Preliminary analysis of ZHH events (2)

Michele Faucci Giannelli,Mike Green, Fabrizio Salvatore

Royal Holloway, University of London

UK

CALICE UK-SOFTWARE meeting, 24/01/2006

06/12/2005 Michele Faucci Giannelli 2

UK

Outline

• Why using ZHH events ?

• Events Generation & Detector simulation

• Events Reconstruction

• New Status of ROOTProcessor

• New results for Z→e+e-, Z→+- channels

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Why ZHH events ?

• Study of Higgs self coupling constant

• These events can also be used as benchmark events for several detector/PFlow studies:– ECAL & HCAL performances,

– Jet-finding algorithms, – b-tagging,– tracker, etc...

see: M.Battaglia et al, “Physics Benchmarks for the ILC Detectors”

(2005 ILC Workshop, Stanford, USA)

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• Use Pandora Pythia:– M(Higgs)=120 GeV & ECM = 500 GeV

• Used Mokka (V05-03) – detector model: D10scint

• Using MARLIN (V09-01)– Using Durham jet finding algorithm– Root output

Events Generation

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Status of ROOTProcessor

• All information of ReconstructedParticle Class for PFlow and ReconstructedParticle Collections stored in a ROOT file

• Added the truth (MCParticle Class) of MCParticle collection– Note: difficult to compare MC and Reco event-

by-event

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Z→+- analysis

Missing energy !!

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Z→+- analysis

• In order to understand the problem I looked at the number of particle in the “jet”. There are no muon in the low energy events (problem with muon id? Need to investigate)

Et<380 GeV Et>380 GeV

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Z→+- analysis

• Two request:– Etot > 380 GeV

– At least 2 “jets” must have less than 7 particle, those are identified as muons

• The remaining 4 jets are combined in all 3 possible ways, the combination that minimizeis used to calculate the Higgs mass

2h342

h122hh mmmmD

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Z→+- analysis

Some differences with the new cuts

The long tail will disappear later

Old New

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Z→+- analysis

Cut on D to eliminate the tails: D < XXX

Before After

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Fit of Z→+-

Z H

Last Time

After jet requirement and D cut

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Z→e+e- analysis

No missing energy

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Z→e+e- analysis

• Only one request:– At least 2 “jets” must have less than 7 particle,

those are identified as positron-electron pairs

• The remaining 4 jets are combined in all 3 possible ways– the combination that minimize

is used to calculate the Higgs mass

2h342

h122hh mmmmD

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UK

Z→e+e- analysis

Differences with the new cuts

The long tail will disappear later

Old New

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UK

Z→e+e- analysis

D < XXX

Before After

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Fit of Z→e+e-

Z H

Last Time

After jet requirement and D cut

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What has been done …

• New Processor in Marlin to produce an output in ROOT format is working fine

• Analysis of Z→+- and Z→e+e- using simple analysis, – mass plot are improved from December

• still to understand some problems (missing energy)

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… and what has still to be done

• Study the MCParticle, now in ROOT-tuple• Study other variables• Implement the muon reconstruction in Marlin, before

jet-finding algorithm– Understand the missing energy on muon events (using MC too)

• Reconstruct same events using different detector models– e.g. D09 – need to sort out calibration– D10scint with reduced size (see H. Videau’s talk at Vienna)

• Analyze events using different PF algorithms– Mark’s new PF ?– Chris/George’s new clustering ?