Beyond the Standard Model Higgsat ATLAS
Hal Evans, Indiana University, for the ATLAS Collaboration
Mitchell Workshop on Collider & Dark Matter PhyiscsMitchell Institute for Fundamental Physics
Texas A&M University12 – 15 May, 2014
H. Evans Mitchell Workshop - May 12, 2014 2
The Higgs We FoundThe Higgs We Found
Signal Strength: μ = (σ×BR)/(σ×BR)SM Spin Structure (vs 0+)
verySM-like
verySM-like
but still roomfor
somethingnew
ATLAS-CONF-2014-009Phys Lett B 726 (2013) 120
H. Evans Mitchell Workshop - May 12, 2014 3
Beyond the SMBeyond the SM
Large number of possible models ==> two strategies− consider only simplest extensions of the SM− topology-driven (~model independent) searches
Models considered− Minimal Composite Higgs Model (MCHM)
> Higgs = pseudo-Nambu-Goldstone boson ==> explains scalar naturalness
− Single additional electroweak singlet> simplest extension, two CP-even Higgs bosons
− Two Higgs Doublet Models (2HDM)> additional doublet ==> h0, H0 (CP-even), A0 (CP-odd), H± ==> resolves hierarchy problem> 4 types based on coupling structure (Type-II = MSSM)
− Higgs Triplets> h0, H0 (CP-even), A0 (CP-odd), H±, H±± ==> explains neutrino masses/mixings
− Next-to-Minimal SUSY (NMSSM)> MSSM + complex singlet(S): generates MSSM μ-term through S spontaneous symmetry breaking
− Higgs and Dark Matter> Dark Matter couples primarily to the Higgs ==> “invisible” decays
H. Evans Mitchell Workshop - May 12, 2014 4
ATLAS BSM Higgs AnalysesATLAS BSM Higgs Analyses
Published− “Search for top quark decays t→ qH with H→γγ using the ATLAS detector”, arXiv:1403.6293, submitted to JHEP− “Search for Invisible Decays of a Higgs Boson Produced in Association with a Z Boson in ATLAS”, arXiv:1402.3244,
accepted by PRL− “Search for a Multi-Higgs Boson Cascade in W+W- bbar events with the ATLAS detector in pp collisions at √s = 8 TeV”,
Phys. Rev. D 89, 032002 (2014), arXiv:1312.1956− “Search for a light charged Higgs boson in the decay channel H+ → csbar in ttbar events using pp collisions at √s = 7
TeV with the ATLAS detector”, Eur. Phys. J. C, 73 6 (2013) 2465, arXiv:1302.3694− “Search for charged Higgs bosons through the violation of lepton universality in ttbar events using pp collision data at
√s = 7 TeV with the ATLAS experiment”, JHEP03(2013)076, arXiv:1212.3572− “Search for the neutral Higgs bosons of the Minimal Supersymmetric Standard Model in pp collisions at √s =7 TeV with
the ATLAS detector”, JHEP02(2013)095, arXiv:1211.6956− “Search for doubly-charged Higgs bosons in like-sign dilepton final states at sqrt(s) = 7 TeV with the ATLAS detector”,
Eur.Phys.J. C72 (2012) 2244, arXiv:1210.5070
Preliminary− “Constraints on New Phenomena via Higgs Coupling Measurements with the ATLAS Detector”, ATLAS-CONF-2014-010− “Search for Higgs bosons in Two-Higgs-Doublet models in the H → WW → eνμν channel with the ATLAS detector “,
ATLAS-CONF-2013-027− “Search for a Higgs boson decaying to four photons through light CP-odd scalar coupling using 4.9 fb-1 of 7 TeV pp
collision data taken with ATLAS detector at the LHC”, ATLAS-CONF-2012-079
+ other, superseded results (not discussed here)− see: https://twiki.cern.ch/twiki/bin/view/AtlasPublic/HiggsPublicResults
2HDM Triplet NMSSM Dark MatterSingletMCHM
H. Evans Mitchell Workshop - May 12, 2014 5
ATLAS DetectorATLAS Detector
2012 ATLAS Detector
2012 Trigger/DAQ
Rate (kHz) 2012 2015
Bunch Crossing 20,000 40,000
L1 Trigger 75 100
to disk 0.4 ~1
H. Evans Mitchell Workshop - May 12, 2014 6
Data Taking (pp Mode)Data Taking (pp Mode)
Year √s BC Delivered Good Qual
2010 7 TeV 50 ns 0.048 fb-1 0.045 fb-1
2011 7 TeV 50 ns 5.46 fb-1 4.5 fb-1
2012 8 TeV 50 ns 22.8 fb-1 20.3 fb-1
2015 13 TeV 25 ns ~40 fb-1
pileup
H. Evans Mitchell Workshop - May 12, 2014 7
General BSM Higgs Search FeaturesGeneral BSM Higgs Search Features
