Dmitri Sidorov Oklahoma State University On behalf of the ATLAS Collaboration DIS2014, 04/28/2014

Transcription

1 Dmitri Sidorov Oklahoma State University On behalf of the ATLAS Collaboration DIS4, 4/8/4

2 Introduc)on We discovered a Standard Model (SM) like Higgs boson at mh=5 GeV. This is not the end of the story. There are indications that SM is incomplete. There is a lot of room for non- SM interpretation. Two Higgs Doublet Models (HDM) there are two electroweak doublets (only one doublet in SM). Minimal Supersymmetric Standard Model (MSSM) solution to hierarchy problem and dark matter candidates. Next- to- Minimal Supersymmetric Model (NMSSM) solves the problem with an additional electroweak singlet S, and the resulting Higgs sector contains the MSSM Higgs content. 4/8/4 DIS4

3 Searches Next to Minimal: NMSSM a μμ NMSSM h a a 4γ Neutral Higgs searches: H τ τ and μ μ HDM H W W Invisible Higgs Fermiophobic H γγ Charged Higgs searches: H ± τ ± υ jets H ± cs Doubly charged Higgs Measurements of Higgs boson coupling scale factors in different coupling parametrizations. 4/8/4 DIS4 3

4 MSSM Higgs Search for Neutral Higgs heavy (H) CP- even/light (h)/ CP- odd (A) decaying ττ/μμ Production: gluon fusion, b- associated production. separated into b- tagged and b- vetoed ττ- channel: three groups (eμ, lhad,hadhad) μμ- channel: pt> GeV, η <.5, MET<4 GeV Events / 5 GeV Events / GeV µ µ, b-tagged sample ATLAS Data m A =5 GeV, tan!=4 Z " µµ Multi-jet Top Bkg. uncertainty L dt = 4.8 fb s = 7 TeV ! lep! had, b-tagged sample ATLAS m µµ Data m A =5 GeV, tan "= Z!! Z ee/µµ Other electroweak Top Multi-jet Bkg. Uncertainty s = 7 TeV, $ L dt = 4.7 fb MMC 4/8/4 DIS4 4 m!!

5 MSSM Higgs results Obtain combined limits for both channels tanβ vs ma in mhmax, μ> MSSM scenario limit on production for a generic single scalar boson decaying into μμ/ττ tan! ATLAS MSSM combination, 95% CL limit " Ldt = fb s = 7 TeV max, µ> m h Observed CLs Expected CLs ± ± LEP m A $ BR(!""/µµ) [pb] 95% CL limit on %! -!""!µµ JHEP (3) 95 Observed bb! CLs Expected bb! Observed gg! CLs Expected gg! ± % bb! ± % bb! ATLAS s = 7 TeV Ldt = fb & m! 4/8/4 DIS4 5

6 HDM Simple extension of SM scalar sector, yet with rich phenomenology: Baryon asymmetry contrary to the SM, allow for both explicit and spontaneous CP violation Dark matter candidates Flavour Changing Neutral Current Higgs sector of HDM models described by parameters: 4 Higgs masses, tan β (ratio of vacuum expectation values vev) and α mixing between the two neutral CP even states h, H Type I: One Higgs doublet couples to vector bosons ( fermiophobic ), while the other couples to fermions. Type II: MSSM like model, one doublet couples to up- type quarks, the other to down- type quarks Type III: Lepton- specific model, Higgs bosons have same couplings to quarks as type I and to leptons as in type II Type IV: Flipped model, Higgs bosons have same couplings to quarks as in type II and to leptons as in type I 4/8/4 DIS4 6

