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Review of MSSM Higgs boson searches at LEP

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Review of MSSM Higgs boson searches at LEP

MSSM with CP conservation

MSSM with CP violation

Conclusions

3 July 2006

3 neutral Higgs bosons: h, H, A CP-eigenstates

at tree level, 2 parameters : tan, mA

hZ: low tan

large tan & mA

HZ: large tan & low mA

hA: interm./large tan & low mA

Higgsdecays: invisible, , ee, , , KK, cc, , bb, AA, hadrons

3 July 2006

mtopand the SUSY breaking parameters, assumed to be unified at some scale :

SU(2), U(1) gaugino mass terms unified at MGUT M2 at MEW

sfermion mass terms : unified at MEW Msusyat MEW

squark trilinear couplings : unified at MEW A at MEW

mixing parameter in the stop sector : X = A - cot

gluino mass and Higgs mixing parameter Mğand

Total: 8 parameters

mtop is measured ; M2, Msusy, Mğ, et X are chosen to define a “scenario”; tan and mA are free to vary (tan[0.4, 50] and mA[0.02, 1000] GeV).

NB: radiative corrections in the Feynman-diagrammatic approach (the most complete at two-loop order)

3 July 2006

- mhmax: sparticules at high mass (M2, Msusy, Mğ large), et X such that mh range is maximal (mtop=174.3 GeV: mh < 132.9 GeV).
LHC variants: 1) -, 2) - & X -X

- No mixing: counterpart of mhmax with X=0;mh range reduced (mtop=174.3 GeV: mh < 115.5 GeV).
LHC variant: 1) -, Msusy 2 Msusy

- Large : at least one Higgs (h, A or H) kinematically accessible (mtop=174.3 GeV: mh < 108.0 GeV) but Br(bb, ) vanish at large tan.
- Gluophobicscenario:ggh (strongly) suppressed tan, mA
- Small eff: Brh(bb, ) suppressedat large tan, moderate mA

3 July 2006

mtop

95%CL

99.7%CL

mtop=174.3 GeV,95% CL limits:

mh > 92.8 GeV, mA > 93.4 GeV

insensitive to mtop

tan exclusion : 0.7 – 2.0

sensitive to mtop

LHC variants:~identical mass limits, looser tan constraints

3 July 2006

unexcluded holes:

hAA, mA<3GeV, mh~80GeV

lack of searches at LEP2

mtop=174.3 GeV,95% CL limits:

mh, mA > 93.6 GeV (tan>0.7)tan exclusion : 0.4 – 10.2 (mA>3GeV)

very sensitive to mtop: scenario fully excluded at mtop=169.3 GeV (H within reach)

LHC variant: tighter mass and tan limits

3 July 2006

- excluded at 95% CL, not at 99.7% CL:
- hZ only remaining process
- BR(hbb) suppressed
- mh~108GeV close to the sensitivity of the flavour-blind searches
This strip grows with increasing mtop

theoretically forbidden

mtop=174.3 GeV or smaller:

scenario fully excluded at 95%CL

thanks to: H searches and flavour-blind analyses

3 July 2006

mtop=174.3 GeV , 95% CL limits:

mh > 90.5 GeV, mA > 96.3 GeV mh > 87.3 GeV, mA > 98.8 GeV

tan exclusion : 0.4 – 5.4 tan exclusion : 0.4 – 4.2

moderately sensitive to mtop

NB: h, A not degenerate in mass at large tan

3 July 2006

- 8 representative scenarios scanned with ADLO results on neutral Higgs boson searches at LEP1 & LEP2 ;
- improved sensivitivity thanks to H searches and flavour-blind analyses (esp. for low mtop)
- mass limits are set atlarge tan and ~ O(90) GeV in mh,mA
- tan limits are set by the LEP mhmax scenario :
tan exclusion (95%CL) : 0.7 – 2.0 for mtop=174.3 GeV

