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01/12/2014 Kruger 2014, K. Hamano 1
Search for Exotics (and Higgs) Physics beyond the Standard Model with the ATLAS Detector
Kenji Hamano (University of Victoria) on behalf of the ATLAS Collaboration
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Plan of this talk § LHC and ATLAS detector. § Signature based search strategy. § Dileptons/Multi-leptons signature § Lepton(s) + jet(s) signature § Dijets/Multi-jets signature § Top quarks signature § Vector bosons signature § Other signatures § Conclusions.
01/12/2014 Kruger 2014, K. Hamano 2
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Other topics § BSM Higgs:
§ “Beyond the Standard Model Higgs Physics Using the ATLAS Detector” (Guillermo Hamity).
§ Dark Matter: § “Searches for Dark Matter with the ATLAS
Detector” (Ketevi Assamagan). § Supersymmetry (SUSY):
§ “SUSY Searches in the ATLAS Detector” (Lawrence Lee JR).
01/12/2014 Kruger 2014, K. Hamano 3
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LHC § Large Hadron Collider (LHC)
§ Collide two protons (pp-collision). § Center of mass energy:
§ Run1: 2011, 7 TeV, ~5 fb-1; 2012, 8 TeV, ~20 fb-1 § Run2 (2015 ~): 13 TeV or 14 TeV
01/12/2014 Kruger 2014, K. Hamano 4
• Only recent results with 8TeV data are presented in this talk.
• Selection is based on my preference.
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ATLAS Detector § From inside to outside
§ Inner tracker: reconstruct charged tracks. § Calorimeter: detect particle energies.
§ Electromagnetic calorimeter: electros and photons § Hadronic calorimeter: charged and neutral hadrons.
§ Muon detector: detect muons.
01/12/2014 Kruger 2014, K. Hamano 5
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Need for BSM physics § There are many problems with the Standard
Model (SM). § Hierarchy Problem § Neutrino mass term § Dark matter § Gravity § …
§ Possible solution is a Beyond the Standard Model (BSM) physics? § Supersymmetry? § Extra dimensions? § Higher symmetry/Unified model? § Seesaw mechanism? § …
01/12/2014 Kruger 2014, K. Hamano 6
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Signature based search (1) § To search for a new physics, experimentalists
look for particles in final states produced by the new physics.
§ An example: Zee-Babu model § Physics point of view:
§ A model to generate small neutrino mass with a two loop diagram.
§ Introduce two new scalar particles: h+, k++ § Lepton flavor violation is also introduced.
§ Experimental point of view: § Look for the new particles. § How they are produced in pp-collisions? § How they decay?
01/12/2014 Kruger 2014, K. Hamano 7
h−
eR
k−−
νL eR
eL eL
νL
h−
⟨H⟩ ⟨H⟩
Figure 1: Diagram contributing to the neutrino Majorana mass at two loops.
for instance we can take fµτ real and positive. Of course the counting of parameters is the
same as before: we will have 12 moduli (3 from Y , 3 from f and 6 from gab) and 5 phases
(3 from gab and 2 from fab) and the real and positive parameter µ.
In any of the discussed conventions, Y is directly related to the masses of charged leptons
ma = Yaav, with v ≡ ⟨H0⟩ = 174 GeV, the VEV of the standard Higgs doublet. Then the
physical scalar masses are
m2h = m′2h + λhHv
2 , m2k = m′2k + λkHv
2 . (8)
A. The neutrino masses
The first contribution to neutrino masses involving the four relevant couplings appears
at two loops [19, 20] and its Feynman diagram is depicted in fig. 1.
The calculation of this diagram gives the following mass matrix for the neutrinos (defined
as an effective term in the Lagrangian Lν ≡ −12νcLMννL + h.c.)
(Mν)ab = 16µfacmcg∗cdIcdmdfbd , (9)
with
Icd =
∫d4k
(2π)4
∫d4q
(2π)41
(k2 −m2c)1
(k2 −m2h)1
(q2 −m2d)1
(q2 −m2h)1
(k − q)2 −m2k. (10)
Icd can be calculated analytically [33], however, since mc, md are the masses of the charged
leptons, necessarily much lighter than the charged scalars, we can neglect them and obtain
8
ArXiv:0711.0483
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Signature based search (2) § Production
§ The new particle k is either pair produced or produced along with h.
§ Decay § k++ à e+e+, e+µ+, µ+µ+, etc.
§ Look for same-sign lepton pair(s) in final states.
01/12/2014 Kruger 2014, K. Hamano 8
γ∗, Z∗
q
q
k−−
k++
Figure 2: Pair production of k
gauge charges as well as depending only on one unknown parameter: the mass of the scalar.
The partonic cross section at LO reads
σ =πα2Q2β3
6
[2Q2qŝ−
2(gL + gR)Qqc2w
ŝ−M2Z(ŝ−M2Z)2 + Γ2ZM2Z
+(g2L + g
2R)
c4w
ŝ
(ŝ−M2Z)2 + Γ2ZM2Z
],
(30)
where ŝ is the energy squared in the center of mass frame (CM) of the quarks, Q stands for
electric charges, gL and gR are given for the quarks by gL = T3 − s2wQq and gR = −s2wQqand β is the velocity of the produced scalars in this frame β =
√1− 4m2/ŝ.
Equation (30) shows that pair production is four times more efficient for k than for h due
to their charges (assuming equal masses), which translates into a better discovery potential
for k. The k pair production cross section, σkk, at NLO for the LHC and Tevatron is displayed
in fig. 3. To compute it, we have used CompHEP [62] with CTEQ6.1L libraries [63] to find
the LO cross section and afterwards we have included a K-factor of 1.25 for the LHC and
1.3 for Tevatron to take into account NLO corrections, see [64].
Single production might be also interesting when double production is not possible. Single
production can proceed with a k accompanied by two singly charged scalars, fig. 4, or by
two charged leptons replacing the scalar h’s. If the k is accompanied by two charged leptons
the amplitudes are proportional to the Yukawa couplings, whose exact values we ignore and
might be small.
It is important to note that the cross section will be dominated by the virtual particles
in the propagators if they could be on-shell. In the case of k being produced with two h, the
single production will be dominated by the first diagram if ŝ > 2mk, because in this case
k∗ can be created on-shell. One might argue that the energy in the center of mass frame of
17
500 1000 1500mk (GeV)
0.001
0.01
0.1
1
10
100
σ (fb)
14 TeV (LHC)2 TeV (Tevatron)
Figure 3: Pair production cross section for k. We have used CompHEP (CTEQ6.1L) to obtain the
LO and applied a K-factor of 1.25 for the LHC and 1.3 for Tevatron.
γ∗, Z∗ k∗
q
q
k++
h−
h−
γ∗, Z∗h∗
q
q
h−
k++
h−
Figure 4: Single production diagrams.
the colliding quarks is not fixed, instead it is a fraction of the total energy in the center of
mass frame of the colliding protons, s. However, the cross section involves an integration
over the possible values of ŝ. If s is large enough to create two k’s, the integration will be
dominated by the real production of two k’s, thus reducing the single production to pair
production. Specifically, σ(k++h−h−) ≈ σkkBr(k → hh). The same reasoning is valid in the
case of single production with leptons. We have performed calculations using CompHEP to
check this point. Therefore, single production is only important when the available energy,
s, is not sufficient to create a pair of k.
18
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Signature vs Physics models § Many new physics models can be searched by
same signature. § (Example) Same-sign diletpon signature:
§ SUSY, Universal Extra Dimensions, Left-right symmetric models, neutrino mass models, Doubly charged Higgs, Vector-like quarks.
