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2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 1
MSSM Higgs Searches at LEP
Tord Ekelöf
Uppsala University
Sweden
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 2
What is the rational for supersymmetry?
SM has problems with quadratic divergencies (mass hiarchy problem)
Supersymmetry leads to coupling unification at high energy
Supersymmetry needed for superstrings->supergravity->unification of general relativity and quatum field theory
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 3
Introduction• SM One Higgs Field Doublet
– One physical Higgs H• Production
– Higgsstrahlung
– Vector boson fusion, small
• Decay H->bb, , W*W*...
• MSSM Two Higgs Field Doublets– Five physical Higgs h0 A0 H0 H+ H-
Z0e+
e-
Z0
H0 e+,
e-,
e+
e-
Z,W
Z,WH0
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 4
– MSSM free parameters• MSUSY Sfermion mass parameter at EW scale
SUSY Higgs mass parameter
• M2 SU(2) gaugino mass param at EW scale
• Xt Stop mixing term=At- tan, At trilinHt
• tan ratio between vacuum expectation values of Higgs field doublets
• mA A Higgs boson mass
• mg Gluino mass
– On tree level mh calculable from (mA,tan) and mh< mz. In one and two loop corrections to production cross-sections and branching ratios all free parameters are involved. Can make mh larger.
~
~
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 5
• MSSM Higgs production– h0
• Higgsstrahlung, SMsin2(-)
• Vector boson fusion, small
• Higgs pair production, SMcos2(-)
– A0
– Higgs pair production, SMcos2(-)
• h0 decay if 2mA<mh
– H0
• Higgsstrahlung if large, SMcos2(-)
– H+H-
• Pairproduction
e+
h0
e-
A0
h0
Z0
h0
Z0
e-
A0
h0
Z0
h0
Z0
e+
h0
A0
A0
e+
e-
e+,
e-,
Z,W
Z,W
Z0e+
e-
Z0
h0
e+
e-
Z0
H0
Z0
e+
e-
Z0H+
H-
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 6
• MSSM Higgs decay– h
• “standard” h0->bb, +-
• invisible, LSP/Majoron h0->101
0, JJ
• fermiophobic, 2HDM type I h0->• flavour independent, MSSM large h0->cc, ss, gg
– A • “standard” A0->bb, +-
• bosonic A0->Z0h0
– H+-
• “standard”, 2HDM if at LEP2 H+-->cs, • bosonic, 2HDM type I H+-->W*A0
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2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 7
• MSSM Bench Mark Scenarios
– Three points in the MSSM parameter space• plus general parameter space scan
Parameter 1. mhmax 2. no mixing 3. large general MSSM scan
unit GeVMSUSY 1000 1000 400 200 to 1000 -200 -200 1000 -500 to +500M2 200 200 400 200 to 1000Xt =At- tan 2MSUSY 0 -300 -2MSUSY to 2MSUSY
mg 0.8MSUSY 0.8MSUSY 200
mA 4-1000 4-1000 4-1000 4 to 1000tan 0.4-50 0.4-50 0.4-50 0.4 to 50
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 8
• 1. Mhmax scenario
• Designed to maximize the largest h0 mass value as function of tan with the aim to obtain the most conservative exclusion of tan, or , conversely, to possibly exclude MSSM by excluding h0 up to a maximal limit mh
max< 130 GeV, which depends on the exact value of mtop=174.3+-5.1 GeV.
• 2. No-mixing scenario• Same as mh
max but with no mixing in the stop sector to see the effect of mixing, mh
max<114 GeV
• 3. Large- scenario• In this scenario h0 (or H0) does not decay to b quarks in
certain parameter-space regions. Motivates flavor independent search. mh
max<108 GeV
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 9
Searches for h and A with data collected up to 209 GeV
• e+e-->Zh same as SM with production cross section reduced by sin2(-) and different decay BRs
• e+e-->hA has cross section proportional to cos2(-) with final states bbbb (dominates), +-bb and bb+-. Cross-section largest when mAmh.