Triggers
Physics Objects
Pileup− important effect for jets, taus,
missing ET, b-tagging
− less of an issue for e/μ
2012 Trigger Level-1 Threshold [GeV] “Analysis” Threshold [GeV]
single e 18 (isol) / 30 (non-isol) 25 / 40
di-photon 2 x 10 (isol) 2 x 15
single μ 15 20
tau+ETmiss 15, 35 40, 60
e / γ calorimeter, tracking, γ→e+e-
μ muon system, tracking
tau BDT: collimation, isol, shower profile
jets anti-Kt (R=0.4)
ETmiss objects + topo clusters in calo
b-jets lifetime-related Neural Net
Z / W Z → ℓℓ / W → ℓν, qq'
top t → b W
H. Evans Mitchell Workshop - May 12, 2014 8
Minimal Composite Higgs Model&
Additional EW Singlets
Minimal Composite Higgs Model&
Additional EW Singlets
H. Evans Mitchell Workshop - May 12, 2014 9
MCHM & Additional Singlet ResultsMCHM & Additional Singlet Results
Re-analysis of all ATLAS Higgs coupling measurements− h→γγ, h→ZZ*, h→WW*, h→ττ, h→bb
Minimal Composite Higgs Modelscouplings to Vector Bosons & Fermions modifiedfrom SM values:
Additional EW Singleth & H couple with reduced strength
κV ,κH=F(ξ=v2 / f2)
95% CL f [GeV]
MCHM4 >710(460)
MCHM5 >640(550)
σh=κ2σh,SM σH=κ ' 2
σH ,SM
BRh, i=BRh ,SM, i BRH, i=(1−BRH ,new )BRH ,SM, i
κ'2 < 0.12(0.29)
ATLAS-CONF-2014-010
(κ' 2)
ATLAS-CONF-2014-009
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Two Higgs Doublet ModelsTwo Higgs Doublet Models
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2HDM Features2HDM Features
General Features− 5 physical Higgs particles: h0, H0 (CP-even), A0 (CP-odd), H±
− separate vev's for each doublet: v12 + v2
2 = (246 GeV)2 tanβ = v2 / v1
− 5 parameters: mh , mH , mA , mH± , tanβ, α (h0–H0 mixing)
4 Types suppress FCNCs
Coupling Scale Type I Type II Type III Type IV
doublet 1 vector bosons u-type q's q's as type I q's as type II
doublet 2 fermions d-type q's ℓ's as type II ℓ's as type I
κV sin(β−α) sin(β−α) sin(β−α) sin(β−α)
κu cos α / sin β cos α / sin β cos α / sin β cos α / sin β
κd cos α / sin β −sin α / cos β cos α / sin β −sin α / cos β
κℓ cos α / sin β −sin α / cos β −sin α / cos β cos α / sin β
MSSM
h0 co
uplin
gs /
SM
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2HDM Coupling Limits2HDM Coupling Limits
From ATLAS SM Higgs coupling measurements− h→γγ, h→ZZ*, h→WW*, h→ττ, h→bb
ATLAS-CONF-2014-010
ATLAS-CONF-2014-009
Type I Type II Type III Type IV
SimplifiedMSSM
Consistent w/ SM-like alignment: cos(β−α)~0 − observed limits better than expected b/c meas. couplings generally > SM
H. Evans Mitchell Workshop - May 12, 2014 13
2HDMs and Vector Bosons2HDMs and Vector Bosons
Search for Heavy Higgs: H0 → WW → ev μv− selection as in SM h0 → WW analysis
> e + μ + Etmiss + 0 or 2(non-b) jets
− Neural Net to distinguish signalfrom background (mainly di-boson)
ATLAS-CONF-2013-027
Type I Type II
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2HDMs and Fermions2HDMs and Fermions
Higgs coupling to τ-leptons and b-quarks enhanced (large tanβ)− associated production with b-quarks (h/H/A b) increasingly important− decays h/H/A → ττ, bb dominate
Charged Higgs production involves top quarks− decay mainly via: H+ → τv
> H+ → cs also possible
τ/b/t play an importantrole in many searches
mH+ < mt mH+ > mt
t → b H+ associated production
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Examples of τ & b-ID at ATLASExamples of τ & b-ID at ATLAS
b mis-tagging rate (εb = 70%)
τ→hadrons tagging: bgrd vs eff.
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h/H/A → ττ, μμ in MSSMh/H/A → ττ, μμ in MSSM
h/H/A (φ) production via: gg→φ and φb(b), then φ → ττ or μμ− BR(φ→ττ) ~ 10% in mass range, BR(φ→μμ) ~ 0.04% (clean signature)
> use τeτμ (6%), τeτhad (23%), τμτhad (23%), τhadτhad(42%)
− separate into events with and without b-jets
JHEP 02(2013)095
complementary exclusion to LEP generic scalar boson: gg-fusion & b-assoc.
