Search for non-standard-model Higgs at the LHC with ATLAS Dimitris Fassouliotis University of Athens on behalf of the ATLAS Collaboration

Outline MSSM Higgs sector: h, H, A and H± Emphasis is put on: Investigate decay channels in particles h/H/A→τ+τ-, μ+μ- - light / heavy H± → τν, tb Investigate decay channels in sparticles 4l + Missing ET final states (and one scenario for invisible Higgs decays) Probe E-W symmetry breaking by the vector boson scattering at high mass Especially useful in case that no Higgs boson discovered. Emphasis is put on: Use of most recent theoretical calculations Detailed detector simulation Detailed consideration of systematic uncertainties in each channel Data driven methods for the background estimation Analyses included concern data at 14 TeV Results shown without pile-up and cavern bkg (effect small at L=1033 cm−1s−1) Details can be found at: CERN-OPEN-2008-020 (ATLAS, arXiv:0901.0512) ATL-PHYS-PUB-2009-079 Several studies in progress not mentioned here

h/H/A→τ+τ- / μ+μ- Production Direct Production Associated Production Several benchmark scenarios for the study of MSSM Higgs at LHC. At tree level, the Higgs sector described by two parameters mA and tanβ Results shown here for this study within the mh-max scenario mh-max scenario Η and A mass degenerate for most of the parameter space → Cross sections added Direct Production Associated Production (dominant at large tanβ) Production Decay channels: Advantage: High branching ratio Advantage: Excellent mass resolution

h/H/A → τ+τ- →l+l-4v (event selection) Backgrounds: Event selection Trigger: single + double lepton triggers Two isolated, opposite sign leptons ≥1 b-jet and no central jet activity missing ET required mττ reconstruction collinear approximation L=30fb-1 L=30fb-1

h/H/A → τ+τ- →l+l-4v (background control – results) Systematic uncertainties Theoretical: <20% on signal and ~10% on bkg Experimental: <10% on signal and ~10% on bkg (jet energy scale /resolution and b-tagging) Evaluation of backgrounds from data Estimation of the irreducible from the control samples Shape: replace real e/μ with simulated τ Normalization (<3% systematic uncertainty):

h/H/A → μ+μ- (event selection) Mass resolution 3% for mA=200 GeV Backgrounds: Event selection Trigger: single high pT muon Two isolated, high pT, opposite sign muons Low missing ET 0 b-jet or ≥1 b-jet and no central jet activity L=30fb-1, tanβ=20 0 b-jet analysis ≥1 b-jets analysis Low efficiency in b-jet analysis due to soft b-jets in signal

h/H/A → μ+μ- (background control – results) 5σ discovery 95% CL limit Systematic uncertainties Theoretical: <20% on signal and ~10% on background Experimental: 5% on signal and ~10% on background (mainly b-tagging) Evaluation of backgrounds from data Side band fit together with Control samples (signal free samples with same dilepton mass spectrum) Estimation accuracy background estimation

H±→τν / bt H± decay modes Light H± (mH<mtop) Heavy H± (mH>mtop) tanβ=35 tanβ=2 H±→τν / bt mh-max scenario H± decay modes Light H± (mH<mtop) Heavy H± (mH>mtop) Production: Decay:

Light Η± t → H+b, H+→ τ±ν (event selection) Backgrounds: Event selection Trigger tau and ETmiss Single lepton and/or ETmiss Single lepton or tau and ETmiss Objects kinematics 1τ-jet, 2b-jets, ≥ 4jets, ETmiss 1l, 2b-jets, ≥4 jets, ETmiss ≥ 1l,τ ≥ 1b-jets, ≥3 jets, ETmiss W, top reconstruction |mWrec-mW|<30 GeV |mtrec-mt|<40 GeV Angular-charge correlation 100<mtrec<300 GeV 3 ν make complete event reconstruction difficult tt suppression Likelihood discriminant l - t angle in W rest frame tanβ=20 mH=130 GeV L=10fb-1 If the charged Higgs boson is light, then BR(t →bW) is smaller:

H+t → tbt→ bWbbW →bqqbblν Heavy Η± H+t → tbt→ bWbbW →bqqbblν (event selection) (gg→ tbH+ →bqqbτ(had)ν / gb→ tH+ →bqqτ(had)ν similar selection as in light Η± case) H+t → tbt→ bWbbW →bqqbblν Trigger Single lepton and ETmiss or tau and ETmiss Object multiplicity Kinematics 1 isolated lepton , ≥ 3b-jets, ≥ 5jets, ETmiss W, top reconstruction Constraint on W mass / Likelihood function for combinatorial bkg tt suppression Likelihood discriminant L=1fb-1 tanβ=35 H+t→ τ(had)ν bW→τ(had)νbqq H+t → tbt→ bWbbW →bqqbblν tanβ value for high significance L=1fb-1 bqqbblν bqq[b]τ(had)ν