7 HDM Higgs Search for a heavier neutral (H) CP- even partner of 5 GeV light Higgs Probe the hypothesis of simultaneous presence of signals from both light (5GeV) Higgs and its heavier partner the first analysis of this kind! Production: gluon fusion, vector boson fusion (VBF) Decay: H WW* eν μν Selection: split into - jet and - jet channels Use neural network to separate signal from background jets has better S/B but worse NN separation Events / 5 GeV 4 3 L dt = 3. fb H"WW"e!µ! jets Data SM Higgs m Wjets Z/$*jets s=8 TeV =5 GeV h tt/wt/tq/tb WW/WZ/ZZ/W$/W$* SM (sys % stat) Events /.7 L dt = 3. fb H"WW"e!µ! jets Data SM Higgs m s=8 TeV =5 GeV h Wjets Z/$*jets tt/wt/tq/tb WW/WZ/ZZ/W$/W$* SM (sys % stat) Event fraction /.7.3. s = 8 TeV H"WW"e!µ! jets HDM m H =8 GeV HDM m h =5 GeV Total background NN output signific. 3-3 m T 3 4 & -prob.: 9 % m T signific. 3-3 NN output & -prob.: 6 % NN output Event fraction / s = 8 TeV H"WW"e!µ! jets HDM m H =8 GeV HDM m h =5 GeV Total background NN output 4/8/4 DIS4 7

8 HDM Higgs results No evidence found in the 35 3 GeV mass region Limits set in terms of cos(α) and mh Type- I: all quarks couple to only one Higgs doublet Type- II: /3 RH quarks couple to one HD, /3 RH quarks couple to the other HD cos(!).5 " L dt = 3 fb s=8 TeV HDM Type-I tan = H%WW%e$µ$ cos(!).5 ATLAS- CONF- 3-7 " L dt = 3 fb s=8 TeV HDM Type-II tan = H%WW%e$µ$ -.5 Exp. 95% CL Exp. 99% CL Obs. 95% CL Obs. 99% CL m H -.5 Exp. 95% CL Exp. 99% CL Obs. 95% CL Obs. 99% CL m H 4/8/4 DIS4 8

9 HDM results Observed exclusion limit (95% CL) for four types of HDM mode in terms of cos(β α), tan β parameter space Compared with expected exclusion limits for SM Higgs Boson Data are consistent with SM alignment limit cos (β- α)= to within - σ for all models ATLAS- CONF- 4-4/8/4 DIS4 9

10 Invisible Higgs Production: associated ZH, Z ll (l=e,μ) H decay: stable/long lived weakly interacting particles Selection: ptl> GeV, mll- mz <5 GeV, MET>9 GeV Limits are set in two scenarios: on invisible BR of a SM Higgs at mh=5 GeV: at 95% C.L. observed/expected limits are 65%/84% on production BR of a Higgs- like particle vs mh Events / 3 GeV 3 ATLAS s = 8 TeV,! L dt =.3 fb ZH ll inv. Data ZZ llνν (incl. τ) WZ lνll (incl.τ) WW, dilep., W, Z ττ Z " ee, µ µ W jets,multijet,semilep.top ZH ll inv.,br(h inv.) = BR(H!inv.) [fb] " s = 8 TeV, $ ATLAS L dt =.3 fb ZH ll inv. ZH,SM Observed 95% CL limit Expected 95% CL limit ± ± ZH 3 Data / Expected miss E T /8/4 DIS4 arxiv:4.344, submitted to PRL m H

11 Higgs and Dark matter Model extends SM to include weakly interacting massive particles (WIMPs) coupling to Higgs boson Dark matter- nucleon scattering as well as decay rate inferred from Higgs invisible decays ] [cm i "!-N DAMA/LIBRA (99.7% CL) CRESST (95% CL) CDMS (95% CL) CoGeNT (9% CL) XENON (9% CL) XENON (9% CL) LUX (95% CL) s = 7 TeV, Ldt = fb s = 8 TeV, Ldt =.3 fb h%& &, h%zz*%4l, h%ww*%l$l$, miss h%' ', h%bb, Zh%llE T ATLAS (95% CL) in Higgs portal model: Scalar WIMP Majorana WIMP Vector WIMP m! BR i Upper limit at 95% CL on the WIMP- nucleon scattering cross section in a Higgs portal model as a function of the mass of the dark matter particle. 4/8/4 DIS4 ) - ln!(br ATLAS- CONF- 4- Likelihood scan of the invisible branching ratio of the Higgs boson. s= 7 TeV, " Ldt = fb s= 8 TeV, " Ldt =.3 fb [ $, g, BR ] i h & $ $, ZZ*, WW*, % %, bb, miss Zh & ll E : T obs. exp. h & $ $, ZZ*, WW*, % %, bb : obs. exp.

