Search for Non SM Higgs Bosons at LEP

Transcription

1 Search for Non SM Higgs Bosons at LEP 2HDM Higgses Photonic Higgs Invisibe Higgs Charged Higgses MSSM Higgses Aura Rosca Humbodt University Berin DESY-Zeuthen Seminar 13 June 2001

2 The LEP Acceerator

3 The four LEP Detectors

4 LEP II Data Taking E cm Period (GeV) Luminosity s 1 (pb ) ~ : ~ 475/pb. exp : ~ 200/pb. exp. at energies up to 209 GeV Coected at LEP2: 2.9 fb -1

5 Higgs Mechanism in the SM The Higgs mechanism is the way we know to give masses to partices in the Standard Mode. One compex scaar doubet: = Scaar potentia: + 0 m 2 H V( 2 < v 2 ) 0,, = v 2 = ( 2 v 2 + 2G = F ) + 2-1/2 is unknown 2, _ G F = + ) = 2, the Higgs > v (1) x 10 5 GeV -2 mass is unknown! v = 246 GeV No a priori reason to introduce ony one singe Higgs doubet!

6 Two Higgs Doubet Modes (2HDM) Minima extension of the SM mode: two Higgs doubets Five physica Higgs bosons: two neutra CP-even scaars ( H 0 and h 0, m ); a neutra CP-odd scaar ( ); a charged pair ( ± H > m A 0 h H ). Six free parameters (no CP vioation and no additiona partices): four Higgs masses; tan, the ratio of the vacuum expectation vaues of the two Higgs fieds;, mixing ange in the CP-even sector. Higgs coupings contro Higgs production and decay Higgs fermion coupings: restricted, to avoid FCNCs 2HDM (I): ony one doubet coupes to fermions. 2HDM (II): one Higgs doubet coupes to the down-type fermions and the other doubet coupes to up-type fermions.

7 h 0 Higgs-Strahung 2HDM Production Mechanisms (1) Vector boson fusion 2 SM hz hz = sin ( (argest at sma tanβ 1.4) hz 2 = sin ( SM hz Pair production 2 SM hz ha = cos ( (argest at tan β > 15)

8 2HDM Production Mechanisms (2) H 0 Higgs-Strahung A 0 Pair production hz 2 = cos ( SM hz ha 2 = cos ( SM hz H ± f(e,m ) + = H H - cme H Pair production

9 Higgs Decay in 2HDM h 0 A 0 H ± standard h favour independent h bosonic h invisibe h standard A standard H bosonic H bb, ττ cc, ss, gg * γγ, WW, A A ~~ 0 0 χχ JJ 1 bb, 1, * + + ττ cs, τυ τ 0 W A 0 0

10 Standard Mode Processes at LEP e e + + e e qq ( pb) + e e qq ( γ ) ( pb) qq( s / s > 0.85) + + e e W W qqqq ( 1-15 pb) + e e ZZ qqqq (1 pb) search sensitivity (0.1-1 pb)

11 Genera Search Strategy Cut optimisation Fina discriminant Topoogica and kinematica variabes B-tag variabes Mass variabe Neura Net Fina discriminant Cacuation of signaness estimator and C. L.

12 Favour Independent Searches No evidence for Higgs mass imits on m H (SM) or excusion contours in(m A, tan β), (m, tan β) h panes (MSSM) Dominant decay modes H,h bb, A bb coupings g HZZ, ghzz, ghaz are fixed to vaues predicted by SM and benchmark scenarios of constrained MSSM Mode dependent interpretations of search resuts In 2HDM h bb,a bb can be suppressed ( h cc,gg and A cc,gg are enhanced) g HZZ, ghzz, ghaz are different from those in SM and MSSM benchmark scenarios Motivation for favour independent Higgs search and mode independent interpretation of resuts

13 h Favour Independent Searches: Signa Topoogies qq, gg h qq, gg h qq, gg h qq, gg Z qq Z υυ Z ee,µµ Z ττ Channes: 4-jet Missing energy Leptonic Tau use SM anayses, without b-tag Aeph, Opa deveop new dedicated anayses for the 4-jet channe. 0 Combine with the standard (b-tagged) searches for h and A 0 + bb, ττ Treatment of the overap among favour-independent and standard searches: For each parameter space point, that anaysis providing the best expected C.L. is chosen.

14 2HDM Parameter Scan Tree eve coupings of neutra Higgs reative to the SM vaues: hcc: cos 0 α 0 sinα h bb: sinβ cosβ 0 0 A cc:cot β A bb:tanβ A scan over a broad range of masses and on both tanβ and α is required in order to extract excusion imits. Reduce the number of parameters to scan 4, set m and m H 0 H ± to a constant outside the kinematicay accessibe region; resuts are provided for each point in the (m space. h,m A, tanβ, α) Covered parameter space: 1 mh 100 GeV, in steps of 1 GeV; 5 ma 100 GeV, in steps of 1 GeV; 100 ma 500 GeV, in steps of 5 GeV; 0.5 ma 2 TeV, in steps of 0.5 TeV; tan β 58, in steps of 1 inb α = 0, - π / 8, - π / 4, - 3 π / 8 and - π / 2

15 Favour Independent Excuded Regions (1) A fixed (m,m, α) point is h A excuded at 95% C.L. if it is excuded for a scanned vaues of tanβ Data sets: s = m, 183,189 GeV Z Externa constrain from the width of the Z boson.

