Searches for new phenomena in leptonic final states using...
Transcript of Searches for new phenomena in leptonic final states using...
Chikuma Kato on behalf of ATLAS collaboration
BLV2017
Cleveland OH USA 15th May 2017
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Searches for new phenomena in leptonic final states
using the ATLAS detector
Introduction • Standard Model (SM) needs extension
– Naturalness, baryon number, dark matter, neutrino mass
• Models with extended gauge groups (left-right symmetric, E6-motivated) predict heavy gauge boson (W'/Z') – W' à lv @ 13 TeV, 36.1 fb-1 [ATLAS-CONF-2017-016] – Z' à ll @ 13 TeV, 36.1 fb-1 [ATLAS-CONF-2017-027]
• Models with extended Higgs sector (MSSM, 2HDM) predict a CP-odd (A) and two CP-even (h, H) and two charged (H±) Higgs bosons – H/A à ττ @ 13 TeV, 13.3 fb-1 [ATLAS-CONF-2016-085] – A à Zh @ 13 TeV, 3.2 fb-1 [ATLAS-CONF-2016-015]
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W' à lv : Overview • Signal
– Sequential Standard Model (SSM) W'SSM à couplings to fermions are identical to SM W
• Selection – eν : 1 electron pT
> 65 GeV, ETmiss > 65 GeV, mT > 130 GeV
– µν : 1 muon pT > 55 GeV, ETmiss > 55 GeV, mT > 110 GeV
• Background – W, top, Z, di-boson, multi-jet, heavy flavor quark, γ+jets
• multi-jet is estimated from data using matrix method • top, di-boson and multi-jet are extrapolated into high mT
• Discriminant – mT = √( 2pTET
miss(1-cosφlv))
3 ν
±lq
q
±W’
W' à lv : mT
• eν (left) and µν (right) • Local significance 2.3 σ at 1.1 TeV in eν • No significant excess
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DataWTop quarkMultijet
*γZ/Diboson
W’ (3 TeV)W’ (4 TeV)W’ (5 TeV)
PreliminaryATLAS
selectionν e→W’
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-1 = 13 TeV, 36.1 fbsDataWTop quark
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W' à lv : Limit
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[TeV]W’m1 2 3 4 5 6
) [pb
]νe
→ B
R(W
’×
W’)
→(p
pσ
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Expected limit
σ 1±Expected
σ 2±Expected
Observed limit
SSMW’
PreliminaryATLAS
ν e→W’ -1 = 13 TeV, 36.1 fbs
95% CL
[TeV]W’m1 2 3 4 5 6
) [pb
]νµ
→ B
R(W
’×
W’)
→(p
pσ
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Expected limit
σ 1±Expected
σ 2±Expected
Observed limit
SSMW’
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νµ →W’ -1 = 13 TeV, 36.1 fbs
95% CL
[TeV]W’m1 2 3 4 5 6
) [pb
]νl
→ B
R(W
’×
W’)
→(p
pσ
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Expected limit
σ 1±Expected
σ 2±Expected
Observed limit
SSMW’
PreliminaryATLAS
ν l→W’ -1 = 13 TeV, 36.1 fbs
95% CL
• eν (left) and µν (right) • Combined (bottom) • Stronger limit in eν because
acceptance and momentum resolution is better in eν
• Lower mass limit for W'SSM : 5.22 TeV
Z' à ll : Overview • Signal
– Generic Z' (1~32% width), Z'SSM and E6-motivated Z'ψ, Z'χ : in this slides
– Minimal Z' and Contact Interaction (CI) : also in the note • Selection
– ee : At least 2 electon ET > 30 GeV, – µµ : At least 2 muon pT > 30 GeV, opposite charge
• Background – Z, top, di-boson, multi-jet, W+jets – Multi-jet and W+jets are estimated from data using matrix method
• Negligible in µµ • Discriminant
– m(ll)
6 -l
+lq
q
Z’Z’
Z' à ll : m(ll)
• ee (left) and µµ (right) • Local significance 2.5 σ at 2.37 TeV • No significant excess
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Top QuarksDibosonMulti-Jet & W+Jets
(3 TeV)χZ’ (4 TeV)χZ’ (5 TeV)χZ’
PreliminaryATLAS-1 = 13 TeV, 36.1 fbs
Dielectron Search Selection
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Dimuon Search Selection
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Z' à ll : Limits
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PreliminaryATLAS
ll→Z’ -1 = 13 TeV, 36.1 fbs
observed limits
• Limit on generic Z' expected (left) and observed (right)
• Limit on Z'SSM and E6-motivated Z'ψ, Z'χ (bottom) – Lower mass limit for Z'SSM :
4.5 TeV
[TeV]Z’M0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
B [p
b]σ
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Observed limitSSMZ’χZ’ψZ’
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ll→Z’
-1 = 13 TeV, 36.1 fbs
H/A à ττ : Overview • Signal
– gluon-gluon fusion (ggH/A) and b-quark associated (bbH/A) – large tanβ à couplings to down type fermions à b-tag category
• Selection – τlepτhad : ET
miss > 150 GeV à high-ETmiss category, 1 lepton pT > 30
GeV, τhad-vis pT > 25 GeV, opposite charge, Δφ(τhad-vis, l) > 2.4, mT(l, ET
miss) < 40 GeV, veto 80 < mvis(e, τhad-vis) < 110 GeV – τhadτhad : τ1 pT > 110 ~ 140 GeV, Δφ(τ1, τ2) > 2.7, τ refers to visible