01/12/2014 Kruger 2014, K. Hamano 9
§ A new model can be probed by many signatures. § (Example) Type III
seesaw model: § 2 leptons + 2 jets § 3 leptons § 4 leptons
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Dileptons/Multi-leptons § Dileptons
§ Opposite-sign same flavor § High mass resonance search (arXiv:1405.4123, PRD90,052005(2014))
§ Heavy gauge boson Z’, Excited boson Z*, Spin-2 graviton, Quantum Black Holes, Technicolor
§ Non-resonant dileptons (arXiv:1407.2410, EPJC) § Contact Interaction (llqq), Large Extra Dimensions
§ Opposite-sign mixed flavor § Lepton Flavor Violation: Z à e µ (arXiv:1408.5774, PRD90,072010(2014))
§ Same-sign dileptons (arXiv:1412.0237, JHEP) § SUSY, Extra dimension, Neutrino mass models, Doubly-
charged Higgs
§ 3 or more leptons (arXiv:1411.2921) § SUSY, Neutrino mass models, Doubly-charged Higgs
01/12/2014 Kruger 2014, K. Hamano 10
More details on Blue analysis
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Dileptons/Multi-leptons (2) § Diphoton resonance (arXiv:1210.8389, NJP15,242(2013))
§ KK Graviton (Extra dimensions)
01/12/2014 Kruger 2014, K. Hamano 11
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Dilepton resonance (arXiv:1405.4123, PRD90,052005(2014))
§ Z’ and Z* à l+l-
01/12/2014 Kruger 2014, K. Hamano 12
Even
ts
-110
1
10
210
310
410
510
610
710Data 2012
*γZ/Top quarkDijet & W+JetsDibosonZ’ SSM (1.5 TeV)Z’ SSM (2.5 TeV)
ATLAS ee →Z’
-1 L dt = 20.3 fb∫ = 8 TeV s
[TeV]eem0.08 0.1 0.2 0.3 0.4 0.5 1 2 3 4
Dat
a/Ex
pect
ed
0.60.8
11.21.4
Even
ts
-110
1
10
210
310
410
510
610
710Data 2012
*γZ/Top quarkDibosonZ’ SSM (1.5 TeV)Z’ SSM (2.5 TeV)
ATLAS µµ →Z’
-1 L dt = 20.5 fb∫ = 8 TeV s
[TeV]µµm0.08 0.1 0.2 0.3 0.4 0.5 1 2 3 4
Dat
a/Ex
pect
ed
0.60.8
11.21.4
ee mass µµ mass
• Two isolated opposite-charge same-flavor leptons.
• Electron: leding ET>40GeV, subleading ET>30GeV
• Muon pT>25GeV
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Dilepton Resonane (2)
01/12/2014 Kruger 2014, K. Hamano 13
[TeV]Z’M0.5 1 1.5 2 2.5 3 3.5
B [p
b]σ
-410
-310
-210
SSMObserved limit Z’χObserved limit Z’ψObserved limit Z’
Observed limit Z*SSMZ’χZ’ψZ’
Z*
ATLAS = 8 TeVs
-1 L dt = 20.3 fb∫ee: -1 L dt = 20.5 fb∫: µµ
SSMObserved limit Z’χObserved limit Z’ψObserved limit Z’
Observed limit Z*SSMZ’χZ’ψZ’
Z*
13
[TeV]SSMZ’
M0.5 1 1.5 2 2.5 3 3.5
B [p
b]σ
-410
-310
-210
-110µµExpected limit µµObserved limit
Expected limit eeObserved limit eeExpected limit llObserved limit ll
SSMZ’
ATLAS
ll→ SSMZ’ = 8 TeVs
-1 L dt = 20.3 fb∫ee: -1 L dt = 20.5 fb∫: µµ
µµExpected limit µµObserved limit
Expected limit eeObserved limit eeExpected limit llObserved limit ll
SSMZ’
FIG. 4. Median expected (dashed line) and observed (solidline) 95% CL upper limits on cross-section times branchingratio (σB) for Z′SSM production for the exclusive dimuon anddielectron channels, and for both channels combined. Thewidth of the Z′SSM theory band represents the theoretical un-certainty from the PDF error set, the choice of PDF as wellas αS .
Figure 3 also contains the Z ′SSM theory band for σB. Itswidth represents the theoretical uncertainty, taking intoaccount the following sources: the PDF error set, thechoice of PDF, and αS . The value of MZ′ at which thetheory curve and the observed (expected) 95% CL limitson σB intersect is interpreted as the observed (expected)mass limit for the Z ′SSMboson, and corresponds to 2.90(2.87) TeV.
A comparison of the combined limits on σB and thosefor the exclusive dielectron and dimuon channel is givenin Figure 4. This demonstrates the contribution of eachchannel to the combined limit. As expected from Fig. 1,the larger values for A×ϵ in addition to the better resolu-tion in the dielectron channel results in a stronger limitthan in the dimuon channel. The observed (expected)Z ′SSM mass limit is 2.79 (2.76) TeV in the dielectron chan-nel, and 2.53 (2.53) TeV in the dimuon channel.
Figure 5 shows the observed σB exclusion limits at95% CL for the Z ′SSM, Z
′χ, Z
′ψ and Z
∗ signal searches.Here only observed limits are shown, as they are alwaysvery similar to the expected limits (see Fig. 4). The the-oretical σB of the boson for the Z ′SSM, two E6-motivatedModels and Z∗ are also displayed. The 95% CL limits onσB are used to set mass limits for each of the consideredmodels. Mass limits obtained for the Z ′SSM, E6-motivatedZ ′ and Z∗ bosons are displayed in Table VII.
As demonstrated in Fig. 5, for lower values of MZ′ thelimit is driven primarily by the width of the signal andgets stronger with decreasing width. At large MZ′ , theσB limit for a given Z ′ model worsens with increasingmass. This weakening of the limit is due to the pres-ence of the parton-luminosity tail in the mℓℓ line shape.The magnitude of this degradation is proportional to the
[TeV]Z’M0.5 1 1.5 2 2.5 3 3.5
B [p
b]σ
-410
-310
-210
SSMObserved limit Z’χObserved limit Z’ψObserved limit Z’
Observed limit Z*SSMZ’χZ’ψZ’
Z*
ATLAS = 8 TeVs
-1 L dt = 20.3 fb∫ee: -1 L dt = 20.5 fb∫: µµ
SSMObserved limit Z’χObserved limit Z’ψObserved limit Z’
Observed limit Z*SSMZ’χZ’ψZ’
Z*
FIG. 5. Observed upper cross-section times branching ra-tio (σB) limits at 95% CL for Z′SSM, E6-motivated Z
′ and Z∗
bosons using the combined dilepton channel. In addition, the-oretical cross-sections on σB are shown for the same models.The stars indicate the lower mass limits for each consideredmodel. The width of the Z′SSM band represents the theoret-ical uncertainty from the PDF error set, the choice of PDFas well as αS. The width of the Z
′SSM band applies to the
E6-motivated Z′ curves as well.
size of the low-mass tail of the signal due to much higherbackground levels at low mℓℓ compared to high mℓℓ. AllZ ′ models exhibit a parton-luminosity tail, the size ofwhich increases with increasing natural width of the Z ′
resonance. The tail is most pronounced for Z ′SSM, andleast for Z ′ψ, in line with the different widths given inTable VII. Even though the width of the Z∗ is similar tothe width of the Z ′SSM, the tensor form of the coupling ofthe Z∗ to fermions strongly suppresses parton luminosityeffects. Limits on σB for the Z∗ interpretation thereforedo not worsen with increasing invariant mass. Quantita-tively, the observed Z ′SSM mass limit would increase from2.90 TeV to 2.95 TeV and 3.08 TeV, if the Z ′χ and Z
′ψ bo-
son signal templates, with smaller widths, were used. Ifthe Z∗ boson template with negligible parton-luminositytail but similar width were used instead of the Z ′SSM tem-plate, the observed limit would increase to 3.20 TeV.
TABLE VII. Observed and expected lower mass limits for Z′
and Z∗ bosons, using the corresponding signal template for agiven model.
Model Width Observed Limit Expected Limit[%] [TeV] [TeV]
Z′SSM 3.0 2.90 2.87Z′χ 1.2 2.62 2.60Z′ψ 0.5 2.51 2.46Z∗ 3.4 2.85 2.82
Mass limits
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LFV Z à e µ (arXiv:1408.5774, PRD90,072010(2014)) § Lepton Flavor Violation (LFV) decay Zàeµ.