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2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 10
LEP combined distribution of CLb in themh
max scenario
Along the mAmh diagonal Distribution of confidence (tan>20, cos2(-) 1) level in the (mA, mh) plane
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 11
LEP combined CLs in the mhmax scenario
Along the mAmh diagonal Distribution of exclusion
(tan>20, cos2(-) 1) in the (mA, mh) plane
mA>91.9(95.0) GeV mh>91.0(94.6) GeV observed expected observed expected
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 12
LEP combined exclusion plots in the mhmax
scenario in tan vs mh, mA and mH+ planes excluded region 0.4(0.5)<tan <2.4(2.6)
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 13
OPAL
Exclusion plots in the mhmax scenario
in tan vs mh planes for A, D and O
ALEPH DELPHI OPALmh> 89.6(91.7) 89.8(89.0) 79.3(85.1)tan> 0.7 0.49(0.54) 0.80(1.1)tan< 2.2 2.36(2.36) 1.7(1.9)
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 14
LEP combined exclusion for the no mixing scenario in the mA vs mh and the tan vs mh and mA planes
mh>91.5(95.0) mA>92.2(95.3) excluded 0.7(0.8)<tan <10.5(16.0)
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 15
OPAL
Exclusion plots in the no mixing scenarioin tan vs mh planes for A, D and O
ALEPH DELPHI OPALmh> 89.8(89.0) 80.9(85.6)tan> 0.5 0.59(0.72) 1.2(1.2)tan< 6.0 9.36(9.36) 3.8(4.6)
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 16
Production and decay of charged Higgs bosons
2HDMs predict s-channel pair-production of H+H-
with a tree-level cross-section which is fully determined by (mH+,s) and with H+H- decay into cscs, cs- and +-. No prediction for the BR(H+->+). In tree-level MSSM mH+>mW and mH+>mA.
Search for qqqq, qqp and p final states. Use equal masses constraint, acoplanarity, H+ zero spin, polarization (A,D) and cs identification (D).
/ /
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2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 17
Searches for charged Higgs, exclusion plots from of A, D, L & O
ALEPH DELPHI L3 OPALmH+<78.0(76.9) 73.8(75.4) 65.6(75.1) 72.2(74.5)
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 18
1-CLb for charged Higgs, ADO and ALDO and for different BR(H->)
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 19
Combimed searches for charged Higgs BR(H->) vs H+ mass, and cross-section limit
mH+>78.6(78.8)
Combined ALDO searches for charged Higgs, mass limit and cross-section limit
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 20
The L3 charged Higgs excessat 68 Gev
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 21
Comparison with charged Higgs hadronic decay massdistributions in A, D and O
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 22
Neutral Higgs flavour-independenthadronic decays
In both the SM and in the MSSM the neutral Higgsdecay predominantly into bb or +-.
In MSSM large- scenario and certain other 2HDMs Higgs decays into cc or gg can become predominant.
Same as SM analysis of e+e-->Z0H0, with H0->qq but without imposing requirement on the qq flavour. SM production cross-section and BR(H->had)=1 assumed.
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2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 23
Flavour-independent search for a neutral Higgs
ALEPH
ALEPHmHinv>109.4(109.8)
OPALmHinv>101.8(107.3)
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 24
Higgs decay into photon pairs - fermiophobic Higgs
In the MSSM h0 can decay into two photons via a quark or W-boson loop, but rates are low ~10-3.
In other models, like 2HDM Type I, h0 only couples to gauge bosons (i.e not to fermions) for certain choices of parameter values.
Analysis made assuming SM Higgs production cross-section and BR(Higgs->qq or l+l-) set to 0.
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2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 25
ALEPH mH>105.4
OPAL mH>105.5 (106.4)
L3 () mH>104.3 (104.4)L3 (,WW)mH> 104.8 (108.4)
Search for Higgs decaying into photon pairs
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 26
LEP combined data for h° -> 2
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 27
Higgs decay to invisible particles
e+e+->Z0h0 where Z0 ->qq or l+l- at SM cross-section
h0->101
0 , lightest neutralinos (R parity cons., LSPs) orh0->JJ , Majoronsorh0->other invisible (undetectable) particles, BR=100%.
Mmiss=recoil mass, Mvis=visible massM2
miss=s-2mZEviss/Mvis+mZ2
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2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 28
Searches for invisibly decaying Higgs
For BR(H->inv.)=100% ALEPH minv>114.1(112.6) DELPHI minv>113.0(110.7) OPAL minv>107.0(107.4)
For BR(H->inv.)=any DELPHI minv=112.7
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 29
LEP combined data for h°->invisibleLEP combined data for h°->invisible
2001-11-23 [email protected] Fourth Nordic LHC Physics Workshop Stockholm 22-24 Nov 2001 30
Conclusion NO MSSM/2HDM HIGGS FOUND
Combined results of the four LEP experiemnts MSSM mh
max mh>91.0 (94.6) GeV All limits at 95% CL
mA>91.9 (95.0) GeV 0.5<tan<2.4 (0.5<tan<2.6) excluded Charged Higgs m>78.6 (78.8) GeV Flavour blind Higgs m>112.9 (113.0) GeV Photonic Higgs m>108.2 (109.0) GeV Invisible Higgs m>114.3 (113.6) GeV
All results still preliminary