Higgs Physics and SUSY Searches with ATLAS Max Goblirsch, on behalf - - PowerPoint PPT Presentation

SLIDE 1

Higgs Physics and SUSY Searches with ATLAS

Max Goblirsch, on behalf of the MPP ATLAS group MPP Project Review 2014, 15.12.2014

SLIDE 2

Searching for Physics Beyond the Standard Model with ATLAS

One main objective of the LHC: Search for physics beyond the standard model. Two approaches: Indirect - precision measurements

˜ t g g H

Probe the standard model (SM) at high precision. Look for signs of deviations from the SM. The classic LHC probe: top quarks - See talk this morning! A brand-new probe: The Higgs boson! Direct - production of new particles New particles can also be directly produced. Profit from growing collision energies. Look for excesses over SM in predicted decay topologies. Prominent example: Supersymmetry searches. The MPP ATLAS group plays an important role in both fields.

Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 2 / 17

SLIDE 3

Measurement of the Higgs boson mass and decay width in the H → ZZ → 4ℓ channel

H.Kroha, S.Kortner, O.Kortner, R.Röhrig, K.Ecker, F.Sforza, S.Stern

• Phys. Rev. D. 90, 052004

Knowledge of the Higgs boson mass is essential for predicting all other Higgs boson properties New: Highly reduced systematic uncertainty due to improved energy calibration procedures. Now much lower than CMS analysis. → Muon momentum calibration with Z → µµ and J/Ψ → µµ data. → Development of an analytic description of the mass resolution.

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l 4

m 80 90 100 110 120 130 140 150 160 170 Events / 2.5 GeV 5 10 15 20 25 30 35

Data = 1.51) µ = 125 GeV

H

Signal (m Background ZZ* t Background Z+jets, t Systematic uncertainty

l 4 → ZZ* → H

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Ldt = 4.5 fb

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ATLAS

Channel Measured Mass [GeV] H → ZZ → 4ℓ 124.51 ± 0.52(stat) ± 0.06(sys) H → γγ 125.98 ± 0.42(stat) ± 0.28(sys) Combined 125.36 ± 0.37(stat) ± 0.18(sys) Compatibility of results from the two channels: 2.0 σ First limits on Higgs boson natural width: ΓH < 2.6 GeV (95% CL) Made possible by analytical description developed at MPP!

Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 3 / 17

SLIDE 4

Probing the tensor structure of the H → ZZ coupling

H.Kroha, S.Kortner, O.Kortner, K.Ecker ATL-PHYS-PUB-2013-013

The H → ZZ → 4ℓ channel allows for a full reconstruction of the final state kinematics - ideal for spin/CP measurements! SM Higgs: Spin 0, CP even ATLAS & CMS results point towards Spin 0+ with high probability Beyond the standard model contributions could affect HZZ coupling (loops) A(XJ=0 → ZZ) = v −1[g1m2

Vǫ∗ 1ǫ∗ 2

• Tree-level SM

+ g2f ∗(1)

µν f ∗(2)µν + . . .

• CP-even

+ g4f ∗(1)

µν ˜

f ∗(2)µν

• CP-odd

] → Probe for admixtures in decay amplitudes by measuring final state angular distribution (sensitive to CP) Sensitivity study for integrated luminosities 300 fb−1 and (3000 fb−1): |g2|/g1 < 1.39 (0.81) at 95% CL |g4|/g1 < 1.03 (0.49) at 95% CL

Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 4 / 17

SLIDE 5

Measurement of the Higgs coupling to Vector bosons

S.Kortner, H.Kroha, J.Bronner ATLAS-CONF-2014-060, CERN-THESIS-2014-031

The H → WW channel allows a study of the Higgs coupling to vector bosons. New: Observation of Higgs boson decays to WW (6.1 σ) Evidence for the Vector Boson Fusion (VBF) production mechanism(3.2 σ) → Measurement of Higgs production via vector boson fusion with WW decay as a direct probe of the Higgs boson coupling to vector bosons Measured VBF Signal strength: µ = 1.28 ± 0.4(stat) ± 0.25(sys)

Events / 20 GeV 10 20 50 100 150 Events / 20 GeV 10 20 30 stat ± Obs syst ± Exp

VBF

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m ATLAS Prelim. WW* → H

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TeV, 8 = s H→WW→eνeν / μνμν

Transverse mass distribution in the VBF channels

Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 5 / 17

SLIDE 6

Measurement of the Higgs coupling to fermions

S.Kortner, H.Kroha, D.Zanzi ATLAS-CONF-2014-061, CERN-THESIS-2014-085

The Higgs boson’s direct coupling to fermions can be measured in the H → ττ and H → b¯ b decays first evidence for the H → ττ coupling (4.6σ) New: Multivariate analysis approaches, reduction of systematic uncertainties. Major contribution from fully hadronic final state.

ln(1+S/B) w. Events / 10 GeV

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weighted (Data-Bkg.)