01/12/2014 Kruger 2014, K. Hamano 14
[GeV]µem70 75 80 85 90 95 100 105 110
Even
ts /
2 G
eV
0
100
200
300
400
500
600
700MC stat. error
µµ ee/→Z ττ →Z
MultijetWDibosonTopData
µ e→Z -5 10×B = 1.0
-1 = 8 TeV, 20.3 fbs
ATLAS
[GeV]µem70 75 80 85 90 95 100 105 110
Even
ts /
GeV
50
100
150
200
250
300Data
Fit
-7 10×B = 7.5
-1 = 8 TeV, 20.3 fbs
/DOF = 0.752χ
ATLAS
[GeV]µem70 75 80 85 90 95 100 105 110
Dat
a - F
it
-20-10
01020
B(Z à eµ) < 7.5*10-7
Isolated e with ET>25GeV Isolated µ with pT>25GeV Missing ET
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Same-sign dilepton (arXiv:1412.0237, JHEP)
01/12/2014 Kruger 2014, K. Hamano 15
• Two isolated same-sign leptons: • Electron leading pT>12GeV, others pT>6GeV • Muon leading pT>18GeV, others pT>12GeV
• Z-veto
) [GeV]±e±m(e
0 100 200 300 400 500 600
Elec
tron
pairs
/ 20
GeV
-110
1
10
210
310Data 2012PromptCharge misidγW
Non-prompt 300 GeV±±LH 500 GeV±±LH
ATLAS-1 = 8 TeV, 20.3 fbs
±e±e
) [GeV]±µ±m(e
0 100 200 300 400 500 600
Lept
on p
airs
/ 20
GeV
-110
1
10
210
310 Data 2012PromptCharge misidγW
Non-prompt 300 GeV±±LH 500 GeV±±LH
ATLAS-1 = 8 TeV, 20.3 fbs
±µ±e
) [GeV]±µ±µm(0 100 200 300 400 500 600
Muo
n pa
irs /
20 G
eV
-110
1
10
210
Data 2012PromptNon-prompt
300 GeV±±LH 500 GeV±±LH
ATLAS-1 = 8 TeV, 20.3 fbs
±µ±µ
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Same-sign dilepton (2) § Fiducial cross section limits
01/12/2014 Kruger 2014, K. Hamano 16
) [GeV]±e±m(e>15 >100 >200 >300 >400 >500 >600
) [fb
]±
e±
e→
(pp
95fidσ
-110
1
10
210 ObservedMedian expected
σ 1±Expected σ 2±Expected
ATLAS Internal-1 = 8 TeV, 20.3 fbs
±e±e
) [GeV]±µ±m(e>15 >100 >200 >300 >400 >500 >600
) [fb
]±µ
± e
→(p
p 95fid
σ
-110
1
10
210 ObservedMedian expected
σ 1±Expected σ 2±Expected
ATLAS Internal-1 = 8 TeV, 20.3 fbs
±µ±e
) [GeV]±µ±µm(>15 >100 >200 >300 >400 >500 >600
) [fb
]±µ
±µ
→(p
p 95fid
σ
-110
1
10
210 ObservedMedian expected
σ 1±Expected σ 2±Expected
ATLAS Internal-1 = 8 TeV, 20.3 fbs
±µ±µ
Doubly-charged Higgs mass limits: 95% CL lower limit [GeV]
e±e± e±µ± µ±µ±
Signal Expected Observed Expected Observed Expected Observed
H±±L 553± 30 551 487± 41 468 543± 40 516
H±±R 425± 30 374 396± 34 402 435± 33 438
Table 9: Lower limits at 95% CL on the mass of H±±L and H±±R bosons, assuming a 100%
branching ratio to e±e±, e±µ± and µ±µ± pairs. The 1σ variations are also shown for the
expected limits.
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3 or more charged leptons (arXiv:1411.2921)
§ Event selection
§ This is a generic search and include multiple Signal Regions depending on § On-Z, Off-Z § MET = missing transverse energy § HT = scalar sum of pT § meff = scalar sum of missing ET, jet HT and lepton pT
01/12/2014 Kruger 2014, K. Hamano 17
• 3 or more isolated leptons • Leading lepton: electron or muon with pT>26GeV • Second lepton: electron or muon with pT>15GeV • Third lepton: electron or muon with pT>15GeV or tau with pT>20GeV
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3 or more leptons (2) § Cross section limits in various signal regions:
01/12/2014 Kruger 2014, K. Hamano 18
All 200≥ 500≥ 800≥ 50≥ 100≥ 150≥ 1≥ 2≥ 600≥ 1000≥ 1500≥ 0≥ 600≥ 1200≥ 0≥ 600≥ 1200≥ 0≥ 100≥ 200≥ 300≥ 0≥ 100≥ 200≥ 300≥
-10
1µ3 e/
All 200≥ 500≥ 800≥ 50≥ 100≥ 150≥ 1≥ 2≥ 600≥ 1000≥ 1500≥ 0≥ 600≥ 1200≥ 0≥ 600≥ 1200≥ 0≥ 100≥ 200≥ 300≥ 0≥ 100≥ 200≥ 300≥
-10
1τ + µ2 e/
All 200≥ 500≥ 800≥ 50≥ 100≥ 150≥ 1≥ 2≥ 600≥ 1000≥ 1500≥ 0≥ 600≥ 1200≥ 0≥ 600≥ 1200≥ 0≥ 100≥ 200≥ 300≥ 0≥ 100≥ 200≥ 300≥
-10
1µ3 e/
All 200≥ 500≥ 800≥ 50≥ 100≥ 150≥ 1≥ 2≥ 600≥ 1000≥ 1500≥ 0≥ 600≥ 1200≥ 0≥ 600≥ 1200≥ 0≥ 100≥ 200≥ 300≥ 0≥ 100≥ 200≥ 300≥
-101
10 τ + µ2 e/
All 200≥ 500≥ 800≥ 50≥ 100≥ 150≥ 1≥ 2≥ 600≥ 1000≥ 1500≥ 0≥ 600≥ 1200≥ 0≥ 600≥ 1200≥ 0≥ 100≥ 200≥ 300≥ 0≥ 100≥ 200≥ 300≥
-101
10 µ3 e/
All 200≥ 500≥ 800≥ 50≥ 100≥ 150≥ 1≥ 2≥ 600≥ 1000≥ 1500≥ 0≥ 600≥ 1200≥ 0≥ 600≥ 1200≥ 0≥ 100≥ 200≥ 300≥ 0≥ 100≥ 200≥ 300≥
-101
1020 τ + µ2 e/
(95%
CL
Upp
er L
imit)
[fb]
vis
95σ
Off-Z,no-O
SSFO
ff-Z,OSSF
On-Z
[GeV]leptonsTH [GeV]lepT
Min. p b-tags [GeV]effm [GeV]effm [GeV]effm [GeV]missTE [GeV]
missTE
Inclusive >100 GeVmissTE >100 GeVWTm 150 GeV≥jetsTH
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3 or more leptons (3) § Doubly-charged Higgs in tau decay mode:
01/12/2014 Kruger 2014, K. Hamano 19
mass [GeV]±±H100 200 300 400 500 600
BR [f
b]×
σ
-110
1
10
210
310ATLAS
= 8 TeVs-1Ldt = 20.3 fb∫
±τ±e→L±±H
±τ±e→R±±H
95% CL Upper LimitsObservedMedian Exp.
σ 1±σ 2±
mass [GeV]±±H100 200 300 400 500 600
BR [f
b]×
σ
-110
1
10
210
310ATLAS
= 8 TeVs-1Ldt = 20.3 fb∫
±τ±µ→L±±H
±τ±µ→R±±H
95% CL Upper LimitsObservedMedian Exp.
