A (very) preliminary study of channel pp->h->ZZ->4mu via gg fusion with CMSSW

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A (very) preliminary study of channel

pp->h->ZZ->4muvia gg fusion with CMSSW

Alessandro GiacobbeCristina BottaDaniele Trocino

Relatrice: Chiara Mariotti

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Signal

Torino, 27/03/2007

LeadingOrder

FeynmanDiagrams

gg → h → ZZ→ 4mu

)190(

83.1

GeVm

fb

h

)500(

53.0

GeVm

fb

h

)250(

62.1

GeVm

fb

h

3

Backgrounds

Torino, 27/03/2007

• Zbb → 4mu

• tt → 4mu

LeadingOrder

FeynmanDiagrams

fb4106.2

fb31069.5

• ZZ( ) → 4mu

fb8.17

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Pythia: MC Generation of events

Torino, 27/03/2007

5

1

genN

Lweight

200000genN• gg → h → ZZ → 4mu

• ZZ → 4mu

• Zbb → 4mu

• tt → 4mu

LNexp

200000genN

200000genN

1800000genN

(as we still don’t have more events generated by Comphep)

160 fbL

(more events for a better study of the signal)

We work with the expected Luminosity of the first 2 years :

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CMSSW: what we need to know

Torino, 27/03/2007

• used to configure cmsRun at run time

• tells which data to use

• modules to run (all loaded at beginning of the job)

• parameters to set

• component of CMSSW code

• can be plugged into cmsRun

• it is called for every Event according to the path statement

• 6 differet types (Source,EDProducer, EDFilter, EDAnalyzer, EDLooper, OutpuModule)

• configured through *.cfg using modul-specific ParameterSets

MODULE*.CFG

• The overall software, called CMSSW, is build around a Framework, an Event Data Model (EDM) and services need by the modules that process data

• Only one executable : cmsRun

• Many plug-in modules run algorithms: the same for detector and MC data

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CMSSW: how it works

• Events are processed by passing the event through a sequence of modules

• the module can get data from the Event and put data back to the Event (not every module)

• each module can “talk” to the others only through the Event

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The FourMuFilter

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filtgenNN '

To be accepted the event must have in the final state:at least 4 mu, 2 positive and 2 negative, with Pt > 3 GeV,|η| < 2.5.

A Filter is a module that we used to apply cuts in generation.

Warning:

If the Event doesn’t satisfy the condition it won’t be automatically rejected. To have in output only filtered events you need to specify it in the PooloutModule.

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The FourMuFilter (2)

• gg → h → ZZ → 4mu

• ZZ( )→ 4mu

• Zbb → 4mu

• tt → 4mu

67.0filt79.0filt80.0filt

GeVmh 190

GeVmh 500GeVmh 250

42.0filt

003.0filt

02.0filt

GeV

• In the next days our filter will be send to Filip Moortgat in order to include it

in the next MC production

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Pythia kinematic cuts (1)

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Apart from standard settings that we include in the listof pythia cards ( such as the choice of the partonic functions,or the swich on of parton shower and QED bremsstrahlung),

we also introduce the following Kinematics cuts (that behave like a pythia inner filter) :

• CKIN(45) - CKIN(48) : (D = 12., -1, 12., -1) range of allowed mass values of the two secondary resonancesproduced in a 2->1->2 process like gg->h->ZZ

• CKIN(41) - CKIN(44) : (D = 12., -1, 12., -1) range of allowed mass values of the primary resonances

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Cuts set at5.,150.,5.,150.

Default Kinematics

CutsThe situation is the same.

We chosed to let this setting as it seems to be the

standard way.GeV

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Default Kinematics

Cuts

Cuts set at5.,150.,5.,150.

Useless generated events.We will surely cut this peack coming from μ generated by

virtual photons.GeV

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Analysis of the generatedvariables: the FourMuAnalyzer

Invariant Mass:•all possible muons pairs•muons pairs coming from Z → lower values of (in this way we selected candidate Z)•ZZ pairs

221 )( ppM z

Transverse Momentum:•pt of all muons•max, second, third, min pt of muons•pt of all Z

Angular Variables:•pseudorapidity of muons and Z•theta between two muons with same charge•theta between two muons from Z•Theta between two candidate Z

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Plots: Normalized and Weighted

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Generated Variables of Signal ( ) and BackgroundGeVmh 190

TransverseMomentum

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Invariant Mass

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Angular Variables

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GeVmh 190 GeVmh 250

GeVmh 500

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How well do we “reconstruct” Z’s?The FourMuTruth

Torino, 19/03/2007

Z candidates ↔ μ+μ- couples nearest to Z mass

To measure how much this method works, we define two efficiencies:

generated events total#

s Z'selected- well2 with events #evt

s Z'generated #

s Z'selected- well#Z

Pythia provides history of each generated event (production/decay chain)

→ it’s possible to verify how often μ-couples really come from a generated ZWe get: 97.0Z

for both h → ZZ → 4μ and ZZ → 4μ processes

96.0evt

Main inefficiency cause: photons emission in final state

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How well do we “reconstruct” Z’s?The FourMuTruth

Pythia also provides information about all generated particles (E, p, η …)→ it’s possible to access “true” data (i.e. generated with MC) and

compare them to “reconstructed” data (i.e. from selected μ-couples)

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Higgs produced via VV Fusion

Torino, 19/03/2007

• VV → h → ZZ → 4mu

)190( GeVmh

)500( GeVmh

fbp 62.0

80.0filt

71.0filt 200000genN

fbp 16.0 200000genN

Aims:• compare Pythia-Phantom for VV-fusion

• (attempt to) separate VV-fusion signal from gg-fusion one

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Weighted plots: expected eventsGeVmh 500

Generated variables of signal gg-fusion, signal VV-fusion, background

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Kinematics differences


GeVmh 500

Normalized

plots

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GeVmh 500

Normalized

plots

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GeVmh 500

Normalized

plots

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What to do:

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First of all… EXAMS !!!!!!!!

Apply cuts: muons Ptmuons pairs invariant mass (Z cand. mass)find new kinematics variables(muons collinearity, …)

Do the same study for final state: e22

Do the complete simulation-Reconstruction: SIMU-DIGI-RECO

Documents

A (very) preliminary study of channel pp->h->ZZ->4mu via gg fusion with CMSSW