• Background – Z+jets, W+jets, top (in b-tag category), di-boson, multi-jet – Fake is estimated from data using fake factor and fake rate method
• Discriminant – mT
tot = √(mT2(ET
miss, τ1)+mT2(ET
miss, τ2)+mT2(τ2, τ1))
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ATLAS Preliminary -1 = 13 TeV, 13.3 fbs
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• τlepτhad : b-veto (left), b-tag (middle) and high-ET
miss (right) • τhadτhad : b-veto (left)
and b-tag (right) • No significant excess
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, single topttOthersUncertaintyPre-fit background
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H à ττ : mTtot
H/A à ττ : Limits
• ggH/A (left) and bbH/A (right) • Upper limit on σ x BR : 2.0 (2.1) ~ 0.0013 (0.0014) pb for ggA (bbA) at
m(H/A) = 200 ~ 1200 GeV • mA vs tanβ for MSSM : also in the note 11
[GeV]Am200 400 600 800 1000 1200
)[pb]
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BR(
H/A
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, 95 % CL limitsττ →H/A -1 13.3 fb≤ = 13 TeV, s
gluon-gluon fusion
ObservedExpectedσ1±σ2±
(Obs.)-12015, 3.2 fb
(Exp.)hadτhadτ
(Exp.)hadτlepτ
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)[pb]
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, 95 % CL limitsττ →H/A -1 13.3 fb≤ = 13 TeV, s
b-associated production
ObservedExpectedσ1±σ2±
(Obs.)-12015, 3.2 fb
(Exp.)hadτhadτ
(Exp.)hadτlepτ
A à Zh : Overview • Signal
– ggA and bbA • Selection
– llbb : in this slides à – ννbb : also in the note – pT
Z >500 GeV à high-pT
Z category
• Background – Z+jets, top, di-boson, W+jets – multi-jet is negligible
• Discriminant – llbb : m(Zh) – ννbb : mT(Zh)
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-l
+l
bh
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bA
g
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t
low-pTz high-pTz
pTz [GeV] < 500 > 500
# of b-tag 1, 2 1, 2
# of dR = 0.4 jets ≧ 2 -
# of dR = 1.0 jets - ≧ 1
m(jj), m(J) [GeV] 110 ~ 140 75 ~ 145
m(ee) [GeV] 70 ~ 110 70 ~ 110
m(µµ) [GeV] 70 ~ 110 75 ~ 125
ETmiss/√ΣpT [√GeV] < 3.5 -
• low-pTz, 1 tag (left) and 2 tag (right)
• Local significance about 2 σ at m(A) = 260, 440 GeV
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A à Zh : m(Zh)
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2 jets, 1 tag≥2 lep., < 500 GeVV
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ata/
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ATLAS Preliminary -1Ldt = 3.2 fb∫ = 13 TeV s
2 jets, 2 tags≥2 lep., < 500 GeVV
Tp
< 140 GeVbb m≤110 GeV
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ata/
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=600 GeVAmDibosonZ+(bl,cl)Z+(bb,bc,cc)Z+lUncertaintyPre-fit background
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1 large-R jets, 1 tag≥2 lep., VT
p≤500 GeV < 145 GeVbb m≤75 GeV
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ata/
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1 large-R jets, 2 tags≥2 lep., VT
p≤500 GeV < 145 GeVbb m≤75 GeV
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ata/
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• high-pTz , 1 tag (left) and 2 tag (right)
• No significant excess
• ggA (left) and bbA (right) • Upper limit on σ x BR : 4.0 ~ 0.0017 (6.9 ~ 0.026) pb for ggA (bbA) at
m(A) = 220 ~ 2000 GeV • cos(β-α) vs tan(β) for 2HDM : also in the note
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A à Zh : Limits
[GeV]A m200 400 600 800 1000 1200 1400 1600 1800 2000
bb) [
pb]
→BR
(h⋅
Zh)
→(A
σ 9
5% C
.L. l
imit
on
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10 Observed (CLs)Expected (CLs)
σ 1±σ 2±
expected (CLs)νν→Z ll expected (CLs)→Z
b Zb→Zh→A
ATLAS Preliminary-1 Ldt = 3.2 fb∫ = 13 TeV, s
[GeV]A m200 400 600 800 1000 1200 1400 1600 1800 2000
bb) [
pb]
→BR
(h⋅
Zh)
→(A
σ 9
5% C
.L. l
imit
on
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10 Observed (CLs)Expected (CLs)
σ 1±
σ 2±b Zb→Zh→A
ATLAS Preliminary-1 Ldt = 3.2 fb∫ = 13 TeV, s
Summary • W' à lv @ 13 TeV, 36.1 fb-1 [ATLAS-CONF-2017-016]
– Local significance 2.3 σ at 1.1 TeV in eν – Lower mass limit for W'SSM : 5.22 TeV
• Z' à ll @ 13 TeV, 36.1 fb-1 [ATLAS-CONF-2017-027] • Local significance 2.5 σ at 2.37 TeV • Lower mass limit for Z'SSM : 4.5 TeV
• H/A à ττ @ 13 TeV, 13.3 fb-1 [ATLAS-CONF-2016-085] – Upper limit on σ x BR : 2.0 (2.1) ~ 0.0013 (0.0014) pb for ggA (bbA)
at m(H/A) = 200 ~ 1200 GeV • A à Zh @ 13 TeV, 3.2 fb-1 [ATLAS-CONF-2016-015]
– Local significance about 2 σ at m(A) = 260, 440 GeV – Upper limit on σ x BR : 4.0 ~ 0.0017 (6.9 ~ 0.026) pb for ggA (bbA) at
m(A) = 220 ~ 2000 GeV 16