Physics page

This page is intended to collect information regarding physics analysis and performance studies of people working in Working Package 1 (WP1) of EUROPE EGYPT NETWORK FOR PARTICLE PHYSICS, (EEPN2). Here we collect links to material important for physics studies. Work is organised in close contact with the "Higgs to 4 leptons analysis", "Zprime to 2 leptons analysis", "Wprime to muon and MET analysis", "Excited muon anaysis" and corresponding PAG upgrade WGs.

Meetings biweekly on Tuesdays 11-12 AM. Agenda on indico.

Coordinator Nicola De Filippis <Nicola.Defilippis@ba.infn.it>. Deputy Ahmed Ali Abdelalim <ahmed.ali.abdelalim@cern.ch>.

WP1 mailing list <WP1-EEPN2@cern.ch>.

Physics channels

H to ZZ to 4 lepton

  • final states: 4e, 4mu, 2e2mu
  • Tutorial at CMS DAS school: here

Z' (Zprime) to 2 lepton

Contact person: Sherif Elgammal , I am already involved in this study since 2006, publications.

Grand unified theories (GUT) suppose that strong and electroweak interactions can be described by a simple gauge group, at very high energies E > EGUT, where EGUT is defined as the energy where the three gauge coupling constants of the SM gauge groups become equal. H. Georgi and S. L. Glashow have shown, in 1974, that minimal simple group which can contain the SM gauge groups is SU(5) --> SU(3)c × SU(2)L × U(1)Y , where SU(3)c is the gauge group of the strong interaction. The precision measurements at LEP and SLC experiments prove that the three gauge coupling constants do not meet at one point if they are predicted in the SU(5) GUT. Therefore, it was needed to search for other theories if one wants to describe all SM interactions by one simple group, with avoiding the problem arise from the SU(5) GUT. All the GUTs with gauge groups larger than SU(5) can solve this problem, predicting at least one extra gauge boson (Z'). It was seen by H. Fritzsch and P. Minkowski in 1975 that the next gauge group larger than SU(5) is SO(10). SO(10) predicts the existence of one extra neutral gauge boson Z'c. GUTs with larger gauge groups than SO(10) predict the existence of more than one extra neutral gauge boson and many “exotic” fermions, which must be heavy to make the theory consistent with present experiments. The heavy bosons can decay to di-leptons in the final state as follows Z’ --> l− l+ (l = e, μ). The existence or not of this kind of models was investigated using the data taking by CMS experiment for 7 (see) and 8 (see) TeV centre of mass energy.

The analysis is based on the study of High Energy Electron-Positron Pairs (HEEP) [1-2] or high energy Muon pairs, which can lead to the discovery of new physics, emanating particularly from new gauge groups from Grand Unified Theories (GUT), or extra spatial dimensions (which could show up through modifications to the Standard Model Drell-Yan pair production) and through heavy resonance production. The main background processes to Z′ and G′ signals are t tbar production, tW production, WW pair production and SM Z --> tt --> ll, with the topology of two electrons or muons in the final state, which are estimated from data driven method (e μ method). The second background topology includes processes for which at least one jet is misidentified as an electron. The relevant processes are QCD dijet, W + jets and photon + jets production. In order to discriminate our signal from backgrounds a special selection for electrons [3-4] or muons are used with highest possible efficiency for the signal events, and acceptable rejection power for the backgrounds [5-6].