σ 1±σ 2±
Mass limit : HL++ > 400 GeV
e tau µ tau
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Lepton + X § Lepton + X general search (ATLAS-CONF-2014-006)
§ Events with isolated electrons, photons, muons, jets. § Lepton + MET (neutrino) (arXiv:1407.7494, JHEP09(2014)037)
§ Heavy gauge boson W’, Exited boson W*. § Lepton + jet
§ Scalar Leptoquarks: § 1st generation (arXiv:1112.4828, PLB709(2012)158-176) § 2nd generation (arXiv:1203.3172, EPJ C72(2012)2151) § 3rd generation (arXiv:1303.0526, JHEP06(2013)033)
§ Microscopic Black Holes (arXiv:1405.4254, JHEP08(2014)103) § Quantum Black Holes (arXiv:1311.2006, PRL112,091804(2014)) § Excited Leptons (arXiv:1308.1364, NJP15(2013)093011)
01/12/2014 Kruger 2014, K. Hamano 20
More details on Blue analysis
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L + Missing energy (arXiv:1407.7494, JHEP09(2014)037)
§ W’ and W* à l + v
01/12/2014 Kruger 2014, K. Hamano 21
[GeV]W’ m500 1000 1500 2000 2500 3000 3500 4000
B [f
b]σ
-110
1
10
210
310NNLO theoryObserved limitExpected limit
σ 1±Expected σ 2±Expected
= 8 TeV,s ∫ -1 = 8 TeV, Ldt = 20.3 fbsν l →W’
95% CL
ATLAS
[GeV]missT E
210 310
Eve
nts
1
10
210
310
410
510
610Data 2012W’(0.5 TeV)W’(1 TeV)W’(3 TeV)WZTop quarkDibosonMultijet
ATLAS ν e→W’ = 8 TeVs
-1 L dt = 20.3 fb∫
[GeV]missT E210 310
Dat
a/Bk
g
00.5
11.5
2
[GeV]missT E
210 310
Eve
nts
110
210
310
410
510
610
710
810Data 2012W’(0.5 TeV)W’(1 TeV)W’(3 TeV)WZTop quarkDibosonMultijet
ATLAS νµ →W’ = 8 TeVs
-1 L dt = 20.3 fb∫
[GeV]missT E210 310
Dat
a/Bk
g
00.5
11.5
2
ev
µv
Missing energy
Table 10. Observed upper limits on σB for W ′ and W ∗ with masses above 2000 GeV. Thecolumns are the same as in table 9.
mW ′/W∗ [GeV] Channel 95% CL limit on σB [fb]W ′ W ∗
none S SB SBL SBc SBcL none SBcL
2250eν 0.453 0.455 0.455 0.456 0.458 0.459 0.830 0.859µν 0.853 0.859 0.859 0.862 0.866 0.869 0.726 0.734both 0.296 0.297 0.297 0.298 0.301 0.303 0.457 0.488
2500eν 0.564 0.569 0.569 0.570 0.572 0.573 0.438 0.441µν 1.06 1.07 1.07 1.08 1.08 1.08 0.828 0.837both 0.368 0.370 0.370 0.371 0.376 0.377 0.287 0.289
2750eν 0.629 0.643 0.643 0.644 0.648 0.649 0.459 0.462µν 1.16 1.19 1.19 1.20 1.21 1.21 0.917 0.928both 0.409 0.413 0.413 0.414 0.425 0.426 0.306 0.308
3000eν 0.809 0.852 0.852 0.853 0.863 0.865 0.387 0.389µν 1.47 1.55 1.55 1.56 1.58 1.58 0.798 0.807both 0.523 0.534 0.534 0.536 0.566 0.567 0.261 0.263
3250eν 1.20 1.37 1.37 1.37 1.40 1.40 0.338 0.340µν 2.14 2.45 2.45 2.45 2.52 2.52 0.678 0.687both 0.768 0.815 0.815 0.816 0.919 0.920 0.226 0.228
3500eν 1.92 2.56 2.56 2.56 2.64 2.64 0.312 0.315µν 3.37 4.38 4.38 4.39 4.56 4.57 0.645 0.655both 1.22 1.38 1.38 1.38 1.72 1.73 0.210 0.213
3750eν 3.12 4.90 4.90 4.90 5.07 5.08 0.297 0.307µν 5.32 7.85 7.85 7.86 8.22 8.24 0.605 0.630both 1.97 2.37 2.37 2.38 3.26 3.27 0.199 0.208
4000eν 4.76 8.07 8.07 8.09 8.38 8.40 0.304 0.372µν 7.75 12.0 12.0 12.0 12.6 12.6 0.613 0.749both 2.95 3.66 3.66 3.66 5.24 5.24 0.203 0.255
Table 11. Lower limits on the W ′ and W ∗ masses. The first column is the decay channel (eν, µνor both combined) and the following give the expected (Exp.) and observed (Obs.) mass limits.
mW ′ [TeV] mW ∗ [TeV]Decay Exp. Obs. Exp. Obs.eν 3.13 3.13 3.08 3.08µν 2.97 2.97 2.83 2.83Both 3.17 3.24 3.12 3.21
– 18 –
Mass limits
• One isolated electron with ET>125GeV + MET>125GeV
• Or one muon with pT>45GeV + MET>45GeV
• No additional lepton with pT>20GeV
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Dijets/Multi jets § Dijet resonance (arXiv:1407.1376, PRD)
§ Excited quarks, Color octet scalars, Heavy and excited W bosons, Quantum black holes,
§ Multi jets § Resonant Higgs Pair Production (ATLAS-CONF-2014-005)
§ X à HH à bbbb § Two Higgs doublet models, KK graviton
§ Photon + jet (arXiv:1309.3230, PLB728,562(2013)) § Quantum Black Holes, Excited quarks
§ Dark matter search: § “Searches for Dark Matter with the ATLAS
Detector” (Ketevi Assamagan).
01/12/2014 Kruger 2014, K. Hamano 22
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DataFit
*, m = 0.6 TeVq*, m = 2.0 TeVq*, m = 3.5 TeVq
9
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BR
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=8 TeVs-1L dt = 20.3 fb∫
BW/mBWΓ PDFgg
0.050.030.010.005
Figure 9. The 95% CL upper limits on � ⇥ A for a Breit–Wigner narrow resonance produced by a gg initial state de-caying to dijets and convolved with PDF e↵ects, dijet massacceptance and detector resolution as a function of the meanmass, mBW, for di↵erent values of intrinsic width over mass(�BW/mBW), taking into account both the statistical and sys-tematic uncertainties.
[TeV]BWm1 2 3 4
BR
[pb]
× A × σ
-410
-310
-210
-110
1
10
210
310
ATLAS
=8 TeVs-1L dt = 20.3 fb∫
BW/mBWΓ PDFqq
0.050.030.010.005
Figure 10. The 95% CL upper limits on � ⇥ A for a Breit–Wigner narrow resonance produced by a qq̄ initial state de-caying to dijets and convolved with PDF e↵ects, dijet massacceptance and detector resolution as a function of the meanmass, mBW, for di↵erent values of intrinsic width over mass(�BW/mBW), taking into account both the statistical and sys-tematic uncertainties.
masses. The data sample used in the current analysisconsists of 20.3 fb�1 of pp collision data at
ps = 8 TeV,
and the resulting dijet mass distribution extends from250 GeV to approximately 4.5 TeV.No resonance-like features are observed in the dijet
mass spectrum. This analysis places limits on the crosssection times acceptance at the 95% credibility level onthe mass or energy scale of a variety of hypotheses forphysics phenomena beyond the Standard Model.To illustrate the typical increases in sensitivity to new
phenomena at the LHC up to the end of 2012 running,Table II shows the history of expected limits from AT-LAS studies using dijet resonance analysis of two bench-mark models, excited quarks and color-octet scalars. Thelimits set by this analysis on excited quarks, color-octetscalars, heavy W 0 bosons, chiral W ⇤ bosons, and quan-tum black holes, are summarized in Table I.