12 h aa 4γ (NMSSM) Diphotons from a decays are highly collimated and result in a single EM cluster Selection: similar to h γγ but modified photon identification to detect photon pairs from Higgs decays Limits on prod BR for ma=,, 4 MeV ATLAS- CONF Events / GeV Data ( s= 7 TeV) Background Model (" /n dof =6./6) Signal (M =5 GeV, M = MeV) H Signal (M =5 GeV, M = MeV) H Signal (M =5 GeV, M =4 MeV) H A A A L dt=4.9 fb m!! (pp" H"4!) [pb] 95%CL limit on = 4 MeV Observed Limit Expected Limit ± ± m H m a 4/8/4 DIS4

13 Charged Higgs Charged Higgs H ± are predicted in several scenarios, with Higgs triplets, MSSM and HDM. SM doesn t have H ±, so its observation would indicate BSM H ± production and decay depends on mh ± compared to mt mh ± < mt mh ± > mt Top decay Light Charged Higgs Top Associated Production Heavy Charged Higgs 4/8/4 DIS4 3

14 Charged Higgs results Light Higgs (mh ± <mt), tt HbWb Events / GeV!.8 $ Ldt = 9.5 fb.6 s = 8 TeV Data True " Jet" misid Uncertainty m H = 3 GeV ( x ) B(tbH ) =.9% Light H Selection t! bh B - Data Observed CLs s = 8 TeV Expected ± " Ldt = 9.5 fb ± " tan! Median expected exclusion Observed exclusion 95% CL Observed " theory Observed " theory Expected exclusion Observed exclusion max s=8 TeV m h Ldt = 9.5 fb Data $jets m T m H m H Heavy Higgs (mh ± >mt) ATLAS- CONF- 3-9 Events / GeV! % Ldt = 9.5 fb s = 8 TeV Data True " Jet" misid Uncertainty m H = 5 GeV ( x ) tan($) = 5, MSSM m Heavy H Selection max h m T [pb]! H - -3 Data Observed CLs Expected s = 8 TeV ±! ±! Ldt = 9.5 fb /8/4 DIS4 4 " m H tan! max m h s=8 TeV Data Median expected exclusion Observed exclusion 95% CL Observed " theory Observed " theory Ldt = 9.5 fb m H $ jets

15 Light charged Higgs H ± cs Search for the light charged Higgs in top decays H ± jets, and leptons from second top Selection: e/μ and 4 Jets (of which b- tagged) High Missing Energy Look for a second peak in dijet mass, set limits on Br(t bh ) Eur. Phys. J. C73 (3) 465 Events / 5 GeV Events / 5 GeV ATLAS Simulation Before kinematic fit After kinematic fit s = 7 TeV SM tt H GeV s SM tt H = 7 TeV GeV Dijet mass ATLAS Simulation Dijet mass Events / 6 GeV ATLAS s = 7 TeV :! Ldt = 4.7 fb Data SM tt Non-tt SM with uncertainty b) 95% CL on B(t! H ATLAS s = 7 TeV B(H! cs) = % Ldt = 4.7 fb Limits at 95% CL: Expected Limit Expected ± " Expected ± " Observed Limit Dijet mass m H 4/8/4 DIS4 5

16 Doubly charged Higgs Appears in LR symmetric models, Seesaw Type II, Little Higgs Possible way to probe origin of neutrino masses at the LHC! Production: mostly pairs: H H Method: generic same- sign dilepton spectrum search pte>5gev,ptμ>gev,z- window Lepton pairs / GeV ATLAS! Ldt = 4.7 fb s = 7 TeV e ± µ ± Data Non-prompt Charge flips Prompt ± ± H L ± ± H L ± ± H L ± ± H L 5 GeV 3 GeV 35 GeV 4 GeV ± m(e µ ± ) ± ± m(h ) 4/8/4 DIS4 6 ) [fb] ± l ±! l ± ± )" BR(H H $(pp! H ± Observed limit: e ± e ATLAS % Eur. Phys. J. C7 () 44 Ldt = 4.7 fb s = 7 TeV $(pp! H $(pp! H H L L H R R ± ± ± ± ), BR(H! l l )= ), BR(H ± ± ± ±! l l )= Expected limit: e ± e ± Observed limit: µ ± µ ± Expected limit: µ ± µ ± Observed limit: e ± µ ± Expected limit: e ± µ ±

