Transcript System Test results

QCD and Hadronic interactions
Recontres de Moriond-La Thuille 12-19 March 2005
Searches for Higgs in the MSSM
CP-conserving and CP-violating scenarios at LEP
P.Ferrari (CERN)
on behalf of the
LEP
experiments
-model introduction
-the CP-conserving MSSM
-the CP-violating MSSM
-2HDM
Pamela Ferrari
Recontres de Moriond ‘05
0
2 Higgs Doublet Models
Simplest extension of SM are 2HDMs
2
mW
ρ 2
~ 1 and no FCNC
mZ cos 2 θw
Two complex scalar field doublets Φ1 and Φ2, 5 scalar Higgses:
Real parts mix with  -> CP even scalars h0,H0
- Imaginary part -> CP odd scalar A0
- Two charged scalars H+-
Two production processes :
e-
Higgsstrahlung
Z0
e-
Pair-Production
A0
- shZ=sin2(b-a)sSMHZ
- sHZ=cos2(b-a)sSMHZ
- sHA=cos2(b-a)lsSMHZ
b =ratio of VEV of scalar fields
e+
Z*
Z*
h,H
e+
h
The type of 2HDM determined by the couplings of Φ1 , Φ2 to fermions:
- Only F1 couples to fermions 2HDM (I)
- F1 (F2) couples to down (up) type fermions 2HDM(II)
Pamela Ferrari
Recontres de Moriond ‘05
1
The MSSM
2HDM(II) are interesting since by adding supesymmetry
CP-conserving MSSM
CP-conserving MSSM is interesting since it provides framework for
unification of Gauge interactions and stability of universe at EW scale
mh <140 GeV after radiative corrections
to explain matter-antimatter asymmetry in universe we need
CP-violation >> than in SM
Justifies introduction of CP-violation in MSSM: can be done via
radiative corrections (in particular from 3rd generation s-quarks)
Pamela Ferrari
Recontres de Moriond ‘05
2
CP-violation in MSSM
Mass eigenstates and CP-eigenstates do not coincide:
H1,H2,H3 are mixtures of CP-even and CP-odd Higgs fields
Only CP eigenstates h,H
can couple to Z
But H1 is the
propagating particle
Lightest Higgs boson might have escaped
detection at LEP2: H1 might decouple
almost completely from the Z
Search for both H1Z and H2Z production
Pamela Ferrari
Recontres de Moriond ‘05
3
Experimental searches
b-tagging HZ




(H
(H
(H
(H
bb) (Z qq )
bb,tt ) ( Z nn )
bb,qq) (Z ee,mm)
tt ) ( Z qq), (H bb,tt ) ( Z tt)
ALEPH, DELPHI, OPAL & L3
data @ 91 GeV<s< 209 GeV
Interpreted in MSSM
CPC and CPV and 2HDM(II)
Flavour independent HZ


(H qq) Z
(H2H1H1 ) Z dominant when kinematically allowed
b-tagging pair production H2H1



(H2  bb) (H1 bb )
(H2  tt ) (H1 bb )
(H2 H1 H1  bbbb )((H1 bb )
Flavour independent H2H1 used only for 2HDM(II) scan