Model and Final State 95% CL Limits [TeV]Expected Observed
q⇤ ! qg 3.99 4.09s8 ! gg 2.83 2.72W 0 ! qq̄0 2.51 2.45Leptophobic W ⇤ ! qq̄0 1.93 1.75Leptophilic W ⇤ ! qq̄0 1.67 1.66Qbh black holes 5.82 5.82(q and g decays only)BlackMax black holes 5.75 5.75(all decays)
Table I. The 95% CL lower limits on the masses and energyscales of the models examined in this study. All limit analy-ses are Bayesian, with statistical and systematic uncertaintiesincluded.
ps L Citation q⇤ [TeV] s8 [TeV]
7 TeV 36 pb�1 [11] 2.07 -7 TeV 1.0 fb�1 [12] 2.81 1.777 TeV 4.8 fb�1 [13] 2.94 1.978 TeV 20.3 fb�1 current 3.99 2.83
Table II. ATLAS previous and current expected 95% CL up-per limits [TeV] on excited quarks and color-octet scalars.
ACKNOWLEDGMENTS
We thank CERN for the very successful operation ofthe LHC, as well as the support sta↵ from our institutionswithout whom ATLAS could not be operated e�ciently.We acknowledge the support of ANPCyT, Argentina;
YerPhI, Armenia; ARC, Australia; BMWF and FWF,Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPqand FAPESP, Brazil; NSERC, NRC and CFI, Canada;CERN; CONICYT, Chile; CAS, MOST and NSFC,China; COLCIENCIAS, Colombia; MSMT CR, MPOCR and VSC CR, Czech Republic; DNRF, DNSRCand Lundbeck Foundation, Denmark; EPLANET, ERC
Mass limits [TeV]*qm1 2 3 4 5
[pb]
A × σ
-310
-210
-110
1
10
210
310
ATLAS
*qObserved 95% CL upper limitExpected 95% CL upper limit68% and 95% bands
-1L dt = 20.3 fb∫=8 TeVs
• Two well measured jets with pT>50GeV • mjj > 250GeV
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× A × σ
-410
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1
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ATLAS
=8 TeVs-1L dt = 20.3 fb∫
G/mGσ0.150.100.07Resolution
Gaussian resonance limits B-W narrow resonance limits
[TeV]BWm1 2 3 4
BR
[pb]
× A × σ
-410
-310
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1
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=8 TeVs-1L dt = 20.3 fb∫
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Top quark final states § ttbar resonance (ATLAS-CONF-2013-052)
§ Leptophobic topcolor Z’, Kaluza-Klein gluons § Same-sign top etc. (ATLAS-CONF-2013-051)
§ 4th generation down-type chiral quarks (b’), Vector Like Quarks, Composite top partners (T5/3), Same-sign top pairs, Contact interactions.
§ Vector Like Quarks (VLQ) § Little Higgs, Composite Higgs. § VLQ à H + t (ATLAS-CONF-2013-018) § VLQ à W + b (ATLAS-CONF-2013-060) § VLQ à Z + t/b (arXiv:1409.5500, JHEP)
§ W’ à t b: § l + jets final states (arXiv:1410.4103, PLB) § qqbb final states (arXiv:1408.0889, EPJC)
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810 Data Z’ (1.5 TeV)×5 tt (2.0 TeV)KK g×5
Multi-jets W+jetsOther Backgrounds
0 0.5 1 1.5 2 2.5 3 3.5
ATLAS Preliminary
= 8 TeVs
-1 L dt = 14.2 fb∫
[TeV]recottm
Dat
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1.5
0 0.5 1 1.5 2 2.5 3 3.5
Z’ mass [TeV]0.5 1 1.5 2 2.5 3
) [pb
]t t
→ B
R(Z
’×
Z’σ
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310Obs. 95% CL upper limitExp. 95% CL upper limit
uncertaintyσExp. 1 uncertaintyσExp. 2
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Obs. 95% CL upper limitExp. 95% CL upper limit
uncertaintyσExp. 1 uncertaintyσExp. 2
Leptophobic Z’ (LO x 1.3)
ATLAS Preliminary
-1 = 14.3 fbdt L ∫
= 8 TeVs
mass [TeV]KK
g0.5 1 1.5 2 2.5
) [pb
]t t
→KK
BR
(g×
KKgσ
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310Obs. 95% CL upper limitExp. 95% CL upper limit
uncertaintyσExp. 1 uncertaintyσExp. 2
Kaluza-Klein gluon (LO)
Obs. 95% CL upper limitExp. 95% CL upper limit
uncertaintyσExp. 1 uncertaintyσExp. 2
Kaluza-Klein gluon (LO)ATLAS Preliminary
-1 = 14.3 fbdt L ∫
= 8 TeVs
Topcolor Z’ mass < 1.9 TeV
KK gluon mass < 2.1 TeV
• Isolated lepton (pT>25GeV) + well defined b-jet
• e+jets: MET>30GeV, mT>30GeV • µ+jets: MET>20GeV, MET+mT>60GeV • Angular distance between l and j
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Z+light jets
Z+bottom jet(s)
tt
Other bkg
(650 GeV)BB
(650 GeV)TT
q (650 GeV)bB
q (650 GeV)bT
Uncertainty
ATLAS
-1 Ldt = 20.3 fb∫
= 8 TeVs
Dilepton
2 b-tags≥ 1 fwd jet≥
m(Zb) [GeV]
0 200 400 600 800 1000 1200 1400
Da
ta /
bkg
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(jets+leptons) [GeV]TH0 400 800 1200 1600 2000
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0.2
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1.4
1.6DataOther bkg.WZ
+Vtt (650 GeV)BB (650 GeV)TTq (650 GeV)bT
Uncertainty
ATLAS=8 TeVs
-1 L dt = 20.3 fb∫
1 b-tag≥ 1 fwd jet≥
Trilepton
• Isolated electrons and muons • Well defined b-jet • Z candidate: opposite-charge,
same –flavor leptons with |m(ll) – m(Z)| < 10GeV
Event selectionZ boson candidate preselection
� 2 central jetspT
(Z) � 150 GeVDilepton channel Trilepton channel
= 2 leptons � 3 leptons� 2 b-tagged jets � 1 b-tagged jet
Pair production Single production Pair production Single productionH
T
(jets) � 600 GeV � 1 fwd. jet – � 1 fwd. jetFinal discriminant
m(Zb) HT
(jets+leptons)
Table 1. Summary of the event selection criteria. Preselected Z boson candidate events aredivided into dilepton and trilepton categories. The requirements on the number of central jetsand the Z candidate transverse momentum are common to both channels, and for the pair- andsingle-production hypotheses. Other requirements are specific to a lepton channel or the targetedproduction mechanism. The last row lists the final discriminant used for hypothesis testing.
after selecting events with a Z boson candidate and at least two central jets. The shapes ofthe signal and background distributions motivate separate criteria for events with exactlytwo leptons, and those with three or more, with the strategy for the former focused onbackground rejection, and the strategy for the latter focused on maintaining signal efficiency.The only signal hypothesis not expected to produce events with a third isolated lepton isthe B(! Zb)¯bq process. The other three processes are capable of producing, in additionto the Z boson, a W boson that decays to leptons. The W boson could arise from a topquark decay, or directly from the other heavy quark decay in the case of the pair-productionsignal.
At least two central jets are required in both lepton channels, and when testing bothproduction mechanism hypotheses. The requirement is over 95% efficient for the pair-production signals, and over 70% efficient for the single-production signals, while sup-pressing the backgrounds by a factor of 20 and 5 in the dilepton and trilepton channels,respectively. A second common requirement is on the minimum transverse momentum ofthe Z boson candidate: p
T
(Z) > 150 GeV. Figure 4(b) presents the pT
(Z) distribution insignal and background dilepton channel events after the Z+ � 2 central jets selection.