Η± (background control – results) Main background in H± searches is Systematic uncertainties Theoretical: <20% on signal and ~12% on bkg Experimental: 10-40% signal and bkg (mainly due to jet energy scale and b-tagging) Evaluation of main background from data: Control samples Replace real μ with simulated τ Estimation accuracy <10% W mT for real/scaled btνbjj events mh-max scenario mh-max scenario

Higgs bosons decaying into SUSY cascades to 4 leptons + ETmissing Final state with 4 leptons +ETmissing explored (as in the example) MSSM or mSUGRA scenarios with decays to light or heavier neutralinos / charginos investigated Backgrounds: Event selection 2 pairs of opposite sign opposite flavor isolated leptons from the interaction vertex kinematics, lepton pT dilepton masses to reduce Z, ZZ ETmissing to reduce Z, ZZ, SUSY Jet multiplicity to reduce tt,SUSY Systematic uncertainties Experimental uncertainties: small Signal depends strongly on slepton masses Main SM background after cuts Can be evaluated from data via control samples MSSM Set 2 H/A and tH± included

Vector boson scattering at high mass (event selection) Standard Model can be a low energy effective theory New physics can be seen in vector boson pair resonances Higgs-like scalar resonances and/or technicolour-like vector resonances If resonances not produced the vector boson scattering cross sections must be measured Event signature Forward jets Central jets that might be merged (decaying vector boson may be seen as one single wide and heavy jet) Dileptons in the central region Missing ET from W, or Z → νν Backgrounds: q W,Z Z,W Res W Z jj.ll,νν jj.lν j Event selection: Trigger: single or double lepton, single or double jet Isolated high pT leptons 2 forward tag jets Central jet veto (except jets originating from W,Z) Top rejection 130 < mt < 240 GeV W,Z mass selection

Vector boson scattering at high mass (results) Some of the results (normalized to 1fb-1) WZ→lνll WZ→llj(j) L≈60 fb-1 for discovery of resonances up to 800 GeV Systematic uncertainties Theoretical: Background cross section factor ~ 2 Data driven background estimation needed Experimental: small Underlying event: ~ 5% ZZ→llνν

Summary Neutral MSSM Higgs Charged MSSM Higgs h/H/A → ττ With 30fb-1 provides good coverage of the parametric space (mA-tanβ plane). h/H/A → μμ Competitive channel, helps to increase sensitivity, provides sharp mass peak. Charged MSSM Higgs From the channels presented, H± → τν → τ(had)νν provides the highest sensitivity. With 1fb-1 of well understood data, the Tevatron limits can be superseded. With 30 fb-1 the combined results, cover almost completely the parameter space for low masses (except tanβ ≈7). For high masses, large tanβ values are also covered. MSSM Higgs decays in SUSY particles 4leptons +ETmissing With ~100 fb-1, high mass MSSM Higgs bosons can be discovered. Vector boson scattering at high mass Resonances that provide information for different mechanisms of EW symmetry breaking can be discovered with ~60 fb-1. Data driven methods to evaluate backgrounds have been formed and will be studied in detail as real data are accumulated. One final comment: The outcome of most analyses was presented in the context of specific models. This however, is not mandatory and results can also be presented in a model independent way.

Back up slides

Sensitivity to an Invisibly Decaying Higgs Boson Model independent study of As an example, in R-parity conserving SUSY Higgs decay to lightest neutralinos Systematic uncertainties VBF qqH Theoretical background shape: ~10% Experimental background shape: ~ 5% (jet energy scale /resolution) ZH Theoretical background: ~6% Experimental background: ~4% (lepton energy scale /resolution) Topologies studied: VBF qqH, ZH VBF qqH Backgrounds: Event selection Trigger: ETmiss, forward jets ETmiss not close to jet, forward jets lepton veto, central jet veto counting experiment / shape distribution φjj ZH Trigger: Single lepton, dilepton, ETmiss Two leptons compatible with mZ ETmiss, b-jet veto BDT with kinematic variables L=30fb-1

Theoretical uncertainties Neutral MSSM Higgs Direct production NLO calculation M. Spira, HIGLU: A Program for the Calculation of the Total Higgs Production Cross Section at Hadron Colliders via Gluon Fusion including QCD Corrections, 1995 Associated production Inclusive approach NLO (Reliable when both b at high pT) S. Dittmaier, M. Kramer, and M. Spira, Higgs radiation off bottom quarks at the Tevatron and the LHC, 2004. S. Dawson, C.B. Jackson, L. Reina, and D. Wackeroth,, Phys. Rev. Lett. 94 (2005) 031802 Exclusive Approach NNLO The theoretical uncertainty on the production cross-section, is estimated taking into account contributions from the scale uncertainty and from the uncertainty on the parton distribution functions. The scale uncertainty is obtained from Harlander, R. V. and Kilgore, W. B., Phys. Rev. D 68 (2003) 013001. The contribution from the PDFs is estimated by exchanging MRST2002 for MRST2004 (conservative approach). Charged MSSM Higgs E. Boos and T. Plehn, Phys. Rev. D 69 (2004) 094005 T. Plehn, Phys. Rev. D 67 (2003) 014018