1 A (very) preliminary study of channel pp->h->ZZ->4mu via gg fusion with CMSSW Alessandro Giacobbe Cristina Botta Daniele Trocino Relatrice: Chiara Mariotti

2 Signal Torino, 27/03/2007 Leading Order Feynman Diagrams gg → h → ZZ→ 4mu

3 Backgrounds Torino, 27/03/2007 Zbb → 4mu tt → 4mu Leading Order Feynman Diagrams ZZ( ) → 4mu

4 Pythia: MC Generation of events Torino, 27/03/2007 gg → h → ZZ → 4mu ZZ → 4mu Zbb → 4mu tt → 4mu ( as we still don’t have more events generated by Comphep) ( 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 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 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 list of 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 resonances produced 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 at 5.,150.,5.,150. Default Kinematics Cuts The 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 at 5.,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 generated variables: 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 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 Background Transverse Momentum

14 Plots: Normalized and Weighted Torino, 27/03/2007 Generated Variables of Signal ( ) and Background

15 Plots: Normalized and Weighted Torino, 27/03/2007 Generated Variables of Signal ( ) and Background

16 Plots: Normalized and Weighted Torino, 27/03/2007 Generated Variables of Signal ( ) and Background Invariant Mass

17 Plots: Normalized and Weighted Torino, 27/03/2007 Generated Variables of Signal ( ) and Background

18 Plots: Normalized and Weighted Torino, 27/03/2007 Generated Variables of Signal ( ) and Background Angular Variables

19 Plots: Normalized and Weighted Torino, 27/03/2007

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: Pythia provides history of each generated event (production/decay chain) → it’s possible to verify how often μ-couples really come from a generated Z We get: for both h → ZZ → 4μ and ZZ → 4μ processes 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 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 events 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 Normalized plots

25 Torino, 19/03/2007 Kinematics differences Generated variables of signal gg-fusion, signal VV-fusion, background Normalized plots

26 Torino, 19/03/2007 Kinematics differences Generated variables of signal gg-fusion, signal VV-fusion, background Normalized plots

27 What to do: Torino, 19/03/2007 First of all… EXAMS !!!!!!!! Apply cuts: muons Pt muons pairs invariant mass ( Z cand. mass ) find new kinematics variables ( muons collinearity, …) Do the same study for final state: Do the complete simulation- Reconstruction: SIMU-DIGI-RECO