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=1.4) µ ( (125) H =1.6) µ ( (110) H =6.2) µ ( (150) H Data =1.4) µ ( (125) H τ τ → Z Others Fakes Uncert.

ATLAS Preliminary VBF+Boosted τ τ → H

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, 4.5 fb = 7 TeV s

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, 20.3 fb = 8 TeV s Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 6 / 17

SLIDE 7

Measurement of the Higgs coupling to fermions

H.Kroha, S.Kortner, F .Müller, F .Sforza arXiv:1409.6212

The Higgs boson’s direct coupling to fermions can be measured in the H → ττ and H → b¯ b decays Improved search for VH → Vb¯ b, but no evidence yet (1.5σ). Ongoing optimisation for run 2 based on the substructure of boosted b-jets Run 2: Measure coupling to the top quark in the t¯ tH production channel

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Data 2012 =1.0) µ VH(bb) ( Diboson Uncertainty

ATLAS

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∫

= 8 TeV s 0+1+2 lep., 2+3 jets, 2 tags Weighted by Higgs S/B

) µ Signal strength (

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H

m

arXiv:1408.7084

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= 1.17 µ γ γ → H

arXiv:1408.5191

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arXiv:1412.2641

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JHEP11(2014)056

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ATLAS-CONF-2014-061

Total uncertainty µ

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σ 1 ±

released 09.12.2014

Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 7 / 17

SLIDE 8

Combined coupling fits

ATL-PHYS-PUB-2014-016, ATLAS-CONF-2014-009

Combine the results into a study of the Higgs boson couplings Common fit of couplings to fermions and vector bosons from individual measurements Currently still limited accuracy - expect major improvements in run 2 MPP to contribute to individual measurements and global fit → Important future ingredients: ttH and VH → Vb¯ b - no significant observation yet

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κ 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4

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= 7 T eV s , ZZ*, WW* γ γ

Prospects LHC Run 1

→ Combined H

private comparison

Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 8 / 17

SLIDE 9

Interpreting the couplings measurement - Dark Matter at the LHC

ATL-PHYS-PUB-2014-017

Major goal for run 2: use Higgs couplings results to constrain dark matter (DM) Higgs portal scenario: Competitive with direct searches at low DM masses

q q Z H χ χ Z ℓ− ℓ+

Further sensitivity to DM at the LHC:

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Direct search for invisible Higgs decays

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Direct search for recoils off invisible particles (Monojets)

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Direct SUSY searches (R-Parity conservation) assume presence of DM

Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 9 / 17

SLIDE 10

Search for neutral MSSM Higgs bosons

S.Kortner, H.Kroha, A.Manfredini ATLAS-CONF-2014-049, CERN-THESIS-2014-080

Higgs searches can also directly target new physics models Recently published ATLAS searches for MSSM higgs bosons based on 2012 data Exclusion limits on MSSM paramters (tan β, mA) for various models Strong implications on viability of SUSY models Large range of tan β values excluded Heavier H/A bosons with mA/H > 200 GeV preferred (mmax

h

) if discovered boson is the h ATLAS-MPP: fully leptonic final state (H → ττ → ℓννℓνν) → Important for excluding A/H masses below 200 GeV

Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 10 / 17

SLIDE 11

Direct searches for Supersymmetry - Top Squarks

H.Kroha, O.Kortner, M.Flowerdew, N.Köhler JHEP 06 (2014) 124

A light top squark is a key ingredient to natural supersymmetry Challenging phase-space region for existing searches: m(˜ t) ≈ m(t) New analysis approach exploiting spin correlations in the dileptonic t¯ t decay greatly enhances sensitivity → Strong MPP effort - to be extended to general stop searches in run 2

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All limits at 95% CL

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Qualitative Illustration no spin correlations s p i n c

