Dielectron Channel at CMS Cairo University November, 26 2006 Waled Emam Centre for Theoretical Physics at the British Univ. in Egypt.

Presentation on theme: "Dielectron Channel at CMS Cairo University November, 26 2006 Waled Emam Centre for Theoretical Physics at the British Univ. in Egypt."— Presentation transcript:

Dielectron Channel at CMS Cairo University November, 26 2006 Waled Emam Centre for Theoretical Physics at the British Univ. in Egypt

Outline Physics motivation  Randall-Sundrum Gravitons  Heavy Z’ Bosons Monte Carlo simulation

Extra Dimensions Scenarios  Several models include extra dimensions have been introduced to solve hierarchy problem between M EW ~1TeV and M pl ~10 16 TeV  Arkani-Hamed, Dvipoulos and Dvali (ADD)  introduce large spatial extra dimensions  observed 3D space is a 3D-brane embedded in a higher dimensional space  extra spatial dimensions (the bulk) are orthogonal to 3D-brane  Standard Model particles are stick to the 3D brane  Graviton can travel in all dimensions  Size of large extra dimension:  M D = Fundamental Plank scale in 4+n dimensional space ~ TeV  Kaluza-Klein gauge bosons  fermions are localized on 3d brane  gauge bosons propagate in additional small extra dimension compactified on a circle of radius R c ~TeV -1 ~10 -17 cm  masses of these gauge boson modes are  M c compactification scale, M c =1/R c

Extra Dimensions Scenarios (Cont.)  The Randall-Sundrum(RS) model  introduce one warped extra dimension  5D space-time with 2 branes of 4D: Metric: e -2kr|φ| η υμ dx υ dx μ + r c 2 dφ 2 Curvature: k (~M pl ) Compactification radius: r c New coordinate: φ (-π ≤ φ ≤π) Traditional 4D coordinates: x ν  Gravity scale : Λ π =M Pl e -krπ kr c ≈11-12 => Λ π ~1 TeV => no hierarchy  Only the graviton can propagate in 5D  On the 4D branes, Kaluza-Klein excitations of the graviton can be observed.

Z’ Gauge Bosons  Extra neutral heavy gauge bosons are predicted in models beyond Standard Model  4 models studied:  Z SSM Sequential Standard Model  Z psi, Z eta, Z exi arising in E6 & SO(10) GUT group  They all differ by couplings to the SM fermions  The interaction of the Z’ to SM fermions is  Two mass eigenstates  Z’’ is heavy and decouple from Z & Z’  Z’ light and couple to Z

Serach for ED & Z’ at CMS  single photon+missing E T  Search for ADD direct graviton emission  Topology Single high p t photon in the central η region High missing pt back-to-back to the photon in the azimuthal plane with a similar p t distribution  Backgrounds  single lepton+missing E T  Search for W’  Topology Single high p t muon Muon isolation: no additional track within a cone of certain size  Backgrounds  dilepton, dipthoton, dijet  Search for Z’ (leptons, jets)  RS model (leptons, photons, jets)  TeV-1 model (electrons)

Dielectron Channel at CMS  Look for heavy resonances of order few TeV decaying into an electron pair  Observation of a resonance peak in the dielecton mass spectrum over background  Such heavy resonance can be interpreted as:  Randall-Sundrum graviton or  heavy Z’ bosons  Once a heavy resonance is discovered, its observables can be used to characterize the theoretical framework:  angular distributions measurement  forward-backward asymmetries

 Signal and Background:  Production of excited Gravitons according to the Randall-Sundrum (RS) model through qq and gg initial states  Two parameters control the RS model:  M 0 The mass of first Kaluza-Klein excitation  C=K/M pl The coupling constant  Universal decay modes: e + e -, mu + mu -, tau + tau - and gamma+gamma  Background:  Drell-Yan Z/gamma->l + l -  Fake electron: Dijet, gamma-jet, e-jet. But negligible  Monte Carlo Simulation  Pythia is used to produce the signal and background processes  CMSSW framework  Model parameters:  Mass (TeV): 0.75, 1.00, 1.25, 1.50, 1.75, 2.00, 2.50, 3.00, 3.50, 4.00  Coupling: 0.01, 0.02, 0.05, 0.1 Randall Sundrum Gravitons

 Monte Carlo Simulation (Cont.)  Pythia settings:  maxEvents= 5x10 3 !# of events  PMAS(347,1)= 750. !mass of G  MSEL=0 !full user control  MSUB(391) = 1 !ff -> G  MSUB(392) = 1 !gg -> G  MDCY(347,1) = 1 !allow G decay  CKIN(13) = -2.5 !eta cut |eta|<2.5  PARP(50) = 0.054 !C model coupling constant  MDME(4166,1)= 1 !e+ e-  Results:  Still in progress  Cross-section (fb) & Mass (TeV C\M1.001.502.002.503.003.504.00 0.015.920.690.130.030.0090.0030.001 0.02242.790.530.130.0370.0120.004 0.0514817.63.360.820.2380.0760.025 0.105966913.33.320.9540.3050.102

 Signal and Background:  Production of Z’ boson according to the E6 models through qq initial state  Two parameters control the Z’ production:  M The mass of the Z’  The coupling constants to the SM quarks and leptons  Universal decay modes: e + e -, mu + mu -, tau + tau -  Background: Drell-Yan Z/gamma->l + l -  Monte Carlo Simulation  Pythia is used to produce the signal and background processes  CMSSW framework  Model Parameters:  Mass (TeV): 1.00, 3.00, 5.00  Couplings: Heavy Z’ Bosons Z SSM ZψZψ ZηZη ZχZχ CVCV -0.080-0.783-0.479 CACA 0.505-0.7830.159

 Monte Carlo Simulation (Cont.)  Pythia settings:  maxEvents= 5x10 3 !# of events  PMAS(32,1)= 1000. !mass of G  MSEL=0 !full user control  MSUB(141) = 1 !ff -> gamma/Z/Z’  MSTP(44) = 3 !select the Z’ process, the Z or DY  CKIN(1) = 400 !mass cutoff'  CKIN(13) = -2.5 !eta cut |eta|<2.5  PARU(125) = -0.08 !C V coupling  PARU(126) = -1 !C A coupling  MDME(297,1)= 1 !e+ e-  Results:  Still in progress  Cross-section (fb) & Mass (TeV) & Drell-Yan complete interference MassZ SSM ZψZψ ZηZη ZχZχ 1.00487279561249 3.002.521.682.871.42 5.000.0450.0340.0510.027

To Do List  Fast simulation:  PYTHIA – Detector - Data  Event selection:  E HCAL /E ECAL < 10%.  Isolation cut:  Track associated with E ECAL is required for neutral rejection  Comparison with analysis from dimuon and diphoton channels

Download ppt "Dielectron Channel at CMS Cairo University November, 26 2006 Waled Emam Centre for Theoretical Physics at the British Univ. in Egypt."

Similar presentations