GeVLQ mass

VLQ TT → Ht + X 1 e, µ ≥ 2 b, ≥ 3 j Yes 20.3 T in (T,B) doublet 1505.04306855 GeVT mass

VLQ YY →Wb + X 1 e, µ ≥ 1 b, ≥ 3 j Yes 20.3 Y in (B,Y) doublet 1505.04306770 GeVY mass

VLQ BB → Hb + X 1 e, µ ≥ 2 b, ≥ 3 j Yes 20.3 isospin singlet 1505.04306735 GeVB mass

VLQ BB → Zb + X 2/≥3 e, µ ≥2/≥1 b − 20.3 B in (B,Y) doublet 1409.5500755 GeVB mass

VLQ QQ →WqWq 1 e, µ ≥ 4 j Yes 20.3 1509.04261690 GeVQ mass

T5/3 →Wt 1 e, µ ≥ 1 b, ≥ 5 j Yes 20.3 1503.05425840 GeVT5/3 mass

Excited quark q∗ → qγ 1 γ 1 j − 3.2 only u∗ and d∗, Λ = m(q∗) 1512.059104.4 TeVq∗ mass

Excited quark q∗ → qg − 2 j − 3.6 only u∗ and d∗, Λ = m(q∗) 1512.015305.2 TeVq∗ mass

Excited quark b∗ → bg − 1 b, 1 j − 3.2 Preliminary2.1 TeVb∗ mass

Excited quark b∗ →Wt 1 or 2 e, µ 1 b, 2-0 j Yes 20.3 fg = fL = fR = 1 1510.026641.5 TeVb∗ mass

Excited lepton ℓ∗ 3 e, µ − − 20.3 Λ = 3.0 TeV 1411.29213.0 TeVℓ∗ mass

Excited lepton ν∗ 3 e,µ, τ − − 20.3 Λ = 1.6 TeV 1411.29211.6 TeVν∗ mass

LSTC aT →W γ 1 e, µ, 1 γ − Yes 20.3 1407.8150960 GeVaT mass

LRSM Majorana ν 2 e, µ 2 j − 20.3 m(WR ) = 2.4 TeV, no mixing 1506.060202.0 TeVN0 mass

Higgs triplet H±± → ℓℓ 2 e, µ (SS) − − 20.3 DY production, BR(H±±L → ℓℓ)=1 1412.0237551 GeVH±± mass

Higgs triplet H±± → ℓτ 3 e,µ, τ − − 20.3 DY production, BR(H±±L→ ℓτ)=1 1411.2921400 GeVH±± mass

Monotop (non-res prod) 1 e, µ 1 b Yes 20.3 anon−res = 0.2 1410.5404657 GeVspin-1 invisible particle mass

Multi-charged particles − − − 20.3 DY production, |q| = 5e 1504.04188785 GeVmulti-charged particle mass

Magnetic monopoles − − − 7.0 DY production, |g | = 1gD , spin 1/2 1509.080591.34 TeVmonopole mass

Mass scale [TeV]10−1 1 10√s = 8 TeV

√s = 13 TeV

ATLAS Exotics Searches* - 95% CL ExclusionStatus: March 2016

ATLAS Preliminary"L dt = (3.2 - 20.3) fb−1

√s = 8, 13 TeV

*Only a selection of the available mass limits on new states or phenomena is shown. Lower bounds are specified only when explicitly not excluded.

†Small-radius (large-radius) jets are denoted by the letter j (J).

* large discrepancy between weak O(103) GeV and Planck scale O(1019) GeV

Many open Questions and many Proposals/Theories

• Many theories propose solutions to fundamental questions - let’s focus on the hierarchy problem* Proposal: gravity can propagate in extra dimensions, thus Quantum Black Holes (QBH) are allowed due to a reduced effective Planck scale

• 1) Arkani-Hamed, Dimopoulos, Dvali (ADD) proposal: introduces n large extra dimensions and thus a new fundamental Planck scale, MD

• 2) Randall–Sundrum (RS) model: five-dimensional with a highly warped anti-de Sitter space (AdSn(5))

6

Low-scale gravity signature searches

• Q: What are these “low-scale gravity signatures”?