16 Favour Independent Excuded Regions (2) α independent scan of m,m and tan h A β

17 Mode-independent Interpretations Mode independent imits can be given for the cross section of the process: ee h Z Resuts are expressed in terms of the cross section scae factor, ξ 2 : σ hz = 2 ξ σ Mass ower imit on a Higgs boson decaying hadronicay with BR(h hadrons) = 1. SM

18 Decay Mode Independent Searches: Aeph Resuts 4-jet data and MC m H > GeV(exp.109.8GeV) Cross section scaing factor

19 Decay Mode Independent Searches: Opa Resuts 4-jet data and MC m H > GeV(exp.107.3GeV)

20 Decay Mode Independent Searches: Fina variabe: L3 Resuts 5C M h g / g SM hzz HZZ = 1 BR(h hadrons) = 1 m H > GeV (exp GeV)

21 Photonic Higgs A number of different modes aow for the Higgs to decay into two photons; Rare in SM where process occurs via oops of charged partices and is at the eve of 0.1% for a Higgs with the mass of 90 GeV; Severa modes (2HDM, anomaous coupings, etc.) can have fermiophobic Higgs bosons.

22 Fermiophobic Decays Suppressed coupings between Higgs boson and fermions; In 2HDM(I), choice of parameters can suppress fermionic coupings. g hff cos chosen to be cos h decays into bosons (fermiophobic) 2 SM widths, but zero fermionic BRs Branching Ratio h dominates for m < h * h WW dominatesfor m h m h 90 GeV > 90 GeV

23 Photonic Higgs: Signa topoogies h γγ h γγ h γγ Z qq Z υυ Z ee, µµ, ττ Channes: Hadronic Missing energy Leptonic high mutipicity ow mutipicity arge visibe energy missing energy ow mutipicity 2 eptons 2 energetic photons 2 acopanar photons 2 photons M recoi M M M M M Z recoi Z recoi Z

24 Photonic Higgs: Resuts from L3 Observed data: 62 events s = GeV SM background: 71.1 events Potentia signa: 32.9 events (m h = 105 GeV, BR = 1) E γ = GeV M M s = 205 GeV = GeV = 87.4 GeV γγ recoi E γ = GeV

25 Photonic Higgs: Resuts from L3 Upper imits on assuming SM production cross section: BR(h m fermiophobic h > GeV

26 Photonic Higgs: Other Resuts Upper imits on BR(h assuming SM production cross section m fermiophobic h > GeV m fermiophobic h > GeV

27 Photonic Higgs: LEP Combined Resuts Di-photon Invariant Mass Upper imits on BR(h assuming SM production X-section m fermiophobic h > GeV

28 Fermiophobic Decays Decay 0 Search channes: * Combined resuts on fermiophobic Higgs incuding h 0 * WW L3 h 0 Z 0 * WW Z qqqq qqqqqq qq qq Tq qqqq + exp.m h,ww h > GeV

29 Invisibe Higgs Invisibe decays can occur in different modes: MSSM with non universa gaugino masses h χ χ (R parity conservation, LSPs) 1 Modes with mojorons h 0 JJ 1 Anaysis assume SM Higgs production cross section and BR( h 0 invisibe )=1. Resuts are given in terms of upper imits on 2, ξ 2 = σ(e + e 0 0 h Z ) BR(h + σ(e e H 0 SM invisibe) 0 Z )

30 Invisibe Higgs: Signa Topoogies Not searched for h χχ h χχ h χχ Z Channes: qq Z ee,µµ Z υυ Hadronic Leptonic Large missing energy Two acopanar jets or eptons Kinematic constraints: M M and M M ff Z miss h

31 Invisibe Higgs: Dephi Resuts Hadronic channe data and MC m invisibe h > GeV (exp.110.7gev)

32 Invisibe Higgs: Other Resuts m invisibe h > GeV (exp.112.6gev) m invisibe h > GeV (exp.107.4gev)

33 Charged Higgs Searches In 2HDM(II) In 2HDM(I) Assumption of: + + BR(H qq) + BR(H + ) = 1 Search channes: Dominant decay mode at high H ± W BRs depend on tan and ± * A 0 tan, Opa P = m m H A H + H qqqq Additiona search channes H H + + H H qq + (c.c.) H + H W + A 0 W qqbbqqbb * * A 0 WW rejection: difficut to reject H + H W + * A 0 W A Ebqqbb, = e, * 0 H + W + * A 0, H