3 July 2006

3 neutral Higgs bosons: H1,H2,H3mixtures ofCP-eigenstates

at tree level, 2 parameters : tan, mH

H1H2: interm./large tan & low mH1

H1Z: low tan,

large tan & mH1

H2Z: low/interm. tan & low mH1

wrt CPC case:

more processes a priori, but some ZZHi couplings can be suppressed

similar decays, but Hj HiHi is enhanced

3 July 2006

The MSSM underlying parameters

- The usual eight MSSM underlying parameters:
- at tree level: tan, mH±
- through radiative corrections : mtop and the SUSY breaking parameters: M2, Msusy, Mğ, andAt,b

- two CPV phases : arg(At,b) and arg(Mğ)

low Msusy, large and arg(At,b)~90o

the CPX scenario:

Msusy=500GeV, =4Msusy=2TeV, |At,b|=Mğ=2Msusy=1TeV,M2=200GeV andarg(At,b)=arg(Mğ)=90o

+ 10 variants to study the dependence with arg(At,b), and Msusy.

NB: radiative corrections in the renormalization group and Feynman-diagrammaticapproaches(presently at the same stage of developpement)

3 July 2006

60°

CPC !

0°

90°

slight excess of data

lack of sensitivity

Phases ~90°:H1Z suppressed

large tan: H1H2

interm.tan: H2Z, esp. H2 H1H1

3 July 2006

2TeV

1TeV

4TeV

At intermediate tan:

=1TeV: two processes left

=2TeV: one process left

=4TeV: no process left

3 July 2006

174.3GeV

169.2GeV

179.4GeV

At intermediate tan:

H1Z, H2Z and H1H2 suppression gets stronger with increasing mtop

3 July 2006

CP-violating MSSM scenarios, conclusions:

- 11 representative scenarios scanned with ADLO results on neutral Higgs boson searches at LEP1 & LEP2 ;
- Significant effects require arg(At,b)=90°,135°, mtop174GeV, and |At,b|/ Msusy2 8 ;
- CPV = redundancy lost reduced sensitivity of LEP at intermediate tan down to the lowest massesNo absolute mass limits!
- tan limits are set by the CPX scenario :
tan > 2.9 (95% CL) for mtop=174.3 GeV

- Results are qualitatively the same in the renormalization group and Feynman-diagrammatic approaches.

3 July 2006

From the neutral Higgs boson searches at LEP applied to a set of representative MSSM scenarios :

- If CP is conserved in the Higgs sector:
- absolute mass limits around 90 GeV in mh,mA;
- low tan region not favoured (0.7 – 2.0 excluded in theLEP mhmax scenariofor mtop=174.3 GeV).

- If CP is not conserved in the Higgs sector:
- No absolute mass limits (at intermediate tan) !
- low tan region still not favoured (tan<2.9 excluded in theCPX scenariofor mtop=174.3 GeV);
- Calculations of radiative corrections not yet as complete as in the CP-conserving case.

3 July 2006

Higgsstrahlung

Pair-production

(+ WW, ZZ fusion)

Yukawa production

Higgs boson searches at LEP:

- Direct searches :
- Only 3 production processes
- Almost all decays can be exploited
- model-independentconstraints on x Br
- model scans : SM, MSSM, 2HDM

- Indirect constraints through EW precision measurements

In this talk: SM + MSSM neutral Higgs boson direct searches

published in April 2006

3 July 2006

EW precise measurements:

MH ≤ 175 GeV (95% CL)

Direct searches :

MH ≥ 114.4 GeV (95% CL)

MH [115,118] GeV ?

(status as of spring 2006)

3 July 2006

LEP results:

New physics scale

3 July 2006

dominant decays : direct decays in bb or

H1Z

H2H1

3 July 2006

non dominant decays : the example of the H2H1H1 cascade

H2Z

H2H1

3 July 2006

The gluophobic and small scenarios

gluo. scen.

small

Br(MSSM)/ Br(SM) predictions

NB: tthttbb and WW fusion channels enhanced

NB: h channel unsuppressed

3 July 2006

weaker exclusion

weaker exclusion

CPH

FeynHiggs

more one-loop and two-loop order corrections in FeynHiggs

phase dependence more complete in CPH than in FeynHiggs

3 July 2006