17 Search for FCNC in t ch, H γγ In SM, FCNC are forbidden at tree level, suppressed by GIM mechanism at higher orders Observation direct indication of new physics Selection: two photons (pt>4/3 GeV) tt bw ch bjj γγ: 4 jets, b- jet, top mass cuts tt bw ch blν γγ: e/μ, mt>3 GeV, jets, b- jet, top mass cuts Observed/expected limits at 95% CL: Br(t ch):.83/.53%, tch coupling.7/.4 ATLAS- CONF- 3-8 Events / 4 GeV 4 8 Hadronic selection Data SigSM Higgs (6.8 GeV)Bkg fit SM HiggsBkg nd Bkg ( order polynomial) L dt =.3 fb, "s = 8 TeV L dt = 4.7 fb, "s = 7 TeV S CL L dt =.3 fb, "s = 8 TeV L dt = 4.7 fb, "s = 7 TeV m!! Observed Expected ± $ ± $ Br(t! ch) 4/8/4 DIS

18 Conclusions Performed many different searches for extended BSM Higgs sector with ATLAS, however no evidence found. Limits have been set. Many analyses on full Run I data set are still to be completed. We now know where in the phase space to focus our efforts as we prepare for Run II. Further analysis still in progress. Looking forward to new exciting discoveries! 4/8/4 DIS4 8

19 BACKUP SLIDES 4/8/4 DIS4 9

20 Additional electroweak singlet ATLAS- CONF- 4- BR H,new /8/4 DIS4 " H / " H,SM =. s = 7 TeV: Ldt = fb s = 8 TeV: Ldt =.3 fb Combined h & % %,ZZ*,WW*,$ $,bb! =.! =. " H /" H,SM =.5! =.3! =.4 " H / " H,SM =.! =.5! =.6 EW singlet " H /" H,SM =5.! =.7 Obs. 95% CL Exp. 95% CL SM " H /" H,SM = µ H Observed and expected upper limits at 95% CL on the squared coupling, κ, of a heavy Higgs boson arising through an additional EW singlet, shown in the (μh, BRH,new) plane.! =.9! =.8! =.

21 MSSM simplified model Coupling scale factor Type I Type II Type III Type IV k V k u k d k l Regions of the (ma, tan β) plane excluded in a simplified MSSM model via fits to the measured rates of Higgs boson production and decays. The likelihood contours where ln Λ = 6., corresponding approximately to 95% CL (σ), are indicated for the data and expectation assuming the SM Higgs sector. ATLAS- CONF- 4- sin(β- α) sin(β- α) sin(β- α) sin(β- α) cos(α)/sin(β) cos(α)/sin(β) cos(α)/sin(β) cos(α)/sin(β) cos(α)/sin(β) - sin(α)/cos(β) cos(α)/sin(β) - sin(α)/cos(β) cos(α)/sin(β) - sin(α)/cos(β) - sin(α)/cos(β) cos(α)/sin(β) tan! s= 7 TeV, " s= 8 TeV, " Ldt = fb Ldt =.3 fb Combined h % $ $, ZZ*, WW*,, bb Simplified MSSM [& V, & u, & d ] Exp. 95% CL Obs. 95% CL /8/4 DIS4 m A

22 Cascade Higgs search g W W H H ± b g h Diagram showing the Higgs- boson cascade gg H W H` W W`h W W`bb. Phys. Rev. D 89, 3 (4) b Mass ± H ATLAS! Ldt =.3 fb s = 8 TeV ± ± ± ± ± ± H "W H "h W W "bbw W Expected Limits [pb] Mass ± H ATLAS! Ldt =.3 fb s = 8 TeV ± ± ± ± ± ± H "W H "h W W "bbw W 95% C.L. Upper Limits [pb] H Mass H Mass 4/8/4 DIS4