• A: Black Holes and String Balls (highly excited long and jagged strings)

• Q: How do they decay and thus present themselves to the analyser?

• A: Via Hawking radiation => relatively large number of high-transverse-momentum (high-pT) particles, democratic* decay. Thus the scalar sum of pT (HT) is utilized as discriminating variable (currently experimenting with invariant mass)

arXiv:hep-ph/0108060

HT =X

pT 7* in SM: mostly jets (due to color charge)

Problem: the SM background almost exclusively QCD multi-jet - do not want to rely on MonteCarlo simulation (MC)

Multi-jet search √s = 8 TeV (2012)

8

1.5 2 2.5 3 3.5 4 4.5 5

Even

ts/0

.1 T

eV

1

10

210

310

410

510

-1=8 TeV, 20.3 fbsATLAS Multi-jets

tt+jetsγW+jetsZ+jetsTotalData

3≥ jetN

[TeV]TH1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Dat

a/M

C

0.60.81.01.21.4 1.5 2 2.5 3 3.5 4 4.5 5

Even

ts/0

.1 T

eV

1

10

210

310-1=8 TeV, 20.3 fbs

ATLAS Multi-jetstt+jetsγW+jetsZ+jetsTotalData

8≥ jetN

[TeV]TH1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Dat

a/M

C

0.60.81.01.21.4

Solution: a fit and extrapolation method of the HT spectrum in inclusive jet multiplicities (Njet ≥ x, with 3≤x≤8 )

arXiv:1503.08988

Tested a plethora of empirical functions able to describe the full HT spectrum (in MC)

Multi-jet search √s = 8 TeV (2012)

9

Envelope of alternate fit functions was assigned as “fit-function selection” uncertainty

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0Ev

ents

/0.1

TeV

1

10

210

3102

p/x1

p (1-x)

0p

)2x2

exp(p1p

(1-x)0

px

2p

x1p

(1-x)0

pln(x)]

2-p

1[p

/x)(1-x)0

(pln(x)]

2-p

1[p

)(1-x)2/x0

(p

8≥ jetN

ATLAS

[TeV]TH1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Fit/N

om F

it0.60.81.01.21.41.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Even

ts/0

.1 T

eV

1

10

210

310

410

2p

/x1p

(1-x)0

p

)2x2

exp(p1p

(1-x)0

px

2p

x1p

(1-x)0

pln(x)

2p

x1p

(1-x)0

pln(x)

2p

(1+x)1p

(1-x)0

p

3≥ jetN

ATLAS

[TeV]TH1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Fit/N

om F

it

0.60.81.01.21.4

arXiv:1503.08988

1.5 2 2.5 3 3.5 4 4.5 5

Even

ts/0

.1 T

eV

1

10

210

310

8≥ jetN

Total uncertaintyData

=3.5 TeVD

=5.0, MTh

n=2, M=3.5 TeV

D=5.0, M

Thn=4, M

=3.5 TeVD

=5.0, MTh

n=6, M

-1=8 TeV, 20.3 fbsATLAS

ExtrapolationFit

[TeV]TH1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Dat

a/Pr

ed

0.60.81.01.21.4 1.5 2 2.5 3 3.5 4 4.5 5

Even

ts/0

.1 T

eV

1

10

210

310

410

3≥ jetN

Total uncertaintyData

=3.5 TeVD

=5.0, MTh

n=2, M=3.5 TeV

D=5.0, M

Thn=4, M

=3.5 TeVD

=5.0, MTh

n=6, M

-1=8 TeV, 20.3 fbs

ATLAS

ExtrapolationFit

[TeV]TH1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Dat

a/Pr

ed

0.60.81.01.21.4

Define Control Region (excluded by prev. searches) and “open the box” (first & last time to look at data in the Signal Region)

Multi-jet search √s = 8 TeV (2012)

10

Unfortunately no excess observed ➝ proceed to limit setting

CR SRCR SR

arXiv:1503.08988

arXiv:1503.08988

(+signal MC)

1. model- independent

limits

2. model-specific limits

[TeV]minTH

3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0

[fb]