Figure 4(c) presents the b-tagged jet multiplicity distribution, also after the Z+ � 2central jets selection in the dilepton channel. Pair-production signal events are expected toyield at least two b-jets, whether produced directly from a heavy quark decay, the decayof a top quark, or the decay of a Higgs boson. Single-production signal events also yieldtwo b-jets, but the one arising from the b-quark produced in association is less often in theacceptance for b-tagging. In order to effectively suppress the large Z + jets background,dilepton channel events are required to contain at least two b-tagged jets when testing boththe single- and pair-production hypotheses. A requirement of at least one b-tagged jet
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[GeV]Bm400 500 600 700 800 900 1000 1100 1200
Zb)
[pb]
→ B
R(B
×q)
bB
→(p
pσ
-210
-110
1
10
210
ATLAS
-1 Ldt = 20.3 fb∫
=8 TeVs
95% CL expected limit
σ1±95% CL expected limit
σ2±95% CL expected limit
95% CL observed limit
400 500 600 700 800 900 1000 1100-210
-110
1
10
210
[GeV]Tm
Zt)
[pb]
→ B
R(T
×q)
b T
→(p
p
σ
ATLAS
-1Ldt = 20.3 fb∫
= 8 TeVs
95% CL expected limit
σ1±95% CL expected limit
σ2±95% CL expected limit
95% CL observed limit
Singlet mass limit [GeV] Doublet mass limit [GeV]Hypothesis Dilepton Trilepton Comb. Dilepton Trilepton Comb.
B ¯B 690 (665) 610 (610) 685 (670) 765 (750) 540 (530) 755 (755)T ¯T 620 (585) 620 (620) 655 (625) 705 (665) 700 (700) 735 (720)
Table 8. Observed (expected) 95% CL limits on the T and B quark mass (GeV) assuming pairproduction of SU(2) singlet and doublet quarks, and using the dilepton and trilepton channelsseparately, as well as combined.
For the pair-production hypotheses, the final discriminating variable in the dileptonchannel is the m(Zb) distribution shown in figure 7(d), while the final discriminating vari-able in the trilepton channel is the H
T
(jets + leptons) distribution shown in figure 9(b). Forthe single-production hypotheses, the final discriminating variable in the dilepton channelis the m(Zb) distribution shown in figure 10(d), while the final discriminating variable inthe trilepton channel is the H
T
(jets + leptons) distribution shown in figure 11(b).The data are found to be consistent with the background-only hypotheses in each
of the four final distributions, and limits are subsequently derived according to the CLs
prescription [70, 71]. Upper limits at the 95% confidence level (CL) are set on the pair- andsingle-production cross sections of vector-like T and B quarks. The cross-section limits arethen used to set lower limits on the quark masses, as well as upper limits on electroweakcoupling parameters.
10.1 Limits on the pair-production hypotheses
Figures 12(a,b) show the pair-production cross-section limit for B quark masses in theinterval 350–850 GeV, assuming the branching ratios of an SU(2) singlet B quark and aB quark in a (B, Y ) doublet, respectively. The theoretical curve represents the total pair-production cross section calculated with Top++, and the width of the curve indicatesthe uncertainty on the prediction from PDF+↵
s
and scale uncertainties. The observed(expected) limit on the mass of an SU(2) singlet B quark is 685 GeV (670 GeV), whilethe observed (expected) limit on the mass of a B quark in a (B, Y ) doublet is 755 GeV(755 GeV). These limits are derived by combining the dilepton and trilepton channels in asingle likelihood function. Table 8 lists the combined B quark mass limits along with themass limits obtained from the dilepton and trilepton channels independently. The dileptonchannel provides the greater degree of sensitivity for both the singlet and doublet B quarkhypotheses.
Figures 12(c,d) show the pair-production cross-section limit for T quark masses in theinterval 350–850 GeV, assuming the branching ratios of an SU(2) singlet T quark and a Tquark in a (T, B) doublet, respectively. The observed (expected) limit on the mass of anSU(2) singlet T quark is 655 GeV (625 GeV), while the observed (expected) limit on themass of a T quark in a (T, B) doublet is 735 GeV (720 GeV). These limits are derived bycombining the dilepton and trilepton channels in a single likelihood function. Table 8 liststhe combined T quark mass limits along with the mass limits obtained from the dilepton
– 26 –
Single production cross section limits:
Pair production mass limits:
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Data5×(1.75 TeV)RW'
TopW+jetsZ+jets, dibosonsMultijetsUncertainty
Even
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eV
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[GeV]btm400 600 800 1000 1200 1400 1600 1800 2000D
ata/
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.
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2 mass [TeV]LW'
0.5 1 1.5 2 2.5 3
) [pb
]b t
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W'
×) LW
'→
(pp
σ
-210
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TheoryExpected limitObserved limit
σ 1 ±σ 2 ±
WL’ > 1.70 TeV
• Isolated leptons with pT>30GeV • Well measured jets with pT>25GeV
• W’ à t bbar à W(lv)b bbar
• 1 lepton + 2 b-jets (+ jet) • MET>35GeV • mT(W)+MET>70GeV
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§ GUT, Little Higgs, Technicolor, Composite Higgs, Extra dimensions.
§ WZ à lvll (full leptonic) (arXiv:1406.4456, PLB737,223(2014)) § ZZ/ZW à lljj (arXiv:1409.6190, EPJC) § Wγ and Zγ (arXiv:1407.8150, PLB738,428(2014)) § WH/ZH à Wjj/Zjj (ATLAS-CONF-2013-074)
§ Heavy lepton search § Heavy neutrino à Wv (ATLAS-CONF-2012-139)
§ Left-right symmetric model § Heavy lepton à Zl (ATLAS-CONF-2013-019)
§ Type III seesaw model
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310ATLAS
-1Ldt=20.3 fb∫=8 TeV, s
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Data W’(600 GeV)
WZ W’(1000 GeV)
Other bkg W’(1400 GeV)
stat.+syst.σ
[GeV]WZm200 400 600 800 1000 1200 1400 1600 1800
Dat
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[GeV]m200 400 600 800 1000 1200 1400 1600 1800 2000
WZ)
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pσ
-210
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210 Expected 95% CL Limitσ 1±95% CL σ 2±95% CL
Observed LimitEGM W’HVT A(gv=1) HVT A(gv=3) HVT B(gv=3)
ATLAS-1Ldt = 20.3 fb∫=8 TeV, s
CLs, defined as the ratio CLs+b/CLb, is equal to 0.05. For themass points above 400 GeV, only the high-mass signal region isused in the calculation by statistically combining all lepton de-cay channels. For the mass points below or equal to 400 GeV,the two signal regions are further combined to maximize thesensitivity of the search.Fig. 5 presents the 95% CL upper limits on σ(pp → X) ×
B(X → WZ) as a function of the signal resonance mass, whereX stands for the signal resonance, together with the theoreti-cal cross sections of the EGM W′ and HVT benchmark mod-els. The latter cross sections are calculated via the web in-terface [55] provided by the authors of Ref. [20]. The exclu-sion region in parameter space {(g2/gV)cF , gVcH} is shown inFig. 6. The fermion coupling cF was set to the same valuefor quarks and leptons. The couplings cVVV , cVVHH and cVVW ,which involve vertices with more than one heavy vector bosonand which have negligible effect on the cross section, were setto zero. Table 4 presents the expected and observed limits fora selected set of signal mass points as well as the EGM W′signal acceptance A and correction factor C. The acceptanceA is defined as the number of generated events found withinthe fiducial region at particle level divided by the total numberof generated events, while C is defined as the number of re-constructed events passing the nominal selection requirementsdivided by the number of generated events within the fiducialregion at particle level. The fiducial region selection criteriaconsist of the same kinematic selections (lepton pT, lepton η,Z boson mass, EmissT , ∆y(W, Z) and ∆φ(ℓ, E
missT )) and lepton iso-
lation requirements as in the nominal selections. Particle levelrefers to particle states that stem from the hard scatter, includ-ing those that are the product of hadronization, but before theirinteraction with the detector. Table 5 presents the 95% CL ex-pected and observed lower limits on the EGM W′ boson massfor each decay channel and their combination. The observed(expected) exclusion limit on the EGM W′ mass is found tobe 1.52 (1.49) TeV, and the limits in each channel are shownin Table 5. The simulated HVT resonances are found to havekinematic distributions similar to those of theW′ and thus havesimilar acceptances to the EGM model. The corresponding ob-served (expected) limits for the A(gV = 1), A(gV = 3), andB(gV = 3) HVT resonances from Ref. [20] are 1.49 (1.45) TeV,0.76 (0.69) TeV, and 1.56 (1.53) TeV respectively. In Fig. 5, theHVT benchmarkmodel curves are not shown for low resonancemass where the models do not apply.