34 Charged Higgs in 2HDM(II): Signa Topoogies H cs H cs H τ υ τ H + cs H + τ + υ τ H + τ + υ τ Channes: Hadronic Semi-eptonic Leptonic high mutipicity high mutipicity ow mutipicity arge visibe energy ow visibe energy visibe energy, acoinearity mass reconstructed mass reconstructed mass is not reconstructed from the four jets from the two jets

35 Charged Higgs in 2HDM(II): L3 Resuts Higgs reconstructed mass: 4-jet channe Higgs reconstructed mass: semieptonic channe

36 Charged Higgs in 2HDM(II): L3 Resuts m = H 68 GeV BR(H τυ) = σ excess observed in the data

37 Charged Higgs Search in 2HDM(II): LEP Combined Resuts 1 CL b pot for A+D+O 1 CL b pot for A+D+L+O The L3 excess is seen aso in the combined pot for the hadronic channe.

38 Charged Higgs: LEP Combined Resuts Excuded region in the + pane BR(H τυ + ) vs m H Lower imits at 95% C.L. on charged Higgs mass BR( )=0 BR( )=1 BR( )=0.4 Observed Expected

39 Charged Higgs Search in 2HDM(I): Opa Resuts Opa excuded regions at 95% C.L. in the ( m, m ) pane H A

40 Constrained Minima Supersymmetric Standard Mode 2HDM (II) Production cross sections and branching ratios depend on the mode parameters: at tree eve: tan radiative corrected: M SUSY, m h,m (or 2 m h and m A, µ, A,tanβ,m Interpretations depend on the vaues assumed for these parameters and on the order of the cacuated radiative corrections. ) A, m ~ g

41 CMSSM Higgs Searches At tree-eve: mh < mz < m H, cacuabe from (m, tan β) A In one and two oop corrections to production cross-sections and branching ratios a free parameters are invoved; Sti: m <130 GeV h New topoogies h bb h bb A bb A ττ +

42 MSSM Searches: Resuts from L3 Fina Discriminant High B-tag=0.6 High Discriminant=0.98 m + m = GeV h A

43 Benchmark scans: No stop-quark mixing m~ g = 800GeV scan over: 0.4 < tan < 50, MSSM Scenarious Max- m h : same as before but X t(a) = 2M SUSY Large- : choice of parameters such that h bb is not dominant M M m SUSY = 1TeV, M = 200GeV, = 200GeV, X (A) = 0, 4GeV< m SUSY A < t 2 1TeV = 400GeV,M = 1TeV, X (A) = 300TeV, ~ g t = 200GeV,4 m 2 = 400GeV, A 400GeV.

44 Recent Progress in Theory Fu two-oop cacuations of m h in the MSSM (Weigein, Heinemeyer, Hoik hep-ph/ ) m h No mixing and max- scenarios One-oop renormaisation-group improved cacuation (Carena,Quiros,Wagner Nuc.Phys. B461 (1996) 407. µ Large- scenario

45 No-mixing Scenario:LEP Combined Resuts Non-excuded region: h 0 m m Z h A 0 BR(A > 65 GeV < 40 GeV A A domin ates 0 0 bb) suppressed 0 Z m h > > 0 m A tanβ exc. Observed Expected

46 Max- h Scenario: LEP Combined Resuts tanβ m h > > m A tanβ exc. Observed Expected

47 Large- Scenario: LEP Combined Resuts m h < 108GeV Non-excuded region where BR(h 0 bb) is suppressed (favour independent anayses can hep)

48 Genera MSSM scans Opa, Dephi and Aeph investigated in more detai the MSSM parameter space: Do the imits of the standard MSSM scenarios hod when mixing parameters and SUSY masses are not fixed?

49 Covered Parameter Space Parameter m A (GeV) tan M SUSY (GeV) M 2 (GeV) (GeV) Scan 20 to to to to to 500 Benchmark 4 to to and and and 1000 X -2 to 2 0 and 6 t 2-oop Higgs boson masses, cross section and branching fractions; Database with cross sections and branching ratios

50 Genera MSSM Scan: Resuts A given (m h, m A ) combination is excuded if for a SUSY parameter sets the excusion C.L. is arger than 95%. m A > 87GeV m h > 86GeV

51 CP-vioation in 2HDM CP parities of neutra Higgses may be mixed by radiative effects due to CP-vioating interactions of Higgs bosons to top and bottom quarks; h,h and h Three neutra Higgs bosons ( ) with undefined CP properties; Modified Yukawa coupings to t- and b-quarks; Due to the modified coupings, the excusions quoted for CP-conserving MSSM might be weakened in the CPvioating scenario.... work in progress...

52 Summary No 2HDM Higgs has been found; Limits were presented for favour independent Higgs searches, fermiophobic Higgs, invisibe Higgs, charged Higgs and neutra Higgses of the MSSM; Work continues on MSSM no-mixing and argescenarious, the L3 H + excess, H W * A 0, h A A µ (Opa), MSSM parameter scan (Dephi)