∈ × A

×)

min

T>H T

(Hσ

0

2

4

6

8

10

3≥ jetNσ2±Expected σ1±Expected

ExpectedObserved

ATLAS-1=8 TeV, 20.3 fbs

95% CL upper limits

[TeV]minTH

3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0

[fb]

∈ × A

×)

min

T>H T

(Hσ

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

8≥ jetNσ2±Expected σ1±Expected

ExpectedObserved

ATLAS-1=8 TeV, 20.3 fbs

95% CL upper limits

[TeV]DM1.5 2.0 2.5 3.0 3.5 4.0

[TeV

]th

M

4.5

5.0

5.5

6.0

6.5

Expected, n=2Observed, n=2Expected, n=4Observed, n=4Expected, n=6Observed, n=6

ATLAS-1=8 TeV, 20.3 fbs

exclusion95% CL

BlackMax

D/MThk=M

k=2k=3k=4Black holes, Non-rotating

[TeV]sM1.0 1.5 2.0 2.5 3.0

[TeV

]th

M4.5

5.0

5.5

6.0

6.5

Expected, Non-rotatingObserved, Non-rotatingExpected, RotatingObserved, Rotating

ATLAS

-1=8 TeV, 20.3 fbsCHARYBDIS2

s/MThk=M

k=2

k=3k=4k=5

k=6

String balls

exclusion95% CL

(assumptions of the models not valid for k = 1, but are valid for k ≫ 1)

(assumptions of the models not valid for k = 1, but are valid for k ≫ 1)

Hmin

T =

Z 1

x

HT

Mth = creation threshold MD = fundamental Planck scale

Multi-jet search √s = 8 TeV (2012)

11

source: W.J. Stirling, private communication (edited)

strong interaction dominated processes

electroweak processes

4000

Round (or Run) 2: increasing the center of mass energy (√s)

• Our search can significantly extend the 8 TeV reach already with a few fb-1 of 13 TeV collision data

• Why is that?

12

Multi-jet search √s = 13 TeV (2015)

13

Even

ts /

0.1

TeV

2−10

1−10

1

10

210

310 ATLASStep 1

-1 L dt = 6.5 pb∫ = 13 TeV, s

3≥ jetn

Data 2015Multijets

= 6 TeV th

= 2.5 TeV, MDM

[TeV]TH1 1.5 2 2.5 3 3.5 4 4.5 5 5.5

Dat

a/M

C

00.5

11.5

2

Even

ts /

0.1

TeV

2−10

1−10

1

10

210

310

410 ATLASStep 2

-1 L dt = 74 pb∫ = 13 TeV, s

3≥ jetn

Data 2015Multijets

= 7.5 TeV th

= 3 TeV, MDM

[TeV]TH1 2 3 4 5 6

Dat

a/M

C

00.5

11.5

2

Due to the increased cross sections and thus expected statistics apply concepts that were not possible before

The bootstrapping approach: add data in increasing steps (~approx. factor 10) from step to step - starting at Run 1 sensitivity to avoid potential signal contamination

CR

SRVR

CR

SRVR

arXiv:1512.02586

Even

ts /

0.1

TeV

2−10

1−10

1

10

210

310

410

510

610 ATLASStep 4

-1 L dt = 3.0 fb∫ = 13 TeV, s

3≥ jetn

Data 2015tMultijets+t

tt = 9 TeV

th = 2.5 TeV, MDM

[TeV]TH1 2 3 4 5 6 7 8

Dat

a/M

C

00.5

11.5

2

Even

ts /

0.1

TeV

2−10

1−10

1

10

210

310

410

510 ATLASStep 3

-1 L dt = 0.44 fb∫ = 13 TeV, s

3≥ jetn

Data 2015Multijets

= 8 TeV th

= 4.5 TeV, MDM

[TeV]TH1 2 3 4 5 6 7

Dat

a/M

C

00.5

11.5

2

Multi-jet search √s = 13 TeV (2015)

14

From step to step take the sensitivity from the previous as input (caveat: you have to discard data from step 1-3)

Add one more region to the procedure: the Validation Region (VR) as a further signal contamination x-check