Table 5: Expected and observed lower mass limits at 95% CL in TeV for theEGM W′ boson in the eνee, eνµµ, µνee, µνµµ channels as well as the fourchannels combined.
Excluded EGMW′ lower mass [TeV]eνee µνee eνµµ µνµµ combined
Expected 1.21 1.16 1.17 1.16 1.49Observed 1.20 1.19 1.06 1.17 1.52
[GeV]m200 400 600 800 1000 1200 1400 1600 1800 2000
WZ)
[pb]
→ B
(X×
X)
→ (p
pσ
-210
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Observed LimitEGM W’HVT A(gv=1) HVT A(gv=3) HVT B(gv=3)
ATLAS-1Ldt = 20.3 fb∫=8 TeV, s
Fig. 5: The observed 95% CL upper limits on σ(pp → X) × B(X → WZ)as a function of the signal mass m, where X stands for the signal resonance.The expected limits are also shown together with the ±1 and ±2 standard devi-ation uncertainty bands. Both the expected and observed upper limits assumethe EGM W′ signal acceptance times efficiency as presented in Table 4. The-oretical cross sections for the EGM W′ and the HVT benchmark models arealso shown. The uncertainty band around the EGM W′ cross-section line rep-resents the theoretical uncertainty on the NNLO cross-section calculation usingZWPROD [30].
H cVg-3 -2 -1 0 1 2 3
F) c V
/g2(g
-1
-0.5
0
0.5
1 ATLAS-1 L dt = 20.3 fb∫ = 8 TeV, s
=1V
gA
=3V
gA
=3V
gB1 TeV
1.5 TeV
2 TeV
Fig. 6: Observed 95% CL exclusion contours in the HVT parameter space{(g2/gV )cF , gVcH } for resonances of mass 1 TeV, 1.5 TeV and 2 TeV. Alsoshown are the benchmark model parameters A(gV=1) (circle) and A(gV=3)(square) and B(gV=3) (triangle).
8
Extended Gauge Model W’ mass limits
• Exactly 3 isolated leptons with pT>25GeV • MET>25GeV • Z candidate: opposite-charge same-flavor leptons with |m(ll) – m(Z)| < 20GeV
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ZZ/ZWàllqq (arXiv:1409.6190, EPJC)
01/12/2014 Kruger 2014, K. Hamano 32
Even
ts /
GeV
-410
-310
-210
-1101
10
210
310
410
510 DataZ+jetsZZ/ZW/WW
+Single TopttSys+Stat UncertaintyG*, m=500 GeV
10.0× Nominalσ
ATLAS = 8 TeVs
-1L dt = 20.3 fb∫ Res. Region
TLow-p
Channelµµ ee, →Z
[GeV]lljjm0 500 1000 1500 2000 2500
Dat
a / B
G
0.60.8
11.21.4
[GeV]G*m400 600 800 1000 1200 1400 1600 1800 2000
ZZ)
[pb
]→
BR
(G*
× G
*)
→(p
p σ
-310
-210
-110
1
10
210ATLAS
= 8 TeVs-1L dt = 20.3 fb∫
= 1PlMBulk RS graviton k/ = 0.5PlMBulk RS graviton k/
Expected 95% CLObserved 95% CL
uncertaintyσ 1 ± uncertaintyσ 2 ±
[GeV]W’m400 600 800 1000 1200 1400 1600 1800 2000
ZW
) [p
b]→
BR
(W’
× W
’) →
(pp
σ
-310
-210
-110
1
10
210ATLAS
= 8 TeVs-1L dt = 20.3 fb∫
EGM W’, c = 1Expected 95% CLObserved 95% CL
uncertaintyσ 1 ± uncertaintyσ 2 ±
EGM W’ mass > 1590 GeV
Bulk RS G* mass > 740 GeV
• Extended Gauge Model W’ à WZ
• KK Graviton G* à ZZ • Exactly two isolated oppsite-charge,
same-flavor leptons with 66GeV < |m(ll) – m(Z)| < 116GeV • qq side: two well measured jets or
one large-R jet. Mass agrees with Z or W.
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ewed
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Other Signatures § Exotic charges
§ Highly ionizing particles (arXiv:1207.6411, PRL109(2012)261803) § Magnetic monopoles
§ Long Lived Particles (LLP) § LLP decays away from the pp interaction point. § Look for displaced decay point (vertex). § Special trigger is required. § Displaced lepton-jets (LJ):
§ H à dark photon (arXiv:1409.0746, JHEP) § Displaced jets:
§ Heavy scalar à Hidden Valley LLP pair (ATLAS-CONF-2014-041)
§ BSM Higgs specific searches: § “Beyond the Standard Model Higgs Physics Using the
ATLAS Detector” (Guillermo Hamity). 01/12/2014 Kruger 2014, K. Hamano 33
More details on Blue analysis
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ewed
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inte
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circ
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Other Signatures § Exotic charges
§ Highly ionizing particles (arXiv:1207.6411, PRL109(2012)261803) § Magnetic monopoles
§ Long Lived Particles (LLP) § LLP decays away from the pp interaction point. § Look for displaced decay point (vertex). § Special trigger is required. § Displaced lepton-jets (LJ):
§ H à dark photon (arXiv:1409.0746, JHEP) § Displaced jets:
§ Heavy scalar à Hidden Valley LLP pair (ATLAS-CONF-2014-041)
§ BSM Higgs specific searches: § “Beyond the Standard Model Higgs Physics Using the
ATLAS Detector” (Guillermo Hamity). 01/12/2014 Kruger 2014, K. Hamano 34
More details on Blue analysis
Not
revi
ewed
,for
inte
rnal
circ
ulat
ion
only
LLP à lepton-jets (arXiv:1409.0746, JHEP) § pp à 2(4) dark photons à 2(4) lepton-jets (LJ) § Dark photons decay in the calorimeter.
01/12/2014 Kruger 2014, K. Hamano 35
Cone%of%opening%angle%ΔR%
J%%TYPE0%L%
Cone%of%opening%angle%ΔR%
J%%TYPE1%L%
Cone%of%opening%angle%ΔR%
ID#EMCAL#HCAL#MS#
J%%TYPE2%L%
• LJ signature: • µµ: two muons in the muon detector and no near-by jets. • ee: one jet in the calorimeter. • No matching tracks in the inner tracker. • Type0 (muons),Type1 (muons and jets), Type2 (jets)
• Two LJs with back-to-back (large angular separation)
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LLP à lepton-jets (2)
01/12/2014 Kruger 2014, K. Hamano 36
[mm]τDark photon c1 10 210 310
) [pb
]X+ dγ
2→
HBR
(×σ
95%
CL
Lim
it on
1
10
210ATLAS
= 8 TeVs -120.3 fb
modeldγFRVZ 2
σ 2±expected σ 1±expected
observed limitexpected limit
) = 100%X+dγ 2→HBR(
) = 10%X+dγ 2→HBR(
= 400 MeVdγm
[mm]τDark photon c1 10 210 310
) [pb
]X+ dγ
4→
HBR
(×σ
95%
CL
Lim
it on
1
10
210ATLAS
= 8 TeVs -120.3 fb
modeldγFRVZ 4
σ 2±expected σ 1±expected
observed limitexpected limit
) = 100%X+dγ 4→HBR(
) = 10%X+dγ 4→HBR(
= 400 MeVdγm
FRVZ model Excluded c⌧ [mm]BR(10%)
H ! 2�d + X 14 c⌧ 140H ! 4�d + X 15 c⌧ 260
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Conclusions § Signature based search was done to look for
physics Beyond the Standard Model (BSM). § Recent results with 2012, 8TeV data are
presented. § No significant deviation from the Standard
Model. § Limits are set for new physics models/particles. § Please see other talks for BSM Higgs, Dark
Matter and SUSY.
