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A (very) preliminary study of channel pp->h->ZZ->4mu via gg fusion with CMSSW. Alessandro Giacobbe Cristina Botta Daniele Trocino. Relatrice: Chiara Mariotti. Signal. gg → h → ZZ→ 4mu. Leading Order Feynman Diagrams. Torino, 27/03/2007. Backgrounds. ZZ( ) → 4mu. Leading - PowerPoint PPT Presentation
Citation preview
1
A (very) preliminary study of channel
pp->h->ZZ->4muvia gg fusion with CMSSW
Alessandro GiacobbeCristina BottaDaniele Trocino
Relatrice: Chiara Mariotti
2
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
4
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 :
5
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
6
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
Torino, 27/03/2007
7
The FourMuFilter
Torino, 27/03/2007
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.
8
Torino, 27/03/2007
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
9
Pythia kinematic cuts (1)
Torino, 27/03/2007
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
10
Pythia kinematic cuts (3)
Torino, 27/03/2007
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
11
Pythia kinematic cuts (2)
Torino, 27/03/2007
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
12
Torino, 27/03/2007
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
13
Plots: Normalized and Weighted
Torino, 27/03/2007
Generated Variables of Signal ( ) and BackgroundGeVmh 190
TransverseMomentum
14
Plots: Normalized and Weighted
Torino, 27/03/2007
Generated Variables of Signal ( ) and BackgroundGeVmh 190
15
Plots: Normalized and Weighted
Torino, 27/03/2007
Generated Variables of Signal ( ) and BackgroundGeVmh 190
16
Plots: Normalized and Weighted
Torino, 27/03/2007
Generated Variables of Signal ( ) and BackgroundGeVmh 190
Invariant Mass
17
Plots: Normalized and Weighted
Torino, 27/03/2007
Generated Variables of Signal ( ) and BackgroundGeVmh 190
18
Plots: Normalized and Weighted
Torino, 27/03/2007
Generated Variables of Signal ( ) and BackgroundGeVmh 190
Angular Variables
19
Plots: Normalized and Weighted
Torino, 27/03/2007
GeVmh 190 GeVmh 250
GeVmh 500
20
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
21
Torino, 19/03/2007
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)
22
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
23
Torino, 19/03/2007
Weighted plots: expected eventsGeVmh 500
Generated variables of signal gg-fusion, signal VV-fusion, background
24
Torino, 19/03/2007
Kinematics differences
Generated variables of signal gg-fusion, signal VV-fusion, background
GeVmh 500
Normalized
plots
25
Torino, 19/03/2007
Kinematics differences
Generated variables of signal gg-fusion, signal VV-fusion, background
GeVmh 500
Normalized
plots
26
Torino, 19/03/2007
Kinematics differences
Generated variables of signal gg-fusion, signal VV-fusion, background
GeVmh 500
Normalized
plots
27
What to do:
Torino, 19/03/2007
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