CRSRVR

CRSRVR

arXiv:1512.02586

Even

ts /

0.1

TeV

1−10

1

10

210

310

410

Step 2Data 2015

ln (x)2

px1p

)1/3(1-x0

(x) = p10f2

p/x1

p(1-x)

0(x) = p1f

x2

p x1

p(1-x)

0(x) = p3f

ln (x)2

px1

p(1-x)

0(x) = p4f

x2

p(1+x)1

p(1-x)

0(x) = p5*f

ln (x)2

p(1+x)1

p(1-x)

0(x) = p6f

2p

/x1p

)1/3(1-x0

(x) = p9f

Rejected in validation region

ATLAS-1 L dt = 74 pb∫

= 13 TeVs 3≥ jetn

[TeV]TH2 3 4 5 6

data

σ(d

ata

- fit)

/

2−1.5−

1−0.5−

00.5

11.5

2

Even

ts /

0.1

TeV

1−10

1

10

210

310

Step 1Data 2015

ln (x)2

px1

p(1-x)

0(x) = p4f

2p

/x1p

(1-x)0

(x) = p1f

2p

/x1p

)1/3(1-x0

(x) = p9f

ln (x)2

px1p

)1/3(1-x0

(x) = p10f

ATLAS-1 L dt = 6.5 pb∫

3≥ jetn = 13 TeVs

[TeV]TH1 1.5 2 2.5 3 3.5 4 4.5 5

data

σ(d

ata

- fit)

/

2−1.5−

1−0.5−

00.5

11.5

2

Multi-jet search √s = 13 TeV (2015)

15

Opening the box:

CR

SR

VR

CR

SRVR

(note the x-axis scale changing)

arXiv:1512.02586

Even

ts /

0.1

TeV

1−10

1

10

210

310

410

Step 4Data 2015

x2

p(1+x)1

p(1-x)

0 (x) = p5f

2p

/x1p

(1-x)0

(x) = p1*f2x

2p

e1p

(1-x)0

(x) = p2f x2

p x1

p(1-x)

0 (x) = p3f ln (x)

2p

x1p

(1-x)0

(x) = p4*fln (x)

2p

(1+x)1p

(1-x)0

(x) = p6f/x

ln (x)2

-p1

p(1-x)

0 (x) = p7f

2/xln (x)

2-p

1p

(1-x)0

(x) = p8f2

p/x1

p)1/3(1-x

0 (x) = p9f ln (x)

2p

x1p

)1/3(1-x0

(x) = p10*fRejected in validation region

ATLAS-1 L dt = 3.0 fb∫

3≥ jetn = 13 TeVs

[TeV]TH2 3 4 5 6 7 8

data

σ(d

ata

- fit)

/

3−

2−

1−

0

1

2

3

Even

ts /

0.1

TeV

1−10

1

10

210

310

410

Step 3Data 2015

ln (x)2

px1

p)1/3(1-x

0 (x) = p10f

2p

/x1p

(1-x)0

(x) = p1f2x

2p

e1p

(1-x)0

(x) = p2fx

2p

x1p

(1-x)0

(x) = p3fln (x)

2p

x1p

(1-x)0

(x) = p4fx

2p

(1+x)1p

(1-x)0

(x) = p5fln (x)

2p

(1+x)1p

(1-x)0

(x) = p6f/x

ln (x)2

-p1

p(1-x)

0 (x) = p7f

2/xln (x)

2-p

1p

(1-x)0

(x) = p8f2

p/x1

p)1/3(1-x

0 (x) = p9f

ATLAS-1 L dt = 0.44 fb∫

= 13 TeVs 3≥ jetn

[TeV]TH2 3 4 5 6 7

data

σ(d

ata

- fit)

/

3−

2−

1−

0

1

2

3

Multi-jet search √s = 13 TeV (2015)

16

Opening the box - continued:

CR

SRVR

CR

SR

VR

Unfortunately no excess observed ➝ proceed to limit setting

arXiv:1512.02586

[TeV]SM3 3.5 4 4.5 5

[TeV

]th

M5

6

7

8

9

10

11

12

13

3)≥ jet

Expected (n 3)≥

jetObserved (n

σ 1 ±

σ 2 +

ATLAS

= 0.6sg

-1 L dt = 3.0 fb∫ = 13 TeVs 95% CL exclusion (n = 6)