01/12/2014 Kruger 2014, K. Hamano 37
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§ Overview
01/12/2014 Kruger 2014, K. Hamano 38
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W’ à tb (qqbb) (arXiv:1408.0886, EPJC) § W’ à t bbar à W(qq)b bbar
01/12/2014 Kruger 2014, K. Hamano 39
[GeV]W'm1500 2000 2500 3000
tb) [
pb]
→ W
') x
BR(W
'→
(pp
σ
-210
-110
1
1095% CL limit
observedexpected
σ 1 ±σ 2 ±
signal prediction
ATLAS-1 L dt = 20.3 fb∫
= 8 TeVs
LW'
M(W’) > 1.68 TeV [GeV]W'm1600 1800 2000 2200 2400 2600 2800
SMg'
/g
00.20.40.60.8
11.21.4
1.61.8
2
LW'
observedexpected
σ 1 ±
ATLAS-1 L dt = 20.3 fb∫
= 8 TeVs
[GeV]tbm2000 3000 4000 5000
Even
ts /
100
GeV
-110
1
10
210
310
410
510 databackground-only fit
extrapolation to 5 TeV
L1.5 TeV W'
L2.0 TeV W'
L2.5 TeV W'
L3.0 TeV W'
ATLAS-1 L dt = 20.3 fb∫
= 8 TeVs
/#bins = 26.5/292χone b-tag category
[GeV]tbm1500 2000 2500 3000 3500 4000 4500 5000
data
/ fit
0.40.60.8
11.21.41.6
• One large-R jet with pT>350GeV • Large-R jet is widely distributed and
include W(qq) and b. • One b-jet with pT>350GeV • Angular distance between large-R jet
and b-jet > 2.0
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ewed
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Wγ and Zγ (arXiv:1407.8150, PLB738,428(2014)) § Wàlv, Zàll mode
01/12/2014 Kruger 2014, K. Hamano 40
Even
ts /
80 G
eV
-110
1
10
210
310
410
510 Data 2012γ)+νW(e
)+jets-e+Z(e)+jetsνW(e
+jetsγOther Backgrounds
) = 600 GeV x 10T
m(aσ 1 ±Background Fit
ATLAS
= 8 TeVs, -1 L dt = 20.3 fb∫
[GeV]γνeTm200 400 600 800 1000 1200 1400 1600
Sign
ifica
nce
-101
Even
ts /
60 G
eV
-110
1
10
210
310
410
510Data 2012
γ)++µ-µZ(
)+jets+µ-µZ(
Other Backgrounds
) = 500 GeV x 10Tωm(
σ 1 ±Background Fit
= 8 TeVs, -1 L dt = 20.3 fb∫ATLAS
[GeV]γ-µ+µm
200 400 600 800 1000 1200 1400 1600
Sign
ifica
nce
-2-1012
Even
ts /
80 G
eV
-110
1
10
210
310
410
510Data 2012
γ)+νµW()+jets-µ+µZ()+jetsνµW(
+jetsγOther Backgrounds
) = 600 GeV x 10T
m(aσ 1 ±Background Fit
ATLAS
= 8 TeVs, -1 L dt = 20.3 fb∫
[GeV]γνµTm200 400 600 800 1000 1200 1400 1600
Sign
ifica
nce-5
0
5
Even
ts /
60 G
eV
-110
1
10
210
310
410
510Data 2012
γ)++e-Z(e
)+jets+e-Z(e
Other Backgrounds
) = 500 GeV x 10Tωm(
σ 1 ±Background Fit
= 8 TeVs, -1 L dt = 20.3 fb∫ATLAS
[GeV]γ-e+em
200 400 600 800 1000 1200 1400 1600
Sign
ifica
nce
-2-1012
evγ µvγ
eeγ µµγ
lvγ mode: • Lepton pT>25GeV • Photon ET>45GeV • MET>35GeV llγ mode: • 65
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Wγ and Zγ (2)
01/12/2014 Kruger 2014, K. Hamano 41
[GeV]Ta
m400 600 800 1000 1200 1400 1600
) [fb
]γ) ν
W(l
→ B
R(X
×fidσ
-210
-110
1
10
Observed 95% CL upper limitExpected 95% CL upper limit
σ 1 ±Expected σ 2 ±Expected
γ) ν W(l→ Ta
=8 TeVs, -1 L dt = 20.3 fb∫ATLAS
γν l→pp
[GeV]Tω
m200 400 600 800 1000 1200 1400 1600
) [fb
]γ)- l+
Z(l
→ B
R(X
×
fidσ
-210
-110
1
10=8 TeVs, -1 L dt = 20.3 fb∫
ATLAS
γ-l+ l→pp
Observed 95% CL upper limitExpected 95% CL upper limit
σ 1 ±Expected σ 2 ±Expected
γ) -l+ Z(l→ Tω
[GeV]φm200 400 600 800 1000 1200 1400 1600
) [fb
]γ)- l+
Z(l
→ φ B
R(
×fidσ
-310
-210
-110
1
10
=8 TeVs, -1 L dt = 20.3 fb∫ATLAS
γ-l+ l→pp
Observed 95% CL upper limitExpected 95% CL upper limit
σ 1 ±Expected σ 2 ±Expected
, parameter set (a) γ) -l+ Z(l→ φ, parameter set (b)γ) -l+ Z(l→ φ
• Low Scale Technicolor model: • M(aT) > 960 GeV • M(ωT) > 890 GeV
• Singlet scalar resonance: • M(φ) > 1180 GeV
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LLP pair (ATLAS-CONF-2014-041) § Heavy scalar boson (ΦHS) à LLP (πｖ) pair
01/12/2014 Kruger 2014, K. Hamano 42
v proper decay length [m]π
-110 1 10
BR
[pb]
× σ95
% C
L U
pper
Lim
it on
-110
1
10
210
10 GeVvπ
100 GeV - mΦ
m
25 GeVvπ
100 GeV - mΦ
mATLAS Preliminary
BR (100%) = 29.7 pb× σ
BR (10%) = 2.97 pb× σ
-1 L dt = 20.3 fb∫
= 8 TeVs
proper decay length [m]v
π
-110 1 10
BR
[pb]
× σ95
% C
L U
pper
Lim
it on
1
10
210 10 GeV
vπ 140 GeV - mΦ
m
20 GeVvπ
140 GeV - mΦ
m
40 GeVvπ
140 GeV - mΦ
m
ATLAS Preliminary
BR (100%) = 15.4 pb× σ
BR (10%) = 1.54 pb× σ
-1 L dt = 20.3 fb∫
= 8 TeVs
proper decay length [m]v
π
-110 1 10
SMσ / σ
95%
CL
Upp
er L
imit
on
-110
1
10 GeVvπ
126 GeV - mΦ
m
25 GeVvπ
126 GeV - mΦ
m
40 GeVvπ
126 GeV - mΦ
m
10 GeVvπ
126 GeV - mΦ
m
25 GeVvπ
126 GeV - mΦ
m
40 GeVvπ
126 GeV - mΦ
m
10 GeVvπ
126 GeV - mΦ
m
25 GeVvπ
126 GeV - mΦ
m
40 GeVvπ
126 GeV - mΦ
m
ATLAS Preliminary
BR 30%
BR 10%
-1 L dt = 20.3 fb∫
= 8 TeVs
100 GeV
140 GeV
126 GeV
Excluded proper decay length
• LLP candidate: • Narrow jet in hadronic calorimeter • Small energy deposit in EM calorimeter. • No matching track in the inner tracker.