(H2  qq) (H1 qq )
Additional constraints

Z width, decay mode independent search for HZ, light Higgs from Yukawa production
Pamela Ferrari
Recontres de Moriond ‘05
4
MSSM CPC benchmarks
Traditional scans:
- No mixing: in stop sector
- mh max:
yields maximal bound on mhTH
- Large m: suppressed h-> bb
7 parameters: (Carena et al. hep-ph/9912223)
mtop= 179.3 GeV ( 178.04.3 GeV CDF & D0)
MSUSY sfermion mass at EW scale
m Higgs mixing parameter
M2 gaugino mass at EW scale
mg gluino mass
Xt= Stop mixing parameter
Ab=At= Xt +mcotb trilinear Higgs-squark coupling
New scans:
envisaged for final LEP combination but not yet done
Favoured by (g-2)m and Br(b->sg)
- No mixing ( 2TeV) reversed m sign motivated by (g-2)m
- mh-max+ with reversed m sign motivated by (g-2)m
- constrained mh-max reversed sign for At and Xt motivated by Br(b->sg)
Regions where Hadron colliders might have problems in detecting the Higgs
- gluophobic gg->h suppressed
- small aeff h->bb,tt suppressed
Pamela Ferrari
Recontres de Moriond ‘05
5
CPC mh-max scan
LHWG-Note/2004-01
2 calculations used:
 FeynHiggs 2.0: 2-loop diagrammatic
approach & OS scheme
S.Heinemeyer et al. hep-ph/0212037
 SUBHPOLE: 1-loop renormalization
group, MS scheme
M.Carena et al hep-ph/9912223
FeynHiggs is chosen:
Expected
exclusion
Pamela Ferrari
more accurate, conservative results
Recontres de Moriond ‘05
mh
(GeV/c2)
mA
(GeV/c2)
tanb
Obs
92.9
94.8
0.9-1.5
Exp
94.8
95.1
0.8-1.6
6
No-mixing & large m scans
LHWG-Note/2004-01
Large m
No-mixing
0.37<1-CLb<0.65
Nearly excluded
No-mixing
mh
(GeV/c2)
mA
(GeV/c2)
tanb
Obs
93.3
93.3
0.4-5.6
Exp
95.0
95.0
0.4-6.5
For mh~80 GeV and
tanb<0.7, mA<tt threshold:
A decays uncertain
hbb small
Pamela Ferrari
Recontres de Moriond ‘05
7
Did we miss the Higgs?
LHWG-Note/2004-01
No excess larger than 3 s:
 2 s @ mh~98 GeV
 2 s @ mh~115 GeV.
Recent interpretations:
M.Drees hep-ph/0502075
G.L. Kane et al. hep-ph/0407001
Explain this kind of “excess” within
 CP-conserving MSSM
 CP-violating MSSM
 2HDM
Pamela Ferrari
Recontres de Moriond ‘05
8
Example of new scans
OPAL Eur.Phys.J.C37:49-78,2004
Only OPAL data: exclusion will be larger for LEP combination
Large regions of the parameters space are excluded
Pamela Ferrari
Recontres de Moriond ‘05
9
CP-violating MSSM
Phases of At ,Ab and m~g introduce CP violation~ in the Higgs potential via
loop effects leading off-diagonal contributions to higgs mass matrix
Theoretically: argAu ≠0 most general case, can be motivated by Baryogenesis.
Size of CP violating effects proportional to:
4
m
Im(μAt )
2
MSP
 2t
2
v 32π 2mSUSY
benchmark: large argAu ≠0, large m, relatively small mSUSY
the CP violation increases with mt
Pamela Ferrari
Recontres de Moriond ‘05
10
CPX benchmark
Carena et al., Phys.Lett B495 155(2000)
mH+( GeV) m (GeV) mSUSY (GeV)
tanb
0.6–40
4–1000
2000
500
M2 (GeV)
|Aq| (TeV)
arg(Aq)
mg (TeV)
arg(mg)
200
1
90o
1
90o
EDM measurements of n and e fullfilled
Maximal CP violation
Feynhiggs and CPH are a priori equivalent:
Feynhiggs has more advanced one-loop corrections
CPH (CPV version of SUBHPOLE) is more precise at the two-loop level
In each parameter space point the most conservative result is used
All implemented in HZHA with ISR and interference between identical final
states from Higgstrahlung and boson fusion process
Pamela Ferrari
Recontres de Moriond ‘05
11
CPX scan
LHWG-Note/2004-01
No lower mH
1,2
limit
mt dependent 95%CL on tanb:
mt(GeV/c2)
Expected
tanb
Observed
tanb
174.3
>2.9
>3.0
179.3
>2.6
>2.7
183.0
>2.5
>2.5
mt=178.04.3 GeV CDF & D0
For heavy H2:
 H1HSM
 mH > 115 GeV
1
Pamela Ferrari
Recontres de Moriond ‘05
12
CPX scan
LHWG-Note/2004-01
Strong reduction of exclusion
increasing mt CP-violation:
for example 4<tanb<10, where
both H1Z & H2Z are open
No excess larger than 3s found
Pamela Ferrari
Recontres de Moriond ‘05
13
OPAL general 2HDM(II) scan
2HDM(II) have no constraint derived from SUSY:
h  bb is not dominant decay,e.g for a=0 BR(hbb/tt)=0  flavour-indep. searches
large regions of the parameter space cannot be exlcuded by LEP
light Higgs not ruled out
Signal generated with HZHA
hep-ex/0408097
Free parameters:
1 < mh< 130 GeV
3 GeV <mA< 2 TeV
a   p/2,  p/4,0
0.4< tanb <40
mH and mH kinematically unaccessible
Excluded rectangular region for
1<mh<55 GeV when 3<mA<63 GeV
But for mA> 63 values of mh down to 0
are still allowed !
No tanb exclusion independent of mh/mA
Pamela Ferrari
Recontres de Moriond ‘05
14
Conclusions
At LEP we have searched for Higgses in several extensions of SM:
CP-conserving MSSM
CP-violating MSSM
2HDM
No evidence of the presence of a signal has been found
Still there is room for the presence of a light Higgs:
In CP-violating MSSM
In 2HDMs
Some theoretical papers interpreting small data-background
discrepancy (about 2 s) in the context of specific CPC MSSM
scenarios ( require quite some tuning) as well as CPV MSSM and
2HMD.
Pamela Ferrari
Recontres de Moriond ‘05
15
Back-up
Pamela Ferrari
Recontres de Moriond ‘05
16
SM vs MSSM excess
The excesses at mh=98 & 115 GeV Observed in
MSSM are the same that where observed in the
SM searches:
mh~98 GeV 2.3 s excess 1-CLb= 2%
from all hZ channels
Not Compatible with a SM signal.
mh~115 GeV 1.7 s excess 1-CLb= 9%
from ALEPH hZ 4-jet channel
Compatible with a SM signal.
1-CLb gioves the Probability of a local fluctuation of background.
Probability that a fluctuation appears anywhere within a certain mass range
is given by:
1 - CLb ) Δ mass range)
mass resolution
Pamela Ferrari
Recontres de Moriond ‘05
17
mh max scans
mt=174.3,179,183 GeV
Pamela Ferrari
Recontres de Moriond ‘05
18
No-mixing
Pamela Ferrari
Recontres de Moriond ‘05
19
Useful searches for CPV MSSM
Pamela Ferrari
Recontres de Moriond ‘05
20
CPH vs FEYNHIGGS


The largest discrepancy occurs for large tanb where Feynhiggs
predicts a higher x-section for Higgstrahlung
Data/background discrepancy in intemediate tanb region:
due to excess at mh~98 GeV which is the mH2 mass in this region
Pamela Ferrari
Recontres de Moriond ‘05
21
CPX-phases
Exclusion decreases
With increasing
argAt,b (CP-Violation)
Pamela Ferrari
Recontres de Moriond ‘05
22
2HDM scan
Pamela Ferrari
Recontres de Moriond ‘05
23
2HDM scan tanb exclusion
No tanb exclusion independent
from mh and mA
Pamela Ferrari
Recontres de Moriond ‘05
24
Pamela Ferrari
Recontres de Moriond ‘05
25