Rotating string ballsCHARYBDIS2

[TeV]DM2 2.5 3 3.5 4 4.5 5 5.5

[TeV

]th

M

6

7

8

9

10

11

12

13

14

ExpectedObserved

σ 1 ±σ 2 +

= 8 TeVsATLAS = 13 TeVs) -1Step 1 (6.5 pb

= 13 TeVs) -1Step 2 (74 pb = 13 TeVs) -1Step 3 (.44 fb

ATLAS

-1 L dt = 3.0 fb∫ = 13 TeVs

Rotating black holesCHARYBDIS2 3)≥

jet95% CL exclusion (n = 6, n

arXiv:1512.02586

Multi-jet search √s = 13 TeV (2015)

17

That was that - and now?

Final results (model-specific only this time):

(in Run1 we had 20 fb-1 in 2012)

Food for Thought

18

- The best (Mth independent) MD limit actually stem from a Run 1 mono-jet analysis by CMS arxiv:1408.3583

arXiv:1509.07180

- Requiring Mth/MD >> 1 for model validity shows us that most models considered for our searches are only valid beyond LHC energies

- The theory community cannot use model dependent limits easily - due to unknown detector/selection acceptances Further: HT is hard to model - be kind: express your limits in minv

Run-I limits on MDThe best limits on MD (independent of Mth) come from the CMS run-Imonojet search (http://arxiv.org/abs/1408.3583)12 8 Summary

δ2 3 4 5 6

[TeV

]D

M

0

1

2

3

4

5

6

7

8

9

-1CMS (LO) 8 TeV, 19.7 fb-1CMS (LO) 7 TeV, 5.0 fb

-1ATLAS (LO) 7 TeV, 4.7 fbLEP limitCDF limit

limit∅D

CMS 95% CL limits

Figure 7: Lower limits at 95% CL on MD plotted against the number of extra dimensions �, withresults from the ATLAS [25], CMS [11], LEP [19–21, 78], CDF [22], and DØ [23] collaborations.

Ud1 1.2 1.4 1.6 1.8 2

[TeV

]U

Λ

0

1

2

3

4

5

6

7

8

-18 TeV, 19.7 fb-17 TeV, 36 pb

CDF + Theory

CMS95% CL lower bound limit

for scalar unparticlesUΛ

Figure 8: The expected and observed lower limits on the unparticle model parameters �U as afunction of dU at 95% CL, compared to previous results [24, 79]. The shaded region indicatesthe side of the curve that is excluded.

Table 8: Expected and observed 95% CL lower limits on �U (in TeV) for scalar unparticles withdU =1.5, 1.6, 1.7, 1.8 and 1.9 and a fixed coupling constant � = 1.

dU Expected limit on �U (TeVns) +1� �1� Observed limit on �U (TeV)1.5 7.88 6.63 8.39 10.001.6 3.89 2.51 4.88 4.911.7 2.63 2.09 2.89 2.911.8 1.91 1.76 1.98 2.011.9 1.41 0.88 1.46 1.60

TeV corresponding to an integrated luminosity of 19.7 fb�1. The dominant backgrounds to thistopology are from Z(��)+jets and W(��)+jets events, and are estimated from data samples of

Applying these limits, and realising that= Mth

MD>> 1 for the model to be valid, pushes the

region of validity of the models we considerbeyond the LHC energy reach.

�

�

MD

Mth

������������������������������

MD(limit)

k = 5

allowed region�

Mth > 16 TeV

Figure 1: GR black hole search parameter space. The valid region is to the right of thevertical MD(limit) line and to the left of the k = 5 line.

All searches for GR black holes have set model-dependent limits. However, recent resultsfrom ATLAS using 80 pb�1 of data with the LHC running at 13 TeV centre of mass energyhave set the the most stringent limits. A multi-jet analysis [37] obtains Mth > 8.5� 7.5 TeVfor MD = 2 � 5 TeV (k = 4.2 � 1.5) at the 95% CL. Invoking the current limits on MD

gives Mth > 8.1 TeV (k = 2.5). Similarly, a �+jets analysis [38] obtains Mth > 7.3� 5.9 TeVfor MD = 2 � 4 TeV (k = 3.6 � 1.5) at the 95% CL. Invoking the current limits on MD

gives Mth > 6.4 TeV (k = 2). While these are significant improvements over the massthreshold limits at 8 TeV proton–proton centre of mass energy, they are still not in a regionof parameter space in which the models are particularly valid.