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Charged Higgs SearchesCharged Higgs Searches
Indirect search: ℓ universality− compare BR(tt → e/μ/τ)
Direct (two jet) search: mH+<mt
− − search for a peak in M(cs)
> kinem. fit: jets↔partons
t t̄ → H+(c s̄)b W−
(e/μ ν)b
Rl =BR( t t̄ →bb̄+e/μ τhad+Nν)
BR( t t̄ →bb̄+eμ+Nν)
EPJ C73 6 (2013) 2465JHEP 03(2013)076JHEP06(2012)039
interpretation w/in MSSM − incl. τhad+jets MT
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Charged Higgs Searches (cont)Charged Higgs Searches (cont)
Direct search in the H+ → τ v mode− mH+ < mt:
− mH+ > mt:
− challenging all-hadronic mode
t t̄ → H+ ( τhad ν)b W (qq̄ ' b̄)b
gb̄ → t̄ (qq̄ ' b̄) H+ ( τhad ν)
gg → t̄ (qq̄ ' b̄)b H+ ( τhad ν)
mH+< mt
mH+> mt
interpretation w/in MSSM (mhmax scenario)
ATLAS-CONF-2013-090
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2HDM multi-Higgs Cascade2HDM multi-Higgs Cascade
Search for: H0 → WH+ → WWh0 → WWbb− same topology as top-pair events− distinguish using Boosted Decision Tree
> uses: mbb , mbbW , mbbWW , Δrbb , mtlep,,had, mt – mtbar
− trained at 36 different (mH0 , mH+) points
> mH0: 325–1025 GeV ; mH+: 225–925 GeV
expected limits (95% CL) observed limits (95% CL) limits on σgg→H0obs/σgg→H0
2HDM-II
PRD 89 (2014) 032002
upper limits still > theoretical (SM-like) H0 cross-section − but getting close in high-mass region
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2HDM Higgs & FCNC Top Decays2HDM Higgs & FCNC Top Decays
t → c h0 is GIM-suppressed in the SM (BR ~ 3∙10-15)− can reach ~0.15% in some 2HDM Type-III models
Search in− small h → γγ BR (0.23%) offset by distinctive signature
t t̄ → [h(γ γ)c /u] [W (e/μ ν ,q q̄ ')b]
arXiv:1403.6293√λ tcH2
+λ tuH2
< 0.17 (0.14 expected)
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Other BSM Higgs:Higgs Triplet Models &
Next-to-Minimal Supersymmetry
Other BSM Higgs:Higgs Triplet Models &
Next-to-Minimal Supersymmetry
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Further Beyond the SMFurther Beyond the SM
Higgs Triplet: H++ → ℓ+ℓ+
− same sign: ee, eμ, μμ eventsLight CP-odd Higgs in NMSSM
− h0 → aa → γγ γγ (ma < 3 mπ0)
− gg → a → μμ (ma < 2 mB)
HL++
HR++
EPJ C72 (2012) 2244
ATLAS-CONF-2012-079
ATLAS-CONF-2011-020
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Dark Matter and the HiggsDark Matter and the Higgs
H. Evans Mitchell Workshop - May 12, 2014 24
Higgs Portal to Dark MatterHiggs Portal to Dark Matter
WIMP Dark Matter candidate could interact mainly with Higgs− increase Z h0 → ℓℓ + Et
miss rate
− modify visible h0 decay rate: h → γγ, ZZ*(4ℓ), WW*(ℓvℓv), ττ, bb
ATLAS-CONF-2014-010arXiv:1402.3244
combine Zh → ℓℓ & SM coupling meas's
stringent constraintsat low χ mass
(but model-dependent)
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LHC's Future PlansLHC's Future Plans
√s = 13-14 TeV; L → 2×1034 cm-2 s-1; ∫L dt ~ 120 fb-1√s = 13-14 TeV; L → 2×1034 cm-2 s-1; ∫L dt ~ 120 fb-1
√s = 14 TeV; 5×1034 cm-2 s-1; 3,000 fb-1√s = 14 TeV; 5×1034 cm-2 s-1; 3,000 fb-1
√s = 14 TeV; 2×1034 cm-2 s-1; 350 fb-1√s = 14 TeV; 2×1034 cm-2 s-1; 350 fb-1
CERN update: Dec. 2, 2013
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ATLAS: Goals & ChallengesATLAS: Goals & Challenges
LHC upgrades ==> substantial challenges for ATLAS− trigger, data acquisition, tracking, data processing, ….
But also opportunities: energy, integrated luminosity− See talk by Carmen Garcia for more details
Phase Pileup Major ATLAS Changes
Run 1 (2012) 20
Run 2 (2015-18) 43 L1 topological trigger, Inner Pixel Layer
Run 3 (2020-22) 50-80 forward muon syst, readout/trigger
Run 4 (2025...) 140-200 new tracking, trigger architecture
CERN-2012-022
current h→γγ
ATL-PHYS-PUB-2013-015ATLAS-CONF-2014-010
SM Higgs Couplings
2HDMType IILimits
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ConclusionConclusion
Discovery of a Higgs boson has not stopped BSM searches− observed couplings limit many models though
Focus on simplest extensions of the SM & model-indep searches− emphasis on Two Higgs Doublet Models, but others explored as well− results rely on excellent performance of ATLAS detector
> e, μ, γ, τ- and b-tagging, Etmiss, top
− no evidence for Higgs beyond the SM found yet
Upgrades to LHC and ATLAS will broaden the search− higher mass reach & increased coupling sensitivity− but significant challenges for detector, trigger, analyses
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