The spin determination of this new heavy boson is important to know the nature and then the model which predicts this particle. The main quantity which determined directly the particle spin is angular distribution. The angular distributions, based on Collins Soper frame, have been studied in the framework of high energy electron pairs (HEEP). Several signal MC samples of new heavy bosons (Mee = 2 TeV/c2) originated from different models (Randall Sundrum and ADD models for spin 2 Graviton, grand unified theories as spin1 Z′y and the Contact Interaction model), in addition to MC productions of high mass Drell-Yan (above 2 TeV/c2) have been used for this study. The study done at high mass for Drell-Yan background and different signal samples has shown that the angular distributions based on cos(qCS) is very useful variable to discriminator between Drell-Yan background and spin 2 particle (RS KK or ADD KK excitation) and spin 1 particle as Z′y with high mass. Finally, the discrimination power of the cos(qCS) variable between different signals and the main background (Drell-Yan events) was quantified using like-lihood ratio, in case a signal of 10 or 20 events is observed. In all cases and for all the models a 1s expected separation is achieved. It was shown that the discrimination can be sensitively improved by using the rapidity of the pair as a second variable in the likelihood ratio, which allows us to reach a separation close to 2s with 20 events for some models [7]. Although this study was preformed at 8 TeV, where no signal was seen, it gives insight of the sensitivity that could be reached.

The foreseen increase of LHC center of mass energy will help in the possible observation of a new high mass signal, which could show up only in couple of months after the LHC resume running in 2015. For this reason the study will be repeated with the foreseen MC production suitable for 13 TeV centre of mass energy to match the condition of data taking in 2015.

[1] The definition of High Energy Electron Positron (HEEP) ID: here

[2] HEEP Selection in CMSSW: here

[3] HEEP ID: HEEP_ID_AN2012_258_v3.pdf

[4] Cut on dxy and photon conversion rejection: Dxy_AN2012_391_v3.pdf

[5] HEEP Tag&Probe, Fake Rate, Invariant Mass Plot: here

[6] Search for high mass resonances using 2012 full data: AN2012_415_v10.pdf:

[7] Study of angular distribution of high mass di-electrons pairs in the 2012 data and for different models of physics: AN2013_361_v1.pdf

W' (Wprime) to mu + nu

Excited muon (mu*)

  • Decay channels
    • mu + mu* to 2 mu + Z to 4 mu
    • mu + mu* to 2 mu + gamma

Instructions for GEM simualtion

CMSSW Release

To align better with other systems upgrades and to facilitate sharing, it is better to use some of the official upgrade releases. The latest upgrade release currently is CMSSW_6_0_1_PostLS1v2_patch2.

cmsrel CMSSW_6_0_1_PostLS1v2_patch2
cd CMSSW_6_0_1_PostLS1v2_patch2/src/
cmsenv

Geometry

The Geometry/GEMGeometry package currently has four CMS geometry configuration with GEMs:

  • cmsExtendedGeometryPostLS2plusGEMXML_cfi.py
  • cmsExtendedGeometryPostLS1plusGEMXML_cfi.py
  • cmsExtendedGeometryPostLS1plusGEMr08v01XML_cfi.py
  • cmsExtendedGeometryPostLS1plusGEMr10v01XML_cfi.py

We will be mainly using the last 3 configuration. They enable a GEM system (added to the current PostLS1 detector geometry) with 6, 8 and 10 eta partitions respectively.

GEN-SIM recipe

The GEN-SIM step consist of GEN and SIM:

  • GEN: generation of physics processes
  • SIM: simulation of generated particles passing through the CMS detector. This is done with the GEANT4 package that is interfaced to CMSSW. GEANT produces SimHits. These are directed energy loss "hits" that the particle leaves while interacting with matter. Particles tend to leave trails of SimHits in their dedicated detectors. Each SimHit knows ID of detector it was produced in, position, direction (with respect to local detector's coordinate system), time of flight when it was produced after the beams' interaction, and energy loss in this hit.

Needed Packages

The tagset below is the latest code on the top of a base release to do GEN-SIM with GEMs.