3.2 Searches for string balls

Embedding weakly-coupled string theory into ADD results in string ball states that couldbe searched for at the LHC [8]. The model [14] modifies the black hole cross section, but

7

Plot credit: DougGingich

Sarah Williams (Nikhef) Exotics/HBSM Workshop March 3, 2016 17 / 20

Future of the Multi-jet searches

• Many more models to consider - BUT as just stated: model independent limits are strongly preferred by our “clients”

• New method: the so-called Hemisphere method will be studied in the coming months

19

Hempisphere method for background estimation in themultijet analysis

• Development of Hemespheres Method - a new data driven bkg estimation technique:

‣Procedure - Divide events into hemispheres ‣Assumption - Bkg to have independent Njets in each hemisphere. Signal will. ‣Advantages - completely data driven. Clear physical motivation.2 by 2 process BH production

• Study of Event Shape Variables

Slides courtesy of Daniel TurgemanSarah Williams (Nikhef) Exotics/HBSM Workshop March 3, 2016 19 / 20

Conclusions

• As TeV gravity searches benefit dominantly from √s increases than more luminosity these searches will be continued - but with a lower priority

• If all goes well we will see stable collisions very very soon again in the LHC

• We expect up to five times the luminosity from LHC this year - there is a lot of physics to be done

Thus: Stay tuned for more news from the LHC!20

THANK YOU A LOT FOR YOUR ATTENTION

TIME FOR QUESTIONS, SUGGESTIONS AND IDEAS

22

Back up!

Other Exotic final state searches

23

Feel invited to browse:

https://twiki.cern.ch/twiki/bin/view/AtlasPublic/ExoticsPublicResults

the following link is restricted to ATLAS members, but if you are a member and looking for a nice topic to work on please see:

https://twiki.cern.ch/twiki/bin/view/AtlasProtected/ExoticsRun2UncoveredAnalyses

An other ATLAS TeV gravity search

24

lepton+jets: sensitive on rotating BH models (ATLAS-CONF-2016-006)

[TeV]T

p∑

Even

ts /

0.25

TeV

-110

1

10

210

310

410

510

610

710ATLAS Preliminary

=13 TeVs, -13.2 fb

Electron channel

DataStandard ModelW+jetsZ+jetsttMultijetSingle TopDibosonBH2_n6_Mth6000_MD4000BH2_n6_Mth7000_MD2000

[TeV]T

p∑0 0.5 1 1.5 2 2.5 3 3.5 4

Dat

a / S

M

0

1

2 [TeV]T

p∑

Even

ts /

0.25

TeV

-110

1

10

210

310

410

510

610

710ATLAS Preliminary

=13 TeVs, -13.2 fb

Muon channel

DataStandard ModelW+jetsZ+jetsttSingle TopDibosonBH2_n6_Mth6000_MD4000BH2_n6_Mth7000_MD2000

[TeV]T

p∑0 0.5 1 1.5 2 2.5 3 3.5 4

Dat

a / S

M

0

1

2

[GeV]Dm2000 2500 3000 3500 4000 4500 5000

[GeV

]Th

m

6000

7000

8000

9000

10000

ATLAS Preliminary=13 TeVs, -13.2 fb

Observed (n=6) Expected (n=6)

(n=6)expσ±Expected Observed limit (n=4) Expected limit (n=4) Observed limit (n=2) Expected limit (n=2) ATLAS 8 TeV (n=6)

Observed (n=6) Expected (n=6)

(n=6)expσ±Expected Observed limit (n=4) Expected limit (n=4) Observed limit (n=2) Expected limit (n=2) ATLAS 8 TeV (n=6)

Exclusion contours in the Mth, MD plane for rotating black hole models with 2, 4 & 6 extra dimensions (simulated with Charybdis2 1.0.4)

<= 17 vertices 25