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r e l a t i

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Opening angle between the leptons 0.5 1 1.5 2 2.5 3 SM/SUSY 0.5 1 1.5

1 2 1 2

Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 11 / 17

SLIDE 12

Direct searches for Supersymmetry - Electroweak production

H.Kroha, M.Flowerdew, M.Goblirsch, J.Junggeburth, F.Sforza

• Phys. Rev. D. 90, 052001 (2014)

Can also target electroweak production of SUSY particles Can lead to multi-lepton final states - rare in the SM Four-lepton search led by MPP Final run 1 analysis: Significant analysis improvements, additional interpretations

˜ χ0

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SR2noZa

New, challenging final state: 2e/µ, 2 hadronic τ decays

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σ 1 ± Observed limit ( ) σ 1 ± Expected limit ( All limits at 95% CL

Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 12 / 17

SLIDE 13

Direct searches for Supersymmetry - R-Parity violation

H.Kroha, M.Flowerdew, M.Goblirsch, J.Junggeburth, F.Sforza

• Phys. Rev. D. 90, 052001 (2014)

Main MPP SUSY focus: Searches for R-Parity violating Supersymmetry (RPV) Lightest supersymmetric particle decays to SM particles → Requires dedicated search regions MPP leading ATLAS effort in search for lepton-number violating (LFV) RPV couplings Main tool for prompt LFV RPV decays: 4-lepton search → highly versatile analysis

˜ g ˜ g ˜ χ0

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Data 2012 Total SM Reducible ZZ Z t t tWZ Higgs VVV )=(450,300) GeV

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theory

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ATLAS

=8 TeV s ,

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l ν →

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χ ∼ All limits at 95% CL

Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 13 / 17

SLIDE 14

Direct searches for Supersymmetry - Reinterpretations

H.Kroha, M.Flowerdew, D.Krauss, J.Mellenthin

Can extend reach of existing analyses with Reinterpretations Interpret results of existing analyses in new signal models Example: Generic RPV decay branching ratios in 4-lepton search MPP also involved in RPV interpretations of conventional SUSY searches In addition: pMSSM interpretations of the 4-lepton analysis → Fully exploit existing work → Extended

Expected Mass Exclusion [GeV] 1100 1150 1200 1250 1300 1350 )

R

τ BR( 0.2 0.4 0.6 0.8 1 )

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τ BR( 0.1 0.2 0.3 0.4 0.5 ATLAS Work in progress

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= 8 TeV, 20.3 fb s ) = 0.9 g ~ ) / m(

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χ ∼ m( ν

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+

l →

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χ ∼ qq → g ~ g ~ → pp

N e w

Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 14 / 17

SLIDE 15

Direct searches for Supersymmetry - R-Parity violation, long-lived

H.Kroha, M.Flowerdew, M.Goblirsch ATLAS-CONF-2013-092

R-Parity violating decays can have a significant lifetime Long-lived decays can lead to displaced vertex signatures. MPP performing a Displaced Dilepton search (also targeting non-RPV models). Technically challenging: Need to rerun large parts of the ATLAS reconstruction. Build on work done by existing multi-track displaced vertex search. Results nearly final - expect publication early 2015.

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Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 15 / 17

SLIDE 16

Prospects for direct SUSY searches in run 2

ATL-PHYS-PUB-2014-010

Direct searches for heavy particles expected to strongly profit of increased √s Strong production: Can surpass existing sensitivity even with small datasets → Expect results very early in run 2 (late 2015) Electroweak production: Statistically limited in early data → Slower pace than strong production, but also expected to surpass run 1 quickly Expect sensitivity to TeV-scale top squarks (’natural SUSY’) with the full run-2 data.

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= 30%

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Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 16 / 17

SLIDE 17

Summary - Good times for new physics searches

ATLAS: Twofold approach to new physics searches Precision studies of Higgs boson and top quark physics Direct searches for new particles Strong MPP presence in both fields, leading several analysis efforts Analysis of run 1 data drawing to a close Very mature analyses, advanced techniques Wide range of final states and interpretations No significant signs of new physics yet, but . . . LHC run 2 is about to start! Dramatically increased cross-sections for direct searches Enhanced statistics for precision measurements 2015: ∼ 10fb−1 of 13 TeV data expected - first results by PR ’15?

Max Goblirsch (ATLAS) ATLAS Higgs/SUSY 15.12.2014 17 / 17