Beyond the Standard Model Higgs Boson Searches at DØ Nicolas Osman On behalf of the DØ Collaboration Centre de Physique des Particules de Marseille 28th July, 2011 PANIC11
2 Outline Tevatron and DØ Neutral MSSM Higgs NMSSM Higgs Doubly Charged Higgs Fermiophobic Higgs Conclusion
3 Accelerator & Detector Proton-anti proton s = 1.96 TeV 11.52 fb-1 delivered 10.32 fb-1 recorded
4 Neutral MSSM Higgs Bosons
5 MSSM Higgs Boson 5 MSSM Higgs bosons 3 neutral: H, h, A (φ) 2 charged: H+, H- φ Branching Ratios: ~90% to bb ~10% to ττ Coupling enhanced by tanβ τ φ φ ττ τ τ τ bφ bττ φ b b b φ b bφ bbb
6 φ ττ Last published result 1fb-1-1 New result: τ τ (5.4 fb ) μ h Submitted to PLB Signature: Isolated lepton and τh Opposite charge Main Background: 2 Mvis = (Pτ1+Pτ2+PT) Z ττ, W + jets, MJ
7 φ ττ Visible mass used to set cross section limits CLs method used at DØ Exclusion comparable to LHC at low mass Model independent MSSM Scenarios
8 bφ bττ Two channels: τμ τh (7.3 fb-1, submitted to PRL) τe τh (prelim. 3.7 fb-1) Selection: Isolated lepton, τh One tagged b-jet Multivariate technique reduces Z+jet, tt, MJ τμ τh
9 bφ bττ MVA distribution used to set cross section limits Most stringent limits from direct search at Tevatron
10 bφ bbb 5.2 fb-1 (PLB) Require 3-4 b-jets Large multijet background Use data-derived MJ model 3 jet pairs per event Use LH to select pair Also cut on LH at 0.65
11 bφ bbb Mbb is final discriminant Excesses at 120 & 200 (1-2 sigma)
12 DØ MSSM Combination Combine results Strongest Tevatron exclusion to date
13 Next-to-MSSM Higgs Bosons
14 h aa 4l μ (τ) μ (τ) a h a μ μ Add extra Higgs singlet to MSSM Mh > 82 GeV Signal: collinear Leptons
15 Doubly Charged Higgs Bosons
16 H++ H-- 4l Occur in extended Higgs sector models Little Higgs, 331 gauge model Same Sign Require at least 2 τ,1 μ Separated into channels depending on τ charge First search at hadron collider with 2 τh Opposite Sign
17 H++ H-- 4l Limits depend on BR of different channels MH < 123 GeV excluded for 100% 4τ First limits of this kind at Hadron collider
18 Fermiophobic Higgs Boson
19 hf γγ Higgs coupling to leptons suppressed γγ coupling x10 DT improves sensitivity Exclude Mhf < 112 GeV
20 Conclusions
21 Conclusions Range of non-sm Higgs searches at DØ These results include up to 8.2 fb-1 of data Recorded ~10 fb-1 so far: aiming for 11 fb-1 MSSM Higgs exclusions comparable to Moriond LHC results Investigations into excesses forthcoming Updated results expected to come in BSM Higgs Searches
22 Additional Slides
23 Tevatron Performance
24 DØ Data-Taking Efficiency Consistently ~ 90%
25 Old MSSM Combinations Combine 3 channels Last result 2009 Up to 2.6 fb-1 of data Combination with CDF (τ states only) Last update 2010-1 Up to 2.2 fb analysed
26 τh Identification Three τ types: Type 1: τ± π±ν (1 charged track, 0 EM clusters) Type 2: τ± π±π0ν (1 charged track, >1 EM clusters) Type 3: τ± π±ππν (>2 charged tracks) Dedicated NN to identify each type
27 b-jet Identification b-jets characterised by long life time Can be identified by: Impact parameter Secondary vertex Soft muon Combined in NN b-tagger Updating to MVA b-tagger
28 MSSM Scenarios At LO, MSSM parameterised by MA, tanβ Require more parameters at NLO Set limits using benchmark scenarios: Mh max: maximal mixing scenario No mixing: mixing parameter set to 0 Higgs sector coupling term, μ, is important Set limits for μ = ± 200 GeV
29 MSSM Scenarios Effective tanβ Increased Higgs Width
30 Modified Frequentist Limits Define hypotheses Htest and Hnull Log likelihood ratio (χ) is calculated: P n H test s = 2ln =s n ln 1 P n H null b s, b, n are expected number of signal, background events Vary n to calculate test, null and data χ
31 Modified Frequentist Limits Generate χs+b and χb distributions Define (frequentist) confidence limit: CLb =P b d CL s b =P s b d Calculate CLs (CLs+b/CLb) Bayesian priors used for systematics