cvs co -r V01-03-04-91   DataFormats/MuonDetId
cvs co -r V01-09-07      Geometry/CMSCommonData
cvs co -r V01-05-03      Geometry/ForwardCommonData
cvs co -r V01-05-01      Geometry/HcalCommonData
cvs co -r V01-08-05      Geometry/MuonCommonData
cvs co -r V01-00-01      Geometry/MuonNumbering
cvs co -r V01-03-01      Geometry/MuonSimData
cvs co -r V02-08-09      SimG4CMS/Calo
cvs co -r V01-01-08      SimG4CMS/Muon
cvs co -r V01-04-07      SimG4CMS/ShowerLibraryProducer
cvs co -r V05-16-05      SimG4Core/Application
cvs co -r V00-09-01      Geometry/CommonDetUnit
cvs co -r V00-02-03      Geometry/GEMGeometry
cvs co -r V00-01-06      Geometry/GEMGeometryBuilder
cvs co -r V02-04-00      Geometry/Records
cvs co -r V00-00-02      DataFormats/GEMDigi
cvs co -r V00-02-17      SimMuon/GEMDigitizer
cvs co -r  V00-11-00  L1Trigger/CSCTriggerPrimitives
cvs co -r V00-03-21 -d RPCGEM/GEMValidation UserCode/RPCGEM/GEMValidation
scram b -j 8

Generating GEN-SIM configurations

GEN

For this you can make use of the many pre-configured process generator fragments in Configuration/Generator/python. You can also add Configuration/Generator to your CMSSW release and check the python directory, e.g.

addpkg Configuration/Generator
ls -l $CMSSW_RELEASE_BASE/src/Configuration/Generator/python/*py

GEN-SIM

Use the cmsDriver with the appropriate geometry (someGeometryXML_cfi.py) to build a runnable configuration for cmsRun.

cmsDriver.py YourGEN_cfi \
  -s GEN,SIM \
  --conditions POSTLS161_V12::All \
  --geometry Geometry/GEMGeometry/someGeometryXML_cfi \
  --datatier GEN-SIM \
  --eventcontent FEVTDEBUG \
  -n nEvents   --no_exec   --fileout out_file_name.root

Example: You want to simulate 1000 event of W to l nu (GEN). You want the SimHits produced with GEANT4 (SIM) with the 6 partition geometry.

Choose the file Configuration/Generator/python/WToLNu_TuneZ2star_8TeV_pythia6_tauola_cff.py from the configuation files in the Configuration/Generator/python/ directory.

cmsDriver.py Configuration/Generator/python/WToLNu_TuneZ2star_8TeV_pythia6_tauola_cff.py \
  -s GEN,SIM \
  --conditions POSTLS161_V12::All \
  --geometry Geometry/GEMGeometry/cmsExtendedGeometryPostLS1plusGEMXML_cfi \
  --datatier GEN-SIM \
  --eventcontent FEVTDEBUG \
  -n 1000   --no_exec   --fileout WToLNu_TuneZ2star_8TeV_pythia6_tauola.root

The resulting configuration can be run with either cmsRun or CRAB.

cmsRun WToLNu_TuneZ2star_8TeV_pythia6_tauola_cff_py_GEN_SIM.py

Tutorial session

  • CMSDAS school 2013 : here

Manpower

  • Nicola De Filippis
  • Ahmd Ali Abdelalim
  • Sherif Elgammal
  • Reham Aly
  • Asmaa Fawzy
  • Walaa Mohammed
  • Waleed Ahmed Esmail
  • Shereen Aly
  • Mustafa Eshra

Useful links

-- AhmedAbdelalim - 29-Mar-2013 -- AhmedAbdelalim - 18-Apr-2013

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf AN2012_415_v10.pdf r1 manage 2376.2 K 2013-05-23 - 15:57 SherifElgammal Search for high mass resonances using 2012 full data
PDFpdf AN2013_361_v1.pdf r1 manage 1123.6 K 2013-10-27 - 12:59 SherifElgammal Angular distribution for Z'--->e e
PDFpdf Dxy_AN2012_391_v3.pdf r1 manage 407.3 K 2013-05-23 - 15:58 SherifElgammal Cut on dxy and photon conversion rejection
PDFpdf HEEP_ID_AN2012_258_v3.pdf r1 manage 2562.8 K 2013-05-23 - 15:57 SherifElgammal HEEP ID
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Topic revision: r13 - 2013-12-15 - SherifElgammal
 
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