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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
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
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lepton+jets: sensitive on rotating BH models (ATLAS-CONF-2016-006)
[TeV]T
p∑
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DataStandard ModelW+jetsZ+jetsttMultijetSingle TopDibosonBH2_n6_Mth6000_MD4000BH2_n6_Mth7000_MD2000
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DataStandard ModelW+jetsZ+jetsttSingle TopDibosonBH2_n6_Mth6000_MD4000BH2_n6_Mth7000_MD2000
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p∑0 0.5 1 1.5 2 2.5 3 3.5 4
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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)
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