Search for MSSM Higgs at LEP Haijun Yanggallatin.physics.lsa.umich.edu/~hyang/talks/mssm-lep.pdf ·...

Search for MSSM Higgs at LEP

Haijun YangUniversity of Michigan, Ann Arbor

PhysicsSeminarat Univ. of Michigan

February4, 2002

OUTLINEL�

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� Introduction of MSSM

� Main Backgrounds

� L3 Analysis Procedure

� LEP CombinedResults

� Conclusions

HaijunYang Searchfor MSSM Higgsat LEP 1

Intr oductionL�

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� Minimal SupersymmetricStandardModel

Two Higgsdoublets�� 5 Higgsbosons

3 neutral(h & H CP-even,A CP-odd),

2 charged Higgs.

� NeutralHiggs- Two ComplementaryProcesses

Higgsstrahlung Pair Production

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� Parametersof theMSSM

1. Ratioof two Higgsvacuumexpectationvalues:@(A4� �2. Massof A boson:B )3. Gauginomassparameter: C �4. Scalarfermionmass:B D5. Higgsinomassparameter: E6. Higgs-sfermiontrilinear coupling: F

� ThreeBenchmarkScenarios

B � MaximalG H F E +-,:@ � I J TeV

Minimal Mixing: No mixing in stopsectorG H F E +-,:@ � K large E


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Main BackgroundsL�

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Analysis ProcedureL�

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� 4-jet channel:hA V L M LWL MLPreselection`

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Step1. Preselection:To rejectlow multiplicitybackgrounds while keepinghigh signalefficiencies(b 90%).

Step2. Neural Network: Discriminant distri-butions are combinedin a neural net-work.

Step3. Final Discriminant: Neural networkoutputs are usedto construct final dis-criminantvariable.


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6. Longitudinal componentof the missing mo-mentum: z {B p|r'r s~}�� o�p|r � � � � m eji�x� Event 6 4-jet usingDURHAM algorithm

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� NeuralNetwork Inputs:

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�� B � B ) ��" �� NeuralNetwork Outputs:

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ALEPH DELPHI L3 OPALInte. Lumi. (ë�ìîí^ï ) 217 224 217 208

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Event DAQ Time :

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§ � �c�= 0.91, ¨ª©¬«N�® = 0.965, ¨ª©.«N_¯ = 0.359,° �i� = 90.68GeV,

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ALEPH DELPHI L3 OPALInte. Lumi. (¾À¿lÁ ® ) 217 224 217 205

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ConclusionsLV

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^ Morethan200_"`ba c datawerecollectedperexper-iment in the Year2000. In total d 700 _�`ea c werecollectedabove f g poleby eachexperiment.

R No significantevidenceof MSSM neutralandchargedHiggsareobservedup to h i 209GeV.

R NeutralHiggslimits with 95%C.L.

j k U lnmporq GeV, j s U lnmporl GeVtvuxw y

is excludedfr om 0.5to 2.4

R ChargedHiggslimits with 95%C.L.

j S T U z|{no~} GeV


Search for MSSM Higgs at LEP Haijun Yanggallatin.physics.lsa.umich.edu/~hyang/talks/mssm-lep.pdf ·...

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Transcript of Search for MSSM Higgs at LEP Haijun Yanggallatin.physics.lsa.umich.edu/~hyang/talks/mssm-lep.pdf ·...